Semi-coke wastewater zero discharge treatment system

Abstract

The utility model provides a semi-coke wastewater zero-discharge treatment system, and belongs to the field of wastewater treatment. The semi-coke wastewater zero discharge treatment system comprises a phenol ammonia recovery unit, a biochemical unit, a concentration unit, a salt separation unit, a nanofiltration concentrated water evaporative crystallization unit, a nanofiltration produced water evaporative crystallization unit and a carnallite treatment unit. According to the utility model, the semi-coke wastewater is conveyed to the phenol-ammonia recovery unit for phenol-ammonia recovery treatment to obtain a phenol-ammonia product and waste liquid, and the phenol-ammonia in the semi-coke wastewater is recovered. Then the waste liquid is sequentially conveyed to a biochemical unit, a concentration unit, a salt separation unit, a nanofiltration concentrated water evaporation and crystallization unit, a nanofiltration produced water evaporation and crystallization unit and a carnallite treatment unit to be treated, sodium sulfate powder, sodium chloride powder and carnallite are finally obtained, and therefore the requirement for zero emission of the semi-coke waste water is met.

Description

Technical Field

[0001] The utility model relates to the technical field of wastewater treatment, in particular to a zero-discharge treatment system for blue carbon wastewater. Background Art

[0002] The production of semi-coke is to heat the coal to 600℃~800℃ by medium-low temperature dry distillation under the condition of isolating from air and oxygen, so that it decomposes to produce coal tar, semi-coke and semi-coke gas (raw gas). Semi-coke wastewater, also known as semi-coke wastewater, is the wastewater produced after oil removal during the condensation and purification of raw gas in the process of coal-to-semi-coke. Its pollutant composition is complex, mainly containing high concentrations of organic and inorganic substances. Organic matter contains a large amount of phenols and their derivatives, which are difficult to biodegrade and highly toxic substances. Its CODcr is as high as 30000mg / L~40000mg / L, phenols are 3000mg / L~5000mg / L, and ammonia nitrogen is 2500mg / L~3000mg / L. Compared with coking wastewater and coal gasification wastewater in coal chemical industry, semi-coke wastewater contains a large amount of medium and low molecular weight pollutants that have not been oxidized by high temperature, with high phenol content and complex types, greater toxicity, poor biodegradability, and high requirements for zero emission treatment.

[0003] In order to build a friendly social environment, we insist on putting environmental governance projects into operation simultaneously with new lignite production capacity to protect the water system and the atmospheric environment. At present, new coal chemical projects in China are basically tending to wastewater recycling and resource utilization. In addition, new coal chemical projects are required to achieve zero discharge of wastewater in areas with water shortage, lack of polluted water bodies, limited sewage discharge, water pollution, no environmental capacity and sensitive water environment. Due to the huge market demand, the lignite industry has developed rapidly, and the situation of achieving completely zero discharge of lignite wastewater is becoming increasingly severe.

[0004] It should be noted that the information disclosed in the background technology section of the utility model is only intended to deepen the understanding of the general background technology of the utility model, and should not be regarded as an admission or suggestion in any form that the information constitutes prior art already known to those skilled in the art. Utility Model Content

[0005] The utility model aims to provide a blue coke wastewater zero discharge treatment system to solve the problem of how to achieve blue coke wastewater zero discharge.

[0006] In order to solve the above technical problems, the utility model provides a zero-discharge treatment system for semi-coke wastewater, comprising:

[0007] The phenol-ammonia recovery unit is used to recover phenol-ammonia from the semi-coke wastewater to obtain phenol-ammonia products and waste liquid;

[0008] A pretreatment unit for sequentially subjecting the waste liquid to biochemical treatment, concentration, and salt separation to obtain nanofiltration concentrated water and nanofiltration product water, wherein the treatment unit includes a biochemical unit, a concentration unit, and a salt separation unit;

[0009] A nanofiltration concentrated water evaporation and crystallization unit for evaporating and crystallizing the nanofiltration concentrated water to obtain sodium sulfate powder and sodium sulfate mother liquor;

[0010] A nanofiltration product water evaporation and crystallization unit for evaporating and crystallizing the nanofiltration product water to obtain sodium chloride powder and sodium chloride mother liquor;

[0011] A miscellaneous salt treatment unit for drying the sodium chloride mother liquor and the sodium sulfate mother liquor to obtain miscellaneous salts.

[0012] Preferably, the phenolic ammonia recovery unit includes:

[0013] An oil removal device for separating oil and water from the semi-coke wastewater to obtain recycled wastewater;

[0014] A deacidification tower connected to the oil removal device;

[0015] A denitrification tower connected to the deacidification tower;

[0016] An extraction tower connected to the denitrification tower;

[0017] Wherein, the recycled wastewater is sequentially conveyed to the deacidification tower, the denitrification tower, and the extraction tower for deacidification treatment, denitrification treatment, and extraction treatment to obtain phenolic ammonia products and waste liquid.

