CN111268859A - Method for simultaneously preparing hydrochloric acid and sodium hydroxide by utilizing reverse osmosis strong brine - Google Patents

Method for simultaneously preparing hydrochloric acid and sodium hydroxide by utilizing reverse osmosis strong brine Download PDF

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CN111268859A
CN111268859A CN202010071570.5A CN202010071570A CN111268859A CN 111268859 A CN111268859 A CN 111268859A CN 202010071570 A CN202010071570 A CN 202010071570A CN 111268859 A CN111268859 A CN 111268859A
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wastewater
water
reverse osmosis
enters
effluent
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陈鹏
马光宇
胡绍伟
王飞
刘芳
王永
徐伟
高军
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Angang Steel Co Ltd
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Abstract

The invention relates to a method for simultaneously preparing hydrochloric acid and sodium hydroxide by utilizing reverse osmosis strong brine, wherein metallurgical reverse osmosis strong brine enters a regulating tank, calcium hydroxide solution and PAM are added, then anhydrous sodium carbonate is added, supernatant flows into a denitrification biological filter, methanol is added into the denitrification biological filter, and effluent of the denitrification biological filter enters a first ozone oxidation tower; the effluent of the first ozone oxidation tower enters a sand filter; then the wastewater enters an ultrafiltration device, ultrafiltration produced water enters a second-stage reverse osmosis system RO for concentration and separation, high-salt water generated by the second-stage reverse osmosis system RO is injected into chelating type ion exchange resin, and effluent enters a second ozone oxidation tower; the nanofiltration device divides the wastewater into water and concentrated water, the concentrated water is sent to a blast furnace for slag flushing or an incinerator, and the nanofiltration water is sent to a bipolar membrane electrodialysis device. The advantages are that: the process has the advantages of low energy consumption, low cost, simple equipment, easy operation and stable treatment effect.

Description

Method for simultaneously preparing hydrochloric acid and sodium hydroxide by utilizing reverse osmosis strong brine
Technical Field
The invention belongs to the technical field of industrial wastewater treatment, and particularly relates to a method for simultaneously preparing hydrochloric acid and sodium hydroxide by utilizing reverse osmosis concentrated brine.
Background
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 further reduced, the cyclic utilization rate of water of the steel enterprises is improved, and the comprehensive treatment and recycling of wastewater of the steel enterprises are enhanced, which is one of the keys for realizing sustainable development of the steel enterprises.
The reuse of wastewater is the final target of wastewater treatment, but after the wastewater is subjected to reverse osmosis treatment, most of primary pure water is obtained, and simultaneously, a large proportion of high-salinity concentrated water is also produced, the concentrated water is an inevitable product of a reverse osmosis desalination process, contains high organic matters and salt concentration, and the concentrated water content is about 25% of the reverse osmosis treatment water content. For the high-salinity concentrated water, the treatment method at the present stage is basically direct discharge, which causes a great deal of resource waste and environmental pollution.
Patent application No.: 201010283192.3, discloses a process for desalting strong brine by pervaporation technology and recovers purified water. The technology has high operation energy consumption, needs to heat the strong brine to more than 60 ℃, can only remove salt in the strong brine, and cannot effectively remove organic matters in the strong brine. Patent application No.: 200910070804.8, a forward osmosis membrane module is adopted, the seawater desalination strong brine is used as a drawing liquid, fresh water is used as a feeding liquid, part of the fresh water which permeates the seawater desalination strong brine at the permeation side of the forward osmosis membrane module and the feeding liquid side is mixed into diluted standard salt water and then is discharged out of the forward osmosis membrane module, and the rest of the feeding liquid is discharged out of the forward osmosis membrane module. The technology can only be used for treating the seawater strong brine, and is not suitable for the strong brine process in the metallurgical industry. Patent publication No. CN1030773143B discloses a strong brine zero emission treatment process of steel plant, adopts tertiary reverse osmosis process to carry out waste water concentration, then carries out evaporation crystallization. The concentration of the three-stage reverse osmosis has high operation cost, and the process does not consider the problems of organic pollution, inorganic scaling and the like of the reverse osmosis membrane. Patent publication No. CN103253820B discloses a high-efficient liquid zero release waste water treatment method and system, and although this system has the advantage that the energy consumption is low efficient, the mixed salt that obtains can't be dealt with just becomes secondary pollutant, even dangerous discarded object, consequently does not solve the problem of solid salt retrieval and utilization, still puzzles the further development of enterprise.
