Nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coal mine water

Abstract

A nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coal mine water comprises a desalting device, a secondary concentration device and an evaporative crystallization device, the desalting device comprises an adjusting tank, a sedimentation tank, a filter tank, a ceramic ultrafiltration device, a first reverse osmosis device and a concentrated brine tank which are sequentially connected, and an outlet of the first reverse osmosis device is connected with a water producing tank; the secondary concentration device comprises a clarification tank, a multi-medium filter, an ion exchanger, a softening water production tank, a decarburization device and a reverse osmosis device II which are connected in sequence, and an inlet of the clarification tank is connected with an outlet of a concentrated brine tank; the evaporative crystallization device comprises a concentrated water tank, a catalytic oxidation device, an evaporator, a sodium sulfate evaporative crystallization device, an ultrafiltration device, a nanofiltration device and a sodium chloride evaporative crystallization device which are connected in sequence; an inlet of the concentrated water tank is connected with an outlet of the reverse osmosis device II. According to the utility model, the treatment processes of desalination, secondary concentration and salt separation are adopted to realize the complete resource utilization of the coal mine water, and the zero emission requirement is met.

Description

Technical Field

[0001] The utility model belongs to the field of wastewater salt treatment, and in particular relates to a nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coal mine water. Background Art

[0002] Mine water is composed of groundwater, underground dust prevention water, equipment cooling water, etc. that enters the underground tunnels during coal mining. Affected by the mining area's geographical environment, coal seam mineral composition, and hydrogeological conditions, it can be divided into suspended solids wastewater and high-mineralization wastewater (i.e. high-salt mine water) according to its water quality characteristics.

[0003] High-salinity mine water is mainly distributed in the northwest and northern mining areas of my country. These areas generally have large-scale coal chemical enterprises based on coal mining production: the local scarce water resources have become an important factor restricting the development of the coal chemical industry. After conventional treatment, part of the high-salinity mine water in coal mines is reused for the production of coal mines themselves. The remaining large amount of rich water cannot be reused because the salt content is far higher than the water quality index of coal chemical enterprises. If it is directly discharged, it will not only waste water resources, but also harm the originally fragile ecological environment of the local area. Therefore, it is particularly urgent and necessary to deeply treat the high-salinity mine water and make resource utilization.

[0004] In addition to using conventional processes for pretreatment, the key to resource utilization of high-mineralized mine water is to carry out desalination treatment to make the water quality meet the requirements of production or life. To achieve zero emissions, it is necessary to further treat the concentrated water produced by desalination to achieve complete separation of water and impurities and utilize them separately. The deep treatment and resource utilization of high-salt water is an emerging technology that combines multidisciplinary applications such as water treatment and chemical industry. It is difficult and has a long process chain. It is widely used in coal chemical wastewater, landfill leachate and other industries in China. High-salt mine water mostly draws on the treatment technology and engineering experience of these industries, and the treatment process based on its own water quality characteristics is rarely used in practice. Utility Model Content

[0005] In view of the above-mentioned problems, the utility model provides a nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coal mine water. The system can effectively recover salts in highly mineralized groundwater. The use of quality-differentiation and utilization technology can reduce the processing cost to the greatest extent and achieve zero emission requirements. It is also safe, stable and reliable in operation and has strong resistance to shock loads.

[0006] In order to achieve the above-mentioned invention object, the utility model adopts the following technical scheme: a nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coal mine water, characterized in that it includes a desalting device, a secondary concentration device and an evaporation crystallization device; the desalting device includes a regulating tank, a sedimentation tank, a filter tank, a ceramic ultrafiltration device, a reverse osmosis device and a concentrated brine tank connected in sequence, and the outlet of the reverse osmosis device is connected to a water production tank; the secondary concentration device includes a clarification tank, a multi-media filter, an ion exchanger, a softening water production tank, a decarbonization device and a reverse osmosis device 2 connected in sequence, and the inlet of the clarification tank is connected to the outlet of the concentrated brine tank; the evaporation crystallization device includes a concentrated water tank, a catalytic oxidation device, an evaporator, a sodium sulfate evaporation crystallization device, an ultrafiltration device, a nanofiltration device and a sodium chloride evaporation crystallization device connected in sequence, and the inlet of the concentrated water tank is connected to the outlet of the reverse osmosis device 2.

