Oslo crystallizer system

Abstract

The utility model discloses an Oslo crystallizer system which comprises a water inlet tank, the water inlet tank is sequentially connected with a first-stage heat exchanger, a second-stage heat exchanger and an Oslo crystallizer, the Oslo crystallizer is further respectively connected with a settler and a centrifugal machine, the settler is connected with the second-stage heat exchanger through a supernatant circulating pipeline, and the centrifugal machine is connected with the second-stage heat exchanger through a centrifugal machine. The second-stage heat exchanger is further provided with a supernate outlet, the centrifugal machine is further connected with the Oslo crystallizer through a filtrate circulating pipeline, and the centrifugal machine is further provided with a solid discharge port; and the top of the Oslo crystallizer is connected with a steam pipeline through a heat pump. The Oslo crystallizer system can solve the problem that salt separation is not thorough due to factors such as performance attenuation of a nanofiltration unit membrane element and the recovery rate in nanofiltration salt separation.

Description

Technical Field

[0001] This utility model belongs to the field of zero discharge technology for coal chemical wastewater, and specifically relates to an Oslo crystallizer system. Background Technology

[0002] Coal chemical industry holds significant strategic importance for my country's energy structure and security. However, with its rapid development in recent years, water resource and environmental issues have become increasingly prominent, necessitating "zero discharge" of wastewater from coal chemical projects to achieve water conservation and cleaner production. This is also the inevitable solution to the aforementioned contradictions. The saline wastewater from coal chemical projects mainly originates from syngas washing wastewater, circulating system drainage, desalination system drainage, and concentrated water from the reuse system. After further concentration and reuse, the remaining concentrated water has a salt content of no less than 1%, and is referred to as concentrated brine. Due to the high salt concentration, it inhibits and toxicizes microorganisms, making it difficult to achieve "zero discharge" of high-concentration brine through biochemical methods.

[0003] Highly concentrated brine contains a large amount of soluble inorganic salts, such as Cl. - SO4 2- Na + Ca 2+ In order to stabilize, render harmless, and utilize crystalline salts, plasma treatment is required to separate the salts.

[0004] Currently, among the methods for separating salts in high-concentration brine, one approach is to use high-pressure nanofiltration membranes, but the separation efficiency decreases as membrane performance and recovery rate decline. Another approach utilizes high- and low-temperature evaporation and crystallization to separate Na₂SO₄ and NaCl crystals; this method has lower investment costs, but the product quality is significantly affected by the incoming water and requires a high salt / nitrate ratio.

[0005] Besides the two methods mentioned above, a cold salt separation process is also used, which involves cooling and crystallizing to obtain sodium sulfate crystals, and then further evaporating sodium chloride crystals from the mother liquor. The cold salt separation process has a short flow rate, strong resistance to fluctuations in salt content in upstream water, high purity of the crystallized salt, and the low temperature helps reduce corrosion of the equipment. However, in existing cold salt separation technologies, the external circulation refrigeration pipes are prone to clogging, resulting in poor refrigeration performance, affecting the salt separation effect, and hindering efficient, long-term, and stable operation. Utility Model Content

[0006] To address the shortcomings of existing technologies, this invention provides an Oslo crystallizer system that avoids the impact of membrane performance and recovery rate on salt separation during nanofiltration.

[0007] An Oslo crystallizer system includes an inlet tank, which is sequentially connected to a primary heat exchanger, a secondary heat exchanger, and an Oslo crystallizer. The Oslo crystallizer is also connected to a settling tank and a centrifuge. The settling tank is connected to the secondary heat exchanger via a supernatant circulation pipeline, and the secondary heat exchanger is also provided with a supernatant outlet. The centrifuge is also connected to the Oslo crystallizer via a filtrate circulation pipeline, and the centrifuge is also provided with a solid discharge outlet. The top of the Oslo crystallizer is connected to a steam pipeline via a heat pump.

[0008] Preferably, the heat pump is also connected to a mixing condenser, which is sequentially connected to a liquid seal tank and a refrigeration unit, and the refrigeration unit is also connected to the mixing condenser through an internal circulation pipeline.

[0009] Preferably, the Oslo crystallizer is a cooled Oslo crystallizer.