In conclusion, the existing strong brine treatment process of metallurgical enterprises has the defects of poor treatment effect, serious membrane pollution, low water yield of a system and overhigh process operation cost. Therefore, the development of an efficient method for resource utilization of the concentrated brine of the metallurgical enterprise can save a large amount of new water resources for the metallurgical enterprise, the adverse effect of the discharge of the concentrated brine on the environment of the surrounding water area can be reduced by greatly reducing the discharge amount of the concentrated brine, the resource utilization of the production wastewater is a new benefit growth point, and the method has important significance for realizing water saving and emission reduction of the enterprise.
Disclosure of Invention
Aiming at the reverse osmosis concentrated brine discharged by steel enterprises, the method is sequentially carried out with a sedimentation tank, a denitrification tank, an ozone oxidation tank, a sand filter, ultrafiltration, reverse osmosis, ion exchange resin, ozone oxidation, nanofiltration salt separation and bipolar membrane electrodialysis for treatment, and the concentrated solution of the comprehensive wastewater can be finally converted into acid and alkali byproducts.
In order to achieve the purpose, the invention is realized by the following technical scheme:
a method for simultaneously preparing hydrochloric acid and sodium hydroxide by utilizing reverse osmosis concentrated brine comprises the following steps:
1) firstly, feeding metallurgical reverse osmosis strong brine into a regulating tank, adding a calcium hydroxide solution while stirring to regulate the pH value of the wastewater to 11-12, adding 1-2ppm of PAM, and precipitating for 0.5-1.5 hours; adding anhydrous sodium carbonate, stirring for reaction for 20-30 minutes, precipitating for 1-2 hours, effectively removing total hardness and fluoride ions in raw water through precipitation, enabling supernatant to flow into a denitrification biological filter, adjusting the pH value of wastewater to 8.0-9.0, supplementing methanol into the denitrification biological filter to provide sufficient carbon source for nitrate denitrification, wherein the biological filter is filled with ceramsite filter material, and the hydraulic retention time is 7-9 hours;
2) the effluent of the denitrification biological filter enters a first ozone oxidation tower, the pH of the wastewater is controlled to be 11.0-12.0, the adding amount of ozone is 20-24mg/L, and under the strong oxidation effect of the ozone, organic matters which cannot be biodegraded in the wastewater are oxidized into micromolecular organic matters which are easy to biodegrade or are partially mineralized by the ozone;
3) the effluent of the first ozone oxidation tower enters a sand filter, fine suspended matters and particles are further removed, the quality of the effluent is enhanced, and backwash water of the biological filter and the sand filter returns to a front-end regulating tank; the pH of the effluent of sand filtration is adjusted to control the pH of the wastewater to be 6.2-6.6, then the wastewater enters an ultrafiltration device to further intercept suspended matters and colloid pollutants in the wastewater, concentrated water of the ultrafiltration device flows back to an adjusting tank to be circularly treated, ultrafiltration produced water enters a two-stage reverse osmosis system RO to be concentrated and separated to intercept most of salt and small molecular organic matters in the wastewater, the RO produced water of the two-stage reverse osmosis system enters a fresh water storage tank to be recycled, high salt water generated by the RO of the two-stage reverse osmosis system is injected into chelate ion exchange resin to adsorb residual calcium, magnesium and other metal ions in the wastewater through the exchange performance of the resin, regeneration wastewater of the ion exchange resin flows back to the adjusting tank to be circularly treated, effluent enters a second ozone oxidation tower to control the pH of the wastewater in the oxidation tank to be 11-12, and the ozone dosage to be 22-28mg/L, adjusting the pH of the effluent of the second ozone oxidation tower to 6.4-6.8, and then feeding the effluent into a nanofiltration device;
4) the nanofiltration device divides the wastewater into water and concentrated water, the nanofiltration concentrated water is sent to a blast furnace for slag flushing or an incinerator, the nanofiltration water is sent to a bipolar membrane electrodialysis device for treatment, the bipolar membrane electrodialysis device finally converts the salt in the nanofiltration water into corresponding hydrochloric acid and sodium hydroxide, and the low-concentration hydrochloric acid and sodium hydroxide can be reused for acid-base regulation in the system.
