CN113213665A - Thermal power plant desulfurization wastewater clarification process based on silicon carbide film ultrafiltration technology - Google Patents
Thermal power plant desulfurization wastewater clarification process based on silicon carbide film ultrafiltration technology Download PDFInfo
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Abstract
The invention discloses a thermal power plant desulfurization wastewater clarification process based on a silicon carbide film ultrafiltration technology, which comprises the steps of carrying out micro-flocculation treatment on desulfurization wastewater to obtain a pretreatment solution; filtering the pretreatment solution by adopting a silicon carbide ceramic membrane to obtain a filtered clear solution and a concentrated solution, wherein the clear solution is recycled or subjected to advanced treatment, and the concentrated solution is returned to a desulfurization system; the invention can effectively decontaminate and reduce turbidity of the desulfurization wastewater, and the turbidity of the filtered clear liquid can be controlled within 1.0NTU, thereby being beneficial to realizing resource utilization of the desulfurization wastewater, secondarily utilizing the filtered clear liquid and reducing the consumption of industrial water; the concentrated solution is filtered and returned to the desulfurization system, sludge does not need to be discharged, sludge generated and treated in water treatment is avoided, and the investment, the running cost and the environmental protection risk of a power plant are also obviously reduced while the environment is prevented from being polluted by desulfurization wastewater.
Description
Technical Field
The invention belongs to the technical field of water treatment of a thermal power plant, and relates to a thermal power plant desulfurization wastewater clarification process based on a silicon carbide film ultrafiltration technology.
Background
China is a country with coal as a main energy source, and coal-fired power generation is one of the most important ways for coal utilization in China; among the air pollutants discharged by coal-fired thermal power generating units, SO2 is a major pollutant to be controlled, and has a great environmental hazard. At present, the existing flue gas desulfurization technologies include wet desulfurization, dry desulfurization and the like, wherein the wet desulfurization technology is most widely applied. However, in the operation process of wet flue gas desulfurization, desulfurization wastewater containing a large amount of gypsum slurry and salt, and a small amount of heavy metal ions such as carbon black, tar, mercury, lead, nickel, arsenic, chromium and the like can be generated, and the direct discharge has great harm to the environment.
With the increasingly prominent environmental protection problems and the increasingly stricter emission standards, the advanced treatment and recycling of the desulfurization wastewater of the thermal power plant are more and more emphasized. In 2015, the environmental protection laws of the people's republic of China and the action plans of water pollution prevention and control (ten items of water) integrally improve the requirements of wastewater treatment. Ministry of environmental protection, "feasible technical guidelines for pollution control in thermal power plants" (HJ 2301-2017): the desulfurized wastewater is preferably recycled after being treated by processes such as lime treatment, coagulation, clarification, neutralization and the like. The treatment processes such as flue gas evaporation drying or evaporation crystallization are encouraged to realize that the desulfurization wastewater is not discharged outside. However, the conventional treatment processes such as flocculation precipitation, clarification and separation and the like are adopted, so that the cost of the medicament is high, the flow is long, the occupied area of equipment is large, the manpower is relied on, and the automation degree is low; the existing thermal method process systems such as evaporation crystallization and the like for concentrating, solidifying and dissolving salts are complex, mainly use the evaporation of hot flue gas at the tail part of a boiler, depend on the waste heat of the flue gas of the boiler and have higher energy consumption.
At present, the mainstream desulfurization wastewater treatment processes have the defects of high construction and operation cost, easy precipitation and blockage of slurry, large maintenance amount and the like, and have low process reliability. The reason is that the desulfurization wastewater mainly comprises a large amount of supersaturated sulfite, sulfate, suspended matters and trace heavy metals, and the ions are mixed together, so that the desulfurization wastewater has the characteristics of high suspended matters, high scaling tendency, mixed solution of various ions, large component change and the like, and can be continuously subjected to advanced treatment or recycling after being subjected to proper pretreatment and clarification. Therefore, how to solve the problem that the clarification process of the desulfurization wastewater becomes the problem of restricting the comprehensive utilization of the desulfurization wastewater needs to be solved urgently.
