Treatment method and treatment system for strong brine in coal chemical industry

Abstract

The invention relates to a coal chemical strong brine treatment method and system, and the treatment method comprises the following steps: carrying out membrane filtration treatment on coal chemical strong brine to obtain filtrate; performing sodium sulfate crystallization treatment on the filtrate to obtain sodium sulfate crystals and first mother liquor; performing sodium chloride crystallization treatment on the first mother liquor to obtain sodium chloride crystals and second mother liquor; carrying out mixed salt crystallization treatment on the second mother solution to obtain a mixed salt crystal and a third mother solution; at least part of the third mother liquor is subjected to solvent removal treatment, and solid carnallite is obtained; and preparing the solid carnallite into the ceramsite filter material. According to the treatment method of the coal chemical strong brine in the embodiment, a method of sodium sulfate crystallization, sodium chloride crystallization and mixed salt crystallization is adopted, salt in the strong brine is separated to the maximum extent, and generated carnallite is prepared into a ceramsite filter material for use, so that the carnallite is harmless and recycled.

Description

Technical Field

[0001] The invention relates to the treatment of concentrated brine, and in particular to a method for treating concentrated brine in coal chemical industry. Background Art

[0002] The composition of coal chemical brine is complex. In addition to a large amount of chloride, sulfate, and nitrate, it also contains other organic and inorganic components, which makes it difficult to treat. At present, the treatment of brine basically adopts the mainstream treatment technology of evaporation + fractionation crystallization, but some organic matter, nitrate and other substances in the crystallization feed cannot be crystallized and can only be separated in the form of miscellaneous salts.

[0003] The relevant regulations clearly state that "the salt mud produced by wastewater treatment that cannot be recycled shall be temporarily managed as hazardous waste; the by-product sold shall meet the applicable product quality standards and ensure that it does not cause environmental problems when used as a product". Therefore, due to its complex composition, it is difficult to recycle the salt, and the industry basically disposes it as hazardous waste. However, due to the high cost of hazardous waste disposal, it has become a bottleneck problem restricting the development of many companies. Summary of the invention

[0004] In order to overcome at least one defect of the above-mentioned prior art, in a first aspect, an embodiment of the present invention provides a method for treating coal chemical concentrated brine, comprising the following steps:

[0005] The coal chemical concentrated brine is subjected to membrane filtration treatment to obtain a filtrate;

[0006] The filtrate is subjected to sodium sulfate crystallization treatment to obtain sodium sulfate crystals and a first mother liquor;

[0007] The first mother liquor is subjected to a sodium chloride crystallization treatment to obtain sodium chloride crystals and a second mother liquor;

[0008] The second mother liquor is subjected to a mixed salt crystallization treatment to obtain mixed salt crystals and a third mother liquor;

[0009] removing the solvent from at least a portion of the third mother liquor to obtain a solid impure salt; and

[0010] The solid miscellaneous salt is made into ceramsite filter material;

[0011] Wherein, the mixed salt crystals include sodium chloride and sodium sulfate.

[0012] In a second aspect, an embodiment of the present invention provides a system for treating concentrated brine in a coal chemical industry, comprising:

[0013] A membrane filtration unit is used to perform membrane filtration treatment on coal chemical concentrated brine to obtain filtrate;

[0014] a sodium sulfate crystallization unit, used for subjecting the filtrate to sodium sulfate crystallization to obtain sodium sulfate crystals and a first mother liquor;

[0015] a sodium chloride crystallization unit, used for subjecting the first mother liquor to sodium chloride crystallization to obtain sodium chloride crystals and a second mother liquor;

[0016] A mixed salt crystallization unit, used for subjecting the second mother liquor to a mixed salt crystallization process to obtain mixed salt crystals and a third mother liquor;

[0017] a solid impure salt preparation unit, used for removing the solvent from the third mother liquid to obtain solid impure salt; and

[0018] The ceramsite filter material preparation unit is used for preparing the ceramsite filter material from the solid impure salt.

