A method and apparatus for crystallization of high-salinity wastewater

Abstract

The application relates to a high-salt wastewater crystallization method and device, and belongs to the technical field of wastewater treatment. In the method, hot flue gas or hot air is blown through the surface of fine-particle crystal seeds in a scattered state and covered with a water film, heat and mass transfer occurs between the hot flue gas or hot air and the surface of the fine-particle crystal seeds, the water on the surface of the fine-particle crystal seeds evaporates into the flue gas or air, the salt in the high-salt wastewater is crystallized on the surface of the fine-particle crystal seeds, the growing crystal seeds in a scattered state collide with each other or with the wall surface of a crystallizer in the movement, the surface crystals are stripped off, screened and discharged from the crystallizer; the flue gas or air carrying a small amount of fine-particle crystallized salt is discharged after dust removal; and the crystal seeds in a scattered state return to the crystallizer, are re-coated with a water film, evaporate and crystallize, and are recycled. The device has the advantages of strong heat and mass transfer process, large crystallization area, crystal seed strengthening in the crystallization process, and the like, can realize rapid evaporation and crystallization of wastewater by using low-temperature flue gas or air (less than 90 DEG C), and has small volume and weight, and low manufacturing and using costs.

Description

A method and apparatus for crystallizing high-salt wastewater Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically a crystallization device and method for high-salt wastewater. Background Technology

[0002] Currently, over one hundred flue gas desulfurization methods have been researched worldwide, but only about ten are truly applicable to industrial production. Limestone-gypsum wet flue gas desulfurization technology, characterized by high reliability, high desulfurization efficiency, simple operation, and low cost, has been widely adopted by coal-fired power plants both domestically and internationally. However, the efficiency of limestone-gypsum wet flue gas desulfurization is affected by numerous factors, many of which are interrelated. Among these, the high salt content of the generated desulfurization wastewater and the poor effectiveness of traditional wastewater treatment technologies have long been a technical bottleneck hindering environmental protection efforts in coal-fired power plants.

[0003] CN202223289473.7 discloses a zero-discharge system for high-salinity wastewater using a combination of low-temperature multi-effect spraying and a drying tower. This invention employs a conventional method of wastewater atomization spraying and direct contact heat exchange crystallization with high-temperature flue gas. This method requires flue gas temperatures above 300°C, necessitating extremely fine spray nozzles to achieve atomization. However, in practical applications, excessively high flue gas temperatures lead to continuous heating of the nozzles, frequently causing clogging and affecting treatment efficiency. Furthermore, the fine atomized water droplets move with the flue gas, resulting in poor heat convection and reliance solely on 300°C for heat radiation, significantly increasing energy consumption.

[0004] CN202211457570.4 discloses a system and method for direct drying of desulfurization wastewater. This invention draws desulfurization wastewater from the bottom of a gas-liquid separator directly into a spray tank for drying. This method utilizes an atomizing device to directly contact the atomized water droplets of the desulfurization wastewater with the hot flue gas, causing evaporation and crystallization that falls into the ash silo. However, the hot flue gas continuously contacts the atomizing nozzles during the treatment process, causing nozzle blockage. Simultaneously, the flue gas carries atomized water droplets along with it, making thermal convection difficult to occur. Crystallization relies solely on thermal radiation, increasing energy consumption.

[0005] Therefore, finding a high-salinity wastewater treatment technology with good treatment effect and low energy consumption has become an urgent problem to be solved. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method and apparatus for crystallizing high-salt wastewater. Compared with traditional evaporation crystallization apparatus, the apparatus of this invention has the dual advantages of large crystallization area and large heat exchange area, which enhances convective heat transfer and heat radiation conduction, enabling rapid evaporation of water with extremely low energy consumption. At the same time, it also ensures that the equipment is compact in size and weight, reducing manufacturing and operating costs.