The metallurgy reverse osmosis strong brine is reverse osmosis strong brine for steel production, the pH is 7.0-8.5, the conductivity is 7.0-8.0ms/cm, the COD is 80-100mg/L, the nitrate radical is less than or equal to 90mg/L, and the fluorine ion is less than or equal to 35 mg/L.
Compared with the prior art, the invention has the beneficial effects that:
the method is used for treating the reverse osmosis strong brine discharged by steel enterprises by a sedimentation tank, a denitrification tank, an ozone oxidation tank, a sand filter tank, ultrafiltration, reverse osmosis, ion exchange resin, ozone oxidation, nanofiltration salt separation and bipolar membrane electrodialysis in sequence, so that the recovery rate of the strong brine is more than 85 percent, the quality of recycled water is superior to the quality requirement of industrial fresh water, and the produced by-products, namely hydrochloric acid and sodium hydroxide can be recycled for regeneration of the ion exchange resin, pretreatment softening of wastewater, acidification of wastewater RO process, acid-base neutralization process and the like, thereby saving the cost of purchased acid and base and realizing resource utilization. The electric flocculation and electric adsorption technology selected in the treatment process makes full use of the characteristic of high salt content of metallurgical strong brine, and the treatment process has the advantages of low energy consumption, low cost, simple equipment, easy operation and stable treatment effect.
Drawings
FIG. 1 is a process flow diagram of a process for the simultaneous production of hydrochloric acid and sodium hydroxide using reverse osmosis concentrated brine.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings, but it should be noted that the present invention is not limited to the following embodiments.
Example 1:
referring to fig. 1, the method for simultaneously preparing hydrochloric acid and sodium hydroxide by using reverse osmosis concentrated brine, wherein the metallurgy reverse osmosis concentrated brine is reverse osmosis concentrated brine produced in steel production, has the pH value of 7.0-8.5, the conductivity of 7.0-8.0ms/cm, the COD of 80-100mg/L, the nitrate radical of less than or equal to 90mg/L and the fluoride ion of less than or equal to 35mg/L, and specifically comprises the following steps:
1) the method comprises the steps of firstly feeding metallurgical reverse osmosis strong brine into a regulating tank, adding a calcium hydroxide solution while stirring to regulate the pH value of wastewater to 11, adding 1ppm PAM, precipitating for 0.5h, adding anhydrous sodium carbonate, stirring to react for 20min, precipitating for 1 h, effectively removing total hardness, fluorine and other ions in raw water through precipitation, enabling supernatant to flow into a denitrification biofilter, regulating the pH value of wastewater to 8.0, supplementing methanol into the denitrification biofilter as an additional carbon source for microbial denitrification, and controlling the hydraulic retention time of the biofilter for 7 h.