[0019] A method for treating concentrated brine in coal chemical industry according to one embodiment of the present invention adopts a method of sodium sulfate crystallization + sodium chloride crystallization + mixed salt crystallization to separate the salt in the concentrated brine to the maximum extent, and the generated mixed salt is made into ceramsite filter material for use, so as to render it harmless and recyclable. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are only used to illustrate specific embodiments and are not to be considered as limiting the present invention.

[0021] Figure 1 The present invention is a process flow chart of a method for treating concentrated brine in coal chemical industry according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] Typical embodiments that embody the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various changes in different embodiments without departing from the scope of the present invention, and the descriptions therein are essentially used as illustrations rather than to limit the present invention.

[0023] One embodiment of the present invention provides a method for treating coal chemical concentrated brine, comprising the following steps:

[0024] S1: treating coal chemical concentrated brine with membrane filtration to obtain filtrate;

[0025] S2: subjecting the filtrate to sodium sulfate crystallization treatment to obtain sodium sulfate crystals and a first mother liquor;

[0026] S3: subjecting the first mother liquor to sodium chloride crystallization to obtain sodium chloride crystals and a second mother liquor;

[0027] S4: subjecting a portion of the second mother liquor to a mixed salt crystallization treatment to obtain mixed salt crystals and a third mother liquor;

[0028] S5: removing the solvent from at least a portion of the third mother liquor to obtain a solid impure salt;

[0029] Among them, the mixed salt crystals include sodium chloride and sodium sulfate.

[0030] In one embodiment, the solid miscellaneous salts can be made into ceramsite filter materials.

[0031] In one embodiment, the COD of the coal chemical concentrated brine is less than 12000 mg / l, and the salt content is greater than 1000 mg / l.

[0032] In one embodiment, in step S1, the coal chemical concentrated brine is first processed through a security filter to remove larger impurities; the treated liquid is then subjected to membrane filtration treatment, and the membrane used in the membrane filtration treatment is a nanofiltration membrane for removing organic matter.

[0033] In one embodiment, the nanofiltration membrane used in the membrane filtration treatment in step S1 is made of polyamide. The pressure resistance of the nanofiltration membrane is: 0≤pressure resistance≤4.5MPa, which is three times that of ordinary nanofiltration membranes, thanks to the fact that the membrane material is polyamide; and the thickness of the supporting layer of the nanofiltration membrane is 80-100 nanometers, which is twice that of ordinary nanofiltration membranes. Such a structure enables the nanofiltration membrane to exhibit excellent performance.

[0034] In one embodiment, the surface of the nanofiltration membrane in step S1 is strongly negatively charged, and the surface charge is 4 times that of ordinary nanofiltration membranes. It can intercept uncharged organic matter with a molecular weight greater than 300, and can also partially intercept negatively charged organic matter with a molecular weight greater than 150.

[0035] In one embodiment, the nanofiltration membrane in step S1 may have a permeability of 10-30% for inorganic salts and a retention rate of 60-70% for COD.

[0036] In one embodiment, the membrane flux of the nanofiltration membrane used in the membrane filtration treatment may be 10 to 30 LMH, the operating pressure may be 0.7 to 2.0 MPa, the operating pH may be 2 to 12, and the inlet water turbidity may be less than 3 NTU.

[0037] In one embodiment, a concentrated solution and a filtrate (purified solution) are obtained through membrane filtration treatment in step S1; the concentrated solution contains most of the COD in the brine and has a low salt content. The concentrated solution can be sent to a sewage biochemical system for treatment to reduce COD, wherein COD is used as a carbon source for the biochemical system, which is more conducive to the stable operation of the biochemical system.