Disclosure of Invention
The invention aims to provide a thermal power plant desulfurization wastewater clarification process based on silicon carbide membrane ultrafiltration, which realizes resource utilization of desulfurization wastewater, avoids environmental pollution caused by desulfurization wastewater, and also obviously reduces investment and operation cost of thermal power plant desulfurization wastewater.
The silicon carbide film ultrafiltration technology has some incomparable advantages compared with the solid-liquid separation of traditional plate-and-frame filter presses, centrifuges, diatomite, polymer films and the like: the cleaning and sanitation, energy conservation and environmental protection are realized; high temperature resistance, high mechanical strength and good wear resistance; the pore size distribution is narrow, and the separation precision is extremely high; easy to clean, can be used for on-line medicament or backwashing: the chemical stability is extremely strong, can resist acid-base, oxidation, is suitable for pH value 0-14, the silicon carbide film adopts the internal pressure cross flow type to filter, the velocity of flow of feed liquid in the film tube can reach several meters per second, can be used for the treatment of high solid content waste water, and does not need to add chemical agent to the waste water, the floor area of the apparatus is small, the degree of automation is high.
The invention adopts the technical scheme that the thermal power plant desulfurization wastewater clarification process based on the silicon carbide film ultrafiltration technology comprises a desulfurization system, a primary sedimentation tank, an adjusting tank, a micro-flocculation reaction tank and a silicon carbide film filtering device; the desulfurization system, the primary sedimentation tank, the regulating tank, the micro-flocculation reaction tank and the silicon carbide film filtering device are sequentially connected through a pump and a pipeline;
the method is implemented by the following steps:
step 1, conveying the wastewater generated by a desulfurization system to a primary sedimentation tank through a wastewater pump and a pipeline, completing primary sedimentation separation in the primary sedimentation tank, forming thick slurry by sedimentation at the bottom of the primary sedimentation tank, and producing supernatant at the upper part;
step 2, enabling the supernatant of the primary sedimentation tank to enter an adjusting tank, wherein the adjusting tank is provided with a stirrer, further uniformly stirring the supernatant, and adding a sodium hydroxide solution through a dosing system to adjust the pH value of the desulfurization wastewater;
step 3, enabling the effluent of the adjusting tank to enter a micro flocculation reaction tank, adding a sodium carbonate solution through a dosing system, completing micro flocculation precipitation in the micro flocculation reaction tank, performing flocculation concentration on large particles to obtain thick slurry, discharging the thick slurry at the bottom, and obtaining a pretreatment solution from the effluent of the micro flocculation reaction tank, wherein the mass concentration is not more than 4%;
step 4, conveying the pretreatment liquid to a silicon carbide film filtering device through a silicon carbide film circulating pump and a pipeline for filtering treatment to obtain a filtered clear liquid and a concentrated liquid;
and 5, filtering clear liquid for recycling or entering a desulfurization wastewater zero-discharge system for advanced treatment, and collecting and recycling concentrated solution and concentrated slurry discharged from the primary sedimentation tank and the micro-flocculation reaction tank to the desulfurization system to realize cyclic utilization.
