CN210505911U - System for preparing nano magnesium oxide powder by taking desulfurization wastewater as raw material - Google Patents
System for preparing nano magnesium oxide powder by taking desulfurization wastewater as raw material Download PDFInfo
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- CN210505911U CN210505911U CN201821784246.2U CN201821784246U CN210505911U CN 210505911 U CN210505911 U CN 210505911U CN 201821784246 U CN201821784246 U CN 201821784246U CN 210505911 U CN210505911 U CN 210505911U
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- 239000002351 wastewater Substances 0.000 title claims abstract description 52
- 238000006477 desulfuration reaction Methods 0.000 title claims abstract description 42
- 230000023556 desulfurization Effects 0.000 title claims abstract description 42
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 title claims abstract description 18
- 239000002994 raw material Substances 0.000 title claims abstract description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 113
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 45
- 229910001425 magnesium ion Inorganic materials 0.000 claims abstract description 17
- 238000001223 reverse osmosis Methods 0.000 claims abstract description 14
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 claims abstract description 13
- 239000000347 magnesium hydroxide Substances 0.000 claims abstract description 13
- 229910001862 magnesium hydroxide Inorganic materials 0.000 claims abstract description 13
- 239000000395 magnesium oxide Substances 0.000 claims abstract description 12
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 claims abstract description 12
- 150000002500 ions Chemical class 0.000 claims abstract description 11
- 238000001354 calcination Methods 0.000 claims abstract description 10
- 229910001385 heavy metal Inorganic materials 0.000 claims abstract description 7
- 238000006243 chemical reaction Methods 0.000 claims description 110
- 239000012528 membrane Substances 0.000 claims description 40
- 229910001424 calcium ion Inorganic materials 0.000 claims description 29
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 claims description 28
- 238000001728 nano-filtration Methods 0.000 claims description 23
- 238000001556 precipitation Methods 0.000 claims description 22
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 claims description 16
- 239000000126 substance Substances 0.000 claims description 15
- 239000002244 precipitate Substances 0.000 claims description 14
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 13
- 239000011575 calcium Substances 0.000 claims description 13
- 229910052791 calcium Inorganic materials 0.000 claims description 12
- 150000003839 salts Chemical class 0.000 claims description 10
- 239000011777 magnesium Substances 0.000 claims description 8
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 7
- 230000003009 desulfurizing effect Effects 0.000 claims description 7
- 238000001035 drying Methods 0.000 claims description 7
- 229910052749 magnesium Inorganic materials 0.000 claims description 7
- 239000010802 sludge Substances 0.000 claims description 6
- 239000002270 dispersing agent Substances 0.000 claims description 5
- 238000011033 desalting Methods 0.000 claims description 4
- 238000000227 grinding Methods 0.000 claims description 4
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 3
- 238000011085 pressure filtration Methods 0.000 claims description 3
- 238000000034 method Methods 0.000 abstract description 17
- 238000000926 separation method Methods 0.000 abstract description 15
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 abstract description 12
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 abstract description 11
- 229910052602 gypsum Inorganic materials 0.000 abstract description 11
- 229910052938 sodium sulfate Inorganic materials 0.000 abstract description 11
- 235000011152 sodium sulphate Nutrition 0.000 abstract description 11
- 239000010440 gypsum Substances 0.000 abstract description 10
- 238000004519 manufacturing process Methods 0.000 abstract description 8
- 239000000047 product Substances 0.000 abstract description 7
- 239000006227 byproduct Substances 0.000 abstract description 6
- 229910000029 sodium carbonate Inorganic materials 0.000 abstract description 6
- 235000019738 Limestone Nutrition 0.000 abstract description 3
- 238000001914 filtration Methods 0.000 abstract description 3
- 239000006028 limestone Substances 0.000 abstract description 3
- 239000000843 powder Substances 0.000 abstract description 2
- ZFXVRMSLJDYJCH-UHFFFAOYSA-N calcium magnesium Chemical compound [Mg].[Ca] ZFXVRMSLJDYJCH-UHFFFAOYSA-N 0.000 abstract 1
- 238000002360 preparation method Methods 0.000 abstract 1
- 239000006228 supernatant Substances 0.000 description 32
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 28
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 description 17
- 239000007788 liquid Substances 0.000 description 16
- 229910000019 calcium carbonate Inorganic materials 0.000 description 14
- 239000007787 solid Substances 0.000 description 13
- 230000008569 process Effects 0.000 description 12
- 238000001704 evaporation Methods 0.000 description 10