[0007] The technical solution of the present invention:

[0008] A method for crystallizing high-salinity wastewater, the specific process of which is as follows:

[0009] (1) Spray the high-salt wastewater evenly onto the surface of the fine-particle seed crystals in a dispersed state, so that the high-salt wastewater covers the surface of the fine-particle seed crystals with a thin water film; or first spray the high-salt wastewater evenly onto the surface of the fine-particle seed crystals so that the high-salt wastewater covers the surface of the fine-particle seed crystals with a thin water film, and then blow the fine-particle seed crystals into a dispersed state.

[0010] (2) Hot flue gas or hot air is blown over the surface of the fine-grained seed crystals in a dispersed state. The hot flue gas or hot air undergoes heat and mass transfer with the surface of the fine-grained seed crystals. The moisture on the surface of the fine-grained seed crystals evaporates and enters the flue gas or air. The salt in the high-salt wastewater crystallizes on the surface of the fine-grained seed crystals. The growing seed crystals in a dispersed state collide with each other or with the crystallizer wall during the movement, peeling off the surface crystals and discharging them from the crystallizer through screening.

[0011] (3) The flue gas or air carrying a small amount of fine crystalline salt particles is discharged after dust removal; the seed crystals that are in a scattered state are returned to the crystallizer to be re-coated with a water film for evaporation and crystallization for recycling.

[0012] Furthermore, the fine-particle seed crystals are surface-activated polymer materials, high-strength salt particles, or other crystals; the high-strength salt particles are one or more mixtures of salts contained in high-salt wastewater.

[0013] Furthermore, hot flue gas or hot air includes residual hot flue gas, residual warm flue gas, dry hot air, and dry warm air.

[0014] A high-salt wastewater crystallization device, comprising a wastewater spraying module, a direct heat and mass transfer evaporation crystallization module, a seed crystal circulation module, and a seed crystal screening and dust removal module;

[0015] The wastewater spraying module and the hot flue gas or hot air inlet are connected to one end of the direct heat and mass transfer evaporation crystallization module, and the seed crystal screening and dust removal module and the hot flue gas or hot air outlet are connected to the other end of the direct heat and mass transfer evaporation crystallization module.

[0016] The spray module is used to uniformly spray high-salt wastewater onto the surface of fine-particle seed crystals and form a water film. The hot flue gas or hot air is blown from one end of the direct heat and mass transfer evaporation crystallization module across the surface of the fine-particle seed crystals in a dispersed motion and discharged from the other end.

[0017] The seed crystal screening and dust removal module is used to screen and remove the fine particles of crystalline salt from flue gas or air carrying a small amount of crystalline salt and then discharge the crystalline salt.

[0018] The seed crystal circulation module is used to return the seed crystals of the salt that have been peeled off from the surface to the direct heat and mass transfer evaporation crystallization module.

[0019] Form 1: The high-salt wastewater crystallization device is a high-salt wastewater external circulation split crystallization device, including a wastewater heat carrier adsorption mixing device 1, a vertical heat exchange crystallization device A2, and a cyclone separator 3.

[0020] The wastewater heat carrier adsorption mixing device 1 includes a shell 4, a wastewater nozzle 5, a stirring blade 6, a horizontal conveying spiral 7, and a cross spiral 8. The shell 4 contains a heat carrier. The wastewater nozzle 5 is located at the top of the shell 4. The stirring blade 6 is located inside the heat carrier adsorption mixing device 1 and is used to stir the sprayed heat carrier. The horizontal conveying spiral 7 and the cross spiral 8 are sequentially located at the bottom of the shell 4. The cross spiral 8 is connected to the bottom of the vertical heat exchange crystallization device A2. The horizontal conveying spiral 7 and the cross spiral 8 are used to transport the stirred heat carrier to the vertical heat exchange crystallization device A2.

[0021] The vertical heat exchange crystallization device A2 is provided with a hot air inlet A9 at the bottom end, which is connected to the hot flue gas, and a hot air outlet A10 at the top end, which is connected to the hot air inlet B11 of the cyclone separator 3.

[0022] The cyclone separator 3 includes a hot air inlet B11, a hot air outlet B12, and a seed crystal outlet A13; the seed crystal outlet A13 is connected to the wastewater heat carrier adsorption and mixing device 1.