The invention is also characterized in that:
adding a sodium hydroxide solution into the primary sedimentation tank to adjust the pH value of the desulfurization wastewater to 10-11 in the step 2;
adding a sodium carbonate solution into the regulating reservoir in the step 3 to perform micro-flocculation pretreatment to obtain a pretreatment solution; the desulfurization wastewater contains calcium sulfate, and the ratio of the addition amount of sodium carbonate to the solubility of the calcium sulfate is 100-110: 172;
wherein the micro-flocculation reaction time in the step 3 is 5-45 min;
wherein the effective filtering aperture of the silicon carbide film used by the silicon carbide film filtering device in the step 4 is 0.04-0.1 μm;
wherein the transmembrane pressure difference of the silicon carbide film in the step 4 is controlled to be 0.15-0.25 Mpa in the filtering process of the pretreatment liquid, and the flow rate of the film surface is controlled to be 2-3.5 m/s;
wherein the feeding of the silicon carbide membrane filtering device in the step 4 is adjusted by adopting variable flow, and the proportion of clear liquid to concentrated liquid is kept at 2-4: 1;
and 4, periodically backwashing the silicon carbide membrane filter device in the step 4, wherein the backwashing adopts constant-flow constant-pressure flushing, and backwashing water is a filtering clear liquid. The silicon carbide film device is back flushed once every 15-20 minutes for 30 s;
after the flux of the silicon carbide membrane filtering device in the step 4 is less than 50% of the initial flux, a hydrochloric acid solution with the concentration of 2-3% or a sulfamic acid solution with the concentration of 5-8% is needed for chemical cleaning;
wherein, the thick slurry discharged from the bottom of the primary sedimentation tank in the step 2, the thick slurry discharged from the bottom of the micro flocculation reaction tank in the step 3 and the thick liquid generated by the silicon carbide film device in the step 4 are discharged to a special collecting tank and are returned to a desulfurization system through a collecting tank lift pump and a pipeline.
The invention has the beneficial effects that:
1. substances such as suspended matters, colloids, heavy metals, carbon black, tar particles and the like in the desulfurization wastewater are agglomerated by utilizing the micro flocculation effect of sodium hydroxide and sodium carbonate, so that the aim of effectively removing the substances is fulfilled;
2. according to the conditions of high colloid concentration, complex components, small particles and difficult precipitation of the desulfurization wastewater, the silicon carbide film is adopted for filtering, the filtrate is clear and transparent, the turbidity is within 1.0NTU, and the pH value of the filtrate is between 10 and 11, so that the high utilization value is achieved, the filtrate can be reused in other process water systems in a plant area, the consumption of fresh water is reduced, and the recovery of alkali liquor and water is realized;
3. the silicon carbide film has excellent strength, long service life and low construction, operation and maintenance cost;
4. the method is favorable for realizing resource utilization of the desulfurization wastewater, and the thick slurry and the thick liquid generated in the process flow return to a desulfurization system, so that the environmental protection risk caused by disposing solid wastes such as gypsum mud cakes and the like is avoided;
the method and the process can effectively pretreat the desulfurization wastewater, reduce turbidity, achieve resource recovery of the desulfurization wastewater, and obviously reduce the advanced treatment cost of the desulfurization wastewater.
Drawings
FIG. 1 is a schematic flow diagram of a thermal power plant desulfurization wastewater clarification process based on a silicon carbide membrane ultrafiltration technology.
Detailed Description
The present invention will be described in detail with reference to the following embodiments.
