Evaporating crystallizer for zero discharge and recycling of coal chemical industry wastewater

Abstract

The utility model relates to an evaporating crystallizer, which is used for zero discharge recycling of coal chemical industry wastewater and comprises a gasification separation chamber, a crystal growing chamber positioned below the gasification separation chamber, and a circulating pipe, a circulating pump and a heat exchanger which are connected in sequence, wherein a central downcomer is arranged at the bottom of the gasification separation chamber, a plurality of openings are formed in the top of the crystal growing chamber, and the crystal growing chamber comprises an upper part and a lower part; the central downcomer at least extends to a crystal mush area from an opening formed in the top of the crystal growing chamber, the central downcomer is composed of a main body section and a diffusion section with a trapezoidal longitudinal section, and the included angle between the side wall of the diffusion section and the vertical direction is 10-30 degrees; the circulating pipe is connected with another opening formed in the top of the crystal growing chamber, and a discharging opening of the heat exchanger is connected with a feeding opening of the gasification separation chamber. The included angle between the side wall of the diffusion section and the vertical direction is optimally designed, so that the energy loss can be reduced, the product granularity can be optimized, and the crystallization efficiency can be improved.

Description

Technical Field

[0001] This utility model belongs to the field of wastewater treatment technology, specifically relating to an evaporator crystallizer for zero-discharge resource utilization of coal chemical wastewater. Background Technology

[0002] Industrial production in coal mining and coal chemical industries generates saline wastewater containing large amounts of inorganic and organic impurities. Current technologies typically use crystallization systems including evaporators to further concentrate the saline wastewater and achieve zero discharge. However, the supersaturation of the circulating mother liquor in conventional evaporators is not fully utilized for crystal growth, resulting in a nucleation rate exceeding the crystal growth rate. This leads to the formation of numerous new crystal nuclei, resulting in a large number of fine crystals. Consequently, the obtained salt product has a small particle size, failing to meet the standards of downstream manufacturers. Furthermore, salt often accumulates at the bottom of the crystallizer, requiring regular cleaning and disrupting the continuous production of the entire crystallization system. Summary of the Invention

[0003] To address the shortcomings of the existing technology, the purpose of this utility model is to provide an evaporation crystallizer for zero-discharge resource utilization of coal chemical wastewater, which, compared with traditional crystallizers, features high output, optimized crystal size, and continuous production operation.

[0004] Specifically, the evaporator crystallizer of this utility model includes a vaporization separation chamber, a crystal growth chamber located below the vaporization separation chamber, and a circulation pipe, a circulation pump, and a heat exchanger connected in sequence.

[0005] The gasification separation chamber has a central downcomer at the bottom and a crystal growth chamber has multiple openings at the top. The crystal growth chamber includes an upper part and a lower part. The upper part is divided into a fine crystal zone and a first settling zone from top to bottom, and the lower part is divided into a second settling zone, a crystal slurry zone and a turbulence zone from top to bottom. The transverse cross-sectional area of ​​the upper part is larger than that of the lower part, and the transverse cross-sectional area of ​​the second settling zone is larger than that of the crystal slurry zone. The central downcomer extends from the opening at the top of the crystal growth chamber to at least the crystal slurry zone. The central downcomer consists of a main section and a diffusion section with a trapezoidal longitudinal section. The angle between the sidewall of the diffusion section and the vertical direction is 10°-30°.

[0006] The circulation pipe is connected to another opening located at the top of the crystallization chamber, and the outlet of the heat exchanger is connected to the inlet of the gasification separation chamber.

[0007] The structure of the above-mentioned evaporator crystallizer is as follows: Figure 1 As shown.

[0008] In this invention, the angle between the sidewall of the diffuser section of the central downcomer and the vertical direction is optimized, and the diameter of the diffuser section gradually increases along the direction of solution movement, which effectively enhances the turbulent mixing effect of the crystal slurry. Through sufficient contact between the solution and crystal particles, mass transfer efficiency is improved, while avoiding crystal accumulation and agglomeration during sedimentation, ensuring the uniformity and stability of crystal growth, thereby significantly improving the overall efficiency of the evaporation crystallization process and product quality.

[0009] The central downcomer can be made of materials such as stainless steel or titanium alloy, or it can be coated with a coating to resist corrosion and high temperature. In practice, it can be selected according to different chemical environments.

