CN111517553A - Titanium dioxide washing wastewater resource utilization treatment process - Google Patents
Titanium dioxide washing wastewater resource utilization treatment process Download PDFInfo
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Abstract
The invention provides a titanium dioxide washing wastewater resource utilization treatment process, which comprises the following steps: collecting waste water of produced water, and carrying out pretreatment after heat exchange so as to meet the water quality requirement of entering a nanofiltration membrane; the pretreated produced water enters a first-stage nanofiltration unit for concentration treatment, the concentrated water of the first-stage nanofiltration unit enters a nanofiltration adsorption filler unit for adsorption, and the produced water of the first-stage nanofiltration unit is used as the inlet water of a first-stage reverse osmosis unit; and (2) the effluent of the nanofiltration adsorption filler unit enters a nanofiltration unit at the second section for concentration, the produced water of the nanofiltration unit at the second section returns to the nanofiltration unit at the first section as the inlet water, the concentrated water of the nanofiltration unit at the second section enters a resin adsorption unit for adsorbing sulfuric acid, the effluent of the resin adsorption unit enters a reaction kettle after heat exchange, the reacted wastewater is evaporated, and then the wastewater is crystallized and dried in sequence to obtain the poly-iron product. The process provided by the invention can effectively treat titanium dioxide washing wastewater, realize zero-emission resource utilization of wastewater and change waste into valuable.
Description
Technical Field
The invention belongs to the field of coating wastewater treatment, and particularly relates to a titanium dioxide washing wastewater resource utilization treatment process.
Background
Titanium dioxide is widely used in the fields of manufacturing coatings, high-grade white paints, white rubber, synthetic fibers, welding electrodes, light reduction agents of rayon, fillers of plastics and high-grade paper and the like, and is also used in the industries of telecommunication equipment, metallurgy, printing and dyeing, enamel and the like.
The current common method for producing titanium dioxide is a sulfuric acid method. The main raw materials for producing titanium dioxide by a sulfuric acid method are titanium ore (ilmenite or acid-soluble titanium slag) and sulfuric acid, and the production process can be generally divided into ten major links: the method comprises the following steps of drying and crushing titanium ores, carrying out acidolysis on the titanium ores, purifying a titanium sulfate solution, crystallizing ferrous sulfate, hydrolyzing the titanium sulfate solution, washing and bleaching hydrated titanium dioxide, carrying out salt treatment, calcining and crushing, and carrying out surface treatment and crushing on titanium dioxide.
The waste acid discharged in the production process comes from a primary water washing procedure and a titanium dioxide hydrolysis process in the titanium sulfate solution purification process, the yield is 7-10t/t (titanium dioxide), the sulfuric acid content is 18-23%, and the FeSO4 content is about 80g/L (calculated by anhydrous FeSO 4). 20 percent of the total discharge amount of the waste acid can be directly returned to acidolysis acid preparation and used for adjusting the acidity coefficient of titanium liquid during leaching, and the rest waste acid can not be recycled. At present, most of domestic sulfuric acid process titanium dioxide factories supply the part of waste acid to nearby steel plants according to local conditions for pickling steel or supplying the waste acid to paper mills, dyeing mills and the like for treating alkaline waste water, but sometimes the problem cannot be solved due to small consumption, and the treatment methods of the part of waste acid mainly comprise the following steps:
1. waste acid concentration process