The invention provides a thermal power plant desulfurization wastewater clarification process based on a silicon carbide film ultrafiltration technology, which is implemented by the following steps as shown in figure 1:
step 1, conveying the wastewater generated by a desulfurization system to a primary sedimentation tank through a wastewater pump and a pipeline, completing primary sedimentation separation in the primary sedimentation tank, forming thick slurry by sedimentation at the bottom of the primary sedimentation tank, and producing supernatant at the upper part;
step 2, enabling the supernatant of the primary sedimentation tank to enter an adjusting tank, wherein the adjusting tank is provided with a stirrer, the supernatant can be further uniformly stirred, and adding a sodium hydroxide solution through a dosing system to adjust the pH value of the desulfurization wastewater to 10-11;
step 3, enabling the effluent of the adjusting tank to enter a micro-flocculation reaction tank, adding a sodium carbonate solution through a dosing system, and completing micro-flocculation precipitation in the micro-flocculation reaction tank, wherein the micro-flocculation reaction time is 5-45 min, the desulfurization wastewater contains calcium sulfate, the ratio of the addition amount of the sodium carbonate to the solubility of the calcium sulfate is 100-110: 172, large particles are flocculated and concentrated into thick slurry to be discharged at the bottom, and the effluent of the micro-flocculation reaction tank is treated to obtain a pretreatment solution, wherein the mass concentration is not more than 4%;
and 4, conveying the pretreatment liquid to a silicon carbide film filtering device through a silicon carbide film circulating pump and a pipeline for filtering treatment to obtain a filtered clear liquid and a concentrated liquid, wherein the effective filtering aperture of a silicon carbide film used by the silicon carbide film filtering device is 0.04-0.1 mu m, the transmembrane pressure difference of the silicon carbide film in the filtering process of the pretreatment liquid is controlled to be 0.15-0.25 Mpa, the flow rate of the film surface is controlled to be 2-3.5 m/s, the feeding of the silicon carbide film filtering device is regulated by variable flow, and the proportion of the clear liquid to the concentrated liquid is kept to be 2-4: 1, the silicon carbide film filtering device needs to be periodically back flushed by adopting a constant flow and a constant pressure, and the back flushing water is the filtering clear liquid. The silicon carbide film device is back flushed once every 15-20 minutes for 30 s; after the flux of the silicon carbide film filtering device is less than 50% of the initial flux, a 2-3% hydrochloric acid solution or a 5-8% sulfamic acid solution is needed for chemical cleaning;
the thick slurry discharged from the bottom of the primary sedimentation tank in the step 2, the thick slurry discharged from the bottom of the micro flocculation reaction tank in the step 3 and the thick liquid generated by the silicon carbide film device in the step 4 are discharged to a special collecting tank and are returned to a desulfurization system through a collecting tank lifting pump and a pipeline;
and 5, filtering clear liquid for recycling or entering a desulfurization wastewater zero-discharge system for advanced treatment, and collecting and recycling concentrated solution and concentrated slurry discharged from the primary sedimentation tank and the micro-flocculation reaction tank to the desulfurization system to realize cyclic utilization.
The working principle of the silicon carbide film is as follows: the silicon carbide ceramic membrane is formed by adopting a recrystallization technology through high-temperature sintering, the porous supporting layer, the transition layer and the membrane layer are all silicon carbide materials, and the filtering precision is ultrafiltration. The silicon carbide film filtering system is one kind of fluid separating process in cross flow filtering mode, and has high speed treated liquid flowing inside the film pipe, clear penetrating liquid containing small molecular components driven by pressure to penetrate through the dense film layer outwards in the direction perpendicular to the clear penetrating liquid, and turbid concentrated liquid containing large molecular components to be intercepted, so as to realize the clarification, separation, concentration and purification of fluid.
The process method is suitable for the clarification process of the pretreatment of the desulfurization wastewater of the thermal power plant, can effectively decontaminate and reduce the turbidity of the desulfurization wastewater, and the turbidity of the effluent is within 1.0NTU, thereby not only meeting the low-level recycling, but also being more beneficial to the advanced treatment and greatly reducing the load and pressure of an advanced treatment device;
example 1
Adding sodium hydroxide into the desulfurization wastewater containing calcium sulfate to adjust the pH value of the wastewater to 11, adding sodium carbonate, mechanically stirring and uniformly mixing, wherein the ratio of the adding amount of the sodium carbonate to the solubility of the calcium sulfate is 100:172, and entering a micro-flocculation reaction tank for micro-flocculation reaction for 25min to obtain a pretreatment solution; and (3) filtering the pretreatment solution by using a silicon carbide ceramic membrane to obtain a filtered clear solution, wherein the effective filtering aperture of the silicon carbide ceramic membrane is 0.08 mu m, the transmembrane pressure difference of the silicon carbide ceramic membrane is controlled to be 0.20Mpa in the filtering process of the pretreatment solution, and the membrane surface flow rate is controlled to be 2 m/s.