[0010] Preferably, the diameter of the central downcomer is 0.8-1.2m, and the total length is 4.0-5.0m, wherein the length of the diffusion section is 1.0-1.5 times the diameter of the central downcomer, and the main body section extends from the opening located at the center of the top of the crystallization chamber to the second settling zone, preferably the middle of the second settling zone. The above-mentioned diameter and length are designed according to the scale, throughput, and other process requirements of the evaporator crystallizer.

[0011] Preferably, the distance between the bottom of the central downcomer and the bottom of the crystallization chamber is 0.5-1.0 times the diameter of the central downcomer.

[0012] Preferably, the central downcomer extends from an opening located at the center of the top of the crystallization chamber to the turbulence zone. Below the bottom of the central downcomer is the turbulence zone of the crystallization chamber, where supersaturated solution is released, and the crystals gradually grow and settle.

[0013] Preferably, the top of the gasification separation chamber is provided with a steam outlet.

[0014] Preferably, the total volume of the crystal growth chamber is 8.0-35.0 m³. 3 .

[0015] Preferably, the upper part of the crystal growth chamber is cylindrical, with a transverse cross-sectional area of ​​6.00-8.00 m². 2 The longitudinal section of the second settling zone and the crystal slurry zone in the crystallization chamber is an inverted trapezoid, and the bottom area of ​​the crystal slurry zone is 2.00-3.00 m². 2 .

[0016] Preferably, the height of the fine crystal zone accounts for 30-50% of the total height of the crystal growth chamber, the height of the first settling zone accounts for 10-30% of the total height of the crystal growth chamber, the height of the second settling zone accounts for 10-20% of the total height of the crystal growth chamber, and the height of the crystal slurry zone accounts for 10-20% of the total height of the crystal growth chamber.

[0017] Preferably, the sidewalls of the second settling zone and the crystal slurry zone form an angle of 15°-25° with the vertical direction; and / or the height of the tumbling zone accounts for 5-15% of the total height of the crystal growth chamber, and the tumbling zone has an arc-shaped bottom surface, the transverse cross-sectional area of ​​which is smaller than that of the crystal slurry zone.

[0018] By employing the trapezoidal design of the central downcomer diffusion section, the inverted trapezoidal design of the second settling zone and crystal slurry zone in the crystallization chamber, and the arc-shaped bottom design of the turbulence zone, the flow rate of the crystal slurry (supersaturated solution) is controlled, causing the crystal slurry to turbulent and preventing it from settling and accumulating at the bottom. These designs result in crystals suspended in the feed liquid, forming a fluidized state with particle size classification. The upward flow velocity of the supersaturated solution gradually decreases, and the particle size of the suspended crystals decreases as it rises. When the solution reaches the upper layer of the crystallization chamber, only a fine-crystal solution remains, which serves as the mother liquor for circulation. This ensures that the circulating feed liquid does not explode and nucleate during flash evaporation in the vaporization separation chamber. Furthermore, the particle size classification effect of the crystallization chamber allows large crystal particles to settle and separate, resulting in a final product with large and uniform particle size.

[0019] Preferably, the crystal growth chamber has one or more discharge ports on its bottom and / or sidewall.

[0020] Preferably, the central downcomer is equipped with a temperature sensor and / or a pressure sensor. These monitoring devices are used to detect process parameters.

[0021] This invention achieves a particle size classification fluidized state for crystal particles during evaporation crystallization by setting a layered structure in the crystal growth chamber and combining the trapezoidal combination of the second settling zone and the crystal slurry zone within the chamber with the parameters of the central downcomer. By optimizing the design of the diffusion section of the central downcomer and the crystal growth chamber, the crystal slurry is kept in a turbulent state between the diffusion section and the bottom of the chamber, preventing crystal deposition and accumulation. This also promotes uniform suspension and growth of the crystals, ensuring that the supersaturated solution gradually desaturates during its ascent within the chamber. Ultimately, this achieves efficient fluidized classification of the crystal slurry and efficient production of crystal products with large and uniform particle sizes. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the evaporator crystallizer of this utility model;

[0023] Figure 2 This is a schematic diagram of the crystallization chamber and the central downcomer in a specific embodiment of this utility model. Detailed Implementation

[0024] The following specific embodiments illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. Although the description of this utility model will be presented in conjunction with preferred embodiments, this does not mean that the features of this utility model are limited to this embodiment. To provide a deep understanding of this utility model, many specific details will be included in the following description. This utility model may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of this utility model, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this utility model can be combined with each other.