The waste acid concentration can adopt the methods of submerged combustion and vacuum concentration, the submerged combustion is to spray the high-temperature gas produced in the combustion chamber directly into the waste acid, so as to evaporate the water in the waste acid and play a role of concentrating the waste acid, because the concentration of sulfuric acid is improved, ferrous sulfate dissolved in the waste acid is separated out, but the concentration after the concentration is not high, and the corrosion of equipment is very serious, the former Soviet Union uses the method to concentrate the waste acid to 55% for sale or use for producing phosphate fertilizer, the vacuum evaporation concentration can respectively concentrate about 20% of the waste acid to 40%, 50%, 70% and even more than 90% according to the evaporation intensity and concentration grade. According to the method, in a multi-effect falling-film evaporator and a forced circulation concentrator, waste acid is concentrated to 70-80% by using steam as a heat source, a waste acid concentration pilot plant production device is established in Nanjing, Zhenjiang and the like in 80 s of the third design institute of the national department of chemical industry and the coating research of the ministry of the original chemical industry, the waste acid is settled and purified, then the waste acid is concentrated by a vacuum concentration method for more than 30%, then the waste acid is frozen at 0-5 ℃ to separate out ferric salt in the waste acid, meanwhile, the concentration of the waste acid can be increased to about 40%, and a second stage of concentration is added on the basis to increase the concentration of the waste acid to 40%, but the tube nest of the evaporator cannot be put into industrial production due to the fact that ferrous sulfate heptahydrate generated by dehydration of ferrous sulfate heptahydrate blocks the tube nest of the evaporator. The waste acid discharged in the titanium dioxide production is treated by adopting a concentration method and is popular in Europe and Japan, but waste acid concentration equipment is very expensive, energy consumption and operation cost are very high, and the cost of concentrated sulfuric acid is more expensive than that of purchased sulfuric acid, so that the factory in China is not in need of much liquid.
2. Waste acid neutralization production gypsum
The process of producing gypsum by using waste acid neutralization is to neutralize the waste acid with lime milk to pH =2.5, then to filter to obtain low-iron gypsum, the quality of the gypsum is basically the same as that of natural gypsum, and the gypsum can be used as building material.
3. Production of iron series pigment by waste acid
The waste acid contains ferrous sulfate besides sulfuric acid. The waste acid is utilized to react with the waste iron sheet and the scrap iron to obtain a ferrous sulfate solution, and then the ferrous sulfate solution is used as a raw material to produce iron series pigments such as iron oxide black, iron oxide red and the like. The iron oxide black is prepared by mixing ferrous sulfate solution with excessive soda ash, heating with water vapor (95 deg.C), filtering, washing with water, oven drying, and pulverizing. The simplest method for producing the iron oxide red is to dry and dehydrate ferrous sulfate to generate FeSO4.H2O, then calcine the raw iron oxide red at 800 ℃ to generate crude iron oxide red, and obtain a finished product after crushing, drying and re-crushing, wherein the waste gas SO3 can be recycled for preparing sulfuric acid, and the calcination method has important calcination temperature, and has a hue with a yellow phase at a lower temperature and a hue with a blue phase at a higher temperature. However, the method has high energy consumption, and needs to add a large amount of soda ash to neutralize iron, thereby causing high operation cost.
4. Ammonium sulfate and ferrous ammonium sulfate fertilizer produced by ammonia neutralization
The method for producing fertilizer by ammonia neutralization is a method adopted by chemical company in Japan, and patent 97106429.6 also discloses a method similar to chemical company in Japan, which introduces the method that ferrous sulfate is added into waste acid, liquid ammonia is directly added into the mixed solution, and then the material is directly sprayed and dried to obtain ammonium sulfate and ferrous ammonium sulfate. In addition, a method for producing liquid ammonium sulfate by using waste acid is also provided, and a titanium dioxide production line of Zibo drilling company Limited successfully performs pilot test on the method. The method is that waste acid is neutralized by ammonia water in a neutralization tank, then enters a first-stage aeration tank, is stirred by a small amount of compressed air, so that sulfuric acid and ammonia are fully reacted, and Fe2+ is converted into Fe3+At this time, the water still contains a small amount of sulfuric acid and Fe2+Therefore, secondary neutralization, aeration and filtration are arranged, so that qualified ammonium sulfate solution is obtained. This method is also a simpler and more efficient method, requiring strict control of the neutralization pH, otherwise large amounts of precipitates of iron salts belonging to the hazardous waste range will be produced.
