CN109422313B - Method for treating catalyst production wastewater - Google Patents
Method for treating catalyst production wastewater Download PDFInfo
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- CN109422313B CN109422313B CN201710750767.XA CN201710750767A CN109422313B CN 109422313 B CN109422313 B CN 109422313B CN 201710750767 A CN201710750767 A CN 201710750767A CN 109422313 B CN109422313 B CN 109422313B
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- 239000002351 wastewater Substances 0.000 title claims abstract description 196
- 238000000034 method Methods 0.000 title claims abstract description 123
- 239000003054 catalyst Substances 0.000 title claims abstract description 78
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 74
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims abstract description 318
- 238000001704 evaporation Methods 0.000 claims abstract description 250
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- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims abstract description 200
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- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 4
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- 239000003921 oil Substances 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- 238000007670 refining Methods 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
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- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 2
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- 235000011130 ammonium sulphate Nutrition 0.000 description 2
- RHZUVFJBSILHOK-UHFFFAOYSA-N anthracen-1-ylmethanolate Chemical compound C1=CC=C2C=C3C(C[O-])=CC=CC3=CC2=C1 RHZUVFJBSILHOK-UHFFFAOYSA-N 0.000 description 2
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- HFCSXCKLARAMIQ-UHFFFAOYSA-L disodium;sulfate;hydrate Chemical compound O.[Na+].[Na+].[O-]S([O-])(=O)=O HFCSXCKLARAMIQ-UHFFFAOYSA-L 0.000 description 1
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Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C1/00—Ammonia; Compounds thereof
- C01C1/02—Preparation, purification or separation of ammonia
- C01C1/022—Preparation of aqueous ammonia solutions, i.e. ammonia water
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D3/00—Halides of sodium, potassium or alkali metals in general
- C01D3/04—Chlorides
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/34—Nature of the water, waste water, sewage or sludge to be treated from industrial activities not provided for in groups C02F2103/12 - C02F2103/32
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2201/00—Apparatus for treatment of water, waste water or sewage
- C02F2201/002—Construction details of the apparatus
- C02F2201/007—Modular design
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Inorganic Chemistry (AREA)
- Materials Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Analytical Chemistry (AREA)
- Heat Treatment Of Water, Waste Water Or Sewage (AREA)
Abstract
The invention relates to the field of sewage treatment, and discloses a method for treating catalyst production wastewater, wherein the catalyst production wastewater contains NH 4 + 、SO 4 2‑ 、Cl ‑ And Na + The method comprises the steps of 1) carrying out first evaporation on wastewater to be treated to obtain first concentrated solution containing ammonia vapor and sodium sulfate crystals, wherein the wastewater to be treated contains the catalyst production wastewater; 2) Carrying out first solid-liquid separation on the first concentrated solution, and cooling and crystallizing the obtained liquid phase to obtain a crystallization liquid containing sodium sulfate crystals; 3) Carrying out second solid-liquid separation on the crystallization liquid, and carrying out second evaporation on a liquid phase obtained by the second solid-liquid separation to obtain second ammonia-containing steam and a second concentrated solution containing sodium chloride crystals; 4) Cooling the second concentrated solution to obtain a treatment solution containing sodium chloride crystals; 5) And carrying out third solid-liquid separation on the treatment liquid. The method can respectively recover the ammonium, the sodium sulfate and the sodium chloride in the wastewater, and furthest recycle resources in the wastewater.
Description
Technical Field
The invention relates to the field of sewage treatment, in particular to a method for treating catalyst production wastewater, and especially relates to a catalyst containing NH 4 + 、SO 4 2- 、Cl - And Na + The method for treating wastewater from catalyst production.
Background
In the production process of the oil refining catalyst, a large amount of inorganic acid-base salts such as sodium hydroxide, hydrochloric acid, sulfuric acid, ammonium salts, sulfates, hydrochlorides and the like are needed, and a large amount of mixed sewage containing ammonium, sodium sulfate, sodium chloride and aluminosilicate is generated. For such sewage, the common practice in the prior art is that the pH value is adjusted to be within the range of 6-9, most of suspended matters are removed, then the biochemical method, the blow-off method or the steam stripping method is adopted to remove ammonium ions, then the salt-containing sewage is subjected to pH value adjustment, most of suspended matters are removed, hardness, silicon and part of organic matters are removed, most of organic matters are removed through ozone biological activated carbon adsorption oxidation or other advanced oxidation methods, then the salt-containing sewage enters an ion exchange device for further hardness removal, enters an enrichment device (such as reverse osmosis or electrodialysis) for concentration, and then MVR evaporative crystallization or multiple-effect evaporative crystallization is adopted to obtain mixed miscellaneous salt of sodium sulfate and sodium chloride containing a small amount of ammonium salt; or is; firstly, adjusting the pH value to be within the range of 6.5-7.5, removing most suspended matters, then removing hardness, silicon and part of organic matters, removing most of the organic matters through ozone biological activated carbon adsorption oxidation or other advanced oxidation methods, then entering an ion exchange device for further removing hardness, entering a thickening device (such as reverse osmosis and/or electrodialysis) for concentration, and then adopting MVR (mechanical vapor recompression) evaporative crystallization or multi-effect evaporative crystallization to obtain the mixed miscellaneous salt of sodium sulfate and sodium chloride containing ammonium salt. However, these ammonium-containing mixed salts are currently difficult to treat or expensive to treat, and the process of removing ammonium ions at the early stage additionally increases the cost of wastewater treatment.
In addition, the biochemical deamination can only treat wastewater with low ammonium content, and can not directly carry out biochemical treatment due to insufficient COD content in the catalyst sewage, and organic matters such as glucose or starch and the like are additionally added in the biochemical treatment process, so that the ammoniacal nitrogen can be treated by the biochemical method. The most important problems are that the total nitrogen of the wastewater after the biochemical deamination treatment is not up to the standard (the contents of nitrate ions and nitrite ions exceed the standard), advanced treatment is needed, in addition, the salt content in the wastewater is not reduced (20-30 g/L), the wastewater cannot be directly discharged, and further desalination treatment is needed.
In order to remove ammoniacal nitrogen from wastewater by gas stripping deamination, a large amount of alkali is needed to adjust the pH value, the alkali consumption is high, the alkali in the wastewater after deamination cannot be recovered, the pH value of the treated wastewater is high, the treatment cost is high, the COD content in the catalyst wastewater after gas stripping does not change greatly, the salt content in the wastewater is not reduced (20-30 g/L), the wastewater cannot be directly discharged, further desalting treatment is needed, the wastewater treatment operation cost is high, a large amount of alkali remains in the treated wastewater, the pH value is high, waste is large, and the treatment cost is up to 50 yuan/ton.
Disclosure of Invention
The invention aims to overcome the defect of NH content in the prior art 4 + 、SO 4 2- 、Cl - And Na + The wastewater treatment cost is high, and only mixed salt crystals can be obtained, and the NH-containing catalyst with low cost and environmental protection is provided 4 + 、SO 4 2- 、Cl - And Na + The method for treating the wastewater generated in the catalyst production can respectively recover ammonium, sodium sulfate and sodium chloride in the wastewater, and furthest recycle resources in the wastewater.
In order to achieve the above objects, an aspect of the present invention provides a method for treating catalyst production wastewater containing NH 4 + 、SO 4 2- 、Cl - And Na + The method comprises the following steps of,
1) Performing first evaporation on wastewater to be treated to obtain first concentrated solution containing ammonia vapor and sodium sulfate crystals, wherein the wastewater to be treated contains the catalyst production wastewater;
2) Carrying out first solid-liquid separation on the first concentrated solution containing the sodium sulfate crystals, and cooling and crystallizing a liquid phase obtained by the first solid-liquid separation to obtain a crystallization solution containing the sodium sulfate crystals;
3) Carrying out second solid-liquid separation on the crystallization liquid containing the sodium sulfate crystals, and carrying out second evaporation on a liquid phase obtained by the second solid-liquid separation to obtain second ammonia-containing steam and a second concentrated solution containing the sodium chloride crystals;
4) Cooling the second concentrated solution containing the sodium chloride crystals to obtain a treatment solution containing the sodium chloride crystals;
5) Carrying out third solid-liquid separation on the treatment liquid;
before the wastewater to be treated is subjected to first evaporation, adjusting the pH value of the wastewater to be treated to be more than 9; relative to 1mol of SO contained in the wastewater to be treated 4 2- Cl contained in the wastewater to be treated - Is 14mol or less; the first evaporation does not crystallize sodium chloride out.
By the technical scheme, the method aims at the content of NH 4 + 、SO 4 2- 、Cl - And Na + The wastewater is subjected to first evaporation to obtain concentrated ammonia water after the pH value of the wastewater to be treated is adjusted to a specific range in advance, sodium sulfate crystals are obtained by cooling crystallization separation, then a second concentrated solution containing sodium chloride crystals and sodium sulfate crystals and dilute ammonia water are obtained by second evaporation, then the sodium sulfate crystals in the second concentrated solution are dissolved by cooling treatment, and sodium chloride is further crystallized and separated out to obtain sodium chloride crystals. The method can respectively obtain high-purity sodium sulfate and sodium chloride, avoids the difficulties in the processes of mixed salt treatment and recycling, simultaneously completes the process of separating ammonia and salt, simultaneously heats up the wastewater and cools the ammonia-containing steam by adopting a heat exchange mode without a condenser, reasonably utilizes the heat in the evaporation process, saves energy, reduces the wastewater treatment cost, recovers the ammonium in the wastewater in the form of ammonia water, recovers the sodium chloride and the sodium sulfate in the form of crystals respectively, does not generate waste residues and waste liquid in the whole process, and achieves the aim of changing waste into valuable.
The cooling crystallization process of the method can obtain the crystallization liquid only containing sodium sulfate crystals, and also can obtain the crystallization liquid containing sodium sulfate crystals and sodium chloride crystals. When the crystallization liquid only containing sodium sulfate crystals is obtained, hydrated sodium sulfate crystals can be directly obtained through separation and serve as products, or the product can be obtained after crystal water in the hydrated sodium sulfate crystals is removed, or the product can be returned to the first evaporation process for evaporation to obtain sodium sulfate without crystal water; when a crystal liquid containing sodium sulfate crystals and sodium chloride crystals is obtained, the obtained sodium sulfate crystals and sodium chloride crystals are returned to the first evaporation process together to be evaporated, thereby obtaining sodium sulfate crystals containing no crystal water. Through cooling crystallization, sodium chloride can be fully obtained through second evaporation, and the efficiency of wastewater treatment is improved.
Furthermore, the method obtains stronger ammonia water through first evaporation, is convenient for the utilization of the ammonia water, improves the ion concentration of the solution, improves the precipitation rate of cooling crystallization and improves the treatment efficiency; through the cooperation of the second evaporation and the cooling treatment, the second evaporation process can be carried out at a higher temperature, the solid content and the second evaporation efficiency of the second evaporation are improved, the amount of circulating liquid in the treatment system is reduced, and meanwhile, the energy-saving effect can be achieved.
Drawings
FIG. 1 is a schematic flow diagram of a method for treating wastewater from catalyst production according to an embodiment of the present invention.
Description of the reference numerals
1. The second MVR evaporation device 53 and the second mother liquor tank
2. Cooling crystallization device 54, third mother liquor tank
3. First MVR evaporation plant 55, low temperature treatment tank
31. First heat exchange device 61 and first pH value measuring device
32. Second heat exchange device 60 and second pH value measuring device
33. Third heat exchange device 70 and eleventh circulating pump
34. Fourth heat exchange device 71 and first circulating pump
35. Fifth heat exchange device 72 and second circulating pump
36. Sixth heat exchange device 73 and third circulation pump
38. Eighth heat exchanger 74 and fourth circulating pump
30. Tenth heat exchange device 75, fifth circulating pump
50. First mother liquid tank 76 and sixth circulating pump
51. First ammonia water storage tank 77 and seventh circulating pump
52. Second ammonia storage tank 78, eighth circulating pump
79. Ninth circulating pump 91 and second solid-liquid separation device
80. Tenth circulating pump 92, third solid-liquid separation device
84. Fourteenth circulating pump 93 and first solid-liquid separation device
81. Vacuum pump 101, first compressor
82. Circulating water tank 102 and second compressor
83. Tail gas absorption tower
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For numerical ranges, each range between its endpoints and individual point values, and each individual point value can be combined with each other to give one or more new numerical ranges, and such numerical ranges should be construed as specifically disclosed herein.
The present invention will be described below with reference to fig. 1, but the present invention is not limited to fig. 1.
