1. A brine refining process interposed between a conventional primary refined brine and a conventional secondary refined brine, the brine refining process comprising the steps of:

1) removing free chlorine: adding sodium sulfite into brine treated by a primary brine refining system to remove free chlorine in the brine;

2) pressurizing: pressurizing the effluent adjusted in the step 1) by a pressurizing pump, wherein the pressurizing pressure is less than or equal to 4.0 MPa;

3) concentration: pressurizing the salt water in the step 2), performing high-temperature nanofiltration, wherein the nanofiltration is one-stage or multi-stage concentration filtration, and the water quality of the penetrating fluid discharged by filtration reaches Ca²⁺+Mg²⁺≤0.5mg/L，SS≤0.3mg/L，SO4^2-≤4g/L。

2. A brine refining process interposed between a conventional primary refined brine and a conventional secondary refined brine, the brine refining process comprising the steps of:

0) and (3) pH adjustment: adjusting the pH value of effluent after refining the primary brine to 3-8 by adding hydrochloric acid;

1) removing free chlorine: adding sodium sulfite into the saline water with the pH value adjusted in the step 1) to remove free chlorine in the saline water;

2) pressurizing: pressurizing the effluent adjusted in the step 1) by a pressurizing pump, wherein the pressurizing pressure is less than or equal to 4.0 MPa;

3) concentration: pressurizing the salt water in the step 2), performing high-temperature nanofiltration, wherein the nanofiltration is one-stage or multi-stage concentration filtration, and the water quality of the penetrating fluid discharged by filtration reaches Ca²⁺+Mg²⁺≤0.5mg/L，SS≤0.3mg/L，SO4^2-The pH value can enter a pH readjustment stage when the concentration is less than or equal to 4 g/L;

4) and (3) readjusting the pH: the penetrating fluid is subjected to alkali addition to adjust the pH value to 8-11, and then the traditional secondary brine refining stage can be carried out.

3. A brine refining method as defined in claim 1 or 2, further comprising in step 1):

temperature regulation: the effluent temperature after the treatment of the traditional primary brine refining system is adjusted to be less than or equal to 70 ℃.

4. A brine purification method as claimed in claim 1 or 2, wherein said temperature regulation is provided before or after the removal of free chlorine in step 1).

5. A brine refining method as claimed in claim 1 or 2, wherein said multiple stages of concentration and filtration are connected in series, the concentrated solution in the first stage is used as the feed solution for the second stage, and the concentrated solution in the second stage is used as the feed solution for the next stage, and the permeate in each stage is continuously discharged and enters the conventional secondary brine refining system.

6. A brine refining method as claimed in claim 1 or 2, wherein said multiple stages of concentration and filtration are connected in parallel, and the concentrated solution in each stage is filtered and the recovered solution is collected, combined and fed into a conventional secondary brine refining system.

7. A brine purification method as claimed in claim 1 or 2, wherein said multiple stage concentration filtration is a combination of series and parallel filtration.

8. A brine purification method as claimed in claim 1 or 2, wherein said high temperature nanofiltration is modified high temperature refined brine nanofiltration (HX-MNF).

9. A novel method for refining MNF from brine, comprising the method for refining brine according to any one of claims 1 to 8, and sequentially comprising treatment of a salt dissolving tank or a brine tank, reaction of a front tank and a rear tank, membrane filtration, and conventional primary brine refining reaction before the brine refining step; the brine refining step sequentially comprises chelating resin tower reaction and traditional secondary refined brine treatment.

Background

Brine refining is the source of chlor-alkali enterprises, is the prerequisite of the normal operation of electrolysis trough, the technological process of chlor-alkali enterprises is primary brine refining, secondary brine refining, electrolysis and subsequent processes, brine refining is to remove the impurity ions such as calcium ion, magnesium ion, sulfate radical in the original salt or brine, reach the brine index requirement that satisfies the electrolysis trough operation, along with the requirement of chemical industry enterprise zero release in recent years, organic matter TOC in the brine also exceeds standard occasionally, bring passivity to current brine refining technology, can't satisfy the electrolysis trough operation requirement, lead to chlor-alkali enterprise core equipment electrolysis trough can't long-term operation, consequently, require a new brine refining technique to solve these problems, in order to adapt to the new demand of chlor-alkali industry brine refining.