[0010] Preferably, both the primary heat exchanger and the secondary heat exchanger are plate heat exchangers.

[0011] Preferably, the refrigeration unit contains a refrigerant. More preferably, the refrigerant is tetrafluoroethane.

[0012] A freeze crystallization process, using the above system, includes the following steps:

[0013] (a) The high-salt concentrated water enters the inlet tank, is pumped to the first-stage heat exchanger for pre-cooling, and then enters the second-stage heat exchanger for pre-cooling;

[0014] (ii) After precooling, the steam enters the Oslo crystallizer. The steam from the steam pipeline provides power to the heat pump, which carries away the heat from the Oslo crystallizer and lowers the temperature of the Oslo crystallizer to 0-10℃, causing crystals to precipitate in the Oslo crystallizer.

[0015] (III) The crystals precipitated from the Oslo crystallizer are pumped to a centrifuge, where solid-liquid separation is achieved. The filtrate obtained from the separation is returned to the Oslo crystallizer through the filtrate circulation pipeline for secondary freeze crystallization. The solid sodium sulfate obtained from the separation is discharged from the solid outlet. The sodium sulfate is melted by hot melting and then evaporated and crystallized using a Na2SO4 evaporator crystallizer. The precipitated solid is centrifuged and dried to obtain solid Na2SO4. The mother liquor obtained from the evaporation crystallization and the liquid obtained from the centrifugation are returned to the evaporation crystallizer, hot melting and Oslo crystallizer for circulation.

[0016] (iv) The supernatant in the Oslo crystallizer is pumped to the settling tank for secondary settling. The supernatant after settling enters the secondary heat exchanger through the supernatant circulation pipeline to pre-cool the feed to the secondary heat exchanger. Then it is discharged from the supernatant outlet and collected. After pre-cooling, it is evaporated and crystallized in a NaCl crystallizer until a solid is precipitated. Then it is centrifuged and dried to obtain solid NaCl. The mother liquor produced by evaporation and crystallization is divided into two paths. One path is returned to the Oslo crystallizer to provide salt-nitrate balance, and the other path is sent to the mixed salt crystallization system to ensure the purity and whiteness of sodium chloride.

[0017] Preferably, the heat pump is also connected to a mixing condenser, which is sequentially connected to a liquid seal tank and a refrigeration unit, and the refrigeration unit is also connected to the mixing condenser through an internal circulation pipeline.

[0018] Preferably, in step (ii), the heat pump carries away the heat from the Oslo crystallizer, which enters the mixing condenser and is cooled to 20-30°C. The heat then enters the liquid seal tank and is pumped to the refrigeration unit to be cooled to 0°C. Finally, the heat is returned to the mixing condenser through the internal circulation pipeline.

[0019] Preferably, the Na2SO4 evaporator crystallizer is a single-effect evaporator crystallizer, and the NaCl crystallizer is a forced circulation evaporator crystallizer.

[0020] Preferably, the high-concentration brine has a TDS of 15%-17%, total hardness ≤1mg / L, COD ≤400mg / L, and silicon content ≤200mg / L.

[0021] Advantages of this utility model:

[0022] (1) The Oslo crystallizer system provided by this utility model can solve the problem of incomplete salt separation caused by factors such as the degradation of the performance of the nanofiltration unit membrane element and the recovery rate in nanofiltration salt separation. It can be widely used in the field of coal chemical wastewater treatment, chemical industry and other fields for the separation of monovalent salts and divalent salts. It has the characteristics of convenient operation, high automation efficiency, versatility and reliability, and has considerable applicability and practical application value.

[0023] (2) The Oslo crystallizer system provided by this utility model is used in the freeze crystallization process. It has high salt separation efficiency and can avoid the effects of poor freezing effect and incomplete salt separation caused by blockage of the external circulation freezing pipe in the traditional nanofiltration + external circulation pipe freezing process. Attached Figure Description

[0024] Figure 1 A schematic diagram of the Oslo crystallizer system described in this utility model;

[0025] Among them, 1-inlet tank, 2-primary heat exchanger, 3-secondary heat exchanger, 4-Oslo crystallizer, 5-sedimentation tank, 6-centrifuge, 7-mixing condenser, 8-liquid seal tank, 9-refrigeration unit. Detailed Implementation

