CN110357334A - Coal water slurry gasification waste water divides salt crystallization zero-discharge treatment system and method - Google Patents

Abstract

The invention discloses a zero-discharge treatment system and method for coal-water slurry gasification wastewater salt separation and crystallization. The system includes a pretreatment system, a salt separation system, a mirabilite crystallization system and a salt crystallization system; the method includes S1. pretreatment, S2 . Salt division, S3. Output of sodium chloride, S4. Output of sodium sulfate and S5. Treatment of mother liquor. The advantage of the present invention is that, on the basis of meeting the system operation requirements, the traditional coal-water slurry gasification wastewater is treated with a high-salt wastewater treatment system, and chemical softening, filtration, and membrane systems are repeatedly set up, reducing system investment and construction costs, reducing The energy consumption of the pretreatment system is reduced; the salt separation system is optimized, and the reverse osmosis water is mixed with the concentrated water of the primary nanofiltration in proportion to the secondary nanofiltration, which reduces the operating pressure of the secondary nanofiltration and improves the secondary nanofiltration. The recovery rate of filtration prolongs the service life of the equipment; the crystallization system is optimized to improve the recovery rate and purity of sodium chloride and sodium sulfate.

Description

Coal-water slurry gasification wastewater treatment system and method for salt separation and crystallization zero discharge

Technical field:

The invention relates to the field of coal gasification, in particular to a zero-discharge treatment system and method for coal-water slurry gasification waste water, salt separation and crystallization.

Background technique:

Coal-water slurry gasification technology is a coal gasification technology that uses coal-water slurry as the raw material for coal gasification. Due to the high reaction temperature and pressure of coal-water slurry gasification technology, the effective components in the coal-water slurry can be recovered in the gasifier. Complete conversion is achieved, and the organic matter, pollutants and solid impurities carried in the coal-water slurry and produced during the gasification process enter into the coal-water slurry gasification wastewater, and the coal-water slurry gasification wastewater can be recycled after being reused. The highest recovery rate is 80%; while the other 20% coal-water slurry gasification wastewater not only has high salt content, but also has complex pollutant components, with many types of organic pollutants, high concentrations and most of them are highly toxic. It belongs to medium and high concentration organic wastewater that is difficult to biodegrade.

At present, for this part of coal-water slurry gasification wastewater, the following methods are generally used for treatment: 1. Directly send to the sewage treatment plant for treatment. Large-scale wastewater has seriously affected the development of the coal chemical industry; 2. Direct evaporation and drying, after evaporation and drying of coal-water slurry gasification wastewater, miscellaneous salts are produced. Miscellaneous salts are not only complex in composition, but also easy to dissolve, and pollutants will easily leak when stacked for a long time Accidents, serious environmental pollution, do not meet current environmental protection requirements; 3, utilize high-salt wastewater treatment system to carry out coal-water slurry gasification wastewater treatment, as shown in Figure 1, there are the following problems: 1) the coal-water slurry gasification wastewater is sequentially For reclaimed water reuse treatment, concentrated treatment and salt separation treatment, the reclaimed water reuse treatment system is generally equipped with chemical softening, filtration, and membrane systems, and the concentrated treatment system is generally equipped with chemical softening, filtration, membrane systems, and ion exchange softening. The construction of a salt separation treatment system on the basis of the concentration treatment system also needs to be equipped with chemical softening, filtration, advanced oxidation, salt separation, and evaporation crystallization; it can be seen that using a high-salt wastewater treatment system to treat coal-water slurry gasification wastewater requires repeated settings. Chemical softening, filtration, and membrane systems lead to high construction costs and high energy consumption of existing high-salt wastewater treatment systems; The first stage nanofiltration, the concentrated water of the first stage nanofiltration is followed by the second stage nanofiltration. Separation treatment, the concentrated water of the secondary nanofiltration is subjected to advanced oxidation to remove organic matter, and then thenardite is separated, and thenardite is recovered from the salt evaporation separation mother liquor to improve the recovery rate of thenardite, but no attention is paid to the purity of the by-product sodium sulfate crystal salt, various evaporation and The problem of salt recovery in frozen mother liquor leads to low purity of by-product sodium sulfate crystalline salt, high TOC, and high output of miscellaneous salt. The increase in miscellaneous salt production will inevitably lead to high cost of miscellaneous salt treatment and increase the burden on coal chemical enterprises.

Invention content:

The first object of the present invention is to provide a zero-emission treatment system for coal-water slurry gasification wastewater salt separation and crystallization with low investment and construction costs, low yield of miscellaneous salts, and high purity of by-product crystal salts.

The second object of the present invention is to provide a zero-discharge treatment method for salt separation and crystallization of coal-water slurry gasification wastewater with low miscellaneous salt yield and high purity of by-product crystalline salt.

The first object of the present invention is implemented by the following technical solutions: coal water slurry gasification wastewater salt separation crystallization zero discharge treatment system, which includes a pretreatment system, a salt separation system, a Glauber's salt crystallization system and a salt crystallization system, and the pretreatment system The water outlet of the ion exchange equipment is connected to the water inlet of the primary reverse osmosis system of the salt separation system, and the concentrated water outlet of the secondary nanofiltration system of the salt separation system is connected to the thenardite multi-effect evaporation of the thenardite crystallization system The water inlet of the crystallizer is connected, the concentrated water outlet of the three-stage reverse osmosis system of the salt separation system is connected with the inlet of the salt multi-effect evaporation crystallizer of the salt crystallization system, and the mother liquor outlet of the mirabilite multi-effect evaporation crystallizer is , the mother liquor outlet of the salt multi-effect evaporation crystallizer is connected with the inlet of the mother liquor freezing crystallizer respectively, the slurry outlet of the mother liquor freezing crystallizer is connected with the inlet of the separatory centrifuge, and the solid matter of the separatory centrifuge The outlet is connected with the material inlet of the Glauber's salt dissolving tank of the Glauber's salt crystallization system; the mother liquor outlet of the mother liquor frozen crystallizer is connected with the inlet of the first mother liquor evaporator of the salt crystallization system, and the slurry of the first mother liquor evaporator The feed outlet is connected to the inlet of the mother liquor centrifuge, the solid outlet of the mother liquor centrifuge is connected to the inlet of the salt multi-effect evaporation crystallizer, the mother liquor outlet of the first mother liquor evaporator is connected to the inlet of the miscellaneous salt dryer connect.

Further, the pretreatment system includes chemical softening equipment, filtering equipment and the ion exchange equipment, the water inlet of the chemical softening equipment is connected to the coal-water slurry gasification wastewater pipeline, and the water outlet of the chemical softening equipment is connected to the The water inlet of the filter equipment is connected, and the water outlet of the filter equipment is connected with the water inlet of the ion exchange equipment; the chemical softening equipment is equipped with a mud scraper, and the mud discharge port of the chemical softening equipment is connected to the pressure filter The feeding port of the machine is connected.

Further, the filtering equipment includes a V-shaped filter tank and an ultrafiltration equipment, and the water outlet of the V-shaped filter tank is connected to the water inlet of the ultrafiltration equipment.