Gather a certain power plant's desulfurization waste water in Hebei, waste water sample index is: yellow turbidity, solid content 3.5 percent and SS concentration 4629 mg/L; the filtrate obtained by treating the desulfurization waste water according to example 1 showed a pH value >10, colorless transparency and a turbidity of 0.3 NTU.
Example 2
Adding sodium hydroxide into the desulfurization wastewater containing calcium sulfate to adjust the pH value of the wastewater to 10.5, adding sodium carbonate, mechanically stirring and uniformly mixing, wherein the ratio of the adding amount of the sodium carbonate to the solubility of the calcium sulfate is 108:172, and entering a micro-flocculation reaction tank for micro-flocculation reaction for 45min to obtain a pretreatment solution; and (3) filtering the pretreatment solution by using a silicon carbide ceramic membrane to obtain a filtered clear solution, wherein the effective filtering aperture of the silicon carbide ceramic membrane is 0.04 mu m, the transmembrane pressure difference of the silicon carbide ceramic membrane is controlled to be 0.25Mpa in the filtering process of the pretreatment solution, and the membrane surface flow rate is controlled to be 2 m/s.
Gather a certain power plant's desulfurization waste water in Hebei, waste water sample index is: yellow turbidity, solid content 4.5% and SS concentration 4983 mg/L. The desulfurization waste water was treated in accordance with the method of example 2 to obtain a clear filtrate having an index of pH >10, colorless and transparent, and a turbidity of 0.5 NTU.
Example 3
Adding sodium hydroxide into the desulfurization wastewater containing calcium sulfate to adjust the pH value of the wastewater to 11, adding sodium carbonate, mechanically stirring and uniformly mixing, wherein the ratio of the adding amount of the sodium carbonate to the solubility of the calcium sulfate is 110:172, and entering a micro-flocculation reaction tank for micro-flocculation reaction for 5min to obtain a pretreatment solution; and (3) filtering the pretreatment solution by using a silicon carbide ceramic membrane to obtain a filtered clear solution, wherein the effective filtering aperture of the silicon carbide ceramic membrane is 0.1 mu m, the transmembrane pressure difference of the silicon carbide ceramic membrane is controlled to be 0.25Mpa in the filtering process of the pretreatment solution, and the membrane surface flow rate is controlled to be 3 m/s.
Gather a certain power plant's desulfurization waste water in Hebei, waste water sample index is: yellow turbidity, solid content 3.5% and SS concentration 5684 mg/L. The filtrate obtained by treating the desulfurization waste water according to example 3 showed a pH value of >10, colorless and transparent, and a turbidity of 0.6 NTU.
Example 4
Adding sodium hydroxide into the desulfurization wastewater containing calcium sulfate to adjust the pH value of the wastewater to 10, adding sodium carbonate, mechanically stirring and uniformly mixing, wherein the ratio of the adding amount of the sodium carbonate to the solubility of the calcium sulfate is 100:172, and allowing the mixture to enter a micro-flocculation reaction tank for micro-flocculation reaction for 20min to obtain a pretreatment solution; and (3) filtering the pretreatment solution by using a silicon carbide ceramic membrane to obtain a filtered clear solution, wherein the effective filtering aperture of the silicon carbide ceramic membrane is 0.04 mu m, the transmembrane pressure difference of the silicon carbide ceramic membrane is controlled to be 0.20Mpa in the filtering process of the pretreatment solution, and the membrane surface flow rate is controlled to be 3.5 m/s.
Gather a certain power plant's desulfurization waste water in Hebei, waste water sample index is: yellow turbidity, 3.5% solids content and an SS concentration of 5689 mg/L. The desulfurization waste water was treated in accordance with the method of example 4 to obtain a clear filtrate having an index of pH >10, colorless and transparent, and a turbidity of 0.3 NTU.
