CN113582367A - Treatment process and system for simultaneously removing calcium ions and COD (chemical oxygen demand) in acidic wastewater - Google Patents
Treatment process and system for simultaneously removing calcium ions and COD (chemical oxygen demand) in acidic wastewater Download PDFInfo
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Abstract
The invention discloses a treatment method for simultaneously removing calcium ions and COD (chemical oxygen demand) in acidic wastewater, which comprises the following steps: cold rolling acid wastewater enters a neutralization tank, and strong alkali solution is added into the neutralization tank for neutralization; after passing through the neutralization tank, the pH value of the cold rolling acid wastewater is 6.8-8.1; cold rolling acid wastewater enters a mixing sedimentation tank, stirring is carried out, 600-810 mg/L of sodium carbonate solution is added, and calcium carbonate precipitation is formed by sodium carbonate and calcium ions; after passing through the mixing sedimentation tank, the wastewater enters a ceramic microfiltration system, and a modified ceramic microfiltration membrane is placed in the ceramic microfiltration system; the obtained cold rolling acid wastewater enters a modified diatomite adsorption tower through a three-stage lift pump; modified diatomite is filled in the modified diatomite adsorption tower; and the obtained cold rolling acid wastewater enters a subsequent process. The pH value of the treated cold rolling acid wastewater is 7.1-8.6, the calcium ion is 3-9 mg/L, and the COD is 13-25 mg/L. The cold rolling acid wastewater can be discharged through a drainage pump, and can also enter a high-pressure reverse osmosis or electrodialysis system through the drainage pump for further concentration.
Description
Technical Field
The invention belongs to the technical field of water treatment, and particularly relates to a cold rolling acid wastewater advanced treatment method.
Background
The steel industry is a high-energy-consumption, high-resource and high-pollution industry, and the water resource consumption of the steel industry is huge and accounts for about 14 percent of the water consumption of the national industry.
The national development and improvement committee of 7 months in 2005 issued "iron and steel industry development policy", put forward higher targets and more specific requirements for the development of circular economy, energy and resource conservation and sustainable development road of the iron and steel industry, and under the condition of global resource shortage, low energy consumption, low pollution and low emission become the needs of social development.
The unit water consumption of the steel enterprises in China is still higher than the level of the advanced steel enterprises in China, so that the new water consumption per ton of steel of the steel enterprises is reduced, the water recycling rate of the steel enterprises is improved, and the comprehensive treatment and recycling of the wastewater of the steel enterprises are enhanced, which is one of the keys for realizing the sustainable development of the steel enterprises in China.
Pickling is one of the indispensable processes in cold rolling plants. In the process production process, the scale on the surface of the steel is removed by adopting an acid pickling process for cold-rolled steel, and the surface of the steel is washed by pure water after acid pickling so as to clean the residual acid liquor on the surface of the steel. Therefore, pickling waste liquid and acidic rinsing water are generated, and most of waste acid in the pickling process is returned to an acid regeneration system for regeneration and then is recycled; the rinsing wastewater can not be regenerated by acid due to too low acid concentration and can only be discharged.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is that the invention firstly provides a complete technical scheme for simultaneously removing calcium ions and COD in the acidic wastewater, and the problem that the acidic wastewater pollutes the environment is systematically solved, so the invention belongs to a steel green environment-friendly production process system.
The technical scheme of the invention is as follows: a treatment method for simultaneously removing calcium ions and COD in acidic wastewater comprises the following steps:
a. cold rolling acid wastewater enters a neutralization tank, and strong alkali solution is added into the neutralization tank for neutralization; after passing through the neutralization tank, the pH value of the cold rolling acid wastewater is 6.8-8.1;
b. then, cold rolling acid wastewater enters a mixing and precipitating tank through a primary lift pump, and a stirrer is arranged at the front part of the mixing and precipitating tank and is uniformly stirred; adding 600-810 mg/L sodium carbonate solution into the front part of the mixing and precipitating tank, and fully mixing the sodium carbonate solution and the cold rolling acid wastewater through a stirrer; the rear part of the mixing tank is mainly an inclined plate precipitation zone, the precipitation time is 30-45 min, and sodium carbonate and calcium ions form calcium carbonate precipitation;
c. after passing through the mixing sedimentation tank, the acidic wastewater enters a ceramic microfiltration system through a secondary lift pump, and a modified ceramic microfiltration membrane is placed in the ceramic microfiltration system; the pressure of the microfiltration pressure pump is 0.2-0.8 MPa, the aperture of the modified ceramic microfiltration membrane is 500-800 nm, and the membrane area is 0.178m2～0.246m2；
d. The cold rolling acid wastewater obtained in the step enters a modified diatomite adsorption tower through a three-stage lift pump; modified diatomite is filled in the modified diatomite adsorption tower, and the modified diatomite accounts for 85-90% of the volume of the whole modified diatomite adsorption tower; the retention time of the cold rolling acidic wastewater in the modified diatomite adsorption tower is 25-45 min; and the obtained cold rolling acid wastewater enters a subsequent process.
