CN115108744A - Process for decomposing phosphogypsum and co-producing cement - Google Patents
Process for decomposing phosphogypsum and co-producing cement Download PDFInfo
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- PASHVRUKOFIRIK-UHFFFAOYSA-L calcium sulfate dihydrate Chemical compound O.O.[Ca+2].[O-]S([O-])(=O)=O PASHVRUKOFIRIK-UHFFFAOYSA-L 0.000 title claims abstract description 100
- 238000000034 method Methods 0.000 title claims abstract description 29
- 239000004568 cement Substances 0.000 title claims abstract description 28
- 230000003647 oxidation Effects 0.000 claims abstract description 53
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 53
- 238000000354 decomposition reaction Methods 0.000 claims abstract description 33
- 239000000843 powder Substances 0.000 claims abstract description 32
- 230000002829 reductive effect Effects 0.000 claims abstract description 22
- 239000002994 raw material Substances 0.000 claims abstract description 19
- 238000001354 calcination Methods 0.000 claims abstract description 11
- 238000001035 drying Methods 0.000 claims abstract description 5
- 238000000227 grinding Methods 0.000 claims abstract description 5
- 239000003469 silicate cement Substances 0.000 claims abstract description 3
- 239000011593 sulfur Substances 0.000 claims description 57
- 229910052717 sulfur Inorganic materials 0.000 claims description 57
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 46
- 239000003245 coal Substances 0.000 claims description 45
- 238000004458 analytical method Methods 0.000 claims description 26
- 239000000126 substance Substances 0.000 claims description 26
- 239000000203 mixture Substances 0.000 claims description 18
- 239000010881 fly ash Substances 0.000 claims description 15
- 229910052500 inorganic mineral Inorganic materials 0.000 claims description 12
- 239000011707 mineral Substances 0.000 claims description 12
- 229910052799 carbon Inorganic materials 0.000 claims description 11
- 238000001514 detection method Methods 0.000 claims description 10
- 238000004519 manufacturing process Methods 0.000 claims description 10
- 239000004927 clay Substances 0.000 claims description 4
- 239000004576 sand Substances 0.000 claims description 4
- 239000000463 material Substances 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims 1
- 238000006477 desulfuration reaction Methods 0.000 abstract description 12
- 230000023556 desulfurization Effects 0.000 abstract description 12
- 230000002411 adverse Effects 0.000 abstract description 3
- 230000000694 effects Effects 0.000 abstract description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 49
- 229910052742 iron Inorganic materials 0.000 description 22
- 239000002689 soil Substances 0.000 description 20
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 8
- 235000019738 Limestone Nutrition 0.000 description 8
- 239000006028 limestone Substances 0.000 description 8
- 230000001590 oxidative effect Effects 0.000 description 7
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 5
- 239000011398 Portland cement Substances 0.000 description 5
- 229910004298 SiO 2 Inorganic materials 0.000 description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 4
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 4
- 239000002956 ash Substances 0.000 description 3
- -1 silicon-aluminum-iron Chemical compound 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000005245 sintering Methods 0.000 description 2
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000004566 building material Substances 0.000 description 1
- ZHZFKLKREFECML-UHFFFAOYSA-L calcium;sulfate;hydrate Chemical compound O.[Ca+2].[O-]S([O-])(=O)=O ZHZFKLKREFECML-UHFFFAOYSA-L 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 239000000571 coke Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 235000013601 eggs Nutrition 0.000 description 1
- 230000003203 everyday effect Effects 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000002686 phosphate fertilizer Substances 0.000 description 1
- 239000002367 phosphate rock Substances 0.000 description 1
- OJMIONKXNSYLSR-UHFFFAOYSA-N phosphorous acid Chemical compound OP(O)O OJMIONKXNSYLSR-UHFFFAOYSA-N 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000002910 solid waste Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B7/00—Hydraulic cements
- C04B7/36—Manufacture of hydraulic cements in general
- C04B7/38—Preparing or treating the raw materials individually or as batches, e.g. mixing with fuel
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B7/00—Hydraulic cements
- C04B7/02—Portland cement
- C04B7/04—Portland cement using raw materials containing gypsum, i.e. processes of the Mueller-Kuehne type
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B7/00—Hydraulic cements
- C04B7/36—Manufacture of hydraulic cements in general
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Processing Of Solid Wastes (AREA)
Abstract
The invention discloses a process for decomposing phosphogypsum and co-producing cement, which comprises the steps of obtaining phosphogypsum, drying, crushing, grinding, then feeding into a reduction furnace through a preheater for CaSO 4 Decomposition of (2); feeding the reduced and decomposed powder into an oxidation furnace to oxidize the residual CaS; the silicoferrite raw materials which are proportioned and measured according to the silicate cement clinker are mixed and ground, then enter a side branch preheater, and enter a rotary kiln together with the decomposition product of the phosphogypsum for calcining the clinker; by adopting the method, the decomposition and the desulfurization of the phosphogypsum are respectively carried out in the reduction furnace and the oxidation furnace, so that the phosphogypsum is subjected to two steps of reduction and oxidation and then is subjected to more thorough desulfurization, and simultaneously CaS and CaSO are avoided 4 Adverse effects on clinker calcination in the rear rotary kiln, and control of atmospheric conditions and energy savings through a gas circulation system using tertiary air.