Further, the salt separation system includes the primary reverse osmosis system, reuse water tank, decarburizer, secondary reverse osmosis system, advanced oxidation system, primary nanofiltration system, the secondary nanofiltration system, nanofiltration Filtration production water tank, the three-stage reverse osmosis system and the four-stage reverse osmosis system, the water production outlet of the first-stage reverse osmosis system is connected to the water inlet of the reuse water tank, the concentrated water of the first-stage reverse osmosis system The outlet is connected to the water inlet of the decarburizer, and the water outlet of the decarburizer is connected to the water inlet of the two-stage reverse osmosis system; The water inlet of the secondary reverse osmosis system is connected to the water inlet of the advanced oxidation system; the water outlet of the advanced oxidation system is connected to the water inlet of the primary nanofiltration system, and the The water outlet of the primary nanofiltration system is connected to the water inlet of the nanofiltration water production tank, the concentrated water outlet of the primary nanofiltration system is connected to the water inlet of the secondary nanofiltration system, and the secondary nanofiltration system is connected to the water inlet of the secondary nanofiltration system. The water inlet of the filtration system is also connected with the water outlet of the reuse water tank through a regulating valve; the water production outlet of the secondary nanofiltration system is connected with the water inlet of the nanofiltration water production tank; The water outlet is connected to the water inlet of the three-stage reverse osmosis system, and the produced water outlet of the three-stage reverse osmosis system is connected to the water inlet of the four-stage reverse osmosis system; the produced water outlet of the four-stage reverse osmosis system It is connected to the water inlet of the reuse water pool, and the concentrated water outlet of the four-stage reverse osmosis system is connected to the water inlet of the nanofiltration water pool; the three-stage reverse osmosis system is a disc-type reverse osmosis system, electric Any one of a membrane system or a roll-type reverse osmosis system, and the four-stage reverse osmosis system is any one of a disk-type reverse osmosis system or a roll-type reverse osmosis system.

Further, the Glauber’s salt crystallization system includes the Glauber’s salt multi-effect evaporation crystallizer, the Glauber’s salt dissolving tank, Glauber’s salt recrystallization evaporator, Glauber’s salt centrifuge and Glauber’s salt dryer, and the slurry outlet of the Glauber’s salt multi-effect evaporation crystallizer It is connected with the inlet of the liquid separator centrifuge, the material outlet of the Glauber's salt dissolving tank is connected with the material inlet of the Glauber's salt recrystallization evaporator, and the material outlet of the Glauber's salt recrystallization evaporator is connected with the material of the Glauber's salt centrifuge. The inlet is connected, the solids outlet of the Glauber's salt centrifuge is connected with the inlet of the Glauber's salt dryer, and the outlet of the Glauber's salt dryer is connected with the inlet of the sodium sulfate storage bin.

Further, the salt crystallization system includes the salt multi-effect evaporation crystallizer, a salt centrifuge, and a salt dryer, the solids outlet is connected to the material inlet of the salt centrifuge, and the solids of the salt centrifuge The material outlet is connected with the feed port of the salt drier, and the discharge port of the salt drier is connected with the inlet of the sodium chloride storage bin.

Further, it also includes a second mother liquor evaporator, the mother liquor outlet of the first mother liquor evaporator is connected to the inlet of the second mother liquor evaporator, the slurry outlet of the second mother liquor evaporator is connected to the miscellaneous Inlet connection for salt dryer.

The second object of the present invention is implemented by the following technical solutions: a zero-discharge treatment method for coal-water slurry gasification wastewater salt separation crystallization, which includes the following steps:

S1. Pretreatment: After the coal-water slurry gasification wastewater is homogeneous and equalized in the adjustment tank, it enters the pretreatment system for hard and turbidity removal, silicon removal, pH adjustment, and organic matter removal to obtain pretreated wastewater. The indicators of wastewater are Ca ²⁺ = 0mg/l, Mg ²⁺ = 0mg/l, SiO ₂ ≤15.00mg/l, turbidity ≤1NTU, pH 7-8;

S2. Salt separation: the pretreated wastewater is transported to the primary reverse osmosis system for concentration to obtain primary concentrated water; after the primary concentrated water is adjusted to pH 4-5, it is transported to the decarbonizer to remove carbon dioxide to obtain decarburization effluent; the decarbonized effluent is transported to the secondary reverse osmosis system for concentration to obtain secondary concentrated water; the secondary concentrated water is transported to the advanced oxidation system for removal of organic matter to obtain oxidized wastewater; the primary reverse osmosis system 1. The produced water of the secondary reverse osmosis system is transported to the reuse water tank as reuse water; the oxidized wastewater is transported to the primary nanofiltration system for a salt separation treatment to obtain a primary nanofiltration concentrated water; the primary nanofiltration The filtered concentrated water and the reused water are transported to the secondary nanofiltration system according to the volume ratio of 4:3-4 for secondary salt separation treatment to obtain the secondary nanofiltration concentrated water; the primary nanofiltration water, the The secondary nanofiltration produced water is transported to the nanofiltration production pool as waste water to be brine; the waste water to be produced is transported to a three-stage reverse osmosis system for concentration to obtain tertiary concentrated water and tertiary produced water; The produced water is transported to the four-stage reverse osmosis system for treatment, and the four produced water is transported to the reuse water tank, and the four concentrated water is transported to the nanofiltration produced water tank, and the four produced water is transported to the reuse pool;

S3. Output of sodium chloride: the three times concentrated water is transported to a salt multi-effect evaporation crystallizer for evaporation and crystallization to obtain salt slurry and salt mother liquor; the salt slurry is transported to a salt centrifuge for solid-liquid separation, Obtaining solid sodium chloride; the solid sodium chloride is transported to a salt dryer and dried to a water content of ≤0.1%, to obtain sodium chloride crystalline salt, the purity of the sodium chloride crystalline salt is ≥98.5%;

S4. Output of sodium sulfate: the secondary nanofiltration concentrated water is transported to the Glauber's salt multi-effect evaporation crystallizer for evaporation and crystallization to obtain Glauber's salt slurry and Glauber's salt mother liquor; the Glauber's salt slurry is subjected to solid-liquid separation to obtain sodium sulfate solid The sodium sulfate solid is transported to the Glauber's salt dissolving tank for redissolving, and the solution in the Glauber's salt dissolving tank is a sodium sulfate saturated solution to obtain a heavy solution; the heavy solution is transported to the Glauber's salt recrystallization evaporator to obtain a recrystallization slurry material; the recrystallized slurry is transported to the Glauber's salt centrifuge for solid-liquid separation to obtain sodium sulfate solid; the sodium sulfate solid is transported to the Glauber's salt dryer to dry to a water content of ≤0.3%, to obtain sodium sulfate crystalline salt, the The TOC of sodium sulfate crystalline salt is ≤50mg/KG, and the purity is ≥97%;

S5. Treatment of mother liquor: both the salt mother liquor and the Glauber's salt mother liquor are transported to the mother liquor freezing crystallizer for freezing and crystallization, the COD of the salt mother liquor is ≤18000mg/L, SiO ₂ ≤4000mg/l, and the Glauber's salt mother liquor is COD ≤ 30000mg/L, SiO ₂ ≤ 5000mg/l, to obtain mother liquor slurry and frozen mother liquor; after the mother liquor slurry is subjected to solid-liquid separation treatment, sodium sulfate decahydrate solid is obtained, and the sodium sulfate decahydrate solid is transported to the In the output of S4. sodium sulfate, the Glauber's salt is redissolved in the dissolving tank; the frozen mother liquor is transported to the first mother liquor evaporator for salt separation to obtain mixed salt slurry and concentrated mother liquor; the mixed salt slurry After solid-liquid separation, the dehydrated mixed salt is obtained, and the dehydrated mixed salt is transported to the salt multi-effect evaporation crystallizer in the output of the S3.sodium chloride; the concentrated mother liquor is transported to the miscellaneous salt dryer Internal drying, to get miscellaneous salts.