[0025] It should be noted that in this specification, similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0026] In the description of this embodiment, it should be noted that the terms "upper", "lower", "inner", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the utility model product is usually placed in during use. They are only for the convenience of describing the utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the utility model.

[0027] In the description of this embodiment, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set up," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this embodiment based on the specific circumstances.

[0028] To make the objectives, technical solutions, and advantages of this utility model clearer, the embodiments of this utility model will be described in further detail below with reference to the accompanying drawings.

[0029] like Figure 1 As shown, the evaporator crystallizer of this utility model includes a vaporization separation chamber, a crystal growth chamber located below the vaporization separation chamber, and a circulation pipe, a circulation pump, and a heat exchanger connected in sequence.

[0030] The gasification separation chamber has a central downcomer at its bottom, and the crystallization chamber has multiple openings at its top. The crystallization chamber includes an upper part and a lower part. The upper part is divided into a fine crystal zone and a first settling zone from top to bottom, and the lower part is divided into a second settling zone, a crystal slurry zone, and a turbulence zone from top to bottom. The lateral cross-sectional area of ​​the upper part is larger than that of the lower part, and the lateral cross-sectional area of ​​the second settling zone is larger than that of the crystal slurry zone. In one embodiment, the central downcomer extends from the opening located in the center of the top of the crystallization chamber to the turbulence zone. The central downcomer consists of a main body section and a diffuser section with a trapezoidal longitudinal cross-section. The angle between the sidewall of the diffuser section and the vertical direction is 10°-30°. Of course, in other embodiments of this invention, the central downcomer can be set to extend from other positions on the top of the crystallization chamber to the turbulence zone, as long as the crystal slurry can be turbulent from the bottom of the central downcomer to the bottom of the crystallization chamber during use.

[0031] In this embodiment, the circulation pipe is connected to another opening located at the top of the crystallization chamber, and the outlet of the heat exchanger is connected to the inlet of the gasification separation chamber.

[0032] The central downcomer has a diameter of 0.9m and a total length of 4.5m. The diffusion section is 1.2 times the diameter of the central downcomer. The main body extends from the opening at the center of the top of the crystallization chamber to the second settling zone, and the entire central downcomer extends from the opening at the center of the top of the crystallization chamber to the turbulence zone. In this embodiment, the bottom and / or sidewall of the crystallization chamber has one or more discharge ports, and the top of the gasification separation chamber has a steam outlet. The central downcomer of the crystallizer is made of stainless steel and is used for evaporating and crystallizing coal chemical wastewater. Of course, in other embodiments of this invention, the central downcomer can also be made of titanium alloy or other materials, as long as they are corrosion-resistant and high-temperature resistant.

[0033] In operation, wastewater is added through the circulation pipe and mixed with the saturated solution overflowing from the crystallization chamber by the circulation pump. The mixture then flows through a steam-heated heat exchanger. The heated solution is pumped into the gasification separation chamber for flash evaporation. The steam generated after flash evaporation is discharged from the steam outlet at the top of the gasification separation chamber. The supersaturated solution after flash evaporation flows through the central downcomer to the bottom of the crystallization chamber and then flows upwards, passing through the crystals growing inside. Upon contact with these crystals, the supersaturated solution desaturates and becomes saturated. This saturated solution rises to the top of the crystallization chamber and mixes with the solution in the circulation pipe before circulating together. The resulting large and uniform crystals are discharged through the outlets at the bottom and / or sidewalls of the crystallization chamber. By adjusting the diameter parameters of the central downcomer, the lateral flow velocity of the supersaturated solution in the downcomer is controlled to be approximately 0.9 m / s, and the upward flow velocity of the solution in the settling zone is ≤0.1 m / s. The flow rate of the supersaturated solution moving upward in the crystallization chamber gradually decreases, and the particle size of the suspended crystals becomes smaller as they go upward, without disrupting the established sedimentation steady state. During this process, the supersaturated solution is gradually desaturated and used for crystal growth, becoming a saturated solution that participates in the mother liquor circulation.