In summary, most of the currently used waste acid treatment methods are neutralization, lime, liquid caustic soda or ammonia water are added, but the wastewater or waste acid contains a large amount of acid and also contains high-concentration iron ion concentration, and the titanium dioxide production wastewater is treated in a neutralization manner, so that the consumed alkali amount is large, and a large amount of iron slag is generated. In addition, disposal discharge of the wastewater after neutralization can also be a problem.
Disclosure of Invention
The invention aims to provide a simple, low-energy-consumption and low-cost titanium dioxide washing wastewater resource utilization treatment process aiming at the defects in the prior art.
Therefore, the invention is realized by the following technical scheme:
the titanium dioxide washing wastewater is generated in the titanium dioxide washing process, and the titanium dioxide washing wastewater recycling treatment process comprises the following steps:
(1) collecting the generated wastewater, then carrying out heat exchange on the wastewater to 25 ℃ through a heat exchanger, and then carrying out pretreatment to remove titanium dioxide solid particles in the wastewater, wherein the SDI (standard deviation) of effluent is less than or equal to 5, so as to meet the water quality requirement of a subsequent nanofiltration membrane, and carrying out filter pressing on the titanium dioxide solid particles to obtain titanium dioxide. Here, the cooling water of the heat exchanger is the effluent of the resin adsorption unit to lower the temperature of the waste water.
(2) The pretreated produced water enters a nanofiltration unit at one working section for concentration treatment, most ferrous ions are intercepted in concentrated water, and sulfuric acid exists in the nanofiltration produced water through a nanofiltration membrane, so that the separation of acid and ferrous ions is realized.
(3) The concentrated water of the nanofiltration unit in one section contains higher ferric salt, is used as the inlet water of the nanofiltration adsorption filler unit, enters the nanofiltration adsorption filler to selectively adsorb metals except iron, and can also adsorb COD (chemical oxygen demand) in the wastewater so as to reduce the pressure of the subsequent membrane operation and improve the quality of a polyferric product. And mixing the outlet water of the nanofiltration adsorption filler unit and part of the produced water of the reverse osmosis adsorption filler unit, and then entering a nanofiltration unit at the second section for further concentration. The water produced by the nanofiltration unit in the second working section returns to the nanofiltration unit in the first working section to be fed.
(4) The water produced by the nanofiltration unit in the first section is used as the inlet water of the first-stage reverse osmosis unit, the recovery rate of the first-stage reverse osmosis unit is adjusted to be 40-66%, and the concentrated water of the first-stage reverse osmosis unit enters the membrane distillation unit for low-pressure evaporation until the acid concentration is 20-30%. Then the acid enters an evaporation system for further evaporation and concentration until the acid concentration is 50% -60%. The water produced by the first-stage reverse osmosis unit enters the reverse osmosis filler adsorption unit to adsorb heavy metals so as to improve the quality of final product water. And mixing the effluent of the reverse osmosis filler adsorption unit with membrane distillation condensate and evaporation condensate, and then feeding the mixture into a secondary reverse osmosis unit for evolution and purification treatment, wherein the recovery rate of the secondary reverse osmosis unit is controlled to be 80-90%.
(5) And (2) enabling concentrated water of the nanofiltration unit in the second section to enter a resin adsorption unit to adsorb sulfuric acid, enabling water discharged from the resin adsorption unit to enter the heat exchanger in the step (1) to exchange heat with original wastewater, then entering a second-stage heat exchanger to exchange heat with external steam, and enabling the temperature to rise to 40-60 ℃. And (3) the waste water after heat exchange enters a reaction kettle, water, sulfuric acid and ferrous sulfate are sequentially added, and a catalyst is slowly added under continuous stirring to perform catalytic oxidation reaction. And taking the reacted wastewater as inlet water of an evaporation system, adding seed crystals into the evaporated concentrated solution, then sequentially entering a crystallizer for crystallization, and drying by a dryer to obtain a poly-iron product.
While adopting the technical scheme, the invention can also adopt or combine the following technical scheme:
as a preferred technical scheme of the invention: the heat exchanger adopts plate type to be one of tube type or plate type.