Further, the S1. pretreatment is specifically as follows:

a1. Chemical softening: the coal-water slurry gasification wastewater is transported to chemical softening equipment for treatment of hardening and turbidity removal, silicon removal, and organic matter removal to obtain chemically softened water. The index of the chemically softened water is Ca ²⁺ ≤50.00 mg/l, Mg ²⁺ ≤50.00mg/l, SiO ₂ ≤15.00mg/l, turbidity ≤20NTU; the obtained sludge is sent to the filter press for dehydration to obtain dewatered sludge;

a2. Filtration: the chemically softened water is adjusted to a pH of 7-8, and then transported to a filtration system for turbidity reduction to obtain filtered water, and the turbidity of the filtered water is ≤ 1 NTU;

a3. Deep softening: the filtered water is sent to the ion exchange equipment for deep softening, and then to the pretreated wastewater.

Further, in the treatment of the S5. mother liquor, the concentrated mother liquor is first transported to the second mother liquor evaporator for concentration to obtain the second concentrated mother liquor, and the SiO ₂ of the concentrated mother liquor is ≤8000mg/l, and then the two The subconcentrated mother liquor is transported to the miscellaneous salt drier for drying to obtain the miscellaneous salt.

Advantages of the present invention: 1. On the basis of meeting the system operation requirements, the traditional coal-water slurry gasification wastewater is treated with a high-salt wastewater treatment system, and chemical softening, filtration, and membrane systems are repeatedly set up, which reduces the cost of system investment and construction. The energy consumption of the pretreatment system is reduced. 2. The salt separation system is optimized. Firstly, the reverse osmosis system is used to concentrate and the advanced oxidation system is used to remove organic matter, so that the water entering the nanofiltration system meets the requirements of nanofiltration water intake; Proportional mixing is followed by secondary nanofiltration, which reduces the operating pressure of the secondary nanofiltration, improves the recovery rate of the secondary nanofiltration, and prolongs the service life of the equipment. 3. The crystallization system is optimized. The concentrated water produced by the second-stage nanofiltration is treated with Glauber's salt crystallization, and the product water produced by the second-stage nanofiltration is concentrated by reverse osmosis and then subjected to salt crystallization. First, in the process of Glauber's salt crystallization, the The sodium sulfate produced by Glauber's salt multi-effect evaporation crystallizer is redissolved and recrystallized, and the sodium sulfate crystal salt is obtained through evaporation and crystallization again, which improves the purity of sodium sulfate crystal salt; secondly, the mother liquor produced by the freezing crystallizer is further evaporated Crystallization, the obtained solids are returned to the salt multi-effect evaporation crystallizer for recrystallization, the sodium chloride in the mother liquor is recovered, and the recovery rate and purity of the sodium chloride crystal salt are improved; thirdly, for the salt multi-effect evaporation crystallizer , Glauber’s salt, and the mother liquor produced by the multi-effect evaporation crystallizer are all transported to the freezing crystallizer for freezing and crystallization, and the obtained sodium sulfate decahydrate is transported to the re-dissolving step of the sodium sulfate crystallization process for re-dissolving and recrystallization, increasing the sodium sulfate recovery and purity.

Description of drawings:

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Figure 1 is a schematic diagram of the connection of a conventional wastewater zero discharge system.

FIG. 2 is a schematic diagram of the overall connection of Embodiment 1.

Fig. 3 is a flowchart of a zero-discharge treatment method for coal-water slurry gasification wastewater by salt separation and crystallization.

Chemical softening equipment 1, V-type filter 2, ultrafiltration equipment 3, ion exchange equipment 4, primary reverse osmosis system 5, decarburizer 6, reuse pool 7, secondary reverse osmosis system 8, advanced oxidation system 9, Primary nanofiltration system 10, secondary nanofiltration system 11, nanofiltration production pool 12, third-stage reverse osmosis system 13, fourth-stage reverse osmosis system 14, thenardite multi-effect evaporation crystallizer 15, thenardite dissolution tank 16, thenardite recrystallization Evaporator 17, Glauber's salt centrifuge 18, Glauber's salt dryer 19, separatory centrifuge 20, salt multi-effect evaporation crystallizer 21, salt centrifuge 22, salt dryer 23, mother liquor freezing crystallizer 24, first mother liquor evaporator 25 , the second mother liquor evaporator 26, miscellaneous salt drier 27, filter press 28, regulating valve 29, mother liquor centrifuge 30.

Detailed ways:

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Example 1:

As shown in Figure 2, the coal water slurry gasification wastewater salt separation and crystallization zero discharge treatment system includes a pretreatment system, a salt separation system, a Glauber’s salt crystallization system and a salt crystallization system;

The pretreatment system can remove most of the total hardness, total alkalinity, heavy metal ions and suspended solids as well as some silica, fluoride ions and organic matter in the wastewater to ensure the normal and stable operation of the subsequent system; the pretreatment system includes chemical softening equipment 1 , filter equipment and ion exchange equipment 4, the water inlet of the chemical softening equipment 1 is connected with the coal water slurry gasification wastewater pipeline, the water outlet of the chemical softening equipment 1 is connected with the water inlet of the filter equipment, and the filter equipment includes a V-shaped filter tank 2 and Ultrafiltration equipment 3, the water outlet of V-type filter tank 2 is connected with the water inlet of ultrafiltration equipment 3, the water outlet of filtration equipment is connected with the water inlet of ion exchange equipment 4; chemical softening equipment 1 is provided with scraper, chemical The sludge discharge port of the softening device 1 is connected with the feed port of the filter press 28 .

The water outlet of the ion exchange equipment 4 of the pretreatment system is connected to the water inlet of the first-stage reverse osmosis system 5 of the salt separation system. Reverse osmosis system 8, advanced oxidation system 9, primary nanofiltration system 10, secondary nanofiltration system 11, nanofiltration production pool 12, third-stage reverse osmosis system 13 and fourth-stage reverse osmosis system 14, three-stage reverse osmosis system 13 It is any one of disc-type reverse osmosis system, electrically driven membrane system or roll-type reverse osmosis system. In this embodiment, the three-stage reverse osmosis is a disc-type reverse osmosis system; Any one of the tubular reverse osmosis system or the coiled reverse osmosis system. In this embodiment, the four-stage reverse osmosis is a coiled reverse osmosis system; The water inlet is connected, the concentrated water outlet of the primary reverse osmosis system 5 is connected to the water inlet of the decarburizer 6, the water outlet of the decarburizer 6 is connected to the water inlet of the secondary reverse osmosis system 8; the secondary reverse osmosis system 8 The outlet of the produced water is connected to the water inlet of the reuse pool 7, the concentrated water outlet of the secondary reverse osmosis system 8 is connected to the water inlet of the advanced oxidation system 9; the water outlet of the advanced oxidation system 9 is connected to the water inlet of the primary nanofiltration system 10 Connection, the water outlet of the primary nanofiltration system 10 is connected to the water inlet of the nanofiltration water production pool 12, the concentrated water outlet of the primary nanofiltration system 10 is connected to the water inlet of the secondary nanofiltration system 11, and the secondary nanofiltration system The water inlet of 11 is also connected with the water outlet of reuse water tank 7 through regulating valve 29; The water inlet of the three-stage reverse osmosis system 13 is connected, and the water outlet of the three-stage reverse osmosis system 13 is connected with the water inlet of the four-stage reverse osmosis system 14; Connect, the concentrated water outlet of the four-stage reverse osmosis system 14 is connected with the water inlet of the nanofiltration pool.