[0034] Figure 2 The specific structure of the crystal growth chamber and the central downcomer is shown. In this embodiment, the angle between the sidewall of the diffuser section of the central downcomer and the vertical direction is approximately 20°, and the distance between the bottom of the central downcomer and the bottom of the crystal growth chamber is approximately one diameter of the central downcomer. The total height of the crystal growth chamber is 5.27 m, and the total volume is 30.5 m³. 3 The upper part of the crystal growth chamber is cylindrical, with a cross-sectional area of ​​7.07 m². 2 The longitudinal section of the second settling zone and the crystal slurry zone in the crystallization chamber is an inverted trapezoid, with the bottom area of ​​the crystal slurry zone being 2.54 m². 2 .

[0035] The height of the fine crystal zone accounts for 40% of the total height of the crystal growth chamber, the height of the first sedimentation zone accounts for 20% of the total height of the crystal growth chamber, the height of the second sedimentation zone accounts for 15% of the total height of the crystal growth chamber, and the height of the crystal slurry zone accounts for 15% of the total height of the crystal growth chamber.

[0036] The sidewalls of the second settling zone and the crystal slurry zone form an angle of approximately 20° with the vertical direction. In this embodiment, the sidewalls of the second settling zone and the crystal slurry zone preferably form the same angle with the vertical direction.

[0037] By controlling the above parameters, the flow velocity of the supersaturated solution between the diffusion section of the central downcomer and the bottom of the crystallization chamber is approximately 0.6 m / s, ensuring that the crystal slurry is in a fluidized and turbulent state and does not deposit.

[0038] In this embodiment, the height of the tumbling zone accounts for 10% of the total height of the crystal growth chamber, and the tumbling zone has an arc-shaped bottom surface, the cross-sectional area of ​​which is smaller than the cross-sectional area of ​​the crystal slurry zone.

[0039] The crystallization chamber has different diameters in different regions, with the fine-crystal zone having a larger cross-sectional area. The top of the crystallization chamber is the fine-crystal zone, which participates in the feed liquid circulation. Next is the settling zone (including the first and second settling zones), where crystals of various sizes settle and grow. Then comes the crystal slurry zone, where larger crystals accumulate. By controlling the size of the diffuser opening in the central downcomer, the inverted trapezoidal design of the second settling zone and the crystal slurry zone in the crystallization chamber, and the arc-shaped design at the bottom of the crystallization chamber, the flow velocity at the bottom of the feed liquid is controlled, causing the crystal slurry to churn and preventing it from settling and accumulating at the bottom. These designs allow the crystals to be suspended in the feed liquid, forming a fluidized state with particle size classification. The flow velocity of the supersaturated solution gradually decreases upwards, and the particle size of the suspended crystals decreases as they go up. When the solution reaches the fine-crystal zone of the crystallization chamber, only the fine-crystal solution remains, which serves as the mother liquor and enters the circulation. This ensures that the circulating feed liquid does not explode and nucleate during flash evaporation in the gasification separation chamber. In addition, the particle size classification effect of the crystallization chamber allows large crystals to settle and separate, resulting in a final product with large and uniform particle size.

[0040] In this embodiment, based on the sedimentation characteristics of crystal particles obtained from evaporation wastewater, the total height of the crystal growth chamber, the bottom area of ​​the fine crystal zone, the sedimentation zone (including the first sedimentation zone and the second sedimentation zone), and the crystal slurry zone, as well as the proportion of different zones to the total height of the crystal growth chamber, are designed so that the crystal slurry can achieve natural stratification in the crystal growth chamber, and large crystal particles can settle and grow.

[0041] Of course, in other embodiments of this invention, the angle between the sidewalls of the second settling zone and the crystal slurry zone and the vertical direction can vary between 15° and 20°, and the distance between the bottom of the central downcomer and the bottom of the crystallization chamber can vary between 0.5 and 1.0 times the diameter of the central downcomer. The specific values ​​are adjusted according to the content of various salt ions in the wastewater being treated and the required crystal particle size. Furthermore, in other embodiments of this invention, the central downcomer can also be equipped with a temperature sensor and / or a pressure sensor for monitoring the temperature and pressure of the supersaturated solution.