[0026] Example 1

[0027] An Oslo crystallizer system includes an inlet tank 1, which is sequentially connected to a primary heat exchanger 2, a secondary heat exchanger 3, and an Oslo crystallizer 4. The Oslo crystallizer 4 is also connected to a settling tank 5 and a centrifuge 6. The settling tank 5 is connected to the secondary heat exchanger 3 via a supernatant circulation pipeline, and the secondary heat exchanger 3 is also provided with a supernatant outlet. The centrifuge 6 is also connected to the Oslo crystallizer 4 via a filtrate circulation pipeline, and the centrifuge 6 is also provided with a solid discharge outlet. The top of the Oslo crystallizer 4 is connected to a steam pipeline via a heat pump.

[0028] Preferably, the Oslo crystallizer 4 is a cooled Oslo crystallizer.

[0029] Preferably, both the primary heat exchanger 2 and the secondary heat exchanger 3 are plate heat exchangers.

[0030] The Oslo crystallizer system can achieve preliminary separation of monovalent and divalent salts from the high-concentration brine generated by zero discharge, as detailed below:

[0031] (1) The high-salt concentrated water enters the inlet tank 1. Since the water temperature is high, reaching 80-90℃, it is pumped to the first-stage heat exchanger 2 for pre-cooling (the first-stage heat exchanger uses circulating water for cooling), and then enters the second-stage heat exchanger 3 for pre-cooling (the second-stage heat exchanger uses the supernatant discharged from the Oslo crystallizer for cooling).

[0032] (2) After precooling, the steam enters the Oslo crystallizer 4. The steam from the steam pipeline provides power to the heat pump, which takes away the heat of the Oslo crystallizer 4 and lowers the temperature of the Oslo crystallizer 4 to 0-10℃, and crystals precipitate in the Oslo crystallizer 4.

[0033] (3) The crystals precipitated in Oslo crystallizer 4 are pumped to centrifuge 6. After centrifugation, solid-liquid separation is achieved. The filtrate obtained by separation is returned to Oslo crystallizer 4 through the filtrate circulation pipeline for secondary freeze crystallization. The solid sodium sulfate obtained by separation is discharged from the solid discharge port for later use.

[0034] (4) The supernatant in the Oslo crystallizer 4 is pumped to the settling tank 5 for secondary settling to ensure that no crystals precipitate in the supernatant after settling. The supernatant after settling enters the secondary heat exchanger 3 through the supernatant circulation pipeline to pre-cool the feed of the secondary heat exchanger 3, and then is discharged from the supernatant outlet for later use.

[0035] It can be seen that the Oslo crystallizer system can achieve preliminary separation of Na2SO4 and NaCl in high-salt concentrated water; the solid sodium sulfate discharged from the solid outlet in step (3) can be further processed to obtain Na2SO4; in step (4), the supernatant discharged from the supernatant outlet mainly contains NaCl, which can be further evaporated and crystallized to obtain solid NaCl, thereby achieving the separation of Na2SO4 and NaCl.

[0036] Example 2

[0037] Based on the above embodiment 1, the heat pump is also connected to a mixing condenser 7, which is sequentially connected to a liquid seal tank 8 and a refrigeration unit 9. The refrigeration unit 9 is also connected to the mixing condenser 7 through an internal circulation pipeline.

[0038] The heat pump carries away the heat from the Oslo crystallizer 4 and into the mixing condenser 7, where it is cooled to 20-30°C. The heat then enters the liquid seal tank 8 and is pumped to the refrigeration unit 9 to be cooled to 0°C. Finally, it returns to the mixing condenser 7 through the internal circulation pipeline, and the cycle repeats.

[0039] Preferably, the refrigeration unit 9 is provided with a refrigerant. More preferably, the refrigerant is tetrafluoroethane.

[0040] Example 3

[0041] A freeze crystallization process, using the system described in Example 1 above, includes the following steps:

[0042] (1) The high-salt concentrated water enters the inlet tank 1. Since the water temperature is high, reaching 80-90℃, it is pumped to the first-stage heat exchanger 2 for pre-cooling, and then enters the second-stage heat exchanger 3 for pre-cooling.

