A reverse osmosis membrane crystallization treatment device and a reverse osmosis crystallization treatment method

Abstract

The application discloses a kind of reverse osmosis membrane crystallization processing equipment and reverse osmosis crystallization processing method.The reverse osmosis membrane crystallization processing equipment includes sequentially communicating feed liquid tank, feed pump, high-pressure pump, reverse osmosis membrane assembly, crystallization device and dehydration device, and dosing device communicated with feed liquid tank.Reverse osmosis crystallization processing using the equipment of the application can realize the further concentration of the salt-containing feed liquid to be processed at a higher salinity, and the crystallization reaction under normal temperature conditions, and can reduce operating costs.

Description

TECHNICAL FIELD

[0001] The present application relates to a reverse osmosis membrane crystallization treatment equipment and a reverse osmosis crystallization treatment method. BACKGROUND

[0002] In the production processes of petrochemical industry, coal chemical industry, power, steel and seawater desalination, a large amount of salt-containing wastewater will be produced. In order to reduce the amount of effluent and improve the efficiency of water use, the salt-containing wastewater is generally treated by membrane method mainly using reverse osmosis for reuse, which improves the efficiency of water use to a certain extent.

[0003] CN208071390U discloses a reverse osmosis system, which comprises a first reverse osmosis unit (1-1) and a second reverse osmosis unit (2-1), the first reverse osmosis unit (1-1) comprises a reverse osmosis inlet A1, a concentrated water outlet B1 and a water production outlet C1, and the second reverse osmosis unit (2-1) comprises a reverse osmosis inlet A2, a concentrated water outlet B2 and a water production outlet C2; wherein the reverse osmosis inlet A1 of the first reverse osmosis unit (1-1) is in communication with the raw water pipeline, the water production outlet C1 of the first reverse osmosis unit (1-1) is in communication with the reverse osmosis inlet A2 of the second reverse osmosis unit (2-1), and the concentrated water outlet B2 of the second reverse osmosis unit (2-1) is in communication with the reverse osmosis inlet A1 of the first reverse osmosis unit (1-1), so that the water produced from the first reverse osmosis unit (1-1) enters the second reverse osmosis unit (2-1) for treatment, and the concentrated water produced from the second reverse osmosis unit (2-1) is recycled to the first reverse osmosis unit (1-1) for treatment; wherein the apparent rejection rate of the first reverse osmosis unit (1-1) is less than the apparent rejection rate of the second reverse osmosis unit (2-1). However, this system is mainly used for concentrating treatment of raw material liquid with relatively low salt content (salinity 1%-7%), and cannot realize crystallization separation of inorganic salt components.

[0004] “High-salt wastewater salt separation crystallization process and its technical and economic analysis” by Xiong Rihua, He Can, et al., Coal Science and Technology, Vol. 46, No. 9, September 2018, discloses a membrane salt separation crystallization process design. In order to improve the salt recovery rate of the salt separation crystallization process and reduce the amount of generated and disposal cost of mixed salt solid waste, a nanofiltration-low temperature crystallization route is used to design the process for the above pretreated wastewater. However, this technical route uses thermal evaporation crystallization, which has problems of easy corrosion of equipment, high investment and operation cost, etc.

[0005] "Application of membrane concentration technology in zero discharge of high-salinity wastewater" He Can, Liu Zhao-feng, et al., Modern Chemical Industry, Vol. 29, No. 10, October 2019, which discloses the characteristics of three membrane concentration technologies, reverse osmosis, forward osmosis and electrodialysis. However, these membrane concentration technologies are mainly used for concentrating treatment of high-salinity wastewater, and need to be combined with evaporation crystallization treatment to realize the crystallization separation of inorganic salt components.

[0006] "Application of evaporation crystallization technology in zero discharge of high-salinity wastewater" Wang Dan, et al., China Salt, Vol. 45, which discloses the evaporation crystallization technology. However, it has problems such as easy corrosion of equipment, high investment and operation cost, etc.

[0007] Therefore, in the case of requiring zero liquid discharge, high-salinity wastewater is finally treated by evaporation crystallization to obtain distilled water and solid impure salt. However, the investment and operation cost of the evaporation crystallization device are extremely high, which causes great burden to enterprises. SUMMARY

[0008] In view of the above problems existing in the prior art, the present application provides a new reverse osmosis membrane crystallization treatment device and a reverse osmosis crystallization treatment method. The device can realize further concentration of the to-be-treated salt-containing feed liquid (to-be-crystallized feed liquid) at a higher salinity, realize crystallization reaction under normal temperature conditions, and reduce the operation cost.