Example 5
Adding sodium hydroxide into the desulfurization wastewater containing calcium sulfate to adjust the pH value of the wastewater to 10.5, adding sodium carbonate, mechanically stirring and uniformly mixing, wherein the ratio of the adding amount of the sodium carbonate to the solubility of the calcium sulfate is 105:172, and entering a micro-flocculation reaction tank for micro-flocculation reaction for 30min to obtain a pretreatment solution; and (3) filtering the pretreatment solution by using a silicon carbide ceramic membrane to obtain a filtered clear solution, wherein the effective filtering aperture of the silicon carbide ceramic membrane is 0.06 mu m, the transmembrane pressure difference of the silicon carbide ceramic membrane is controlled to be 0.20Mpa in the filtering process of the pretreatment solution, and the membrane surface flow rate is controlled to be 2 m/s.
Gather a certain power plant's desulfurization waste water in Hebei, waste water sample index is: yellow turbidity, solid content 3.5% and SS concentration 3689 mg/L. The desulfurization waste water was treated in accordance with example 5 to obtain a clear filtrate having an index of pH >10, colorless and transparent, and a turbidity of 0.2 NTU.
Example 6
Adding sodium hydroxide into the desulfurization wastewater containing calcium sulfate to adjust the pH value of the wastewater to 10, adding sodium carbonate, mechanically stirring and uniformly mixing, wherein the ratio of the adding amount of the sodium carbonate to the solubility of the calcium sulfate is 105:172, and entering a micro-flocculation reaction tank for micro-flocculation reaction for 40min to obtain a pretreatment solution; and (3) filtering the pretreatment solution by using a silicon carbide ceramic membrane to obtain a filtered clear solution, wherein the effective filtering aperture of the silicon carbide ceramic membrane is 0.08 mu m, the transmembrane pressure difference of the silicon carbide ceramic membrane is controlled to be 0.20Mpa in the filtering process of the pretreatment solution, and the membrane surface flow rate is controlled to be 3.2 m/s.
Gather a certain power plant's desulfurization waste water in Hebei, waste water sample index is: yellow turbidity, solid content 3.5% and SS concentration 3452 mg/L. The desulfurization waste water was treated in accordance with example 6 to obtain a clear filtrate having an index of pH >10, colorless and transparent, and a turbidity of 0.25 NTU.
Example 7
Adding sodium hydroxide into the desulfurization wastewater containing calcium sulfate to adjust the pH value of the wastewater to 10.5, adding sodium carbonate, mechanically stirring and uniformly mixing, wherein the ratio of the adding amount of the sodium carbonate to the solubility of the calcium sulfate is 105:172, and entering a micro-flocculation reaction tank for micro-flocculation reaction for 50min to obtain a pretreatment solution; and (3) filtering the pretreatment solution by using a silicon carbide ceramic membrane to obtain a filtered clear solution, wherein the effective filtering aperture of the silicon carbide ceramic membrane is 0.06 mu m, the transmembrane pressure difference of the silicon carbide ceramic membrane is controlled to be 0.20Mpa in the filtering process of the pretreatment solution, and the membrane surface flow rate is controlled to be 2.2 m/s.
Gather a certain power plant's desulfurization waste water in Hebei, waste water sample index is: yellow turbidity, solid content 3.5% and SS concentration 2689 mg/L. The filtrate obtained by treating the desulfurization waste water according to example 7 was found to have an index of pH >10, colorless and transparent, and a turbidity of 0.35 NTU.