The existing primary brine refining technology in the chlor-alkali industry is to add excessive sodium carbonate and calcium ions into brine for reaction, add excessive sodium hydroxide and magnesium ions for reaction, control the total amount of calcium and magnesium ions and suspended solids SS below 1mg/L through filtration, remove sulfate radicals through denitration by a crude brine barium method or denitration by a dilute brine membrane method after electrolysis, usually control the sulfate radicals of a brine system below 7g/L to meet requirements, secondary brine refining is to adsorb primary brine through a chelating resin tower, further remove calcium and magnesium ions and the like, finally control the content of calcium and magnesium ions below 0.02mg/L to meet the running requirements of an electrolytic cell, the total TOC of the brine entering the electrolytic cell is required to be below 7mg/L, but no effective method for removing the TOC in the brine exceeding standard in the industry exists at present, the continuous TOC exceeding standard can greatly reduce the service life of an ionic membrane, if the new technology is used for removing sulfate radicals, calcium and magnesium ions, suspended substances SS and TOC in the primary refined brine at one time, the service life of the ionic membrane is greatly prolonged, which is a revolutionary breakthrough of the brine refining technology in the chlor-alkali industry.

Disclosure of Invention

The invention aims to solve the technical problem of providing a brine refining method, which refines primary refined brine again, and intercepts high-valence ions such as sulfate radicals, trace calcium carbonate, magnesium hydroxide, TOC, calcium ions, magnesium ions, aluminum ions, iron ions and other suspended matters in refined brine to achieve the aim of refining the brine again.

The technical problem to be solved by the invention is realized by the following technical scheme:

a brine refining process interposed between a conventional primary refined brine and a conventional secondary refined brine, the brine refining process comprising the steps of:

1) removing free chlorine: adding sodium sulfite into brine treated by a primary brine refining system to remove free chlorine in the brine;

2) pressurizing: pressurizing the effluent adjusted in the step 1) by a pressurizing pump, wherein the pressurizing pressure is less than or equal to 4.0 MPa;

3) concentration: pressurizing the salt water in the step 2), performing high-temperature nanofiltration, wherein the nanofiltration is one-stage or multi-stage concentration filtration, and the water quality of the penetrating fluid discharged by filtration reaches Ca²⁺+Mg²⁺≤0.5mg/L，SS≤0.3mg/L，SO4^2-≤4g/L。

The other technical problem to be solved by the invention is realized by the following technical scheme:

a brine refining process interposed between a conventional primary refined brine and a conventional secondary refined brine, the brine refining process comprising the steps of:

0) and (3) pH adjustment: adjusting the pH value of effluent after refining the primary brine to 3-8 by adding hydrochloric acid;

1) removing free chlorine: adding sodium sulfite into the saline water with the pH value adjusted in the step 1) to remove free chlorine in the saline water;

2) pressurizing: pressurizing the effluent adjusted in the step 1) by a pressurizing pump, wherein the pressurizing pressure is less than or equal to 4.0 MPa;

3) concentration: pressurizing the salt water in the step 2), performing high-temperature nanofiltration, wherein the nanofiltration is one-stage or multi-stage concentration filtration, and the water quality of the penetrating fluid discharged by filtration reaches Ca²⁺+Mg²⁺≤0.5mg/L，SS≤0.3mg/L，SO4^2-The pH value can enter a pH readjustment stage when the concentration is less than or equal to 4 g/L;

4) and (3) readjusting the pH: the penetrating fluid is subjected to alkali addition to adjust the pH value to 8-11, and then the traditional secondary brine refining stage can be carried out.

Preferably, the step 1) further comprises: temperature regulation: the effluent temperature after the treatment of the traditional primary brine refining system is adjusted to be less than or equal to 70 ℃.

Preferably, the temperature regulation is provided before or after the removal of free chlorine in step 1).