[0038] In one embodiment, in step S2, the filtrate obtained in step S1 is evaporated and concentrated to obtain an evaporated concentrated liquid; the evaporated concentrated liquid is cooled to obtain an evaporated concentrated cooled liquid; the evaporated concentrated cooled liquid is cooled and crystallized to obtain sodium sulfate slurry; the sodium sulfate slurry is thickened and centrifuged to obtain sodium sulfate crystals.

[0039] In one embodiment, the evaporated concentrated liquid can be heat exchanged with circulating cooling water in a precooler to cool the concentrated liquid, for example, the temperature can be reduced from 100°C to about 40°C.

[0040] In one embodiment, the evaporation concentration cooling liquid can be crystallized in a freezing crystallizer, a first circulation pipeline is arranged outside the freezing crystallizer, and a cooler is arranged on the first circulation pipeline; the liquid material in the freezing crystallizer can enter the first circulation pipeline, and re-enter the freezing crystallizer along the first circulation pipeline after being cooled by the cooler. Furthermore, the liquid material in the first circulation pipeline can exchange heat with the ethylene glycol solution through the cooler.

[0041] In one embodiment, the liquid material in the first circulation pipeline can have a small temperature drop (for example, about 0.5°C), which can effectively suppress the wall formation of the heat exchange tubes of the cooler on the one hand; on the other hand, it can ensure that the crystallization process is carried out in the metastable zone, providing good conditions for crystal growth and realizing a continuous and stable low-temperature crystallization process.

[0042] In one embodiment, the evaporation concentration cooling liquid can be passed into the first circulation pipeline, cooled by the cooler and then enter the freezing crystallizer. Further, the sodium sulfate slurry in the freezing crystallizer can be passed into a thickener for thickening, and then separated by a centrifugal dehydrator to obtain sodium sulfate crystals and the first mother liquor.

[0043] In one embodiment, the centrifuged first mother liquor still contains about 2% of suspended solids, and the suspended solids can be separated from the mother liquor by setting a sedimentation tank. Furthermore, the bottom concentrate of the sedimentation tank can be transported to the first circulation pipeline, and the supernatant (frozen mother liquor) of the sedimentation tank overflows into the frozen mother liquor tank, and then is transported to the first mother liquor preheater by a pump. The frozen mother liquor can be preheated by the first mother liquor preheater, for example, the mother liquor temperature is raised from -4.5°C to about 25°C, and the preheated mother liquor is then treated through a nanofiltration security filter to remove suspended matter within 5um. Afterwards, the frozen mother liquor can be further separated by a nanofiltration device, and the resulting nanofiltration concentrated water (concentrated liquid) mainly contains sulfate, which can be recycled; the nanofiltration produced water (filtrate) mainly contains chloride, which is subjected to sodium chloride crystallization treatment.

[0044] In one embodiment, in step S3, the liquid material to be treated is subjected to a volatile removal treatment. Further, the volatiles can be removed by a volatile removal system, which can include a volatile removal tower, a removal tower condenser, a removal tower discharge pump, and a removal tower condensate pump. The liquid material fed can be heated by low-pressure steam and then flashed in the removal tower to separate the volatile organic matter. The secondary steam containing organic matter at the top of the tower can be condensed and sent to the off-site sewage biochemical treatment system by the removal tower condensate pump for treatment.

[0045] In one embodiment, the liquid material discharged from the volatile matter removal system can be transported to the sodium chloride crystallizer to be mixed with the circulating salt slurry in the sodium chloride crystallizer, and a second circulation pipeline is provided outside the sodium chloride crystallizer, and a heater is provided on the second circulation pipeline. The liquid material in the sodium chloride crystallizer can enter the second circulation pipeline, and the circulating salt slurry is heated to a boiling point by heat exchange with the steam in the shell side through the heater, and then enters the sodium chloride crystallizer for flash evaporation, and part of the sensible heat is converted into latent heat to generate secondary steam. With the heating and flash evaporation of the salt slurry, water is removed in the form of steam, and the salt slurry reaches supersaturation, and crystals are precipitated in the crystallizer to form a concentrated salt slurry.