[0018] Preferably, the extractant for the extraction treatment is methyl isobutyl ketone.

[0019] Preferably, the biochemical unit includes:

[0020] An oil separation tank for conveying the waste liquid to the oil separation tank to remove heavy oil in the waste liquid;

[0021] A dissolved air flotation device connected to the oil separation tank; for removing light oil from the waste liquid with heavy oil removed by means of dissolved air flotation;

[0022] A biochemical treatment module connected to the dissolved air flotation device for sequentially adjusting, anaerobic, anoxic, aerobic, sedimentation, denitrification, aeration, sedimentation, and physicochemical treatment of the waste liquid with light oil removed.

[0023] Preferably, the waste liquid is conveyed to a biochemical effluent CODcr treatment device for physicochemical treatment, and the biochemical effluent CODcr treatment device is an activated carbon adsorption process treatment device, or a Fenton process treatment device, or an ozone oxidation process treatment device.

[0024] Preferably, the concentration unit includes:

[0025] A first-stage high-density clarification tank, a first-stage filter, a first-stage ultrafiltration unit, and a reverse osmosis device connected in sequence, which are used to perform coagulation and sedimentation treatment on the waste liquid and then perform filtration treatment; perform reverse osmosis treatment on the waste liquid after filtration treatment to concentrate the waste liquid and obtain a concentrated liquid.

[0026] Preferably, the salt separation unit includes:

[0027] A second-stage high-density clarification tank, a second-stage filter, a concentrated water CODcr treatment device, a second-stage ultrafiltration unit, a chelating resin softening unit, and a nanofiltration device connected in sequence, which are used to perform coagulation and sedimentation, filtration, CODcr degradation, ultrafiltration, hardness removal, and nanofiltration treatment on the concentrated liquid in sequence to obtain nanofiltration concentrated water and nanofiltration product water.

[0028] Preferably, the nanofiltration concentrated water evaporation and crystallization unit includes:

[0029] A high-pressure nanofiltration device, a sodium sulfate defluorination and desilication device, a high-salt concentrated water CODcr degradation device, and a sodium sulfate evaporation and crystallization device connected in sequence, and the high-pressure nanofiltration device is connected to the nanofiltration device.

[0030] Preferably, the nanofiltration product water evaporation and crystallization unit includes:

[0031] A high-pressure reverse osmosis device, a sodium chloride defluorination and desilication device, and a sodium chloride evaporation and crystallization device connected in sequence, and the high-pressure reverse osmosis device is connected to the nanofiltration device.

[0032] Preferably, the miscellaneous salt treatment unit includes:

[0033] A mother liquor treatment device, which is respectively connected to the sodium chloride evaporation and crystallization device and the sodium sulfate evaporation and crystallization device, and is used to perform drying treatment on the sodium chloride mother liquor and the sodium sulfate mother liquor to obtain miscellaneous salts.

[0034] Compared with the prior art, the zero-discharge treatment system for semi-coke wastewater of the present invention has the following advantages:

[0035] In the present invention, the semi-coke wastewater is transported to the phenol and ammonia recovery unit for phenol and ammonia recovery treatment to obtain phenol and ammonia products and waste liquid, and the phenol and ammonia in the semi-coke wastewater are recovered. Then, the waste liquid is sequentially transported to the biochemical unit, the concentration unit, the salt separation unit, the nanofiltration concentrated water evaporation and crystallization unit, the nanofiltration product water evaporation and crystallization unit, and the miscellaneous salt treatment unit for treatment, and finally sodium sulfate powder, sodium chloride powder, and miscellaneous salts are obtained, thereby meeting the requirement of zero discharge of semi-coke wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a process flow diagram of the zero-discharge treatment system for semi-coke wastewater in an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0037] To make the objectives, advantages, and features of the present utility model clearer, the following further elaborates on the zero-emission treatment system for semi-coke wastewater proposed by the present utility model in conjunction with the accompanying drawings and specific embodiments. It should be noted that the accompanying drawings are in a very simplified form and use non-precise scales, only for conveniently and clearly assisting in explaining the objectives of the embodiments of the present utility model. It should be understood that the drawings in the specification do not necessarily show the specific structure of the present utility model in proportion, and the illustrative features used to explain certain principles of the present utility model in the drawings of the specification will also adopt a slightly simplified drawing method. The specific design features of the present utility model disclosed herein, such as specific dimensions, directions, positions, and shapes, will be partially determined by the specific application and usage environment. Also, in the following described embodiments, sometimes the same reference numerals are used commonly between different drawings to represent the same parts or parts with the same functions, and the repeated description thereof is omitted. In this specification, similar reference numerals and letters are used to represent similar items. Therefore, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0038] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present utility model, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0039] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present utility model. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0040] The core idea of the present utility model is to provide a zero-emission treatment system for semi-coke wastewater, which can meet the requirement of zero emission of semi-coke wastewater.