Description
Technical Field
The invention belongs to the technical field of building materials, and particularly relates to a process for decomposing phosphogypsum and co-producing cement.
Background
Phosphogypsum is a solid waste generated in a wet-process phosphoric acid process, the composition of the phosphogypsum is complex, besides calcium sulfate hydrate, incompletely decomposed phosphorite, residual phosphoric acid, fluoride, acid insoluble substances, organic matters and the like are also contained, wherein the existence of fluorine and the organic matters has the greatest influence on the resource utilization of the phosphogypsum, the stacking occupies a large amount of land, and the water resource and the land resource are polluted. According to the statistics of the China phosphate fertilizer industry Association, the total amount of phosphogypsum discharged in 2020 is about 7500-8000 million tons, and phosphogypsum is tried to be used by a plurality of industries, but the utilization rate is low, the domestic stock reaches more than 6 hundred million tons, and the world reaches more than 60 hundred million tons, and the resource utilization of the phosphogypsum is a worldwide problem.
The cement industry is one of the largest sources of carbon dioxide emissions in the world, accounting for 5-8% of the global emissions, of which 60% is derived from the calcination of limestone. The phosphogypsum replaces limestone to be used as a CaO source to produce the cement clinker, which is a direction with the challenge and significance for solving the resource utilization of the phosphogypsum, can ensure that the utilization rate of the phosphogypsum reaches more than 90 percent, and can avoid the problem of carbon dioxide emission of the limestone in the cement production.
CaSO 4 Relative to CaCO 3 In other words, the phosphogypsum can be decomposed only at a higher temperature, and in order to make the phosphogypsum meet the requirements of cement production and reduce the operation difficulty and energy consumption in the process, the phosphogypsum needs to be decomposed and desulfurized at a lower temperature. Many documents report researches on the decomposition of phosphogypsum by using carbonaceous raw materials, carbon monoxide atmosphere, elemental sulfur and the like, although the decomposition rate of the phosphogypsum can reach more than 99% under the low-temperature environment of 1000-1100 ℃, the realization of the desulfurization rate of more than 95% is difficult, the atmosphere needs to be stably and accurately regulated, the difficulty in the actual production process is increased undoubtedly, and if the desulfurization rate does not meet the requirement, the sulfur can be used as CaSO in the clinker sintering stage 4 The form of CaS or solid solution, which makes CaO insufficient on one hand and CaSO on the other hand for the system for producing the cement clinker by taking the phosphogypsum as the main CaO source 4 Sulfur-containing substances such as CaS and the like generate more SO when being desulfurized at high temperature 3 Influence the atmosphere in the kiln, and finally, seriously influence C 3 The formation of S also has a number of adverse effects on the production and use of clinker.