The concentrated water outlet of the secondary nanofiltration system 11 of the salt separation system is connected to the water inlet of the thenardite multi-effect evaporation crystallizer 15 of the thenardite crystallization system. Crystallization evaporator 17, Glauber's salt centrifuge 18 and Glauber's salt dryer 19, Glauber's salt recrystallization evaporator 17 can be multi-effect evaporation crystallizer or the Glauber's salt recrystallization evaporator disclosed in Chinese patent with application number CN201720046981.2, in this embodiment , Glauber's salt recrystallization evaporator 17 may be a multi-effect evaporation crystallizer. The slurry outlet of Glauber's salt multi-effect evaporation crystallizer 15 is connected with the inlet of separatory centrifuge 20, the material outlet of Glauber's salt dissolving tank 16 is connected with the material inlet of Glauber's salt recrystallization evaporator 17, and the material outlet of Glauber's salt recrystallization evaporator 17 is connected with The material inlet of the Glauber's salt centrifuge 18 is connected, the solid matter outlet of the Glauber's salt centrifuge 18 is connected with the inlet of the Glauber's salt dryer 19, and the outlet of the Glauber's salt dryer 19 is connected with the inlet of the sodium sulfate storage bin.

The concentrated water outlet of the three-stage reverse osmosis system 13 of the salt separation system is connected to the inlet of the salt multi-effect evaporation crystallizer 21 of the salt crystallization system. The salt crystallization system includes a salt multi-effect evaporation crystallizer 21, a salt centrifuge 22, and a salt dryer. 23, the solids outlet of the salt centrifuge 22 is connected to the material inlet, the solids outlet of the salt centrifuge 22 is connected to the feed port of the salt dryer 23, and the outlet of the salt dryer 23 is connected to the sodium chloride storage bin. import connection.

The mother liquor outlet of Glauber's salt multi-effect evaporation crystallizer 15 and the mother liquor outlet of salt multi-effect evaporation crystallizer 21 are respectively connected to the inlet of mother liquor freezing crystallizer 24, and the slurry outlet of mother liquor freezing crystallizer 24 is connected to the inlet of separatory centrifuge 20 , the solids outlet of the separatory centrifuge 20 is connected with the material inlet of the Glauber's salt dissolving tank 16 of the Glauber's salt crystallization system; The slurry outlet of the evaporator 25 is connected with the inlet of the mother liquor centrifuge 30, the solid outlet of the mother liquor centrifuge 30 is connected with the inlet of the salt multi-effect evaporation crystallizer 21, the mother liquor outlet of the first mother liquor evaporator 25 is connected with the second mother liquor evaporator The inlet of 26 is connected, and the slurry outlet of the second mother liquor evaporator 26 is connected with the inlet of miscellaneous salt drier 27.

Compared with the conventional waste water zero discharge system (as shown in Figure 1), the difference between Embodiment 1 is that the repeated setting of the V-shaped filter tank 2 and the ultrafiltration equipment 3 is omitted, and the subsequent two-stage softening and hardening removal is omitted. For equipment, calculated according to the current market price, the investment and construction cost of this embodiment is 25 million yuan/set lower than that of the conventional wastewater zero discharge system, and the equipment maintenance and replacement costs can be reduced by 450,000 yuan per year.

Example 2:

Utilize embodiment 1 to carry out the coal-water slurry gasification wastewater salt separation crystallization zero-discharge treatment method, as shown in Figure 3, it comprises the following steps:

S1. Pretreatment: After the coal-water slurry gasification wastewater is homogeneous and equalized in the adjustment tank, it enters the pretreatment system for hard and turbidity removal, silicon removal, pH adjustment, and organic matter removal. The details are as follows:

a1. Chemical softening: Coal-water slurry gasification wastewater is sent to chemical softening equipment 1 for treatment of hardening, turbidity, silicon, and organic matter removal to obtain chemically softened water. The index of chemically softened water is Ca ²⁺ ≤50.00mg/l , Mg ²⁺ ≤50.00mg/l, SiO ₂ ≤15.00mg/l, turbidity ≤20NTU; the obtained sludge is transported to filter press 28 for dehydration to obtain dewatered sludge;

a2. Filtration: chemically softened water is adjusted to pH 7 and then transported to the filtration system for turbidity reduction to obtain filtered water, the turbidity of which is ≤1NTU;

a3. Deep softening: the filtered water is transported to the ion exchange equipment 4 for deep softening, and then to pre-treatment wastewater;

Obtain pretreated wastewater, the indicators of pretreated wastewater are Ca ²⁺ =0mg/l, Mg ²⁺ =0mg/l, SiO2≤15.00mg/l, turbidity≤1NTU, pH 7;

S2. Salt separation: the pretreated wastewater is transported to the primary reverse osmosis system 5 for concentration to obtain primary concentrated water; after the primary concentrated water is adjusted to pH 4, it is transported to the decarbonizer 6 to remove carbon dioxide to obtain decarbonized effluent; decarbonization The effluent is transported to the secondary reverse osmosis system 8 for concentration to obtain secondary concentrated water; the secondary concentrated water is transported to the advanced oxidation system 9 to remove organic matter to obtain oxidized wastewater; the primary reverse osmosis system 5 and the secondary reverse osmosis system 8 The produced water is transported to the reuse water pool 7 as reuse water; the oxidized waste water is transported to the primary nanofiltration system 10 for a salt separation treatment to obtain the primary nanofiltration concentrated water; the primary nanofiltration concentrated water and the recycled water are based on the volume ratio The ratio of 4:3 is sent to the secondary nanofiltration system 11 for secondary salt separation treatment to obtain the secondary nanofiltration concentrated water; the primary nanofiltration water and the secondary nanofiltration water are both sent to the nanofiltration water production pool 12 , as the waste water to be brine; the waste water to be brine is transported to the three-stage reverse osmosis system 13 for concentration to obtain the third concentrated water and the third product water; the third product water is sent to the four-stage reverse osmosis system 14 for treatment to obtain the fourth product water Transported to the reuse water pool 7, the obtained concentrated water is transported to the nanofiltration water production pool 12 for four times, and the four produced water is transported to the reuse water pool 7;

S3. Output of sodium chloride: three times concentrated water is transported to salt multi-effect evaporation crystallizer 21 for evaporation and crystallization to obtain salt slurry and salt mother liquor; salt slurry is transported to salt centrifuge 22 for solid-liquid separation to obtain solid Sodium chloride: solid sodium chloride is transported to the salt dryer 23 and dried to a water content of 0.1%, to obtain sodium chloride crystalline salt, and the purity of sodium chloride crystalline salt is 98.5%;