The invention provides a method for treating wastewater generated in catalyst production, which contains NH 4 + 、SO 4 2- 、Cl - And Na + The method comprises the following steps of,
1) Performing first evaporation on wastewater to be treated to obtain first concentrated solution containing ammonia vapor and sodium sulfate crystals, wherein the wastewater to be treated contains the catalyst production wastewater;
2) Carrying out first solid-liquid separation on the first concentrated solution containing the sodium sulfate crystals, and cooling and crystallizing a liquid phase obtained by the first solid-liquid separation to obtain a crystallization solution containing the sodium sulfate crystals;
3) Carrying out second solid-liquid separation on the crystallization liquid containing the sodium sulfate crystals, and carrying out second evaporation on a liquid phase obtained by the second solid-liquid separation to obtain second ammonia-containing steam and a second concentrated solution containing the sodium chloride crystals;
4) Cooling the second concentrated solution containing the sodium chloride crystals to obtain a treatment solution containing the sodium chloride crystals;
5) Carrying out third solid-liquid separation on the treatment liquid;
before the wastewater to be treated is subjected to first evaporation, adjusting the pH value of the wastewater to be treated to be more than 9; relative to 1mol of SO contained in the wastewater to be treated 4 2- Cl contained in the wastewater to be treated - Is 14mol or less; the first evaporation does not crystallize out sodium chloride.
Preferably, the wastewater to be treated is the catalyst production wastewater; or the wastewater to be treated contains the catalyst production wastewater and a liquid phase obtained by the third solid-liquid separation.
More preferably, the wastewater to be treated is a mixed solution of the catalyst production wastewater and at least part of a liquid phase obtained by the third solid-liquid separation.
The method provided by the invention can be used for the treatment of the compounds containing NH 4 + 、SO 4 2- 、Cl - And Na + Except that it contains NH 4 + 、SO 4 2- 、Cl - And Na + In addition, the catalyst production wastewater is not particularly limited.
In the present invention, it is understood that the first ammonia-containing steam and the second ammonia-containing steam are so-called secondary steam in the art. The pressures are all pressures in gauge pressure.
In the present invention, the sequence of the first heat exchange, the adjustment of the pH value of the wastewater to be treated, and the preparation of the wastewater to be treated (in the case where the wastewater to be treated contains a liquid phase obtained by the solid-liquid separation of the catalyst production wastewater and the third solid-liquid separation, the preparation of the wastewater to be treated is required) is not particularly limited, and may be appropriately selected as needed, and the first evaporation of the wastewater to be treated is completed.
In the invention, the first evaporation aims at crystallizing and separating out sodium sulfate, concentrating the wastewater to be treated, simultaneously obtaining stronger ammonia water, improving the concentration of ions and improving the separation rate of cooling crystallization. The degree of the first evaporation can be selected according to the requirements and the components of the wastewater to be treated, and the purpose of only crystallizing and separating out sodium sulfate is achieved. For example, evaporation can be controlled to obtain only a small amount of ammonia-containing steam, so that ammonia water with higher concentration is obtained; also can be through the degree of control evaporation, make pending waste water concentrated, control ion concentration simultaneously, the subsequent cooling crystallization of being convenient for obtains pure sodium sulfate, also can fully go on through the control evaporation, makes pending waste water concentrated, improves the efficiency of cooling crystallization.
In the present invention, the first evaporation may be performed using an evaporation apparatus conventional in the art, such as an MVR evaporation apparatus, a single-effect evaporation apparatus, or a multi-effect evaporation apparatus. As the MVR evaporation means, for example, one or more selected from the group consisting of an MVR falling film evaporator, an MVR forced circulation evaporator, an MVR-FC continuous crystallization evaporator, and an MVR-OSLO continuous crystallization evaporator may be mentioned. Among them, preferred are an MVR forced circulation evaporator and an MVR-FC continuous crystallization evaporator, and more preferred is a falling film + forced circulation two-stage MVR evaporative crystallizer. The evaporator as the single-effect evaporator or the multiple-effect evaporator may be, for example, one or more selected from falling-film evaporators, rising-film evaporators, wiped-plate evaporators, central-circulation-tube-type multiple-effect evaporators, basket-suspended evaporators, external-heat evaporators, forced-circulation evaporators and lien evaporators. Among them, a forced circulation evaporator and an external heating evaporator are preferable. The respective evaporators of the multi-effect evaporation apparatus are composed of a heating chamber and an evaporation chamber, and may further include other evaporation auxiliary components as necessary, such as a demister for further separating liquid foam, a condenser for condensing all secondary steam, and a vacuum apparatus for pressure reduction operation. The number of evaporators included in the multi-effect evaporation apparatus is not particularly limited, and may be 2 or more, and more preferably 3 to 5. According to a preferred embodiment of the present invention, said first evaporation is carried out by means of a first MVR evaporation device 3.
According to the present invention, the conditions of the first evaporation are not particularly limited, and the purpose of concentrating the wastewater to be treated can be achieved. For example, the conditions of the first evaporation may include: the temperature is above 35 ℃ and the pressure is above-98 kPa. To improve the efficiency of evaporation, preferably, the first evaporation conditions include: the temperature is 75-130 ℃, and the pressure is-73 kPa-117 kPa; preferably, the conditions of the first evaporation include: the temperature is 85-130 ℃, and the pressure is-58 kPa-117 kPa; preferably, the conditions of the first evaporation include: the temperature is 95-110 ℃, and the pressure is-37 kPa-12 kPa; preferably, the conditions of the first evaporation include: the temperature is 95-105 ℃, and the pressure is-37 kPa to-7 kPa.
In the present invention, the operating pressure of the first evaporation is preferably the saturated vapor pressure of the evaporated feed liquid. In addition, the evaporation amount of the first evaporation may be appropriately selected depending on the capacity of the apparatus to treat and the amount of wastewater to be treated, and may be, for example, 0.1m 3 More than h (e.g. 0.1 m) 3 /h～500m 3 /h)。
From the viewpoint of improving the treatment efficiency of wastewater, relative to 1mol of SO contained in the wastewater to be treated 4 2- Cl contained in the wastewater to be treated - Is 14mol or less, preferably 13.8mol or less, preferably 13.75mol or less, more preferably 13.5mol or less, more preferably 13mol or less, still more preferably 12mol or less, still more preferably 11mol or less, still more preferably 10.5mol or lessPreferably 2mol or more, more preferably 2.5mol or more, further preferably 3mol or more, and may be, for example, 1.46 to 5.2mol. By reacting SO 4 2- And Cl - The molar ratio of (b) is controlled within the above range, so that sodium sulfate is precipitated in the first evaporation and sodium chloride is not precipitated.
By appropriately controlling the conditions of the first evaporation, 80 mass% or more, preferably 90 mass% or more, of the ammonia contained in the wastewater to be treated can be obtained by evaporation, and for example, 80 mass%, 83 mass%, 85 mass%, 86 mass%, 87 mass%, 88 mass%, 89 mass%, 90 mass%, 91 mass%, 93 mass%, 95 mass%, or 98 mass% can be obtained, and the first aqueous ammonia can be directly recycled in the production process of the catalyst, or can be recycled after being neutralized with an acid to obtain an ammonium salt, or can be used by blending with water and a corresponding ammonium salt or aqueous ammonia.
According to a preferred embodiment of the present invention, the first evaporation is performed such that the concentration of sodium chloride in the first concentrated solution is X or less, where X is the concentration of sodium chloride at which both sodium sulfate and sodium chloride in the first concentrated solution are saturated under the conditions of the first evaporation. Preferably, the first evaporation is such that the concentration of sodium chloride in the first concentrate is between 0.95X and 0.999X. When only sodium sulfate crystals are obtained by cooling crystallization, preferably, cl is contained in the liquid phase (i.e. the first mother liquor) obtained by the first solid-liquid separation - The concentration of (A) is less than 5.2 mol/L; more preferably, cl is contained in the liquid phase obtained by the first solid-liquid separation - The concentration of (B) is 5.0mol/L or less. By controlling the degree of the first evaporation, sodium sulfate is crystallized and precipitated as much as possible, and the chloride ion concentration in the liquid phase obtained by the first solid-liquid separation satisfies the condition that sodium chloride is not precipitated during cooling crystallization, the efficiency of wastewater treatment can be improved.
In the present invention, the degree of progress of the first evaporation is monitored by monitoring the concentration of the first concentrated solution, and specifically, the concentration of the liquid obtained by the first evaporation is controlled within the above range so that the first evaporation does not cause crystallization of sodium chloride. The concentration of the liquid resulting from the first evaporation is monitored by measuring the density, which may be carried out using a densitometer.
According to the invention, the pH of the wastewater to be treated is adjusted to a value greater than 9, preferably greater than 10.8, before the wastewater to be treated is subjected to the first evaporation. The upper limit of the adjustment of the pH of the wastewater to be treated is not limited, and may be, for example, 14 or less, preferably 13.5 or less, and more preferably 13 or less. By carrying out the first evaporation at the above pH, the evaporation of ammonia can be promoted, aqueous ammonia of higher concentration can be obtained, and high purity sodium sulfate and sodium chloride crystals can be conveniently obtained in the subsequent crystallization.
Specific examples of adjusting the pH of the wastewater to be treated before subjecting the wastewater to be treated to the first evaporation include: 9. 9.5, 9.6, 9.7, 9.8, 9.9, 10, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, 11, 11.1, 11.2, 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, 11.9, 12, 12.2, 12.4, 12.6, 12.8, 13, 13.5, or 14, etc.
In the present invention, the method of the pH adjustment is not particularly limited, and for example, the pH of the wastewater to be treated may be adjusted by adding an alkaline substance. The alkaline substance is not particularly limited, and may be used for the purpose of adjusting the pH. The alkaline substance is preferably NaOH in order not to introduce new impurities in the wastewater to be treated, increasing the purity of the crystals obtained. Further, the third mother liquor (i.e., the liquid phase obtained by the third solid-liquid separation) contains NaOH at a relatively high concentration, and it is also preferable to use the third mother liquor as the basic substance, and further supplement NaOH.
The manner of adding the basic substance may be any manner known in the art, but it is preferable to mix the basic substance with the wastewater to be treated in the form of an aqueous solution, and for example, an aqueous solution containing the basic substance may be introduced into a pipe through which the wastewater to be treated is introduced and mixed. The content of the alkaline substance in the aqueous solution is not particularly limited as long as the purpose of adjusting the pH can be achieved. However, in order to reduce the amount of water used and further reduce the cost, it is preferable to use a saturated aqueous solution of an alkaline substance or a second mother liquor. In order to monitor the pH value of the wastewater to be treated, the pH value of the wastewater to be treated may be measured after the above-mentioned pH value adjustment.
According to a preferred embodiment of the present invention, the first evaporation is performed in the first MVR evaporation device 3, pH adjustment is performed by introducing and mixing the aqueous solution containing the alkaline substance in the pipe that feeds the wastewater to be treated to the first MVR evaporation device 3 before feeding the wastewater to be treated to the first MVR evaporation device 3, and the adjusted pH is measured by the first pH measuring device 61 and the second pH measuring device 60 after the adjustment.
According to the present invention, in order to fully utilize the heat of the first ammonia-containing steam, it is preferable that before the wastewater to be treated is subjected to the first evaporation, the wastewater to be treated is subjected to the first heat exchange with the first ammonia-containing steam to obtain the first ammonia water, and at the same time, the temperature of the wastewater to be treated is raised to facilitate the evaporation.
According to a preferred embodiment of the present invention, the first heat exchange between the wastewater to be treated and the first ammonia-containing steam is performed by the first heat exchange device 31 and the eighth heat exchange device 38, specifically, the ammonia-containing steam is sequentially passed through the eighth heat exchange device 38 and the first heat exchange device 31, and simultaneously the wastewater to be treated is passed through the first heat exchange device 31 to exchange heat with the first ammonia-containing steam condensate, and then the wastewater to be treated is passed into the eighth heat exchange device 38 to exchange heat with the first ammonia-containing steam. Through the first heat exchange, the obtained first ammonia water is stored in the first ammonia water storage tank 51, and simultaneously, the temperature of the wastewater to be treated is raised to 82-137 ℃, preferably 102-117 ℃, so that the evaporation can be conveniently carried out.
According to the present invention, in order to fully utilize the heat of the first concentrated solution, it is preferable that before the wastewater to be treated is subjected to the first evaporation, the wastewater to be treated is subjected to the first heat exchange with the first concentrated solution, so that the temperature of the first concentrated solution is lowered to facilitate cooling crystallization, and the temperature of the wastewater to be treated is raised to facilitate evaporation.
According to a preferred embodiment of the present invention, the first heat exchange between the wastewater to be treated and the first concentrated solution is performed by the eleventh heat exchange device 30, and the wastewater to be treated is heat exchanged with the first concentrated solution by the eleventh heat exchange device 30.
The first heat exchange device 31, the eleventh heat exchange device 30 and the eighth heat exchange device 38 are not particularly limited, and various heat exchangers conventionally used in the art may be used to perform heat exchange. Specifically, a jacketed heat exchanger, a plate heat exchanger, a shell-and-tube heat exchanger, or the like may be mentioned, with the plate heat exchanger being preferred. The material of the heat exchanger can be specifically selected according to the needs, for example, in order to resist the corrosion of chloride ions, the heat exchanger of duplex stainless steel, titanium and titanium alloy, hastelloy can be selected as the material, and the heat exchanger containing plastic material can be selected when the temperature is lower.