- 230000008020 evaporation Effects 0.000 description 10
- 239000012265 solid product Substances 0.000 description 10
- 238000005516 engineering process Methods 0.000 description 9
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 8
- 239000003546 flue gas Substances 0.000 description 8
- 239000000203 mixture Substances 0.000 description 7
- 230000006872 improvement Effects 0.000 description 5
- 230000032683 aging Effects 0.000 description 4
- 238000002425 crystallisation Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000010881 fly ash Substances 0.000 description 4
- 238000004065 wastewater treatment Methods 0.000 description 4
- 239000003795 chemical substances by application Substances 0.000 description 3
- 230000008025 crystallization Effects 0.000 description 3
- 239000013505 freshwater Substances 0.000 description 3
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 239000000428 dust Substances 0.000 description 2
- 239000000945 filler Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
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- 230000001376 precipitating effect Effects 0.000 description 2
- 238000004062 sedimentation Methods 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 239000008118 PEG 6000 Substances 0.000 description 1
- 229920002584 Polyethylene Glycol 6000 Polymers 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 229910052925 anhydrite Inorganic materials 0.000 description 1
- 239000002956 ash Substances 0.000 description 1
- 239000004566 building material Substances 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 238000003889 chemical engineering Methods 0.000 description 1
- 238000005352 clarification Methods 0.000 description 1
- 238000005345 coagulation Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 235000013373 food additive Nutrition 0.000 description 1
- 239000002778 food additive Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000012770 industrial material Substances 0.000 description 1
- 239000001095 magnesium carbonate Substances 0.000 description 1
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 1
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 1
- 230000005389 magnetism Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
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- 238000005070 sampling Methods 0.000 description 1
- 230000005476 size effect Effects 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
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Abstract
The utility model provides a system for use desulfurization waste water to prepare nanometer magnesium oxide powder as raw materials, it is through homogeneity, get rid of heavy metal ion, throw sodium sulfate and prepare gypsum byproduct, throw sodium carbonate and prepare limestone byproduct, throw sodium hydroxide and prepare magnesium hydroxide, then prepare magnesium oxide product with magnesium hydroxide after calcining, carry out water treatment through receiving and filtering and reverse osmosis unit at last and obtain the backflow water that accords with the production requirement; the utility model discloses with calcium magnesium ion separation preparation by-product at the in-process of softening desulfurization waste water, realized the comprehensive utilization of resource, accord with energy saving and emission reduction's theory.
Description
Technical Field
The invention belongs to the technical field of desulfurization wastewater treatment, and particularly provides a system for preparing nano magnesium oxide powder by taking desulfurization wastewater as a raw material.
Background
The wet limestone gypsum method flue gas desulfurization is a coal-fired flue gas desulfurization technology commonly applied in China, and the technology accounts for more than 90% of the installed capacity of coal-fired power stations in China. The wet flue gas desulfurization system can produce a certain amount of desulfurization waste water in actual operation, the pH value of desulfurization waste water is generally between 4 ~ 6, contains a large amount of gypsum, fly ash and sulfate suspended particles in the desulfurization waste water, wherein chloride ion concentration can reach 20000mg/L, and the positive ions in the desulfurization waste water are mainly calcium, magnesium ion and a small amount of heavy metal ion. The direct discharge can bring secondary pollution to the environment. At present, the desulfurization wastewater is treated by a chemical precipitation-coagulation clarification process widely at home and abroad, although the process can effectively reduce the content of suspended matters and heavy metals in the wastewater, the treated wastewater still contains a large amount of calcium and magnesium ions, wherein the concentration of the magnesium ions is even up to ten thousand mg/L, and the process has the characteristics of strong corrosivity, easy scaling and the like, and the wastewater cannot reach the recycling standard. The terminal treatment technology of the desulfurization wastewater mainly comprises the steps of carrying out evaporation treatment after concentration and decrement, and finally precipitating dissolved solids in the