[0009] The first aspect of the present application provides a reverse osmosis membrane crystallization treatment device, comprising: a feed liquid tank, a feed pump, a high-pressure pump, a reverse osmosis membrane assembly, a crystallization device and a dewatering device connected in sequence, and a dosing device connected with the feed liquid tank, wherein,

[0010] The dosing device is used for adding an inorganic salt stabilizer to the feed liquid tank;

[0011] The feed liquid tank is used for storing the to-be-treated salt-containing feed liquid, and mixing the inorganic salt stabilizer with the feed liquid in the feed liquid tank;

[0012] The feed pump is used for delivering the feed liquid to the high-pressure pump;

[0013] The high-pressure pump is used for pressurizing the feed liquid and sending the pressurized feed liquid to the reverse osmosis membrane assembly;

[0014] The reverse osmosis membrane assembly is used for reverse osmosis concentration treatment of the feed liquid to obtain reverse osmosis product water and reverse osmosis concentrated water, wherein the apparent rejection rate of the reverse osmosis membrane assembly is 10-50%;

[0015] The crystallization device is used for crystallizing and precipitating the saturated inorganic salt components of the reverse osmosis concentrated water, and growing the precipitated crystal particles to obtain solid, effluent and crystallization mother liquor;

[0016] The dewatering device is used for dewatering treatment on the external drainage liquid to obtain supernatant and dewatered crystal product.

[0017] According to some embodiments of the device of the present application, preferably, the reverse osmosis membrane assembly comprises a reverse osmosis membrane element or a nanofiltration membrane element.

[0018] According to some embodiments of the device of the present application, preferably, the reverse osmosis membrane assembly parameters comprise: an operating pressure of 4-12 MPa, preferably 5.5-8.5 MPa; more preferably, when the operating pressure is 4-7 MPa, the apparent rejection rate is 5%-20%; more preferably, when the operating pressure is greater than 7 MPa and not greater than 12 MPa, the apparent rejection rate is greater than 20% and not greater than 40%.

[0019] In the present application, the term "apparent rejection rate" refers to the proportion of the portion of the solute of the raw water retained by the reverse osmosis unit to the total amount of the raw water. The apparent rejection rate is commonly defined as R=(1-C1 / C0)×100%. In the formula, R is the apparent rejection rate, C1 is the permeate concentration, and C0 is the feed liquid concentration.

[0020] According to some embodiments of the device of the present application, preferably, the reverse osmosis membrane crystallization treatment device further comprises a pretreatment device for pretreating the to-be-treated salt-containing liquid to obtain a pretreated to-be-treated salt-containing liquid. Then the liquid is introduced into the liquid tank.

[0021] According to some embodiments of the device of the present application, preferably, the pretreatment device comprises one or more of an oxidation device, a coagulation device, a flocculation device, a sedimentation device, a sand filtration device, a porous medium filtration device, a degassing device, a bacteriostatic device, an activated carbon filtration device, a microfiltration device, an ultrafiltration device, and a reduction device. In the present application, the pretreatment device is used to treat the water entering the reverse osmosis assembly to remove suspended particles, organic matter, microorganisms, heavy metals, dissolved gases, oxidizing agents, and other substances in the raw water that affect the operation of the reverse osmosis assembly.

[0022] According to some embodiments of the device of the present application, preferably, the supernatant outlet of the dewatering device is in communication with the inlet of the pretreatment device for pretreating the supernatant.

[0023] According to some embodiments of the device of the present application, preferably, the crystallization mother liquor outlet of the crystallization device is in communication with the inlet of the pretreatment device.

[0024] According to some embodiments of the device of the present application, preferably, the reverse osmosis membrane crystallization treatment device further comprises a pre-concentration device for pre-concentrating the pretreated to-be-treated salt-containing liquid. Then the liquid is introduced into the liquid tank.

[0025] According to some embodiments of the device of the present application, preferably, the pre-concentration device comprises one or more of a nanofiltration device, an electrodialysis device, a conventional reverse osmosis device, an ultra-high pressure reverse osmosis device, a forward osmosis device, a membrane distillation device, an electrosorption device, a diffusion dialysis device, and an evaporation device.

[0026] According to some embodiments of the device of the present application, preferably, the outlet of the reverse osmosis product water of the reverse osmosis membrane assembly is in communication with the pre-concentration device and / or the inlet of the pre-concentration device for pre-treatment and / or concentration treatment of the reverse osmosis product water. Preferably, the outlet of the reverse osmosis product water of the reverse osmosis membrane assembly is in communication with the inlet of the pre-concentration device for concentration treatment of the reverse osmosis product water.

[0027] According to some embodiments of the device of the present application, preferably, the reverse osmosis membrane crystallization treatment device further comprises an energy recovery device for recovering the pressure energy of the reverse osmosis concentrated water. In the present application, the energy recovery device can be a hydraulic turbine type or a work exchange type.

[0028] According to some embodiments of the device of the present application, preferably, the high-pressure pump is a plunger pump or a multi-stage centrifugal pump.

[0029] According to some embodiments of the device of the present application, preferably, the crystallization device is a DTB crystallizer or an OSLO crystallizer.

[0030] According to some embodiments of the device of the present application, preferably, the dewatering device is a centrifugal dewatering machine, a plate-and-frame filter press, a belt filter, a vacuum filter, or a prilling dewatering machine.