[0043] (2) After precooling, the steam enters the Oslo crystallizer 4. The steam from the steam pipeline provides power to the heat pump, which takes away the heat of the Oslo crystallizer 4 and lowers the temperature of the Oslo crystallizer 4 to 0-10℃, and crystals precipitate in the Oslo crystallizer 4.

[0044] (3) The crystals precipitated in the Oslo crystallizer 4 are pumped to the centrifuge 6. After centrifugation, solid-liquid separation is achieved. The filtrate obtained by separation is returned to the Oslo crystallizer 4 through the filtrate circulation pipeline for secondary freeze crystallization. The solid sodium sulfate obtained by separation is discharged from the solid discharge port. After hot melting, the sodium sulfate is melted and then evaporated and crystallized using the Na2SO4 evaporator crystallizer. The precipitated solid is centrifuged and dried to obtain solid Na2SO4. The mother liquor obtained from the evaporation crystallization and the liquid obtained from the centrifugation are returned to the evaporation crystallizer, hot melting and Oslo crystallizer 4 for circulation.

[0045] (4) The supernatant in the Oslo crystallizer 4 is pumped to the settling tank 5 for secondary settling. The supernatant after settling enters the secondary heat exchanger 3 through the supernatant circulation pipeline to pre-cool the feed of the secondary heat exchanger 3. Then it is discharged from the supernatant outlet and collected into the NaCl buffer tank. After pre-cooling, it is evaporated and crystallized in the NaCl crystallizer until solid is precipitated. Then it is centrifuged and dried to obtain solid NaCl. The mother liquor produced by evaporation and crystallization is divided into two paths. One path is returned to the Oslo crystallizer 4 to provide salt-nitrate balance, and the other path is sent to the mixed salt crystallization system to ensure the purity and whiteness of sodium chloride.

[0046] Preferably, the Na2SO4 evaporator crystallizer is a single-effect evaporator crystallizer, and the NaCl crystallizer is a forced circulation evaporator crystallizer.

[0047] Preferably, the high-concentration brine has a TDS of 15%-17%, total hardness ≤1mg / L, COD ≤400mg / L, and silicon content ≤200mg / L.

[0048] Example 4

[0049] Based on Embodiment 3 above, the heat pump is further connected to a mixing condenser 7. The mixing condenser 7 is sequentially connected to a liquid seal tank 8 and a refrigeration unit 9. The refrigeration unit 9 is also connected to the mixing condenser 7 via an internal circulation pipeline. The heat pump carries away the heat from the Oslo crystallizer 4, which enters the mixing condenser 7, is cooled to 20-30°C, enters the liquid seal tank 8, and is then pumped to the refrigeration unit 9 to be cooled to 0°C. Finally, it returns to the mixing condenser 7 via the internal circulation pipeline.

Claims

1. An Oslo crystallizer system comprising a water inlet tank (1), characterized in that: The water inlet tank (1) is connected with a first heat exchanger (2), a second heat exchanger (3) and an Oslo crystallizer (4) in sequence, the Oslo crystallizer (4) is further connected with a settler (5) and a centrifugal machine (6) respectively, the settler (5) is connected with the second heat exchanger (3) through a supernatant circulating pipeline, the second heat exchanger (3) is further provided with a supernatant outlet, the centrifugal machine (6) is further connected with the Oslo crystallizer (4) through a filtrate circulating pipeline, and the centrifugal machine (6) is further provided with a solid discharge outlet; the top of the Oslo crystallizer (4) is connected with a steam pipeline through a heat pump.

2. The Oslo crystallizer system of claim 1, wherein: The heat pump is further connected with a mixed condenser (7), the mixed condenser (7) is connected with a liquid seal groove (8) and a refrigeration unit (9) in sequence, and the refrigeration unit (9) is further connected with the mixed condenser (7) through an internal circulating pipeline.

3. The Oslo crystallizer system according to claim 1 or 2, characterized in that: The Oslo crystallizer (4) is a cooling type Oslo crystallizer.

4. The Oslo crystallizer system of claim 3, wherein: The first heat exchanger (2) and the second heat exchanger (3) are both plate type heat exchangers.

5. The Oslo crystallizer system of claim 2, wherein: A refrigerant is arranged in the refrigeration unit (9).

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