Freezing crystallization system and method

Abstract

The invention belongs to the technical field of freezing crystallization, and particularly relates to a freezing crystallization system and method.The freezing crystallization system comprises a crystallizer and a heat exchange pipeline, the crystallizer comprises a tank, a gas inlet, a gas outlet, a feeding port and a discharging port, and the flowing direction of a gas flowing path in the tank is opposite to that of a liquid flowing path in the tank; the heat exchange pipeline is provided with a heat exchange device and a pressurizing device, and the heat exchange device is connected with a cold source. The freezing crystallization system and method are optimized, high-pressure gas is ingeniously used as a heat transfer carrier, flowing high-pressure low-temperature gas is used for conducting heat between the heat exchanger and the solution, airflow and the solution are in direct contact for heat transfer, and direct contact between the solution and the wall face of the heat exchanger is avoided. The problems of heat exchanger corrosion and wall surface icing (wall attachment) can be basically solved, the production efficiency of the freezing crystallization process is improved, and the manufacturing cost of the heat exchanger is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of freeze crystallization, and particularly relates to a freeze crystallization system and method. Background Art

[0002] Freeze crystallization technology is a new type of crystallization technology. By lowering the temperature of the solution, specific components in the solution can crystallize out. By collecting the generated crystals, the specific components can be separated from the solution, which has advantages such as low energy consumption and complete separation.

[0003] Currently, the widely used crystallization equipment includes stirred crystallizers and tubular crystallizers, which need to cooperate with heat exchangers for heat exchange. The hot and cold fluids inside the heat exchanger are separated by a wall surface, and heat is conducted from the hot fluid to the cold fluid through the material of the wall surface to complete heat exchange. When this freeze system is operating, a layer of crystals that can form solvent substances is extremely likely to form on the wall surface of the external heat exchanger, affecting the heat transfer efficiency. For example, when a brine solution is freeze-concentrated, ice will form on the surface of the heat exchanger, isolating the brine solution from the heat exchanger wall surface. Since the thermal conductivity of ice crystals is usually much lower than that of the material of the heat exchanger wall surface, the icing phenomenon will cause a significant decrease in the heat transfer efficiency of the heat exchanger, affecting the freeze crystallization efficiency of the crystallizer. Currently, the conventional method to solve the icing (wall fouling) phenomenon is to clean the fouled wall, and cleaning the fouled wall often requires a large amount of clean water for circulating cleaning, and the saline wastewater generated by cleaning also needs to be treated, with high energy consumption; and when the freeze system stops operating, the system needs to be emptied, which will waste some cold energy; if hot clean water at 50 - 70 °C is selected for cleaning in order to improve the cleaning efficiency, a heat source also needs to be provided simultaneously. After retrieval, it is found that Chinese Patent CN202420552511.3 discloses a freeze crystallization device and its system. In this technical solution, two heat exchangers are provided. In the case of wall fouling in the heat exchanger, another heat exchanger can also be switched for heat exchange operation, so as to achieve the effect of continuous operation of the cooling crystallization device. However, it does not actually completely solve the icing (wall fouling) phenomenon.

[0004] In addition, the heat exchanger also faces the problem of corrosion. Many solutions have strong corrosiveness, and ordinary stainless steel and aluminum heat exchangers cannot operate safely for a long time. Therefore, the heat exchanger needs to be made of expensive corrosion-resistant metal materials, which increases the overall manufacturing cost and manufacturing difficulty. Summary of the Invention

[0005] The purpose of the present invention is to overcome the drawbacks and deficiencies existing in the prior art, and provide a freeze crystallization system and method.

[0006] The technical solution adopted by the present invention is as follows: A freeze crystallization system, comprising: The crystallizer includes a tank body, an air inlet, an air outlet, a feed inlet, and a discharge outlet provided on the tank body. The air inlet and the air outlet are communicated through the inner cavity of the tank body to form a gas flow path from the air inlet to the air outlet direction in the inner cavity of the tank body. The feed inlet and the discharge outlet are communicated through the inner cavity of the tank body to form a liquid flow path from the feed inlet to the discharge outlet direction in the inner cavity of the tank body. The flow direction of the gas flow path is opposite to the flow direction of the liquid flow path; The heat exchange pipeline is provided with a heat exchange device and a pressurizing device. The heat exchange device is connected to a cold source. The two ends of the heat exchange pipeline are respectively connected to the air inlet and the air outlet and form a gas pressurized transmission path from the air outlet to the air inlet direction under the action of the pressurizing device.

