阅读说明：本技术 一种利用高盐废水精制盐的工艺及系统 (Process and system for refining salt by using high-salinity wastewater ) 是由 张刚 贾启 庞学雷 杨希清 周兆凯 于 2020-12-21 设计创作，主要内容包括：本发明属于废水处理技术领域,具体涉及一种利用高盐废水精制盐的工艺及系统。该工艺包括如下步骤：对高盐废水进行预处理,将预处理后的废水通过MVR机械式蒸汽再压缩技术进行预浓缩,预浓缩后再通过ED离子膜浓缩,之后进入双级纳滤系统完成氯化钠和硫酸钠的分离,再通过冷却结晶分别制得氯化钠和硫酸钠。该系统包括依次连接的软化澄清池、臭氧生物碳滤池、脱碳塔、MVR蒸发器、ED浓缩装置、双级纳滤设备,双级纳滤设备连有氯化钠结晶器和硫酸钠结晶器。本发明在降低生产能耗的基础上,极大提高了产品盐的回收率和纯度,实现了高盐废水的资源化利用。(The invention belongs to the technical field of wastewater treatment, and particularly relates to a process and a system for refining salt by using high-salinity wastewater. The process comprises the following steps: the method comprises the steps of pretreating high-salinity wastewater, pre-concentrating the pretreated wastewater by an MVR mechanical vapor recompression technology, concentrating the wastewater by an ED ion membrane after pre-concentration, separating sodium chloride and sodium sulfate by a two-stage nanofiltration system, and respectively preparing the sodium chloride and the sodium sulfate by cooling crystallization. The system comprises a softening clarification tank, an ozone biochar filter tank, a decarbonization tower, an MVR evaporator, an ED concentration device and two-stage nanofiltration equipment which are sequentially connected, wherein the two-stage nanofiltration equipment is connected with a sodium chloride crystallizer and a sodium sulfate crystallizer. On the basis of reducing production energy consumption, the method greatly improves the recovery rate and purity of the product salt, and realizes resource utilization of high-salinity wastewater.)

1. A process for refining salt by using high-salinity wastewater is characterized by comprising the following steps: the method comprises the steps of pretreating high-salinity wastewater, pre-concentrating the pretreated wastewater by an MVR mechanical vapor recompression technology, concentrating the wastewater by an ED ion membrane after pre-concentration, separating sodium chloride and sodium sulfate by a two-stage nanofiltration system, and respectively preparing the sodium chloride and the sodium sulfate by cooling crystallization.

2. The process for refining salt by using high-salinity wastewater as claimed in claim 1, wherein the pretreatment step comprises: softening and clarifying the high-salinity wastewater, performing ozone catalytic oxidation, performing biodegradation and adsorption, performing activated carbon adsorption and decarbonizing treatment in sequence.

3. The process for refining salt by using high-salinity wastewater as claimed in claim 2, wherein the softening and clarifying agents used comprise: calcium oxide and sodium metaaluminate in a weight ratio of 1: 1.

4. The process for refining salt by using high-salinity wastewater as claimed in claim 3, wherein the pH value of softening and clarifying is 8-9.5, the temperature of softening and clarifying is 20-40 ℃, and the time of softening and clarifying is 0.5-1.5 h.

5. The process for refining salt by using high-salinity wastewater as claimed in claim 1, wherein the temperature of the pre-concentration is 500-550 ℃, and the pressure is 9.5-10.5 MPa.

6. The process for refining the salt by using the high-salinity wastewater as claimed in claim 1, wherein the nanofiltration membrane adopted by the double-stage nanofiltration system is a monovalent ion selective membrane ACS-CIMS.

7. The process for refining salt by using high-salinity wastewater as claimed in claim 1, wherein the crystallization temperature of the sodium chloride is 10-18 ℃, and the crystallization time is 1.2-2.0 h; the crystallization temperature of the sodium sulfate is 14-22 ℃, and the crystallization time is 1.5-2.2 h.

8. The system of any one of claims 1 to 7, comprising a softening and clarifying tank, an ozone biochar filter, a decarbonizing tower, an MVR evaporator, an ED concentration device and a two-stage nanofiltration device which are connected in sequence, wherein the two-stage nanofiltration device is connected with a sodium chloride crystallizer and a sodium sulfate crystallizer.

Technical Field

The invention belongs to the technical field of wastewater treatment, and particularly relates to a process and a system for refining salt by using high-salinity wastewater.

Background

The high-salt wastewater refers to wastewater with the total salt mass fraction of more than 1%, mainly comes from industrial production processes of papermaking, printing and dyeing, chemical industry, petroleum and natural gas collection and processing and the like, is wide in production path, and the water quantity is increased year by year. The organic matters in the high-salt wastewater have great differences in the types and chemical properties of the organic matters according to different production processes, but most of the salt substances are Cl^-、SO₄ ^2-、Na⁺、Ca²⁺And the like, the removal of organic pollutants in the high-salt wastewater is of great importance to reduce the influence of the organic pollutants on the environment.