In the present invention, in order to increase the solid content in the first MVR evaporation device 3 and reduce the ammonia content in the liquid, it is preferable that a part of the liquid evaporated by the first MVR evaporation device 3 (i.e. the liquid located inside the first MVR evaporation device, also referred to as the first circulation liquid) is heated and then returned to the first MVR evaporation device 3 for evaporation. The above-mentioned process of returning the first circulation liquid to the first MVR evaporation device 3 is preferably to return the first circulation liquid to the first MVR evaporation device 3 after mixing with the wastewater to be treated after the first pH adjustment and before the second pH adjustment, for example, the first circulation liquid may be returned to the wastewater delivery pipeline between the first heat exchange device 31 and the eighth heat exchange device 38 by the fifth circulation pump 75 to be mixed with the wastewater to be treated, and then after the second pH adjustment, heat exchange is performed by the eighth heat exchange device 38, and finally the wastewater is sent to the first MVR evaporation device 3. Here, the first reflux ratio means: the ratio of the amount of reflux to the total amount of liquid fed to the first MVR evaporator 3 minus the amount of reflux. The reflux ratio may be set appropriately according to the evaporation amount to ensure that the first MVR evaporation device 3 can evaporate the required amount of water and ammonia at a given evaporation temperature. For example, the first reflux ratio of the first evaporation may be 10 to 200, preferably 50 to 100.
According to the present invention, preferably, the method further comprises compressing the first ammonia-containing vapor before the first heat exchange. The compression of the first ammonia-containing vapor may be performed by a first compressor 101. Through right first ammonia vapor that contains compresses, for input energy among the MVR vaporization system, guarantee that waste water intensification-evaporation-cooling's process goes on in succession, need input start-up steam when MVR vaporization process starts, only need pass through first compressor 101 energy supply after reaching continuous running state, no longer need input other energy. The first compressor 101 may employ various compressors conventionally used in the art, such as a centrifugal fan, a turbine compressor, or a roots compressor. After compression by the first compressor 101, the temperature of the first ammonia-containing vapor is raised by 5 to 20 ℃.
In the invention, the first concentrated solution containing sodium sulfate crystals is subjected to first solid-liquid separation to obtain sodium sulfate crystals and a first mother liquor (namely, a liquid phase obtained by the first solid-liquid separation). The method of the first solid-liquid separation is not particularly limited, and may be selected from one or more of centrifugation, filtration, and sedimentation.
According to the present invention, the first solid-liquid separation of the first concentrated solution may be performed by using a first solid-liquid separation device (for example, a centrifuge, a belt filter, a plate filter, or the like). As shown in fig. 1, after the first solid-liquid separation, the first mother liquor obtained by the first solid-liquid separation device 93 is temporarily stored in the first mother liquor tank 50, and may be sent to the cooling crystallization device 2 by the eleventh circulation pump 70 to be cooled and crystallized. In addition, it is difficult to avoid that impurities such as chlorine ions, free ammonia, and hydroxide ions are adsorbed on the obtained sodium sulfate crystals, and in order to remove the adsorbed impurities, reduce the odor of solid salts, reduce corrosiveness, and improve the purity of the crystals, it is preferable that the sodium sulfate crystals are first washed with water, the catalyst production wastewater, or a sodium sulfate solution and dried.
The manner of the first solid-liquid separation and the first washing is not particularly limited, and may be carried out by using, for example, a combination of an elutriation apparatus and a solid-liquid separation apparatus which are conventional in the art, or may be carried out on a staged solid-liquid separation apparatus such as a belt filter. Preferably, the first wash comprises panning and/or rinsing. The above-mentioned elutriation and rinsing are not particularly limited and may be carried out by a method conventional in the art. The number of elutriation and rinsing is not particularly limited, and may be 1 or more, and is preferably 2 to 4 times in order to obtain sodium sulfate crystals of higher purity. In the elutriation process, the waste water produced by the catalyst is generally not recycled when used as an elutriation liquid, and the washing liquid recovered by the first washing can be recycled in a counter-current manner when used as the elutriation liquid. Before the elutriation, it is preferable to perform a preliminary solid-liquid separation by sedimentation to obtain a slurry containing sodium sulfate crystals (the liquid content may be 35% by mass or less, and this step is preferably performed in an apparatus known in the art such as a sedimentation tank or a sedimentation tank). In the elutriation, 1 to 20 parts by weight of a liquid is used for elutriation per 1 part by weight of a slurry containing sodium sulfate crystals. In addition, the rinsing is preferably carried out using an aqueous sodium sulfate solution, the concentration of which is preferably such that the sodium chloride and the sodium sulfate reach the concentration of sodium sulfate in the saturated aqueous solution at the same time at the temperature corresponding to the sodium sulfate crystals to be rinsed. In order to further enhance the elutriation effect and obtain sodium sulfate crystals with higher purity, the elutriation is preferably performed using a liquid obtained by rinsing, and preferably using water or a sodium sulfate solution. It is preferable for the liquid produced by the washing to be returned to before the first heat exchange before the first evaporation is completed.
According to a preferred embodiment of the present invention, after a first concentrated solution containing sodium sulfate crystals is subjected to a preliminary solid-liquid separation by settling, the catalyst production wastewater is subjected to a first elutriation in an elutriation tank, then a liquid obtained in a subsequent sodium sulfate crystal washing is subjected to a second elutriation in another elutriation tank, finally, the slurry subjected to the two elutriations is sent to a solid-liquid separation device for solid-liquid separation, crystals obtained by the solid-liquid separation are washed with an aqueous sodium sulfate solution, and the liquid obtained by the washing is returned to the second elutriation. Through the washing process, the purity of the obtained sodium sulfate crystal is improved, washing liquid is not excessively introduced, and the efficiency of wastewater treatment is improved.
In the present invention, the cooling crystallization may be performed to obtain a crystal liquid containing only sodium sulfate crystals, or may be performed to obtain a crystal liquid containing sodium sulfate crystals and sodium chloride crystals. In the case where it is intended to separate sodium sulfate from wastewater to obtain sodium sulfate crystals by precipitating sodium sulfate, it is preferable that the cooling crystallization is performed so that only sodium sulfate crystals are contained in the obtained crystal liquid. In this case, the obtained sodium sulfate crystals (i.e., the solid phase obtained by the second solid-liquid separation) are hydrated sodium sulfate crystals (e.g., sodium sulfate decahydrate crystals) and may be used as they are, or sodium sulfate crystals may be obtained by removing the crystal water through a step such as heating, or sodium sulfate crystals may be obtained by returning to the first evaporation step and evaporating the crystals to obtain sodium sulfate crystals containing no crystal water. In addition, when the purpose is to obtain sodium sulfate containing no crystal water, the cooling crystallization may be performed so that the obtained crystal liquid contains sodium sulfate crystals (sodium sulfate hydrate crystals) and sodium chloride crystals. In this case, it is preferable that the sodium sulfate crystals obtained by the cooling crystallization and the sodium chloride crystals (i.e., the solid phase obtained by the second solid-liquid separation) are returned to the first evaporation step together and evaporated to obtain sodium sulfate crystals containing no crystal water. As a method for returning the crystals obtained by the cooling crystallization to the first evaporation process, it is preferable to return to a waste water line before the pH adjustment and the first heat exchange before the first evaporation, for example, before the first pH adjustment device 61.
According to a preferred embodiment of the present invention, in order to obtain high-purity sodium sulfate crystals, it is preferable that the cooling crystallization is performed so that sodium chloride crystals are not precipitated, that is, a crystal liquid containing only sodium sulfate crystals is obtained, and sodium sulfate can be separated from wastewater favorably. The cooling crystallization only precipitates sodium sulfate and does not exclude sodium chloride entrained by the sodium sulfate crystals or adsorbed on the surface. In the present invention, the content of sodium sulfate in the obtained sodium sulfate crystals is preferably 92% by mass or more, more preferably 96% by mass or more, and further preferably 98% by mass or more), it is understood that the amount of the obtained sodium sulfate crystals is based on a dry basis. When the content of sodium sulfate in the obtained sodium sulfate crystal is within the above range, it is considered that only sodium sulfate is precipitated. That is, when the total content of impurities such as sodium chloride in the obtained sodium sulfate crystals is 8 mass% or less, it is considered that only sodium sulfate is precipitated.
In order to ensure that sodium sulfate crystals are obtained by cooling crystallization, SO in the first mother liquor is preferably used 4 2- The concentration of (A) is preferably 0.01mol/L or more, more preferably 0.07mol/L or more, still more preferably 0.1mol/L or more, and yet more preferably 0.01mol/L or moreIs 0.2mol/L or more, and particularly preferably 0.3mol/L or more. According to the invention, in order to increase the purity of the sodium sulfate crystals obtained by cooling crystallization, the Cl in the first mother liquor - The concentration of (A) is preferably 5.2mol/L or less, more preferably 5mol/L or less, further preferably 4.5mol/L or less, and further preferably 4mol/L or less, so that sodium chloride does not precipitate in the cooled crystals.
By adding SO in the first mother liquor 4 2- 、Cl - The concentration is controlled in the range, so that the first evaporation can be fully carried out, and simultaneously, sodium sulfate in the cooling crystal can be separated out without separating out sodium chloride, thereby achieving the aim of efficiently separating sodium sulfate. In the present invention, if SO is present in said first mother liquor 4 2- 、Cl - The concentration of (b) is not within the above range, and concentration adjustment may be carried out before cooling crystallization is carried out, and the concentration adjustment is preferably carried out using the catalyst production wastewater, washing of sodium sulfate crystals, and/or a third mother liquor, and the like, and specifically may be mixed with the first mother liquor in the first mother liquor tank 50.
SO in the first mother liquor 4 2- Specific examples of the content include: 0.01mol/L, 0.03mol/L, 0.05mol/L, 0.08mol/L, 0.1mol/L, 0.2mol/L, 0.3mol/L, 0.4mol/L, 0.5mol/L, 0.6mol/L, or 0.7mol/L, and the like.
Additionally, cl is present in the first mother liquor - Specific examples of the content include: 2.0mol/L, 2.2mol/L, 2.4mol/L, 2.6mol/L, 2.8mol/L, 3mol/L, 3.2mol/L, 3.4mol/L, 3.6mol/L, 3.8mol/L, 4mol/L, 4.5mol/L or 5mol/L, etc.
According to another preferred embodiment of the present invention, when the solid phase obtained by the second solid-liquid separation is not used as a product for wastewater treatment, the sodium chloride can be crystallized by cooling crystallization, that is, the sodium sulfate crystals and the sodium chloride crystals are obtained simultaneously by cooling crystallization, and at this time, the obtained sodium sulfate crystals and the sodium chloride crystals are returned to the first evaporation process together to be evaporated so as to obtain sodium sulfate crystals containing no crystal water. Through the cooperation of the first evaporation and the cooling crystallization, the first evaporation can be controlled more easily, and the efficiency of wastewater treatment is improved simultaneously.
The pH value of the wastewater to be treated is more than 9 by adjusting the pH value before the first evaporation, wherein the NH is 4 + Most of the ammonia molecules are evaporated during the first evaporation, so that ammonium sulfate and/or ammonium chloride are not separated out in the cooling crystallization process, and the sodium sulfate separation rate can be improved due to the increase of the concentration of sodium chloride.
In the present invention, the cooling crystallization conditions may be appropriately selected as needed, and the effect of crystallizing out the sodium sulfate may be achieved. The cooling crystallization conditions may include: the temperature is-21.7-17.5 ℃, preferably-20-5 ℃, more preferably-10-5 ℃, further-10-0 ℃, and particularly preferably-4-0 ℃; the time (in terms of the time of residence in the cooling crystallization apparatus 2) is 5min or more, preferably 60min to 180min, more preferably 90min to 150min, and further preferably 120min to 150min. By controlling the cooling crystallization conditions within the above range, sodium sulfate can be sufficiently precipitated, and sodium chloride can be precipitated or not precipitated as necessary.
Specific examples of the temperature for cooling crystallization include: -21 ℃, -20 ℃, -19 ℃, -18 ℃, -17 ℃, -16 ℃, -15 ℃, -14 ℃, -13 ℃, -12 ℃, -11 ℃, -10 ℃, -9 ℃, -8 ℃, -7 ℃, -6 ℃, -5 ℃, -4 ℃, -3 ℃, -2 ℃, -1 ℃ or 0 ℃.
Specific examples of the time for cooling crystallization include: 5min, 6min, 7min, 8min, 10min, 15min, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 52min, 54min, 56min, 58min, 60min, 65min, 70min, 75min, 80min, 85min, 90min, 95min, 100min, 105min, 110min, 115min, 120min, 130min, 140min, 150min, or 160min.