The water quality characteristics of the cold rolling acid wastewater before treatment are that the pH is 0.2-1.5, the calcium ion is 123-345 mg/L, and the COD is 45-67 mg/L.
And b, after the step b, passing through a mixed sedimentation tank, wherein calcium ions in the cold rolling acid wastewater are 23-67 mg/L, and COD is 35-59 mg/L. However, suspended matters in the effluent of the acid wastewater mixing and settling tank are 54-178 mg/L, and the suspended matters are removed by a subsequent ceramic microfiltration process;
and c, after passing through a ceramic microfiltration system, the suspended matters in the cold-rolled acidic wastewater are 5-12 mg/L, the calcium ions are 15-32 mg/L, and the COD is 24-45 mg/L.
According to the treatment method for simultaneously removing calcium ions and COD in the acidic wastewater, the strong base in the step a is preferably selected from one of sodium hydroxide or potassium hydroxide; the mass concentration of the strong alkali solution is 5-37%.
Preferably, in the step a, the cold rolling acid wastewater enters a neutralization pond through a water inlet pump. The mass concentration of the strong alkali solution is 11-17%.
According to the treatment method for simultaneously removing calcium ions and COD in the acidic wastewater, the residence time of the neutralization pond in the step a is preferably 10-14 min.
According to the treatment method for simultaneously removing calcium ions and COD in the acidic wastewater, the stirring speed in the step b is preferably 75-85 r/min.
According to the treatment method for simultaneously removing calcium ions and COD in the acidic wastewater, the modified ceramic microfiltration membrane in the step c is preferably prepared by the following steps:
1) selecting alpha-Al with the average grain diameter of 25-45 mu m2O3Selecting calcium carbonate with the average particle size of 20-40 mu m and active coke powder with the average particle size of 20-40 mu m;
2)α-Al2O3mixing calcium carbonate and active coke powder according to the mass ratio of 70-85: 5-15, and grinding to form mixed powder;
3) mixing and grinding the mixed powder and the high-alumina powder according to the mass ratio of 1: 1.6-1.9 to obtain superfine diatomite mixed powder;
4) mixing polyethyleneimine and glycerol according to the mass ratio of 0.5-1:1-3 to form a mixed solution, mixing superfine diatomite mixed powder and the mixed solution according to the solid-to-liquid ratio of 3-5: 1, and fully kneading to obtain a pug; mixing the pug, putting the pug into a vacuum extruder, and performing extrusion molding to obtain a wet blank of the tubular support body;
5) and (3) putting the tubular support body wet blank into a heating furnace, heating the heating furnace to 1270-1340 ℃ at the speed of 2-4 ℃/min, keeping the temperature for 45-90 min, and then cooling to room temperature to form the modified ceramic microfiltration membrane.
The modified ceramic microfiltration membrane is prepared according to the water quality of the acidic wastewater.
The porosity of the modified ceramic microfiltration membrane support body is 35.7-43.2%, the three-point bending strength is 23.3-34.7 MPa, and the pure water flux is 45-72 m3/(m2·h·MPa)。
The mixing in the step 4) is a process for mixing raw rubber or plasticated raw rubber and a compounding agent into mixed rubber by a rubber mixing mill, and is the most important production process for rubber processing. Essentially, the process of uniformly dispersing the compounding agent in the raw rubber is realized, the granular compounding agent is in a dispersed phase, and the raw rubber is in a continuous phase.
Further, the grinding in the step 2) is grinding and mixing for 30-50 min on a ball mill; and 3) grinding and mixing the materials on a ball mill for 10-15 h.
Preferably, the mixture obtained in the step 3) is sieved by a sieve of 20-30 meshes.
Further, the alumina content of the high-alumina powder in the step 3) is 45-65%;
further, the wet blank of the tubular support body in the step 4) is 170-190 mm in length, 8-12mm in outer diameter and 4-8mm in inner diameter.