desulfurization wastewater in a crystal form after the soluble solids are retained in concentrated residual liquid. The method can be divided into multi-stage flash evaporation, multi-effect evaporation, mechanical vapor recompression technology, flue gas evaporation technology and the like according to different heating forms. The flue gas evaporation technology is that the desulfurization waste water is atomized and then sprayed into a flue between an air preheater of a coal-fired power plant boiler and an electric dust remover, or a part of hot flue gas and the desulfurization waste water are introduced from the front of the air preheater and enter a bypass evaporation device together, the waste water is completely evaporated by utilizing the heat of the flue gas, pollutants in the waste water are converted into solid substances such as crystals or salts and the like, and the solid substances are collected by the electric dust remover along with fly ash in the flue gas, so that the zero discharge of the waste water is realized. The investment and operation cost of the flue evaporation technology are low, the occupied area is extremely small, however, the technology directly sprays high-salt-content acidic wastewater into the flue, so that the corrosion or ash deposition of the downstream flue is easily caused, the quality of the fly ash is reduced, and the comprehensive utilization of the fly ash is influenced. The evaporative crystallization method can recover water resources and crystallized salt, but has extremely high investment and operation cost and large occupied area. Meanwhile, if the recovered crystalline salt is a mixed salt consisting of sodium sulfate and sodium chloride, the value is low. Furthermore, in order to ensure the proper functioning of the evaporative crystallizer and to ensure the quality of the crystallized salts, it is generally necessary to subject the waste water to a strict pretreatment. In a word, the desulfurization wastewater treatment technology needs to develop a technology with lower investment and operation cost and high added value resource utilization.
The nano-scale magnesium oxide has obvious small-size effect, surface effect, quantum size effect and macroscopic tunnel effect, is free from agglomeration after modification treatment, has a plurality of specific functions and important application values in the aspects of optics, catalysis, magnetism, mechanics, chemical engineering and the like, and has very wide prospects. The desulfurization waste water contains a large amount of magnesium ions and can be used as a raw material for preparing magnesium oxide. However, in the existing desulfurization wastewater treatment technologies, the emphasis is generally placed on the softening of desulfurization wastewater, and most of the separated byproducts exist in the form of mixed pug, and then are treated uniformly, so that a magnesium oxide product with high purity cannot be obtained. Gypsum is a chemical substance which is widely applied and can be used as an industrial material and a building material, and can also be used as a cement retarder, a gypsum building product, model making, a medical food additive, sulfuric acid production, paper filler, paint filler and the like; the gypsum and its products have fine sound-proof, heat-insulating and fire-proof properties due to the microporous structure and heat-dewatering property. In the traditional desulfurization wastewater treatment technology, the emphasis is usually placed on wastewater softening, and the obtained by-products are usually treated in a centralized manner in the form of mixed pug, so that a gypsum product with high purity cannot be obtained.
Disclosure of Invention
In order to solve the technical problems, the invention provides a system for preparing magnesium oxide by taking desulfurization wastewater as a raw material, and provides a method for preparing nano-scale magnesium oxide powder by taking desulfurization wastewater as a raw material through stepwise softening.
In order to achieve the technical purpose, the invention adopts the following technical scheme:
the invention comprises the following steps:
the reaction tank 1(5) is used for separating a part of calcium ions, the water inlet of the reaction tank 1(5) is connected with the upper part of the precipitation reaction tank, and the water outlet of the reaction tank 1(5) is connected with the tubular membrane 1(7) through a pretreatment water pump (6). If the concentration of calcium ions in the secondary supernatant is higher than 1000mg/L, adding a sodium hydroxide solution, controlling the pH value to be 7.0, and then adding sodium sulfate solid, wherein the adding amount is as follows: 3(x-1000) mg/L; then adding calcium sulfate, wherein the adding amount of the calcium sulfate is 1% of the solid sodium sulfate; x is the concentration of calcium ions and the unit of mg/L; and if the concentration of calcium ions in the secondary supernatant is lower than 1000mg/L, controlling the pH value to be 7.0 by using a sodium hydroxide solution, and then carrying out solid-liquid separation by using a tubular membrane 1(7) to obtain a mud-water mixture and a tertiary supernatant.