According to the present invention, the cooling crystallization is carried out in a continuous or batch manner, and the temperature of the first mother liquor is lowered to precipitate sodium sulfate crystals, and the continuous cooling crystallization is preferably carried out. The cooling crystallization of the sodium sulfate may be carried out by various cooling crystallization apparatuses conventionally used in the art, for example, by using a continuous cooling crystallizer with an external cooling heat exchanger, or by using a crystallization tank having a cooling means, such as the cooling crystallization device 2. The cooling part can lead the first mother liquor in the cooling crystallization device to be cooled to the condition required by cooling crystallization by introducing a cooling medium. The cooling crystallization device is preferably provided with a blending part, such as a stirrer and the like, and the first mother liquor is blended to achieve the effect of uniform cooling, so that sodium sulfate in the first mother liquor can be fully precipitated, and the size of crystal grains can be increased. The cooling crystallization device is preferably provided with a circulating pump, so as to avoid generating a large amount of fine crystal nuclei and prevent crystal grains in the circulating crystal slurry from colliding with the impeller at a high speed to generate a large amount of secondary crystal nuclei, and the circulating pump is preferably a centrifugal pump with low rotating speed, and more preferably a guide pump impeller with large flow and low rotating speed or an axial pump with large flow, low lift and low rotating speed.
By carrying out the cooling crystallization under the above conditions, sodium sulfate can be sufficiently precipitated in the cooling crystallization, and the purpose of separating and purifying sodium sulfate can be achieved.
In the present invention, in order to control the crystal grain size distribution in the cooling crystallization device 2 and reduce the content of fine crystal grains, it is preferable that a part of the liquid crystallized by the cooling crystallization device 2 (that is, the liquid located inside the cooling crystallization device 2, hereinafter also referred to as cooling circulation liquid) is mixed with the first mother liquid and then returned to the cooling crystallization device 2 to be cooled and crystallized again. The above-mentioned process of returning the cooling circulation liquid to the cooling crystallization device 2 for crystallization may be, for example, by returning the cooling circulation liquid to the sixth heat exchange device 36 by the second circulation pump 72, mixing with the first mother liquid, and then entering the cooling crystallization device 2 again for cooling crystallization. The return amount of the cooling circulation liquid can be defined by a cooling circulation ratio which is: the ratio of the circulating amount to the total amount of the liquid fed to the cooling crystallization device 2 minus the circulating amount. The circulation ratio may be appropriately set according to the supersaturation degree of sodium sulfate in the cooling crystallization apparatus 2 to ensure the particle size of sodium sulfate crystals. In order to control the particle size distribution of crystals obtained by cooling crystallization and to reduce the content of fine crystal grains, it is preferable to control the supersaturation degree to less than 1.5g/L, more preferably to less than 1g/L.
In the invention, the sodium sulfate crystal and the second mother liquor (i.e. the liquid phase obtained by the second solid-liquid separation) are obtained after the second solid-liquid separation is carried out on the crystallization liquid containing the sodium sulfate crystal. The method of the second solid-liquid separation is not particularly limited, and may be selected from one or more of centrifugation, filtration, and sedimentation, for example.
According to the present invention, the second solid-liquid separation may be performed by using a second solid-liquid separation device 91 (for example, a centrifuge, a belt filter, a plate filter, or the like). After the second solid-liquid separation, the second mother liquor obtained by the second solid-liquid separation device 91 is temporarily stored in the second mother liquor tank 53, and can be sent to the second MVR evaporation device 1 through the sixth circulation pump 76 for second evaporation. In addition, it is difficult to avoid adsorbing impurities such as chloride ions, free ammonia, and hydroxide ions on the obtained sodium sulfate crystals, and when the sodium sulfate obtained by cooling crystallization is used as a product, the sodium sulfate crystals are preferably subjected to a second washing with water or a sodium sulfate solution, and may be dried when anhydrous sodium sulfate is required, in order to remove the adsorbed impurities, reduce the odor of solid salts, reduce corrosiveness, and improve the purity of the crystals. The second washing method is preferably rinsing, and rinsing is preferably performed after solid-liquid separation.
The form of the second solid-liquid separation and the second washing is not particularly limited, and may be carried out, for example, by using a solid-liquid separation apparatus which is conventional in the art, or may be carried out in a staged solid-liquid separation apparatus. The washing is not particularly limited and may be carried out by a method conventional in the art. The number of washing is not particularly limited, and may be 1 or more, and is preferably 2 to 4 times in order to obtain sodium sulfate crystals of higher purity. The second washing is preferably carried out using an aqueous sodium sulphate solution, the concentration of which is preferably such that the sodium chloride and the sodium sulphate reach simultaneously the concentration of sodium sulphate in a saturated aqueous solution at the temperature corresponding to the sodium sulphate crystals to be washed. As for the liquid resulting from the washing, it is preferred that the water or aqueous sodium sulfate solution washing liquid is returned to the cooling crystallization device 2, for example, by an eighth circulation pump 78 to the cooling crystallization device 2.
According to a preferred embodiment of the present invention, after cooling the crystal liquid containing sodium sulfate obtained by crystallization, solid-liquid separation is performed by a solid-liquid separation apparatus, and the crystals obtained by solid-liquid separation are rinsed with an aqueous sodium sulfate solution (the concentration of the aqueous sodium sulfate solution is the concentration of sodium sulfate in an aqueous solution in which sodium chloride and sodium sulfate are saturated at the temperature corresponding to the sodium sulfate crystals to be rinsed), and the rinsed liquid is returned to the cooling crystallization apparatus 2. By the above washing process, the purity of the obtained sodium sulfate crystals can be improved.
According to the present invention, in order to make full use of the refrigeration capacity of the second mother liquor, it is preferable that the second mother liquor is subjected to second heat exchange with the first mother liquor before the first mother liquor is cooled and crystallized.
According to a preferred embodiment of the present invention, the second heat exchange is performed by a second heat exchange device 32, and specifically, the second mother liquor and the first mother liquor are respectively passed through the second heat exchange device 32 and heat exchanged, so that the temperature of the first mother liquor is lowered to facilitate the cooling crystallization, and the temperature of the second mother liquor is raised to facilitate the second evaporation. After the second heat exchange is carried out by the second heat exchange device 32, the temperature of the first mother liquor is-20.7-16.5 ℃, preferably-5-10 ℃, and is close to the temperature of cooling crystallization.
According to the invention, in order to facilitate the cooling crystallization, the first mother liquor and the refrigerating fluid are subjected to second heat exchange. According to a preferred embodiment of the present invention, the second heat exchange between the first mother liquid and the freezing liquid is performed by the sixth heat exchange device 36, specifically, the freezing liquid and the first mother liquid are respectively passed through the sixth heat exchange device 36, and heat exchange is performed between the freezing liquid and the first mother liquid, so that the temperature of the first mother liquid is reduced to facilitate cooling crystallization. The refrigerating fluid can be the refrigerating fluid which is used for cooling conventionally in the field, as long as the temperature of the first mother liquor can meet the requirement of cooling crystallization.
The second heat exchanger 32 and the sixth heat exchanger 36 are not particularly limited, and various heat exchangers conventionally used in the art may be used to perform heat exchange. Specifically, a jacketed heat exchanger, a plate heat exchanger, a shell-and-tube heat exchanger, or the like may be mentioned, with the plate heat exchanger being preferred. The material of the heat exchanger can be specifically selected according to the needs, for example, in order to resist the corrosion of chloride ions, the heat exchanger of duplex stainless steel, titanium and titanium alloy, hastelloy can be selected as the material, and the heat exchanger containing plastic material can be selected when the temperature is lower. The second heat exchange device 32 is preferably a heat exchanger made of plastic.
In the present invention, the second evaporation is intended to separate out sodium chloride and/or sodium sulfate and further evaporate ammonia, thereby separating ammonia and salts in the wastewater. According to the invention, by controlling the conditions of the second evaporation, sodium chloride is first precipitated, possibly sodium sulphate, with a progressive reduction in the solvent, obtaining a second concentrated solution containing sodium chloride crystals. In order to reduce the amount of circulating water in the treatment system and to increase the efficiency of the second evaporation and thus of the wastewater treatment, said second evaporation is preferably carried out to such an extent that sodium chloride and sodium sulfate are precipitated simultaneously, that is to say that the second evaporation preferably results in a second concentrated solution comprising sodium sulfate crystals and sodium chloride crystals.
In the present invention, the second evaporation may be performed using an evaporation apparatus conventional in the art, such as an MVR evaporation apparatus, a single-effect evaporation apparatus, or a multi-effect evaporation apparatus. The details of the device in the first evaporation are not repeated herein. In the present invention, the second evaporation is preferably performed by the second MVR evaporation device 1. Among them, preferred are an MVR forced circulation evaporator and an MVR-FC continuous crystallization evaporator, and more preferred is a falling film + forced circulation two-stage MVR evaporative crystallizer.
In the present invention, the evaporation conditions of the second evaporation are not particularly limited, and may be appropriately selected as necessary to achieve the purpose of precipitating crystals. The conditions of the second evaporation may include: the conditions of the second evaporation include: the temperature is above 35 ℃ and the pressure is above-98 kPa; preferably, the conditions of the second evaporation include: the temperature is 45-175 ℃, and the pressure is-95 kPa-653 kPa; preferably, the conditions of the second evaporation include: the temperature is 60-175 ℃, and the pressure is-87 kPa-653 kPa; preferably, the conditions of the second evaporation include: the temperature is 75-175 ℃, and the pressure is-73 kPa-653 kPa; preferably, the conditions of the second evaporation include: the temperature is 80-130 ℃, and the pressure is-66 kPa-117 kPa; preferably, the conditions of the second evaporation include: the temperature is 95-110 ℃, and the pressure is-37 kPa-12 kPa; preferably, the conditions of the second evaporation include: the temperature is 105-107 ℃ and the pressure is-8 kPa-0 kPa.
In the present invention, the operating pressure of the second evaporation is preferably the saturated vapor pressure of the evaporated feed liquid. Further, the evaporation amount of the second evaporation may be appropriately selected depending on the capacity of the apparatus to treat and the amount of the waste water to be treated, and may be, for example, 0.1m 3 More than h (e.g. 0.1 m) 3 /h～500m 3 /h)。
In order to obtain sodium chloride crystals better in the second evaporation process, it is preferable to use SO contained in 1mol of the liquid phase obtained by the second solid-liquid separation 4 2- Cl contained in the liquid phase obtained by the second solid-liquid separation - Is 7.15mol or more, more preferably 10mol or more, further preferably 20mol or more, further preferably 44mol or more, further preferably 50mol or more, further preferably 74mol or more, more preferably 230mol or less, such as 44 to 50mol, for example, 9.5mol, 10.5mol, 11mol, 11.5mol, 12mol, 12.5mol, 13mol, 13.5mol, 14mol, 14.5mol, 15mol, 15.5mol, 16mol, 16.5mol, 17mol, 17.5mol, 18mol, 18.5mol, 19mol, 19.5mol, 20mol, 21mol, 22mol, 23mol, 25mol, 27mol, 29mol, 31mol, 35mol, 40mol, 45mol, 50mol, 60mol, 65mol, and the like. By reacting SO 4 2- And Cl - The molar ratio of the sodium sulfate to the sodium chloride is controlled in the range, pure sodium chloride crystals can be obtained through temperature reduction treatment after evaporation, and separation of the sodium sulfate and the sodium chloride is realized.
According to the present invention, from the viewpoint of improving the efficiency of wastewater treatment, the higher the degree of progress of the second evaporation, the better; however, if the second evaporation exceeds a certain level, the treatment solution containing only sodium chloride crystals cannot be obtained by the temperature reduction treatment, and in this case, the crystals can be dissolved by adding water to the treatment solution, but the efficiency of wastewater treatment is impaired. Therefore, the second evaporation is preferably performed to such an extent that sodium chloride crystals and sodium sulfate crystals are precipitated simultaneously, and the temperature reduction treatment can dissolve the sodium sulfate crystals in the second concentrated solution containing sodium chloride crystals; that is, it is preferable that the second concentrated solution containing sodium chloride crystals obtained in step 3) is a concentrated solution containing sodium chloride crystals and sodium sulfate crystals, and the temperature reduction treatment dissolves the sodium sulfate crystals in the concentrated solution containing sodium chloride crystals and sodium sulfate crystals. In order to dissolve the sodium sulfate crystals in the concentrated solution containing the sodium chloride crystals and the sodium sulfate crystals in the temperature reduction treatment, for example, the evaporation degree of the second evaporation may be controlled so that the concentration of sodium sulfate in the treatment solution is Y or less (where Y is the concentration of sodium sulfate when both sodium sulfate and sodium chloride in the treatment solution are saturated under the temperature reduction treatment condition). In the subsequent temperature lowering treatment step, the concentration of sodium sulfate in the treatment solution is preferably 0.9Y to 0.99Y, more preferably 0.95Y to 0.98Y, from the viewpoint of precipitating sodium chloride as much as possible and completely dissolving sodium sulfate. By controlling the degree of the second evaporation within the above range, it is ensured that sodium chloride is precipitated as much as possible during the second evaporation, and sodium sulfate is completely dissolved during the temperature reduction treatment, and finally pure sodium chloride crystals are separated. By crystallizing sodium chloride in the second evaporation as much as possible, the wastewater treatment efficiency can be improved, and energy can be saved.