S4. Output of sodium sulfate: the secondary nanofiltration concentrated water is transported to the Glauber's salt multi-effect evaporation crystallizer 15 for evaporation and crystallization to obtain Glauber's salt slurry and Glauber's salt mother liquor; the Glauber's salt slurry is subjected to solid-liquid separation to obtain sodium sulfate solid; The solid is transported to the Glauber's salt dissolving tank 16 for redissolving, and the solution in the Glauber's salt dissolving tank 16 is a saturated solution of sodium sulfate to obtain a heavy solution; the heavy solution is transported to the Glauber's salt recrystallization evaporator 17 to obtain a recrystallization slurry; the recrystallization slurry Transported to Glauber's salt centrifuge 18 for solid-liquid separation to obtain sodium sulfate solid; the sodium sulfate solid was transported to Glauber's salt dryer 19 to dry to a water content of 0.3%, to obtain sodium sulfate crystalline salt, and the TOC of sodium sulfate crystalline salt was 37mg/KG , the purity is 97%;

S5. Treatment of mother liquor: the salt mother liquor and Glauber's salt mother liquor are transported to the mother liquor freezing crystallizer 24 for freezing and crystallization, the COD of the salt mother liquor is ≤18000mg/L, SiO ₂ ≤4000mg/l, the COD of Glauber's salt mother liquor is ≤30000mg/L, SiO ₂ ≤5000mg/l, to obtain mother liquor slurry and frozen mother liquor; after solid-liquid separation of mother liquor slurry, sodium sulfate decahydrate solid is obtained, and the sodium sulfate decahydrate solid is transported to the Glauber's salt dissolving tank in the output of S4. Redissolve within 16; the frozen mother liquor is transported to the first mother liquor evaporator 25 for salt separation to obtain mixed salt slurry and concentrated mother liquor; after solid-liquid separation of the mixed salt slurry, dehydrated mixed salt is obtained, and the dehydrated mixed salt is transported to S3. Salt multi-effect evaporation crystallizer 21 in the output of sodium chloride; the concentrated mother liquor is first transported to the second mother liquor evaporator 26 for concentration to obtain the secondary concentrated mother liquor, and the SiO ₂ of the concentrated mother liquor is ≤8000mg/l, and then The secondary concentrated mother liquor is transported to the miscellaneous salt drier 27 for drying to obtain miscellaneous salts.

The waste water with the same water quality and water quantity in Example 2 is transported to the conventional waste water zero discharge system (as shown in Figure 1) for processing, and the secondary nanofiltration operating pressure, sodium chloride crystalline salt purity and output, sodium sulfate crystalline salt purity and The yield and miscellaneous salt rate were detected and compared, and the comparison results are shown in Table 1 below.

Table 1 Comparison results of two groups

It can be seen from Table 1 that, compared with the conventional wastewater zero discharge system, this embodiment uses reverse osmosis produced water and primary nanofiltration concentrated water to mix in proportion, which reduces the operating pressure of the secondary nanofiltration and improves the recovery of the secondary nanofiltration. rate, prolonging the service life of the equipment. In addition, in this embodiment, by optimizing the crystallization system, the purity and yield of by-product sodium chloride crystalline salt and sodium sulfate crystalline salt are improved, and the output of miscellaneous salt is reduced, which can reduce the cost of miscellaneous salt treatment.

Example 3:

Utilize embodiment 1 to carry out the coal-water slurry gasification wastewater salt separation crystallization zero-discharge treatment method, as shown in Figure 3, it comprises the following steps:

S1. Pretreatment: After the coal-water slurry gasification wastewater is homogeneous and equalized in the adjustment tank, it enters the pretreatment system for hard and turbidity removal, silicon removal, pH adjustment, and organic matter removal. The details are as follows:

a1. Chemical softening: Coal water slurry gasification wastewater is transported to chemical softening equipment 1 for treatment of hardening and turbidity removal, silicon removal, and organic matter removal to obtain chemically softened water. The index of chemically softened water is Ca ²⁺ ≤50.00mg/l , Mg ²⁺ ≤50.00mg/l, SiO ₂ ≤15.00mg/l, turbidity ≤20NTU; the obtained sludge is transported to filter press 28 for dehydration to obtain dewatered sludge;

a2. Filtration: Chemically softened water is adjusted to pH 7.5 and sent to the filtration system for turbidity reduction to obtain filtered water, the turbidity of which is ≤1NTU;

a3. Deep softening: the filtered water is transported to the ion exchange equipment 4 for deep softening, and then to pre-treatment wastewater;

Obtain pretreated wastewater, the indicators of pretreated wastewater are Ca ²⁺ =0mg/l, Mg ²⁺ =0mg/l, SiO2≤15.00mg/l, turbidity≤1NTU, pH 7.5;

S2. Salt separation: the pretreated wastewater is transported to the primary reverse osmosis system 5 for concentration to obtain primary concentrated water; after the primary concentrated water is adjusted to pH 4.5, it is transported to the decarbonizer 6 to remove carbon dioxide to obtain decarbonized effluent; decarbonization The effluent is transported to the secondary reverse osmosis system 8 for concentration to obtain secondary concentrated water; the secondary concentrated water is transported to the advanced oxidation system 9 to remove organic matter to obtain oxidized wastewater; the primary reverse osmosis system 5 and the secondary reverse osmosis system 8 The produced water is transported to the reuse water pool 7 as reuse water; the oxidized waste water is transported to the primary nanofiltration system 10 for a salt separation treatment to obtain the primary nanofiltration concentrated water; the primary nanofiltration concentrated water and the recycled water are based on the volume ratio The ratio of 4:3.5 is sent to the secondary nanofiltration system 11 for secondary salt separation treatment to obtain the secondary nanofiltration concentrated water; the primary nanofiltration product water and the secondary nanofiltration product water are both sent to the nanofiltration water production pool 12 , as the waste water to be brine; the waste water to be brine is transported to the three-stage reverse osmosis system 13 for concentration to obtain the third concentrated water and the third product water; the third product water is sent to the four-stage reverse osmosis system 14 for treatment to obtain the fourth product water Transported to the reuse water pool 7, the obtained concentrated water is transported to the nanofiltration water production pool 12 for four times, and the four produced water is transported to the reuse water pool 7;

S3. Output of sodium chloride: three times concentrated water is transported to salt multi-effect evaporation crystallizer 21 for evaporation and crystallization to obtain salt slurry and salt mother liquor; salt slurry is transported to salt centrifuge 22 for solid-liquid separation to obtain solid Sodium chloride; the solid sodium chloride is transported to the salt dryer 23 and dried to a water content of 0.08%, so as to obtain sodium chloride crystalline salt, and the purity of the sodium chloride crystalline salt is 98.9%;