[0023] Form 2: The high-salt wastewater crystallization device is an integrated high-salt wastewater external circulation crystallization device, including a vertical heat exchange crystallization device B14, a separator A15, and a spray device A19;

[0024] The vertical heat exchange crystallization device B14 has a straight cylindrical section at the top and a gradually decreasing cylindrical section at the bottom; the separator A15 includes a hot air inlet D20, a hot air outlet D21, and a seed crystal outlet B22.

[0025] A hot air inlet C16 is provided at the bottom of the vertical heat exchange crystallization device B14, and the hot air inlet C16 is connected to the hot flue gas; a supplementary material inlet 18 is provided on one side above the hot air inlet C16, and the other side is connected to the seed crystal outlet B22 at the bottom of the separator A15; a spray device A19 is provided near the supplementary material inlet 18 and the seed crystal outlet B22; a hot air outlet C17 is provided at the top of the vertical heat exchange crystallization device B14, and the hot air outlet C17 is connected to the hot air inlet D20 of the separator A15.

[0026] Form 3: The high-salt wastewater crystallization device is an integrated high-salt wastewater internal circulation crystallization device, including a vertical heat exchange crystallization device C23, a horizontal separator 24, and a spray device; the vertical heat exchange crystallization device C23 is a gradually decreasing diameter cylinder from top to bottom, with a hot air inlet E25 at the bottom connected to hot flue gas; a spray inlet 26 is provided above the hot air inlet E25 and connected to the spray device; an overflow outlet 27 is also provided above the hot air inlet E25; the horizontal separator 24 is located at the top of the vertical heat exchange crystallization device C23, with an internal gas inlet 28 between the two; the horizontal separator 24 includes an internal gas inlet 28, a separator ash outlet 29, and a hot air outlet E30.

[0027] Furthermore, the structure of the horizontal separator 24 is similar to that of the cyclone separator. The diameter of the cyclone separator needs to be changed from a gradual change to a straight cylinder. The outlet pipe in the cyclone separator is extended to the other end of the separator, so that the gas entering the horizontal separator 24 rotates around the periphery of the outlet pipe from the beginning to the other end of the separator, and then enters the interior of the outlet pipe from the other end and is discharged from the separator from the beginning along the outlet pipe. The ash hopper is set at the lower end of the horizontal separator 24.

[0028] Form 4: The high-salt wastewater crystallization device is a horizontal split-type crystallization device with external circulation for high-salt wastewater, including a horizontal heat exchange crystallization device 31, a separator B32 and a spray device B37.

[0029] The horizontal heat exchange crystallization device 31 includes a hot air inlet F33, a hot air outlet F34, a seed crystal outlet C35, and a seed crystal circulation inlet 36; the separator B32 includes a hot air inlet G39, a hot air outlet G38, and a seed crystal outlet D40.

[0030] The hot air outlet F34 of the horizontal heat exchange crystallization device 31 is connected to the hot air inlet G39 of the separator B32. The auger of the horizontal heat exchange crystallization device 31 is welded to the inner wall, and the crystallized salt is stirred and moved as the cylinder rotates. The nozzles of the spray device B37 are evenly distributed on the inner wall of the horizontal heat exchange crystallization device 31.

[0031] The seed outlet D40 of the separator B32 is connected to the seed circulation inlet 36 of the horizontal heat exchange crystallization device 31.

[0032] The beneficial effects of this invention are:

[0033] 1. Compared with traditional evaporation and crystallization methods, the method of this invention utilizes the large specific surface area of ​​the heat carrier to increase the heat exchange area. At the same time, compared with spray drying, this method utilizes the gravity of the heat carrier itself to counteract wind pressure, enhances heat convection and heat transfer, reduces the requirement for the initial temperature of the hot air, and can rapidly evaporate moisture with extremely low energy consumption.

[0034] 2. It ensures that the equipment is compact in size and weight, reducing manufacturing and operating costs. Attached Figure Description

[0035] Figure 1 is a schematic diagram of the principle of a high-salt wastewater crystallization method.

[0036] Figure 2 is a schematic diagram of a split-type crystallization device for external circulation of high-salt wastewater.