As a preferred technical scheme of the invention: the pretreatment is one or a combination of precipitation, microfiltration and ultrafiltration.
As a preferred technical scheme of the invention: the operating pressure of the nanofiltration unit in the first working section is 25-60 bar, the temperature is 15-40 ℃, the unit recovery rate is controlled to be 60-80%, so that the concentration of iron ions in the concentrated water of the nanofiltration unit in the first working section is 15000-25000 mg/L, and the concentration of sulfuric acid is 4-6%.
As a preferred technical scheme of the invention: the operating pressure of the second-section nanofiltration unit is 60-120 bar, the temperature is 15-40 ℃, the unit recovery rate is controlled to be 60-80%, so that the concentration of iron ions in the concentrated water of the second-section nanofiltration unit is 50000-80000 mg/L, and the concentration of sulfuric acid is 4-6%.
As a preferred technical scheme of the invention: the nanofiltration membrane material adopted by the nanofiltration unit at the first working section and/or the nanofiltration unit at the second working section is polyamide, and the molecular weight cutoff is 150-400, so that the interception rate of the nanofiltration membrane on iron ions is 90-98%, and the interception rate on sulfuric acid is 5-20%.
As a preferred technical scheme of the invention: the filler of the nanofiltration adsorption filler unit is one or a combination of more of diatomite, activated carbon, zeolite and cellulose balls.
As a preferred technical scheme of the invention: the flow of part of the outlet water of the reverse osmosis adsorption filler unit recycled to the inlet of the nanofiltration unit of the second working section is 1/4-1/2 of the concentrated water flow of the nanofiltration unit of the first working section.
As a preferred technical scheme of the invention: the operation pressure of the primary reverse osmosis unit is 60-120 bar, the temperature is 15-40 ℃, the unit recovery rate is controlled to be 40-66%, and therefore the concentration of sulfuric acid in concentrated water of the primary reverse osmosis unit is 8-15%.
As a preferred technical scheme of the invention: the filler of the reverse osmosis adsorption filler unit is one or a combination of more of diatomite, activated carbon, zeolite and cellulose balls.
As a preferred technical scheme of the invention: the operating pressure of the secondary reverse osmosis unit is 10-20 bar, the temperature is 15-40 ℃, and the unit recovery rate is controlled to be 80-90%, so that the concentration of iron ions in the water produced by the secondary reverse osmosis unit is less than or equal to 0.5mg/L, and the concentration of sulfuric acid is less than or equal to 0.1%.
As a preferred technical scheme of the invention: the interception rate of the reverse osmosis membrane in the first-stage reverse osmosis unit to iron ions is 95-99%, and the interception rate to sulfuric acid is 85-95%.
As a preferred technical scheme of the invention: the interception rate of the reverse osmosis membrane in the secondary reverse osmosis unit to iron ions is 95-99%, and the interception rate to sulfuric acid is 90-95%.
As a preferred technical scheme of the invention: the evaporation system in the step 4) is one or a combination of multiple-effect evaporation or a mechanical vapor recompression technology evaporator.
As a preferred technical scheme of the invention: the resin adsorption unit adopts one or more of strong acid type anion resin, weak acid type anion resin or acid retardation resin.
As a preferred technical scheme of the invention: the regenerant required by the regeneration of the resin adsorption unit is water produced by the reverse osmosis unit. The regeneration mode is staged regeneration, and the regeneration period is 5-15 minutes.
As a preferred technical scheme of the invention: and returning the regenerated water of the resin system to a nanofiltration unit at one working section for purification and separation of acid.
As a preferred technical scheme of the invention: the reaction temperature in the reaction kettle is 40-60 ℃; h in the reaction kettle+/Fe2+The molar ratio of ferrous sulfate to sulfuric acid is 1: 0.44-0.45, and the molar ratio of total sulfate radicals to total iron is 1.31-1.35: 1.
As a preferred technical scheme of the invention: the catalyst is HNO3、HNO2、NaNO2、NaClO3Or KClO3One or more of (a) or (b).