S4. Output of sodium sulfate: the secondary nanofiltration concentrated water is transported to the Glauber's salt multi-effect evaporation crystallizer 15 for evaporation and crystallization to obtain Glauber's salt slurry and Glauber's salt mother liquor; the Glauber's salt slurry is subjected to solid-liquid separation to obtain sodium sulfate solid; The solid is transported to the Glauber's salt dissolving tank 16 for redissolving, and the solution in the Glauber's salt dissolving tank 16 is a saturated solution of sodium sulfate to obtain a heavy solution; the heavy solution is transported to the Glauber's salt recrystallization evaporator 17 to obtain a recrystallization slurry; the recrystallization slurry Transported to Glauber's salt centrifuge 18 for solid-liquid separation to obtain solid sodium sulfate; the sodium sulfate solid was transported to Glauber's salt dryer 19 to dry to a water content of 0.23%, to obtain sodium sulfate crystalline salt, and the TOC of sodium sulfate crystalline salt was 32mg/KG , the purity is 97.8%;

S5. Treatment of mother liquor: the salt mother liquor and Glauber's salt mother liquor are transported to the mother liquor freezing crystallizer 24 for freezing and crystallization, the COD of the salt mother liquor is ≤18000mg/L, SiO ₂ ≤4000mg/l, the COD of Glauber's salt mother liquor is ≤30000mg/L, SiO ₂ ≤5000mg/l, to obtain mother liquor slurry and frozen mother liquor; after solid-liquid separation of mother liquor slurry, sodium sulfate decahydrate solid is obtained, and the sodium sulfate decahydrate solid is transported to the Glauber's salt dissolving tank in the output of S4. Redissolve within 16; the frozen mother liquor is transported to the first mother liquor evaporator 25 for salt separation to obtain mixed salt slurry and concentrated mother liquor; after solid-liquid separation of the mixed salt slurry, dehydrated mixed salt is obtained, and the dehydrated mixed salt is transported to S3. Salt multi-effect evaporation crystallizer 21 in the output of sodium chloride; the concentrated mother liquor is first transported to the second mother liquor evaporator 26 for concentration to obtain the secondary concentrated mother liquor, and the SiO ₂ of the concentrated mother liquor is ≤8000mg/l, and then The secondary concentrated mother liquor is transported to the miscellaneous salt drier 27 for drying to obtain miscellaneous salts.

The waste water with the same water quality and water quantity in Example 3 is transported to the conventional waste water zero discharge system (as shown in Figure 1) for processing, and the secondary nanofiltration operating pressure, sodium chloride crystalline salt purity and output, sodium sulfate crystalline salt purity and The output and miscellaneous salt output are detected and compared, and the comparison results are shown in Table 2 below.

Table 2 Comparison results of two groups

It can be seen from Table 2 that, compared with the conventional wastewater zero discharge system, this embodiment uses reverse osmosis produced water and primary nanofiltration concentrated water to be mixed in proportion to reduce the operating pressure of the secondary nanofiltration and improve the recovery rate of the secondary nanofiltration , prolonging the service life of the equipment. In addition, in this embodiment, by optimizing the crystallization system, the purity and yield of by-product sodium chloride crystalline salt and sodium sulfate crystalline salt are improved, and the output of miscellaneous salt is reduced, which can reduce the cost of miscellaneous salt treatment.

Example 4:

Utilize embodiment 1 to carry out the coal-water slurry gasification wastewater salt separation crystallization zero-discharge treatment method, as shown in Figure 3, it comprises the following steps:

S1. Pretreatment: After the coal-water slurry gasification wastewater is homogeneous and equalized in the adjustment tank, it enters the pretreatment system for hard and turbidity removal, silicon removal, pH adjustment, and organic matter removal. The details are as follows:

a1. Chemical softening: Coal water slurry gasification wastewater is transported to chemical softening equipment 1 for treatment of hardening and turbidity removal, silicon removal, and organic matter removal to obtain chemically softened water. The index of chemically softened water is Ca ²⁺ ≤50.00mg/l , Mg ²⁺ ≤50.00mg/l, SiO ₂ ≤15.00mg/l, turbidity ≤20NTU; the obtained sludge is transported to filter press 28 for dehydration to obtain dewatered sludge;

a2. Filtration: chemically softened water is adjusted to pH 8, then transported to the filtration system for turbidity reduction, and filtered water is obtained, and the turbidity of the filtered water is ≤1NTU;

a3. Deep softening: the filtered water is transported to the ion exchange equipment 4 for deep softening, and then to pre-treatment wastewater;

Obtain pretreated wastewater, the indicators of pretreated wastewater are Ca ²⁺ =0mg/l, Mg ²⁺ =0mg/l, SiO2≤15.00mg/l, turbidity≤1NTU, pH 8;

S2. Salt separation: the pretreated wastewater is transported to the primary reverse osmosis system 5 for concentration to obtain primary concentrated water; after the primary concentrated water is adjusted to pH 5, it is transported to the decarbonizer 6 to remove carbon dioxide to obtain decarbonized effluent; decarbonization The effluent is transported to the secondary reverse osmosis system 8 for concentration to obtain secondary concentrated water; the secondary concentrated water is transported to the advanced oxidation system 9 to remove organic matter to obtain oxidized wastewater; the primary reverse osmosis system 5 and the secondary reverse osmosis system 8 The produced water is transported to the reuse water pool 7 as reuse water; the oxidized waste water is transported to the primary nanofiltration system 10 for a salt separation treatment to obtain the primary nanofiltration concentrated water; the primary nanofiltration concentrated water and the recycled water are based on the volume ratio The ratio of 4:4 is sent to the secondary nanofiltration system 11 for secondary salt separation treatment to obtain the secondary nanofiltration concentrated water; the primary nanofiltration water and the secondary nanofiltration water are both sent to the nanofiltration water production tank 12 , as the waste water to be brine; the waste water to be brine is transported to the three-stage reverse osmosis system 13 for concentration to obtain the third concentrated water and the third product water; the third product water is sent to the four-stage reverse osmosis system 14 for treatment to obtain the fourth product water Transported to the reuse water pool 7, the obtained concentrated water is transported to the nanofiltration water production pool 12 for four times, and the four produced water is transported to the reuse water pool 7;

S3. Output of sodium chloride: three times concentrated water is transported to salt multi-effect evaporation crystallizer 21 for evaporation and crystallization to obtain salt slurry and salt mother liquor; salt slurry is transported to salt centrifuge 22 for solid-liquid separation to obtain solid Sodium chloride: the solid sodium chloride is transported to the salt dryer 23 and dried until the water content is 0.05%, so as to obtain sodium chloride crystalline salt, and the purity of the sodium chloride crystalline salt is 99.2%;

S4. Output of sodium sulfate: the secondary nanofiltration concentrated water is transported to the Glauber's salt multi-effect evaporation crystallizer 15 for evaporation and crystallization to obtain Glauber's salt slurry and Glauber's salt mother liquor; the Glauber's salt slurry is subjected to solid-liquid separation to obtain sodium sulfate solid; The solid is transported to the Glauber's salt dissolving tank 16 for redissolving, and the solution in the Glauber's salt dissolving tank 16 is a saturated solution of sodium sulfate to obtain a heavy solution; the heavy solution is transported to the Glauber's salt recrystallization evaporator 17 to obtain a recrystallization slurry; the recrystallization slurry Transported to Glauber's salt centrifuge 18 for solid-liquid separation to obtain sodium sulfate solid; the sodium sulfate solid was transported to Glauber's salt dryer 19 to dry to a water content of 0.19%, to obtain sodium sulfate crystalline salt, and the TOC of sodium sulfate crystalline salt was 28mg/KG , the purity is 99.1%;