[0037] Figure 3 is a front view of a split-type crystallization device for external circulation of high-salt wastewater.

[0038] Figure 4 is a front view of the wastewater heat carrier adsorption and mixing device of a high-salt wastewater external circulation split crystallization device.

[0039] Figure 5 is a cross-sectional view of the wastewater heat carrier adsorption and mixing device of a high-salt wastewater external circulation split crystallization device.

[0040] Figure 6 is a front view of an integrated crystallization device for external circulation of high-salt wastewater.

[0041] Figure 7 is a front view of an integrated crystallization device for internal circulation of high-salt wastewater.

[0042] Figure 8 is a schematic diagram of a horizontal separator in an integrated crystallization device for internal circulation of high-salt wastewater.

[0043] Figure 9 is a cross-sectional view of a horizontal separator in an integrated crystallization device for internal circulation of high-salt wastewater.

[0044] Figure 10 is a schematic diagram of a horizontal split-type crystallization device for external circulation of high-salt wastewater.

[0045] In the diagram: 1 Wastewater heat carrier adsorption mixing device, 2 Vertical heat exchange crystallization device A, 3 Cyclone separator, 4 Shell, 5 Wastewater nozzle, 6 Stirring blades, 7 Horizontal conveying screw, 8 Crossed screw, 9 Hot air inlet A, 10 Hot air outlet A, 11 Hot air inlet B, 12 Hot air outlet B, 13 Seed crystal outlet A, 14 Vertical heat exchange crystallization device B, 15 Separator A, 16 Hot air inlet C, 17 Hot air outlet C, 18 Supplementary material inlet, 19 Spray device A, 20 Hot air inlet D, 21 Hot air outlet D; 22 Seed crystal outlet B; 23 Vertical heat exchange crystallization device C; 24 Horizontal separator; 25 Hot air inlet E; 26 Spray inlet; 27 Slag overflow port; 28 Internal gas inlet; 29 Separator ash discharge port; 30 Hot air outlet E; 31 Horizontal heat exchange crystallization device; 32 Separator B; 33 Hot air inlet F; 34 Hot air outlet F; 35 Seed crystal outlet C; 36 Seed crystal circulation inlet; 37 Spray device B; 38 Hot air outlet G; 39 Hot air inlet G; 40 Seed crystal outlet D. Detailed Implementation

[0046] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0047] Example 1: Treatment of desulfurization high-salinity wastewater using a split-type crystallization device with external circulation.

[0048] The crystalline salt is placed in the wastewater heat carrier adsorption mixing device 1. The desulfurized high-salt wastewater is sprayed from the wastewater nozzle 5 onto the surface of the crystalline salt to form a thin film. The surface of the crystalline salt is evenly covered with the desulfurized high-salt wastewater by the stirring blades 6. The crystalline salt with the film is sent to the cross spiral 8 by the horizontal conveying spiral 7 below, and then sent to the vertical heat exchange crystallization device A2 by the cross spiral 8.

[0049] Hot flue gas is blown in through the hot air inlet A9 of the vertical heat exchange crystallization device A2. When the hot flue gas with a certain flow rate comes into contact with the fine crystallized salt particles, the crystallized salt is fluidized. At this time, the hot flue gas and the crystallized salt reach the optimal heat exchange state, causing the high-salt desulfurization wastewater on the surface to evaporate rapidly. The waste salt aggregates on the surface of the crystallized salt. The hot flue gas after heat exchange enters the cyclone separator 3 through the hot air outlet A10. The crystallized salt with attached waste salt is separated from the hot air by inertial centrifugal force and returns to the wastewater crystallization salt adsorption and mixing device 1 through the crystallization salt outlet A13 below the cyclone separator 3. During this process, stirring, oscillation and collision cause the waste salt on the surface of the crystallized salt to peel off. The crystallized salt continues to be used. The process is repeated. The hot flue gas is sent out of the device through the hot air outlet B12 of the cyclone separator 3.