And the reaction tank 2(9) is used for separating residual calcium ions, the water inlet of the reaction tank 2(9) is connected with the tubular membrane 1(7), and the water outlet of the reaction tank 2(9) is connected with the filter tank (11) through a calcium removal water pump (10). Adding a sodium carbonate solution to generate calcium carbonate precipitate, and after the reaction is completed, carrying out solid-liquid separation by using a filter tank (11) to obtain a four-stage supernatant and a calcium carbonate solid product.
The reaction tank 3(12) is used for separating magnesium ions, the water inlet of the reaction tank 3(12) is connected with the lower part of the filter tank (11), and the water outlet of the reaction tank 3(12) is connected with the tubular membrane 2(14) through a magnesium removal water pump (13). Adding sodium hydroxide solution to generate magnesium hydroxide precipitate, and separating from the system.
As a further improvement of the invention, the pretreatment unit comprises a homogenizing tank (2), a precipitation reaction tank (3) and a plate-and-frame filter press 1 (4); the water inlet of the homogenizing tank (2) is communicated with the desulfurizing tower (1) through a desulfurizing waste water pipeline, and the water outlet of the homogenizing tank (2) is connected with the precipitation reaction tank (3). The lower part of the precipitation reaction tank (3) is connected with a plate-and-frame filter press 1(4), and a water outlet is connected with a reaction tank 1 (5). Because a plurality of insoluble substances exist in the desulfurization wastewater directly discharged from the desulfurization tower, and certain fluctuation exists in water quality and water quantity, a homogenizing pool is required to be used for homogenizing, insoluble substances in the desulfurization wastewater are precipitated to obtain primary precipitates, and the primary supernatant is introduced into a next-stage reaction device to remove the influence of the substances on subsequent reactions. Adding a heavy-duty agent into the precipitation reaction tank to generate precipitation, fully aging, and performing solid-liquid separation to obtain a secondary supernatant. The precipitation reaction tank is used for removing heavy metal ions.
As a further improvement of the invention, the calcium ion removal unit comprises a reaction tank 1(5), a pretreatment water pump (6), a calcium removal water pump (10), a tubular membrane 1(7) and a plate-and-frame filter press 2(8), a reaction tank 2(9) and a filter tank (11). The water inlet of the reaction tank 1(5) is connected with the upper part of the sedimentation reaction tank (3), and the water outlet of the reaction tank 1(5) is connected with the tubular membrane 1(7) through a pretreatment water pump (6). The sludge discharge port of the tubular membrane 1(7) is connected with the plate-and-frame filter press 2(8), the water inlet of the reaction tank 2(9) is connected with the tubular membrane 1(7), and the water outlet of the reaction tank 2(9) is connected with the filter tank (11) through a water pump (10) for removing calcium. Firstly, sodium sulfate with low price is selected in a reaction tank 1(5) to remove partial calcium ions, and then solid-liquid separation is carried out through a tubular membrane 1(7) to obtain a mud-water mixture and a third-level supernatant. Adding a sodium carbonate solution into the reaction tank 2(9) to generate calcium carbonate precipitate, and after the reaction is completed, performing solid-liquid separation by using a filter tank (11) to obtain four-stage supernatant and a calcium carbonate solid product.
As a further improvement of the invention, the magnesium ion removal unit comprises a reaction tank 3(12), a tubular membrane 2(14), a plate-and-frame filter press 3 (15); a disc dryer (16), a rotary calciner (17) and a nano-mill (18). The water inlet of the reaction tank 3(12) is connected with the lower part of the filter tank (11), sodium hydroxide solution and dispersant are added into the reaction tank 3(12) to generate magnesium hydroxide precipitate, and the water outlet of the reaction tank 3(12) is connected with the tubular membrane 2(14) through a magnesium removal water pump (13). The sludge discharge port of the tubular membrane 2(14) is connected with a plate-and-frame filter press 3(15), and then enters a disc type dryer (16), a rotary calcining furnace (17) and a nano grinder (18) for pressure filtration, drying, calcining and grinding to obtain the nano magnesium oxide.
