Coal chemical industry wastewater crystal salt resource recycling system

Abstract

The utility model discloses a coal chemical industry wastewater crystal salt resource recycling system which comprises a pretreatment softening device, a waste water recycling device and a waste water recycling device, an evaporation concentration device; a first evaporative crystallization system; a first freezing crystallization device; a second evaporative crystallization system; and a second freezing crystallization device. According to different properties of sodium sulfate, sodium chloride and sodium nitrate, the sodium sulfate, the sodium chloride and the sodium nitrate are crystallized and separated through the pretreatment softening device, the evaporation concentration device, the first evaporation crystallization system, the first freezing crystallization device, the second evaporation crystallization system and the second freezing crystallization device, so that the obtained sodium sulfate, the sodium chloride and the sodium nitrate reach industrial recycling standards; therefore, zero discharge and resource utilization of the wastewater are realized.

Description

Technical Field

[0001] This utility model relates to the field of wastewater treatment technology, specifically to a resource recovery system for crystalline salts from coal chemical wastewater. Background Technology

[0002] Coal chemical industry generates a large amount of high-salt wastewater. The traditional treatment method is to evaporate it naturally in an evaporation pond or to evaporate and crystallize it using an evaporation crystallization device. This results in mixed salts that cannot be utilized as resources. The main components are sodium sulfate, sodium chloride, and a small amount of sodium nitrate.

[0003] Currently, the treatment of high-salt wastewater from coal chemical industry basically adopts a resource recovery route of pretreatment + membrane concentration + evaporation crystallization. This technical route produces mixed salts containing a variety of inorganic salts and a large amount of organic matter, which are easily soluble in water, have poor stability, are difficult to solidify, and are prone to causing secondary pollution.

[0004] Therefore, the existing resource recovery systems and processes for crystalline salts from coal chemical wastewater need further improvement. Utility Model Content

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a coal chemical wastewater crystallization salt resource recovery system. This system can effectively treat high-salt coal chemical wastewater to obtain sodium sulfate, sodium chloride and sodium nitrate that meet industrial reuse standards, thereby achieving zero discharge and resource utilization of wastewater.

[0006] Regarding the resource recovery system for crystalline salts from coal chemical wastewater, in order to achieve the above-mentioned objectives, this utility model adopts the following solution: a resource recovery system for sodium sulfate, sodium chloride, and sodium nitrate from coal chemical wastewater, characterized by comprising:

[0007] The pretreatment softening device is used to pretreat and soften high-salt wastewater from coal chemical industry to remove impurity ions from the wastewater.

[0008] An evaporation and concentration device is used to treat pre-treated and softened high-salt coal chemical wastewater to increase its salinity; the outlet of the pre-treatment and softening device is connected to the inlet of the evaporation and concentration device.

[0009] The first evaporation crystallization system is used to evaporate and crystallize the high-salt wastewater concentrate that has been treated by the evaporation and concentration device, so that sodium sulfate in the high-salt wastewater concentrate precipitates out; the liquid outlet of the evaporation and concentration device is connected to the liquid inlet of the first evaporation crystallization system.

[0010] The first freezing crystallization device is used to freeze crystallize the mother liquor discharged from the first evaporation crystallization system to precipitate sodium sulfate in the mother liquor; the mother liquor outlet of the first evaporation crystallization system is connected to the inlet of the first freezing crystallization device.

[0011] The second evaporation crystallization system is used to evaporate and crystallize the mother liquor that has been treated by the first freezing crystallization device, so that sodium oxide in the mother liquor crystallizes out; the outlet end of the second evaporation crystallization system is connected to the inlet end of the second evaporation crystallization system.

[0012] The second cryo-crystallization device is used to cool and crystallize the mother liquor transported from the second evaporation-crystallization system, so that sodium nitrate in the mother liquor crystallizes out; the liquid outlet of the second evaporation-crystallization system is connected to the liquid inlet of the second cryo-crystallization device.

[0013] As another improvement to the resource recovery system for sodium sulfate, sodium chloride, and sodium nitrate from coal chemical wastewater described in this utility model, the first evaporation crystallization system includes a first evaporation crystallization device. The inlet end of the first evaporation crystallization device is connected to the outlet end of the first evaporation concentration device. The outlet end of the first evaporation crystallization device is connected to the inlet end of the first centrifuge. The outlet end of the first centrifuge is connected to both the first freezing crystallization device and the first evaporation crystallization device. The crystallization outlet end of the first centrifuge is connected to the inlet end of the first washing tank. The waste liquid outlet end of the first washing tank is connected to the inlet end of the first evaporation crystallization device. The outlet end of the first washing tank is connected to the inlet end of the second centrifuge. The outlet end of the second centrifuge is connected to the inlet end of the first washing tank. The discharge end of the second centrifuge is connected to the inlet end of the first drying device.