[0007] Preferably, the filter tank is a V-shaped filter tank.

[0008] Preferably, the ion exchanger is a weak acid cation exchanger.

[0009] Preferably, the catalytic oxidation device is an AOP catalytic oxidation device.

[0010] Preferably, the evaporator is an MVR evaporator.

[0011] The working principle of the utility model is as follows: the mine water first enters the regulating tank to remove large suspended particles in the water, coagulants and flocculants are added in the sedimentation tank to remove most of the suspended particles, the sedimentation tank is discharged, and small fine particles are further removed through the V-type filter tank, and bactericides are added through the ceramic ultrafiltration device to remove colloids, bacteria and other substances, and then enter the reverse osmosis device 1, and reducing agents, scale inhibitors and non-oxidizing bactericides are added to produce water for reuse, and the concentrated brine enters the contact clarification tank from the concentrated brine pool, and alkali, flocculants and the like are added to further remove most of the hardness and suspended particles in the water, and after the effluent is disinfected and neutralized, it passes through a multi-media filter, an ion exchanger and the like, and then enters the reverse osmosis device 2 to produce water for reuse. The secondary concentrated super-concentrated brine passes through the catalytic oxidation device and the evaporator in turn and then enters the sodium sulfate evaporation and crystallization device. The MVR concentrate is evaporated and crystallized to obtain sodium sulfate crystals. The sodium sulfate mother liquor adopts membrane salt separation technology. This technology utilizes the selective permeability of the nanofiltration membrane and uses a special wide flow channel and highly pollution-resistant special nanofiltration separation membrane to effectively separate the monovalent salt and divalent salt in the solution. The nanofiltration water enters the subsequent sodium chloride evaporation and crystallization device.

[0012] The utility model has the following advantages and positive effects:

[0013] 1. The desalination device described in the utility model includes a regulating tank, a sedimentation tank, a V-type filter tank, a ceramic ultrafiltration device, a reverse osmosis device and a concentrated brine tank connected in sequence, which can be used to reduce the salt content of raw water, produce qualified product water, and remove most suspended matter, colloids, bacteria, etc. The sedimentation tank + filter tank (tank combination) occupies a small area, has low investment, low operating cost, is easy to operate, has its own mud discharge, strong impact load resistance, and good treatment effect.

[0014] 2. The secondary concentration device described in the utility model includes a clarification tank, a multi-media filter, a weak acid cation exchanger, a softening water production tank, a decarbonization device and a reverse osmosis device connected in sequence, which can further remove most of the hardness and suspended particles of the water, soften, remove silicon, decarbonize and remove alkalinity.

[0015] 3. The evaporation crystallization device described in the utility model includes a concentrated water pool, an AOP catalytic oxidation device, an MVR evaporator, a sodium sulfate evaporation crystallization device, an ultrafiltration device, a nanofiltration device and a sodium chloride evaporation crystallization device connected in sequence, which are used to remove organic matter, continue to concentrate high-concentration brine, separate to obtain solid salt, etc. The membrane salt separation and crystallization salt has high quality.

[0016] 4. The utility model adopts ultrafiltration and reverse osmosis double membrane method, which has high water production rate, low operating cost, high operation requirements, strong anti-pollution ability and low scaling risk. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the utility model. DETAILED DESCRIPTION

[0018] The present invention will be further described below with reference to the accompanying drawings and in combination with embodiments.