[0031] According to some embodiments of the device of the present application, preferably, the reverse osmosis membrane assembly is a flat sheet membrane type assembly, a butterfly tube type assembly, a hollow fiber type assembly, a pipe network type assembly, or a spiral wound type assembly.

[0032] According to some embodiments of the device of the present application, a raw water supply source containing the salt-containing feed liquid to be treated is in communication with the feed liquid tank. In the preferred case where the pre-treatment device and the pre-concentration device are provided, the raw water supply source containing the salt-containing feed liquid to be treated is in communication with the pre-treatment device, and in turn passes into the pre-concentration device, the feed liquid tank, the feed pump, the high-pressure pump, the reverse osmosis membrane assembly, the crystallization device, and the dewatering device, etc.

[0033] The second aspect of the present application provides a reverse osmosis crystallization treatment method, comprising the following steps:

[0034] (1) mixing the salt-containing feed liquid to be treated with an inorganic salt stabilizer, and transporting and pressurizing to a reverse osmosis membrane assembly for reverse osmosis concentration treatment to obtain reverse osmosis product water and reverse osmosis concentrated water;

[0035] (2) in the crystallization device, the reverse osmosis concentrated water is subjected to crystallization treatment, the supersaturated inorganic salt component is crystallized and separated out under the action of the crystal seeds, and the separated crystal particles are grown, to obtain solid, effluent and crystallization mother liquor;

[0036] (3) the effluent is subjected to dewatering treatment, to obtain supernatant and dewatered crystal product.

[0037] According to some embodiments of the treatment method, preferably, the operating conditions of the reverse osmosis membrane assembly include: operating pressure of 4-12 MPa, preferably 5.5-8.5 MPa; more preferably, when the operating pressure is 4-7 MPa, the apparent rejection rate is 5%-20%; more preferably, when the operating pressure is greater than 7 MPa and not greater than 12 MPa, the apparent rejection rate is greater than 20% and not greater than 40%.

[0038] According to some embodiments of the treatment method, preferably, the water inlet temperature of the reverse osmosis membrane assembly is 5-45℃, more preferably 20-30℃.

[0039] According to some embodiments of the treatment method, preferably, the solid content in the crystallization device is 2%-10%.

[0040] According to some embodiments of the treatment method, preferably, in the water inlet of the reverse osmosis concentration treatment, the mass concentration of the inorganic salt to be crystallized is 70%-100% of the mass concentration of the inorganic salt under the condition of saturation at 25℃.

[0041] According to some embodiments of the treatment method, preferably, in the concentrated water of the reverse osmosis concentration treatment, the mass concentration of the inorganic salt to be crystallized is 100-120% of the mass concentration of the inorganic salt under the condition of saturation at 25℃.

[0042] According to some embodiments of the treatment method, preferably, in the water inlet of the reverse osmosis concentration treatment, one or more of sodium chloride, sodium sulfate, sodium nitrate, lithium chloride, lithium sulfate, lithium nitrate, lithium carbonate, lithium bicarbonate, potassium chloride, magnesium chloride, calcium chloride and ammonium chloride are contained.

[0043] According to some embodiments of the treatment method, preferably, in the water inlet of the reverse osmosis concentration treatment, the mass concentration of sodium chloride is 15%-28%.

[0044] According to some embodiments of the treatment method, preferably, in the water inlet of the reverse osmosis concentration treatment, the mass concentration of sodium sulfate is 10%-30%.

[0045] According to some embodiments of the treatment method of the present application, preferably, the mass concentration of sodium nitrate in the water inlet of the reverse osmosis concentration treatment is 35%-50%.

[0046] According to some embodiments of the treatment method of the present application, preferably, the mass concentration of lithium chloride in the water inlet of the reverse osmosis concentration treatment is 35%-50%.

[0047] According to some embodiments of the treatment method of the present application, preferably, the mass concentration of lithium sulfate in the water inlet of the reverse osmosis concentration treatment is 15%-25%.

[0048] According to some embodiments of the treatment method of the present application, preferably, the mass concentration of lithium nitrate in the water inlet of the reverse osmosis concentration treatment is 35%-55%.

[0049] According to some embodiments of the treatment method of the present application, preferably, the mass concentration of potassium chloride in the water inlet of the reverse osmosis concentration treatment is 15%-25%.

[0050] According to some embodiments of the treatment method of the present application, preferably, the mass concentration of ammonium chloride in the water inlet of the reverse osmosis concentration treatment is 20%-30%.

[0051] According to some embodiments of the treatment method of the present application, preferably, the produced water of the reverse osmosis concentration treatment is recycled back to the pretreatment unit.

[0052] According to some embodiments of the treatment method of the present application, preferably, before mixing the salt-containing liquid to be treated with the inorganic salt stabilizer, the treatment method further comprises pretreating the salt-containing liquid to be treated to obtain a pretreated salt-containing liquid to be treated.

