A freeze crystallization system and method

Abstract

This invention belongs to the field of cryo-crystallization technology, specifically relating to a cryo-crystallization system and method, including a crystallizer and heat exchange pipelines. The crystallizer includes a tank, an air inlet, an air outlet, a feed inlet, and a discharge outlet disposed on the tank. The flow direction of the gas inside the tank is opposite to the flow direction of the liquid inside the tank. The heat exchange pipelines are equipped with a heat exchange device and a pressurization device, the heat exchange device being connected to a cold source. This invention, through optimization of the cryo-crystallization system and method, cleverly utilizes high-pressure gas as a heat transfer carrier. The flowing high-pressure, low-temperature gas conducts heat between the heat exchanger and the solution, with direct contact between the gas flow and the solution for heat transfer, avoiding direct contact between the solution and the heat exchanger wall. The problems of heat exchanger corrosion and surface icing (wall formation) can be fundamentally solved, improving the production efficiency of the cryo-crystallization process and reducing the manufacturing cost of the heat exchanger.

Description

Technical Field

[0001] This invention belongs to the field of cryo-crystallization technology, specifically relating to a cryo-crystallization system and method. Background Technology

[0002] Freeze-crystallization is a novel crystallization technique that lowers the solution temperature to allow specific components in the solution to crystallize out. By collecting the crystals, specific components can be separated from the solution. It has advantages such as low energy consumption and complete separation.

[0003] Currently, widely used crystallization equipment includes stirred crystallizers and tubular crystallizers, which require heat exchangers for heat exchange. Inside the heat exchanger, the hot and cold fluids are isolated by a wall, and heat is transferred from the hot fluid to the cold fluid through the wall material. During operation, the outer wall of this refrigeration system is prone to crystallizing, which can form solvent substances, affecting heat transfer efficiency. For example, during the freeze-concentration of brine solutions, ice will form on the heat exchanger surface, isolating the brine solution from the heat exchanger wall. Since the thermal conductivity of ice crystals is usually much lower than that of the heat exchanger wall material, icing significantly reduces the heat transfer efficiency of the heat exchanger, affecting the freeze-crystallization efficiency of the crystallizer. The conventional method to solve the icing (wall formation) problem is wall cleaning. However, wall cleaning often requires large amounts of circulating clean water, and the resulting saline wastewater also needs treatment, resulting in high energy consumption. Furthermore, the refrigeration system needs to be emptied when shut down, wasting some cooling capacity. If hot water at 50–70°C is used for cleaning to improve efficiency, a heat source must also be provided. A search revealed that Chinese patent CN202420552511.3 discloses a freeze crystallization device and system. This technical solution includes two heat exchangers. Even when icing (wall formation) occurs in one heat exchanger, the other heat exchanger can be switched to perform heat exchange, thus achieving continuous operation of the cooling crystallization device. However, it does not actually completely solve the icing (wall formation) problem.

[0004] In addition, heat exchangers also face the problem of corrosion. Many solutions are highly corrosive, and ordinary stainless steel and aluminum heat exchangers cannot operate safely for a long time. Therefore, heat exchangers need 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 this invention is to overcome the shortcomings and deficiencies of the existing technology and to provide a freeze crystallization system and method.

[0006] The technical solution adopted in this invention is as follows: a freeze crystallization system, comprising:

[0007] A crystallizer includes a tank body, an air inlet, an air outlet, a feed inlet, and a discharge outlet disposed on the tank body. The air inlet and the air outlet are connected through the inner cavity of the tank body, forming a gas flow path from the air inlet to the air outlet within the inner cavity of the tank body. The feed inlet and the discharge outlet are connected through the inner cavity of the tank body, forming a liquid flow path from the feed inlet to the discharge outlet within 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.

[0008] The heat exchange pipeline is equipped 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 under the action of the pressurizing device, a gas pressurization and transportation path is formed from the air outlet to the air inlet.