[0014] As another improvement to the coal chemical wastewater sodium sulfate, sodium chloride, and sodium nitrate resource recovery system of this utility model, the liquid outlet of the first freezing crystallization device is connected to the liquid inlet of the third centrifuge, and the liquid outlet of the third centrifuge is connected to the liquid inlet of the first evaporation crystallization system and the liquid inlet of the second evaporation crystallization system, respectively.

[0015] As another improvement to the resource recovery system for sodium sulfate, sodium chloride, and sodium nitrate from coal chemical wastewater described in this utility model, the second evaporation crystallization system includes a second evaporation crystallization device. The inlet end of the second evaporation crystallization device is connected to the outlet end of the second evaporation concentration device. The outlet end of the second evaporation crystallization device is connected to the inlet end of a fourth centrifuge. The outlet end of the fourth centrifuge is connected to both a second freezing crystallization device and a second evaporation crystallization device. The crystallization outlet end of the fourth centrifuge is connected to the inlet end of a second washing tank. The waste liquid outlet end of the second washing tank is connected to the inlet end of the second evaporation crystallization device. The outlet end of the second washing tank is connected to the inlet end of a fifth centrifuge. The outlet end of the fifth centrifuge is connected to the inlet end of the second washing tank. The discharge end of the fifth centrifuge is connected to the inlet end of a second drying device.

[0016] As another improvement to the coal chemical wastewater sodium sulfate, sodium chloride, and sodium nitrate resource recovery system of this utility model, the discharge end of the second freezing crystallization device is connected to the feed end of the sixth centrifuge, and the discharge end of the sixth centrifuge is connected to the feed end of the second evaporation crystallization system and the feed end of the third drying device, respectively.

[0017] As another improvement to the resource recovery system for sodium sulfate, sodium chloride, and sodium nitrate from coal chemical wastewater described in this utility model, it also includes an inlet tank. The inlet end of the inlet tank is connected to the inlet pipe for high-salt coal chemical wastewater, and the outlet end of the inlet tank is connected to the inlet end of the pretreatment softening device.

[0018] As another improvement to the resource recovery system for sodium sulfate, sodium chloride, and sodium nitrate from coal chemical wastewater described in this utility model, the sludge discharge end of the pretreatment softening device is connected to the feed end of the plate and frame filter press.

[0019] In summary, the advantages of this utility model over the prior art are:

[0020] This invention utilizes the different properties of sodium sulfate, sodium chloride, and sodium nitrate. Through a pretreatment softening device, an evaporation and concentration device, a first evaporation crystallization system, a first freezing crystallization device, a second evaporation crystallization system, and a second freezing crystallization device, sodium sulfate, sodium chloride, and sodium nitrate are crystallized and separated to meet industrial reuse standards, thereby achieving zero discharge and resource utilization of wastewater. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the present invention. Detailed Implementation

[0022] The above-mentioned and other technical features and advantages of this utility model will be described in more detail below with reference to the accompanying drawings.

[0023] like Figure 1 As shown, a resource recovery system for sodium sulfate, sodium chloride, and sodium nitrate from coal chemical wastewater includes:

[0024] Pretreatment softening device 1 is used to pretreat and soften high-salinity wastewater from coal chemical industry to remove impurity ions from the wastewater; the pretreatment softening device 1

[0025] Evaporation and concentration device 2 is used to treat pre-treated and softened coal chemical high-salt wastewater to increase its salinity; the liquid outlet of the pre-treatment and softening device 1 is connected to the liquid inlet of the evaporation and concentration device 2.

[0026] The first evaporation crystallization system 3 is used to perform evaporation crystallization treatment on the high-salt wastewater concentrate after being treated by the evaporation concentration device 2, so that sodium sulfate in the high-salt wastewater concentrate precipitates out; the liquid outlet of the evaporation concentration device 2 is connected to the liquid inlet of the first evaporation crystallization system 3.

[0027] The first freezing crystallization device 4 is used to freeze crystallize the mother liquor discharged from the first evaporation crystallization system 3, so that sodium sulfate in the mother liquor precipitates out; the mother liquor outlet of the first evaporation crystallization system 3 is connected to the inlet of the first freezing crystallization device 4.