[0053] According to some embodiments of the treatment method of the present application, preferably, the pretreatment comprises one or more of oxidation treatment, flocculation treatment, precipitation treatment, sand filtration treatment, multi-media filtration treatment, degassing treatment, bacteriostatic treatment, activated carbon adsorption treatment, microfiltration treatment, ultrafiltration treatment, and reduction treatment. In the present application, the pretreatment is used to treat the water inlet of the reverse osmosis assembly to remove suspended particles, organic matter, microorganisms, heavy metals, dissolved gases, oxidants, and other substances in the raw water that affect the operation of the reverse osmosis assembly.

[0054] According to some embodiments of the treatment method of the present application, preferably, the supernatant is mixed with the salt-containing liquid to be treated and pretreated.

[0055] According to some embodiments of the treatment method of the present application, preferably, the crystallization mother liquor is mixed with the salt-containing liquid to be treated and pretreated.

[0056] According to some embodiments of the treatment method of the present application, preferably, after obtaining the pretreated salt-containing feed liquid, and before mixing with the inorganic salt stabilizer, the treatment method further comprises a pre-concentration treatment.

[0057] According to some embodiments of the treatment method of the present application, preferably, the reverse osmosis product water is mixed with the salt-containing feed liquid and / or the pretreated salt-containing feed liquid for the pretreatment and / or concentration treatment. Preferably, the reverse osmosis product water is mixed with the pretreated salt-containing feed liquid.

[0058] According to some embodiments of the treatment method of the present application, preferably, the pre-concentration treatment comprises one or more of nanofiltration concentration treatment, electrodialysis concentration treatment, reverse osmosis concentration treatment, ultra-high pressure reverse osmosis concentration, forward osmosis concentration treatment, membrane distillation concentration treatment, electrosorption concentration treatment, diffusion dialysis concentration treatment, and evaporation concentration treatment.

[0059] According to some embodiments of the treatment method of the present application, preferably, the inorganic salt stabilizer is selected from one or more of potassium ferricyanide, potassium ferrocyanide, sodium ferricyanide, sodium ferrocyanide, phthalamidic compound, polymaleic acid, polyacrylic acid, phospho-based carboxylic acid copolymer, polyepoxysuccinic acid, polyaspartic acid, ascorbic acid, hydroxyethylidene diphosphonic acid, ethylenediaminetetramethylene phosphonic acid, aminotri(methylene) phosphonic acid, tannic acid, diethylene triamine penta(methylene) phosphonic acid, polyol phosphate ester, and phosphono glycolic acid.

[0060] According to some embodiments of the treatment method of the present application, preferably, the dosage of the inorganic salt stabilizer is 100 ppm-10000 ppm.

[0061] According to some specific embodiments of the treatment method of the present application, the reverse osmosis membrane crystallization treatment method is performed using the reverse osmosis membrane crystallization device, comprising the following steps:

[0062] (1) after the pretreatment and pre-concentration treatment of the salt-containing feed liquid, the liquid enters the feed liquid tank;

[0063] (2) in the feed liquid tank, the feed liquid is mixed with the inorganic salt stabilizer, and then is transported by the feed pump and pressurized by the high-pressure pump, and enters the reverse osmosis membrane module for reverse osmosis concentration treatment, to obtain reverse osmosis product water and reverse osmosis concentrated water;

[0064] (3) the reverse osmosis product water is sent to the pretreatment device and / or pre-concentration device for pretreatment and / or concentration treatment, preferably, the reverse osmosis product water is sent to the pre-concentration device for concentration treatment; the reverse osmosis concentrated water is sent to the crystallization device for crystallization treatment;

[0065] (4) In the crystallization device, the supersaturated inorganic salt components crystallize and precipitate under the promotion of the seed crystals, and the precipitated crystal particles grow to obtain solid, drain liquid and crystallization mother liquor; when the solid content in the crystallizer is too high, the solid is drained and the solid content is controlled to be 2-10% by mass. The drain liquid is sent to the dehydration device for dehydration treatment, and the crystallization mother liquor is sent to the pretreatment device for pretreatment.

[0066] (5) The effluent is dehydrated by a dehydration device to obtain supernatant and dehydrated crystal product; the obtained supernatant is recycled to a pretreatment device for further processing, and the obtained dehydrated crystal product is collected as a product.

[0067] The beneficial effects of this invention are:

[0068] (1) This invention employs a reverse osmosis membrane module with a specific rejection ratio to partially desalinate the pressurized feed solution, forming reverse osmosis permeate and reverse osmosis concentrate. Part of the salt in the feed solution is retained by the reverse osmosis membrane, forming the permeate. Because the dissolved ions in the feed solution are partially retained by the reverse osmosis membrane, the salinity of the permeate is lower than that of the feed solution. After treatment by the reverse osmosis membrane module, the salinity of the concentrate increases. When the dissolved salt concentration reaches supersaturation, crystallization occurs, yielding a crystalline salt product. The reverse osmosis membrane module of this invention is equipped with a reverse osmosis membrane element or a nanofiltration membrane element with a specific rejection ratio. Preferably, when the operating pressure is 4-7 MPa, the apparent rejection ratio is 5%-20%; more preferably, when the operating pressure is greater than 7 MPa and not greater than 12 MPa, the apparent rejection ratio is greater than 20% and not greater than 40%, achieving further concentration of the feed solution to be crystallized at higher salinity.