In the present invention, the degree of progress of the second evaporation is performed by monitoring the evaporation amount of the second evaporation, that is, the amount of the liquid, and specifically, the concentration factor is controlled by controlling the evaporation amount of the second evaporation, that is, the amount of the ammonia water, so that the sodium sulfate crystals precipitated in the second concentrated solution obtained by the second evaporation can be dissolved during the temperature reduction treatment. The degree of the second evaporative concentration is monitored by measuring the second evaporation amount, and specifically, the flow measurement can be performed by using a mass flow meter, the amount of the secondary steam can be measured, and the amount of the condensate can also be measured.
In the present invention, in order to increase the liquid salt concentration in the second MVR evaporation device 1 and reduce the ammonia content in the liquid, it is preferred that part of the liquid evaporated by the second MVR evaporation device 1 (i.e. the liquid located inside the second MVR evaporation device, hereinafter also referred to as second circulation liquid) is returned to the second MVR evaporation device 1 for evaporation, preferably heated and then returned to the second MVR evaporation device 1 for evaporation. The above-described process of returning the second circulation liquid to the second MVR evaporating device 1 may be returned to the third heat exchange process by, for example, the seventh circulation pump 77. The second reflux ratio of the second evaporation is: the ratio of the amount of reflux to the total amount of liquid fed to the second MVR evaporator 1 minus the amount of reflux. The second reflux ratio can be set appropriately according to the evaporation amount to ensure that the second MVR evaporation device can evaporate the required amount of water and ammonia at the given second evaporation temperature. The second reflux ratio of the second evaporation may be, for example, 10 to 200, preferably 60 to 110.
According to the present invention, preferably, the method further comprises compressing the second ammonia-containing vapor before the third heat exchange. The compression of the second ammonia-containing vapor may be performed by a second compressor 102. The second ammonia-containing steam is compressed, energy is input into the MVR evaporation system, the continuous process of waste water heating, evaporation and cooling is guaranteed, starting steam needs to be input when the MVR evaporation process is started, energy is supplied only through the second compressor 102 after the continuous running state is achieved, and other energy does not need to be input. The second compressor 102 may employ various second compressors conventionally used in the art, such as a centrifugal fan, a turbine compressor, or a roots compressor, etc. After compression in the second compressor 102, the temperature of the second ammonia-containing vapor is raised by 5 to 20 ℃.
According to the present invention, in order to fully utilize the heat of the second ammonia-containing vapor obtained by the second evaporation, it is preferable to subject the second mother liquor to a third heat exchange with the second ammonia-containing vapor before the second mother liquor is sent to the second MVR evaporation device 1.
According to a preferred embodiment of the present invention, the third heat exchange of the second mother liquor with the second ammonia-containing vapor is performed by a third heat exchange means 33 and a fourth heat exchange means 34, respectively. Specifically, the second mother liquor sequentially passes through the third heat exchange device 33 and the fourth heat exchange device 34, and the second ammonia-containing steam sequentially passes through the fourth heat exchange device 34 and the third heat exchange device 33, so that the temperature of the second mother liquor is raised, the second evaporation is facilitated, and the second ammonia-containing steam is condensed to obtain ammonia water. After heat exchange is carried out by the third heat exchange device 33, the temperature of the second mother liquor is raised to 34-109 ℃, preferably 44-109 ℃; after heat exchange by the fourth heat exchange device 34, the temperature of the second mother liquor is raised to 42 ℃ to 117 ℃, preferably 52 ℃ to 117 ℃.
According to the present invention, in order to make full use of the heat in the second concentrated solution containing sodium chloride crystals obtained by the second evaporation, it is preferable to subject the second concentrated solution containing sodium chloride crystals to a third heat exchange with the second mother liquor before the second evaporation.
According to a preferred embodiment of the present invention, the third heat exchange of the second concentrated solution containing sodium chloride crystals with the second mother liquor is performed by means of a fifth heat exchange means 35. Specifically, the second mother liquor and the second concentrated solution containing sodium chloride crystals pass through the fifth heat exchange device 35, so that the temperature of the second mother liquor is raised for second evaporation, and the second concentrated solution containing sodium chloride crystals is cooled for cooling treatment. After the heat exchange is carried out by the fifth heat exchange device 35, the temperature of the second mother liquor is raised to 34-109 ℃, preferably 44-109 DEG C
The third heat exchanger 33, the fourth heat exchanger 34 and the fifth heat exchanger 35 are not particularly limited, and various heat exchangers conventionally used in the art may be used to achieve the purpose of heat exchange. Specifically, a jacketed heat exchanger, a plate heat exchanger, a shell-and-tube heat exchanger, or the like may be mentioned, with the plate heat exchanger being preferred. The material of the heat exchanger can be specifically selected according to the needs, for example, in order to resist the corrosion of chloride ions, the heat exchanger of duplex stainless steel, titanium and titanium alloy, hastelloy can be selected as the material, and the heat exchanger containing plastic material can be selected when the temperature is lower. Preferably, a duplex stainless steel plate heat exchanger is used.
In the present invention, the temperature reduction treatment is performed to dissolve sodium sulfate crystals that may be contained in the second concentrated solution containing sodium chloride crystals, thereby further precipitating sodium chloride. The temperature reduction treatment for dissolving the sodium sulfate crystals in the second concentrated solution containing sodium chloride crystals means that the degree of the second evaporation needs to be properly controlled in order to obtain pure sodium chloride crystals, that is, the sodium sulfate in the mixed system does not exceed the solubility under the corresponding temperature reduction treatment conditions, and sodium sulfate entrainment or surface adsorption of sodium chloride crystals is not excluded. Since the water content of the crystals after the solid-liquid separation is different, the sodium sulfate content in the obtained sodium chloride crystals is usually 8 mass% or less (preferably 4 mass% or less), and in the present invention, it is considered that the sodium sulfate crystals are dissolved when the sodium sulfate content in the obtained sodium chloride crystals is 8 mass% or less.
The conditions for performing the temperature reduction treatment are not particularly limited, and the sodium sulfate crystals in the second concentrated solution containing sodium chloride crystals may be completely dissolved in the temperature reduction treatment process, for example, the conditions for performing the temperature reduction treatment may include: the temperature is 13 to 100 ℃, preferably 15 to 45 ℃, more preferably 15 to 35 ℃, and still more preferably 17.9 to 35 ℃. In order to ensure the effect of the temperature reduction treatment, preferably, the conditions of the temperature reduction treatment include: the time is more than 5min, preferably 5min to 120min, and more preferably 30min to 90min; more preferably 50 to 60min.
Specific examples of the temperature lowering treatment include: 13 deg.C, 14 deg.C, 15 deg.C, 15.5 deg.C, 16 deg.C, 16.5 deg.C, 17 deg.C, 17.5 deg.C, 17.9 deg.C, 18 deg.C, 18.5 deg.C, 19 deg.C, 19.5 deg.C, 20 deg.C, 21 deg.C, 23 deg.C, 25 deg.C, 27 deg.C, 30 deg.C, 31.5 deg.C, 32 deg.C, 33 deg.C, 34 deg.C, 40 deg.C, 45 deg.C, 50 deg.C, 55 deg.C, etc.
Specific examples of the time for the temperature lowering treatment include: 5min, 6min, 7min, 8min, 10min, 15min, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 52min, 54min, 56min, 58min, 60min, 70min, 100min, 120min.
According to the present invention, the temperature reduction treatment is performed in the low-temperature treatment tank 55, and the treatment solution containing sodium chloride crystals is obtained after the temperature reduction treatment of the second concentrated solution containing sodium chloride crystals in the low-temperature treatment tank 55. The low-temperature treatment tank 55 is not particularly limited, and may be, for example, a thickener, a crystallization tank with agitation, a crystallization tank with external circulation, or the like, and among them, a crystallization tank with agitation is preferable. The low-temperature treatment tank 55 is preferably provided with a kneading means for bringing the second concentrated solution into a kneaded state in the temperature reduction treatment, and for example, a conventionally used mechanical stirring, electromagnetic stirring and/or an external circulation device may be used, and it is preferable that the solid-liquid distribution in the second concentrated solution is brought into a uniform state. All parts of the second concentrated solution are kept at uniform temperature and uniform concentration through uniform mixing, so that the problem that the dissolution of sodium sulfate crystals cannot be fully carried out is avoided, and the efficiency of cooling treatment is improved. The low-temperature treatment tank 55 is preferably provided with a cooling means for cooling the low-temperature treatment tank 55 to a temperature required for the temperature reduction treatment by introducing a cooling medium, for example.
According to the present invention, the third solid-liquid separation may be performed by a third solid-liquid separation device (e.g., a centrifuge, a belt filter, a plate and frame filter, etc.) 92. After the third solid-liquid separation, the third mother liquor obtained by the third solid-liquid separation device 92 (i.e., the liquid phase obtained by the third solid-liquid separation) is returned to the first MVR device 3 for the first evaporation again, and specifically, the third mother liquor can be returned to the place before the second pH adjustment by the ninth circulation pump 79. In addition, it is difficult to avoid that the obtained sodium chloride crystals adsorb certain impurities such as sulfate ions, free ammonia, hydroxide ions, etc., and in order to remove the adsorbed impurities, reduce the odor of solid salts, reduce corrosiveness, and improve the purity of the crystals, the sodium chloride crystals are preferably subjected to third washing with water, the catalyst production wastewater, or a sodium chloride solution and dried. In order to avoid dissolution of the sodium chloride crystals during washing, preferably the sodium chloride crystals are washed with an aqueous solution of sodium chloride. More preferably, the concentration of the sodium chloride aqueous solution is preferably the concentration of sodium chloride in the aqueous solution at which sodium chloride and sodium sulfate reach saturation simultaneously at the temperature corresponding to the sodium chloride crystals to be washed.
The form of the third solid-liquid separation and the third washing is not particularly limited, and may be carried out, for example, by using a combination of an elutriation apparatus and a solid-liquid separation apparatus which are conventional in the art, or may be carried out on a staged solid-liquid separation apparatus such as a belt filter. The third washing mode comprises elutriation and/or rinsing. The above-mentioned elutriation and rinsing are not particularly limited and may be carried out by a method conventional in the art. The number of elutriation and rinsing is not particularly limited, and may be 1 or more, and is preferably 2 to 4 times in order to obtain sodium chloride crystals of higher purity. In the elutriation process, the washing liquid recovered by the third washing can be used in a countercurrent manner when used as the elutriation liquid. Before the elutriation, it is preferable to perform preliminary solid-liquid separation by sedimentation to obtain a slurry containing sodium chloride crystals (the liquid content may be 35% by mass or less). In the elutriation process, 1 to 20 parts by weight of a liquid is used for elutriation with respect to 1 part by weight of a slurry containing sodium chloride crystals. The rinsing is preferably carried out using an aqueous sodium chloride solution, the concentration of which is preferably the concentration of sodium chloride in an aqueous solution in which sodium chloride and sodium sulfate are simultaneously saturated at the temperature corresponding to the sodium chloride crystals to be washed. In order to further enhance the elutriation effect and obtain sodium chloride crystals with higher purity, it is preferable to perform elutriation using the eluted solution. For the liquid resulting from the washing, preferably, the water or aqueous sodium chloride washing and elutriation liquid is returned to the second MVR evaporation device 1, for example, to the second MVR evaporation device 1 by the tenth circulation pump 80.
According to a preferred embodiment of the present invention, the treatment liquid containing sodium chloride crystals obtained by the temperature reduction treatment is subjected to preliminary solid-liquid separation by settling, then elutriated in another elutriation tank using a liquid obtained when sodium chloride crystals are subsequently washed, the elutriated treatment liquid containing sodium chloride crystals is sent to a solid-liquid separation apparatus for solid-liquid separation, the crystals obtained by the solid-liquid separation are washed with an aqueous sodium chloride solution (the concentration of the aqueous sodium chloride solution is the concentration of sodium chloride in an aqueous solution in which sodium chloride and sodium sulfate are simultaneously saturated at a temperature corresponding to the sodium chloride crystals to be washed), and the washed liquid is returned to the elutriation as an elutriation liquid. Through the washing process combining elutriation and leaching, the purity of the obtained sodium chloride crystal is improved, washing liquid is not excessively introduced, and the efficiency of wastewater treatment is improved.