The high-alumina powder is powder with higher alumina content, and the refractory property of the porcelain can be improved by increasing the alumina content. The raw materials for producing the high-alumina powder include silica, kyanite, mullite, diaspore, bauxite, corundum and the like. The high-alumina powder can be directly ground from a raw material containing alumina, and can also be a finished raw material containing high-alumina, such as high-alumina porcelain ground powder.
According to the treatment method for simultaneously removing calcium ions and COD in the acidic wastewater, preferably, the modified diatomite prepared in the step d is prepared by the following steps:
1) preparing a sodium sulfate solution with the concentration of 3.5-6.7 mol/L, then adding 2.3-7.5 mg of glycidyl methacrylate into each liter of solution, and uniformly stirring to form a mixed solution;
2) selecting diatomite with the particle size of 2-10 mm, immersing the diatomite into the mixed solution according to the solid-to-liquid ratio of 1: 5-8, soaking the diatomite in the mixed solution for 3-9 h, filtering the diatomite, heating and drying the diatomite for 3-4 h, cooling the diatomite, putting the diatomite into a heating device, heating the heating device to 330-360 ℃ at the speed of 6-9 ℃/min, keeping the temperature for 2-4 h, and cooling the diatomite to form the modified diatomite.
The calcium ion exchange capacity of the modified diatomite is 13-21 mg/g, and the COD adsorption saturation amount is 18-34 mg/g.
The modified diatomite is prepared according to the characteristics of the cold-rolled acidic wastewater, and calcium ions and COD in the cold-rolled acidic wastewater are synchronously removed.
Further, the stirring speed of the step 1) is 60-80 revolutions per minute; stirring for 15-30 min;
step 2) heating and drying are carried out in a forced air drying box; the heating temperature is 100-110 ℃. The heating device of step 2) is preferably a muffle furnace.
The invention also provides a treatment system for implementing the method, which comprises a water inlet pump, wherein the water inlet pump is connected with the neutralization tank; the neutralization tank is connected with the mixed sedimentation tank through a primary lift pump, and the mixed sedimentation tank is connected with the ceramic microfiltration system through a secondary lift pump; the ceramic microfiltration system is connected with the modified diatomite adsorption tower through a three-stage lift pump; the outlet of the modified diatomite adsorption tower is connected with a drainage pump;
the front part of the mixing and settling tank is provided with a stirrer, and the rear part of the mixing tank is mainly an inclined plate settling zone;
a modified ceramic microfiltration membrane is arranged in the ceramic microfiltration system; the modified diatomite adsorption tower is provided with modified diatomite.
The invention has the beneficial effects that:
the pH value of the treated cold rolling acid wastewater is 7.1-8.6, the calcium ion is 3-9 mg/L, and the COD is 13-25 mg/L. The cold rolling acid wastewater can be discharged through a drainage pump, and can also enter a high-pressure reverse osmosis or electrodialysis system through the drainage pump for further concentration.
Drawings
FIG. 1 is a schematic diagram of a cold rolling acidic wastewater treatment process system.
In the figure, a water inlet pump 1, a neutralization tank 2, a primary lifting pump 3, a mixed sedimentation tank 4, a secondary lifting pump 5, a ceramic microfiltration system 6, a modified ceramic microfiltration membrane 7, a tertiary lifting pump 8, a modified diatomite adsorption tower 9, modified diatomite 10 and a drainage pump 11.
Detailed Description
Example 1
A cold rolling acidic wastewater treatment process comprises a water inlet pump, a neutralization tank, a primary lift pump, a mixed sedimentation tank, a secondary lift pump, a ceramic microfiltration system, a modified ceramic microfiltration membrane, a tertiary lift pump, a modified diatomite adsorption tower, modified diatomite and a drainage pump (shown in figure 1).
The cold rolling acid wastewater has the water quality characteristics that the pH is 0.6, the calcium ion is 225mg/L, and the COD is 55 mg/L.
And the cold rolling acid wastewater enters a neutralization pond through a water inlet pump. And adding a sodium hydroxide solution with the mass ratio of 14% into the neutralization tank. The residence time of the neutralization pond was 12 min. After passing through the neutralization tank, the pH value of the cold rolling acid wastewater is 7.6.