[0007] The air inlet is arranged at the bottom of the tank body or close to the bottom of the tank body. The air outlet is arranged at the top of the tank body or close to the top of the tank body. The feed inlet is arranged at the top of the tank body or close to the top of the tank body. The discharge outlet is arranged at the bottom of the tank body or close to the bottom of the tank body.

[0008] The heat exchange device includes a pre-cooling heat exchanger and a main heat exchanger. The pre-cooling heat exchanger and the main heat exchanger are arranged successively along the transmission direction of the gas pressurized transmission path. The pre-cooling heat exchanger is connected to a first cold source. The main heat exchanger is connected to a second cold source. The pre-cooling heat exchanger includes a condensate outlet and a gas outlet. A condensate return port is provided on the tank body. The condensate outlet is connected to the condensate return port.

[0009] The pressurizing device is a gas compressor arranged between the pre-cooling heat exchanger and the main heat exchanger.

[0010] A check valve is provided on the heat exchange pipeline, and the check valve is arranged between the heat exchange device and the pressurizing device and the air inlet.

[0011] . A freezing crystallization method, and the freezing crystallization system adopted by it includes: The crystallizer includes a tank body, an air inlet, an air outlet, a feed inlet, and a discharge outlet provided on the tank body. The air inlet and the air outlet are communicated through the inner cavity of the tank body to form a gas flow path from the air inlet to the air outlet direction in the inner cavity of the tank body. The feed inlet and the discharge outlet are communicated through the inner cavity of the tank body to form a liquid flow path from the feed inlet to the discharge outlet direction in the inner cavity of the tank body. The flow direction of the gas flow path is opposite to the flow direction of the liquid flow path; The heat exchange pipeline is provided with a heat exchange device and a pressurizing device. The heat exchange device is connected to a cold source. The two ends of the heat exchange pipeline are respectively connected to the air inlet and the air outlet and form a gas pressurized transmission path from the air outlet to the air inlet direction under the action of the pressurizing device; The heat exchange pipeline is filled with a heat transfer carrier gas. After being cooled by a heat exchange device and pressurized by a pressurizing device, it enters the tank body of the crystallizer through the air inlet, and then leaves the tank body of the crystallizer through the air outlet and enters the heat exchange pipeline. The feed liquid enters the tank body of the crystallizer through the feed port. The liquid and the heat transfer carrier gas form countercurrent heat transfer in the tank body, so that the liquid is cooled and crystallized to form a solid-liquid mixture containing crystals, and then the solid-liquid mixture containing crystals is discharged through the discharge port.

[0012] The air inlet is arranged at the bottom of the tank body or close to the bottom of the tank body. The air outlet is arranged at the top of the tank body or close to the top of the tank body. The feed port is arranged at the top of the tank body or close to the top of the tank body. The discharge port is arranged at the bottom of the tank body or close to the bottom of the tank body.

[0013] The heat exchange device includes a precooling heat exchanger and a main heat exchanger. The precooling heat exchanger and the main heat exchanger are arranged successively along the conveying direction of the gas pressurization and conveying path. The precooling heat exchanger is connected to a first cold source. Under the heat exchange action of the first cold source, the temperature of the medium cooled by the precooling heat exchanger is lower than the condensation temperature of the solvent in the feed liquid and higher than the freezing temperature of the solvent in the feed liquid. The main heat exchanger is connected to a second cold source. Under the heat exchange action of the second cold source, the temperature of the medium cooled by the main heat exchanger is not higher than the preset eutectic temperature of the feed liquid. The precooling heat exchanger includes a condensate outlet and a gas outlet. A condensate return port is provided on the tank body, and the condensate outlet is connected to the condensate return port.

[0014] The pressurizing device is a gas compressor arranged between the precooling heat exchanger and the main heat exchanger, and the outlet pressure of the gas compressor ≥ the liquid pressure at the air inlet in the tank body.