2) The effluent of the denitrification biological filter enters a first ozone oxidation tower, the pH of the wastewater is controlled to be 11.0, the ozone dosage is 20mg/L, the effluent of the first ozone oxidation tower enters a sand filter, fine suspended matters and particles are further removed, backwash water of a denitrification tank and the sand filter returns to a front end regulation tank, the pH of sand filtration effluent is regulated to control the pH of the wastewater to be 6.2, then the wastewater enters an ultrafiltration device, pollutants such as suspended matters, colloid and the like in the wastewater are further intercepted, concentrated water of the ultrafiltration device returns to the regulation tank for circulation treatment, ultrafiltration effluent enters a two-stage reverse osmosis system RO for concentration and separation, water produced by the RO system enters a new water storage tank for reuse (the conductivity is less than 80 mus/cm, the COD is less than 5mg/L, and the total hardness is less than 0.1mg/L), and the water quality is far better than the standard requirements of GB/T19923-2005-industrial water quality for regeneration and utilization of urban sewage, the total recovery rate of RO of the two-stage reverse osmosis system is 89%, high-salt water generated by the RO system is injected into chelate ion exchange resin, residual metal ions such as calcium, magnesium and the like in the wastewater are adsorbed by the exchange performance of the resin, the regeneration wastewater of the ion exchange resin flows back to the regulating reservoir for circular treatment, the effluent enters a second ozone oxidation tower, the pH of the wastewater in the oxidation tower is controlled to be 11, the ozone adding amount is 22mg/L, and the effluent of the second ozone oxidation tower enters a nanofiltration device after the pH is regulated to 6.4;
3) the nanofiltration device divides the wastewater into water and concentrated water, the nanofiltration concentrated water is sent to a blast furnace for slag flushing or an incinerator, the nanofiltration water is sent to a bipolar membrane electrodialysis device for treatment, the bipolar membrane electrodialysis device finally converts the salt in the nanofiltration water into corresponding hydrochloric acid and sodium hydroxide, the mass fraction of the hydrochloric acid is 5.82%, the mass fraction of the sodium hydroxide is 5.63%, and the recovered hydrochloric acid and sodium hydroxide can be used for regeneration of ion exchange resin, pretreatment and softening of the wastewater, acidification of wastewater RO process, acid-base neutralization process and the like, so that the cost of purchased acid-base is saved, and the resource utilization is realized.
Example 2:
referring to fig. 1, the method for simultaneously preparing hydrochloric acid and sodium hydroxide by using reverse osmosis concentrated brine, wherein the metallurgy reverse osmosis concentrated brine is reverse osmosis concentrated brine produced in steel production, has the pH value of 7.0-8.5, the conductivity of 7.0-8.0ms/cm, the COD of 80-100mg/L, the nitrate radical of less than or equal to 90mg/L and the fluoride ion of less than or equal to 35mg/L, and specifically comprises the following steps:
1) the method comprises the steps of firstly feeding metallurgical reverse osmosis strong brine into a regulating tank, adding a calcium hydroxide solution while stirring to regulate the pH value of wastewater to 11.5, adding 1.5ppm PAM, precipitating for 1.0h, adding anhydrous sodium carbonate, stirring for reacting for 25min, precipitating for 1.5h, effectively removing total hardness, fluorine and other ions in raw water through precipitation, enabling supernatant to flow into a denitrification biofilter, regulating the pH value of wastewater to 8.5, supplementing methanol into the denitrification biofilter as an additional carbon source for microbial denitrification, and controlling the hydraulic retention time of the biofilter for 8 h.
2) The effluent of the denitrification biological filter enters a first ozone oxidation tower, the pH of the wastewater is controlled to be 11.5, the ozone dosage is 22mg/L, the effluent of the first ozone oxidation tower enters a sand filter, fine suspended matters and particles are further removed, backwash water of a denitrification tank and the sand filter returns to a front end regulation tank, the pH of sand filtration effluent is regulated to control the pH of the wastewater to be 6.4, then the wastewater enters an ultrafiltration device, pollutants such as suspended matters, colloid and the like in the wastewater are further intercepted, concentrated water of the ultrafiltration device returns to the regulation tank for circulation treatment, ultrafiltration effluent enters a two-stage reverse osmosis system RO for concentration and separation, water produced by the RO system enters a new water storage tank for reuse (the conductivity is less than 80 mus/cm, the COD is less than 5mg/L, and the total hardness is less than 0.1mg/L), and the water quality is far better than the standard requirements of GB/T19923-2005-industrial water quality for regeneration and utilization of urban sewage, the total recovery rate of the two-stage reverse osmosis system is 91%, the high-salt water generated by the RO system is injected into chelate ion exchange resin, residual metal ions such as calcium, magnesium and the like in the wastewater are adsorbed by the exchange performance of the resin, the regenerated wastewater of the ion exchange resin flows back to the regulating reservoir for circular treatment, the effluent enters a second ozone oxidation tower, the pH of the wastewater in the oxidation tower is controlled to be 11.5, the ozone adding amount is 25mg/L, and the effluent of the second ozone oxidation tower enters a nanofiltration device after the pH is regulated to be 6.6;
3) the nanofiltration device divides the wastewater into water and concentrated water, the nanofiltration concentrated water is sent to a blast furnace for slag flushing or an incinerator, the nanofiltration water is sent to a bipolar membrane electrodialysis device for treatment, the bipolar membrane electrodialysis device finally converts the salt in the nanofiltration water into corresponding hydrochloric acid and sodium hydroxide, the mass fraction of the hydrochloric acid is 5.75%, the mass fraction of the sodium hydroxide is 5.52%, and the recovered hydrochloric acid and sodium hydroxide can be used for regeneration of ion exchange resin, pretreatment and softening of the wastewater, acidification of wastewater RO process, acid-base neutralization process and the like, so that the cost of purchased acid-base is saved, and the resource utilization is realized.