[0028] The second evaporation crystallization system 5 is used to evaporate and crystallize the mother liquor that has been treated by the first freezing crystallization device 4, so that sodium oxide in the mother liquor crystallizes out; the outlet end of the second evaporation crystallization system 5 is connected to the inlet end of the second evaporation crystallization system 5.

[0029] The second freezing crystallization device 6 is used to cool and crystallize the mother liquor transported from the second evaporation crystallization system 5, so that sodium nitrate in the mother liquor crystallizes out; the liquid outlet of the second evaporation crystallization system 5 is connected to the liquid inlet of the second freezing crystallization device 6.

[0030] This invention utilizes the different properties of sodium sulfate, sodium chloride, and sodium nitrate. Through a pretreatment softening device, an evaporation and concentration device, a first evaporation crystallization system, a first freezing crystallization device, a second evaporation crystallization system, and a second freezing crystallization device, sodium sulfate, sodium chloride, and sodium nitrate are crystallized and separated to meet industrial reuse standards, thereby achieving zero discharge and resource utilization of wastewater.

[0031] The first evaporation crystallization system 3 of this utility model includes a first evaporation crystallization device 31. The liquid inlet of the first evaporation crystallization device 31 is connected to the liquid outlet of the first evaporation concentration device 2. The liquid outlet of the first evaporation crystallization device 31 is connected to the liquid inlet of the first centrifuge 32. The liquid outlet of the first centrifuge 32 is connected to the first freezing crystallization device 4 and the first evaporation crystallization device 31 respectively. The crystallization discharge end of the first centrifuge 32 is connected to the feed end of the first washing tank 33. The waste liquid discharge end of the first washing tank 33 is connected to the liquid inlet of the first evaporation crystallization device 31. The liquid outlet of the first washing tank 33 is connected to the liquid inlet of the second centrifuge 34. The liquid outlet of the second centrifuge 34 is connected to the liquid inlet of the first washing tank 33. The discharge end of the second centrifuge 34 is connected to the feed end of the first drying device 35.

[0032] The liquid outlet of the first cryogenic crystallization device 4 is connected to the liquid inlet of the third centrifuge 7. The liquid outlet of the third centrifuge 7 is connected to the liquid inlet of the first evaporative crystallization system 3 and the liquid inlet of the second evaporative crystallization system 5, respectively.

[0033] The second evaporation crystallization system 5 of this utility model includes a second evaporation crystallization device 51. The liquid inlet of the second evaporation crystallization device 51 is connected to the liquid outlet of the second evaporation concentration device 2. The liquid outlet of the second evaporation crystallization device 51 is connected to the liquid inlet of the fourth centrifuge 52. The liquid outlet of the fourth centrifuge 52 is connected to the second freezing crystallization device 6 and the second evaporation crystallization device 51 respectively. The crystallization discharge end of the fourth centrifuge 52 is connected to the feed end of the second washing tank 53. The waste liquid discharge end of the second washing tank 53 is connected to the liquid inlet of the second evaporation crystallization device 51. The liquid outlet of the second washing tank 53 is connected to the liquid inlet of the fifth centrifuge 54. The liquid outlet of the fifth centrifuge 54 is connected to the liquid inlet of the second washing tank 53. The discharge end of the fifth centrifuge 54 is connected to the feed end of the second drying device 55.

[0034] The discharge end of the second freeze crystallization device 6 of this invention is connected to the feed end of the sixth centrifuge 8, and the discharge end of the sixth centrifuge 8 is connected to the feed end of the second evaporation crystallization system 5 and the feed end of the third drying device 9, respectively.

[0035] The present invention also includes a water inlet tank 10, the inlet end of which is connected to the inlet pipe of high-salt wastewater from coal chemical industry, and the outlet end of which is connected to the inlet end of the pretreatment softening device 1.

[0036] The sludge discharge end of the pretreatment softening device 1 of this utility model is connected to the feed end of the plate and frame filter press 11.

[0037] This utility model relates to a recovery process based on the aforementioned coal chemical wastewater sodium sulfate, sodium chloride, and sodium nitrate resource recovery system, comprising the following steps:

[0038] S1, Pretreatment softening

[0039] High-salinity wastewater from coal chemical plants is fed into pretreatment softening unit 1, where liquid alkali is added to adjust the pH to 11-13, causing magnesium ions in the wastewater to precipitate as magnesium hydroxide. Sodium carbonate is then added, causing calcium ions to precipitate as calcium carbonate. After softening, the pH of the wastewater is adjusted to 6-8 using concentrated sulfuric acid, resulting in softened high-salinity wastewater from coal chemical plants. Coal chemical wastewater generally contains a large amount of calcium and magnesium ions, as well as trace amounts of other metal ions. Softening pretreatment removes most of the calcium and magnesium ions. The sludge from the softening pretreatment is pressed into sludge cakes using a plate and frame filter press. This sludge is considered general solid waste, resulting in low treatment costs.