As a preferred technical scheme of the invention: the evaporation system in the step 5) is one or more of a mechanical vapor recompression technology evaporator, multi-effect evaporation or membrane distillation.
As a preferred technical scheme of the invention: the crystallization temperature in the crystallizer is 0-10 ℃.
The invention provides a titanium dioxide washing wastewater resource utilization treatment process, which can effectively treat titanium dioxide washing wastewater, realize zero-emission resource utilization of wastewater and change waste into valuable. The acid in the wastewater is changed into high-concentration acid which can be returned to the front end of the process for acidolysis of titanium ore, the water in the wastewater reaches the standard of titanium dioxide washing water for titanium dioxide washing, the acid is used for titanium dioxide washing, the iron salt in the wastewater is changed into polymer product which can be sold as flocculant, and the titanium dioxide in the wastewater can be recovered. Compared with the traditional lime or alkali neutralization method, the invention can at least reduce the discharge of 0.95 kg of waste iron slag per ton of waste acid, reduce the discharge of 67 kg of waste gypsum per ton of waste acid and reduce the discharge of 900 kg of waste water. Compared with the method of evaporation concentration, the invention can save energy by at least 50 percent, in addition, not only can effectively solve the problem of evaporator blockage, but also can generate the poly-iron byproduct to benefit.
Drawings
FIG. 1 is a schematic diagram of a titanium dioxide water washing wastewater resource utilization treatment process provided by the invention.
Detailed Description
The invention is described in further detail with reference to the figures and specific embodiments.
A titanium dioxide washing wastewater resource utilization treatment process is characterized in that the titanium dioxide washing wastewater is generated in the titanium dioxide washing process, and the titanium dioxide washing wastewater resource utilization treatment process comprises the following steps:
(1) collecting the generated wastewater, then carrying out heat exchange on the wastewater to 25 ℃ through a heat exchanger, and then carrying out pretreatment to remove titanium dioxide solid particles in the wastewater, wherein the SDI (standard deviation) of effluent is less than or equal to 5, so as to meet the water quality requirement of a subsequent nanofiltration membrane, and carrying out filter pressing on the titanium dioxide solid particles to obtain titanium dioxide. Here, the cooling water of the heat exchanger is the effluent of the resin adsorption unit to lower the temperature of the waste water. In addition, one or more heat exchangers may be further provided to lower the temperature of the wastewater.
(2) The pretreated produced water enters a nanofiltration unit at one working section for concentration treatment, most ferrous ions are intercepted in concentrated water, and sulfuric acid exists in the nanofiltration produced water through a nanofiltration membrane, so that the separation of acid and ferrous ions is realized.
(3) The concentrated water of the nanofiltration unit in one section contains higher ferric salt, is used as the inlet water of the nanofiltration adsorption filler unit, enters the nanofiltration adsorption filler to selectively adsorb metals except iron, and can also adsorb COD (chemical oxygen demand) in the wastewater so as to reduce the pressure of the subsequent membrane operation and improve the quality of a polyferric product. And mixing the outlet water of the nanofiltration adsorption filler unit and part of the produced water of the reverse osmosis adsorption filler unit, and then entering a nanofiltration unit at the second section for further concentration. The water produced by the nanofiltration unit in the second working section returns to the nanofiltration unit in the first working section to be fed.
(4) The water produced by the nanofiltration unit in the first section is used as the inlet water of the first-stage reverse osmosis unit, the recovery rate of the first-stage reverse osmosis unit is adjusted to be 40-66%, and the concentrated water of the first-stage reverse osmosis unit enters the membrane distillation unit for low-pressure evaporation until the acid concentration is 20-30%. Then the acid enters an evaporation system for further evaporation and concentration until the acid concentration is 50% -60%. The water produced by the first-stage reverse osmosis unit enters the reverse osmosis filler adsorption unit to adsorb heavy metals so as to improve the quality of final product water. And mixing the effluent of the reverse osmosis filler adsorption unit with membrane distillation condensate and evaporation condensate, and then feeding the mixture into a secondary reverse osmosis unit for evolution and purification treatment, wherein the recovery rate of the secondary reverse osmosis unit is controlled to be 80-90%.