And then, cold rolling acid wastewater enters a mixing and precipitating tank through a primary lifting pump, a stirrer is arranged at the front part of the mixing and precipitating tank, and the stirring speed is 80 r/min. 780mg/L of sodium carbonate solution is added into the front part of the mixing and precipitating tank, and the sodium carbonate solution and the acidic wastewater are fully mixed through a stirrer. The rear part of the mixing tank is mainly an inclined plate sedimentation area, the sedimentation time is 40min, and sodium carbonate and calcium ions form calcium carbonate sediment. After passing through the mixed sedimentation tank, the calcium ion content of the cold rolling acid wastewater is 45mg/L, and the COD is 47 mg/L. However, the suspended matter of the effluent of the acid wastewater mixing and settling tank is between 123mg/L, and a subsequent ceramic microfiltration process is needed to remove the suspended matter.
By mixingAnd after the sedimentation tank, the acidic wastewater enters a ceramic microfiltration system through a secondary lift pump, and a modified ceramic microfiltration membrane is placed in the ceramic microfiltration system. The pressure of the microfiltration pressure pump is 0.6MPa, the aperture of the modified ceramic microfiltration membrane is 600nm, and the membrane area is 0.178m2。
The modified ceramic microfiltration membrane is prepared according to the water quality of the acidic wastewater. The preparation process of the ceramic membrane is as follows: 1) selecting alpha-Al with the average grain diameter of 35 mu m2O3Selecting calcium carbonate and active coke powder with the average grain diameter of 30 mu m; 2) alpha-Al2O3Mixing calcium carbonate and active coke powder according to the mass ratio of 75:8:6, and mixing for 45min on a ball mill to form mixed powder; 3) mixing the mixed powder with high-alumina powder (the content of alumina is 50%) according to the mass ratio of 1:1.8, then mixing in a ball mill for 12 hours, and sieving with a 25-mesh sieve after mixing to obtain superfine diatomite mixed powder; 4) mixing polyethyleneimine and glycerol according to the mass ratio of 1:2 to form a mixed solution, mixing superfine diatomite mixed powder and the mixed solution according to the solid-to-liquid ratio of 4:1, and fully kneading to obtain pug; the pug is mixed and then placed in a vacuum extruder, and a wet blank of the tubular support body with the length of 180mm, the outer diameter of 10mm and the inner diameter of 6mm is obtained through extrusion molding. 5) And (3) putting the tubular support body wet blank into a heating furnace, heating the heating furnace to 1290 ℃ at the speed of 3 ℃/min, keeping the temperature for 80min, and then cooling to room temperature to form the modified ceramic microfiltration membrane. The porosity of the modified ceramic microfiltration membrane support body is 38.9 percent, the three-point bending strength is 31.2MPa, and the pure water flux is 56m3/(m2·h·MPa)。
After passing through a ceramic microfiltration system, the suspended matters in the cold-rolled acidic wastewater are 10mg/L, the calcium ions are 24mg/L, and the COD is 33 mg/L.
And then, cold rolling acid wastewater enters a modified diatomite adsorption tower through a three-stage lift pump. Modified diatomite is filled in the modified diatomite adsorption tower, and the modified diatomite accounts for 90% of the volume of the whole modified diatomite adsorption tower. The retention time of the cold rolling acidic wastewater in the modified diatomite adsorption tower is 40 min.
The modified diatomite is prepared according to the characteristics of the cold-rolled acidic wastewater, and calcium ions and COD in the cold-rolled acidic wastewater are synchronously removed. The preparation method comprises 1) selecting diatomaceous earth with particle diameter of 8mm, preparing sodium sulfate solution with concentration of 4.2mol/L, adding 4.8mg glycidyl methacrylate into each liter of solution, and stirring at 70 r/min for 25min to obtain mixed solution; 2) and (2) soaking the diatomite into the mixed solution according to the solid-to-liquid ratio of 1:7, soaking for 8h in the mixed solution, filtering the diatomite, drying for 4h in a 105 ℃ blast drying oven, cooling, then placing into a muffle furnace, heating the muffle furnace to 345 ℃ at the speed of 8 ℃/min, keeping the temperature for 3h, and cooling to obtain the modified diatomite. The calcium ion exchange capacity of the modified diatomite is 17mg/g, and the COD adsorption saturation capacity is 29 mg/g.
And finally discharging the acidic wastewater into a subsequent process through a drainage pump.
The pH value of the treated cold rolling acid wastewater is 7.6, the calcium ion is 6mg/L, and the COD is 16 mg/L.