[0046] In one embodiment, the concentrated salt slurry can be passed into a thickener for thickening treatment to increase the concentration of suspended matter in the concentrated salt slurry to more than 40%. Further, the thickened concentrated salt slurry can be subjected to solid-liquid separation by a centrifugal dehydrator (spiral screen centrifuge), and the produced crude sodium chloride solid wet salt has a moisture content of about 5%. Further, the solid wet salt can be transferred to a circulating fluidized bed drying device for drying, and the moisture content of the product salt meets the first-grade standard of refined industrial salt.

[0047] In one embodiment, most of the mother liquor (second mother liquor) after the sodium chloride crystallization treatment is refluxed to the second circulation pipeline for further circulation, concentration and crystallization; in order to ensure the quality of the sodium chloride crystal salt and the long-term stable operation of the crystallizer system, a small amount of the second mother liquor can be subjected to mixed salt crystallization treatment.

[0048] In one embodiment, part of the second mother liquor in step S3 is subjected to a mixed salt crystallization treatment to obtain mixed salt crystals and a third mother liquor (mixed salt mother liquor), wherein the mixed salt includes sodium sulfate and sodium chloride. Further, the mixed salt crystals and the third mother liquor are separated by a dehydrator, and the mixed salt crystals can be returned to step S2 for recycling, and the third mother liquor is dried.

[0049] In one embodiment, the drying process of the third mother liquor can be carried out in a drum dryer, and as the drying process proceeds, the solvent is continuously volatilized to obtain solid impure salts. Since the nitrate concentration in the coal chemical concentrated brine is relatively high, and the solubility of nitrate in aqueous solution is very large, and the solubility increases with the increase of temperature, it is difficult for nitrate to crystallize together during the mixed salt crystallization process, and it will form impure salts together with organic substances and other substances through drying, so the impure salts contain organic matter, nitrates and a small amount of other salts.

[0050] In one embodiment, the impurity salt is a solid product after the evaporation and crystallization mother liquor is treated, which contains not only organic matter but also a certain amount of sulfate, chloride, nitrate, etc. By separating these components from the mother liquor, the generation of hazardous waste can be reduced.

[0051] In one embodiment, the sodium sulfate crystals obtained in step S2 may be processed for resource recovery, for example, the sodium sulfate crystals may be converted into sodium carbonate and ammonium sulfate under the action of carbon dioxide and ammonia.

[0052] In one embodiment, the resource recovery treatment of sodium sulfate crystals includes step (1): configuring the sodium sulfate crystals into a sodium sulfate aqueous solution, introducing ammonia and carbon dioxide into the sodium sulfate solution to undergo a double decomposition reaction, and obtaining sodium bicarbonate solid and double decomposition mother liquor after solid-liquid separation. Sodium bicarbonate solids can be calcined to obtain sodium carbonate. Furthermore, the double decomposition reaction can be carried out at a temperature of 60 to 80°C.

[0053] In one embodiment, the mass concentration of the sodium sulfate aqueous solution may be 10%.

[0054] In one embodiment, the resource recovery process of sodium sulfate crystals further comprises the following steps:

[0055] Step (2): mixing sodium sulfate with the above-mentioned double decomposition mother liquor at 20-40° C. to react to obtain a double salt [Na2SO4·(NH4)2SO4·(1-6)H2O] solid, and obtaining a double salt solid and a saturated solution of sodium after solid-liquid separation; further, the saturated solution of sodium can be used in the double decomposition reaction system of step (1);

[0056] Step (3): preparing the double salt solid into a solution and then performing low-temperature sodium removal to obtain a solid, and obtaining wet salt and sodium removal mother liquor through solid-liquid separation; wherein "low-temperature sodium removal" refers to removing sodium sulfate after lowering the temperature to form sodium sulfate wet salt, the wet salt being composed of sodium sulfate and containing 20-30% of water;

[0057] Step (4): evaporating and crystallizing the sodium-removed mother liquor obtained in step (3), and obtaining ammonium sulfate solid and evaporated mother liquor after solid-liquid separation; the evaporated mother liquor can be reused for the preparation of the double salt solution in step (3);

[0058] Step (5): Dry the wet salt obtained in step (3) to obtain dry salt and condensed water; the obtained dry salt can be reused in step (2), and the obtained condensed water can be reused in the preparation of the complex salt solution in step (3).

