CN110723857B - A high salt water concentration crystallization treatment system and process - Google Patents

Abstract

The invention relates to the technical field of sewage discharge, in particular to a high-salinity water concentration and crystallization treatment system and a high-salinity water concentration and crystallization treatment process. The treatment system sequentially comprises a sewage collecting tank, a pretreatment device, a flocculation and precipitation device, an ultrafiltration device, a reverse osmosis device and an MVR evaporation and concentration device according to a treatment use sequence, wherein the MVR evaporation and concentration device sequentially comprises a plate heat exchanger, a first precipitation and crystallization tank, a second precipitation and crystallization tank and a feed liquid circulating pump according to the treatment use sequence, and a steam outlet end of the first precipitation and crystallization tank and a steam outlet end of the second precipitation and crystallization tank are communicated with the plate heat exchanger through a steam compressor; the plate heat exchanger is provided with a feed end, and the feed end of the plate heat exchanger is communicated with the output end of the reverse osmosis device through a feed pipeline. The high-salinity water concentration crystallization treatment system is novel in structure and simple to operate, crystals of high-salinity water basically precipitate, crystallize and grow at the bottoms of the first precipitation crystallizing tank and the second precipitation crystallizing tank, and the completeness of the crystals is guaranteed.

Description

A high salt water concentration crystallization treatment system and process

technical field

The invention relates to the technical field of sewage discharge, in particular to a high salt water concentration and crystallization treatment system and process.

Background technique

In recent years, in order to save the cost of concentration, many companies, MVR production companies and multi-effect concentration companies have carried out research and production experiments on concentrated crystallization with zero discharge of sewage. During the process of research and production experiments, they all obtained the same result: The crystal particles of the mixed salt are too fine, the concentrated liquid is a turbid liquid, the liquid-solid separation is difficult, the pipelines and heat exchangers in the production process are seriously blocked, and the crystal dehydration is difficult, so that the zero discharge cannot be implemented and operated in a sustainable and benign manner.

Because the concentrated crystalline crystal of reverse osmosis concentrated water has the defects of small crystal particles and poor mechanical strength of the crystalline crystal, in the production process of MVR, the feed liquid is forced to circulate by the forced circulation pump, because the separator does not promote the crystal and solution. The separation device or the lack of an effective separation device makes the separation of the crystal and the solution incomplete. In addition, the inlet of the circulating pump is located at the bottom of the separator. During the circulation process, the crystal is continuously circulated in the circulation pipeline with the feed liquid, and the crystal is In the process of circulation, it is continuously subjected to high-speed shearing by the impeller of the circulating pump, which causes the crystals to be continuously broken, resulting in fine crystal particles or the formation of suspending concentrated liquid, which makes the liquid-solid separation difficult.

SUMMARY OF THE INVENTION

In order to overcome the shortcomings and deficiencies in the prior art, the purpose of the present invention is to provide a high-salt water concentration and crystallization treatment system, which has a novel structure and simple operation, so that the crystals of the high-salt water are basically in the first precipitation crystallizing tank and the second crystallizing tank. The bottom of the second precipitation crystallizing tank is precipitated and crystallized, which avoids shearing by the impeller of the material-liquid circulating pump, ensures the integrity of the crystal, and the crystal can continue to grow into larger crystal particles in the precipitation chamber; The circulation of steam and the circulation of material and liquid improves the utilization rate of raw materials.

The purpose of the present invention is to provide a high-salt water concentration crystallization treatment process, which is simple to operate, and enables crystals to form and grow at the bottom of the tank body of the first precipitation crystallization tank and the second precipitation crystallization tank, avoiding the circulation of material and liquid The impeller of the pump shears it to ensure the integrity of the crystal, which is suitable for large-scale processing.

The object of the present invention is achieved through the following technical solutions: a high-salt water concentration and crystallization treatment system, which sequentially includes a sewage collection tank, a pretreatment device, a flocculation sedimentation device, an ultrafiltration device, a reverse osmosis device, and an MVR evaporation and concentration device according to the order of treatment and use. , the MVR evaporation and concentration device sequentially includes a plate heat exchanger, a first precipitation crystallization tank, a second precipitation crystallization tank and a material-liquid circulation pump according to the order of processing and use. The steam outlet end of the crystallization tank is connected with the plate heat exchanger through the steam compressor; the plate heat exchanger is provided with a feed end, and the feed end of the plate heat exchanger is communicated with the output end of the reverse osmosis device through a feed pipe .