[0041] To achieve the above idea, the present utility model provides a zero-emission treatment system for semi-coke wastewater, referring to Figure 1A specific implementation of a zero-discharge treatment system for semi-coke wastewater is disclosed. The zero-discharge treatment system for semi-coke wastewater includes: a phenol and ammonia recovery unit for performing phenol and ammonia recovery treatment on the semi-coke wastewater to obtain phenol and ammonia products and waste liquid. A pretreatment unit for sequentially performing biochemical treatment, concentration treatment, and salt separation treatment on the waste liquid to obtain nanofiltration concentrate water and nanofiltration product water, wherein the treatment unit includes a biochemical unit, a concentration unit, and a salt separation unit. A nanofiltration concentrate water evaporation and crystallization unit for performing evaporation and crystallization on the nanofiltration concentrate water to obtain sodium sulfate powder and sodium sulfate mother liquor. A nanofiltration product water evaporation and crystallization unit for performing evaporation and crystallization on the nanofiltration product water to obtain sodium chloride powder and sodium chloride mother liquor. A miscellaneous salt treatment unit for performing drying treatment on the sodium chloride mother liquor and the sodium sulfate mother liquor to obtain miscellaneous salts.

[0042] Exemplarily, the phenol and ammonia recovery unit includes: an oil removal device for performing oil-water separation treatment on the semi-coke wastewater to obtain recycled wastewater. A deacidification tower connected to the oil removal device. A deammoniation tower connected to the deacidification tower. An extraction tower connected to the deammoniation tower; wherein the recycled wastewater is sequentially conveyed to the deacidification tower, the deammoniation tower, and the extraction tower for deacidification treatment, deammoniation treatment, and extraction treatment to obtain phenol and ammonia products and waste liquid.

[0043] Specifically, referring to Figure 1As shown in the figure, the semi-coke wastewater is transported to the phenol and ammonia recovery unit for phenol and ammonia recovery treatment to obtain phenol and ammonia products and waste liquid. The semi-coke wastewater is the condensate of semi-coke raw gas, with high contents of oil, phenol and ammonia. The semi-coke wastewater is first transported to an oil removal device, and the oil and water separation of the semi-coke wastewater is carried out through the oil removal device to reduce the oil content with a concentration of 1000mg / L - 1500mg / L to less than 200mg / L, and most of the heavy oil and light oil in the wastewater are recovered, which can reduce the influence of oil on the subsequent process. The oil-removed semi-coke wastewater is successively transported to a deacidification tower, a deammoniation tower and an extraction tower to reduce the acid gas, ammonia and phenol in the semi-coke wastewater. The deacidification tower and deammoniation tower processes can either adopt the two-tower pressurized stripping method or the single-tower pressurized stripping method to reduce the acid gas such as H2S with a concentration of about 100mg / L - 150mg / L and CO2 with a concentration of 4000mg / L - 5000mg / L in the semi-coke wastewater to about 10mg / L - 30mg / L H2S and 100mg / L - 300mg / L CO2, and reduce the ammonia concentration in the semi-coke wastewater from the original 3000mg / L - 5000mg / L to about 200mg / L. The semi-coke wastewater after removing the acid gas and ammonia is sent to the extraction tower, that is, the phenol removal device, and through the method of extraction and de-phenolization, the phenol in the semi-coke wastewater with an original concentration of 10000mg / L - 20000mg / L is recovered as phenol through extraction and rectification, and the phenol in the semi-coke wastewater is reduced to 500mg / L - 800mg / L. The extraction agent is methyl isobutyl ketone, and the extraction agent in the extraction phase and the raffinate phase is separated by stripping and then recycled. After the semi-coke wastewater is treated as above, phenol and ammonia products and waste liquid are obtained.

[0044] Exemplarily, the biochemical unit includes: an oil separation tank for transporting the waste liquid to the oil separation tank to remove the heavy oil in the waste liquid. A dissolved air flotation device is connected to the oil separation tank; it is used to remove the light oil in the waste liquid after removing the heavy oil by means of dissolved air flotation. A biochemical treatment module is connected to the dissolved air flotation device and is used to successively carry out adjustment, anaerobic treatment, anoxic treatment, aerobic treatment, sedimentation, denitrification, aeration, sedimentation and physicochemical treatment on the waste liquid after removing the light oil.