Preferably, the multistage concentration filtration is in series connection, the concentrated solution of the first section is used as the feed solution of the second section, the concentrated solution of the second section is used as the feed solution of the next section, and the penetrating fluid of each section is continuously discharged and enters a traditional secondary brine refining system.

Preferably, the multistage concentration filtration is parallel connection, and the concentrated solution of each stage is filtered, collected and recycled, and then combined to enter a traditional secondary brine refining system.

Preferably, the multistage concentration filtration is combined series and parallel filtration.

Preferably, the high-temperature nanofiltration is modified high-temperature refined brine nanofiltration (HX-MNF).

The invention aims to solve the other technical problem by adopting the following technical scheme:

a novel method for refining MNF from brine, comprising the method for refining brine according to any one of claims 1 to 8, and sequentially comprising treatment of a salt dissolving tank or a brine tank, reaction of a front tank and a rear tank, membrane filtration, and conventional primary brine refining reaction before the brine refining step; the brine refining step sequentially comprises chelating resin tower reaction and traditional secondary refined brine treatment.

The technical scheme of the invention has the following beneficial effects:

(1) the method realizes the denitration of the refined brine, replaces the traditional low-temperature dilute brine denitration, not only saves energy, but also solves the problem that the domestic brine electrolysis is difficult to denitrate;

(2) the modified high-temperature nanofiltration membrane process technology can replace the traditional low-temperature nanofiltration membrane technology, the consumption of steam is reduced, and the steam cost is saved by about 150 ten thousand yuan each year by taking a 20 ten thousand ton caustic soda device as an example;

(3) organic substances TOC in the brine can be directly removed, and a new method is provided for zero emission and waste salt electrolysis of chlor-alkali enterprises;

(4) the method can remove trace particulate matters such as calcium carbonate, magnesium hydroxide and the like in the brine, can also remove high-valence metal ions such as calcium ions, magnesium ions and the like and anions, and greatly improves the quality of the brine, so that the current efficiency of chlor-alkali enterprises can be greatly improved, the unit production cost is reduced, the service life of the ionic membrane is prolonged, and the value is created for the chlor-alkali enterprises.

Drawings

Fig. 1 is a flow diagram of a conventional brine refining process.

Fig. 2 is a flow diagram of a brine refining process incorporating the present application.

Detailed Description

Specific examples of the invention are described in detail below to facilitate a further understanding of the invention.

All experimental procedures used in the following examples are conventional unless otherwise specified. Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.

Fig. 1 is a flow diagram of a conventional brine refining process. As shown in the figure, the traditional primary refined brine in the prior art enters the chelating resin tower to carry out traditional secondary refined brine. Fig. 2 is a flow diagram of a brine refining process incorporating the present application. The method is established on the basis of the traditional brine process, the primary refined brine is refined again, and a series of advanced technologies such as constant-letter Runfeng modified high-temperature brine nanofiltration (sold in the market) are utilized to intercept high-valence ions such as sulfate radicals, trace calcium carbonate, magnesium hydroxide, TOC, calcium ions, magnesium ions, aluminum ions, iron ions, silicon dioxide and other suspended matters in the refined brine so as to achieve the purpose of refining the brine again. Provides a new idea and method for zero emission of chlor-alkali enterprises.

Example 1

A brine refining method is arranged between traditional primary refined brine and traditional secondary refined brine, and comprises the following steps:

1) and (3) pH adjustment: adjusting the pH value of effluent after refining the primary brine to 3-8 by adding hydrochloric acid;

2) removing free chlorine: adding sodium sulfite into the saline water with the pH value adjusted in the step 11) to remove free chlorine in the saline water;

3) pressurizing: pressurizing the effluent adjusted in the step 1) by a pressurizing pump, wherein the pressurizing pressure is less than or equal to 4.0 MPa;

4) concentration: after the brine is pressurized in the step 2), the modified high-temperature refined brine is subjected to nanofiltration (HX-MNF), the nanofiltration is primary filtration, and the water quality of penetrating fluid discharged by the filtration reaches Ca²⁺+Mg²⁺≤0.5mg/L，SS≤0.3mg/L，SO4^2-The pH readjustment stage can be started when the concentration is less than or equal to 4 g/L;

5) and (3) readjusting the pH: and adjusting the pH value of the penetrating fluid to 8-11 by adding alkali, and then entering a secondary brine refining stage.