S5. Treatment of mother liquor: the salt mother liquor and Glauber's salt mother liquor are transported to the mother liquor freezing crystallizer 24 for freezing and crystallization, the COD of the salt mother liquor is ≤18000mg/L, SiO ₂ ≤4000mg/l, the COD of Glauber's salt mother liquor is ≤30000mg/L, SiO ₂ ≤5000mg/l, to obtain mother liquor slurry and frozen mother liquor; after solid-liquid separation of mother liquor slurry, sodium sulfate decahydrate solid is obtained, and the sodium sulfate decahydrate solid is transported to the Glauber's salt dissolving tank in the output of S4. Redissolve within 16; the frozen mother liquor is transported to the first mother liquor evaporator 25 for salt separation to obtain mixed salt slurry and concentrated mother liquor; after solid-liquid separation of the mixed salt slurry, dehydrated mixed salt is obtained, and the dehydrated mixed salt is transported to S3. Salt multi-effect evaporation crystallizer 21 in the output of sodium chloride; the concentrated mother liquor is first transported to the second mother liquor evaporator 26 for concentration to obtain the secondary concentrated mother liquor, and the SiO ₂ of the concentrated mother liquor is ≤8000mg/l, and then The secondary concentrated mother liquor is transported to the miscellaneous salt drier 27 for drying to obtain miscellaneous salts.

The waste water with the same water quality and quantity in Example 4 is transported to the conventional waste water zero discharge system (as shown in Figure 1) for processing, and the secondary nanofiltration operating pressure, sodium chloride crystalline salt purity and output, sodium sulfate crystalline salt purity and The output and miscellaneous salt output are detected and compared, and the comparison results are shown in Table 3 below.

Table 3 Comparison results of two groups

It can be seen from Table 3 that, compared with the conventional wastewater zero discharge system, this embodiment uses reverse osmosis produced water and primary nanofiltration concentrated water to mix in proportion, which reduces the operating pressure of the secondary nanofiltration and improves the recovery of the secondary nanofiltration. rate, prolonging the service life of the equipment. In addition, in this embodiment, by optimizing the crystallization system, the purity and yield of by-product sodium chloride crystalline salt and sodium sulfate crystalline salt are improved, and the output of miscellaneous salt is reduced, which can reduce the cost of miscellaneous salt treatment.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims (10)

1. coal water slurry gasification waste water divides salt to crystallize zero-discharge treatment system, which is characterized in that it includes pretreatment system, divides salt system System, sodium chloride crystal system and salt crystal system, the water outlet of the ion-exchange unit of the pretreatment system divide salt system with described The water inlet of the primary reverse osmosis system of system connects, concentrated water outlet and the saltcake of the second level nanofiltration system for dividing salt system The water inlet of the saltcake Multi-effect evaporation crystallizer of crystal system connects, and the concentrated water of the three-level counter-infiltration system of described point of salt system goes out Mouth is connect with the import of the salt Multi-effect evaporation crystallizer of the salt crystal system, and the mother liquor of the saltcake Multi-effect evaporation crystallizer goes out Mouthful, the mother liquor outlet of the salt Multi-effect evaporation crystallizer connect respectively with the import of mother liquor freezing and crystallizing device, the mother liquor freezes The slurry outlet of crystallizer is connect with the import of liquid separation centrifuge, solids outlet and the saltcake knot of the liquid separation centrifuge The material inlet connection of the saltcake dissolving tank of crystallographic system system；The mother liquor outlet of the mother liquor freezing and crystallizing device and the salt crystal system The first mother liquid evaporation device import connection, the import of the slurry outlet of the first mother liquid evaporation device and mother liquor centrifuge connects It connects, the solid outlet of the mother liquor centrifuge is connect with the import of the salt Multi-effect evaporation crystallizer, first mother liquid evaporation The mother liquor outlet of device is connect with the import of the carnallite drier.

2. coal water slurry gasification waste water according to claim 1 divides salt to crystallize zero-discharge treatment system, which is characterized in that described Pretreatment system includes chemical tendering equipment, filter plant and the ion-exchange unit, the water inlet of the chemical tendering equipment Mouth is connect with coal water slurry gasification waste line, and the water outlet of the chemical tendering equipment and the water inlet of the filter plant connect It connects, the water outlet of the filter plant is connect with the water inlet of the ion-exchange unit；It is equipped in the chemical tendering equipment Mud scraper, the mud discharging mouth of the chemical tendering equipment and the feed inlet of filter press connect.

3. coal water slurry gasification waste water according to claim 2 divides salt to crystallize zero-discharge treatment system, which is characterized in that described Filter plant includes V-type filter tank and ultrafiltration apparatus, and the water outlet in the V-type filter tank is connect with the water inlet of the ultrafiltration apparatus.

4. coal water slurry gasification waste water according to claim 1 divides salt to crystallize zero-discharge treatment system, which is characterized in that described Point salt system includes the primary reverse osmosis system, reuse pool, decarbonizer, two-stage reverse osmosis system, advanced oxidation system, one Grade nanofiltration system, the second level nanofiltration system, nanofiltration produce pond, the three-level counter-infiltration system and level Four counter-infiltration system, institute The production water out for stating primary reverse osmosis system is connect with the water inlet of the reuse pool, the concentrated water of the primary reverse osmosis system Outlet is connect with the water inlet of the decarbonizer, and the water inlet of the water outlet of the decarbonizer and the two-stage reverse osmosis system connects It connects；The production water out of the two-stage reverse osmosis system is connect with the water inlet of the reuse pool, the two-stage reverse osmosis system Concentrated water outlet connect with the water inlet of the advanced oxidation system；The water outlet of the advanced oxidation system is received with the level-one The water inlet of filter system connects, and the production water out of the level-one nanofiltration system is connect with the water inlet that the nanofiltration produces pond, institute The concentrated water outlet for stating level-one nanofiltration system is connect with the water inlet of the second level nanofiltration system, the water inlet of the second level nanofiltration system Mouth is also connect by regulating valve with the water outlet of the reuse pool；The production water out of the second level nanofiltration system and the nanofiltration Produce the water inlet connection in pond；The water outlet that the nanofiltration produces pond is connect with the water inlet of the three-level counter-infiltration system, institute The production water out for stating three-level counter-infiltration system is connect with the water inlet of the level Four counter-infiltration system；The level Four counter-infiltration system Production water out connect with the water inlet of the reuse pool, the outlet of the concentrated water of the level Four counter-infiltration system and the nanofiltration water The water inlet in pond connects；The three-level counter-infiltration system is that disc tube reverse osmosis (dt-ro) system, electric drive membranous system or rolling are reverse osmosis Any one in system, the level Four counter-infiltration system are any in disc tube reverse osmosis (dt-ro) system or rolling counter-infiltration system It is a kind of.