[0045] Specifically, referring to Figure 1 As shown in the figure, before the waste liquid is concentrated, the zero-discharge treatment system for semi-coke wastewater further includes: transporting the waste liquid to a biochemical unit for biochemical treatment. The biochemical treatment of the waste liquid further includes: transporting the waste liquid to an oil separation tank to remove the heavy oil in the waste liquid; removing the light oil in the waste liquid after removing the heavy oil by means of dissolved air flotation; successively carrying out adjustment, anaerobic treatment, anoxic treatment, aerobic treatment, sedimentation, denitrification, aeration and sedimentation treatment on the waste liquid after removing the light oil.

[0046] The waste liquid obtained in step S1 is transported to a biochemical unit for biochemical treatment. After the temperature of the semi-coke wastewater (i.e., the waste liquid) after reducing oil, acid gas, ammonia, and phenol in step S1 is lowered to below 40°C, it is sent to an oil separation tank. Since the raw water contains some oil, to ensure the stability of subsequent devices, first, the heavy oil in the wastewater is removed by gravity in the oil separation tank, and then the light oil is removed by dissolved air flotation, controlling the oil content in the wastewater to be below 20 mg / L. According to the characteristics of the wastewater, air, nitrogen, or carbon dioxide can be selected as the gas source for dissolved air in dissolved air flotation. The biochemical treatment module includes: an adjustment tank, an anaerobic tank, an anoxic tank, an aerobic tank, a primary sedimentation tank, a denitrification tank, an aeration tank, a secondary sedimentation tank, and a biochemical effluent CODcr treatment device. After oil removal, the waste liquid is transported to the adjustment tank. The adjustment tank performs homogenization and equalization treatment on the waste liquid to ensure the stability of water quality and water volume during subsequent treatment. When there are large fluctuations in the raw water quality, the waste liquid needs to be sent to an accident tank for temporary storage. After the system stabilizes, it is then sent to the adjustment tank at a small flow rate to ensure the stability of the biochemical system. The waste liquid treated by the adjustment tank is then input into the anaerobic tank. Chemotrophic heterotrophic anaerobic bacteria are cultivated in the anaerobic tank at a temperature of 25°C to 35°C. The high-molecular organic matter in the semi-coke wastewater is hydrolyzed and acidified into small-molecule compounds by the anaerobic bacteria, controlling the biodegradability index of the semi-coke wastewater in the anaerobic tank to be ≥0.3, and the oxidation-reduction potential to be -250 mV to -350 mV to ensure the biodegradability of the semi-coke wastewater. The semi-coke wastewater hydrolyzed and acidified in the anaerobic tank flows by gravity to the anoxic tank. Biological fillers or submersible agitators are installed in the anoxic tank. The semi-coke wastewater undergoes denitrification for nitrogen removal in the anoxic tank, controlling the dissolved oxygen in the anoxic tank to be 0.2 mg / L to 0.5 mg / L, and the mixed liquor suspended solids index to be 3 g / L to 7 g / L. After being treated in the anoxic tank, it is input into the aerobic tank. Autotrophic bacteria and heterotrophic aerobic microorganisms are cultivated in the aerobic tank at a temperature of 25°C to 35°C, controlling the dissolved oxygen in the wastewater in the aerobic tank to be 4 mg / L to 7 mg / L, the pH to be 6.5 to 7.5, and the MLSS to be 3 g / L to 4.5 g / L. The autotrophic bacteria nitrify ammonia and nitrogen in the semi-coke wastewater into nitrate nitrogen, and the heterotrophic aerobic microorganisms use the organic matter in the wastewater as a carbon source and energy source to synthesize cell substances, thereby removing the organic matter in the semi-coke wastewater. At the same time, the aerobic nitrification liquid is refluxed to the anoxic tank at 3 to 6 times the output flow rate of the anaerobic tank. The semi-coke wastewater treated in the aerobic tank flows by gravity to the primary sedimentation tank, and in the primary sedimentation tank, part of the particulate, non-biodegradable organic matter adsorbed by the activated sludge flocs and the particulate products of microbial attenuation are removed by sedimentation. At the same time, part of the sludge in the primary sedimentation tank is refluxed to the anoxic tank and the aerobic tank. The semi-coke wastewater that has completed decarbonization biochemical treatment is sent to the subsequent denitrification tank for denitrification treatment. An easily biodegradable carbon source is added to the denitrification tank, and the carbon source is selected as C 1～3Hydrocarbons or derivatives of hydrocarbons. The semi-coke wastewater removes the nitrate nitrogen produced by nitrification in the aerobic tank within 12 to 30 hours to remove the total nitrogen. The semi-coke wastewater treated in the denitrification tank is then input into the aeration tank. Air is introduced into the aeration tank, and the microorganisms continue to remove the organic matter in the semi-coke wastewater, controlling the dissolved oxygen in the aeration tank at 4 mg / L to 7 mg / L. The semi-coke wastewater treated in the aeration tank is then input into the secondary sedimentation tank. The semi-coke wastewater undergoes sedimentation in the secondary sedimentation tank to remove the particulate products of microbial attenuation in the aeration tank. At the same time, part of the sludge in the secondary sedimentation tank flows back to the aeration tank. After the above biochemical treatment, the content of organic matter CODcr in the semi-coke wastewater is about 200 mg / L - 350 mg / L, the cyanide is about 0.3 mg / L - 0.5 mg / L, the total nitrogen is less than or equal to 15 mg / L, and the ammonia nitrogen is less than or equal to 5 mg / L. Then the semi-coke wastewater is input into the biochemical effluent CODcr treatment device for treatment. Its effluent meets the direct discharge standard of the "Pollutant Discharge Standard for Coking Chemical Industry" (GB 16171-2012). The biochemical effluent CODcr treatment device can select CODcr treatment devices such as activated carbon adsorption devices, Fenton processes, and ozone oxidation processes.