[0069] (2) In this invention, because an inorganic salt stabilizer is added to the feed water, the feed solution concentrated to saturation by reverse osmosis does not crystallize during the reverse osmosis process, but precipitates in the crystallizer under the induction of crystal seeds, thus realizing the crystallization reaction under normal temperature conditions. Attached Figure Description

[0070] Figure 1 This is a schematic diagram of the reverse osmosis membrane crystallization treatment equipment provided in Embodiment 1 of the present invention.

[0071] Figure 2 This is a schematic diagram of the reverse osmosis membrane crystallization treatment equipment provided in Embodiment 3 of the present invention.

[0072] Explanation of reference numerals in the attached figures

[0073] 1. Pretreatment unit; 2. Pre-concentration unit; 3. Feed tank.

[0074] 4. Dosing device; 5. Feed pump; 6. High-pressure pump

[0075] 7. Reverse osmosis membrane module; 8. Crystallization unit; 9. Dehydration unit. Detailed Implementation

[0076] To make the present invention easier to understand, the present invention will be described in detail below with reference to embodiments. These embodiments are for illustrative purposes only and are not limited to the scope of application of the present invention.

[0077]

Example 1

[0078] 1. Adopt Figure 1 The reverse osmosis membrane crystallization treatment equipment shown is used for crystallizing NaCl-rich brine, where the NaCl mass concentration is 7% and the trace calcium sulfate impurity mass concentration is 260 ppm. The reverse osmosis membrane crystallization treatment equipment consists of a pretreatment unit (a porous media filtration unit and an ultrafiltration unit) connected in sequence. Figure 1 (Number 1) Pre-concentration unit (electrodialysis-reverse osmosis coupling unit, i.e., electrodialysis unit) Figure 1 The winning bid number is 2), and the liquid tank ( Figure 1 (No. 3) Feed pump ( Figure 1 (No. 5) High-pressure pump ( Figure 1 (No. 6) Reverse osmosis membrane module (disc tube type reverse osmosis membrane module) Figure 1 (No. 7) Crystallization apparatus (DTB crystallizer) Figure 1 (No. 8) and dehydration equipment (centrifugal dehydrator) Figure 1 The winning bid number is 9), and the dosing device connected to the liquid tank ( Figure 1 The invention comprises: a dosing device for adding inorganic salt stabilizer to a feed tank; a feed tank for storing the salt-containing feed solution to be treated and mixing the inorganic salt stabilizer with the feed solution within the tank; a feed pump for conveying the feed solution to a high-pressure pump; a high-pressure pump for pressurizing the feed solution and sending the pressurized feed solution to a reverse osmosis membrane module; a reverse osmosis membrane module for concentrating the feed solution using reverse osmosis to obtain reverse osmosis permeate and reverse osmosis concentrate, wherein the reverse osmosis membrane module operates at 6.9 MPa with an apparent rejection rate of 19%; a crystallization device for crystallizing the saturated inorganic salt components of the reverse osmosis concentrate and growing the precipitated crystal particles to obtain a solid, an effluent, and a crystallization mother liquor; and a dehydration device for dehydrating the effluent to obtain a supernatant and a dehydrated crystal product.

[0079] 2. Reverse osmosis crystallization treatment method:

[0080] The feed solution in the tank contains 7% NaCl by mass, with a feed flow rate of 10 t / hr. The concentration of potassium ferrocyanide (inorganic salt stabilizer) in the feed tank is adjusted to 0.025 mol / L. After pretreatment involving chemical precipitation, resin impurity removal, porous media filtration, and ultrafiltration, followed by electrodialysis and reverse osmosis (the pre-concentration unit employs a multi-stage, multi-section reverse osmosis process; the desalination rate of the reverse osmosis membrane module gradually decreases from the feed solution to the system concentrate, and gradually increases from the feed solution to the system permeate), the NaCl concentration reaches 25.9%. This NaCl is then further concentrated by the reverse osmosis module, with an inlet water temperature of 20°C. In the inlet water for reverse osmosis concentration, the concentration of the inorganic salt to be crystallized is 97% of its saturated concentration at 25°C. The sodium chloride concentration in the inlet water for reverse osmosis concentration is 25.8%. After reverse osmosis (RO) concentration treatment at 6.9 MPa with an apparent rejection rate of 16%, RO permeate and RO concentrate are obtained. The salinity of the RO permeate is 21.7%, and it is recycled to a pre-concentration unit for further concentration. The concentration of the RO concentrate reaches 27.1%, and it is then fed into a crystallization unit for sodium chloride crystallization, allowing the precipitated crystals to grow, yielding solids, effluent, and mother liquor. The solid content in the crystallization unit is controlled at 5-6% by mass. The mother liquor is recycled to a pretreatment unit, and the effluent is fed into a dehydration unit for dehydration, yielding supernatant and dehydrated crystal product. The supernatant is recycled to the pretreatment unit for pretreatment, and the salt yield of the dehydrated crystal product is 582 kg / hr.