At present, the factory for producing sulfuric acid and cement by using phosphogypsum is built in China, and the main method is that the phosphogypsum is dried and dehydrated, and is matched with coke, clay, sand shale and the like according to the clinker, and is calcined in a hollow rotary kiln to prepare the clinker, and SO in kiln gas 2 The sulfuric acid is prepared after conversion and absorption, the energy consumption and the cost are high by adopting the method, and the decomposition and the desulfurization of the phosphogypsum and the calcination of clinker are carried out in a kiln. Because of CaSO 4 Is more easily reduced and decomposed into CaS under the low-temperature reducing atmosphere of 900-1100 ℃, so that CaSO 4 High decomposition rate and high desulfurization rate are difficult to realize at one time, and in order to ensure that the high decomposition rate of the phosphogypsum can cause the desulfurization rate of the phosphogypsum in a low-temperature reducing atmosphere section at the tail of a kiln to be further reduced to be difficult to reach 90 percent by a person skilled in the art, so that most of the residual CaSO 4 CaS is subjected to a series of reactions in a high-temperature section in the middle of the kiln to remove sulfur, and C in the finally prepared clinker 3 The S content is less than 30 percent, so that the color and the strength of the clinker are lighter, and the produced clinker releases H due to the desulfurization of CaS during the high-temperature sintering of the clinker and the small amount of the CaS in the clinker 2 The smelly eggs of S are toxic and harmful to human health, so that the popularization and application are difficult.
Disclosure of Invention
The invention aims to provide a process for decomposing phosphogypsum and co-producing cement, which carries out complete desulfurization treatment on the phosphogypsum in two steps and has the utilization rate of more than 90 percent when being applied to the preparation of cement clinker.
In order to achieve the purpose, the technical scheme is as follows:
a process for decomposing phosphogypsum and co-producing cement comprises the following steps:
(1) obtaining phosphogypsum, drying, crushing, grinding, and then feeding into a reduction furnace through a preheater for CaSO 4 Decomposition of (2);
(2) feeding the reduced and decomposed powder into an oxidation furnace to oxidize the residual CaS;
(3) the silicoferrite raw materials proportioned and measured according to the silicate cement clinker are mixed and ground, then enter a side branch preheater, and enter a rotary kiln together with the decomposition product of the phosphogypsum for calcining the clinker.
According to the scheme, the aluminosilicoferrite raw material in the step 3 is one or more of sand shale, coal gangue, clay and fly ash; SO in the chemical components of the phosphogypsum 3 The remaining chemical components are measured in accordance with a substance mainly containing CaO, calculated in terms of loss on ignition per se.
According to the scheme, in the reducing furnace in the step 1, a reducing atmosphere is created by adding coal raw materials and introducing tertiary air, and the volume concentration of CO in the reducing furnace is controlled to be 2-6%; the temperature was maintained at 900 ℃ and 1000 ℃.
According to the scheme, the coal raw material is common coal or high-sulfur coal for producing cement, wherein C and SO in phosphogypsum 3 Is 0.6 to 1.0.
According to the scheme, the introduction speed and the gas amount of the tertiary air are adjusted through the total sulfur analysis detection result of powder at the outlet of the reduction furnace, and the smaller the total sulfur content is, the better the total sulfur content is.
According to the scheme, in the step 2, the oxidation furnace creates an oxidation atmosphere by introducing tertiary air, and O in the oxidation furnace is controlled 2 The volume concentration of (a) is 2% -10%; the temperature was maintained at 1000 ℃ and 1100 ℃.
According to the scheme, the introduction speed and the gas amount of the tertiary air are adjusted through the total sulfur analysis detection result of powder at the outlet of the oxidation furnace, and the smaller the total sulfur content is, the better the total sulfur content is.
According to the scheme, C in the mineral composition of the obtained clinker 3 S is 25% -65%, C 2 S is 10% -50%, C 3 A is 2% -10%, C 4 AF is 5 to 15 percent.
Compared with the prior art, the invention has the following beneficial effects:
the method of the invention is adopted, the decomposition and the desulfurization of the phosphogypsum are respectively put into a reducing furnace and an oxidizing furnace to carry out the decomposition and the desulfurization of the phosphogypsum, so that the phosphogypsum reaches higher decomposition rate in the reducing furnace, and then the residual CaS is converted towards CaO in a weak oxidation atmosphere instead of CaSO in the oxidizing furnace 4 The desulfurization is more thorough after the two steps, thereby avoiding CaS and CaSO 4 Adverse effect on clinker calcination in the rear rotary kiln and control of atmospheric conditions by means of a gas circulation system using tertiary airAnd saves energy. The reducing atmosphere in the reducing furnace is controlled by the tertiary air-heat air and the coal raw material, and the weak oxidizing atmosphere in the oxidizing furnace is controlled by the tertiary air-heat air and the oxygen-free gas which is fed into the oxidizing furnace after being combusted in the kiln.