[0050] Example 2: Treatment of desulfurization high-salt wastewater using an integrated crystallization device with external circulation for high-salt wastewater

[0051] The high-salt desulfurization wastewater is evenly sprayed onto the surface of the rising crystallized salt in the furnace through the spray device 19 inside the vertical heat exchange crystallization device B14, forming a thin film. Hot flue gas enters through the hot air inlet C16 of the vertical heat exchange crystallization device B14. When the hot flue gas with a certain flow rate blows the crystallized salt upward, the high-salt desulfurization wastewater on the surface of the crystallized salt completes the evaporation and crystallization process during the upward movement. The dried crystallized salt reaches the top of the vertical heat exchange crystallization device B14 with the flue gas and enters the separator 15 through the hot air outlet C17. After separation by the separator 15, the hot flue gas is sent out of the device through the hot air outlet D21 of the separator 15, and the crystallized salt returns to the vertical heat exchange crystallization device B14 through the crystallization salt outlet B22. It then undergoes spraying again. During this process, stirring, oscillation, and collision cause the waste salt on the surface of the crystallized salt to peel off. The crystallized salt is then reused, and the above process is repeated.

[0052] When the internal crystallized salt is insufficient, it can be supplemented through the supplementary material inlet 18 of the vertical heat exchange crystallization device B14.

[0053] Example 3: Treatment of desulfurization high-salt wastewater using an integrated internal circulation crystallization device for high-salt wastewater.

[0054] The high-salt desulfurization wastewater is evenly sprayed onto the surface of the rising crystallized salt in the furnace through the spray inlet 26 inside the vertical heat exchange crystallization device C23, forming a thin film. Hot flue gas enters through the hot air inlet E25 of the vertical heat exchange crystallization device C23. When the hot flue gas with a certain flow rate blows the crystallized salt upward, the high-salt desulfurization wastewater on the surface of the crystallized salt completes the evaporation and crystallization process during this process. After the dried crystallized salt reaches the upper part of the vertical heat exchange crystallization device C23 with the flue gas, due to the decrease in air pressure and the increase in gravity, the crystallized salt falls back down to continue spraying. During this process, the stirring, oscillation and collision cause the waste salt on the surface of the crystallized salt to peel off, and the crystallized salt continues to be used. This process is repeated until the salt crystals accumulate to a certain height and reach the discharge height, at which point it will be automatically discharged through the overflow port 27.

[0055] Hot flue gas and fine particles enter the horizontal separator 24 through the internal gas inlet 28. After the hot flue gas removes the fine particles, it is discharged through the hot air outlet E30. The fine particles are centrifuged and then returned to the inside of the device through the separator ash outlet 29.

[0056] Example 4 uses a horizontal, split-type crystallization device with external circulation for treating desulfurization high-salt wastewater.

[0057] The desulfurization high-salt wastewater is sprayed onto the surface of the crystallized salt through nozzles evenly distributed on the inner wall of the horizontal heat exchange crystallization device 31. Dry hot flue gas enters the horizontal heat exchange crystallization device 31 through the hot air inlet F33. The rotation of the horizontal heat exchange crystallization device 31 drives the auger welded to the inner wall and the high-salt spray water to continuously stir, so that a thin water film covers the surface of the crystal seed. The dry hot flue gas is mixed evenly and loosely, so that the high-salt wastewater evaporates quickly.

[0058] After heat exchange, the humid and hot flue gas enters the separator B32 through the hot air outlet F34. After the solid particles in the hot flue gas are separated by the separator B32, they are sent back to the horizontal heat exchange crystallization device 31 through the seed crystal outlet D40 for continued use. During this process, the stirring, oscillation and collision cause the waste salt on the surface of the crystallized salt to peel off. The crystallized salt continues to be used, and the excess crystallized salt is discharged through the seed crystal outlet C35. The separated humid and hot flue gas is discharged from the system through the hot air outlet G38.