5. coal water slurry gasification waste water according to claim 1 divides salt to crystallize zero-discharge treatment system, which is characterized in that described Sodium chloride crystal system include the saltcake Multi-effect evaporation crystallizer, the saltcake dissolving tank, saltcake recrystallization evaporator, saltcake from Scheming and saltcake drying machine, the slurry outlet of the saltcake Multi-effect evaporation crystallizer are connect with the import of the liquid separation centrifuge, The material outlet of the saltcake dissolving tank is connect with the material inlet of saltcake recrystallization evaporator, and the saltcake recrystallization steams The material outlet of hair device is connect with the material inlet of the saltcake centrifuge, the solids of the saltcake centrifuge export with it is described The feed inlet of saltcake drying machine connects, and the discharge port of the saltcake drying machine is connect with the import of sodium sulphate warehouse.

6. coal water slurry gasification waste water according to claim 1 divides salt to crystallize zero-discharge treatment system, which is characterized in that described Salt crystal system includes the salt Multi-effect evaporation crystallizer, salt centrifuge, salt drying machine, and the solids exports and the salt The material inlet of centrifuge connects, and the solids outlet of the salt centrifuge is connect with the feed inlet of the salt drying machine, described The discharge port of salt drying machine is connect with the import of sodium chloride warehouse.

7. coal water slurry gasification waste water according to claim 1 divides salt to crystallize zero-discharge treatment system, which is characterized in that it is also It include the second mother liquid evaporation device, the import of the mother liquor outlet of the first mother liquid evaporation device and the second mother liquid evaporation device connects It connects, the slurry outlet of the second mother liquid evaporation device is connect with the import of the carnallite drier.

8. coal water slurry gasification waste water divides salt to crystallize Zero discharge treatment method, which is characterized in that it includes the following steps:

S1. pre-process: coal water slurry gasification waste water after conditioning tank homogeneous average, into pretreatment system carry out except firmly drop it is turbid, remove Silicon, pH adjust, remove the processing of organic matter, obtain pretreated waste water, and the index of the pretreated waste water is Ca²⁺=0mg/l, Mg²⁺=0mg/l, SiO₂≤ 15.00mg/l, turbidity≤1NTU, pH 7-8；

S2. divide salt: the pretreated waste water is delivered to primary reverse osmosis system and is concentrated, and obtains a concentrated water；It is described primary It after concentrated water tune pH is 4-5, is delivered in decarbonizer and removes removing carbon dioxide, obtain decarburization water outlet；The decarburization water outlet is delivered to two Grade counter-infiltration system is concentrated, and secondary concentrated water is obtained；The secondary concentrated water is delivered to advanced oxidation system and carries out organic matter Removal, obtains oxidized waste water；The primary reverse osmosis system, the two-stage reverse osmosis system production water be delivered to reuse pool It is interior, as recycle-water；The oxidized waste water is delivered to level-one nanofiltration system and carries out primary point salt treatment, and it is dense to obtain a nanofiltration Water；Nanofiltration concentrated water and the recycle-water are delivered to second level nanofiltration system according to the ratio that volume ratio is 4:3-4 and carry out Secondary point of salt treatment obtains secondary nanofiltration concentrated water；Nanofiltration produces water, the secondary nanofiltration produces water and is delivered to nanofiltration production In pond, as salt waste water to be gone out；The salt waste water to be gone out is delivered to three-level counter-infiltration system and is concentrated, and obtains concentrated water three times Water is produced three times；The water of production three times is delivered to level Four counter-infiltration system and is handled, and obtains four production water and is delivered to described return With pond, obtains four concentrated waters and be delivered to nanofiltration production pond, obtain four production water and be delivered to the reuse pool；

S3. the output of sodium chloride: the concentrated water three times is delivered to salt Multi-effect evaporation crystallizer and is evaporated crystallization, obtains salt slurry With salt mother liquor；The salt slurry, which is delivered in salt centrifuge, to be separated by solid-liquid separation, and solid sodium chloride is obtained；The solid sodium chloride It is delivered in salt drying machine and dries to water content≤0.1%, obtain sodium chloride crystal salt, the sodium chloride crystallization purity salt >= 98.5%；

S4. the output of sodium sulphate: the secondary nanofiltration concentrated water is delivered to saltcake Multi-effect evaporation crystallizer and is evaporated crystallization, obtains Saltcake slurry and saltcake mother liquor；The saltcake slurry is separated by solid-liquid separation, and solid sodium sulfate is obtained；The solid sodium sulfate conveying To saltcake dissolving tank carry out weight it is molten, in the saltcake dissolving tank solution be sodium sulphate saturated solution, obtain again solution；It is described Weight solution is delivered to saltcake recrystallization evaporator, obtains recrystallization slurry；The recrystallization slurry be delivered to saltcake centrifuge into Row is separated by solid-liquid separation, and obtains solid sodium sulfate；The solid sodium sulfate be delivered in saltcake drying machine dry to water content≤ 0.3%, obtain sulfate crystal salt, TOC≤50mg/KG, purity >=97% of the sulfate crystal salt；

S5. the processing of mother liquor: the salt mother liquor, the saltcake mother liquor, which are delivered in mother liquor freezing and crystallizing device, carries out freezing knot Crystalline substance, the COD≤18000mg/L, SiO of the salt mother liquor₂≤ 4000mg/l, the COD≤30000mg/L, SiO of the saltcake mother liquor₂ ≤ 5000mg/l obtains mother liquor slurry and freezing mother liquor；The mother liquor slurry obtains sal glauberi after solid-liquid separation treatment It is molten to carry out weight in the saltcake dissolving tank in the output of the sal glauberi Solid Conveying and Melting to the S4. sodium sulphate for solid； The freezing mother liquor, which is delivered in the first mother liquid evaporation device, carries out a point salt, obtains mixed salt slurry and concentrated mother liquor；The mixed salt slurry Material obtains dehydration mixed salt after being separated by solid-liquid separation, and the salt that the dehydration mixed salt is delivered in the output of the S3. sodium chloride is more Imitate crystallizing evaporator；The concentrated mother liquor is delivered to drying in carnallite drier, obtains carnallite.

9. coal water slurry gasification waste water according to claim 8 divides salt to crystallize Zero discharge treatment method, which is characterized in that described S1. it pre-processes specific as follows:

A1. chemical tendering: the coal water slurry gasification waste water be delivered to chemical tendering equipment carry out except drop firmly it is turbid, except silicon, removal have The processing of machine object, obtains chemical tendering water, and the index of the chemical tendering water is Ca²⁺≤50.00mg/l、Mg²⁺≤50.00mg/ l、SiO₂≤ 15.00mg/l, turbidity≤20NTU；Obtained sludge is delivered to filter press dehydration, obtains dewatered sludge；

A2. it filters: being delivered in filtration system after the chemical tendering water tune pH to 7-8 and drop turbid, drainage is obtained, it is described Cross turbidity≤1NTU of drainage；

A3. depth softens: the drainage of crossing is delivered to progress depth softening in ion-exchange unit, arrives the pretreated waste water.

10. coal water slurry gasification waste water according to claim 8 divides salt to crystallize Zero discharge treatment method, which is characterized in that institute In the processing for stating S5. mother liquor, the concentrated mother liquor is first delivered to the second mother liquid evaporation device and is concentrated, and obtains secondary concentration mother Liquid, the SiO of the concentrated mother liquor₂≤ 8000mg/l, then the secondary concentration mother liquor is delivered in the carnallite drier and is done It is dry, obtain the carnallite.