[0059] In one embodiment, the sodium chloride crystals obtained in step S3 may be processed for resource recovery, for example, by converting the sodium chloride into hydrochloric acid and sodium hydroxide solution through a bipolar membrane.

[0060] In one embodiment, sodium chloride crystals can be configured into a sodium chloride solution, and then treated with an ion exchange resin to remove divalent or higher cations (such as calcium, magnesium, iron, and zinc) to achieve the following water inlet conditions for the bipolar membrane: SS <1 mg / L, total content of divalent and higher cations <0.3 mg / L, viscosity <10 cpM, and silica <40 mg / l.

[0061] In one embodiment, sodium chloride can be prepared into a solution through a salt dissolving tank, the solvent used can be desalted water, and the mass concentration of the sodium chloride solution can be 10-15%.

[0062] In one embodiment, the mass concentration of the sodium hydroxide solution produced by the bipolar membrane may be 8%, and the mass concentration of the hydrochloric acid may be 7.3%; the dilute brine of the bipolar membrane may be returned to the salt dissolving tank for recycling.

[0063] In one embodiment, the solid impure salt obtained in step S5 can be mixed with auxiliary materials and then calcined to obtain a ceramsite filter material. Further, the auxiliary materials can include fly ash, and the calcination temperature can be 1000-1200° C., for example, 1100° C.; the calcination time can be 11-13 hours, for example, 11.5 hours, 12 hours, 12.5 hours.

[0064] In one embodiment, the specific surface area of ​​the ceramsite filter material is ≥2×10 4 cm 2 / g.

[0065] In one embodiment, under high temperature conditions, the impurity salt is in a molten state and fully merges with the fly ash to form a special structure with high porosity. After calcination, the mass content of the impurity salt in the obtained ceramsite material is ≥40%, the mass content of the fly ash in the obtained ceramsite material is ≥40%, the strength of the ceramsite material is >2MPa, and the heavy metal solidification rate of the material is >95%.

[0066] In one embodiment, the preparation process of ceramsite filter material comprises:

[0067] Mixing the solid miscellaneous salt with auxiliary materials to form a mixture;

[0068] The mixed material is subjected to molding treatment to obtain a green body;

[0069] The green body is dried to obtain a dried green body;

[0070] calcining the dried green body to obtain a ceramic material; and

[0071] The ceramic material is cooled.

[0072] In one embodiment, the preparation process of the mixture includes: respectively sending the required miscellaneous salts and auxiliary materials (fly ash) into an automatic batching system for stirring and mixing in a certain proportion to form a mixture that meets the requirements of ball formation.

[0073] In one embodiment, the preparation process of the green body includes: sending the mixed material to an automatic ball press machine through a conveyor for ball forming. During the ball forming process, the scraps formed are returned to the mixing process for further recycling.

[0074] In one embodiment, the preparation process of ceramsite filter material further includes: forming the pellets and conveying them to a composite screening machine for screening, conveying qualified green body materials to the next process, and conveying unqualified products under the screen to a crushing process for crushing and subsequent reuse.

[0075] In one embodiment, the temperature of the drying process may be 100-140°C, such as 110°C, 120°C, or 130°C.