[0015] A check valve is provided on the heat exchange pipeline, and the check valve is arranged between the heat exchange device and the pressurizing device and the air inlet.

[0016] The beneficial effects of the present invention are as follows: By optimizing the freezing crystallization system and method, the present invention cleverly uses high-pressure gas as a heat transfer carrier, uses the flowing high-pressure and low-temperature gas to conduct heat between the heat exchanger and the solution, and the air flow and the solution are in direct contact for heat transfer, avoiding direct contact between the solution and the heat exchanger wall surface. The problems of heat exchanger corrosion and ice formation (wall formation) on the surface of the wall can be basically solved, the production efficiency of the freezing crystallization process is improved, and the manufacturing cost of the heat exchanger is reduced. Description of the Drawings

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, obtaining other drawings based on these drawings still belongs to the scope of the present invention.

[0018] Figure 1 It is a schematic structural diagram of a freezing crystallization system in an embodiment of the present invention; Figure 2 It is a flowchart of the operation of a freezing crystallization method in an embodiment of the present invention; In the figure, Crystallizer - 100, air inlet - 110, air outlet - 120, feed inlet - 130, discharge outlet - 140, condensate return port - 150; Heat exchange pipeline - 200, pre - cooler - 210, main heat exchanger - 220, gas compressor - 230, check valve - 240; First cold source - 310, second cold source - 320. Detailed implementation manners

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings.

[0020] It should be noted that all the expressions using "first" and "second" in the embodiments of the present invention are used to distinguish two non - identical entities or non - identical parameters with the same name. It can be seen that "first" and "second" are only for the convenience of expression and should not be construed as a limitation on the embodiments of the present invention. This will not be elaborated one by one in the subsequent embodiments.

[0021] The terms of direction and position mentioned in the present invention, such as up, down, front, back, left, right, inside, outside, top, bottom, side, etc., are only with reference to the direction or position of the drawings. Therefore, the terms of direction and position used are for explaining and understanding the present invention, rather than a limitation on the protection scope of the present invention.

[0022] The present invention provides a freezing crystallization system, as Figure 1As shown, the crystallizer 100 and the heat exchange pipeline 200 are included. The crystallizer 100 includes a tank body, an air inlet 110, an air outlet 120, a feed inlet 130, a feed outlet 140, and a condensate reflux port 150 arranged on the tank body. The air inlet 110 is arranged at the bottom of the tank body or near the bottom of the tank body, the air outlet 120 is arranged at the top of the tank body or near the top of the tank body, the feed inlet 130 is arranged at the top of the tank body or near the top of the tank body, the feed outlet 140 is arranged at the bottom of the tank body or near the bottom of the tank body, and the condensate reflux port 150 is arranged at the top of the tank body or near the top of the tank body. Figure 2 As shown, the air inlet 110 and the air outlet 120 cooperate in the inner cavity of the tank body to form a path for the gas in the tank to flow from bottom to top, and the feed inlet 130 and the feed outlet 140 cooperate in the inner cavity of the tank body to form a path for the liquid in the tank to flow from top to bottom. The two ends of the heat exchange pipeline 200 are respectively connected to the air inlet 110 and the air outlet 120, and a precooling heat exchanger 210, a gas compressor 230, a main heat exchanger 220, and a check valve 240 are sequentially arranged from the air outlet 120 to the air inlet 110.

[0023] The precooling heat exchanger 210 is connected to the first cold source 310. Under the heat exchange effect of the first cold source 310, the precooling heat exchanger 210 makes the temperature of the medium after cooling down lower than the condensation temperature of the solvent in the feed liquid and higher than the freezing temperature of the solvent in the feed liquid. After the gas passes through the liquid in the tank, it is inevitable to carry out a small amount of vaporized solvent. The present invention sets the precooling heat exchanger 210 to precool the gas discharged through the gas outlet 120, so that the solvent vapor carried in the gas is condensed and liquefied, and then the condensate return port 150 of the ventilation pipe flows back to the tank body of the crystallizer 100. The main heat exchanger 220 is connected to the second cold source 320. Under the heat exchange effect of the second cold source 320, the main heat exchanger 220 makes the temperature of the medium after cooling down not higher than the preset eutectic temperature of the feed liquid, so that the gas is fully cooled in the main heat exchanger. Under the pressure of the gas compressor 230, the gas in the tank is discharged through the gas outlet 120, and is transported under pressure in the heat exchange pipeline 200. After flowing through the pre-cooling heat exchanger 210 and the main heat exchanger 220, it enters the tank through the gas inlet 110 to form a cycle. The gas in the tank flowing from bottom to top forms a countercurrent heat transfer with the liquid in the tank flowing from top to bottom. The feed liquid enters the tank from the feed inlet 130 at the top of the tank, cools down and crystallizes after sufficient heat exchange with the gas, and then the solid-liquid mixture containing crystals is discharged from the discharge port 140 at the bottom. When the low-temperature high-pressure gas passes through the solution, as the pressure decreases and the volume increases, it can also produce an additional throttling effect, further reducing the temperature of the gas flow, which can improve the heat transfer efficiency and crystallization efficiency.