As a further improvement of the invention, the desalting unit comprises a nanofiltration device (20), a nanofiltration water pump (21), a reverse osmosis device (22) and a high-salinity wastewater evaporator (23). The water inlet side of the nanofiltration device (20) is connected with the tubular membrane concentration tank 2(14), the water outlet side of the nanofiltration device (20) is connected with the water inlet side of the reverse osmosis device (22) through a nanofiltration water pump (21), and concentrated water obtained by the nanofiltration device (20) and the reverse osmosis device (22) enters the high-salinity wastewater evaporator (23). After the five-level supernatant passes through a nanofiltration device and a reverse osmosis device, fresh water with standard water quality is obtained on a water production side and can be used as production water for backflow, and solid mixed salt is obtained by evaporation and crystallization on a concentrated water side for comprehensive utilization.
Compared with the prior art, the invention has the following technical effects:
the invention softens the desulfurization wastewater by a step treatment method, recovers byproducts at all levels in the softening process, particularly prepares high-purity magnesium oxide, gypsum and limestone, realizes the comprehensive utilization of resources, and ensures that the quality of the treated wastewater completely reaches the standard and can be used as process water for backflow.
According to the invention, a sodium sulfate solution is added in the early stage, so that calcium ions and sulfate ions react to generate calcium sulfate, and then a calcium sulfate solid product, namely a gypsum product, is obtained through dehydration and drying.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a process flow diagram of the present invention.
In the drawings: 1-a desulfurizing tower; 2-homogenizing pool; 3-a precipitation reaction tank; 4-a plate and frame filter press 1; 5-a reaction tank 1; 6-a pretreatment water pump, 10-a calcium removal water pump, 13-a magnesium removal water pump, 19-a water pump and 21-a nanofiltration water pump; 7-tubular membrane 1; 8-plate and frame filter press 2; 9-reaction tank 2; 11-a filtering tank; 12-reaction tank 3; 14-tubular membrane 2; 15-plate and frame filter press 3; 16-tray dryer; 17-rotary calciner; 18-nano grinder; 20-a nanofiltration device; 22-a reverse osmosis unit; 23-high salt waste water evaporator;
the arrows in the drawing indicate the inflow direction of the material.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention comprises the following steps:
the reaction tank 1(5) is used for separating a part of calcium ions, the water inlet of the reaction tank 1(5) is connected with the upper part of the precipitation reaction tank, and the water outlet of the reaction tank 1(5) is connected with the tubular membrane 1(7) through a pretreatment water pump (6). If the concentration of calcium ions in the secondary supernatant is higher than 1000mg/L, adding a sodium hydroxide solution, controlling the pH value to be 7.0, and then adding sodium sulfate solid, wherein the adding amount is as follows: 3(x-1000) mg/L; then adding calcium sulfate, wherein the adding amount of the calcium sulfate is 1% of the solid sodium sulfate; x is the concentration of calcium ions and the unit of mg/L; and if the concentration of calcium ions in the secondary supernatant is lower than 1000mg/L, controlling the pH value to be 7.0 by using a sodium hydroxide solution, and then carrying out solid-liquid separation by using a tubular membrane 1(7) to obtain a mud-water mixture and a tertiary supernatant.
And the reaction tank 2(9) is used for separating residual calcium ions, the water inlet of the reaction tank 2(9) is connected with the tubular membrane 1(7), and the water outlet of the reaction tank 2(9) is connected with the filter tank (11) through a calcium removal water pump (10). Adding a sodium carbonate solution to generate calcium carbonate precipitate, and after the reaction is completed, carrying out solid-liquid separation by using a filter tank (11) to obtain a four-stage supernatant and a calcium carbonate solid product.
The reaction tank 3(12) is used for separating magnesium ions, the water inlet of the reaction tank 3(12) is connected with the lower part of the filter tank (11), and the water outlet of the reaction tank 3(12) is connected with the tubular membrane 2(14) through a magnesium removal water pump (13). Adding sodium hydroxide solution to generate magnesium hydroxide precipitate, and separating from the system.