Example 2:
a cold rolling acidic wastewater treatment process comprises a water inlet pump, a neutralization tank, a primary lift pump, a mixed sedimentation tank, a secondary lift pump, a ceramic microfiltration system, a modified ceramic microfiltration membrane, a tertiary lift pump, a modified diatomite adsorption tower, modified diatomite and a drainage pump.
The cold rolling acid wastewater has the water quality characteristics that the pH is 0.2, the calcium ion is 145mg/L, and the COD is 51 mg/L.
And the cold rolling acid wastewater enters a neutralization pond through a water inlet pump. And adding a sodium hydroxide solution with the mass ratio of 17% into the neutralization tank. The residence time of the neutralization pond was 14 min. After passing through the neutralization tank, the pH value of the cold rolling acid wastewater is 8.0.
And then, cold rolling acid wastewater enters a mixing and precipitating tank through a primary lifting pump, a stirrer is arranged at the front part of the mixing and precipitating tank, and the stirring speed is 85 revolutions per minute. 810mg/L of sodium carbonate solution is added at the front part of the mixing and precipitating tank, and the sodium carbonate solution and the acidic wastewater are fully mixed by a stirrer. The rear part of the mixing tank is mainly an inclined plate sedimentation area, the sedimentation time is 45min, and sodium carbonate and calcium ions form calcium carbonate sediment. After passing through the mixed sedimentation tank, the calcium ion content of the cold rolling acid wastewater is 26mg/L, and the COD is 37 mg/L. However, the suspended matter of the effluent of the acid wastewater mixing and settling tank is between 168mg/L, and a subsequent ceramic microfiltration process is needed to remove the suspended matter.
After passing through the mixing sedimentation tank, the acidic wastewater enters a ceramic microfiltration system through a secondary lift pump, and a modified ceramic microfiltration membrane is placed in the ceramic microfiltration system. The pressure of the microfiltration pressure pump is 0.2MPa, the pore diameter of the modified ceramic microfiltration membrane is 550nm, and the membrane area is 0.198m2。
The modified ceramic microfiltration membrane is prepared according to the water quality of the acidic wastewater. The preparation process of the ceramic membrane is as follows: 1) selecting alpha-Al with the average grain diameter of 25 mu m2O3Selecting calcium carbonate and active coke powder with the average grain diameter of 37 mu m; 2) alpha-Al2O3Mixing calcium carbonate and active coke powder according to the mass ratio of 85:12.5:7, and mixing for 45min on a ball mill to form mixed powder; 3) mixing the mixed powder with high-alumina powder (the content of alumina is 53%) according to the mass ratio of 1:1.9, then mixing in a ball mill for 12 hours, and sieving with a 30-mesh sieve after mixing to obtain superfine diatomite mixed powder; 4) mixing polyethyleneimine and glycerol according to the mass ratio of 1:2 to form a mixed solution, mixing superfine diatomite mixed powder and the mixed solution according to the solid-to-liquid ratio of 5:1, and fully kneading to obtain pug; the pug is mixed and then placed in a vacuum extruder, and a wet blank of the tubular support body with the length of 180mm, the outer diameter of 10mm and the inner diameter of 6mm is obtained through extrusion molding. 5) And (3) putting the tubular support body wet blank into a heating furnace, heating the heating furnace to 1340 ℃ at the speed of 4 ℃/min, keeping the temperature for 90min, and then cooling to room temperature to form the modified ceramic microfiltration membrane. The porosity of the modified ceramic microfiltration membrane support body is 41.1 percent, the three-point bending strength is 29.8MPa, and the pure water flux is 49m3/(m2·h·MPa)。
After passing through a ceramic microfiltration system, the suspended matters in the cold-rolled acidic wastewater are 7mg/L, the calcium ions are 17mg/L, and the COD is 35 mg/L.
And then, cold rolling acid wastewater enters a modified diatomite adsorption tower through a three-stage lift pump. Modified diatomite is filled in the modified diatomite adsorption tower, and the modified diatomite accounts for 85% of the volume of the whole modified diatomite adsorption tower. The retention time of the cold rolling acidic wastewater in the modified diatomite adsorption tower is 25 min.