[0047] Exemplarily, the concentration unit includes: a first-stage high-density clarifier, a first-stage filter, a first-stage ultrafiltration, and a reverse osmosis device connected in sequence, for performing coagulation sedimentation treatment on the waste liquid and then performing filtration treatment; performing reverse osmosis treatment on the waste liquid after filtration treatment to concentrate the waste liquid and obtain a concentrated solution.

[0048] Specifically, refer Figure 1 As shown, the semi-coke wastewater treated by the biochemical unit is transported to the concentration and salt separation unit. The concentration and salt separation unit includes a concentration unit and a salt separation unit. The semi-coke wastewater after removing substances such as organic matter, total nitrogen, ammonia nitrogen, organic nitrogen, and cyanide by the biochemical unit is sent to the concentration unit for concentration treatment. The concentration unit includes a first-stage high-density clarifier, a first-stage filter, a first-stage ultrafiltration, and a reverse osmosis device. The semi-coke wastewater is sent to the concentration unit and first input into the first-stage high-density clarifier. By adding agents such as sodium carbonate, NaOH, PAC, and PAM, the total calcium and magnesium hardness is reduced to about 100 mg / L - 150 mg / L, and it is discharged in the form of solid waste sludge. After the water discharged from the first-stage high-density clarifier is adjusted to neutral pH, it is sent to the filter to further remove the suspended substances in the water. After filtration, it is then input into the first-stage ultrafiltration device. The colloid, protein, microorganism, and macromolecular organic matter are intercepted by ultrafiltration, and at the same time, small molecule substances and dissolved solids (inorganic salts) in the semi-coke wastewater are allowed to pass through. Finally, the turbidity of the produced water ≤ 0.3 NTU, and SDI ≤ 3. After the semi-coke wastewater is treated by the first-stage ultrafiltration, it is sent to the reverse osmosis device for concentration by about 4 times. The reverse osmosis produced water can meet the requirements of the factory area's circulating water makeup water and be directly reused as production water in the production unit. After the reverse osmosis concentrated water is concentrated by 4 times, all kinds of organic and inorganic substances in it are concentrated and sent to the subsequent unit for further treatment.

[0049] Exemplarily, the salt separation unit includes: a secondary high-density clarifier, a secondary filter, a concentrated water CODcr treatment device, a secondary ultrafiltration, a chelating resin softening, and a nanofiltration device connected in sequence, which are used to sequentially perform coagulation sedimentation, filtration, CODcr degradation, ultrafiltration, hardness removal, and nanofiltration treatment on the concentrated liquid to obtain nanofiltration concentrated water and nanofiltration product water.