The pretreatment unit comprises a homogenizing pool (2), a precipitation reaction pool (3) and a plate-and-frame filter press 1 (4); the water inlet of the homogenizing tank (2) is communicated with the desulfurizing tower (1) through a desulfurizing waste water pipeline, and the water outlet of the homogenizing tank (2) is connected with the precipitation reaction tank (3). The lower part of the precipitation reaction tank (3) is connected with a plate-and-frame filter press 1(4), and a water outlet is connected with a reaction tank 1 (5). Because a lot of insoluble substances and ions capable of generating the insoluble substances exist in the desulfurization wastewater directly discharged from the desulfurization tower, the ions can not contact due to being dispersed at different positions and can not be combined to generate the insoluble substances, a homogenizing tank is required to be used for homogenizing, the ions capable of generating the insoluble substances are combined to generate the insoluble substances, then the insoluble substances are precipitated, and the primary supernatant is guided into a next-stage reaction device to remove the influence of the substances on the subsequent reaction. Adding a heavy-duty agent into the precipitation reaction tank to generate precipitation, fully aging, and performing solid-liquid separation to obtain a secondary supernatant. The precipitation reaction tank is used for removing heavy metal ions.
The calcium ion removal unit comprises a reaction tank 1(5), a pretreatment water pump (6), a calcium removal water pump (10), a tubular membrane 1(7), a plate-and-frame filter press 2(8), a reaction tank 2(9) and a filter tank (11). The water inlet of the reaction tank 1(5) is connected with the upper part of the sedimentation reaction tank (3), and the water outlet of the reaction tank 1(5) is connected with the tubular membrane 1(7) through a pretreatment water pump (6). The sludge discharge port of the tubular membrane 1(7) is connected with the plate-and-frame filter press 2(8), the water inlet of the reaction tank 2(9) is connected with the tubular membrane 1(7), and the water outlet of the reaction tank 2(9) is connected with the filter tank (11) through a water pump (10) for removing calcium. Firstly, sodium sulfate with low price is selected in a reaction tank 1(5) to remove partial calcium ions, and then solid-liquid separation is carried out through a tubular membrane 1(7) to obtain a mud-water mixture and a third-level supernatant. Adding a sodium carbonate solution into the reaction tank 2(9) to generate calcium carbonate precipitate, and after the reaction is completed, performing solid-liquid separation by using a filter tank (11) to obtain four-stage supernatant and a calcium carbonate solid product.
The magnesium ion removal unit comprises a reaction tank 3(12), a tubular membrane 2(14) and a plate-and-frame filter press 3 (15); a disc dryer (16), a rotary calciner (17) and a nano-mill (18). The water inlet of the reaction tank 3(12) is connected with the lower part of the filter tank (11), sodium hydroxide solution and dispersant are added into the reaction tank 3(12) to generate magnesium hydroxide precipitate, and the water outlet of the reaction tank 3(12) is connected with the tubular membrane 2(14) through a magnesium removal water pump (13). The sludge discharge port of the tubular membrane 2(14) is connected with a plate-and-frame filter press 3(15), and then enters a disc type dryer (16), a rotary calcining furnace (17) and a nano grinder (18) for pressure filtration, drying, calcining and grinding to obtain the nano magnesium oxide.
The desalting unit comprises a nanofiltration device (20), a nanofiltration water pump (21), a reverse osmosis device (22) and a high-salinity wastewater evaporator (23). The water inlet side of the nanofiltration device (20) is connected with the tubular membranes 2 and 14, the water outlet side of the nanofiltration device (20) is connected with the water inlet side of the reverse osmosis device (22) through a nanofiltration water pump (21), and concentrated water obtained by the nanofiltration device (20) and the reverse osmosis device (22) enters a high-salinity wastewater evaporator (23). After the five-level supernatant passes through a nanofiltration device and a reverse osmosis device, fresh water with the purity up to the standard is obtained on the water production side and can be used as production water for backflow, and solid mixed salt is obtained by evaporation and crystallization on the concentrated water side for comprehensive utilization.