In the present invention, the crystal is precipitated and crystallized by arranging the first precipitation and crystallization tank and the second precipitation and crystallization tank, and the method of material liquid circulation is adopted, so that the material liquid is circulated through the first precipitation and crystallization tank and the second precipitation and crystallization tank for many times, wherein the material The liquid overflows from the first precipitation and crystallization tank to the second precipitation and crystallization tank, and the mixed salt crystals are precipitated at the bottom of the two tanks respectively, which avoids the crystals being sheared by the impeller when they pass through the centrifugal pump or the circulating pump, which will damage the crystals. Integrity, make the crystal grow at the bottom of the tank, ensure the integrity of the crystal, and then realize the easy separation of the salt component in the feed liquid. Wherein, the high salt water includes salt components such as sodium sulfate, sodium carbonate, sodium chloride, etc., through the secondary precipitation separation method of the present invention, the salt components in the high salt water are precipitated and crystallized at the bottom of the tank to form mixed salt Crystals.

On the other hand, in each cycle, part of the feed liquid is evaporated in the first precipitation crystallization tank and the second precipitation crystallization tank, and is circulated to the steam compressor through the steam outlet end of the tank for compression. The heat energy increases, and flows into the plate heat exchanger again to provide heat energy, which provides heat energy for the preheating of the material liquid in the plate heat exchanger, reduces the external energy consumption for providing heat energy to the plate heat exchanger, and saves energy consumption.

Preferably, the plate heat exchanger is also provided with a circulating feed liquid inlet end and a circulating feed liquid outlet end, and a first feed end and a first feed liquid outlet end are provided in the upper middle and upper part of the first precipitation and crystallization tank, so The middle and upper part of the second precipitation crystallization tank is provided with a second feed end and a second feed liquid outlet end;

The inlet end of the circulating feed liquid of the plate heat exchanger is communicated with the first feed end of the first precipitation and crystallization tank through the feeding pipeline, and the second feed end of the second precipitation and crystallization tank is connected to the other through the connecting pipeline. The first material and liquid outlet end of the first precipitation and crystallization tank is communicated, and the second material and liquid outlet end of the second precipitation and crystallization tank is communicated with the inlet end of the material and liquid circulating pump through the first circulation pipeline. The outlet end of the circulation pump is communicated with the inlet end of the circulating feed liquid of the plate heat exchanger through the second circulation pipeline.

Through the above-mentioned components, the present invention makes the feed liquid circulate among the plate heat exchanger, the first precipitation crystallization tank, the second precipitation crystallization tank, and the feed liquid circulating pump, and then circulates through the first precipitation crystallization tank and the second precipitation crystallization tank. The crystallizing tank makes the salt components in the feed liquid precipitate and crystallize at the bottom of the tank body. After many cycles, the mixed salt crystals are formed and grown at the bottom of the tank body, avoiding the crystals passing through the centrifugal pump or circulating pump. The integrity of the crystal is damaged by shearing, so that the crystal grows at the bottom of the tank, which ensures the integrity of the crystal and realizes the easy separation of the salt component in the feed liquid. Wherein, a feeding pump is arranged on the feeding pipeline to pump the feed liquid in the plate heat exchanger into the first precipitation and crystallization tank.

Preferably, the plate heat exchanger is further provided with a circulating steam inlet end, the upper part of the first precipitation and crystallization tank is provided with a first steam outlet end, and the upper part of the second precipitation and crystallization tank is provided with a second steam outlet end ;

The first steam outlet end of the first precipitation and crystallization tank is communicated with the inlet end of the steam compressor through a first steam pipe, and the second steam outlet end of the second precipitation and crystallization tank is communicated with the steam compressor through a second steam pipe. The inlet end of the steam compressor is communicated, and the outlet end of the steam compressor is communicated with the circulating steam inlet end of the plate heat exchanger through a circulating steam pipeline.

In the present invention, through the above-mentioned components, the steam in the feed liquid flows to the steam compressor through the first steam outlet end, the first steam pipe, the second steam outlet end and the second steam pipe for compression, and the compressed feed liquid steam is compressed. The heat energy increases, and flows into the plate heat exchanger again to provide heat energy, providing heat energy for the preheating of the material liquid in the plate heat exchanger, reducing the external energy consumption for providing heat energy to the plate heat exchanger, saving energy, and realizing Recycling of resources. Wherein, the ends of the first steam pipe and the second steam pipe are connected with a steam confluence pipe to confluence the steam to the inlet end of the steam compressor.