According to a preferred embodiment of the invention, the tail gas generated by cooling crystallization is discharged after ammonia removal; discharging the tail gas which is remained by the third heat exchange condensation after ammonia removal; and discharging the tail gas which is remained by the condensation of the first heat exchange after ammonia removal. The tail gas generated by the cooling crystallization is the tail gas discharged by the cooling crystallization device 2, and the third heat exchange condenses the rest tail gas, namely the non-condensable gas discharged by the fourth heat exchange device 34; the first heat exchange ring condenses the remaining tail gas, i.e., the tail gas discharged from the eighth heat exchange device 38. The ammonia in the tail gas is removed, so that the pollutant content in the discharged tail gas can be further reduced, and the tail gas can be directly discharged.
As the method of removing ammonia, absorption may be performed by the off-gas absorption tower 83. The off-gas absorption column 83 is not particularly limited, and may be any of various absorption columns conventionally used in the art, such as a plate-type absorption column, a packed absorption column, a falling film absorption column, or an empty column. Circulating water is arranged in the tail gas absorption tower 83, the circulating water circulates in the tail gas absorption tower 83 under the action of the fourth circulating pump 74, water can be supplemented into the tail gas absorption tower 83 from the circulating water tank 82 through the third circulating pump 73, fresh water can be supplemented into the circulating water tank 82, and meanwhile the temperature of working water of the vacuum pump 81 and the ammonia content can be reduced. The flow of the tail gas and the circulating water in the tail gas absorption tower 83 may be countercurrent or cocurrent, and is preferably countercurrent. The circulating water can be supplemented by additional fresh water. In order to ensure the sufficient absorption of the tail gas, dilute sulfuric acid may be further added to the tail gas absorption tower 83 to absorb a small amount of ammonia and the like in the tail gas. The circulating water can be used as ammonia water or ammonium sulfate solution for production or direct sale after absorbing tail gas. The off gas may be introduced into the off gas absorption tower 83 by a vacuum pump 81.
In the present invention, the catalyst production wastewater is not particularly limited as long as it contains NH 4 + 、SO 4 2- 、Cl - And Na + The wastewater is obtained. In addition, the method is particularly suitable for treating high-salt ammonium-containing wastewater. The waste water from catalyst production of the invention can be molecular sieve, alumina or oil refining catalystThe wastewater from the production process can also be wastewater obtained by removing impurities and concentrating the wastewater from the molecular sieve, alumina or oil refining catalyst production process as follows. It is preferable that the wastewater from the production of molecular sieves, alumina or refinery catalysts is subjected to the following impurity removal and concentration.
As NH in the catalyst production wastewater 4 + May be 8mg/L or more, preferably 300mg/L or more.
As Na in the wastewater from the catalyst production + May be 510mg/L or more, preferably 1g/L or more, more preferably 2g/L or more, further preferably 4g/L or more, further preferably 8g/L or more, further preferably 16g/L or more, further preferably 32g/L or more, further preferably 40g/L or more, further preferably 50g/L or more, further preferably 60g/L or more.
As SO in wastewater from the production of said catalyst 4 2- May be 1g/L or more, preferably 2g/L or more, more preferably 4g/L or more, further preferably 8g/L or more, further preferably 16g/L or more, further preferably 32g/L or more, further preferably 40g/L or more, further preferably 50g/L or more, further preferably 60g/L or more, further preferably 70g/L or more.
As Cl in the catalyst production wastewater - May be 970mg/L or more, more preferably 2g/L or more, further preferably 4g/L or more, further preferably 8g/L or more, further preferably 16g/L or more, further preferably 32g/L or more, further preferably 40g/L or more, further preferably 50g/L or more, further preferably 60g/L or more.
NH contained in the catalyst production wastewater 4 + 、SO 4 2- 、Cl - And Na + The upper limit of (3) is not particularly limited. SO in the wastewater from catalyst production from the viewpoint of easy wastewater treatment 4 2- 、Cl - And Na + The upper limit of (b) is 200g/L or less, preferably 150g/L or less, respectively; NH in catalyst production wastewater 4 + Is 50g/L or less, preferably 30g/L or less.
In the present invention, the inorganic salt ions contained in the catalyst production wastewater are other than NH 4 + 、SO 4 2- 、Cl - And Na + In addition, it may contain Mg 2+ 、Ca 2+ 、K + 、Fe 3+ Inorganic salt ions such as rare earth element ions, mg 2+ 、Ca 2+ 、K + 、Fe 3+ The content of each inorganic salt ion such as a rare earth element ion is preferably 100mg/L or less, more preferably 50mg/L or less, still more preferably 10mg/L or less, and particularly preferably no other inorganic salt ion is contained. By controlling the other inorganic salt ions within the above range, the purity of the sodium sulfate crystals and sodium chloride crystals finally obtained can be further improved. In order to reduce the content of other inorganic salt ions in the catalyst production wastewater, the following impurity removal is preferably performed.
The TDS of the catalyst production wastewater may be 1.6g/L or more, preferably 4g/L or more, more preferably 8g/L or more, further preferably 16g/L or more, further preferably 32g/L or more, further preferably 40g/L or more, further preferably 50g/L or more, further preferably 60g/L or more, further preferably 100g/L or more, further preferably 150g/L or more, further preferably 200g/L or more.
In the present invention, the pH of the catalyst production wastewater is preferably 4 to 8, for example 6 to 7.
In addition, since the COD of the wastewater may block a membrane during concentration, affect the purity and color of a salt during evaporative crystallization, etc., the COD of the wastewater from the catalyst production is preferably as small as possible (preferably 20mg/L or less, more preferably 10mg/L or less), and is preferably removed by oxidation during pretreatment, specifically, by biological method, advanced oxidation method, etc., and is preferably oxidized by an oxidizing agent such as Fenton's reagent when the COD content is very high.
In the invention, in order to reduce the concentration of impurity ions in the wastewater, ensure the continuous and stable treatment process and reduce the equipment operation and maintenance cost, the catalyst production wastewater is preferably subjected to impurity removal before being treated by the treatment method. Preferably, the impurity removal is selected from one or more of solid-liquid separation, chemical precipitation, adsorption, ion exchange and oxidation.
As the solid-liquid separation, filtration, centrifugation, sedimentation, or the like may be mentioned; the chemical precipitation may be pH adjustment, carbonate precipitation, magnesium salt precipitation, or the like; the adsorption can be physical adsorption and/or chemical adsorption, and the specific adsorbent can be selected from activated carbon, silica gel, alumina, molecular sieve, natural clay and the like; as the ion exchange, either one of a strongly acidic cation resin and a weakly acidic cation resin can be used; as the oxidation, various oxidizing agents conventionally used in the art, such as ozone, hydrogen peroxide, potassium permanganate, and in order to avoid introduction of new impurities, ozone, hydrogen peroxide, and the like are preferably used.
The specific impurity removal mode can be specifically selected according to the types of impurities contained in the catalyst production wastewater. For suspended matters, a solid-liquid separation method can be selected for removing impurities; for inorganic matters and organic matters, chemical precipitation, ion exchange and adsorption methods can be selected for removing impurities, such as weak acid cation exchange, activated carbon adsorption and the like; for organic matters, impurities can be removed by adopting an adsorption and/or oxidation mode, wherein an ozone biological activated carbon adsorption oxidation method is preferred. According to a preferred embodiment of the invention, the catalyst production wastewater is subjected to chemical precipitation, filtration, weak acid cation exchange method and ozone biological activated carbon adsorption oxidation method for impurity removal in sequence. By the impurity removal process, most suspended matters, hardness, silicon and organic matters can be removed, the scaling risk of the device is reduced, in addition, the evaporation process is carried out under the strong alkaline condition, the scaling risk of silicon dioxide of the evaporation device is also avoided, and the continuous and stable operation of the wastewater treatment process is ensured.
In the present invention, the wastewater having a low salt content may be concentrated to have a salt content within a range required for the catalyst production wastewater of the present invention before the treatment by the treatment method of the present invention (preferably after the above-mentioned impurity removal). Preferably, the concentration is selected from ED membrane concentration and/or reverse osmosis; more preferably, the concentration is performed by ED membrane concentration and reverse osmosis, and the order of performing the ED membrane concentration and the reverse osmosis is not particularly limited. The ED membrane concentration and reverse osmosis treatment apparatus and conditions may be performed in a manner conventional in the art, and may be specifically selected according to the condition of wastewater to be treated. Specifically, as the concentration of the ED membrane, a one-way electrodialysis system or a reversed electrodialysis system can be selected for carrying out; as the reverse osmosis, a roll membrane, a plate membrane, a disc tube membrane, a vibrating membrane or a combination thereof can be selected for carrying out. Through the concentration can improve the efficiency of waste water treatment, avoid the energy waste that a large amount of evaporations caused.
In a preferred embodiment of the invention, the catalyst production wastewater is wastewater generated by chemical precipitation, filtration, weak acid cation exchange and ozone biological activated carbon adsorption oxidation of wastewater generated in the molecular sieve production process, and is concentrated by an ED membrane and a reverse osmosis method.
The conditions for the above chemical precipitation are preferably: sodium carbonate is used as a treating agent, 1.2-1.4mol of sodium carbonate is added relative to 1mol of calcium ions in the wastewater, the pH value of the wastewater is adjusted to be more than 7, the reaction temperature is 20-35 ℃, and the reaction time is 0.5-4h.
The conditions for the filtration are preferably: the filtering unit adopts a double-layer filtering material multi-medium filter consisting of anthracite and quartz sand, the grain diameter of the anthracite is 0.7-1.7mm, the grain diameter of the quartz sand is 0.5-1.3mm, and the filtering speed is 10-30m/h. After the filter material is used, the regeneration method of 'gas back flushing-gas and water back flushing-water back flushing' is adopted to regenerate the filter material, and the regeneration period is 10-15h.
The conditions for the weak acid cation exchange method are preferably: the pH value range is 6.5-7.5; the temperature is less than or equal to 40 ℃, the height of the resin layer is 1.5-3.0m, the HCl concentration of the regeneration liquid is as follows: 4.5-5 mass%; the dosage of the regenerant (calculated by 100%) is 50-60kg/m 3 Wet resin; the flow rate of the regeneration liquid HCl is 4.5-5.5m/h, and the regeneration contact time is 35-45min; the forward washing flow rate is 18-22m/h, and the forward washing time is 2-30min; the running flow rate is 15-30m/h; as the acidic cation exchange resin, for example, there can be used a Gallery Senno chemical Co., ltd, SNT brand D113 acidic cation exchange resin.
The conditions of the above-mentioned ozone biological activated carbon adsorption oxidation method are preferably: the retention time of the ozone is 50-70min, and the empty bed filtration rate is 0.5-0.7m/h.
The conditions for the concentration of the ED membrane are preferably: the current is 145-155A, and the voltage is 45-65V. The ED membrane may be, for example, an ED membrane manufactured by astone corporation of japan.
The conditions for the reverse osmosis are preferably: the operation pressure is 5.4-5.6MPa, the water inlet temperature is 25-35 ℃, and the pH value is 6.5-7.5. The reverse osmosis membrane is, for example, a seawater desalination membrane TM810C manufactured by Dongli corporation of Lanxingdong.
According to the invention, when the wastewater treatment is started, the catalyst production wastewater can be used for directly starting operation, and if the ion content of the catalyst production wastewater meets the conditions of the invention, the first evaporation and cooling crystallization can be carried out firstly, and then the second evaporation and cooling treatment can be carried out according to the conditions of the invention; if the ion content of the catalyst production wastewater does not meet the conditions of the invention, second evaporation and temperature reduction treatment can be firstly carried out to obtain a second concentrated solution, solid-liquid separation is carried out to obtain sodium chloride crystals and a second mother solution, then the second mother solution is mixed with the catalyst production wastewater to adjust the ion content of the wastewater to be treated to be in the range required by the invention, and then first evaporation and cooling crystallization are carried out to obtain sodium sulfate crystals. Of course, the ion content of the wastewater to be treated can be adjusted by using sodium sulfate or sodium chloride in the initial stage as long as the wastewater to be treated satisfies the SO content in the wastewater to be treated in the present invention 4 2- 、Cl - The requirements are met.
The present invention will be described in detail below by way of examples.
In the following examples, the catalyst production wastewater is wastewater from a molecular sieve production process, which is subjected to chemical precipitation, filtration, weak acid cation exchange and ozone biological activated carbon adsorption oxidation in sequence to remove impurities, and is subjected to ED membrane concentration and reverse osmosis concentration in sequence.