[0040] S2, Evaporation and Concentration

[0041] The coal chemical high-salt softened wastewater in step S1 is sent to the evaporation and concentration device 2 for evaporation and concentration to increase the salt content, and a coal chemical high-salt wastewater concentrate is obtained.

[0042] S3, single-stage evaporation crystallization

[0043] The coal chemical high-salt wastewater concentrate from step S2 is sent to the first evaporation crystallization system 3 to precipitate sodium sulfate. The crystallization slurry is then separated by centrifugation to obtain sodium sulfate solid and evaporation mother liquor.

[0044] This invention can roughly control the purity of the precipitated sodium sulfate product by controlling the concentration of sodium chloride in the liquid phase of the evaporation system.

[0045] The material is further evaporated and concentrated in the first evaporation and crystallization device 31 until crystallization. The crystallized slurry is pumped to the first centrifuge 32 for centrifugation to obtain sodium sulfate solid. In order to further ensure the purity of sodium sulfate, the precipitated sodium sulfate enters the first washing tank 33 for washing to further improve the purity. The washing waste liquid is returned to the first evaporation and crystallization device 31 for further evaporation and crystallization. The washing slurry is centrifuged in the second centrifuge 34 to obtain pure sodium sulfate. After drying in the first drying system 35, sodium sulfate (sodium sulfate) is obtained as a by-product.

[0046] This invention controls the sodium chloride content in the first evaporation crystallization device 31 by discharging the mother liquor, which can ensure the purity of sodium sulfate obtained by evaporation crystallization. Generally, the sodium chloride content in the evaporation mother liquor is controlled at about 20-24%. When the sodium chloride content in the system is high, part of the mother liquor is discharged to the first freezing crystallization device 4.

[0047] S4, single-freeze crystallization

[0048] The mother liquor from step S3 is sent to the first freezing crystallization device 4, and the temperature is controlled from -5°C to -10°C to allow sodium sulfate in the mother liquor to crystallize out. Sodium sulfate decahydrate and freezing mother liquor are obtained by centrifugation.

[0049] The mother liquor discharged from the first evaporation crystallization system 3 has a high sodium chloride content, as well as a small amount of sodium sulfate and some sodium nitrate. In the first freezing crystallization device 4, this mother liquor is frozen to -5°C to -10°C. The sodium sulfate in the material can basically crystallize out in the form of sodium sulfate decahydrate. The sodium sulfate decahydrate is obtained by centrifugation by the third centrifuge 7. The obtained sodium sulfate decahydrate is transported to the first evaporation crystallization device 3 and processed together with other materials. Sodium sulfate is obtained by evaporation and crystallization. The frozen mother liquor is transported to the second evaporation crystallization system 5.

[0050] S5, Secondary evaporation crystallization

[0051] The frozen mother liquor from step S4 is sent to the second evaporation crystallization system 5 for evaporation crystallization treatment, so that sodium chloride in the frozen mother liquor precipitates out; sodium chloride and hot mother liquor are obtained by separation.

[0052] The mother liquor after freezing treatment by the first freezing crystallization device 4 contains virtually no sodium sulfate, but mainly sodium chloride and some sodium nitrate. The mother liquor is evaporated by the second evaporation crystallization system 5, and the sodium chloride will continuously crystallize out. The slurry is then centrifuged by the fourth centrifuge 52 while it is still hot to obtain sodium chloride. Sodium chloride is then obtained by washing in the second washing tank 53, centrifuging by the fifth centrifuge 54, and drying by the second drying device 55.

[0053] As evaporation continues, sodium nitrate in the material is continuously enriched. When its concentration reaches 40-50%, the hot mother liquor obtained by centrifugation in the fourth centrifuge 52 is transported to the second freezing crystallization device 6.

[0054] S6, Secondary Freezing Crystallization

[0055] The hot mother liquor in step S5 is cooled and crystallized to precipitate sodium nitrate crystals; sodium nitrate can be obtained by centrifugation.

[0056] The hot mother liquor in the second evaporation crystallization system 5, in which the sodium nitrate concentration has been enriched to 40-50%, is cooled to approximately 10-20 degrees Celsius, causing some sodium nitrate to crystallize out. This crystallizes and precipitates out after centrifugation in the sixth centrifuge 8, yielding sodium nitrate, which is then dried in the third drying unit 9.