The technologies commonly used for treating high-salinity wastewater at present are incineration, electrodialysis, membrane separation, biological treatment and evaporative concentration-cooling crystallization. The burning method has high energy consumption, limited treatment effect and high operation cost; the electrodialysis method and the membrane separation method have complex processes and expensive equipment, scale formation is easy to occur, the water production efficiency of the membrane and evaporation is reduced if the equipment is expensive, the membrane, a pipeline or a device is blocked if the equipment is heavy, and the maintenance cost is high; the biological treatment method is easy to damage because of the large culture period of the biological strains, and also causes higher maintenance cost; the traditional evaporation concentration-cooling crystallization treatment method has the advantages of low product purity, relatively low yield and long required time.

Disclosure of Invention

Aiming at the problems of high energy consumption, easy scaling and relatively low salt yield and purity in the existing high-salt wastewater treatment technology, the invention provides a process for refining salt by using high-salt wastewater, and the recovery rate and purity of product salt are greatly improved on the basis of reducing production energy consumption.

The invention provides a process for refining salt by using high-salinity wastewater, which comprises the following steps: the method comprises the steps of pretreating high-salinity wastewater, pre-concentrating the pretreated wastewater by an MVR mechanical vapor recompression technology, concentrating the wastewater by an ED ion membrane after pre-concentration, separating sodium chloride and sodium sulfate by a two-stage nanofiltration system, and respectively preparing the sodium chloride and the sodium sulfate by cooling crystallization.

Further, the pretreatment step is as follows: sequentially carrying out softening clarification, ozone catalytic oxidation, biodegradation and adsorption, activated carbon adsorption and decarburization treatment on the high-salinity wastewater to remove impurities such as suspended matters, colloids and Mg in the wastewater²⁺And Ca²⁺Plasma reduces the hardness and the alkalinity of waste water, improves the biodegradability of waste water, prevents scaling during subsequent concentration, and satisfies the requirement of intaking of subsequent concentration.

Further, the softening and clarifying agents used include: calcium oxide and sodium metaaluminate in a weight ratio of 1: 1. Mg in wastewater²⁺、Ca²⁺Can be reacted with Cl^-Producing a chemical reaction to produce Ca₄Al₂Cl₂(OH)₁₂Is a layered precipitate which can be removed by filtration, and Mg is present in a weight ratio of calcium oxide to sodium metaaluminate of 1:1²⁺And Ca²⁺The removal rate of (2) is highest.

Furthermore, the pH value of softening and clarifying is 8-9.5, the temperature of softening and clarifying is 20-40 ℃, and the time of softening and clarifying is 0.5-1.5 h. Under certain alkaline condition, Mg in the wastewater can be led to²⁺、Ca²⁺With Cl^-The chemical reaction is carried out more fully, and the limited temperature and time are the optimal temperature and time for leading the reaction to be more fully on the basis of the lowest energy consumption.

Further, the temperature of the pre-concentration is 500-550 ℃, and the pressure is 9.5-10.5 MPa.

Furthermore, the nanofiltration membrane adopted by the double-stage nanofiltration system is a monovalent ion selective membrane ACS-CIMS.

Further, the crystallization temperature of the sodium chloride is 10-18 ℃, and the crystallization time is 1.2-2.0 h; the crystallization temperature of the sodium sulfate is 14-22 ℃, and the crystallization time is 1.5-2.2 h.

The system used in the process for refining salt by using high-salinity wastewater comprises a softening and clarifying tank, an ozone biochar filter, a decarbonizing tower, an MVR evaporator, an ED concentration device and two-stage nanofiltration equipment which are sequentially connected, wherein the two-stage nanofiltration equipment is connected with a sodium chloride crystallizer and a sodium sulfate crystallizer.

The invention has the beneficial effects that:

according to the process for refining salt by using high-salinity wastewater, the MVR mechanical vapor recompression technology is adopted to prevent blockage caused by scaling in the concentration process, secondary vapor can be used for heating, external energy consumption is reduced, and concentration by combining an ED ion membrane enables the concentration process to be more accurate and sufficient on the basis of lowest energy consumption; the double-stage nanofiltration system is adopted to ensure that the purity of the separated salt is higher, and the pressure drop between two stages causes the booster pump between the two stages to basically not work, so the specific energy consumption of the separated salt is the lowest, and the double-stage nanofiltration system is more energy-saving than the single-stage nanofiltration system. According to the invention, through setting reasonable pretreatment, concentration, salt separation and crystallization steps and selecting optimal process parameters, the recovery rate and purity of the product salt are greatly improved on the basis of reducing production energy consumption, the purity can reach the standard of industrial salt, and the resource utilization of high-salinity wastewater is realized.

Drawings

In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.

FIG. 1 is a schematic diagram of a system for refining salt using high-salinity wastewater according to an embodiment of the present invention.