Preferably, the plate heat exchanger is further provided with a condensed water outlet end, and the condensed water outlet end is connected with a condensed water storage tank through a condensed water pipeline, and the condensed water pipeline is provided with a first valve.

In the present invention, the heat energy of the feed liquid vapor compressed by the steam compressor increases, and flows into the plate heat exchanger again to provide heat energy. After the feed liquid vapor provides heat energy, its own heat energy is reduced, cooled and condensed into condensed water. The water outlet end and the condensed water pipeline flow and are stored in the condensed water storage tank. The condensed water is collected and can be reused for cooling of the steam compressor and the material-liquid circulation pump, which improves the material recycling rate in the system and reduces the external influence on the steam. The energy consumed by the compressor and the liquid circulating pump for cooling saves energy consumption and realizes the recycling of resources.

Wherein, the set first valve can easily control the flow rate of the condensed water.

Preferably, the feeding pipeline is provided with a feeding pump, which can pump the feed liquid in the plate heat exchanger to the first precipitation crystallization tank, so as to improve the power of the circulation process of the feed liquid and avoid the mixed salt crystals in the plate heat exchange. Deposition in the device, high practicability.

Preferably, both the first precipitation and crystallization tank and the second precipitation and crystallization tank are provided with spiral guide vanes, which guide the feed liquid with higher heat to the bottom of the tank body, so that the crystal body is at the bottom of the tank body with the mother liquor and the mother liquid. The steam is separated, the crystals sink to the bottom and continue to grow, and the steam rises and overflows to the steam compressor for compression and reuse.

Another object of the present invention is achieved through the following technical solutions: a process for applying the above-mentioned high brine concentration crystallization treatment system, comprising the steps:

(1) The factory sewage is collected in the sewage collection tank, and the oil and slag removal treatment is carried out through the pretreatment device, and then the impurity removal treatment is carried out through the flocculation sedimentation device, the ultrafiltration device and the reverse osmosis device; wherein, the flocculation sedimentation device is a To remove suspended solids in sewage, the ultrafiltration device has a filtration accuracy of 10nm, which can filter fine impurities in sewage. The reverse osmosis device adopts an ion membrane with a filtration accuracy of 0.1nm, which can filter out more than 90% of dissolved salts and remove a large amount of impurities. , so that the high brine feed liquid entering the MVR evaporation and concentration device can be deposited to form a complete crystal.

(2) the feed liquid after the impurity removal treatment in step (1) enters the plate heat exchanger through the feed end of the plate heat exchanger for heating and heating, and then flows into the first precipitation crystallization tank and the second precipitation crystallization tank for precipitation separation , and the separated feed liquid is pumped into the plate heat exchanger through the feed liquid circulation pump to heat up again for recirculating precipitation and separation;

At the same time, the heated feed liquid is evaporated in the first precipitation crystallization tank and the second precipitation crystallization tank, and the evaporated steam is compressed and processed by the steam compressor and circulated to the plate heat exchanger to provide heat energy to the feed liquid;

After several cycles of precipitation and separation, the high brine is concentrated and crystallized at the bottom of the first precipitation crystallization tank and the second precipitation crystallization tank to obtain mixed salt crystals.

Preferably, in the step (2), the feed liquid is heated to 85-100° C. in the plate heat exchanger and then enters the first precipitation crystallization tank and the second precipitation crystallization tank for cyclic precipitation and separation.

In the existing water treatment process, the concentrated water treated by reverse osmosis mainly contains soluble salts such as sodium and potassium and part of COD. It is complex, the salt produced is mixed salt, and the particles of mixed salt crystals are relatively small, about 60-80 mesh. The mechanical strength of the crystal is average, and it is easily broken into small particles by external force. During the circulation process, it is continuously subjected to high-speed shearing by the impeller of the circulating pump, which causes the crystals to break continuously and form fine-grained crystals, which makes the concentrated liquid form a suspension, which is difficult to separate solid-liquid. Dehydration is difficult.