[0076] In one embodiment, the process of drying the green body includes: sending the formed green balls to a rotary kiln for drying via a belt conveyor, the inlet temperature of the drying chamber is 100-140°C, and the outlet temperature is about 40°C. The heat source for drying the green balls comes from the waste heat of the tail gas of the rotary calcining kiln, which saves energy and protects the environment. The drying time is generally about 2 hours.

[0077] In one embodiment, the roasting process includes: sending the dried spherical material into a rotary calcining kiln through a belt conveyor and mixing it with coke powder added in proportion at the same time, and then directly roasting it. The roasting temperature is 1000-1200°C, and the roasting cycle is about 12 hours, so that the material is ceramicized. The roasting tail gas first enters the bag filter through a heat exchanger to collect dust, and then is sent to the desulfurization and denitrification device through the tail gas main pipe to further remove sulfur-containing tail gas and nitrogen oxides containing sulfur dioxide, sulfur trioxide, etc., and finally the tail gas is washed in a spray tower and discharged in a centralized manner. At the roasting temperature, organic matter will be completely converted into carbon dioxide and water, and nitrates in miscellaneous salts will be converted into oxygen, nitrogen oxides and sodium oxides.

[0078] In one embodiment, the cooling treatment includes: directly sending the calcined material from the rotary calcining kiln into the rotary cooling kiln, and passing circulating cooling water through the outer jacket to cool the material to room temperature.

[0079] In one embodiment, the preparation process of expanded clay filter material further includes: sending the material obtained from the rotary cooling kiln into a screening system by a belt conveyor for grading and screening, selecting product particles of large, medium and small sizes by screening, and then measuring and packaging them separately to become expanded clay products that can be used as resources.

[0080] An embodiment of the present invention provides a system for treating concentrated brine in coal chemical industry, which can be used to implement the above method, including:

[0081] A membrane filtration unit is used to perform membrane filtration treatment on coal chemical concentrated brine to obtain filtrate;

[0082] A sodium sulfate crystallization unit, used for subjecting the filtrate to sodium sulfate crystallization to obtain sodium sulfate crystals and a first mother liquor;

[0083] A sodium chloride crystallization unit, used for subjecting the first mother liquor to sodium chloride crystallization to obtain sodium chloride crystals and a second mother liquor;

[0084] A mixed salt crystallization unit, used for subjecting the second mother liquor to mixed salt crystallization to obtain mixed salt crystals and a third mother liquor;

[0085] a solid impure salt preparation unit, used for removing the solvent from the third mother liquid to obtain solid impure salt; and

[0086] The ceramsite filter material preparation unit is used to prepare ceramsite filter material from solid miscellaneous salts.

[0087] In one embodiment, the processing system further includes a sodium sulfate resource unit for converting sodium sulfate crystals into sodium carbonate and ammonium sulfate. Further, the sodium sulfate resource unit may include a double decomposition reactor, a calciner, a normal temperature crystallizer, a low temperature sodium removal device, a dryer, an evaporative crystallizer, a sodium sulfate bagging machine, and an ammonium sulfate bagging machine connected in sequence.

[0088] In one embodiment, the treatment system further includes a sodium chloride resource unit for converting sodium chloride into hydrochloric acid and sodium hydroxide solution through a bipolar membrane. Further, the sodium chloride resource unit may include a salt dissolving tank, an electrodialysis device, a reverse osmosis device, an ion exchanger, an electrodialysis bipolar membrane, a hydrochloric acid tank, and a sodium hydroxide tank connected in sequence.

[0089] In one embodiment, the solid impurity salt preparation unit comprises a dryer for drying the third mother liquor.

[0090] In one embodiment, the ceramsite filter material preparation unit comprises:

[0091] A batching device, used for mixing solid miscellaneous salt with auxiliary materials to form a mixture;

[0092] A molding device, used for molding the mixed material to obtain a green body;

[0093] A drying device, used for drying the green body to obtain a dried green body;

[0094] A calcining device, used for calcining the dried green body to obtain a ceramic material; and

[0095] The cooling device is used for cooling the ceramic material.