(5) And (2) enabling concentrated water of the nanofiltration unit in the second section to enter a resin adsorption unit to adsorb sulfuric acid, enabling water discharged from the resin adsorption unit to enter the heat exchanger in the step (1) to exchange heat with original wastewater, then entering a second-stage heat exchanger to exchange heat with external steam, and enabling the temperature to rise to 40-60 ℃. And (3) the waste water after heat exchange enters a reaction kettle, water, sulfuric acid and ferrous sulfate are sequentially added, and a catalyst is slowly added under continuous stirring to perform catalytic oxidation reaction. And taking the reacted wastewater as inlet water of an evaporation system, adding seed crystals into the evaporated concentrated solution, then sequentially entering a crystallizer for crystallization, and drying by a dryer to obtain a poly-iron product.
While adopting the technical scheme, the invention can also adopt or combine the following technical scheme:
in this embodiment: the heat exchanger adopts plate type to be one of tube type or plate type.
In this embodiment: the pretreatment is one or a combination of precipitation, microfiltration and ultrafiltration.
In this embodiment: the operating pressure of the nanofiltration unit in the first working section is 25-60 bar, the temperature is 15-40 ℃, the unit recovery rate is controlled to be 60-80%, so that the concentration of iron ions in the concentrated water of the nanofiltration unit in the first working section is 15000-25000 mg/L, and the concentration of sulfuric acid is 4-6%.
In this embodiment: the operating pressure of the second-section nanofiltration unit is 60-120 bar, the temperature is 15-40 ℃, the unit recovery rate is controlled to be 60-80%, so that the concentration of iron ions in the concentrated water of the second-section nanofiltration unit is 50000-80000 mg/L, and the concentration of sulfuric acid is 4-6%.
In this embodiment: the nanofiltration membrane material adopted by the nanofiltration unit at the first working section and/or the nanofiltration unit at the second working section is polyamide, and the molecular weight cutoff is 150-400, so that the interception rate of the nanofiltration membrane on iron ions is 90-98%, and the interception rate on sulfuric acid is 5-20%.
In this embodiment: the filler of the nanofiltration adsorption filler unit is one or a combination of more of diatomite, activated carbon, zeolite and cellulose balls.
In this embodiment: the flow of part of the outlet water of the reverse osmosis adsorption filler unit recycled to the inlet of the nanofiltration unit of the second working section is 1/4-1/2 of the concentrated water flow of the nanofiltration unit of the first working section.
In this embodiment: the operation pressure of the primary reverse osmosis unit is 60-120 bar, the temperature is 15-40 ℃, the unit recovery rate is controlled to be 40-66%, and therefore the concentration of sulfuric acid in concentrated water of the primary reverse osmosis unit is 8-15%.
In this embodiment: the filler of the reverse osmosis adsorption filler unit is one or a combination of more of diatomite, activated carbon, zeolite and cellulose balls.
In this embodiment: the operating pressure of the secondary reverse osmosis unit is 10-20 bar, the temperature is 15-40 ℃, and the unit recovery rate is controlled to be 80-90%, so that the concentration of iron ions in the water produced by the secondary reverse osmosis unit is less than or equal to 0.5mg/L, and the concentration of sulfuric acid is less than or equal to 0.1%.
In this embodiment: the interception rate of the reverse osmosis membrane in the first-stage reverse osmosis unit to iron ions is 95-99%, and the interception rate to sulfuric acid is 85-95%.
In this embodiment: the interception rate of the reverse osmosis membrane in the secondary reverse osmosis unit to iron ions is 95-99%, and the interception rate to sulfuric acid is 90-95%.
In this embodiment: the evaporation system in the step 4) is one or a combination of a mechanical vapor recompression technology evaporator or multiple-effect evaporation.