Example 1
As shown in figure 1, the catalyst production wastewater (containing NaCl58g/L, na) 2 SO 4 66g/L、NH 4 Cl 26.3g/L、(NH 4 ) 2 SO 4 30.4g/L, pH of 6.8) at a feed rate of 5m 3 Feeding the wastewater into a pipeline of a treatment system at a speed of/h, introducing a sodium hydroxide aqueous solution with the concentration of 45.16 mass% into the pipeline to adjust the pH value for the first time, monitoring the adjusted pH value (the measured value is 8.0) by a first pH value measuring device 61 (a pH meter), feeding one part of the catalyst production wastewater into a first heat exchange device 31 through a first circulating pump 71 to exchange heat with a first ammonia-containing steam condensate, mixing the other part of the catalyst production wastewater with a third mother liquor returned by a ninth circulating pump 79, feeding the mixture into an eleventh heat exchange device 30 to exchange heat with the first mother liquor, and combining the two parts to obtain wastewater to be treated (wherein SO is used for treating wastewater) 4 2- With Cl - In a molar ratio of 1:2.42 In the second step), the wastewater to be treated is sent to the eighth heat exchange device 38 to exchange heat with the first ammonia-containing steam, so that the temperature of the wastewater to be treated is raised to 112 ℃, then a sodium hydroxide aqueous solution with the concentration of 45.16 mass% is introduced into the pipeline sent to the first MVR evaporation device 3 to carry out the second pH value adjustment, and the adjusted pH value is monitored by the second pH value measuring device 60 (pH meter) (the measured value is 10.8).
The first evaporation is carried out in a first MVR evaporation device 3 (a falling film + forced circulation two-stage MVR second evaporation crystallizer), the evaporation temperature is 105 ℃, the pressure is-7.01 kPa, and the evaporation capacity is 4.12m 3 And/h, obtaining a first concentrated solution containing ammonia steam and sodium sulfate crystals. After the first ammonia-containing steam is compressed by the first compressor 101 (the temperature is raised by 16 ℃), the first ammonia-containing steam exchanges heat with wastewater to be treated and wastewater from catalyst production in the eighth heat exchange device 38 and the first heat exchange device 31 in sequence to obtain first ammonia water, and the first ammonia water is stored in the first ammonia water storage tank 51. In addition, in order to increase the solid content in the first MVR evaporation device 3, part of the liquid evaporated in the first MVR evaporation device 3 is circulated as a first circulation liquid to the eighth heat exchange device 38 by the fifth circulation pump 75, and then enters the first MVR evaporation device 3 again for first evaporation (the first reflux ratio is 82). The degree of the first evaporation was monitored by a densitometer provided in the first MVR evaporator 3, and the concentration of sodium chloride in the first concentrated solution was controlled to 273.5g/L (4.675 mol/L).
Sulfur-containing vapor obtained by the first MVR evaporation device 3The first concentrated solution of sodium acid crystals is sent to a first solid-liquid separation device 93 (centrifugal machine) for first solid-liquid separation, and then 1.90m is obtained per hour 3 Contains NaCl 273.5g/L, na 2 SO 4 60.7g/L、NaOH 1.67g/L、NH 3 0.43g/L of the first mother liquor (Cl) - Has a concentration of 4.675mol/L, SO 4 2- Is 0.4275 mol/L), temporarily stored in a first mother liquor tank 50, the sodium sulfate solid obtained by solid-liquid separation (the sodium sulfate crystal filter cake 500.52kg containing 1.5 mass% of water is obtained per hour, wherein the content of sodium chloride is below 2.0 mass%) is leached by a sodium sulfate solution of 60g/L which is equal to the dry basis mass of the sodium sulfate crystal filter cake, after drying, the sodium sulfate 493.51kg (the purity is 99.5 mass%) is obtained per hour, and a washing liquid is circulated to a pipeline before entering an eighth heat exchange device 38 through a fourteenth circulating pump 84 to be mixed with the catalyst production wastewater, and then enters a first MVR evaporation device 3 again to carry out first evaporation.
The first mother liquor is sent into an eleventh heat exchange device 30 through an eleventh circulating pump 70 to exchange heat with the catalyst production wastewater, then sent into a second heat exchange device 32 (a heat exchanger made of plastic) to exchange heat with the first mother liquor so as to cool the first mother liquor to 16 ℃, then mixed with the circulating liquid of the cooling crystallization device 2 conveyed by a second circulating pump 72, further cooled through heat exchange with the refrigerating liquid through a sixth heat exchange device 36, and sent into the cooling crystallization device 2 (a continuous freezing crystallization tank) to be cooled and crystallized, so as to obtain the crystallization liquid containing sodium sulfate crystals. Wherein the cooling crystallization temperature is-2 deg.C, the time is 120min, and the circulation amount of the cooling crystallization is controlled to 84m 3 And h, controlling the supersaturation degree of the sodium sulfate during the freezing process to be 1.0g/L.
The sodium sulfate crystal-containing crystal liquid obtained in the cooling crystallization apparatus 2 was sent to a second solid-liquid separation apparatus 91 (centrifuge) to be subjected to solid-liquid separation, whereby 1.74m per hour was obtained 3 Containing NaCl 299g/L, na 2 SO 4 15.6g/L、NaOH 1.8g/L、NH 3 0.46g/L of second mother liquor is temporarily stored in a second mother liquor tank 53, 98 mass percent of sodium sulfate decahydrate crystal filter cake 200.59kg with 56 mass percent of water is obtained every hour, the catalyst production wastewater is dissolved, and then the dissolved catalyst production wastewater is sent into a first MVR evaporation device through a first circulating pump 713, carrying out first evaporation to prepare anhydrous sodium sulfate.
The second evaporation process is carried out in a second MVR evaporation plant 1 (falling film + forced circulation two-stage MVR second evaporation crystallizer). One part of the second mother liquor is sent to a third heat exchange device 33 (a duplex stainless steel plate type heat exchanger) to exchange heat with the compressed second ammonia-containing steam condensate, the other part of the second mother liquor is sent to a fifth heat exchange device 35 (a duplex stainless steel plate type heat exchanger) to exchange heat with a second concentrated solution containing sodium chloride crystals obtained by second evaporation, then the two parts of the second mother liquor are combined and sent to a fourth heat exchange device 34 (a duplex stainless steel plate type heat exchanger) to exchange heat with the second ammonia-containing steam, and second evaporation is carried out in a second MVR evaporation device 1 to obtain a second concentrated solution containing sodium chloride crystals and second ammonia-containing steam. The temperature of the second evaporation is 105 ℃, the pressure is-7.02 kPa, and the evaporation capacity is 1.57m 3 H is the ratio of the total weight of the catalyst to the total weight of the catalyst. After the second ammonia-containing steam is compressed by the second compressor 102 (the temperature is raised by 16 ℃), the second ammonia-containing steam exchanges heat with the second mother liquor in the fourth heat exchange device 34 and the third heat exchange device 33 in sequence to obtain second ammonia water, and the second ammonia water is stored in the second ammonia water storage tank 52. In addition, in order to increase the solid content in the second MVR evaporation device 1, part of the liquid after the second evaporation in the second MVR evaporation device 1 is sent to the second MVR evaporation device 1 again as a circulating liquid through the seventh circulating pump 77 for the second evaporation (the second reflux ratio is 90). The degree of the second evaporation is monitored by a mass flow meter arranged on the second MVR evaporation device 1, and the second evaporation amount is controlled to be 1.57m 3 H (corresponding to the control of the sodium sulfate concentration in the treatment solution to 0.978Y (87.4 g/L)).
And (3) cooling the second concentrated solution containing the sodium sulfate crystals and the sodium chloride crystals obtained by the second evaporation in a low-temperature treatment tank 55 at the temperature of 20 ℃ for 60min to obtain a treatment solution containing the sodium chloride crystals. The low-temperature treatment tank 55 has a stirring paddle and is rotated at 60r/min.
The treatment liquid containing sodium chloride crystals obtained by the temperature reduction treatment is sent to a third solid-liquid separation device 92 (centrifugal machine) for third solid-liquid separation and is washed to obtain 0.31m per hour 3 Contains NaCl 277.5g/L, na 2 SO 4 87.4g/L、NaOH 10.2g/L、NH 3 And 0.0026g/L of third mother liquor is temporarily stored in the third mother liquor tank 54, and is completely returned to the wastewater conveying pipeline through the ninth circulating pump 79 to be mixed with the catalyst production wastewater to obtain wastewater to be treated. The obtained sodium chloride solid (sodium chloride crystal cake with the water content of 1.5 mass% 440.53kg is obtained per hour, wherein the sodium sulfate content is below 1.5 mass%) is subjected to leaching by 277g/L sodium chloride solution which is equal to the dry basis mass of sodium chloride, and then is dried in a dryer, so that 433.92kg of sodium chloride (the purity is 99.5 mass%) is obtained per hour, and a second washing liquid obtained by washing is circulated to the second MVR evaporation device 1 through a tenth circulating pump 80.
In this example, 4.12m of ammonia water having a concentration of 1.9 mass% was obtained per hour in the first ammonia water tank 51 3 (ii) a 1.57m of ammonia water having a concentration of 0.05% by mass per hour was obtained in the second ammonia water tank 52 3 。
In addition, the tail gas discharged by the eighth heat exchange device 38, the cooling crystallization device 2 and the fourth heat exchange device 34 is introduced into a tail gas absorption tower 83 through a vacuum pump 81 for absorption, circulating water is introduced into the tail gas absorption tower 83, the circulating water circulates in the tail gas absorption tower 83 under the action of the fourth circulating pump 74, water is supplemented into the tail gas absorption tower 83 from a circulating water tank 82 through a third circulating pump 73, and fresh water is supplemented into the circulating water tank 82, so that the temperature and the ammonia content of the working water of the vacuum pump 81 are reduced. Dilute sulfuric acid is further introduced into the tail gas absorption tower 83 to absorb ammonia and the like in the tail gas. The starting phase of MVR evaporation was initiated by steam at a temperature of 143.3 ℃.
Example 2
The treatment of the catalyst production wastewater was carried out in the same manner as in example 1, except that: for NaCl-containing 46g/L, na 2 SO 4 89g/L、NH 4 Cl 15g/L、(NH 4 ) 2 SO 4 29.5g/L, pH is 6.7, and the obtained SO in the wastewater to be treated 4 2- With Cl - In a molar ratio of 1:1.46, and the temperature of the wastewater to be treated after heat exchange through the eighth heat exchange device 38 is 102 ℃.
The temperature of the first evaporation is 95 ℃, the pressure is-36.36 kPa,the evaporation capacity was 4.51m 3 H; cooling and crystallizing at-4 deg.C for 120min; the second evaporation temperature was 107 deg.C, the pressure was 0kPa, and the evaporation capacity was 0.54m 3 H; the temperature of the cooling treatment is 25 ℃, and the time is 58min.
The first solid-liquid separation apparatus 93 yielded 614.99kg of sodium sulfate crystal cake containing 1.5 mass% of water per hour, wherein the sodium chloride content was 1.5 mass% or less, and eluted with 64g/L of a sodium sulfate solution equivalent to the dry basis mass of the sodium sulfate crystal cake, and after drying, 605.77kg of sodium sulfate (purity of 99.4 mass%) was yielded 1.39 m/hour 3 Contains NaCl 268.7g/L, na 2 SO 4 64.4g/L、NaOH 1.15g/L、NH 3 0.44g/L of the first mother liquor (Cl) - Has a concentration of 4.593mol/L, SO 4 2- The concentration of (1) is 0.4535 mol/L).
The second solid-liquid separation device 91 obtains 158.68kg of sodium sulfate decahydrate crystal cake containing 55 mass% of water per hour, the purity is 98.3 mass%), and the catalyst production wastewater is returned to the first evaporation after being dissolved; 1.27m per hour 3 The concentration of NaCl is 295.5g/L, na 2 SO 4 14.4g/L、NaOH 1.26g/L、NH 3 0.48g/L of the second mother liquor.
The third solid-liquid separation device 92 obtains 314.32kg of sodium chloride crystal cake with the water content of 1.4 mass% per hour, and finally obtains 309.92kg of sodium chloride (the purity is 99.5 mass%) per hour; yield 0.222m per hour 3 The concentration of NaCl is 279.5g/L, na 2 SO 4 82.2g/L、NaOH 7.2g/L、NH 3 0.0028g/L of the third mother liquor.
4.51m of ammonia water having a concentration of 1.3% by mass was obtained per hour in the first ammonia water tank 51 3 (ii) a 1.14m of aqueous ammonia having a concentration of 0.05% by mass per hour was obtained in the second aqueous ammonia tank 52 3 。
Example 3
The treatment of the catalyst production wastewater was carried out in the same manner as in example 1, except that: for NaCl-containing 82g/L, na 2 SO 4 42g/L、NH 4 Cl 36.5g/L、(NH 4 ) 2 SO 4 19g/L, pH is 6.2 catalyst production wastewaterTreating to obtain SO in the wastewater to be treated 4 2- With Cl - In a molar ratio of 1:5.20, the temperature of the wastewater to be treated after heat exchange by the eighth heat exchange device 38 is 107 ℃.