The phosphogypsum can be effectively utilized, the utilization rate of the phosphogypsum can reach more than 90 percent, natural limestone is not needed, 400 million tons of phosphogypsum can be processed every year according to the calculation of a cement production line producing 5000 tons of clinker every day, and 100 million tons of carbon emission can be reduced every year.
Drawings
FIG. 1: the invention relates to a flow chart of a process for decomposing phosphogypsum and co-producing cement.
FIG. 2 is a schematic diagram: examples 1, 2, 3, 4 gave XRD patterns of clinker.
Detailed Description
The following examples further illustrate the technical solutions of the present invention, but should not be construed as limiting the scope of the present invention.
The specific embodiment provides a process for decomposing phosphogypsum and co-producing cement, which is shown in the attached drawing 1:
(1) obtaining phosphogypsum, drying, crushing, grinding, and then feeding into a reduction furnace through a preheater for CaSO 4 Decomposition of (2); the reducing furnace creates reducing atmosphere by adding coal raw materials and introducing tertiary air; the temperature is kept at 900-1000 ℃; the coal raw material is common coal or high-sulfur coal for cement production, wherein C and SO in phosphogypsum 3 The molar ratio of (A) is 0.6-1.0; the introduction speed and the gas amount of the tertiary air are adjusted through the total sulfur analysis and detection result of powder at the outlet of the reducing furnace, and the volume concentration of CO in the reducing furnace is controlled to be 2-6% as the total sulfur content is smaller.
(2) Feeding the reduced and decomposed powder into an oxidation furnace to oxidize the residual CaS; the oxidation furnace creates an oxidation atmosphere by introducing tertiary air; the temperature is kept at 1000 ℃ and 1100 ℃; the introduction speed and the gas amount of the tertiary air are adjusted through the total sulfur analysis and detection result of powder at the outlet of the oxidation furnace, and the smaller the total sulfur content is, the better the total sulfur content is, the O content in the oxidation furnace is controlled 2 The volume concentration of (A) is 2-10%.
(3) According to the introduction of portland cement clinkerProportionally measured silicon-aluminum-iron raw materials are mixed and ground, then enter a side branch preheater, and enter a rotary kiln together with a decomposition product of phosphogypsum to calcine clinker; in the mineral composition of the obtained clinker C 3 S is 25% -65%, C 2 S is 10% -50%, C 3 A is 2% -10%, C 4 AF is 5 to 15 percent.
In a specific embodiment, the aluminosilicoferrite raw material is one or more of common raw materials such as sand shale, coal gangue, clay, fly ash and the like; SO in the chemical components of the phosphogypsum 3 The remaining chemical components are measured in accordance with a substance mainly containing CaO in the self ignition loss. The method comprises the following steps of obtaining phosphogypsum and a silicon-aluminum-iron auxiliary material, drying, crushing and grinding the phosphogypsum and the silicon-aluminum-iron auxiliary material, and then carrying out chemical component analysis, wherein in the specific embodiment, the chemical components of phosphogypsum, iron ore soil, fly ash and coal gangue are shown in a table 1:
TABLE 1 analysis of chemical composition
| Name (R) | Loss on ignition | SiO 2 | Al 2 O 3 | Fe 2 O 3 | CaO | MgO | SO 3 | K 2 O | Na 2 O |
| Phosphogypsum | 20.04 | 6.04 | 0.30 | 0.28 | 29.75 | 0.02 | 42.28 | 0.22 | 0.12 |