In this embodiment: the resin adsorption unit adopts one or more of strong acid type anion resin, weak acid type anion resin or acid retardation resin.
In this embodiment: the regenerant required by the regeneration of the resin adsorption unit is water produced by the reverse osmosis unit. The regeneration mode is staged regeneration, and the regeneration period is 5-15 minutes.
In this embodiment: and returning the regenerated water of the resin system to a nanofiltration unit at one working section for purification and separation of acid.
In this embodiment: the reaction temperature in the reaction kettle is 40-60 ℃; h in the reaction kettle+/Fe2+The molar ratio of ferrous sulfate to sulfuric acid is 1: 0.44-0.45, and the molar ratio of total sulfate radicals to total iron is 1.31-1.35: 1.
In this embodiment: the catalyst is HNO3、HNO2、NaNO2、NaClO3Or KClO3One or more of (a) or (b).
In this embodiment: the evaporation system in the step 5) is one or more of a mechanical vapor recompression technology evaporator, multi-effect evaporation or membrane distillation.
In this embodiment: the crystallization temperature in the crystallizer is 0-10 ℃.
The invention provides a titanium dioxide washing wastewater resource utilization treatment process, which can effectively treat titanium dioxide washing wastewater, realize zero-emission resource utilization of wastewater and change waste into valuable. The acid in the wastewater is changed into high-concentration acid which can be returned to the front end of the process for acidolysis of titanium ore, the water in the wastewater reaches the standard of the water for washing titanium dioxide, and the high-concentration acid is used for washing titanium dioxide, and the iron salt in the wastewater is changed into polymer product which can be sold as flocculant. Compared with the traditional lime or alkali neutralization method, the invention can at least reduce the discharge of 0.95 kg of waste iron slag per ton of waste acid, reduce the discharge of 67 kg of waste gypsum per ton of waste acid and reduce the discharge of 900 kg of waste water. Compared with the method of evaporation concentration, the invention can save energy by at least 50 percent, in addition, not only can effectively solve the problem of evaporator blockage, but also can generate the poly-iron byproduct to benefit.
The above-described embodiments are intended to illustrate the present invention, but not to limit the present invention, and any modifications, equivalents, improvements, etc. made within the spirit of the present invention and the scope of the claims fall within the scope of the present invention.
Claims (10)
1. A titanium dioxide washing wastewater resource utilization treatment process is characterized in that: the titanium dioxide washing wastewater resource utilization treatment process comprises the following steps: collecting waste water of produced water, reducing the temperature of the waste water through heat exchange, and removing titanium dioxide solid particles in the waste water through pretreatment to ensure that the SDI (standard deviation) of the effluent is less than or equal to 5 so as to meet the water quality requirement of entering a nanofiltration membrane, wherein the titanium dioxide solid particles are subjected to filter pressing to obtain titanium dioxide; the pretreated produced water enters a nanofiltration unit at one working section for concentration treatment, so that most of ferrous ions are intercepted in the concentrated water of the nanofiltration unit at one working section, and the sulfuric acid enters the produced water through the nanofiltration membrane to realize the separation of acid and ferrous ions; concentrated water of a nanofiltration unit at the first working section is used as inlet water of a nanofiltration adsorption filler unit, enters the nanofiltration adsorption filler unit to selectively adsorb metals except iron, and simultaneously adsorbs COD (chemical oxygen demand) in wastewater so as to reduce the pressure of subsequent membrane operation and improve the quality of subsequent polyferric products, and water produced by the nanofiltration unit at the first working section is used as inlet water of a primary reverse osmosis unit; the effluent of the nanofiltration adsorption filler unit enters a nanofiltration unit at a second section for concentration, the produced water of the nanofiltration unit at the second section returns to the nanofiltration unit at the first section as inlet water, the concentrated water of the nanofiltration unit at the second section enters a resin adsorption unit for adsorbing sulfuric acid, the temperature of the effluent of the resin adsorption unit is increased through heat exchange, the effluent enters a reaction kettle, water, sulfuric acid and ferrous sulfate are sequentially added into the reaction kettle, a catalyst is slowly added under continuous stirring for catalytic oxidation reaction, the waste water after the reaction is evaporated, seed crystals are added into the evaporated concentrated solution, and then the concentrated solution is sequentially crystallized and dried to obtain a poly-iron product; concentrated water of the first-stage reverse osmosis unit enters the membrane distillation unit to be evaporated at low pressure until the acid concentration is 20-30%, then enters the evaporation unit to be evaporated to be concentrated until the acid concentration is 50-60%, water produced by the first-stage reverse osmosis unit enters the reverse osmosis filler adsorption unit to adsorb heavy metals, effluent of the reverse osmosis filler adsorption unit, condensate water of membrane distillation and condensate water of the evaporation unit after the membrane distillation all enter the second-stage reverse osmosis unit to be purified, and part of effluent of the reverse osmosis filler adsorption unit is introduced into the second-stage nanofiltration unit.