[0057] After drying, it can be reused. The centrifuged mother liquor is then returned to the second evaporation and crystallization unit 51 for further processing.

[0058] The foregoing has shown and described the basic principles and main features of this utility model, as well as its advantages. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A resource recovery system for crystalline salts from coal chemical wastewater, characterized in that... Including: The pretreatment softening device is used to pretreat and soften high-salt wastewater from coal chemical industry to remove impurity ions from the wastewater. Evaporation and concentration equipment is used to treat pretreated and softened coal chemical high-salt wastewater, thereby increasing its salinity. The liquid outlet of the pretreatment softening device is connected to the liquid inlet of the evaporation and concentration device; The first evaporation crystallization system is used to evaporate and crystallize the high-salt wastewater concentrate that has been treated by the evaporation and concentration device, so that sodium sulfate in the high-salt wastewater concentrate precipitates out; the liquid outlet of the evaporation and concentration device is connected to the liquid inlet of the first evaporation crystallization system. The first freezing crystallization device is used to freeze crystallize the mother liquor discharged from the first evaporation crystallization system to precipitate sodium sulfate in the mother liquor; the mother liquor outlet of the first evaporation crystallization system is connected to the inlet of the first freezing crystallization device. The second evaporation crystallization system is used to evaporate and crystallize the mother liquor that has been treated by the first freezing crystallization device, so that sodium oxide in the mother liquor crystallizes out; the outlet end of the second evaporation crystallization system is connected to the inlet end of the second evaporation crystallization system. The second cryo-crystallization device is used to cool and crystallize the mother liquor transported from the second evaporation-crystallization system, so that sodium nitrate in the mother liquor crystallizes out; the liquid outlet of the second evaporation-crystallization system is connected to the liquid inlet of the second cryo-crystallization device.

2. The coal chemical wastewater crystallized salt resource recovery system according to claim 1, characterized in that... The first evaporation crystallization system includes a first evaporation crystallization device. The inlet of the first evaporation crystallization device is connected to the outlet of the first evaporation concentration device. The outlet of the first evaporation crystallization device is connected to the inlet of the first centrifuge. The outlet of the first centrifuge is connected to both the first freezing crystallization device and the first evaporation crystallization device. The crystallization outlet of the first centrifuge is connected to the inlet of the first washing tank. The waste liquid outlet of the first washing tank is connected to the inlet of the first evaporation crystallization device. The outlet of the first washing tank is connected to the inlet of the second centrifuge. The outlet of the second centrifuge is connected to the inlet of the first washing tank. The discharge end of the second centrifuge is connected to the inlet of the first drying device.

3. The coal chemical wastewater crystallized salt resource recovery system according to claim 2, characterized in that... The liquid outlet of the first freezing crystallization device is connected to the liquid inlet of the third centrifuge, and the liquid outlet of the third centrifuge is connected to the liquid inlet of the first evaporation crystallization system and the liquid inlet of the second evaporation crystallization system, respectively.

4. The coal chemical wastewater crystallized salt resource recovery system according to claim 1, characterized in that... The second evaporation crystallization system includes a second evaporation crystallization device. The inlet of the second evaporation crystallization device is connected to the outlet of the second evaporation concentration device. The outlet of the second evaporation crystallization device is connected to the inlet of a fourth centrifuge. The outlet of the fourth centrifuge is connected to both a second freezing crystallization device and a second evaporation crystallization device. The crystallization outlet of the fourth centrifuge is connected to the inlet of a second washing tank. The waste liquid outlet of the second washing tank is connected to the inlet of the second evaporation crystallization device. The outlet of the second washing tank is connected to the inlet of a fifth centrifuge. The outlet of the fifth centrifuge is connected to the inlet of the second washing tank. The discharge end of the fifth centrifuge is connected to the inlet of a second drying device.

5. A coal chemical wastewater crystallized salt resource recovery system according to claim 1, characterized in that... The discharge end of the second freezing crystallization device is connected to the feed end of the sixth centrifuge, and the discharge end of the sixth centrifuge is connected to the feed end of the second evaporation crystallization system and the feed end of the third drying device.

6. A coal chemical wastewater crystallized salt resource recovery system according to claim 1, characterized in that... It also includes a water inlet tank, the inlet end of which is connected to the inlet pipe of high-salt wastewater from coal chemical industry, and the outlet end of which is connected to the inlet end of the pretreatment softening device.

7. A coal chemical wastewater crystallized salt resource recovery system according to claim 1, characterized in that... The sludge discharge end of the pretreatment softening device is connected to the feed end of the plate and frame filter press.

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