The process for separating calcium and magnesium from desulfurization wastewater by using the system provided by the invention comprises the following steps:
(1) fully homogenizing the desulfurization wastewater in a homogenizing tank to completely precipitate insoluble matters to obtain primary supernatant; sampling and testing the quality of the primary supernatant, and detecting the concentration of each ion;
(2) leading the primary supernatant into a precipitation reaction tank, adding a recapture agent into the precipitation reaction tank, and generating a precipitate; carrying out solid-liquid separation after full aging to obtain secondary supernatant; the reactions that occur in this process are as follows:
M2++S2-＝MS↓
wherein: m2+Is a heavy metal ion;
(3) introducing the secondary supernatant into a reaction tank 1, and adding the secondary supernatant into the reaction tank 1 at the concentration of 1000mg/L or higher when the calcium ion concentration of the secondary supernatant is higher than that of the secondary supernatantControlling the pH value to be 7.0 by 15 wt% of sodium hydroxide solution, and then adding sodium sulfate solid in the following amount: 3(x-1000) mg/L; then adding calcium sulfate, wherein the adding amount of the calcium sulfate is 1% of the solid sodium sulfate; x is the concentration of calcium ions and the unit of mg/L; if the concentration of calcium ions in the secondary supernatant is lower than 1000mg/L, controlling the pH value to be 7.0 by using a sodium hydroxide solution, and performing solid-liquid separation by using a tubular membrane device to obtain a mud-water mixture and a tertiary supernatant; dehydrating the mud-water mixture to obtain CaSO4·2H2O, containing a small amount of Mg (OH)2；Dehydrating the mud-water mixture to obtain a gypsum product, and introducing the dehydrated water into a homogenizing pool to continuously participate in circulation;
the reactions that occur in this process are as follows:
Ca2++SO4 2-＝CaSO4↓
Mg2++2OH-＝Mg(OH)2↓
(4) introducing the third-level supernatant into a reaction tank 2, and adding a sodium carbonate solution according to the following proportion: the molar ratio of carbonate ions to calcium ions is 1.1-1.3; generating calcium carbonate precipitate, wherein the reaction temperature is 30 ℃ and the reaction time is 40 min; after the reaction is completed, performing solid-liquid separation by using a filter tank 1 to obtain four-stage supernatant and calcium carbonate pug, dehydrating and drying the calcium carbonate pug to obtain a calcium carbonate solid product, and reusing the calcium carbonate solid product in a desulfurization working section of a desulfurization tower; the reactions that occur in this process are as follows:
Ca2++CO3 2-＝CaCO3↓
Mg2++CO3 2-＝MgCO3↓
(5) introducing the four-level supernatant into a reaction tank 3, and adding a sodium hydroxide solution and a PEG-6000 dispersant to generate a magnesium hydroxide precipitate; performing solid-liquid separation by using a tubular membrane device to obtain five-level supernatant; precipitating, filtering, dehydrating and drying to obtain a high-purity magnesium hydroxide solid product; in order to ensure that magnesium ions are completely precipitated, the adding amount of a dispersing agent is 2.5mL/100mL of wastewater, sodium hydroxide is slowly added, the liquid inlet amount of the sodium hydroxide is 6mL/min, the pH value is controlled to be 11.0-11.5, the rotating speed of a stirrer in the reaction process is 600r/min, the stirring time is 30min, the temperature is 60 ℃, and the aging temperature is 60 ℃ after the stirring is finished;
the reactions that occur in this process are as follows:
Mg2++2OH-＝Mg(OH)2↓
(6) drying and calcining the magnesium hydroxide solid product, and grinding the magnesium hydroxide solid product by using a nano grinder to obtain nano magnesium oxide; the calcining temperature is 1600 ℃ and the time is 1.5 h; the reactions that occur in this process are as follows:
(7) after the five-level supernatant passes through a nanofiltration device and a reverse osmosis device, fresh water with the purity up to the standard is obtained on the water production side and can be used as production water for backflow, and solid mixed salt is obtained by evaporation and crystallization on the concentrated water side for comprehensive utilization.
The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.