[0024] The present invention ingeniously utilizes high-pressure gas as a heat transfer carrier, and uses flowing high-pressure and low-temperature gas to conduct heat between the heat exchanger and the solution. The gas flow and the solution are in direct contact for heat transfer, avoiding direct contact between the solution and the heat exchanger wall surface. The problems of heat exchanger corrosion and surface crystallization can be basically solved, improving the efficiency and reducing the manufacturing cost of the heat exchanger. Further, through the setting of the precooling heat exchanger 210, the present invention can further effectively avoid the freezing of the solvent vapor entrained in the discharged high-pressure gas in the main heat exchanger 220 after the crystallizer fully exchanges heat with the solution. The check valve 240 is provided to prevent liquid from flowing back into the main heat exchanger 220 and the gas compressor 230.

[0025] In the present invention, the gas used as the heat transfer carrier is preferably an incombustible gas and should not react chemically with any component in the solution, and can be selected according to the type of the feed solution and the required crystallization temperature. Commonly available gases include, but are not limited to, air, nitrogen, inert gases, and gaseous carbon dioxide, etc. When air is not selected as the heat transfer carrier gas, the crystallizer should be ensured to be in the same gas atmosphere as the heat transfer carrier gas.

[0026] In the present invention, the selection of the first cold source 310 and the second cold source 320 includes, but is not limited to, low-temperature atmosphere, compression refrigeration equipment, absorption refrigeration equipment, and low-temperature liquids or gases generated in other industrial processes.

[0027] In the present invention, if the feed liquid contains flammable components, the gas compressor should be a gas compressor that meets the corresponding explosion-proof standards.

[0028] In the present invention, the air pressure generated by the gas compressor should be equal to or slightly greater than the liquid pressure at the liquid inlet 110 in the tank, so that the gas flow can smoothly enter the liquid through the inlet 110. Since the inlet 110 of the present invention is arranged at the bottom of the tank, therefore, the set outlet pressure of the gas compressor ≥ liquid density × liquid level height of the liquid in the tank × local acceleration of gravity, and all variables are calculated using the international standard units.

[0029] Those of ordinary skill in the art can understand that all or part of the steps in the method of the above embodiments can be completed by instructing relevant hardware through a program, and the program can be stored in a computer-readable storage medium, such as ROM / RAM, disk, optical disc, etc.

[0030] The above-disclosed are only the preferred embodiments of the present invention, and of course, the scope of the rights of the present invention cannot be limited thereby. Therefore, equivalent changes made according to the claims of the present invention still fall within the scope covered by the present invention.

Claims

1. A freezing crystallization system, characterized in that: include: A crystallizer, comprising a tank body, an air inlet, an air outlet, a feed port, and a discharge port arranged on the tank body, wherein the air inlet and the air outlet are connected through a tank body cavity to form a gas flow path from the air inlet to the air outlet in the tank body cavity, and the feed port and the discharge port are connected through a tank body cavity to form a liquid flow path from the feed port to the discharge port in the tank body cavity, and the flow direction of the gas flow path is opposite to the flow direction of the liquid flow path; The heat exchange pipeline is provided with a heat exchange device and a pressurizing device. The heat exchange device is connected to a cold source. The two ends of the heat exchange pipeline are respectively connected to an air inlet and an air outlet, and a gas pressurizing transport path from the air outlet to the air inlet is formed under the action of the pressurizing device.