[0096] In one embodiment, the batching device may be an automatic batching system, the forming device may be an automatic ball press, the drying device and the roasting device may both be rotary kilns, and the cooling device may be a rotary cooling kiln.

[0097] In one embodiment, the membrane filtration unit includes a nanofiltration membrane and a security filter, and the types and operating methods of the nanofiltration membrane and the security filter are subject to the aforementioned definitions.

[0098] In one embodiment, the sodium sulfate crystallization unit includes a precooler, a freezing crystallizer, a first circulation pipeline, a cooler, a thickener, a centrifugal dehydrator, a settling tank, a first mother liquor preheater, and a nanofiltration safety filter. The types and operating methods of these devices are subject to the aforementioned limitations.

[0099] In one embodiment, the sodium chloride crystallization unit includes a volatile matter removal system, a sodium chloride crystallizer, a second circulation pipeline, a heater, a thickener, and a centrifugal dehydrator, and the types and operating methods of these devices are subject to the aforementioned limitations.

[0100] In one embodiment, the mixed salt crystallization unit includes a mixed salt crystallizer, a third circulation pipeline, a mixed salt crystallization heater, etc. The devices included in the mixed salt crystallization unit and the operation method thereof may be the same as those of the sodium chloride crystallization unit.

[0101] In one embodiment, the solid miscellaneous salt preparation unit comprises a drum dryer.

[0102] A method for treating concentrated brine in coal chemical industry according to an embodiment of the present invention uses a method of sodium sulfate crystallization + sodium chloride crystallization + mixed salt crystallization to separate the salt in the concentrated brine to the maximum extent, and the produced sodium sulfate and sodium chloride can be recycled, and a small amount of generated miscellaneous salt can be used as a new filter material through calcination. In addition, by completely recycling the miscellaneous salt, waste is turned into treasure, and the recycling of salt is realized.

[0103] A method for treating coal chemical concentrated brine in one embodiment of the present invention prepares solid miscellaneous salts into ceramsite filter media. The filter media product can be used as filter media for sewage treatment biological filter tanks to replace traditional ceramsite filter media. The specific surface area is more than 4 times that of traditional ceramsite filter media. The specific surface area is large, the porosity is high and the filter media is inert, which is conducive to the contact, biofilm formation and growth of microorganisms, can maintain a large amount of microorganisms, is conducive to the mass transfer of oxygen and nutrients required in the metabolism of microorganisms and the waste generated by the metabolism, and has a better treatment effect.

[0104] A method for treating coal chemical concentrated brine in one embodiment of the present invention converts sodium sulfate into sodium carbonate and ammonium sulfate, fully utilizes carbon dioxide, and achieves carbon emission reduction. The produced sodium carbonate and ammonium sulfate can be used as products, thereby increasing the added value of the products.

[0105] A method for treating coal chemical concentrated brine in one embodiment of the present invention converts sodium chloride into hydrochloric acid and caustic soda, which can be used or sold as chemical products, thereby realizing resource utilization of sodium chloride.

[0106] Unless otherwise defined, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0107] The embodiments described in the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Those skilled in the art may make various other substitutions, changes and improvements within the scope of the present invention. Therefore, the present invention is not limited to the above embodiments, but is only limited by the claims.

Claims

1. A method for treating concentrated brine in coal chemical industry, comprising the following steps: The coal chemical concentrated brine is subjected to membrane filtration treatment to obtain a filtrate; The filtrate is subjected to sodium sulfate crystallization treatment to obtain sodium sulfate crystals and a first mother liquor; The first mother liquor is subjected to a sodium chloride crystallization treatment to obtain sodium chloride crystals and a second mother liquor; The second mother liquor is subjected to a mixed salt crystallization treatment to obtain mixed salt crystals and a third mother liquor; removing the solvent from at least a portion of the third mother liquor to obtain a solid impure salt; as well as The solid miscellaneous salt is made into ceramsite filter material; Wherein, the mixed salt crystals include sodium chloride and sodium sulfate.