| Iron ore soil | 3.27 | 48.9 | 15.55 | 15.9 | 7.56 | 4.41 | 0.01 | 0.78 | 2.79 |
| Fly ash | 5.33 | 43.41 | 32.88 | 6.44 | 6.72 | 0.7 | 1.2 | 0.81 | 0.47 |
| Coal gangue | 4.63 | 76.3 | 6.62 | 4.64 | 1.91 | 2.35 | 0.48 | 1.34 | 0.55 |
Example 1
1. Proportioning design
SO in chemical components of phosphogypsum 3 Calculated in the loss on ignition of the coal, according to the loss on ignition of 20.04% + 42.28% + 62.32%, the rest chemical components are measured corresponding to substances mainly containing CaO, similar to limestone, and then are mixed with iron ore according to the design of portland cement clinker, the mixture ratio is shown in table 2, and the weight ratio of phosphogypsum: the iron ore soil is 91: the theoretical mineral composition is shown in table 3:
TABLE 2 proportions
| Name(s) | Loss on ignition | SiO 2 | Al 2 O 3 | Fe 2 O 3 | CaO | MgO | SO 3 | K 2 O | Na 2 O | Proportioning |
| Phosphogypsum | 62.32 | 6.04 | 0.30 | 0.28 | 29.75 | 0.02 | 0 | 0.22 | 0.12 | 91 |
| Iron ore soil | 3.27 | 48.9 | 15.55 | 15.9 | 7.56 | 4.41 | 0.01 | 0.78 | 2.79 | 9 |
TABLE 3 theoretical mineral composition
| KH | SM | IM | C3S | C2S | C3A | C4AF |
| 0.88 | 2.95 | 1.00 | 52.45 | 22.09 | 3.42 | 11.14 |
2. Reductive decomposition and oxidation of phosphogypsum
Feeding the proportioned phosphogypsum powder into a reduction furnace through a preheater for CaSO 4 The reducing furnace creates a reducing atmosphere by adding coal raw materials and introducing tertiary air, high-sulfur coal is added, and the conventional analysis results are shown in table 4:
TABLE 4 general analysis of high-sulfur coal
| Name (R) | Moisture content | Ash content | Volatile component | Fixed carbon content | All sulfur | Qnet,ad | Qnet,d |
| High sulfur coal | 1.42 | 23.48 | 10.25 | 64.85 | 2.99 | 25.25 | 26.33 |
The fixed carbon content and SO in phosphogypsum are designed here 3 The molar ratio of (3) to (3) is 0.8, the weight of the high-sulfur coal added to the phosphogypsum with the weight of 91 in the mixture ratio is (91 × 0.4228/80) × 0.8 × 12/0.6485 ═ 7.12.
The temperature of the reduction furnace is set to 950 ℃, and the total sulfur analysis of powder at an outlet of the reduction furnace is used for measuring SO 3 The content was 7.7%. Then the powder after reduction decomposition enters an oxidation furnace to oxidize the residual CaS, and the oxidation furnace is filled with tertiary airCreating an oxidizing atmosphere, setting the temperature of the oxidizing furnace at 1050 ℃, and analyzing the total sulfur of the powder at an outlet to obtain SO 3 The content was 2.5%.
It should be noted here that the velocity or the gas amount of the tertiary air introduced into the reduction furnace and the oxidation furnace, which is influenced by the process and the equipment, needs to be evaluated and adjusted by the total sulfur analysis and detection result of the powder at the furnace outlet in order to achieve the proper atmosphere condition, and the smaller the total sulfur content is, the better the smaller the total sulfur content is, in this example, the volume concentration of CO in the reduction furnace is controlled to be 4%, and the O in the oxidation furnace is controlled to be 4% 2 The volume concentration of (3) is 5%.
3. Calcination of clinker
The phosphogypsum after reductive decomposition and oxidation directly enters the rotary kiln from the kiln tail, and simultaneously, the iron ore soil independently enters the rotary kiln from the kiln tail, and the phosphogypsum and the iron ore soil after reductive decomposition and oxidation are prepared into clinker in the rotary kiln.