[0050] Specifically, refer to Figure 1As shown in the figure, the amount of the semi-coke wastewater concentrated by the concentration unit is reduced by about three-quarters, but the substance concentration is correspondingly concentrated by about 4 times and then sent to the salt separation unit for salt separation treatment. The salt separation unit includes a secondary high-density clarifier, a secondary filter, a concentrated water CODcr treatment device, a secondary ultrafiltration, chelating resin softening, and nanofiltration equipment. The concentrated liquid is sequentially subjected to coagulation precipitation, filtration, CODcr degradation, ultrafiltration, hardness removal, and nanofiltration treatment to obtain nanofiltration concentrated water and nanofiltration produced water. After being concentrated by the concentration unit, the total calcium and magnesium hardness concentration in the concentrated water rises to about 400 mg / L - 600 mg / L. It is input into the secondary high-density clarifier, and by continuously adding chemicals such as sodium carbonate, NaOH, PAC, and PAM, the total calcium and magnesium hardness in the semi-coke wastewater concentrated water is reduced to about 100 mg / L - 150 mg / L and discharged in the form of solid waste sludge. The effluent from the secondary high-density clarifier after precipitation is adjusted to neutral pH and then sent to the secondary filter to further remove suspended substances in the concentrated water. After reverse osmosis concentration, the CODcr content in the semi-coke wastewater is about 300 mg / L - 500 mg / L. However, excessive organic matter will cause fouling of the membrane system. Therefore, the semi-coke wastewater concentrated water is input into the concentrated water CODcr treatment device again, and its effluent CODcr content is reduced to 100 mg / L - 150 mg / L. The concentrated water CODcr treatment device can adopt processes such as granular activated carbon adsorption, ozone oxidation device, and wet oxidation for treatment. The wastewater after passing through the concentrated water CODcr treatment device is input into the secondary ultrafiltration device again. Colloids, proteins, microorganisms, and macromolecular organic matter are intercepted by ultrafiltration, while small molecule substances and dissolved solids (inorganic salts) in the semi-coke wastewater are allowed to pass through. Finally, the turbidity of the produced water ≤ 0.3 NTU, and SDI ≤ 3. Since the raw coal for producing semi-coke contains fluorides, after the coal undergoes medium and low-temperature dry distillation, the semi-coke wastewater produced also contains some fluoride ions correspondingly. The secondary ultrafiltration produced water is further input into the chelating resin to deeply exchange the calcium and magnesium hardness in the wastewater, effectively preventing calcium fluoride scaling in subsequent reverse osmosis and nanofiltration. The waste liquid after the chelating resin is saturated and regenerated is returned to the secondary high-density clarifier to implement physical and chemical methods, such as by adding soda ash and sodium hydroxide and adjusting the pH to 10 - 12, so that the calcium and magnesium ions in the semi-coke wastewater precipitate in the form of calcium carbonate and magnesium hydroxide to reduce the calcium and magnesium hardness. The semi-coke wastewater softened by the chelating resin is sent to the nanofiltration unit for salt separation. The nanofiltration membrane effectively intercepts divalent and higher-valent ions on the concentrated water side, while allowing monovalent ions to pass through the pore diameter and coexist on the produced water and concentrated water sides. Therefore, after nanofiltration salt separation, sulfate radicals are mainly intercepted on the concentrated water side, and chloride ions and sodium ions coexist on the concentrated water and produced water sides. The nanofiltration concentrated water is sent to the nanofiltration concentrated water evaporation and crystallization unit. The nanofiltration produced water is sent to the nanofiltration produced water evaporation and crystallization unit.

[0051] Exemplarily, the nanofiltration concentrated water evaporation and crystallization unit includes: a high-pressure nanofiltration device, a sodium sulfate defluorination and desilication device, a high-salt concentrated water CODcr degradation device, and a sodium sulfate evaporation and crystallization device connected in sequence, and the high-pressure nanofiltration device is connected to the nanofiltration device.

[0052] Specifically, refer Figure 1 As shown, the nanofiltration concentrated water is transported to the nanofiltration concentrated water evaporation and crystallization unit for treatment. The nanofiltration concentrated water evaporation and crystallization unit is to send about one-fourth of the concentrated water after nanofiltration salt separation of the semi-coke wastewater treated by the salt separation unit to the nanofiltration concentrated water evaporation and crystallization unit. The nanofiltration concentrated water evaporation and crystallization unit includes a high-pressure nanofiltration device, a sodium sulfate defluorination and desilication device, a high-salt concentrated water CODcr degradation device, and a sodium sulfate evaporation and crystallization device. According to the water quality of the nanofiltration concentrated water, the sulfate radical in it is further concentrated by high-pressure nanofiltration. The water produced by high-pressure nanofiltration is returned to the nanofiltration inlet in the salt separation unit for re-salt separation and concentration. After the TDS of the high-pressure nanofiltration concentrated water is concentrated to about 100,000 mg / L - 120,000 mg / L, the fluoride ions, silicon dioxide, CODcr, etc. in it are also correspondingly concentrated. Fluoride ions will corrode the evaporation and crystallization device, silicon dioxide will cause scaling and affect the use efficiency, and the high concentration of CODcr after concentration will affect the efficiency of the evaporation and crystallization device. To ensure the long-term stable operation of the evaporation and crystallization device, the high-pressure nanofiltration concentrated water is treated by physical and chemical methods, such as adding defluorination and desilication agents and then coagulation precipitation to reduce the fluoride ions and silicon dioxide in the wastewater, and then this part of the concentrated water is sent to the high-salt concentrated water CODcr degradation device. After effectively reducing the CODcr in the wastewater, it is sent to the evaporation and crystallization unit. The concentrated liquid before entering the evaporation and crystallization device contains both monovalent chloride ions and divalent sulfate ions. By means of steam heat exchange, part of the water in the wastewater is evaporated, and then, taking advantage of the different solubilities of sodium chloride and sodium sulfate at different temperatures, the concentrated liquid after evaporation is rapidly cooled, so that sodium sulfate precipitates in the form of sodium sulfate decahydrate, and then after redissolution and evaporation, sodium sulfate products are obtained for sale. The water after evaporation in the whole process is condensed and cooled and then mixed with the reverse osmosis produced water and reused in the production unit.