2. The processing method according to claim 1, wherein: Using a nanofiltration membrane to perform the membrane filtration treatment; and / or, converting the sodium sulfate crystals into sodium carbonate and ammonium sulfate under the action of carbon dioxide and ammonia; and / or, converting the sodium chloride crystals into hydrochloric acid and caustic soda via a bipolar membrane; and / or, The solid impure salt is mixed with auxiliary materials to form a mixture and then calcined to obtain the ceramsite filter material.

3. The processing method according to claim 2, wherein: The coal chemical concentrated brine is first processed through a security filter and then processed through the nanofiltration membrane; and / or, The process of converting the sodium sulfate into sodium carbonate and ammonium sulfate comprises: preparing the sodium sulfate crystals into a sodium sulfate aqueous solution, introducing ammonia and carbon dioxide into the sodium sulfate solution to undergo a double decomposition reaction, and obtaining a solid product; Then, solid-liquid separation is performed to obtain sodium bicarbonate solid and double decomposition mother liquor; and the sodium bicarbonate solid is calcined to obtain sodium carbonate.

4. The processing method according to claim 2, wherein: The auxiliary material includes fly ash; and / or, The calcination temperature is 1000-1200°C; and / or, The specific surface area of ​​the ceramsite filter material is ≥2×10 4 cm 2 / g.

5. The processing method according to claim 1, wherein: The preparation process of the ceramsite filter material comprises: Mixing the solid miscellaneous salt with auxiliary materials to form a mixture; The mixed material is subjected to a molding process to obtain a green body; The green body is dried to obtain a dried green body; calcining the dried green body to obtain a ceramic material; and The ceramic material is subjected to a cooling treatment.

6. The processing method according to claim 1, wherein: The material of the membrane used in the membrane filtration treatment is polyamide; and / or, The membrane flux of the membrane used in the membrane filtration treatment is 10-30LMH, and the operating pressure is 0.7-2.0MPa.

7. A system for treating concentrated brine in coal chemical industry, comprising: A membrane filtration unit is used to perform membrane filtration treatment on coal chemical concentrated brine to obtain filtrate; a sodium sulfate crystallization unit, used for subjecting the filtrate to sodium sulfate crystallization to obtain sodium sulfate crystals and a first mother liquor; a sodium chloride crystallization unit, used for subjecting the first mother liquor to sodium chloride crystallization to obtain sodium chloride crystals and a second mother liquor; A mixed salt crystallization unit, used for subjecting the second mother liquor to a mixed salt crystallization process to obtain mixed salt crystals and a third mother liquor; A solid impure salt preparation unit, used for removing the solvent from the third mother liquor to obtain solid impure salt; as well as The ceramsite filter material preparation unit is used for preparing the ceramsite filter material from the solid impure salt.

8. The treatment system according to claim 7, further comprising a sodium sulfate resource recovery unit for converting the sodium sulfate into sodium carbonate and ammonium sulfate; and / or, The invention also comprises a sodium chloride resource recovery unit, which is used for converting the sodium chloride into hydrochloric acid and sodium hydroxide solution through a bipolar membrane.

9. The processing system according to claim 7, wherein: The membrane filtration unit comprises a nanofiltration membrane and a security filter; and / or, The solid impurity salt preparation unit comprises a dryer for drying the third mother liquor.

10. The processing system according to claim 7, wherein: The ceramsite filter material preparation unit comprises: A batching device, used for mixing the solid impurity salt with auxiliary materials to form a mixture; A molding device, used for molding the mixed material to obtain a green body; A drying device, used for drying the green body to obtain a dried green body; A calcining device, used for calcining the dried green body to obtain a ceramic material; and The cooling device is used for cooling the ceramic material.

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