Claims

1. A crystallization device for high-salinity wastewater, characterized in that, The high-salt wastewater crystallization device includes a wastewater spraying module, a direct heat and mass transfer evaporation crystallization module, a seed crystal circulation module, and a seed crystal screening and dust removal module. The wastewater spraying module and the hot flue gas or hot air inlet are connected to one end of the direct heat and mass transfer evaporation crystallization module, while the seed crystal screening and dust removal module and the hot flue gas or hot air outlet are connected to the other end of the direct heat and mass transfer evaporation crystallization module. The spraying module is used to uniformly spray high-salt wastewater onto the surface of fine-particle seed crystals to form a water film. The hot flue gas or hot air is blown from one end of the direct heat and mass transfer evaporation crystallization module across the surface of the fine-particle seed crystals in a dispersed motion and discharged from the other end. The seed crystal screening and dust removal module is used to screen and remove dust from the flue gas or air carrying a small amount of fine-particle crystallized salt before discharging the crystallized salt. The seed crystal circulation module is used to return the seed crystals of the surface-peeled crystallized salt to the direct heat and mass transfer evaporation crystallization module; the high-salt wastewater crystallization device is a high-salt wastewater internal circulation integrated crystallization device, including a vertical heat exchange crystallization device C (23), a horizontal separator (24) and a spray device. The vertical heat exchange crystallization device C (23) is a gradually decreasing diameter cylinder from top to bottom. A hot air inlet E (25) is located at the bottom and connected to the hot flue gas. A spray inlet (26) is located above the hot air inlet E (25) and connected to the spray device. An overflow outlet (27) is also located above the hot air inlet E (25). A horizontal separator (24) is located at the top of the vertical heat exchange crystallization device C (23), with an internal gas inlet (28) between them. The horizontal separator (24) includes an internal gas inlet (28), a separator ash outlet (29), and a hot air outlet E (30). Hot flue gas and fine particles enter the horizontal separator (24) through the internal gas inlet (28). After the flue gas is de-particled, it is discharged through the hot air outlet E (30). The fine particles are centrifuged and then returned to the inside of the device through the separator ash outlet (29). The structure of the horizontal separator (24) is similar to that of the cyclone separator. The diameter of the cyclone separator needs to be changed from a gradual change to a straight cylinder. The outlet pipe in the cyclone separator is extended to the other end of the separator. This allows the gas entering the horizontal separator (24) to rotate around the outside of the outlet pipe from the beginning to the other end of the separator, and then enter the inside of the outlet pipe from the other end and exit the separator from the beginning along the outlet pipe. The separator ash outlet (29) is located at the lower end of the horizontal separator (24) and is located to the right of the internal gas inlet (28).

2. A method for crystallizing high-salinity wastewater, applied to the high-salinity wastewater crystallization apparatus as described in claim 1, characterized in that, The specific process is as follows: (1) Spray the high-salt wastewater evenly onto the surface of the fine-particle seed crystals in a dispersed state, so that the high-salt wastewater covers the surface of the fine-particle seed crystals with a thin water film; or first spray the high-salt wastewater evenly onto the surface of the fine-particle seed crystals so that the high-salt wastewater covers the surface of the fine-particle seed crystals with a thin water film, and then blow the fine-particle seed crystals into a dispersed state; (2) Use hot flue gas or hot air to blow over the surface of the fine-particle seed crystals in a dispersed state, and the hot flue gas or hot air undergoes heat and mass transfer with the surface of the fine-particle seed crystals. The water on the surface of the fine-particle seed crystals evaporates and enters the flue gas or air. The salt in the high-salt wastewater crystals crystallizes on the surface of the fine-particle seed crystals. The growing seed crystals in a dispersed state collide with each other or with the crystallizer wall during the movement, peel off the surface crystals, and discharge them from the crystallizer after screening. (3) The flue gas or air carrying a small amount of fine crystalline salt particles is discharged after dust removal; the seed crystals that are in a scattered state are returned to the crystallizer to be re-coated with a water film for evaporation and crystallization for recycling.

3. The crystallization method for high-salinity wastewater according to claim 2, characterized in that, The fine-grained seed crystals are surface-activated polymer materials, high-strength salt particles, or other crystals; the high-strength salt particles are one or more mixtures of salts contained in high-salt wastewater.

4. The crystallization method for high-salinity wastewater according to claim 2, characterized in that, Hot flue gas or hot air includes residual hot flue gas, residual warm flue gas, dry hot air, and dry warm air.

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