[0053] Exemplarily, the nanofiltration produced water evaporation and crystallization unit includes: a high-pressure reverse osmosis device, a sodium chloride defluorination and desilication device, and a sodium chloride evaporation and crystallization device connected in sequence, and the high-pressure reverse osmosis device is connected to the nanofiltration device.

[0054] Specifically, refer Figure 1As shown, the nanofiltration produced water is transported to the nanofiltration produced water evaporation and crystallization unit for treatment. Nanofiltration produced water evaporation and crystallization unit: About three-quarters of the produced water after nanofiltration and salt separation of the semi-coke wastewater treated by the separation unit is sent to the nanofiltration produced water evaporation and crystallization unit. The nanofiltration produced water evaporation and crystallization unit includes a high-pressure reverse osmosis device, a sodium chloride defluorination and desilication device, and a sodium chloride evaporation and crystallization device. According to the water quality, the nanofiltration produced water is further concentrated by high-pressure reverse osmosis. The high-pressure reverse osmosis produced water is mixed with the reverse osmosis produced water in the concentration unit and then recycled to the production unit. After the high-pressure reverse osmosis concentrated water is concentrated to a TDS of about 70,000 mg / L - 100,000 mg / L, ions such as fluoride ions and silicon dioxide are also concentrated. Fluoride ions will corrode the evaporation and crystallization device, and silicon dioxide will cause scaling and affect the use efficiency. To ensure the long-term stable operation of the evaporation and crystallization device, the high-pressure reverse osmosis concentrated water is treated by physical and chemical methods. After adding defluorination and desilication agents and coagulating and precipitating to reduce the fluoride ions and silicon dioxide in the wastewater, this part of the concentrated water is sent to the evaporation and crystallization unit. Through steam heat exchange, the water in the wastewater is evaporated, and then sodium chloride is crystallized out and sold as industrial salt. The evaporated water is condensed and cooled and then mixed with the reverse osmosis produced water and recycled to the production unit.

[0055] Exemplarily, the miscellaneous salt treatment unit includes: a mother liquor treatment device, which is respectively connected to the sodium chloride evaporation and crystallization device and the sodium sulfate evaporation and crystallization device, and is used for drying the sodium chloride mother liquor and the sodium sulfate mother liquor to obtain miscellaneous salts.

[0056] Specifically, refer Figure 1 As shown. 3% - 5% of the sodium chloride mother liquor produced in the sodium chloride evaporation and crystallization device and 3% - 5% of the sodium sulfate mother liquor produced in the sodium sulfate evaporation and crystallization device enter the mother liquor treatment device for drying treatment and are treated as solid waste to obtain miscellaneous salts.

[0057] In this embodiment, the semi-coke wastewater is transported to the phenol and ammonia recovery unit for phenol and ammonia recovery treatment to obtain phenol and ammonia products and waste liquid, and the phenol and ammonia in the semi-coke wastewater are recovered. Then the waste liquid is successively transported to the biochemical unit, the concentration unit, the salt separation unit, the nanofiltration concentrated water evaporation and crystallization unit, the nanofiltration produced water evaporation and crystallization unit and the miscellaneous salt treatment unit for treatment, and finally sodium sulfate powder, sodium chloride powder and miscellaneous salts are obtained, so as to meet the requirement of zero discharge of semi-coke wastewater.

[0058] In summary, the above embodiments have described in detail different configurations of the semi-coke wastewater zero-discharge treatment system. Of course, the above description is only a description of the preferred embodiments of the present invention, and does not limit the scope of the present invention in any way. The present invention includes but is not limited to the configurations listed in the above embodiments. Those skilled in the art can draw inferences from the content of the above embodiments. Any changes and modifications made by ordinary technical personnel in the field of the present invention according to the above disclosure are within the protection scope of the claims.