Example 8
Adding sodium hydroxide into the desulfurization wastewater containing calcium sulfate to adjust the pH value of the wastewater to 10.5, adding sodium carbonate, mechanically stirring and uniformly mixing, wherein the ratio of the adding amount of the sodium carbonate to the solubility of the calcium sulfate is 107:172, and entering a micro-flocculation reaction tank for micro-flocculation reaction for 30min to obtain a pretreatment solution; and (3) filtering the pretreatment solution by using a silicon carbide ceramic membrane to obtain a filtered clear solution, wherein the effective filtering aperture of the silicon carbide ceramic membrane is 0.05 mu m, the transmembrane pressure difference of the silicon carbide ceramic membrane is controlled to be 0.20Mpa in the filtering process of the pretreatment solution, and the membrane surface flow rate is controlled to be 2.5 m/s.
Gather a certain power plant's desulfurization waste water in Hebei, waste water sample index is: yellow turbidity, solid content 3.5% and SS concentration 2689 mg/L. The desulfurization waste water was treated in accordance with the method of example 8 to obtain a clear filtrate having an index of pH >10, colorless and transparent, and a turbidity of 0.6 NTU.
Example 9
Adding sodium hydroxide into the desulfurization wastewater containing calcium sulfate to adjust the pH value of the wastewater to 10.5, adding sodium carbonate, mechanically stirring and uniformly mixing, wherein the ratio of the adding amount of the sodium carbonate to the solubility of the calcium sulfate is 102:172, and entering a micro-flocculation reaction tank for micro-flocculation reaction for 40min to obtain a pretreatment solution; and (3) filtering the pretreatment solution by using a silicon carbide ceramic membrane to obtain a filtered clear solution, wherein the effective filtering aperture of the silicon carbide ceramic membrane is 0.07 mu m, the transmembrane pressure difference of the silicon carbide ceramic membrane is controlled to be 0.20Mpa in the filtering process of the pretreatment solution, and the membrane surface flow rate is controlled to be 2.5 m/s.
Gather a certain power plant's desulfurization waste water in Hebei, waste water sample index is: yellow turbidity, solid content 3.5% and SS concentration 2689 mg/L. The filtrate obtained by treating the desulfurization waste water according to example 9 indicated a pH value of >10, colorless and transparent, and had a turbidity of 0.1 NTU.
Example 10
Adding sodium hydroxide into the desulfurization wastewater containing calcium sulfate to adjust the pH value of the wastewater to 10, adding sodium carbonate, mechanically stirring and uniformly mixing, wherein the ratio of the adding amount of the sodium carbonate to the solubility of the calcium sulfate is 110:172, and entering a micro-flocculation reaction tank for micro-flocculation reaction for 25min to obtain a pretreatment solution; and (3) filtering the pretreatment solution by using a silicon carbide ceramic membrane to obtain a filtered clear solution, wherein the effective filtering aperture of the silicon carbide ceramic membrane is 0.05 mu m, the transmembrane pressure difference of the silicon carbide ceramic membrane is controlled to be 0.20Mpa in the filtering process of the pretreatment solution, and the membrane surface flow rate is controlled to be 2.2 m/s.
Gather a certain power plant's desulfurization waste water in Hebei, waste water sample index is: yellow turbidity, solid content 3.5% and SS concentration 2689 mg/L. The filtrate obtained by treating the desulfurization waste water according to example 10 indicated a pH value of >10, colorless and transparent, and had a turbidity of 0.4 NTU.