Therefore, in the present invention, by setting the first precipitation crystallization tank and the second precipitation crystallization tank, the feed liquid enters the first precipitation crystallization tank and the second precipitation crystallization tank for precipitation and separation after being heated and heated through the plate heat exchanger. Part of the steam volatilizes to form secondary steam, and the secondary steam is compressed by the steam compressor, the heat energy of the secondary steam increases, and enters the plate heat exchanger again to provide heat energy for the plate heat exchanger, using the secondary steam compression The latter heat energy heats the material and liquid circulated to the plate heat exchanger, which improves the circulation utilization rate of steam heat energy. After the steam provides heat energy for the heating of the material liquid, its own heat energy is reduced, cooled and condensed into condensed water, which flows through the condensed water outlet end and the condensed water pipeline and is stored in the condensed water storage tank. The condensed water is collected and can be used again. The cooling of the steam compressor and the material-liquid circulation pump improves the material circulation utilization rate in the system, reduces the energy consumed by the external cooling of the steam compressor and the material-liquid circulation pump, saves energy consumption, and realizes the recycling of resources.

After precipitation and crystallization through the first precipitation and crystallization tank and the second precipitation and crystallization tank, the feed liquid is precipitated and separated at the bottom of the tank to form high brine crystals, and the high brine crystals basically stay in the first precipitation and crystallization tank and the second precipitation. The bottom of the crystallizing tank avoids the shearing of it by the impeller of the material-liquid circulating pump, ensuring the integrity of the crystal, and the crystal can continue to grow into larger crystal particles in the precipitation chamber.

Among them, spiral guide vanes are arranged inside the tanks of the first precipitation and crystallization tank, which can guide the newly pumped superheated liquid to the bottom of the chamber, and then the crystals are mixed with the mother liquor and water at the bottom of the first precipitation and crystallization tank. The steam is separated, the crystal sinks to the bottom and continues to grow, the mother liquor rises to the overflow port and overflows to the second precipitation and crystallization tank, and the water vapor rises and overflows the water surface and is compressed and reused by the compressor again, which improves the utilization rate of raw materials.

The beneficial effects of the present invention are as follows: the high-salt water concentration and crystallization treatment system of the present invention has a novel structure and simple operation, so that the crystals of the high-salt water are basically precipitated and crystallized at the bottoms of the first precipitation and crystallization tanks and the second precipitation and crystallization tanks, thereby avoiding the need for The impeller of the material-liquid circulation pump shears it to ensure the integrity of the crystals, and the crystals can continue to grow into larger crystal particles in the precipitation chamber; at the same time, through the circulation of steam and material and liquid, the utilization of raw materials is improved. Rate.

The high-salt water concentration and crystallization treatment process of the invention is simple to operate, can make the crystals form and grow at the bottom of the first precipitation crystallization tank and the second precipitation crystallization tank, avoid the impeller of the material-liquid circulating pump to shear it, and ensure the The integrity of the crystals realizes zero discharge of sewage and recycling of resources. The treatment process does not need to add any precipitation aids to obtain well-crystallized crystals, which are suitable for large-scale treatment.

Description of drawings

Fig. 1 is the structural block diagram of the present invention;

Fig. 2 is the structural representation of the MVR evaporation and concentration device of the present invention;

The reference numerals are: 1—sewage collection tank, 2—pretreatment device, 3—flocculation sedimentation device, 4—ultrafiltration device, 5—reverse osmosis device, 6—MVR evaporation and concentration device, 61—plate heat exchanger, 611 -Feeding pipeline, 62-The first precipitation crystallizing tank, 621-Feeding pipeline, 6211-Feeding pump, 622-Connecting pipeline, 623-The first steam pipeline, 63-The second precipitation crystallizing tank, 631-The first circulation Pipes, 632—the second steam pipe, 633—the steam confluence pipe, 64—the liquid circulation pump, 641—the second circulation pipe, 65—the steam compressor, 651—the circulating steam pipe, 66—the condensed water pipe, 67—the first One valve, 68—condensate storage tank, 69—spiral guide vane.

Detailed ways

In order to facilitate the understanding of those skilled in the art, the present invention will be further described below with reference to the embodiments and accompanying drawings 1-2, and the content mentioned in the embodiments does not limit the present invention.

Example 1

Referring to the accompanying drawings 1-2, a high-salt water concentration and crystallization treatment system includes sewage collection tank 1, pre-treatment device 2, flocculation and sedimentation device 3, ultrafiltration device 4, reverse osmosis device 5, MVR evaporation concentration in sequence according to the order of treatment and use Device 6, the MVR evaporation and concentration device 6 sequentially includes a plate heat exchanger 61, a first precipitation and crystallization tank 62, a second precipitation and crystallization tank 63 and a feed liquid circulation pump 64 according to the order of processing and use. The first precipitation and crystallization tank 62 The steam outlet end and the steam outlet end of the second precipitation crystallization tank 63 are all communicated with the plate heat exchanger 61 through the steam compressor 65; The end communicates with the output end of the reverse osmosis device 5 through the feed pipe 611 .