[0009] The air inlet is located at or near the bottom of the tank, the air outlet is located at or near the top of the tank, the feed inlet is located at or near the top of the tank, and the discharge outlet is located at or near the bottom of the tank.

[0010] The heat exchange device includes a precooling heat exchanger and a main heat exchanger, which are arranged sequentially along the gas pressurization and 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. The tank is provided with a condensate return port, and the condensate outlet is connected to the condensate return port.

[0011] The pressurization device is a gas compressor installed between the precooling heat exchanger and the main heat exchanger.

[0012] The heat exchange pipeline is equipped with a check valve, which is located between the heat exchange device and the pressurization device and the air inlet.

[0013] A method for cryo-crystallization, wherein the cryo-crystallization system comprises:

[0014] A crystallizer includes a tank body, an air inlet, an air outlet, a feed inlet, and a discharge outlet disposed on the tank body. The air inlet and the air outlet are connected through the inner cavity of the tank body, forming a gas flow path from the air inlet to the air outlet within the inner cavity of the tank body. The feed inlet and the discharge outlet are connected through the inner cavity of the tank body, forming a liquid flow path from the feed inlet to the discharge outlet within 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.

[0015] The heat exchange pipeline is equipped 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 under the action of the pressurizing device, a gas pressurization and transportation path is formed from the air outlet to the air inlet.

[0016] The heat exchange pipeline is filled with heat transfer carrier gas, which is cooled by the heat exchange device and pressurized by the pressurizing device. It then enters the crystallizer tank through the inlet and exits the crystallizer tank through the outlet. The feed liquid enters the crystallizer tank through the feed inlet. The liquid and the heat transfer carrier gas form a countercurrent heat transfer in the tank, which cools the liquid and crystallizes it to form a solid-liquid mixture containing crystals. The solid-liquid mixture containing crystals is then discharged from the outlet.

[0017] The air inlet is located at or near the bottom of the tank, the air outlet is located at or near the top of the tank, the feed inlet is located at or near the top of the tank, and the discharge outlet is located at or near the bottom of the tank.

[0018] The heat exchange device includes a precooling heat exchanger and a main heat exchanger, which are arranged sequentially along 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 precooling heat exchanger cools the medium to a temperature lower than the condensation temperature of the solvent in the feed liquid but 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 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. The tank is provided with a condensate return port, and the condensate outlet is connected to the condensate return port.

[0019] The pressurization device is a gas compressor installed between the precooling heat exchanger and the main heat exchanger, and the outlet pressure of the gas compressor is greater than or equal to the liquid pressure at the inlet of the tank.

[0020] The heat exchange pipeline is equipped with a check valve, which is located between the heat exchange device and the pressurization device and the air inlet.

[0021] The beneficial effects of this invention are as follows: By optimizing the freeze crystallization system and method, this invention cleverly utilizes high-pressure gas as a heat transfer carrier. The flowing high-pressure, low-temperature gas conducts heat between the heat exchanger and the solution, allowing direct contact between the gas flow and the solution for heat transfer, thus avoiding direct contact between the solution and the heat exchanger wall. This fundamentally solves the problems of heat exchanger corrosion and surface icing (wall formation), improving the production efficiency of the freeze crystallization process and reducing the manufacturing cost of the heat exchanger. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0023] Figure 1 This is a schematic diagram of the structure of a freeze crystallization system in one embodiment of the present invention;

[0024] Figure 2 This is a flowchart illustrating the operation of a freeze-crystallization method in one embodiment of the present invention.

[0025] In the picture,

[0026] Crystallizer-100, air inlet-110, air outlet-120, feed inlet-130, discharge outlet-140, condensate return outlet-150;

[0027] Heat exchange piping - 200, precooling heat exchanger - 210, main heat exchanger - 220, gas compressor - 230, check valve - 240;

[0028] First cold source -310, second cold source -320. Detailed Implementation

[0029] 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 accompanying drawings.

