A method for drying a mixed salt mother liquor

Abstract

The application provides a kind of miscellaneous salt mother liquor dry treatment method, according to the following steps: S101. The miscellaneous salt mother liquor is preheated and transported to the thin film evaporator, and the steam and viscous mother liquor are obtained after being distributed and forced to form film by the thin film evaporator;S201. The viscous mother liquor obtained in S101 is subjected to solid-liquid separation by a separation device to obtain miscellaneous salt solid and centrifugal mother liquor;S202. The steam obtained in S101 is condensed to obtain condensed water, and the condensed water is transported to a rectifying column for rectification to obtain column still liquid and steam containing organic matter, and the column still liquid is discharged and collected;S301. The centrifugal mother liquor obtained in S201 is transported to a tail liquid drying device for drying treatment;S302. The steam containing organic matter obtained in S202 is condensed to obtain an organic solution, and the organic solution is transported back to the rectifying column for continuous rectification and / or discharged for collection. The miscellaneous salt mother liquor dry treatment method provided by the application has a wide application range, does not require the addition of chemical agents during operation, has low operating cost and can be operated stably for a long period of time.

Description

TECHNICAL FIELD

[0001] The present application mainly relates to the field of wastewater treatment, in particular to a method for drying treatment of mixed salt mother liquor. BACKGROUND

[0002] In recent years, in order to survive and long-term development of enterprises, the wastewater discharged in the production process of enterprises in the fields of coal chemical industry, petroleum chemical industry, fine chemical industry, metallurgy, pharmaceutical industry, printing and dyeing, papermaking and the like adopts a "zero discharge" water treatment process. The "zero discharge" water treatment process mainly includes three main treatment procedures of pretreatment, advanced treatment and concentrated water evaporation crystallization. The commonly used treatment process for concentrated water evaporation crystallization is three-effect evaporation crystallization and MVR evaporation crystallization. Regardless of the three-effect evaporation crystallization or the MVR evaporation crystallization process, when sodium chloride or sodium sulfate crystalline salt products meeting the requirements are produced, a certain amount of mixed salt mother liquor will be discharged. The mother liquor has the characteristics of high salt and high COD, usually contains more than 100000 mg / L of salt and more than 10000 mg / L of COD, and is also mixed with solid particles of sodium chloride or sodium sulfate crystalline salt.

[0003] At present, the commonly used treatment method for the mixed salt mother liquor is to use a single drying equipment for drying treatment, such as a roller drying, a spray drying, a rake drying, a microwave drying and a single cone drying equipment. The single drying equipment has the advantages of being able to completely realize drying treatment of the mixed salt mother liquor and truly realizing "zero discharge" of the end treatment of wastewater, but the biggest disadvantage is that the treatment capacity of the mixed salt mother liquor is small (the water quantity is generally not more than 1 m 3 / h), and the COD adaptation range is narrow (only applicable to the mixed salt mother liquor containing difficult volatile COD components). In the "zero discharge" process of water treatment in various industries, especially in petrochemical enterprises, the amount of the mixed salt mother liquor generated is as high as 5 m 3 / h, and the COD in the mother liquor is mostly volatile components. The conventional single drying equipment cannot economically and effectively realize drying of the mixed salt mother liquor. Therefore, it is of important application value to invent a process and method capable of treating a large water quantity, having a wide COD adaptation range, being economical and easy to operate, and realizing drying of the mixed salt mother liquor generated in the "zero discharge" process of water treatment in various industries.