Example 2
1. Proportioning design
SO in chemical components of phosphogypsum 3 Calculated in the loss on ignition of the coal, according to the loss on ignition of 20.04% + 42.28% + 62.32%, the rest chemical components are measured corresponding to substances mainly containing CaO, similar to limestone, and then are mixed with fly ash and iron ore according to the design of portland cement clinker, the mixture ratio is shown in table 5, and the weight ratio of the phosphogypsum is adopted: fly ash: the iron ore soil is 92: 3: the theoretical mineral composition is shown in table 6:
TABLE 5 proportions
| Name (R) | Loss on ignition | SiO 2 | Al 2 O 3 | Fe 2 O 3 | CaO | MgO | SO 3 | K 2 O | Na 2 O | Proportioning |
| Phosphogypsum | 62.32 | 6.04 | 0.30 | 0.28 | 29.75 | 0.02 | 0 | 0.22 | 0.12 | 92 |
| Fly ash | 5.33 | 43.41 | 32.88 | 6.44 | 6.72 | 0.7 | 1.2 | 0.81 | 0.47 | 3 |
| Iron ore soil | 3.27 | 48.9 | 15.55 | 15.9 | 7.56 | 4.41 | 0.01 | 0.78 | 2.79 | 5 |
TABLE 6 theoretical mineral composition
| KH | SM | IM | C3S | C2S | C3A | C4AF |
| 0.926 | 2.832 | 1.637 | 60.58 | 13.05 | 7.25 | 8.34 |
2. Reductive decomposition and oxidation of phosphogypsum
Feeding the proportioned phosphogypsum powder into a reduction furnace through a preheater for CaSO 4 The reducing furnace creates a reducing atmosphere by adding coal raw materials and introducing tertiary air, high-sulfur coal is added, and the conventional analysis results are shown in table 7:
TABLE 7 conventional analysis of high-sulfur coal
| Name(s) | Moisture content | Ash content | Volatile component | Fixed carbon content | All sulfur | Qnet,ad | Qnet,d |
| High sulfur coal | 1.42 | 23.48 | 10.25 | 64.85 | 2.99 | 25.25 | 26.33 |
The fixed carbon content and SO in phosphogypsum are designed here 3 The molar ratio of (2) to (3) is 0.8, the weight of the high-sulfur coal added to the phosphogypsum with the weight of 92 in the mixture ratio is (92 × 0.4228/80) × 0.8 × 12/0.6485 ═ 7.20.
The temperature of the reduction furnace is set to 960 ℃, and SO is measured by total sulfur analysis of powder at the outlet 3 The content was 8.3%. Then feeding the reduced and decomposed powder into an oxidation furnace to oxidize the residual CaS, wherein the oxidation furnace creates an oxidation atmosphere by introducing tertiary air, the temperature of the oxidation furnace is set to 1060 ℃, and the total sulfur analysis of the powder at an outlet is used for measuring SO 3 The content was 3.2%.
It should be noted here that the velocity or gas amount of the tertiary air introduced into the reduction furnace and the oxidation furnace, which is influenced by the process and the equipment, needs to be evaluated and adjusted by the total sulfur analysis and detection result of the powder at the furnace outlet in order to achieve the proper atmosphere condition, and the smaller the total sulfur content is, the better the smaller the total sulfur content is, in this example, the volume concentration of CO in the reduction furnace is controlled to be 6%, and the O in the oxidation furnace is controlled to be 6% 2 The volume concentration of (3) is 5%.
3. Calcination of clinker
The phosphogypsum after reductive decomposition and oxidation directly enters the rotary kiln from the kiln tail, and simultaneously, the fly ash and the iron ore soil independently enter the rotary kiln from the other kiln tail, and the phosphogypsum after reductive decomposition and oxidation, the fly ash and the iron ore soil are prepared into clinker in the rotary kiln.
Example 3
1. Proportioning design
SO in the chemical components of the phosphogypsum 3 Calculated in the loss on ignition of the coal, the loss on ignition is 20.04% + 42.28% ~ 62.32%The residual chemical components are measured corresponding to substances mainly containing CaO, are used similarly to limestone, and are mixed with fly ash and iron ore soil according to the design proportion of portland cement clinker, the proportion is shown in table 8, and the weight ratio of phosphogypsum is as follows: fly ash: the iron ore soil is 91: 4: the theoretical mineral composition is shown in table 9:
TABLE 8 proportions
| Name(s) | Loss on ignition | SiO 2 | Al 2 O 3 | Fe 2 O 3 | CaO | MgO | SO 3 | K 2 O | Na 2 O | Proportioning |
| Phosphogypsum | 62.32 | 6.04 | 0.30 | 0.28 | 29.75 | 0.02 | 0 | 0.22 | 0.12 | 91 |
| Fly ash | 5.33 | 43.41 | 32.88 | 6.44 | 6.72 | 0.7 | 1.2 | 0.81 | 0.47 | 4 |
| Iron ore soil | 3.27 | 48.9 | 15.55 | 15.9 | 7.56 | 4.41 | 0.01 | 0.78 | 2.79 | 5 |
TABLE 9 theoretical mineral composition
| KH | SM | IM | C3S | C2S | C3A | C4AF |
| 0.861 | 2.635 | 1.809 | 46.62 | 25.23 | 8.82 | 8.65 |
2. Reductive decomposition and oxidation of phosphogypsum
Feeding the proportioned phosphogypsum powder into a reduction furnace through a preheater for CaSO 4 The reducing furnace creates a reducing atmosphere by adding coal raw materials and introducing tertiary air, high-sulfur coal is added, and the conventional analysis results are shown in table 10:
TABLE 10 conventional analysis of high-sulfur coal
The fixed carbon content and SO in phosphogypsum are designed here 3 Is 0.7, then the ratio isThe weight of the high-sulfur coal required to be added to the phosphogypsum with the medium weight of 91 is (91 × 0.4228/80) × 0.7 × 12/0.6485 ═ 6.23.