In the figure, 1-softening clarification tank, 2-ozone biochar filter tank, 3-decarbonization tower, 4-MVR evaporator, 5-ED concentration device, 6-double stage nanofiltration equipment, 7-sodium chloride crystallizer and 8-sodium sulfate crystallizer.

Detailed Description

In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

The embodiment of the invention provides a process for refining salt by using high-salinity wastewater, and as shown in figure 1, the system adopted by the process comprises a softening and clarifying tank 1, an ozone biochar filter 2, a decarbonizing tower 3, an MVR evaporator 4, an ED concentration device 5 and a two-stage nanofiltration equipment 6 which are sequentially connected, wherein the two-stage nanofiltration equipment 6 is connected with a sodium chloride crystallizer 7 and a sodium sulfate crystallizer 8.

The process specifically comprises the following steps:

(1) pretreatment: the high-salinity wastewater firstly enters a softening clarification tank 1 for softening clarification, the pH value of the softening clarification is controlled to be 8, softening clarification reagents are calcium oxide and sodium metaaluminate in a weight ratio of 1:1, the wastewater after softening clarification enters an ozone biochar filter tank 2 for catalytic oxidation, biodegradation and adsorption and activated carbon adsorption of ozone, and then enters a decarbonization tower 3 for decarbonization treatment.

(2) Concentration: the pretreated wastewater firstly enters an MVR evaporator 4 for preconcentration, the preconcentration temperature is 500 ℃, the pressure is 9.5MPa, and the wastewater enters an ED concentration device 5 for ED ion membrane concentration after the preconcentration is finished.

(3) Salt separation: after concentration, the mixture enters a double-stage nanofiltration device 6 to separate sodium chloride from sodium sulfate, and a nanofiltration membrane adopted by a double-stage nanofiltration system is a monovalent ion selective membrane ACS-CIMS.

(4) And (3) crystallization: after salt separation is finished, sodium chloride and sodium sulfate are respectively prepared through a sodium chloride crystallizer 7 and a sodium sulfate crystallizer 8, the crystallization temperature of the sodium chloride crystallizer 7 is 10 ℃, the crystallization time is 2.0 hours, the crystallization temperature of the sodium sulfate crystallizer 8 is 14 ℃, and the crystallization time is 2.2 hours.

The recovery rate of the sodium chloride and the sodium sulfate prepared by the embodiment is more than 80%, and the purity of the sodium chloride and the purity of the sodium sulfate can reach more than 99%, so that the national standard of industrial salt is met.

Example 2

The embodiment of the invention provides a process for refining salt by using high-salinity wastewater, and as shown in figure 1, the system adopted by the process comprises a softening and clarifying tank 1, an ozone biochar filter 2, a decarbonizing tower 3, an MVR evaporator 4, an ED concentration device 5 and a two-stage nanofiltration equipment 6 which are sequentially connected, wherein the two-stage nanofiltration equipment 6 is connected with a sodium chloride crystallizer 7 and a sodium sulfate crystallizer 8.

The process specifically comprises the following steps:

(1) pretreatment: the high-salinity wastewater firstly enters a softening clarification tank 1 for softening clarification, the pH value of the softening clarification is controlled at 9.5, softening clarification reagents are calcium oxide and sodium metaaluminate in a weight ratio of 1:1, the wastewater after softening clarification enters an ozone biochar filter tank 2 for catalytic oxidation, biodegradation and adsorption and activated carbon adsorption of ozone, and then enters a decarbonization tower 3 for decarbonization treatment.

(2) Concentration: the pretreated wastewater firstly enters an MVR evaporator 4 for preconcentration at the temperature of 550 ℃ and under the pressure of 10.5MPa, and then enters an ED concentration device 5 for ED ion membrane concentration after the preconcentration is finished.

(3) Salt separation: after concentration, the mixture enters a double-stage nanofiltration device 6 to separate sodium chloride from sodium sulfate, and a nanofiltration membrane adopted by a double-stage nanofiltration system is a monovalent ion selective membrane ACS-CIMS.

(4) And (3) crystallization: after salt separation is finished, sodium chloride and sodium sulfate are respectively prepared through a sodium chloride crystallizer 7 and a sodium sulfate crystallizer 8, the crystallization temperature of the sodium chloride crystallizer 7 is 18 ℃, the crystallization time is 1.2 hours, the crystallization temperature of the sodium sulfate crystallizer 8 is 22 ℃, and the crystallization time is 1.5 hours.

The recovery rate of the sodium chloride and the sodium sulfate prepared by the embodiment is more than 80%, and the purity of the sodium chloride and the purity of the sodium sulfate can reach more than 99%, so that the national standard of industrial salt is met.

Although the present invention has been described in detail by referring to the drawings in connection with the preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made on the embodiments of the present invention by those skilled in the art without departing from the spirit and scope of the present invention, and these modifications or substitutions are within the scope of the present invention/any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.