[0004] Therefore, the present application is proposed. SUMMARY

[0005] The present application aims to provide a method for drying treatment of mixed salt mother liquor, which can quickly and efficiently treat high-salt and high-COD mixed salt mother liquor.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0007] The present application provides a method for drying treatment of mixed salt mother liquor, characterized by the following steps:

[0008] S101. The preheated mother liquor of mixed salt is sent to a thin film evaporator, and after distribution and forced film formation in the thin film evaporator, evaporation is carried out to obtain steam and viscous mother liquor;

[0009] S201. The viscous mother liquor obtained in S101 is subjected to solid-liquid separation by a separation device to obtain mixed salt solid and centrifugal mother liquor;

[0010] S202. The steam obtained in S101 is condensed to obtain condensed water, and the condensed water is sent to a rectifying column for rectification to obtain column still liquid and steam containing organic matter, and the column still liquid is discharged and collected;

[0011] S301. The centrifugal mother liquor obtained in S201 is sent to a tail liquid drying device for drying treatment;

[0012] S302. The steam containing organic matter obtained in S202 is condensed to obtain an organic solution, and the organic solution is sent back to the rectifying column for continuous rectification and / or discharged for collection.

[0013] Preferably or optionally, the temperature of the preheating of the mixed salt mother liquor in step S101 is 60-65℃.

[0014] Preferably or optionally, the thin film evaporator in step S101 is a scraper thin film evaporator.

[0015] Preferably or optionally, the operating temperature of the scraper thin film evaporator is 80-110℃, and the pressure is -85-0KPa.

[0016] Preferably or optionally, the scraper thin film evaporator is a two-stage scraper thin film evaporator.

[0017] Preferably or optionally, the separation device in S201 is a centrifugal separation device.

[0018] Preferably or optionally, the temperature of the condensed water in the rectifying column in S202 is 60-100℃, the operating pressure of the rectifying column is -85.0-0.0KPa, and the separation efficiency of the rectifying column is ≥90%.

[0019] Preferably or optionally, the tail liquid drying device in S301 is one or a combination of a drum drying device, a spray drying device, a rake drying device, a microwave drying device, and a single-cone drying device.

[0020] Beneficial effects

[0021] The method for drying the mixed salt mother liquor provided by the application solves the drying problem of the mixed salt mother liquor produced by the evaporation crystallization device of the water treatment zero discharge process, is not limited by the water amount, the volatile or non-volatile of the COD component, the salt content and the like, has a wide application range, does not add chemical agents during operation, has high mass transfer and heat transfer efficiency, low operation cost, small equipment investment and long-term stable operation. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The figure is a schematic diagram of the mixed salt mother liquor drying treatment system described in Example 2. DETAILED DESCRIPTION

[0023] In order to facilitate the understanding of the application, the application will be described more fully below with reference to the accompanying drawings and preferred experimental examples, but the scope of protection of the application is not limited to the following specific examples.

[0024] Unless otherwise defined, all the professional terms used below have the same meaning as understood by those skilled in the art. The professional terms used in the present application are only for the purpose of describing the specific examples and are not intended to limit the scope of protection of the application.

[0025] Example 1

[0026] The application provides a method for drying the mixed salt mother liquor.

[0027] The method for drying the mixed salt mother liquor is performed according to the following steps:

[0028] First, the mixed salt mother liquor is preheated and then sent to a thin film evaporator, evaporated after distribution and forced film formation, to obtain steam and viscous mother liquor.

[0029] The steam is condensed by a condensing device to obtain condensed water, and the condensed water is sent to a rectifying column for rectification to obtain column still liquid and steam containing organic matter. After the steam containing organic matter is condensed again, the organic solution obtained by condensation is selected to be refluxed and rectified again or discharged and collected for centralized treatment.

[0030] The column still liquid produced after rectification contains a small amount of difficult-to-volatile organic components, so the column still liquid is discharged and collected for subsequent separate treatment.

[0031] As a feasible treatment method, the column still liquid can be sent to a biochemical pool for biochemical treatment to remove part of the organic matter, and then subjected to sludge settlement, addition of coagulant precipitation, oxidation treatment to reduce turbidity and organic matter content, and ultrafiltration and reverse osmosis treatment to obtain reverse osmosis produced water with water quality meeting the water quality requirements of recycled water.

[0032] It should be noted that the present application does not make specific limitations on the processing mode of the tower kettle liquid, and those skilled in the art can select a suitable processing mode of the tower kettle liquid according to actual needs.