The temperature of the reduction furnace is set to 950 ℃, and the total sulfur analysis of powder at an outlet of the reduction furnace is used for measuring SO 3 The content was 6.8%. And then feeding the reduced and decomposed powder into an oxidation furnace to oxidize the residual CaS, and introducing tertiary air into the oxidation furnace to create an oxidation atmosphere. The temperature of the oxidation furnace was set to 1060 ℃ and SO was determined by total sulfur analysis of the powder at the outlet 3 The content was 2.4%.
It should be noted here that the velocity or the amount of the tertiary air introduced into the reduction furnace and the oxidation furnace, which is influenced by the process and the equipment, needs to be evaluated and adjusted by the total sulfur analysis and detection result of the powder at the furnace outlet in order to achieve the proper atmosphere condition, and the smaller the total sulfur content is, the better the smaller the total sulfur content is, in this example, the volume concentration of CO in the reduction furnace is controlled to be 3%, and the O in the oxidation furnace is controlled to be 2 The volume concentration of (3) is 6%.
3. Calcination of clinker
The phosphogypsum after reductive decomposition and oxidation directly enters the rotary kiln from the kiln tail, and simultaneously, the fly ash and the iron ore soil independently enter the rotary kiln from the other kiln tail, and the phosphogypsum after reductive decomposition and oxidation, the fly ash and the iron ore soil are prepared into clinker in the rotary kiln.
Example 4
1. Proportioning design
SO in chemical components of phosphogypsum 3 Calculated in the loss on ignition of the cement, according to the loss on ignition of 20.04% + 42.28% ═ 62.32%, the remaining chemical components are measured corresponding to substances mainly containing CaO, similar to limestone, and then are mixed with iron ore soil and coal gangue according to the design proportion of low-heat portland cement clinker, the proportion is shown in table 11, and the weight ratio of phosphogypsum is adopted: iron ore soil: the coal gangue is 90: 8: 2, theoretical mineral composition is shown in table 12:
TABLE 11 proportions
| Name (R) | Loss on ignition | SiO 2 | Al 2 O 3 | Fe 2 O 3 | CaO | MgO | SO 3 | K 2 O | Na 2 O | Proportioning |
| Phosphogypsum | 62.32 | 6.04 | 0.30 | 0.28 | 29.75 | 0.02 | 0 | 0.22 | 0.12 | 90 |
| Iron ore soil | 3.27 | 48.9 | 15.55 | 15.9 | 7.56 | 4.41 | 0.01 | 0.78 | 2.79 | 8 |
| Coal gangue | 4.63 | 76.3 | 6.62 | 4.64 | 1.91 | 2.35 | 0.48 | 1.34 | 0.55 | 2 |
TABLE 12 theoretical mineral composition
| KH | SM | IM | C3S | C2S | C3A | C4AF |
| 0.792 | 3.332 | 1.018 | 33.50 | 41.70 | 3.48 | 10.56 |
2. Reductive decomposition and oxidation of phosphogypsum
Feeding the proportioned phosphogypsum powder into a reduction furnace through a preheater for CaSO 4 The reducing furnace creates a reducing atmosphere by adding coal raw materials and introducing tertiary air, and coal powder is added, and the conventional analysis results are shown in table 13:
TABLE 13 conventional analysis of coal fines
| Name (R) | Moisture content | Ash content | Volatile component | Fixed carbon content | All sulfur | Qnet,ad | Qnet,d |
| Pulverized coal | 3.23 | 15.14 | 32.30 | 49.33 | 0.97 | 25.51 | 27.43 |
The fixed carbon content and SO in phosphogypsum are designed here 3 Is 0.6, then the weight of the added coal powder required for 90 weight of phosphogypsum in the mixture ratio is (90 × 0.4228/80) × 0.6 × 12/0.4933 ═ 6.94.