The modified diatomite is prepared according to the characteristics of the cold-rolled acidic wastewater, and calcium ions and COD in the cold-rolled acidic wastewater are synchronously removed. The preparation method comprises 1) selecting diatomaceous earth with particle size of 6mm, preparing sodium sulfate solution with concentration of 4.6mol/L, adding 7.1mg glycidyl methacrylate into each liter of solution, and stirring at 70 r/min for 25min to obtain mixed solution; 2) and (2) soaking the diatomite into the mixed solution according to the solid-to-liquid ratio of 1:7, soaking for 7h in the mixed solution, filtering the diatomite, drying for 3h in a 105 ℃ blast drying oven, cooling, then placing into a muffle furnace, heating the muffle furnace to 345 ℃ at the speed of 9 ℃/min, keeping the temperature for 2h, and cooling to obtain the modified diatomite. The calcium ion exchange capacity of the modified diatomite is 15mg/g, and the COD adsorption saturation capacity is 31 mg/g.
And finally discharging the acidic wastewater into a subsequent process through a drainage pump.
The pH value of the treated cold rolling acid wastewater is 8.0, the calcium ion is 8mg/L, and the COD is 16 mg/L. The cold rolling acid wastewater can be discharged through a drainage pump, and can also enter a high-pressure reverse osmosis or electrodialysis system through the drainage pump for further concentration.
Example 3
A cold rolling acidic wastewater treatment process comprises a water inlet pump, a neutralization tank, a primary lift pump, a mixed sedimentation tank, a secondary lift pump, a ceramic microfiltration system, a modified ceramic microfiltration membrane, a tertiary lift pump, a modified diatomite adsorption tower, modified diatomite and a drainage pump.
The cold rolling acid wastewater has the water quality characteristics that the pH is 0.5, the calcium ion is 205mg/L, and the COD is 55 mg/L.
And the cold rolling acid wastewater enters a neutralization pond through a water inlet pump. Adding a potassium hydroxide solution with the mass ratio of 20% into the neutralization tank. The residence time of the neutralization pond was 10 min. After passing through the neutralization tank, the pH value of the cold rolling acid wastewater is 8.0.
And then, cold rolling acid wastewater enters a mixing and precipitating tank through a primary lifting pump, a stirrer is arranged at the front part of the mixing and precipitating tank, and the stirring speed is 85 revolutions per minute. 650mg/L of sodium carbonate solution is added into the front part of the mixing and precipitating tank, and the sodium carbonate solution and the acidic wastewater are fully mixed by a stirrer. The rear part of the mixing tank is mainly an inclined plate sedimentation area, the sedimentation time is 32min, and sodium carbonate and calcium ions form calcium carbonate sediment. After passing through the mixed sedimentation tank, the calcium ion content of the cold rolling acid wastewater is 38mg/L, and the COD is 40 mg/L. . However, the suspended matter of the effluent of the acid wastewater mixing and settling tank is between 108mg/L, and a subsequent ceramic microfiltration process is needed to remove the suspended matter.
After passing through the mixing sedimentation tank, the acidic wastewater enters a ceramic microfiltration system through a secondary lift pump, and a modified ceramic microfiltration membrane is placed in the ceramic microfiltration system. The pressure of the microfiltration pressure pump is 0.7MPa, the pore diameter of the modified ceramic microfiltration membrane is 750nm, and the membrane area is 0.226m2。
The modified ceramic microfiltration membrane is prepared according to the water quality of the acidic wastewater. The preparation process of the ceramic membrane is as follows: 1) selecting alpha-Al with the average grain diameter of 40 mu m2O3Selecting calcium carbonate and active coke powder with the average grain diameter of 25 mu m; 2) alpha-Al2O3Mixing calcium carbonate and active coke powder according to a mass ratio of 80:10:12, and mixing for 30min on a ball mill to form mixed powder; 3) mixing the mixed powder with high-alumina powder (the content of alumina is 52%) according to the mass ratio of 1:1.7, then mixing for 14 hours in a ball mill, and sieving with a 30-mesh sieve after mixing to obtain superfine diatomite mixed powder; 4) mixing polyethyleneimine and glycerol according to the mass ratio of 1:3 to form a mixed solution, mixing superfine diatomite mixed powder and the mixed solution according to the solid-to-liquid ratio of 3:1, and fully kneading to obtain pug; the pug is mixed and then placed in a vacuum extruder, and a tubular support body wet blank with the length of 180mm, the outer diameter of 10mm and the inner diameter of 8mm is obtained through extrusion molding. 5) And (3) putting the tubular support body wet blank into a heating furnace, heating the heating furnace to 1320 ℃ at the speed of 4 ℃/min, keeping the temperature for 60min, and then cooling to room temperature to form the modified ceramic microfiltration membrane. The porosity of the modified ceramic microfiltration membrane support body is 42.5 percent, the three-point bending strength is 25.9MPa, and the pure water flux is 62m3/(m2·h·MPa)。
After passing through a ceramic microfiltration system, the suspended matters in the cold-rolled acidic wastewater are 6mg/L, the calcium ions are 20mg/L, and the COD is 30 mg/L.