[0033] The viscous mother liquor is subjected to solid-liquid separation in the centrifugal separation device, and the separated impurity salt solid can be directly packaged and transported out for harmless treatment, and the centrifugal mother liquor generated after separation is transported to the tail liquid mother liquor tank for centralized collection and transported to the tail liquid drying device for drying treatment.

[0034] For the drying treatment of the centrifugal mother liquor, one or a combination of a roller drying device, a spray drying device, a rake drying device, a microwave drying device, and a single-cone drying device is selected, and the impurity salt solid generated after drying of the centrifugal mother liquor is also packaged and transported out for harmless treatment.

[0035] The impurity salt mother liquor drying treatment method provided in the embodiment realizes efficient treatment of the impurity salt mother liquor through evaporation, solid-liquid separation, and drying, and rectification, is not limited by conditions such as the amount of water in the impurity salt mother liquor, whether the COD component is volatile or not, and the salt content, has a wide application range, and does not require additional chemical agents during operation, thereby further reducing the operation cost on the premise of ensuring long-term stable operation.

[0036] Embodiment two

[0037] The embodiment of the present application provides an impurity salt mother liquor drying treatment method based on specific equipment and systems, as shown in the figure, the set of impurity salt mother liquor drying treatment system is connected with the boundary impurity salt mother liquor outlet, and comprises at least one scraper film evaporator, a separation device, a first condenser, a second condenser, a rectification device, a vacuum device, and a tail liquid drying device. Figure 1

[0038] The impurity salt mother liquor generated by the boundary is pumped and preheated in the heat exchanger of the rectification tower kettle of the rectification device, and then introduced into the scraper film evaporator after preheating.

[0039] In the embodiment, the scraper film evaporator is a two-stage scraper film evaporator, and the number of stages used can be determined by those skilled in the art according to the amount of water in the impurity salt mother liquor to be treated in the actual process.

[0040] The impurity salt mother liquor is uniformly distributed on the heating surface of the scraper film evaporator to form a liquid film, which is evaporated by heating to generate steam and viscous mother liquor mixed with crystalline salt particles, and the viscous mother liquor is collected by the mother liquor tank and then transported into the centrifugal separation device.

[0041] In the embodiment, the scraper film evaporator is heated by using the live steam introduced by the boundary.

[0042] ​The separation device separates the viscous mother liquor in a centrifugal manner, and the separated impurity salt solid is directly packaged and then transported out for harmless treatment, and the separated centrifugal mother liquor is collected in a tail liquid mother liquor tank (not shown in the figure) and then transported to a tail liquid drying device.

[0043] The centrifugal mother liquor is completely dried in the tail liquid drying device, and the generated impurity salt solid is packaged and then transported out for harmless treatment. In this embodiment, the tail liquid drying device is one or a combination of a roller drying device, a spray drying device, a rake drying device, a microwave drying device, and a single-cone drying device.

[0044] The steam generated by the scraped-film evaporator is condensed by the first condenser to obtain condensed water, and the condensed water is transported to the rectifying tower for rectification to remove organic matter. The condensed water exchanges liquid and vapor through the tower plate in the middle part of the rectifying tower, and the volatile organic matter is separated from the water. The volatile organic matter moves upward in the rectifying tower, collects at the top of the tower, and is condensed into an organic solution rich in volatile organic matter components by the second condenser. The organic solution is pumped back to the rectifying tower and mixed with the condensed water for rectification again, or a small amount of organic solution is cooled and transported to a storage tank for centralized treatment.

[0045] The remaining water and non-volatile organic matter in the rectifying tower move downward, collect at the bottom of the rectifying tower, and are cooled by the heat exchanger (synchronously preheating the wastewater) of the tower kettle, and then discharged for subsequent treatment.

[0046] As a feasible treatment method, the tower kettle liquid can be transported to a biochemical pool for biochemical treatment to remove part of the organic matter, and then subjected to sludge settlement, addition of coagulant precipitation, oxidation treatment to reduce turbidity and organic matter content, and ultrafiltration and reverse osmosis treatment to obtain reverse osmosis produced water with water quality meeting the water quality requirements of recycled water.