The first evaporation temperature is 100 deg.C, the pressure is-22.82 kPa, and the evaporation capacity is 3.47m 3 H; cooling and crystallizing at 0 deg.C for 120min; the temperature of the second evaporation is 105 ℃, the pressure is-7.02 kPa, and the evaporation capacity is 2.16m 3 H; the temperature of the temperature reduction treatment is 30 ℃, and the time is 55min.
The first solid-liquid separation apparatus 93 yielded 315.15kg of sodium sulfate crystal cake containing 1.4 mass% of water per hour, wherein the sodium chloride content was 1.5 mass% or less, and eluted with 60g/L of a sodium sulfate solution equivalent to the dry basis mass of the sodium sulfate crystal cake, and after drying, 310.74kg of sodium sulfate (purity of 99.5 mass%) was yielded 2.71 m/hour 3 Containing 279.1g/L, na NaCl 2 SO 4 60.3g/L、NaOH 2.2g/L、NH 3 0.30g/L of the first mother liquor (containing Cl) - 4.771mol/L，SO 4 2- 0.4246mol/L)。
The second solid-liquid separation device 91 obtains 278.01kg of sodium sulfate decahydrate crystal filter cake containing 56 mass% of water in a purity of 98.6 mass% per hour, and the catalyst production wastewater is returned to the first evaporation after being dissolved; obtained 2.49m per hour 3 The concentration of NaCl is 304.3g/L, na 2 SO 4 16.8g/L、NaOH 2.39g/L、NH 3 0.33g/L of the second mother liquor.
The third solid-liquid separation device 92 obtains 620.36kg of sodium chloride crystal cake with the water content of 1.5 mass% per hour, and finally obtains 611.05kg of sodium chloride (the purity is 99.5 mass%) per hour; 0.527m per hour 3 The concentration of NaCl 281g/L, na 2 SO 4 78.5g/L、NaOH 11.3g/L、NH 3 0.0016g/L of a third mother liquor.
3.47m of 2.2 mass% ammonia water was obtained per hour in the first ammonia water tank 51 3 (ii) a 2.16m of ammonia water having a concentration of 0.038 mass% was obtained per hour in the second ammonia water tank 52 3 。
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (45)
1. Method for treating catalyst production wastewater containing NH 4 + 、SO 4 2- Cl-and Na + Characterized in that the method comprises the following steps,
1) Carrying out first evaporation on the wastewater to be treated to obtain first ammonia-containing steam and a first concentrated solution containing sodium sulfate crystals;
2) Carrying out first solid-liquid separation on the first concentrated solution containing the sodium sulfate crystals, and cooling and crystallizing a liquid phase obtained by the first solid-liquid separation to obtain a crystallization solution containing the sodium sulfate crystals;
3) Carrying out second solid-liquid separation on the crystallization liquid containing the sodium sulfate crystals, and carrying out second evaporation on a liquid phase obtained by the second solid-liquid separation to obtain second ammonia-containing steam and a second concentrated solution containing the sodium chloride crystals;
4) Cooling the second concentrated solution containing the sodium chloride crystals to obtain a treatment solution containing the sodium chloride crystals;
5) Carrying out third solid-liquid separation on the treatment liquid;
before the wastewater to be treated is subjected to first evaporation, adjusting the pH value of the wastewater to be treated to be more than 9;
relative to 1mol of SO contained in the wastewater to be treated 4 2- Cl contained in the wastewater to be treated - Is 14mol or less;
the first evaporation does not crystallize sodium chloride out;
the conditions of the second evaporation include: the temperature is 45-175 ℃, and the pressure is-95 kPa-653 kPa; the temperature of the temperature reduction treatment is 15-35 ℃;
the wastewater to be treated contains the catalyst production wastewater and a liquid phase obtained by the third solid-liquid separation;
NH in the catalyst production wastewater 4 + Is more than 8mg/L, SO 4 2- Is more than 1g/L, cl - Over 970mg/L of Na + Is more than 510 mg/L.
2. The process of claim 1, wherein SO is present in the liquid phase from the first solid-liquid separation 4 2- Has a concentration of 0.01mol/L or more, cl - The concentration of (B) is 5.2mol/L or less.
3. The process of claim 1, wherein SO is present in the liquid phase from the first solid-liquid separation 4 2- Has a concentration of 0.01mol/L or more, cl - The concentration of (B) is 5.0mol/L or less.
4. The method according to claim 1, wherein the SO contained in the liquid phase obtained by the second solid-liquid separation is 1mol relative to the SO contained in the liquid phase 4 2- Cl contained in the liquid phase obtained by the second solid-liquid separation - Is 7.15mol or more.
5. The method as claimed in claim 1, wherein the pH of the wastewater to be treated is adjusted to be greater than 10.8 before the wastewater to be treated is subjected to the first evaporation.
6. The method of claim 1, wherein adjusting the pH is performed with NaOH.
7. The method of claim 1, wherein the first evaporation is such that the concentration of sodium chloride in the first concentrated solution is X or less, wherein X is the concentration of sodium chloride at which both sodium sulfate and sodium chloride in the first concentrated solution are saturated under the conditions of the first evaporation.
8. The process of claim 7, wherein the first evaporation provides a concentration of sodium chloride in the first concentrate of 0.95X to 0.999X.
9. The process according to claim 1, wherein the concentration of sodium chloride in the liquid phase obtained by the first solid-liquid separation is adjusted SO that SO is contained in the liquid phase obtained by the first solid-liquid separation before the cooling crystallization 4 2 -concentration of 0.01mol/L or more, cl - The concentration of (b) is 5.2mol/L or less.
10. The method according to claim 9, wherein adjusting the concentration of sodium chloride in the liquid phase obtained by the first solid-liquid separation is performed by mixing the catalyst production wastewater, a washing liquid for washing sodium sulfate crystals, and/or the liquid phase obtained by the third solid-liquid separation.
11. The method according to any one of claims 1 to 10, wherein the cooling crystallization yields a crystalline liquid containing only sodium sulfate crystals; or, the cooling crystallization is carried out to obtain a crystallization liquid containing sodium sulfate crystals and sodium chloride crystals.
12. The process according to claim 11, wherein the solid phase from the second solid-liquid separation is returned to the first evaporation.
13. The method according to any one of claims 1 to 10, wherein the second evaporation is performed so that the concentration of sodium sulfate in the treatment solution is Y or less, where Y is the concentration of sodium sulfate at which both sodium sulfate and sodium chloride in the treatment solution are saturated under the condition of the temperature reduction treatment.
14. The method of claim 13, wherein the second evaporation provides a sodium sulfate concentration in the treatment solution of 0.9Y to 0.99Y.
15. The method of any one of claims 1-10, wherein the conditions of the first evaporation comprise: the temperature is above 35 ℃ and the pressure is above-98 kPa.
16. The method of claim 15, wherein the conditions of the first evaporation comprise: the temperature is 75-130 ℃, and the pressure is-73 kPa-117 kPa.
17. The method of claim 16, wherein the conditions of the first evaporation comprise: the temperature is 85-130 ℃, and the pressure is-58-117 kPa.
18. The method of claim 17, wherein the conditions of the first evaporation comprise: the temperature is 95-110 ℃, and the pressure is-37 kPa-12 kPa.
19. The method of claim 18, wherein the first evaporation is performed by an MVR evaporation device.
20. The method according to any one of claims 1 to 10, wherein the temperature of the cooling crystallization is from-21.7 ℃ to 17.5 ℃.
21. The method according to claim 20, wherein the temperature of the cooling crystallization is from-20 ℃ to 5 ℃.
22. The method of claim 21, wherein the temperature of the cooling crystallization is from-10 ℃ to 5 ℃.
23. The method of claim 22, wherein the temperature of the cooling crystallization is from-10 ℃ to 0 ℃.
24. The method according to claim 20, wherein the cooling crystallization time is 5min or more.
25. The method according to claim 24, wherein the cooling crystallization time is 60min to 180min.
26. The method of claim 25, wherein the cooling crystallization time is 90min to 150min.
27. The method of any of claims 1-10, wherein the conditions of the second evaporation comprise: the temperature is 60-160 ℃, and the pressure is-87 kPa-414 kPa.
28. The method of claim 27, wherein the conditions of the second evaporation comprise: the temperature is 75-150 ℃, and the pressure is-73 kPa-292 kPa.
29. The method of claim 28, wherein the conditions of the second evaporation comprise: the temperature is 80-130 ℃, and the pressure is-66 kPa-117 kPa.
30. The method of claim 29, wherein the conditions of the second evaporation comprise: the temperature is 95-110 ℃, and the pressure is-37 kPa-12 kPa.
31. The method of claim 27, wherein the second evaporation is performed by an MVR evaporation device.
32. The method according to any one of claims 1 to 10, wherein the reduced temperature treatment temperature is 17.9 ℃ to 35 ℃.
33. The method according to claim 32, wherein the time of the temperature reduction treatment is 5min or more.
34. The method of claim 33, wherein the time of the temperature reduction treatment is 5min to 120min.
35. The method of claim 34, wherein the time of the temperature reduction treatment is 45min to 90min.
36. The method according to any one of claims 1 to 10, wherein the wastewater to be treated is subjected to a first heat exchange with the first ammonia-containing steam and a first ammonia water is obtained before the wastewater to be treated is subjected to a first evaporation.
37. The process according to claim 36, wherein the liquid phase obtained by the first solid-liquid separation is subjected to a second heat exchange with the liquid phase obtained by the second solid-liquid separation before the liquid phase obtained by the first solid-liquid separation is subjected to cooling crystallization.
38. The process according to claim 37, wherein the second ammonia-containing vapor is subjected to a third heat exchange with the liquid phase obtained by the second solid-liquid separation before the liquid phase obtained by the second solid-liquid separation is subjected to a second evaporation, and a second ammonia water is obtained.
39. The method according to any one of claims 1 to 10, further comprising subjecting the first concentrated solution containing sodium sulfate crystals to a first solid-liquid separation to obtain sodium sulfate crystals.
40. The method as claimed in claim 39, further comprising subjecting the crystalline liquid containing sodium sulfate crystals to a second solid-liquid separation to obtain sodium sulfate crystals.
41. The process of claim 39, wherein when the sodium sulfate crystals obtained by the second solid-liquid separation are used as a product, the process further comprises washing the obtained sodium sulfate crystals.
42. The method according to any one of claims 1 to 10, further comprising subjecting the treatment liquid containing sodium chloride crystals to a third solid-liquid separation to obtain sodium chloride crystals.
43. The process of claim 42, further comprising washing the sodium chloride crystals obtained.
44. The process of any one of claims 1 to 10, wherein the catalyst production wastewater is wastewater from a molecular sieve, alumina or refinery catalyst production process.
45. The method of claim 44, further comprising removing impurities and concentrating the catalyst process wastewater.
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| US16/115,167 US10829401B2 (en) | 2017-08-28 | 2018-08-28 | Apparatus and method for treating waste water containing ammonium salts |
| NL1042971A NL1042971B1 (en) | 2017-08-28 | 2018-08-28 | Apparatus and Method for Treating Waste Water Containing Ammonium Salts |
| JP2018159150A JP6653736B2 (en) | 2017-08-28 | 2018-08-28 | Equipment for treating wastewater containing ammonium salts |
| JP2020011633A JP7051912B2 (en) | 2017-08-28 | 2020-01-28 | Ammonium salt-containing wastewater treatment equipment and methods |
| US17/037,529 US11820690B2 (en) | 2017-08-28 | 2020-09-29 | Apparatus and method for treating waste water containing ammonium salts |
| JP2022056042A JP7305836B2 (en) | 2017-08-28 | 2022-03-30 | Apparatus and method for treating wastewater containing ammonium salt |
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| CN1944256A (en) * | 2006-10-25 | 2007-04-11 | 中国中轻国际工程有限公司 | Process for producing sodium sulfate and sodium chloride in Na2SO4-NaCl-H2O system |
| CN102616891A (en) * | 2011-12-31 | 2012-08-01 | 广东先导稀材股份有限公司 | Method for treating sewage containing sodium sulfate and sodium chloride |
| CN103172088A (en) * | 2013-04-11 | 2013-06-26 | 南风化工集团股份有限公司 | Application of MVR (mechanical vapor recompression) crystallizing evaporator in sodium sulfate and sodium chloride separation technology |
| CN104609633A (en) * | 2015-02-16 | 2015-05-13 | 阮氏化工（常熟）有限公司 | Method and device for utilizing sewage containing ammonia and sodium |
| CN105036222A (en) * | 2015-08-19 | 2015-11-11 | 石家庄工大化工设备有限公司 | High-salinity wastewater recovery treatment method |
| CN105110542A (en) * | 2015-09-14 | 2015-12-02 | 济宁璟华环保科技有限公司 | Zero-discharge salt separation and purification method for industrial high-salt wastewater |
| CN106145223A (en) * | 2016-08-01 | 2016-11-23 | 江苏星瑞化工工程科技有限公司 | A kind of processing method of high-salt wastewater |
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