[0019] Referring to the attached drawings, the utility model provides a nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coal mine water, the system comprising a desalting device 1, a secondary concentration device 2 and an evaporation crystallization device 3. The desalting device comprises a regulating tank, a sedimentation tank, a V-type filter, a ceramic ultrafiltration device, a reverse osmosis device 1 and a concentrated brine pool connected in sequence, and the outlet of the reverse osmosis device 1 is connected to a water production pool; the secondary concentration device comprises a clarification tank, a multi-media filter, a weak acid cation exchanger, a softening water production pool, a decarbonization device and a reverse osmosis device 2 connected in sequence, and the inlet of the clarification tank is connected to the outlet of the concentrated brine pool; the evaporation crystallization device comprises a concentrated water pool, an AOP catalytic oxidation device, an MVR evaporator, a sodium sulfate evaporation crystallization device, an ultrafiltration device, a nanofiltration device and a sodium chloride evaporation crystallization device connected in sequence, and the inlet of the concentrated water pool is connected to the outlet of the reverse osmosis device 2.

[0020] The regulating tank and sedimentation tank are used to regulate the incoming water, and remove larger particle impurities and most suspended solids by adding chemical agents. The filter tank is a pretreatment facility for filtration and backwashing. The ceramic ultrafiltration device and reverse osmosis device can separate bacteria, colloids, suspended impurities and solution solute membrane separation. The main purpose of the clarification tank is to produce precipitation and achieve the effect of solid-liquid separation. The multi-media filter can further remove the residual suspended solids entering the system. The weak acid cation exchanger is the second-stage hardness removal unit of reverse osmosis. After two-stage hardness removal, the hardness removal rate is 99%. The effluent after pretreatment and hardness removal enters the decarbonization tower to remove the remaining alkalinity, further reducing the risk of scaling. The softening water production pool uses lime softening and ion exchange to remove the hardness in the water. Under high pH conditions, reverse osmosis is used to remove most of the salt. The recovery rate of reverse osmosis can be increased to more than 80%. The catalytic oxidation device can remove organic matter in the water and prevent the uncertainty of COD. The MVR evaporator is used to continue the concentration process of high-concentration brine, recover product water and complete solid-liquid separation. The nanofiltration device can achieve the purpose of separating sodium chloride and sodium sulfate in high salt water.

[0021] The workflow of this utility model is:

[0022] 1. After the raw water from the mine passes through the regulating tank, PAC and PAM are added to the sedimentation tank to remove most of the suspended solids, and the effluent SS is <10mg / L; the fine particles are further removed through the V-type filter, and the produced water SS is <1mg / L. After the ultrafiltration device adds bactericides to remove colloids, bacteria and other substances, the produced water turbidity is <0.1NTU, SDI <3, and after entering the reverse osmosis device, reducing agents, scale inhibitors and non-oxidizing bactericides are added, the produced water is reused, and the concentrated brine enters the secondary concentration.

[0023] 2. Desalination water enters the contact clarification tank from the concentrated brine pool, and sodium hydroxide, lime, soda, and flocculants are added to remove most of the hardness and suspended particles in the water. After the effluent is disinfected with sodium hypochlorite and the pH value is adjusted with hydrochloric acid, it is further removed by a multi-media filter and an ion exchanger to remove the remaining suspended matter and hardness. After decarbonation and alkalinity, it enters the reverse osmosis device, where reducing agents, scale inhibitors, and non-oxidizing bactericides are added. The produced water is reused, and the super-concentrated brine enters evaporation and crystallization. A security filter is provided at the front end of the reverse osmosis device to intercept abnormal impurities in the front-end water.

[0024] The mud cake produced in the clarification tank is mainly composed of calcium carbonate, magnesium hydroxide and a small amount of calcium sulfate and other precipitation products after the reaction of adding drugs, and can be treated as general solid waste.

[0025] The backwash, regeneration and flushing drainage of the multi-media filter, weak acid cation exchanger and reverse osmosis device is collected uniformly and returned to the contact clarifier. The sludge discharged from the clarifier is concentrated in the sludge thickening tank and then dehydrated by the sludge thickening and dehydrating machine. Finally, the mud cake and chemical waste residue are treated uniformly.