[0047] However, it should be noted that the treatment method of the tower kettle liquid is not specifically limited, and those skilled in the art can select a suitable treatment method of the tower kettle liquid according to actual needs.

[0048] The vacuum device is used to extract non-condensable gas from the scraped-film evaporator, the first condenser, the second condenser, and the rectifying device. In this embodiment, the non-condensable gas pipelines of the above-mentioned three devices are communicated to form a non-condensable gas pipeline system.

[0049] Example Three

[0050] The impurity salt mother liquor drying treatment system and method provided in Example Two will be described in detail below in combination with specific process parameters.

[0051] In this embodiment, the salt content of the impurity salt mother liquor is ≥100,000 mg / L, and the COD concentration is ≥10,000 mg / L.

[0052] The mixed salt mother liquor from the boundary zone is pumped into the heat exchanger of the distillation column tower bottom of the rectification device for preheating, and after preheating to 60-65℃, it is introduced into the two-stage scraped film evaporator.

[0053] The mixed salt mother liquor is distributed and forced to form a film in the scraped film evaporator, and the steam generated by evaporation is condensed into condensed water by the first condenser and introduced into the distillation column for distillation to remove organic matter.

[0054] In this embodiment, the scraped film evaporator is also provided with an external vapor-liquid separator, which can effectively separate the liquid droplets contained in the steam generated by the scraped film evaporator, prevent vapor-liquid entrainment, and improve the processing efficiency of the evaporator.

[0055] In this embodiment, the operating temperature of the scraped film evaporator is 80-110℃, and the operating pressure (gauge pressure) is -85.0-0.0KPa.

[0056] The condensed water exchanges vapor and liquid through the tray in the middle of the distillation column to separate the volatile organic matter and water, the volatile organic matter moves upward in the distillation column to form steam containing organic matter and collects at the top, and is condensed into an organic solution rich in volatile organic matter components by the second condenser. The organic solution is pumped back to the distillation column for rectification again, or a small amount of organic solution is cooled and discharged for collection and centralized harmless treatment.

[0057] In this embodiment, the operating temperature of the distillation column is 60-100℃, the operating pressure (gauge pressure) is -85.0-0.0kPa, and the separation efficiency of the distillation column is ≥90%.

[0058] The remaining water and a small amount of difficult-to-volatile organic matter in the distillation column move downward and accumulate at the bottom of the distillation column to form a tower bottom liquid, which is cooled by the heat exchanger of the distillation column tower bottom (simultaneously preheating the wastewater) and discharged for subsequent treatment.

[0059] At this time, the water quality of the tower bottom liquid is ≤1000mg / L in salt content and ≤1000mg / L in COD concentration.

[0060] The viscous mother liquor with precipitated crystalline salt particles remaining after evaporation in the scraped film evaporator is first transported to the mother liquor tank for centralized collection, and then transported to the centrifugal separation device for solid-liquid separation treatment.

[0061] The centrifugal separation device separates the viscous mother liquor by centrifugation, and the separated mixed salt solid is directly packaged and shipped for harmless treatment, and the separated centrifugal mother liquor is collected in the tail liquid mother liquor tank and transported to the tail liquid drying device.

[0062] In the embodiment, the mother liquor tank is a jacketed tank, and low-pressure saturated steam at 140-160 DEG C can be introduced into the jacket to further concentrate the viscous mother liquor, or circulating cooling water can be introduced to cool the mother liquor, when the circulating cooling water is introduced, the temperature of the water introduced is controlled to be 32 DEG C, and the temperature of the returned water is controlled to be 42 DEG C.

[0063] The centrifugal mother liquor is completely dried in a tail liquid drying device, and the produced salt solid is packaged and transported out for harmless treatment. In the embodiment, the tail liquid drying device is one or a combination of a roller drying device, a spray drying device, a rake drying device, a microwave drying device and a single-cone drying device.