The plate heat exchanger 61 is also provided with a circulating feed liquid inlet end and a circulating feed liquid outlet end. The middle and upper part of the second precipitation crystallization tank 63 is provided with a second feed end and a second feed liquid outlet end;

The inlet end of the circulating feed liquid of the plate heat exchanger 61 is communicated with the first feeding end of the first precipitation and crystallization tank 62 through the feeding pipeline 621, and the second feeding end of the second precipitation and crystallization tank 63 passes through. The connecting pipe 622 is communicated with the first material liquid outlet end of the first precipitation and crystallization tank 62, and the second material liquid outlet end of the second precipitation and crystallization tank 63 communicates with the material liquid circulation pump 64 through the first circulation pipe 631. The inlet end of the feed liquid circulating pump 64 is communicated with the inlet end of the circulating feed liquid of the plate heat exchanger 61 through the second circulation pipeline 641 .

The plate heat exchanger 61 is also provided with a circulating steam inlet end, the upper part of the first precipitation crystallization tank 62 is provided with a first steam outlet end, and the upper part of the second precipitation crystallization tank 63 is provided with a second steam outlet end ;

The first steam outlet end of the first precipitation and crystallization tank 62 is communicated with the inlet end of the steam compressor 65 through the first steam pipeline 623, and the second steam outlet end of the second precipitation and crystallization tank 63 passes through the second steam The pipeline 632 communicates with the inlet end of the steam compressor 65 , and the outlet end of the steam compressor 65 communicates with the circulating steam inlet end of the plate heat exchanger 61 through the circulating steam pipeline 651 .

The plate heat exchanger 61 is further provided with a condensate water outlet end, and the condensate water outlet end is connected to a condensate water storage tank 68 through a condensate water pipe 66 , and a first valve 67 is provided on the condensate water pipe 66 .

A feed pump 6211 is provided on the feed pipe 621 .

Spiral guide vanes 69 are provided inside the first precipitation and crystallization tank 62 and the second precipitation and crystallization tank 63 .

Example 2

A process for applying the above-mentioned high brine concentration crystallization treatment system, comprising the steps:

1. Collect factory sewage into sewage collection tank 1, carry out oil and slag removal treatment through pre-treatment device 2, and then carry out impurity removal treatment through flocculation sedimentation device 3, ultrafiltration device 4, and reverse osmosis device 5;

2. The feed liquid after the impurity removal treatment in step 1 enters the plate heat exchanger 61 through the feed end of the plate heat exchanger 61 for heating and heating, and then flows into the first precipitation crystallization tank 62 and the second precipitation crystallization tank 63 in turn for precipitation and separation. , the separated feed liquid is pumped into the plate heat exchanger 61 through the feed liquid circulation pump 64 to be heated again for heating, and the circulation precipitation separation is carried out;

At the same time, the heated feed liquid is evaporated in the first precipitation crystallization tank 62 and the second precipitation crystallization tank 63, and the evaporated steam is compressed and processed by the steam compressor 65 and circulated to the plate heat exchanger 61 to provide thermal energy to the feed liquid;

After several cycles of precipitation and separation, the high brine is concentrated and crystallized at the bottom of the first precipitation crystallization tank 62 and the second precipitation crystallization tank 63 to obtain mixed salt crystals.

Preferably, in the step 2, the feed liquid is heated to 85-100°C in the plate heat exchanger 61 and then enters the first precipitation and crystallization tank 62 and the second precipitation and crystallization tank 63 for cyclic precipitation and separation; The heating temperature is 85°C, 90°C, 95°C or 100°C.

The above-mentioned embodiment is a preferred implementation scheme of the present invention. In addition, the present invention can also be implemented in other ways, and any obvious replacements are within the protection scope of the present invention without departing from the concept of the present invention.