And then, cold rolling acid wastewater enters a modified diatomite adsorption tower through a three-stage lift pump. Modified diatomite is filled in the modified diatomite adsorption tower, and the modified diatomite accounts for 85% of the volume of the whole modified diatomite adsorption tower. The retention time of the cold rolling acidic wastewater in the modified diatomite adsorption tower is 30 min.
The modified diatomite is prepared according to the characteristics of the cold-rolled acidic wastewater, and calcium ions and COD in the cold-rolled acidic wastewater are synchronously removed. The preparation method comprises 1) selecting diatomaceous earth with particle size of 6mm, preparing sodium sulfate solution with concentration of 5.6mol/L, adding 5.2mg glycidyl methacrylate into each liter of solution, and stirring at 70 r/min for 25min to obtain mixed solution; 2) and (2) soaking the diatomite into the mixed solution according to the solid-to-liquid ratio of 1:5, soaking for 4h in the mixed solution, filtering the diatomite, drying for 3.5h in a 105 ℃ blast drying oven, cooling, then placing into a muffle furnace, heating the muffle furnace to 352 ℃ at the speed of 6 ℃/min, keeping the temperature for 4h, and cooling to obtain the modified diatomite. The calcium ion exchange capacity of the modified diatomite is 20mg/g, and the COD adsorption saturation capacity is 21 mg/g.
And finally discharging the acidic wastewater into a subsequent process through a drainage pump.
The pH value of the treated cold rolling acid wastewater is 8.1, the calcium ion is 7mg/L, and the COD is 20 mg/L. The cold rolling acid wastewater can be discharged through a drainage pump, and can also enter a high-pressure reverse osmosis or electrodialysis system through the drainage pump for further concentration.
In conclusion, the invention provides a process for simultaneously cold-rolling calcium ions and COD in acidic wastewater for the first time, and the problem of environmental pollution caused by the cold-rolling acidic wastewater is solved systematically, so the invention belongs to a steel green environment-friendly production process system.
Of course, those skilled in the art should recognize that the above-described embodiments are illustrative only, and not limiting, and that changes and modifications can be made within the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A treatment method for simultaneously removing calcium ions and COD in acidic wastewater is characterized in that: the method comprises the following steps:
a. cold rolling acid wastewater enters a neutralization tank, and strong alkali solution is added into the neutralization tank for neutralization; after passing through the neutralization tank, the pH value of the cold rolling acid wastewater is 6.8-8.1;
b. then, cold rolling acid wastewater enters a mixing and precipitating tank through a primary lift pump, and a stirrer is arranged at the front part of the mixing and precipitating tank and is uniformly stirred; adding 600-810 mg/L sodium carbonate solution into the front part of the mixing and precipitating tank, and fully mixing the sodium carbonate solution and the cold rolling acid wastewater through a stirrer; the rear part of the mixing tank is mainly an inclined plate precipitation zone, the precipitation time is 30-45 min, and sodium carbonate and calcium ions form calcium carbonate precipitation;
c. after passing through the mixing sedimentation tank, the acidic wastewater enters a ceramic microfiltration system through a secondary lift pump, and a modified ceramic microfiltration membrane is placed in the ceramic microfiltration system; the pressure of the microfiltration pressure pump is 0.2-0.8 MPa, the aperture of the modified ceramic microfiltration membrane is 500-800 nm, and the membrane area is 0.178m2～0.246m2；
d. The cold rolling acid wastewater obtained in the step enters a modified diatomite adsorption tower through a three-stage lift pump; modified diatomite is filled in the modified diatomite adsorption tower, and the modified diatomite accounts for 85-90% of the volume of the whole modified diatomite adsorption tower; the retention time of the cold rolling acidic wastewater in the modified diatomite adsorption tower is 25-45 min; and the obtained cold rolling acid wastewater enters a subsequent process.
2. The treatment method for simultaneously removing calcium ions and COD in acidic wastewater according to claim 1, characterized in that: the strong base in the step a is selected from one of sodium hydroxide or potassium hydroxide; the mass concentration of the strong alkali solution is 5-37%.