Example 2

A brine refining method is arranged between traditional primary refined brine and traditional secondary refined brine, and comprises the following steps:

1) removing free chlorine: removing free chlorine in the brine by adding sodium sulfite;

2) pressurizing: pressurizing the effluent adjusted in the step 1) by a pressurizing pump, wherein the pressurizing pressure is less than or equal to 4.0 MPa;

3) concentration: after the brine is pressurized in the step 2), the modified high-temperature refined brine is subjected to nanofiltration (HX-MNF), the nanofiltration is primary filtration, and the water quality of penetrating fluid discharged by the filtration reaches Ca²⁺+Mg²⁺≤0.5mg/L，SS≤0.3mg/L，SO4^2-The refining stage of secondary brine can be carried out when the concentration is less than or equal to 4 g/L.

Example 3

A brine refining method is arranged between traditional primary refined brine and traditional secondary refined brine, and comprises the following steps:

1) and (3) pH adjustment: adjusting the pH value of effluent after refining the primary brine to 3-8 by adding hydrochloric acid;

2) removing free chlorine: adding sodium sulfite into the saline water with the pH value adjusted in the step 11) to remove free chlorine in the saline water;

3) temperature regulation: adjusting the temperature of effluent water treated by a traditional primary brine refining system to be less than or equal to 70 ℃;

4) pressurizing: pressurizing the effluent adjusted in the step 1) by a pressurizing pump, wherein the pressurizing pressure is less than or equal to 4.0 MPa;

5) concentration: after the brine is pressurized in the step 2), performing nanofiltration (HX-MNF) on modified high-temperature refined brine, wherein the nanofiltration is multi-stage filtration, the multi-stage concentration filtration is series connection, the concentrated solution of the first stage is used as the feed solution of the second stage, the concentrated solution of the second stage is used as the feed solution of the next stage, the penetrating fluid of each stage is continuously discharged, and the water quality of the penetrating fluid discharged by filtration reaches Ca²⁺+Mg²⁺≤0.5mg/L，SS≤0.3mg/L，SO4^2-The pH readjustment stage can be carried out when the concentration is less than or equal to 4 g/L.

6) And (3) readjusting the pH: and adjusting the pH value of the penetrating fluid to 8-11 by adding alkali, and then entering a secondary brine refining stage.

Example 4

A brine refining method is arranged between traditional primary refined brine and traditional secondary refined brine, and comprises the following steps:

1) removing free chlorine: removing free chlorine in the brine by adding sodium sulfite;

2) temperature regulation: adjusting the temperature of effluent water treated by a traditional primary brine refining system to be less than or equal to 70 ℃;

3) pressurizing: pressurizing the effluent adjusted in the step 1) by a pressurizing pump, wherein the pressurizing pressure is less than or equal to 4.0 MPa;

4) concentration: after the brine is pressurized in the step 2), performing nanofiltration (HX-MNF) on modified high-temperature refined brine, wherein the nanofiltration is multi-stage filtration, the multi-stage concentration filtration is series connection, the concentrated solution of the first stage is used as the feed solution of the second stage, the concentrated solution of the second stage is used as the feed solution of the next stage, the penetrating fluid of each stage is continuously discharged, and the water quality of the penetrating fluid discharged by filtration reaches Ca²⁺+Mg²⁺≤0.5mg/L，SS≤0.3mg/L，SO4^2-≤4gthe/L can enter a secondary brine refining stage.