[0081]

Example 2

[0082] The difference between the equipment and processing method in Example 1 is that the pre-concentration device performs pre-concentration at a lower concentration ratio.

[0083] 1. Adopt Figure 1 The reverse osmosis membrane crystallization treatment equipment shown is used for crystallizing NaCl-rich brine, where the NaCl mass concentration is 7% and the trace calcium sulfate impurity mass concentration is 260 ppm. The reverse osmosis membrane crystallization treatment equipment consists of a pretreatment unit (a porous media filtration unit and an ultrafiltration unit) connected in sequence. Figure 1 (Number 1) Pre-concentration unit (electrodialysis-reverse osmosis coupling unit, i.e., electrodialysis unit) Figure 1 The winning bid number is 2), and the liquid tank ( Figure 1 (No. 3) Feed pump ( Figure 1 (No. 5) High-pressure pump ( Figure 1 (No. 6) Reverse osmosis membrane module (disc tube type reverse osmosis membrane module) Figure 1 (No. 7) Crystallization apparatus (DTB crystallizer) Figure 1(No. 8) and dehydration equipment (centrifugal dehydrator) Figure 1 The winning bid number is 9), and the dosing device connected to the liquid tank ( Figure 2 The following components are included: a dosing device for adding inorganic salt stabilizer to a feed tank; a feed tank for storing the salt-containing feed solution to be treated and mixing the inorganic salt stabilizer with the feed solution within the tank; a feed pump for conveying the feed solution to a high-pressure pump; a high-pressure pump for pressurizing the feed solution and sending the pressurized feed solution to a reverse osmosis membrane module; a reverse osmosis membrane module for concentrating the feed solution using reverse osmosis to obtain reverse osmosis permeate and reverse osmosis concentrate, wherein the reverse osmosis membrane module operates at 11 MPa with an apparent rejection rate of 25%; a crystallization device for crystallizing the saturated inorganic salt components from the reverse osmosis concentrate and growing the precipitated crystal particles to obtain a solid, an effluent, and a crystallization mother liquor; and a dehydration device for dehydrating the effluent to obtain a supernatant and a dehydrated crystal product.

[0084] 2. Reverse osmosis crystallization treatment method:

[0085] The feed solution containing salt has a NaCl concentration of 7% and a feed flow rate of 10 t / hr. 0.05 mol / kg potassium ferrocyanide (an inorganic salt stabilizer) is added to the feed solution. After pretreatment involving chemical precipitation, resin impurity removal, porous media filtration, and ultrafiltration, followed by electrodialysis and reverse osmosis (the pre-concentration unit employs a multi-stage, multi-section reverse osmosis process; the desalination rate of the reverse osmosis membrane module gradually decreases from the feed solution to the system concentrate, and gradually increases from the feed solution to the system permeate), the NaCl concentration reaches 23%. This NaCl is then introduced into the reverse osmosis module for concentration. The feed water temperature of the reverse osmosis membrane module is 20℃. In the feed water of the reverse osmosis concentration treatment, the concentration of the inorganic salt to be crystallized is 93% of its saturated concentration at 25℃. The sodium chloride concentration in the feed water of the reverse osmosis concentration treatment is 25%. After reverse osmosis concentration treatment at 11 MPa with an apparent rejection rate of 24%, reverse osmosis permeate and reverse osmosis concentrate are obtained. The salinity of the reverse osmosis permeate is 19%. The concentration of the reverse osmosis concentrate reaches 27.2%. The reverse osmosis concentrate is then fed into a crystallization unit for sodium chloride crystallization, allowing the precipitated crystal particles to grow, yielding solids, effluent, and mother liquor. The solid content in the crystallization unit is controlled at 5%. The mother liquor is recycled to the pretreatment unit, and the effluent is fed into a dehydration unit for dehydration treatment, yielding supernatant and dehydrated crystal product. The salt yield of the dehydrated crystal product is 583 kg / hr.

[0086]

Example 3

[0087] The equipment and processing method are the same as in Example 1, except that chemical precipitation and resin impurity removal pretreatment are not used, and the concentration ratio of the pre-concentration device is relatively low.