2. The titanium dioxide washing wastewater resource utilization treatment process according to claim 1, characterized in that: the operating pressure of the nanofiltration unit in the first working section is 25-60 bar, the temperature is 15-40 ℃, the unit recovery rate is controlled to be 60-80%, so that the concentration of iron ions in the concentrated water of the nanofiltration unit in the first working section is 15000-25000 mg/L, and the concentration of sulfuric acid is 4-6%.
3. The titanium dioxide washing wastewater resource utilization treatment process according to claim 1, characterized in that: the operating pressure of the second-section nanofiltration unit is 60-120 bar, the temperature is 15-40 ℃, the unit recovery rate is controlled to be 60-80%, so that the concentration of iron ions in the concentrated water of the second-section nanofiltration unit is 50000-80000 mg/L, and the concentration of sulfuric acid is 4-6%.
4. The titanium dioxide washing wastewater resource utilization treatment process according to claim 1, characterized in that: the nanofiltration membranes in the nanofiltration units in the first working section and the second working section are made of polyamide, and the molecular weight cutoff is 150-400, so that the iron ion interception rate is 90-98%, and the sulfuric acid interception rate is 5-20%.
5. The titanium dioxide washing wastewater resource utilization treatment process according to claim 1, characterized in that: the filler of the nanofiltration adsorption filler unit and/or the reverse osmosis adsorption filler unit is one or a combination of diatomite, activated carbon, zeolite and cellulose balls.
6. The titanium dioxide washing wastewater resource utilization treatment process according to claim 1, characterized in that: the operation pressure of the primary reverse osmosis unit is 60-120 bar, the temperature is 15-40 ℃, the unit recovery rate is controlled to be 40-66%, and therefore the concentration of sulfuric acid in concentrated water of the primary reverse osmosis unit is 8-15%.
7. The titanium dioxide washing wastewater resource utilization treatment process according to claim 1, characterized in that: the operating pressure of the secondary reverse osmosis unit is 10-20 bar, the temperature is 15-40 ℃, and the unit recovery rate is controlled to be 80-90%, so that the concentration of iron ions in the water produced by the secondary reverse osmosis unit is less than or equal to 0.5mg/L, and the concentration of sulfuric acid is less than or equal to 0.1%.
8. The titanium dioxide washing wastewater resource utilization treatment process according to claim 1, characterized in that: the reaction temperature in the reaction kettle is 40-60 ℃; h in the reaction kettle+/Fe2+The molar ratio of ferrous sulfate to sulfuric acid is 1: 0.44-0.45, and the molar ratio of total sulfate radicals to total iron is 1.31-1.35: 1.
9. The titanium dioxide washing wastewater resource utilization treatment process according to claim 1, characterized in that: the catalyst is HNO3、HNO2、NaNO2、NaClO3Or KClO3One or more of (a) or (b).
10. The titanium dioxide washing wastewater resource utilization treatment process according to claim 1, characterized in that: the crystallization temperature is 0-10 ℃.
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Application publication date: 20200811 |