[0030] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0031] The directional and positional terms used in this invention, such as up, down, front, back, left, right, inside, outside, top, bottom, side, etc., are merely for reference to the accompanying drawings. Therefore, the directional and positional terms used are for illustrating and understanding this invention, and not for limiting the scope of protection of this invention.

[0032] This invention provides a freeze-crystallization system, such as Figure 1As shown, the system includes a crystallizer 100 and a heat exchange pipeline 200. The crystallizer 100 includes a tank body, an air inlet 110, an air outlet 120, a feed inlet 130, a discharge outlet 140, and a condensate return outlet 150, all disposed on the tank body. The air inlet 110 is located at or near the bottom of the tank body; the air outlet 120 is located at or near the top of the tank body; the feed inlet 130 is located at or near the top of the tank body; the discharge outlet 140 is located at or near the bottom of the tank body; and the condensate return outlet 150 is located at or near the top of the tank body. Figure 2 As shown, the air inlet 110 and air outlet 120 cooperate to form a bottom-up gas flow path within the tank cavity, while the feed inlet 130 and discharge outlet 140 cooperate to form a top-down liquid flow path within the tank cavity. The heat exchange pipeline 200 is connected to the air inlet 110 and air outlet 120 at its two ends, and from the air outlet 120 towards the air inlet 110, a pre-cooling heat exchanger 210, a gas compressor 230, a main heat exchanger 220, and a check valve 240 are sequentially arranged.

[0033] The precooling heat exchanger 210 is connected to the first cold source 310. Under the heat exchange action of the first cold source 310, the precooling heat exchanger 210 ensures that the temperature of the medium after cooling is lower than the condensation temperature of the solvent in the feed liquid but higher than the freezing temperature of the solvent in the feed liquid. After the gas passes through the liquid in the tank, it is unavoidable that a small amount of vaporized solvent will be carried out. This invention sets up the precooling heat exchanger 210 to precool the gas discharged through the gas outlet 120, so that the solvent vapor carried in the gas will condense and liquefy, and then the condensate return port 150 of the ventilation pipe will return it to the tank of the crystallizer 100. The main heat exchanger 220 is connected to the second cold source 320. Under the heat exchange action of the second cold source 320, the main heat exchanger 220 ensures that the temperature of the medium after cooling is 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 inside the tank is discharged through the outlet 120, pressurized and transported in the heat exchange pipeline 200, flows through the pre-cooling heat exchanger 210 and the main heat exchanger 220, and then enters the tank through the inlet 110, forming a circulation. The gas flowing from bottom to top in the tank and the liquid flowing from top to bottom in the tank form a counter-current heat transfer. The feed liquid enters the tank through the feed inlet 130 at the top of the tank, cools down and crystallizes after sufficient heat exchange with the gas, and then is discharged from the outlet 140 at the bottom as a solid-liquid mixture containing crystals. When the low-temperature, high-pressure gas passes through the solution, the pressure decreases and the volume increases, generating an additional throttling effect, which further reduces the temperature of the gas flow, thereby improving heat transfer efficiency and crystallization efficiency.

[0034] This invention ingeniously utilizes high-pressure gas as a heat transfer medium, employing flowing high-pressure, low-temperature gas to conduct heat between the heat exchanger and the solution. Heat transfer occurs through direct contact between the gas flow and the solution, avoiding direct contact between the solution and the heat exchanger wall. This effectively solves the problems of heat exchanger corrosion and surface crystallization, improving efficiency and reducing manufacturing costs. Furthermore, the pre-cooling heat exchanger 210 effectively prevents solvent vapors carried in the discharged high-pressure gas from freezing and forming ice within the main heat exchanger 220 after sufficient heat exchange between the crystallizer and the solution. The check valve 240 prevents liquid backflow into the main heat exchanger 220 and the gas compressor 230.