Claims (3)
1. A system for preparing nano magnesium oxide powder by taking desulfurization wastewater as a raw material is characterized by comprising a pretreatment unit for removing a large amount of heavy metal ions, suspended substances and sulfate ions in the desulfurization wastewater, a calcium ion removal unit for removing calcium ions in the desulfurization wastewater, a magnesium ion removal unit for recovering magnesium ions in the desulfurization wastewater and a desalting unit for recovering salt in the desulfurization wastewater; the pretreatment unit comprises a homogenizing pool (2), a precipitation reaction pool (3) and a plate-and-frame filter press 1 (4); the water inlet of the homogenizing tank (2) is communicated with the desulfurizing tower (1) through a desulfurizing wastewater pipeline, and the water outlet of the homogenizing tank (2) is connected with the precipitation reaction tank (3); the lower part of the precipitation reaction tank (3) is connected with a plate-and-frame filter press 1(4), and a water outlet is connected with a reaction tank 1 (5); the calcium ion treatment unit comprises a reaction tank 1(5), a plate-and-frame filter press 2(8), a reaction tank 2(9) and a filter tank (11); the reaction tank 1(5) is used for separating a part of calcium ions, the water inlet of the reaction tank 1(5) is connected with the upper part of the precipitation reaction tank (3), and the water outlet of the reaction tank 1(5) is connected with the tubular membrane 1(7) through a pretreatment water pump (6); the reaction tank 2(9) is used for separating residual calcium ions, the water inlet of the reaction tank 2(9) is connected with the tubular membrane 1(7), and the water outlet of the reaction tank 2(9) is connected with the filter tank (11) through a calcium removal water pump (10); the calcium ion treatment unit comprises a reaction tank 3(12), a plate-and-frame filter press 3(15), a disc type dryer (16), a rotary calcining furnace (17) and a nano grinder (18); a reaction tank 3(12) for separating magnesium ions, wherein the water inlet of the reaction tank 3(12) is connected with the lower part of the filter tank (11), and the water outlet of the reaction tank 3(12) is connected with the tubular membrane 2(14) through a magnesium removal water pump (13); the desalting unit comprises a nanofiltration device (20), a nanofiltration water pump (21), a reverse osmosis device (22) and a high-salinity wastewater evaporator (23); the water inlet side of the nanofiltration device (20) is connected with the tubular membranes 2 and 14, the water outlet side of the nanofiltration device (20) is connected with the water inlet side of the reverse osmosis device (22) through a nanofiltration water pump (21), and concentrated water obtained by the nanofiltration device (20) and the reverse osmosis device (22) enters a high-salinity wastewater evaporator (23).
2. The system for preparing nano magnesium oxide powder by using desulfurization wastewater as a raw material according to claim 1, wherein the calcium ion removal unit comprises a reaction tank 1(5), a pretreatment water pump (6), a calcium removal water pump (10), a tubular membrane 1(7) and a plate-and-frame filter press 2(8), a reaction tank 2(9) and a filter tank (11); the water inlet of the reaction tank 1(5) is connected with the upper part of the precipitation reaction tank (3), and the water outlet of the reaction tank 1(5) is connected with the tubular membrane 1(7) through a pretreatment water pump (6); the sludge discharge port of the tubular membrane 1(7) is connected with the plate-and-frame filter press 2(8), the water inlet of the reaction tank 2(9) is connected with the tubular membrane 1(7), and the water outlet of the reaction tank 2(9) is connected with the filter tank (11) through a water pump (10) for removing calcium.
3. The system for preparing nano magnesium oxide powder by using desulfurization wastewater as a raw material according to claim 1, wherein the magnesium ion removal unit comprises a reaction tank 3(12), a tubular membrane 2(14), and a plate-and-frame filter press 3 (15); a disc dryer (16), a rotary calciner (17) and a nano-mill (18); adding sodium hydroxide solution and a dispersing agent into the reaction tank 3(12) to generate magnesium hydroxide precipitate; the sludge discharge port of the tubular membrane 2(14) is connected with a plate-and-frame filter press 3(15), and then enters a disc type dryer (16), a rotary calcining furnace (17) and a nano grinder (18) for pressure filtration, drying, calcining and grinding to obtain the nano magnesium oxide.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109231631A (en) * | 2018-10-31 | 2019-01-18 | 华北电力大学（保定） | A kind of system that nanometer magnesia powder is prepared as raw material using desulfurization wastewater |
| CN112960811A (en) * | 2021-03-10 | 2021-06-15 | 上海电力大学 | Resourceful pretreatment system and method for desulfurization wastewater of coal-fired power plant |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109231631A (en) * | 2018-10-31 | 2019-01-18 | 华北电力大学（保定） | A kind of system that nanometer magnesia powder is prepared as raw material using desulfurization wastewater |
| CN112960811A (en) * | 2021-03-10 | 2021-06-15 | 上海电力大学 | Resourceful pretreatment system and method for desulfurization wastewater of coal-fired power plant |
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