[0088] 1. Adopt Figure 2 The reverse osmosis membrane crystallization treatment equipment shown is used for crystallizing NaCl brine. The equipment consists of a pre-concentration unit (an electrodialysis-reverse osmosis coupling unit, i.e., an electrodialysis unit) connected in sequence. Figure 2 The winning bid number is 2), and the liquid tank ( Figure 2 (No. 3) Feed pump ( Figure 2 (No. 5) High-pressure pump ( Figure 2 (No. 6) Reverse osmosis membrane modules (reverse osmosis membrane modules include reverse osmosis membrane elements and pipeline modules, Figure 2 (No. 7) Crystallization apparatus (OSLO crystallizer) Figure 2 The number of the winning bid is 8) and the dewatering device (plate and frame filter press, Figure 2 The winning bid number is 9), and the dosing device connected to the liquid tank ( ​ The invention comprises: a dosing device for adding inorganic salt stabilizer to a feed tank; a feed tank for storing the salt-containing feed solution to be treated and mixing the inorganic salt stabilizer with the feed solution within the feed tank; a feed pump for conveying the feed solution to a high-pressure pump; a high-pressure pump for pressurizing the feed solution and sending the pressurized feed solution to a reverse osmosis membrane module; a reverse osmosis membrane module for concentrating the feed solution using reverse osmosis to obtain reverse osmosis permeate and reverse osmosis concentrate, wherein the reverse osmosis membrane module has an apparent rejection rate of 27.8% at 7.1 MPa; a crystallization device for crystallizing saturated inorganic salt components from the reverse osmosis concentrate and growing the precipitated crystal particles to obtain a solid, an effluent, and a crystallization mother liquor; and a dehydration device for dehydrating the effluent to obtain a supernatant and a dehydrated crystal product.

[0089] 2. Reverse osmosis crystallization treatment method:

[0090] The feed solution in the tank contains 7% NaCl at a flow rate of 10 t / hr. 0.05 mol / kg potassium ferrocyanide (an inorganic salt stabilizer) is added to the feed tank. The pre-concentration unit employs a multi-stage, multi-section reverse osmosis process. The desalination rate of the reverse osmosis membrane module gradually decreases from the feed solution to the system concentrate; conversely, the desalination rate gradually increases from the feed solution to the system permeate, reaching a NaCl concentration of 23%. This NaCl is then concentrated by the reverse osmosis module, with an inlet water temperature of 20°C. In the feed water for the reverse osmosis concentration treatment, the concentration of the inorganic salt to be crystallized is 93% of its saturated concentration at 25°C. The sodium chloride concentration in the feed water for the reverse osmosis concentration treatment is 25%. After reverse osmosis concentration treatment at 11 MPa with an apparent rejection rate of 29%, reverse osmosis permeate and reverse osmosis concentrate are obtained. The salinity of the reverse osmosis permeate is 18.1%. The concentration of the reverse osmosis concentrate reaches 27.2%. This concentrate is then fed into a crystallization unit to induce sodium chloride crystallization, allowing the precipitated crystals to grow and yielding solids, effluent, and mother liquor. The solid content in the crystallization unit is controlled at 5%. The mother liquor is recycled to a pretreatment unit, while the effluent is fed into a dehydration unit for dehydration, yielding supernatant and dehydrated crystal product. The salt yield of the dehydrated crystal product is 390 kg / hr.

[0091]

Example 4

[0092] The apparatus and method of Example 1 are followed, except that the salt-containing feed solution in the feed tank is replaced with a feed solution containing KCl, with a KCl mass concentration of 7%. The final salt yield of the dehydrated crystal product is 552 kg / hr.

[0093] Comparative Example 1

[0094] The apparatus and processing method of Example 1 were used, except that no inorganic salt stabilizer was added, which resulted in reverse osmosis membrane blockage and equipment failure and shutdown.

[0095] Comparative Example 2

[0096] In the implementation of this example, conventional reverse osmosis membrane modules (operating pressure <4 MPa for brackish water membranes and <7 MPa for seawater desalination membranes) were used for concentration treatment. Because the rejection rate of conventional reverse osmosis membrane modules is over 99% under standard testing conditions, and the reverse osmosis layers are dense, the osmotic pressure across the membrane cannot be overcome under the feed water conditions of this example, resulting in extremely low membrane flux. The feed water salinity to the reverse osmosis module was 20%, and the concentrate salinity was also 20%, resulting in no concentration effect. After the concentrate from the reverse osmosis module entered the crystallizer, no crystallization reaction occurred because it did not reach sodium chloride saturation.

[0097] The above description is merely a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, based on the technical teachings provided by the present invention and as common knowledge in the field, other equivalent modifications and improvements can be made, and these should also be considered within the scope of protection of the present invention.