Claims (6)

1. The utility model provides a concentrated crystallization processing system of high salt water which characterized in that: the device comprises a sewage collecting tank (1), a pretreatment device (2), a flocculation and precipitation device (3), an ultrafiltration device (4), a reverse osmosis device (5) and an MVR evaporation and concentration device (6) in turn according to the treatment use sequence, wherein the MVR evaporation and concentration device (6) comprises a plate heat exchanger (61), a first precipitation and crystallization tank (62), a second precipitation and crystallization tank (63) and a feed liquid circulating pump (64) in turn according to the treatment use sequence, and the steam outlet end of the first precipitation and crystallization tank (62) and the steam outlet end of the second precipitation and crystallization tank (63) are communicated with the plate heat exchanger (61) through a steam compressor (65); the plate heat exchanger (61) is provided with a feed end, and the feed end of the plate heat exchanger (61) is communicated with the output end of the reverse osmosis device (5) through a feed pipeline (611);

spiral guide vanes (69) are arranged in the first precipitation crystallizing tank (62) and the second precipitation crystallizing tank (63);

the plate heat exchanger (61) is also provided with a circulating feed liquid inlet end and a circulating feed liquid outlet end, the middle upper part of the first precipitation crystallizing tank (62) is provided with a first feed end and a first feed liquid outlet end, and the middle upper part of the second precipitation crystallizing tank (63) is provided with a second feed end and a second feed liquid outlet end;

the circulation feed liquid entrance point of plate heat exchanger (61) pass through feed pipeline (621) with the first feed end intercommunication of first precipitation crystallizer (62), the second feed end of second precipitation crystallizer (63) pass through connecting tube (622) with the first feed liquid exit end intercommunication of first precipitation crystallizer (62), the second feed liquid exit end of second precipitation crystallizer (63) pass through first circulation pipeline (631) with the entrance point intercommunication of feed liquid circulating pump (64), the exit end of feed liquid circulating pump (64) pass through second circulation pipeline (641) with the circulation feed liquid entrance point intercommunication of plate heat exchanger (61).

2. The high salinity water concentration crystallization processing system of claim 1, characterized in that: the plate heat exchanger (61) is also provided with a circulating steam inlet end, the upper part of the first precipitation crystallizing tank (62) is provided with a first steam outlet end, and the upper part of the second precipitation crystallizing tank (63) is provided with a second steam outlet end;

the first steam outlet end of the first precipitation crystallization tank (62) is communicated with the inlet end of the steam compressor (65) through a first steam pipeline (623), the second steam outlet end of the second precipitation crystallization tank (63) is communicated with the inlet end of the steam compressor (65) through a second steam pipeline (632), and the outlet end of the steam compressor (65) is communicated with the circulating steam inlet end of the plate-type heat exchanger (61) through a circulating steam pipeline (651).

3. The high salinity water concentration crystallization processing system of claim 1, characterized in that: the plate heat exchanger (61) is further provided with a condensed water outlet end, the condensed water outlet end is connected with a condensed water storage tank (68) through a condensed water pipeline (66), and a first valve (67) is arranged on the condensed water pipeline (66).

4. The high salinity water concentration crystallization processing system of claim 1, characterized in that: and a feeding pump is arranged on the feeding pipeline (621).

5. A treatment process using the high-salinity water concentration and crystallization treatment system as defined in any one of claims 1 to 4, wherein: the method comprises the following steps:

(1) collecting factory sewage into a sewage collecting tank (1), performing oil and slag removal treatment by a pretreatment device (2), and then performing impurity removal treatment by a flocculation precipitation device (3), an ultrafiltration device (4) and a reverse osmosis device (5);

(2) feeding the feed liquid subjected to impurity removal treatment in the step (1) into a plate heat exchanger (61) through a feed end of the plate heat exchanger (61) for heating, then sequentially flowing into a first precipitation crystallizing tank (62) and a second precipitation crystallizing tank (63) for precipitation separation, pumping the separated feed liquid into the plate heat exchanger (61) through a feed liquid circulating pump (64) for heating again, and performing circulating precipitation separation;

meanwhile, the feed liquid heated by temperature rise is evaporated in a first precipitation crystallizing tank (62) and a second precipitation crystallizing tank (63), and the evaporated steam is compressed by a steam compressor (65) and then circulated to a plate heat exchanger (61) to provide heat energy for the feed liquid;

after multiple circulating precipitation separation, the high-salinity water is concentrated and crystallized at the bottoms of a first precipitation crystallizing tank (62) and a second precipitation crystallizing tank (63) to obtain mixed salt crystals.

6. The process of claim 5, wherein: in the step (2), the feed liquid is heated to 85-100 ℃ in a plate heat exchanger (61) and then enters a first precipitation crystallization tank (62) and a second precipitation crystallization tank (63) for cyclic precipitation separation.

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