Claims

1. A semi-coke wastewater zero-discharge treatment system, characterized in that, Including: A phenol and ammonia recovery unit for recovering phenol and ammonia from semi-coke wastewater to obtain phenol-ammonia products and waste liquid; A pretreatment unit for successively subjecting the waste liquid to biochemical treatment, concentration, and salt separation to obtain nanofiltration concentrated water and nanofiltration product water, wherein the treatment unit includes a biochemical unit, a concentration unit, and a salt separation unit; A nanofiltration concentrated water evaporation and crystallization unit for evaporating and crystallizing the nanofiltration concentrated water to obtain sodium sulfate powder and sodium sulfate mother liquor; A nanofiltration product water evaporation and crystallization unit for evaporating and crystallizing the nanofiltration product water to obtain sodium chloride powder and sodium chloride mother liquor; A miscellaneous salt treatment unit for drying the sodium chloride mother liquor and the sodium sulfate mother liquor to obtain miscellaneous salts.

2. The zero-emission treatment system for semi-coke wastewater according to claim 1, wherein, The phenol and ammonia recovery unit includes: An oil removal device for separating oil and water from the semi-coke wastewater to obtain recycled wastewater; A deacidification tower connected to the oil removal device; A deammoniation tower connected to the deacidification tower; An extraction tower connected to the deammoniation tower; Wherein, the recycled wastewater is successively conveyed to the deacidification tower, the deammoniation tower, and the extraction tower for deacidification treatment, deammoniation treatment, and extraction treatment to obtain phenol-ammonia products and waste liquid.

3. The semi-coke wastewater zero-discharge treatment system according to claim 2, characterized in that, The extractant for the extraction treatment is methyl isobutyl ketone.

4. The semi-coke wastewater zero-discharge treatment system according to claim 1, characterized in that The biochemical unit includes: An oil separation tank for conveying the waste liquid to the oil separation tank to remove heavy oil in the waste liquid; A dissolved air flotation device connected to the oil separation tank for removing light oil from the waste liquid with removed heavy oil by means of dissolved air flotation; A biochemical treatment module connected to the dissolved air flotation device for successively adjusting, anaerobically treating, anoxically treating, aerobically treating, precipitating, denitrifying, aerating, precipitating, and physicochemically treating the waste liquid with removed light oil.

5. The semi-coke wastewater zero-discharge treatment system according to claim 4, characterized in that, The waste liquid is conveyed to a biochemical effluent CODcr treatment device for physicochemical treatment, and the biochemical effluent CODcr treatment device is an activated carbon adsorption process treatment device, or a Fenton process treatment device, or an ozone oxidation process treatment device.

6. The zero-emission treatment system for semi-coke wastewater according to claim 1, wherein The concentration unit includes: A first-stage high-density clarifier, a first-stage filter, a first-stage ultrafiltration, and a reverse osmosis device connected in sequence for subjecting the waste liquid to coagulation and precipitation treatment and then to filtration treatment; and subjecting the filtered waste liquid to reverse osmosis treatment to concentrate the waste liquid to obtain a concentrated liquid.

7. The semi-coke wastewater zero-discharge treatment system according to claim 6, wherein, The salt separation unit includes: A second-stage high-density clarifier, a second-stage filter, a concentrated water CODcr treatment device, a second-stage ultrafiltration, chelating resin softening, and a nanofiltration device connected in sequence for successively subjecting the concentrated liquid to coagulation and precipitation, filtration, CODcr degradation, ultrafiltration, hardness removal, and nanofiltration treatment to obtain nanofiltration concentrated water and nanofiltration product water.

8. The semi-coke wastewater zero-discharge treatment system according to claim 1, wherein The nanofiltration concentrated water evaporation and crystallization unit includes: A high-pressure nanofiltration device, a sodium sulfate defluorination and desilication device, a high-salt concentrated water CODcr degradation device, and a sodium sulfate evaporation and crystallization device connected in sequence, and the high-pressure nanofiltration device is connected to the nanofiltration device.

9. The semi-coke wastewater zero-discharge treatment system according to claim 8, characterized in that, The nanofiltration product water evaporation and crystallization unit includes: A high-pressure reverse osmosis device, a sodium chloride defluorination and desilication device, and a sodium chloride evaporation and crystallization device connected in sequence, and the high-pressure reverse osmosis device is connected to the nanofiltration device.

10. The semi-coke wastewater zero-discharge treatment system according to claim 9, wherein, The miscellaneous salt treatment unit includes: The mother liquor treatment device is respectively connected to the sodium chloride evaporation and crystallization device and the sodium sulfate evaporation and crystallization device, and is used for drying the sodium chloride mother liquor and the sodium sulfate mother liquor to obtain miscellaneous salts.

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