Claims

1. A reverse osmosis crystallization treatment method, comprising the following steps: (1) In the feed tank, the salt-containing feed solution to be treated is mixed with inorganic salt stabilizer and then transported and pressurized to the reverse osmosis membrane module for reverse osmosis concentration treatment to obtain reverse osmosis permeate and reverse osmosis concentrate. (2) In the crystallization device, the reverse osmosis concentrate is crystallized. The supersaturated inorganic salt components crystallize out under the action of seed crystals, and the precipitated crystal particles grow to obtain solid, drain liquid and crystallization mother liquor. (3) The effluent is dehydrated in the dehydration device to obtain supernatant and dehydrated crystal product; the reverse osmosis membrane assembly includes reverse osmosis membrane elements; The operating conditions for the reverse osmosis membrane module include: pressure greater than 7 MPa and not greater than 12 MPa, and apparent rejection rate greater than 20% and not greater than 40%. In the feed water of the reverse osmosis concentration treatment, the mass concentration of the inorganic salt to be crystallized is 93%-100% of the mass concentration of the inorganic salt under saturation conditions at 25℃; In the concentrated water from reverse osmosis treatment, the mass concentration of the inorganic salt to be crystallized is 100-120% of the mass concentration of the inorganic salt under saturated conditions at 25°C. The feed water for reverse osmosis concentration treatment contains one of the following: sodium chloride, sodium sulfate, sodium nitrate, lithium chloride, lithium sulfate, lithium nitrate, lithium carbonate, lithium bicarbonate, potassium chloride, magnesium chloride, calcium chloride, and ammonium chloride; the mass concentration of sodium chloride is 15%-28%; the mass concentration of sodium sulfate is 10%-30%; the mass concentration of sodium nitrate is 35%-50%; the mass concentration of lithium chloride is 35%-50%; the mass concentration of lithium sulfate is 15%-25%; the mass concentration of lithium nitrate is 35%-55%; the mass concentration of potassium chloride is 15%-25%; and the mass concentration of ammonium chloride is 20%-30%.

2. The processing method according to claim 1, characterized in that, The feed water temperature of the reverse osmosis membrane module is 5℃-45℃; The solid content in the crystallization apparatus is 2%-10%; and / or, The permeate from the reverse osmosis concentration treatment is recycled back to the pretreatment unit.

3. The processing method according to claim 1 or 2, characterized in that, Before mixing the salt-containing liquid to be treated with the inorganic salt stabilizer, the treatment method further includes pre-treating the salt-containing liquid to be treated to obtain a pre-treated salt-containing liquid to be treated. And / or, the feed water temperature of the reverse osmosis membrane module is 20℃-30℃.

4. The processing method according to claim 3, characterized in that, The pretreatment includes one or more of the following: oxidation treatment, flocculation treatment, precipitation treatment, sand filtration treatment, multi-media filtration treatment, degassing treatment, antibacterial treatment, activated carbon adsorption treatment, microfiltration treatment, ultrafiltration treatment, and reduction treatment.

5. The processing method according to claim 3, characterized in that, The supernatant was mixed with the saline solution to be treated and then pretreated.

6. The processing method according to claim 3, characterized in that, The crystallization mother liquor is mixed with the salt-containing liquid to be treated and then pretreated.

7. The processing method according to claim 3, characterized in that, After obtaining the pretreated salt-containing liquid to be treated, and before mixing with the inorganic salt stabilizer, the treatment method further includes a pre-concentration treatment.

8. The processing method according to claim 7, characterized in that, The reverse osmosis permeate is mixed with the saline solution to be treated and / or the pretreated saline solution to be treated. And / or, the pre-concentration treatment includes one or more of nanofiltration concentration treatment, electrodialysis concentration treatment, reverse osmosis concentration treatment, ultra-high pressure reverse osmosis concentration treatment, forward osmosis concentration treatment, membrane distillation concentration treatment, electroadsorption concentration treatment, diffusion dialysis concentration treatment and evaporation concentration treatment.

9. The processing method according to any one of claims 1 or 2, characterized in that, The inorganic salt stabilizer is selected from one or more of potassium ferrocyanide, potassium ferrocyanide, sodium ferrocyanide, sodium ferrocyanide, phthalamide compounds, polymaleic acid, polyacrylic acid, phosphate-based carboxylic acid copolymers, polyepoxysuccinic acid, polyaspartic acid, ascorbic acid, hydroxyethylidene diphosphonic acid, ethylenediaminetetramethylenephosphonic acid, aminotrimethylenephosphonic acid, tannic acid, diethylenetriaminepentamethylenephosphonic acid, polyol phosphates, and phosphonoglycolic acid.

10. The processing method according to claim 9, characterized in that, The dosage of the inorganic salt stabilizer is 100ppm-10000ppm.

11. The processing method according to claim 1 or 2, characterized in that, In step (1), the salt-containing liquid to be treated is mixed with an inorganic salt stabilizer and transported to a high-pressure pump via a feed pump. After being increased by the high-pressure pump, the pressurized liquid is sent to the reverse osmosis membrane module for reverse osmosis concentration treatment.

12. The processing method according to claim 11, characterized in that, The high-pressure pump is a plunger pump or a multi-stage centrifugal pump; and / or, The crystallization apparatus is a DTB crystallizer or an OSLO crystallizer; and / or, The dewatering device is a centrifugal dewatering machine, a plate and frame filter press, a belt filter, a vacuum filter, or a granulation dewatering machine; and / or, The reverse osmosis membrane module can be a flat sheet membrane module, a butterfly tube module, a hollow fiber module, a pipe network module, or a spiral wound module.

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