Example 5

A brine refining method is arranged between traditional primary refined brine and traditional secondary refined brine, and comprises the following steps:

1) temperature regulation: adjusting the temperature of effluent water treated by a traditional primary brine refining system to be less than or equal to 70 ℃;

2) and (3) pH adjustment: adjusting the pH value of effluent after refining the primary brine to 3-8 by adding hydrochloric acid;

3) removing free chlorine: adding sodium sulfite into the saline water with the pH value adjusted in the step 11) to remove free chlorine in the saline water;

4) pressurizing: pressurizing the effluent adjusted in the step 1) by a pressurizing pump, wherein the pressurizing pressure is less than or equal to 4.0 MPa;

5) concentration: after the brine is pressurized in the step 2), modified high-temperature refined brine nanofiltration (HX-MNF) is carried out, the nanofiltration is multi-stage filtration, the multi-stage concentration filtration is a mode of combining series connection and parallel connection, the concentrated solution in the first stage is used as the feed solution in the second stage, the concentrated solution in the second stage is used as the feed solution in the next stage, penetrating fluid in each stage is continuously discharged, and the water quality of the penetrating fluid discharged by filtration reaches Ca²⁺+Mg²⁺≤0.5mg/L，SS≤0.3mg/L，SO4^2-The pH readjustment stage can be carried out when the concentration is less than or equal to 4 g/L.

6) And (3) readjusting the pH: the penetrating fluid is added with alkali to adjust the pH value to 8-11, and then the penetrating fluid can enter a secondary brine refining system.

Example 6

A brine refining method is arranged between traditional primary refined brine and traditional secondary refined brine, and comprises the following steps:

1) temperature regulation: adjusting the temperature of effluent water treated by a traditional primary brine refining system to be less than or equal to 70 ℃;

2) removing free chlorine: removing free chlorine in the brine by adding sodium sulfite;

3) pressurizing: pressurizing the effluent adjusted in the step 1) by a pressurizing pump, wherein the pressurizing pressure is less than or equal to 4.0 MPa;

4) concentration: after the brine is pressurized in the step 2), modified high-temperature refined brine nanofiltration (HX-MNF) is carried out, the nanofiltration is multi-stage filtration, the multi-stage concentration filtration is a mode of combining series connection and parallel connection, the concentrated solution in the first stage is used as the feed solution in the second stage, the concentrated solution in the second stage is used as the feed solution in the next stage, penetrating fluid in each stage is continuously discharged, and the water quality of the penetrating fluid discharged by filtration reaches Ca²⁺+Mg²⁺≤0.5mg/L，SS≤0.3mg/L，SO4^2-The refining stage of secondary brine can be carried out when the concentration is less than or equal to 4 g/L.

Example 7

A novel brine refining MNF process comprising: salt dissolving pool or brine pool treatment, front and back tank reaction, membrane filtration, traditional primary refined brine reaction, brine refining method, chelating resin tower reaction and traditional secondary refined brine treatment.

The above processes are all carried out by conventional methods, wherein the brine refining process may be carried out by any of the above examples.

The method utilizes a Hengxin Runfeng modified high-temperature refined brine nanofiltration (HX-MNF) (sold in the market) system to treat the brine, and intercepts and refines high-valence ions such as sulfate radicals, trace calcium carbonate, magnesium hydroxide, TOC, calcium ions, magnesium ions, aluminum ions, iron ions, silicon dioxide and other suspended matters in the brine. The system improves the processing capacity and the recovery rate, reduces the operation pressure and the cost of the membrane element as much as possible, and adopts a multi-section type series arrangement system. After the brine is pressurized, the brine enters a membrane shell of a first section, the concentrated solution of the first section is used as the feed solution of a second section, the concentrated solution of the second section is used as the feed solution of the next section, and the penetrating fluid of each section is continuously discharged and enters a refined brine system. The system is in modular design, the membrane shell, the pipeline, the valve, the instrument and the control panel are all installed in a steel frame, and the system is very convenient to control automatically, operate and maintain. The material inlet and the material outlet of the system are provided with flow detection and pressure alarm, and the flow of the booster pump is controlled by the pressure of the concentrated solution outlet.

Although the present invention has been described with reference to the above embodiments, it should be understood that the present invention is not limited thereto, and various changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the present invention.