[0035] In this invention, the gas used as the heat transfer medium is preferably a non-flammable gas that should not chemically react with any component in the solution. The gas can be selected based on the type of feed solution and the required crystallization temperature. Commonly used gases include, but are not limited to, air, nitrogen, inert gases, and gaseous carbon dioxide. When air is not used as the heat transfer medium, the crystallizer should be kept in the same gaseous atmosphere as the heat transfer medium.

[0036] In this 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.

[0037] In this invention, if the feed liquid contains flammable components, the gas compressor should be a gas compressor that meets the corresponding explosion-proof standards.

[0038] In this invention, the gas pressure generated by the gas compressor should be equal to or slightly greater than the liquid pressure at the inlet 110 inside the tank, so that the airflow can smoothly enter the liquid through the inlet 110. Since the inlet 110 is located at the bottom of the tank, the outlet pressure of the gas compressor is ≥ liquid density × liquid level in the tank × local gravitational acceleration. All variables are calculated using international standard units.

[0039] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, such as ROM / RAM, disk, optical disk, etc.

[0040] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A freeze crystallization system, characterized in that, include: A crystallizer includes a tank body, an air inlet, an air outlet, a feed inlet, and a discharge outlet disposed on the tank body. The air inlet and the air outlet are connected through the inner cavity of the tank body, forming a gas flow path from the air inlet to the air outlet within the inner cavity of the tank body. The feed inlet and the discharge outlet are connected through the inner cavity of the tank body, forming a liquid flow path from the feed inlet to the discharge outlet within 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 equipped 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 under the action of the pressurizing device, a gas pressurization and transportation path is formed from the air outlet to the air inlet. The heat exchange device includes a precooling heat exchanger and a main heat exchanger, which are arranged sequentially along the conveying direction of the gas pressurization and 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. The tank body is provided with a condensate return port, and the condensate outlet is connected to the condensate return port. The pressurization device is a gas compressor installed between the precooling heat exchanger and the main heat exchanger; The air inlet is located at or near the bottom of the tank, the air outlet is located at or near the top of the tank, the feed inlet is located at or near the top of the tank, and the discharge outlet is located at or near the bottom of the tank. The heat exchange pipeline is equipped with a check valve, which is located between the heat exchange device and the pressurization device and the air inlet.

2. A freeze crystallization method, applied to the freeze crystallization system as described in claim 1, characterized in that: The heat exchange pipeline is filled with heat transfer carrier gas, which is cooled by the heat exchange device and pressurized by the pressurizing device. It then enters the crystallizer tank through the inlet and exits the crystallizer tank through the outlet. The feed liquid enters the crystallizer tank through the feed inlet. The liquid and the heat transfer carrier gas form a countercurrent heat transfer in the tank, which cools the liquid and crystallizes it to form a solid-liquid mixture containing crystals. The solid-liquid mixture containing crystals is then discharged from the outlet.

3. The freeze-crystallization method according to claim 2, characterized in that: The air inlet is located at or near the bottom of the tank, the air outlet is located at or near the top of the tank, the feed inlet is located at or near the top of the tank, and the discharge outlet is located at or near the bottom of the tank.

4. The freeze-crystallization method according to claim 2, characterized in that: The heat exchange device includes a precooling heat exchanger and a main heat exchanger, which are arranged sequentially along 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 precooling heat exchanger cools the medium to a temperature lower than the condensation temperature of the solvent in the feed liquid but 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 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. The tank body is provided with a condensate return port, and the condensate outlet is connected to the condensate return port.

5. The freeze-crystallization method according to claim 4, characterized in that: The pressurization device is a gas compressor installed between the precooling heat exchanger and the main heat exchanger, and the outlet pressure of the gas compressor is greater than or equal to the liquid pressure at the inlet of the tank.

6. The freeze-crystallization method according to claim 2, characterized in that: The heat exchange pipeline is equipped with a check valve, which is located between the heat exchange device and the pressurization device and the air inlet.

Images