3. The treatment method for simultaneously removing calcium ions and COD in acidic wastewater according to claim 1, characterized in that: in the step a, the retention time of the neutralization tank is 10-14 min.
4. The treatment method for simultaneously removing calcium ions and COD in acidic wastewater according to claim 1, characterized in that: the stirring speed of the step b is 75-85 revolutions per minute; and b, after the step b passes through a mixed sedimentation tank, the calcium ion content of the cold rolling acid wastewater is 23-67 mg/L, and the COD content is 35-59 mg/L.
5. The treatment method for simultaneously removing calcium ions and COD in acidic wastewater according to claim 1, characterized in that:
the preparation process of the modified ceramic microfiltration membrane in the step c is as follows:
1) selecting alpha-Al with the average grain diameter of 25-45 mu m2O3Selecting calcium carbonate with the average particle size of 20-40 mu m and active coke powder with the average particle size of 20-40 mu m;
2)α-Al2O3mixing calcium carbonate and active coke powder according to the mass ratio of 70-85: 5-15, and grinding to form mixed powder;
3) mixing and grinding the mixed powder and the high-alumina powder according to the mass ratio of 1: 1.6-1.9 to obtain superfine diatomite mixed powder;
4) mixing polyethyleneimine and glycerol according to the mass ratio of 0.5-1:1-3 to form a mixed solution, mixing superfine diatomite mixed powder and the mixed solution according to the solid-to-liquid ratio of 3-5: 1, and fully kneading to obtain a pug; mixing the pug, putting the pug into a vacuum extruder, and performing extrusion molding to obtain a wet blank of the tubular support body;
5) and (3) putting the tubular support body wet blank into a heating furnace, heating the heating furnace to 1270-1340 ℃ at the speed of 2-4 ℃/min, keeping the temperature for 45-90 min, and then cooling to room temperature to form the modified ceramic microfiltration membrane.
6. The treatment method for simultaneously removing calcium ions and COD in the acidic wastewater according to claim 5, is characterized in that: the grinding in the step 2) is carried out on a ball mill for 30-50 min; and 3) grinding and mixing the materials on a ball mill for 10-15 h.
7. The treatment method for simultaneously removing calcium ions and COD in the acidic wastewater according to claim 5, is characterized in that: and 4) the wet blank of the tubular support body in the step 4) is 170-190 mm in length, 8-12mm in outer diameter and 4-8mm in inner diameter.
8. The treatment method for simultaneously removing calcium ions and COD in acidic wastewater according to claim 1, characterized in that: the preparation method of the modified diatomite in the step d is as follows:
1) preparing a sodium sulfate solution with the concentration of 3.5-6.7 mol/L, then adding 2.3-7.5 mg of glycidyl methacrylate into each liter of solution, and uniformly stirring to form a mixed solution;
2) selecting diatomite with the particle size of 2-10 mm, immersing the diatomite into the mixed solution according to the solid-to-liquid ratio of 1: 5-8, soaking the diatomite in the mixed solution for 3-9 h, filtering the diatomite, heating and drying the diatomite for 3-4 h, cooling the diatomite, putting the diatomite into a heating device, heating the heating device to 330-360 ℃ at the speed of 6-9 ℃/min, keeping the temperature for 2-4 h, and cooling the diatomite to form the modified diatomite.
9. The method for simultaneously removing calcium ions and COD in acidic wastewater according to claim 8, characterized in that: step 1), the stirring speed is 60-80 r/min; stirring for 15-30 min;
step 2) heating and drying are carried out in a forced air drying box; the heating temperature is 100-110 ℃.
10. A treatment system for carrying out the method of claim 1, comprising a feed pump, wherein: the water inlet pump is connected with the neutralization tank; the neutralization tank is connected with the mixed sedimentation tank through a primary lift pump, and the mixed sedimentation tank is connected with the ceramic microfiltration system through a secondary lift pump; the ceramic microfiltration system is connected with the modified diatomite adsorption tower through a three-stage lift pump; the outlet of the modified diatomite adsorption tower is connected with a drainage pump;
the front part of the mixing and settling tank is provided with a stirrer, and the rear part of the mixing tank is mainly an inclined plate settling zone;
a modified ceramic microfiltration membrane is arranged in the ceramic microfiltration system; the modified diatomite adsorption tower is provided with modified diatomite.
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