Example 3:
referring to fig. 1, the method for simultaneously preparing hydrochloric acid and sodium hydroxide by using reverse osmosis concentrated brine, wherein the metallurgy reverse osmosis concentrated brine is reverse osmosis concentrated brine produced in steel production, has the pH value of 7.0-8.5, the conductivity of 7.0-8.0ms/cm, the COD of 80-100mg/L, the nitrate radical of less than or equal to 90mg/L and the fluoride ion of less than or equal to 35mg/L, and specifically comprises the following steps:
1) the method comprises the steps of firstly feeding metallurgical reverse osmosis strong brine into a regulating tank, adding a calcium hydroxide solution while stirring to regulate the pH value of wastewater to 12, adding 2ppm PAM, precipitating for 1.5h, adding a certain amount of anhydrous sodium carbonate, stirring for reacting for 30min, precipitating for 2 h, effectively removing total hardness, fluorine and other ions in raw water through precipitation, feeding supernatant into a denitrification biofilter, regulating the pH value of wastewater to 9.0, supplementing methanol into the denitrification biofilter as an external carbon source for microbial denitrification, and controlling the hydraulic retention time of the biofilter for 9 h.
2) The effluent of the denitrification biological filter enters a first ozone oxidation tower, the pH of the wastewater is controlled to be 12.0, the ozone dosage is 24mg/L, the effluent of the first ozone oxidation tower enters a sand filter, fine suspended matters and particles are further removed, backwash water of the denitrification tank and the sand filter returns to a front end regulation tank, the pH of sand filtration effluent is regulated to control the pH of the wastewater to be 6.6, then the wastewater enters an ultrafiltration device, pollutants such as suspended matters, colloid and the like in the wastewater are further intercepted, concentrated water of the ultrafiltration device flows back to the regulation tank for circulation treatment, ultrafiltration product water enters a two-stage reverse osmosis system (RO) for concentration and separation, the RO system product water enters a fresh water storage tank for reuse (the electric conductivity is less than 80 mu s/cm, the COD is less than 5mg/L, and the total hardness is less than 0.1mg/L), and the water quality is far better than the standard requirements of GB/T19923-2005 urban sewage regeneration industrial water), the total recovery rate of the two-stage reverse osmosis system is 90%, the high-salt water generated by the RO system is injected into chelate ion exchange resin, residual metal ions such as calcium, magnesium and the like in the wastewater are adsorbed by the exchange performance of the resin, the regenerated wastewater of the ion exchange resin flows back to the regulating reservoir for circular treatment, the effluent enters a second ozone oxidation tower, the pH of the wastewater in the oxidation tower is controlled to be 12, the ozone adding amount is 28mg/L, and the effluent of the second ozone oxidation tower enters a nanofiltration device after the pH is regulated to 6.8;
3) nanofiltration divides the wastewater into water and concentrated water, the nanofiltration concentrated water is sent to a blast furnace for slag flushing or an incinerator, the nanofiltration water is sent to a bipolar membrane electrodialysis device for treatment, the bipolar membrane electrodialysis device finally converts the salt in the nanofiltration water into corresponding hydrochloric acid and sodium hydroxide, the mass fraction of the sodium chloride is 5.68%, the mass fraction of the sodium hydroxide is 5.47%, and the recovered hydrochloric acid and sodium hydroxide can be used for regeneration of ion exchange resin, pretreatment softening of the wastewater, acidification of wastewater RO process, acid-base neutralization process and the like, so that the cost of purchased acid-base is saved, and the resource utilization is realized.