[0042] Compared with traditional crystallizers, the evaporator crystallizer of this invention features uniform particle size and high production capacity. Traditional crystallizers, when used for zero-discharge resource recovery of coal chemical wastewater, produce salt crystals with an average particle size below 0.1 mm. In contrast, the evaporator crystallizer of this invention produces salt particles with an average size of 0.25 mm, resulting in a more uniform and larger-sized product and significantly improved economic value.

[0043] The embodiments of this utility model have been described in detail above, but the content is only a preferred embodiment of this utility model and should not be considered as limiting the scope of implementation of this utility model. Any equivalent improvements made by those skilled in the art without departing from the scope of this utility model should still fall within the patent coverage of this utility model.

Claims

1. An evaporator crystallizer for zero-discharge resource utilization of coal chemical wastewater, characterized in that, The evaporator crystallizer includes a vaporization separation chamber, a crystal growth chamber located below the vaporization separation chamber, and a circulation pipe, a circulation pump, and a heat exchanger connected in sequence. The gasification separation chamber has a central downcomer at its bottom, and the crystal growth chamber has multiple openings at its top. The crystal growth chamber includes an upper part and a lower part. The upper part is divided into a fine crystal zone and a first settling zone from top to bottom, and the lower part is divided into a second settling zone, a crystal slurry zone, and a turbulence zone from top to bottom. The transverse cross-sectional area of ​​the upper part is larger than that of the lower part, and the transverse cross-sectional area of ​​the second settling zone is larger than that of the crystal slurry zone. The central downcomer extends from the opening at the top of the crystal growth chamber to at least the crystal slurry zone. The central downcomer is composed of a main body section and a diffusion section with a trapezoidal longitudinal section. The angle between the sidewall of the diffusion section and the vertical direction is 10°-30°. The circulation pipe is connected to another opening located at the top of the crystallization chamber, and the outlet of the heat exchanger is connected to the inlet of the gasification separation chamber.

2. The evaporator crystallizer according to claim 1, characterized in that, The diameter of the main body section of the central downcomer is 0.8-1.2m, and the total length of the central downcomer is 4.0-5.0m. The length of the diffusion section is 1.0-1.5 times the diameter of the central downcomer. The main body section extends from the opening located at the center of the top of the crystallization chamber to the second settling zone.

3. The evaporator crystallizer according to claim 1, characterized in that, The distance between the bottom of the central downcomer and the bottom of the crystallization chamber is 0.5-1.0 times the diameter of the central downcomer; and / or the central downcomer extends from an opening located at the center of the top of the crystallization chamber to the turbulence zone.

4. The evaporator crystallizer according to claim 1, characterized in that, The top of the gasification separation chamber is equipped with a steam outlet.

5. The evaporator crystallizer according to any one of claims 1-4, characterized in that, The total volume of the crystal growth chamber is 8.0-35.0 m³. 3 .

6. The evaporator crystallizer according to any one of claims 1-4, characterized in that, The upper part of the crystal growth chamber is cylindrical, with a cross-sectional area of ​​6.00-8.00 m². 2 The longitudinal section of the second settling zone and the crystal slurry zone in the crystal growth chamber is an inverted trapezoid, and the bottom area of ​​the crystal slurry zone is 2.00-3.00 m². 2 .

7. The evaporator crystallizer according to any one of claims 1-4, characterized in that, The height of the fine crystal zone accounts for 30-50% of the total height of the crystal growth chamber, the height of the first sedimentation zone accounts for 10-30% of the total height of the crystal growth chamber, the height of the second sedimentation zone accounts for 10-20% of the total height of the crystal growth chamber, and the height of the crystal slurry zone accounts for 10-20% of the total height of the crystal growth chamber.

8. The evaporator crystallizer according to any one of claims 1-4, characterized in that, The angle between the sidewalls of the second settling zone and the crystal slurry zone and the vertical direction is 15°-25°; and / or the height of the tumbling zone accounts for 5-15% of the total height of the crystal growth chamber, and the tumbling zone has an arc-shaped bottom surface, the transverse cross-sectional area of ​​which is smaller than that of the crystal slurry zone.

9. The evaporator crystallizer according to any one of claims 1-4, characterized in that, The crystal growth chamber has one or more discharge ports on its bottom and / or side wall.

10. The evaporator crystallizer according to any one of claims 1-4, characterized in that, The central downcomer is equipped with a temperature sensor and / or a pressure sensor.

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