2. The freezing crystallization system according to claim 1, characterized in that: The air inlet is arranged at the bottom of the tank body or near the bottom of the tank body, the air outlet is arranged at the top of the tank body or near the top of the tank body, the feed port is arranged at the top of the tank body or near the top of the tank body, and the discharge port is arranged at the bottom of the tank body or near the bottom of the tank body.

3. The freezing crystallization system according to claim 1, characterized in that: The heat exchange device includes a precooling heat exchanger and a main heat exchanger, which are arranged in sequence along the conveying direction of the gas pressurized conveying path. The precooling heat exchanger is connected to a first cold source, and the main heat exchanger is connected to a second cold source. The precooling heat exchanger includes a condensate outlet and a gas outlet. A condensate reflux port is provided on the tank body, and the condensate outlet is connected to the condensate reflux port.

4. The freezing crystallization system according to claim 3, characterized in that: The pressurizing device is a gas compressor arranged between the precooling heat exchanger and the main heat exchanger.

5. The freezing crystallization system according to claim 1, characterized in that: A check valve is provided on the heat exchange pipeline, and the check valve is arranged between the heat exchange device and the pressurizing device and the air inlet.

6. A freeze crystallization method, characterized in that: The cryo-crystallization system used includes: A crystallizer, comprising a tank body, an air inlet, an air outlet, a feed port, and a discharge port arranged on the tank body, wherein the air inlet and the air outlet are connected through a tank body cavity to form a gas flow path from the air inlet to the air outlet in the tank body cavity, and the feed port and the discharge port are connected through a tank body cavity to form a liquid flow path from the feed port to the discharge port in the tank body cavity, and the flow direction of the gas flow path is opposite to the flow direction of the liquid flow path; The heat exchange pipeline is provided with a heat exchange device and a pressurizing device, the heat exchange device is connected to a cold source, the two ends of the heat exchange pipeline are respectively connected to an air inlet and an air outlet, and a gas pressurizing conveying path from the air outlet to the air inlet is formed under the action of the pressurizing device; The heat exchange pipeline is filled with a heat transfer carrier gas, which enters the tank body of the crystallizer through the air inlet after being cooled by the heat exchange device and pressurized by the pressurizing device, and then leaves the tank body of the crystallizer through the air outlet and enters the heat exchange pipeline. The feed liquid enters the tank body of the crystallizer through the feed port, and the liquid and the heat transfer carrier gas form a countercurrent heat transfer in the tank body, so that the liquid is cooled and crystallized to form a solid-liquid mixture containing crystals, and then the solid-liquid mixture containing crystals is discharged from the discharge port.

7. The freeze crystallization method according to claim 6, wherein: The air inlet is arranged at the bottom of the tank body or near the bottom of the tank body, the air outlet is arranged at the top of the tank body or near the top of the tank body, the feed port is arranged at the top of the tank body or near the top of the tank body, and the discharge port is arranged at the bottom of the tank body or near the bottom of the tank body.

8. The freeze crystallization method according to claim 6, wherein: The heat exchange device includes a precooling heat exchanger and a main heat exchanger, which are arranged in sequence along the conveying direction of the gas pressurized conveying path. The precooling heat exchanger is connected to a first cold source. Under the heat exchange effect of the first cold source, the precooling heat exchanger cools the medium to a temperature lower than the condensation temperature of the solvent in the feed liquid and higher than the freezing temperature of the solvent in the feed liquid. The main heat exchanger is connected to a second cold source. Under the heat exchange effect of the second cold source, the main heat exchanger cools the medium to a temperature not higher than the preset eutectic temperature of the feed liquid. The precooling heat exchanger includes a condensate outlet and a gas outlet. A condensate reflux port is provided on the tank body, and the condensate outlet is connected to the condensate reflux port.

9. The freeze crystallization method according to claim 8, characterized in that: The pressurizing device is a gas compressor arranged between the precooling heat exchanger and the main heat exchanger, and the outlet pressure of the gas compressor is ≥ the liquid pressure at the air inlet in the tank body.

10. The freeze crystallization method according to claim 6, characterized in that: A check valve is provided on the heat exchange pipeline, and the check valve is arranged between the heat exchange device and the pressurizing device and the air inlet.

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