Claims (2)

1. A method for simultaneously preparing hydrochloric acid and sodium hydroxide by utilizing reverse osmosis concentrated brine is characterized by comprising the following steps:
1) firstly, feeding metallurgical reverse osmosis strong brine into a regulating tank, adding a calcium hydroxide solution while stirring to regulate the pH value of the wastewater to 11-12, adding 1-2ppm of PAM, and precipitating for 0.5-1.5 hours; adding anhydrous sodium carbonate, stirring for reaction for 20-30 minutes, precipitating for 1-2 hours, effectively removing total hardness and fluoride ions in raw water through precipitation, enabling supernatant to flow into a denitrification biological filter, adjusting the pH value of wastewater to 8.0-9.0, supplementing methanol into the denitrification biological filter to provide sufficient carbon source for nitrate denitrification, wherein the biological filter is filled with ceramsite filter material, and the hydraulic retention time is 7-9 hours;
2) the effluent of the denitrification biological filter enters a first ozone oxidation tower, the pH of the wastewater is controlled to be 11.0-12.0, the adding amount of ozone is 20-24mg/L, and under the strong oxidation effect of the ozone, organic matters which cannot be biodegraded in the wastewater are oxidized into micromolecular organic matters which are easy to biodegrade or are partially mineralized by the ozone;
3) the effluent of the first ozone oxidation tower enters a sand filter, fine suspended matters and particles are further removed, the quality of the effluent is enhanced, and backwash water of the biological filter and the sand filter returns to a front-end regulating tank; the pH of the effluent of sand filtration is adjusted to control the pH of the wastewater to be 6.2-6.6, then the wastewater enters an ultrafiltration device to further intercept suspended matters and colloid pollutants in the wastewater, concentrated water of the ultrafiltration device flows back to an adjusting tank to be circularly treated, ultrafiltration produced water enters a two-stage reverse osmosis system RO to be concentrated and separated to intercept most of salt and small molecular organic matters in the wastewater, the RO produced water of the two-stage reverse osmosis system enters a fresh water storage tank to be recycled, high salt water generated by the RO of the two-stage reverse osmosis system is injected into chelate ion exchange resin to adsorb residual calcium, magnesium and other metal ions in the wastewater through the exchange performance of the resin, regeneration wastewater of the ion exchange resin flows back to the adjusting tank to be circularly treated, effluent enters a second ozone oxidation tower to control the pH of the wastewater in the oxidation tank to be 11-12, and the ozone dosage to be 22-28mg/L, adjusting the pH of the effluent of the second ozone oxidation tower to 6.4-6.8, and then feeding the effluent into a nanofiltration device;
4) the nanofiltration device divides the wastewater into water and concentrated water, the nanofiltration concentrated water is sent to a blast furnace for slag flushing or an incinerator, the nanofiltration water is sent to a bipolar membrane electrodialysis device for treatment, the bipolar membrane electrodialysis device finally converts the salt in the nanofiltration water into corresponding hydrochloric acid and sodium hydroxide, and the low-concentration hydrochloric acid and sodium hydroxide can be reused for acid-base regulation in the system.
2. The method as claimed in claim 1, wherein the metallurgical reverse osmosis concentrated brine is reverse osmosis concentrated brine produced from steel, pH is 7.0-8.5, conductivity is 7.0-8.0ms/cm, COD is 80-100mg/L, nitrate radical is less than or equal to 90mg/L, and fluoride ion is less than or equal to 35 mg/L.
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