[0026] 3. Secondary concentration of super concentrated brine passes through the advanced catalytic oxidation unit (AOP), mechanical vapor recompression unit (MVR), Na 2 SO 4 And NaCl evaporation crystallization unit, membrane salt separation unit and mixed salt drying unit. The incoming water (secondary concentrated super brine) enters the AOP unit, and the organic matter in the high brine is removed through advanced oxidation, reducing the amount of water entering MVR and Na 2 SO 4 The organic matter content of the evaporation crystallization unit is reduced to 150mg COD of the effluent, less than 10 times the chromaticity, and SS <1mg, thereby improving the purity of the crystallized salt. The high-salt water in the mine treated by AOP enters the MVR unit for concentration, Na 2 SO 4 The evaporation crystallization unit evaporates the MVR concentrate and precipitates the evaporation crystals, which are packaged after drying. The quality of the crystallized salt meets the requirements of GB / T 6009-2014 Industrial Anhydrous Na 2 SO 4 Class I first-class product requirements. Continuous external discharge of Na 2 SO 4 The evaporated mother liquor enters the membrane separation unit. The membrane separation device adopts nanofiltration salt separation technology. 2 SO 4 After the crystallization mother liquor is pre-treated to remove suspended solids, it is then ultrafiltered to remove most of the COD and macromolecular organic matter, and finally the NaCl and Na 2 SO 4 Separate the quality and salt. Contains more SO 4 2- The nanofiltration concentrated water is returned to the front-end AOP unit for treatment, and the nanofiltration produced water containing more Cl- enters the NaCl evaporation crystallization unit; the NaCl evaporation crystallization unit evaporates the nanofiltration produced water and precipitates NaCl crystals, which are packaged after drying. The quality index of the crystallized salt meets the requirements of GB / T5462-2015 industrial dry salt first-class product. At the same time, the NaCl evaporation mother liquor is continuously discharged to the impurity salt drying unit to ensure Na 2 SO 4 The Na precipitated from the evaporation crystallization unit and the NaCl evaporation crystallization unit 2 SO 4 and NaCl crystal purity.

[0027] Ultrafiltration and nanofiltration concentrated water flows back to the front-end catalytic oxidation unit. 2 SO 4When the crystallization mother liquor, silicon and COD accumulate to the point where they affect the quality of the crystallized salt, the mother liquor can be sent directly to the impurity salt drying device through a bypass, and the sodium chloride crystallization mother liquor is discharged to the impurity salt drying device according to the amount of impurity ions enriched in the mother liquor. The device evaporates the liquid in a scraper film evaporator, and after reaching a certain concentration, it is dried by a rake dryer. After drying, the moisture content is <0.2% and is sent to the impurity salt silo by a belt conveyor.

[0028] The embodiments of the present application are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present application should be included in the scope of protection of the present application.

Claims

1. A nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coal mine water, characterized by: It comprises a desalination device, a secondary concentration device and an evaporation crystallization device; the desalination device comprises a regulating tank, a sedimentation tank, a filter tank, a ceramic ultrafiltration device, a reverse osmosis device 1 and a concentrated brine tank which are connected in sequence, and the outlet of the reverse osmosis device 1 is connected to a water production tank; the secondary concentration device comprises a clarification tank, a multi-media filter, an ion exchanger, a softening water production tank, a decarbonization device and a reverse osmosis device 2 which are connected in sequence, and the inlet of the clarification tank is connected to the outlet of the concentrated brine tank; the evaporation crystallization device comprises a concentrated water tank, a catalytic oxidation device, an evaporator, a sodium sulfate evaporation crystallization device, an ultrafiltration device, a nanofiltration device and a sodium chloride evaporation crystallization device which are connected in sequence, and the inlet of the concentrated water tank is connected to the outlet of the reverse osmosis device 2.

2. A nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coal mine water according to claim 1, characterized in that: The filter tank adopts a V-shaped filter tank.

3. A nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coal mine water according to claim 1, characterized in that: The ion exchanger is a weak acid cation exchanger.

4. A nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coal mine water according to claim 1, characterized in that: The catalytic oxidation device adopts an AOP catalytic oxidation device.

5. A nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coal mine water according to claim 1, characterized in that: The evaporator is an MVR evaporator.

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