Claims (10)
1. A thermal power plant desulfurization wastewater clarification process based on a silicon carbide film ultrafiltration technology is characterized by comprising the following steps:
step 1, conveying the wastewater generated by a desulfurization system to a primary sedimentation tank through a wastewater pump and a pipeline, completing primary sedimentation separation in the primary sedimentation tank, forming thick slurry by sedimentation at the bottom of the primary sedimentation tank, and producing supernatant at the upper part;
step 2, enabling the supernatant of the primary sedimentation tank to enter an adjusting tank, wherein the adjusting tank is provided with a stirrer, further uniformly stirring the supernatant, and adding a sodium hydroxide solution through a dosing system to adjust the pH value of the desulfurization wastewater;
step 3, enabling the effluent of the adjusting tank to enter a micro flocculation reaction tank, adding a sodium carbonate solution through a dosing system, completing micro flocculation precipitation in the micro flocculation reaction tank, performing flocculation concentration on large particles to obtain thick slurry, discharging the thick slurry at the bottom, and obtaining a pretreatment solution from the effluent of the micro flocculation reaction tank, wherein the mass concentration is not more than 4%;
step 4, conveying the pretreatment liquid to a silicon carbide film device through a silicon carbide film circulating pump and a pipeline for filtration treatment to obtain a filtered clear liquid and a concentrated liquid;
and 5, filtering clear liquid for recycling or entering a desulfurization wastewater zero-discharge system for advanced treatment, and collecting and recycling concentrated solution and concentrated slurry discharged from the primary sedimentation tank and the micro-flocculation reaction tank to the desulfurization system to realize cyclic utilization.
2. The thermal power plant desulfurization wastewater clarification process based on the silicon carbide membrane ultrafiltration technology as claimed in claim 1, characterized in that in step 2, sodium hydroxide solution is added into a primary sedimentation tank to adjust the pH value of desulfurization wastewater to 10-11.
3. The thermal power plant desulfurization wastewater clarification process based on silicon carbide membrane ultrafiltration technology according to claim 2, characterized in that sodium carbonate solution is added into a regulating reservoir in step 3 for micro-flocculation pretreatment to obtain pretreatment liquid; the desulfurization wastewater contains calcium sulfate, and the ratio of the addition amount of sodium carbonate to the solubility of the calcium sulfate is 100-110: 172.
4. The thermal power plant desulfurization wastewater clarification process based on the silicon carbide membrane ultrafiltration technology as claimed in claim 2, characterized in that the micro-flocculation reaction time in step 3 is 5-45 min.
5. The thermal power plant desulfurization wastewater clarification process based on silicon carbide membrane ultrafiltration technology according to claim 1, characterized in that the effective filtration pore size of the silicon carbide membrane used in the silicon carbide membrane device in step 4 is 0.04-0.1 μm.
6. The thermal power plant desulfurization wastewater clarification process based on the silicon carbide membrane ultrafiltration technology according to claim 1, characterized in that the transmembrane pressure difference of the silicon carbide membrane in the pretreatment liquid filtration process in the step 4 is controlled to be 0.15-0.25 Mpa, and the membrane surface flow rate is controlled to be 2-3.5 m/s.
7. The thermal power plant desulfurization wastewater clarification process based on silicon carbide membrane ultrafiltration technology according to claim 1, characterized in that the feeding of the silicon carbide membrane device in step 4 is regulated by variable flow, and the ratio of clear liquid to concentrated liquid is kept at 2-4: 1.
8. The thermal power plant desulfurization wastewater clarification process based on silicon carbide membrane ultrafiltration technology as claimed in claim 1, characterized in that the silicon carbide membrane device in step 4 needs to be periodically back-washed, the back-washing adopts constant flow and constant pressure washing, and the water for back-washing is the clear filtrate. The silicon carbide film device is back flushed once every 15-20 minutes for 30 s.
9. The process for clarifying desulfurization wastewater of thermal power plant based on silicon carbide membrane ultrafiltration technology as claimed in claim 1, wherein after the flux of the silicon carbide membrane device in step 4 is less than 50% of the initial flux, the silicon carbide membrane device needs to be chemically cleaned by using 2-3% hydrochloric acid solution or 5-8% sulfamic acid solution.
10. The thermal power plant desulfurization wastewater clarification process based on the silicon carbide membrane ultrafiltration technology as claimed in claim 1, wherein the thick slurry discharged from the bottom of the primary sedimentation tank in step 2 and the micro flocculation reaction tank in step 3 and the thick liquid generated by the silicon carbide membrane device in step 4 are discharged to a special collection tank and returned to the desulfurization system through a collection tank lift pump and a pipeline.
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