[0064] The vacuum device is used to extract the non-condensable gas in the scraped thin film evaporator, the first condenser, the second condenser and the rectifying device, in the embodiment, the primary scraped thin film evaporator and the secondary scraped thin film evaporator are connected with the steam pipeline of the first condenser, the non-condensable gas pipeline of the first condenser is connected with the secondary steam pipeline of the second condenser, the secondary steam pipeline of the second condenser is connected with the rectifying tower, and the non-condensable gas pipeline of the second condenser is connected with the vacuum device, thereby forming a non-condensable gas pipeline system.

[0065] The mother liquor drying treatment method of the salt provided by the application solves the drying problem of the salt mother liquor produced by the evaporation crystallization device of the water treatment "zero discharge" process, is not limited by the water amount, the volatility of the COD component, the salt content and other conditions, has a wide application range, and does not add chemical agents during operation, has low operation cost and can be stably operated for a long time.

[0066] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the application, and not to limit them; although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the application.

Claims

1. A method for dry treatment of a mixed salt mother liquor, characterized in that, The following steps are taken: S101. The impure salt mother liquor from the boundary zone is pumped into the heat exchanger of the rectification tower of the rectification device for preheating and then into the two-stage scraped film evaporator, and after distribution and forced film formation by the two-stage scraped film evaporator, evaporation is carried out to obtain steam and viscous mother liquor; The scraped film evaporator is also provided with an external vapor-liquid separator, which can effectively separate the liquid droplets contained in the steam generated by the scraped film evaporator, prevent vapor-liquid entrainment, and improve the processing efficiency of the evaporator; S201. The viscous mother liquor obtained in S101 is first transported to the mother liquor tank for centralized collection, and then subjected to solid-liquid separation by a centrifugal separation device to obtain impure salt solids and centrifugal mother liquor. The impure salt solids are directly packaged and then shipped for harmless treatment; The mother liquor tank is a jacketed tank, and low-pressure saturated steam at 140-160℃ is introduced into the jacket to further concentrate the viscous mother liquor, or circulating cooling water is introduced for cooling. When circulating cooling water is introduced, the temperature of the incoming water is controlled at 32℃, and the temperature of the return water is controlled at 42℃; S202. The steam obtained after vapor-liquid separation in S101 is condensed by a first condenser to obtain condensed water, which is then transported to the rectification tower for rectification to obtain tower bottom liquid and steam containing organic matter. The tower bottom liquid is discharged and collected; S301. The centrifugal mother liquor obtained in S201 is collected in the tail liquid mother liquor tank and then transported to a tail liquid drying device for drying treatment; The tail liquid drying device is a combination of one or more of a drum drying device, a spray drying device, a rake drying device, a microwave drying device, and a single-cone drying device; S302. The steam containing organic matter obtained in S202 is condensed by a second condenser to obtain an organic solution, which is transported back into the rectification tower to mix with the condensed water and then rectified again; The remaining water and difficult-to-vaporize organic matter in the rectification tower flows downward and accumulates at the bottom of the rectification tower to form tower bottom liquid, which is cooled by the heat exchanger of the rectification tower and then discharged for subsequent treatment. The heat exchanger simultaneously preheats the wastewater. The water quality of the tower bottom liquid has a salt content of ≤1000 mg / L and a COD concentration of ≤1000 mg / L.

2. The method of heterogeneous salt liquor dewatering according to claim 1, wherein, The preheating temperature of the impure salt mother liquor in step S101 is 60-65℃.

3. The method of heterogeneous salt liquor dewatering according to claim 1, wherein, The operating temperature of the scraped film evaporator is 80-110℃, and the pressure is -85-0 kPa.

4. The method of heterogeneous salt liquor dewatering according to claim 1, wherein, In S202, the condensate is rectified in the rectification tower at a temperature of 60-100℃, the operating pressure of the rectification tower is -85.0-0.0 kPa, and the separation efficiency of the rectification tower is ≥90%.

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