The temperature of the reduction furnace is set to 960 ℃, and SO is measured by total sulfur analysis of powder at the outlet 3 The content was 7.5%. Then feeding the reduced and decomposed powder into an oxidation furnace to oxidize the residual CaS, introducing tertiary air into the oxidation furnace to create an oxidation atmosphere, setting the temperature of the oxidation furnace to be 1040 ℃, and measuring the total sulfur of the powder at an outlet to obtain SO 3 The content was 2.3%.
It should be noted here that the velocity or the amount of the tertiary air introduced into the reduction furnace and the oxidation furnace, which is influenced by the process and the equipment, needs to be evaluated and adjusted by the total sulfur analysis and detection result of the powder at the furnace outlet in order to achieve the proper atmosphere condition, and the smaller the total sulfur content is, the better the smaller the total sulfur content is, in this example, the volume concentration of CO in the reduction furnace is controlled to be 3%, and the O in the oxidation furnace is controlled to be 2 The volume concentration of (2) is 8%.
3. Calcination of clinker
The phosphogypsum after reductive decomposition and oxidation directly enters the rotary kiln from the kiln tail, meanwhile, the iron ore soil and the coal gangue independently enter the rotary kiln from the other branch to the kiln tail, and the phosphogypsum after reductive decomposition and oxidation, the iron ore soil and the coal gangue are prepared into clinker in the rotary kiln.
The XRD patterns of the clinkers prepared in the examples 1, 2, 3 and 4 are shown in the figure, and all the clinker minerals are well formed.
The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are within the protection scope of the present invention.
Claims (8)
1. The process for decomposing phosphogypsum and co-producing cement is characterized by comprising the following steps of:
(1) obtaining phosphogypsum, drying, crushing, grinding, and then feeding into a reduction furnace through a preheater for CaSO 4 Decomposition of (2);
(2) feeding the reduced and decomposed powder into an oxidation furnace to oxidize the residual CaS;
(3) the silicoferrite raw materials proportioned and measured according to the silicate cement clinker are mixed and ground, then enter a side branch preheater, and enter a rotary kiln together with the decomposition product of the phosphogypsum for calcining the clinker.
2. The process for decomposing phosphogypsum and co-producing cement according to claim 1, wherein the ferro-silico-aluminous material in step 3 is one or more of sand shale, coal gangue, clay and fly ash; SO in the chemical components of the phosphogypsum 3 The remaining chemical components are measured in accordance with a substance mainly containing CaO in the self ignition loss.
3. The process for decomposing phosphogypsum and CO-producing cement as claimed in claim 1, wherein in the reducing furnace in the step 1, a reducing atmosphere is created by adding coal raw materials and introducing tertiary air, and the volume concentration of CO in the reducing furnace is controlled to be 2% -6%; the temperature was maintained at 900 ℃ and 1000 ℃.
4. The process for the co-production of cement by decomposing phosphogypsum as claimed in claim 3, wherein the process comprises the step of mixing the phosphogypsum with the cementThe coal raw material is common coal or high-sulfur coal for cement production, wherein C and SO in phosphogypsum 3 Is 0.6 to 1.0.
5. The process for co-producing cement through phosphogypsum decomposition according to claim 3, wherein the introduction speed and gas amount of the tertiary air are adjusted according to the total sulfur analysis and detection result of powder at the outlet of the reducing furnace, so that the smaller the total sulfur content is, the better the total sulfur content is.
6. The process for co-production of cement through decomposition of phosphogypsum as claimed in claim 1, wherein in step 2, the oxidation furnace is used for creating an oxidation atmosphere by introducing tertiary air, and O in the oxidation furnace is controlled 2 The volume concentration of (A) is 2-10%; the temperature was maintained at 1000 ℃ and 1100 ℃.
7. The process for decomposing phosphogypsum and co-producing cement according to claim 6, wherein the introduction speed and gas amount of the tertiary air are adjusted according to the total sulfur analysis and detection result of powder at the outlet of the oxidation furnace, so that the smaller the total sulfur content is, the better the total sulfur content is.
8. The process for the co-production of cement by the decomposition of phosphogypsum according to claim 1, wherein the mineral composition of the obtained clinker is C 3 S is 25% -65%, C 2 S is 10% -50%, C 3 A is 2% -10%, C 4 AF is 5 to 15 percent.
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