CN-122006471-A - Cryogenic rectification system and cryogenic rectification process

CN122006471ACN 122006471 ACN122006471 ACN 122006471ACN-122006471-A

Abstract

A low temperature rectification system and a low temperature rectification method belong to the technical field of low temperature rectification. The cryogenic rectification system comprises a rectification column, a cryogenic circulation unit and a high temperature circulation unit. The high-temperature circulation unit forms a circulation channel of the high-temperature refrigerant, the low-temperature circulation unit forms a circulation channel of the low-temperature mixed refrigerant, and the high-temperature refrigerant in a low-temperature state can exchange heat with the low-temperature refrigerant in a high-temperature state in the evaporation condenser to absorb heat of the low-temperature mixed refrigerant. The low-temperature circulation unit is provided with at least two heat exchangers, at least two expansion devices and at least one gas-liquid separator, so that the refrigerant with higher evaporation temperature in the low-temperature mixed refrigerant can be condensed, separated from gas and liquid, throttled and cooled, and subjected to heat exchange with the refrigerant gas with lower evaporation temperature, thereby realizing gradient cooling of the refrigerant with lower evaporation temperature, and being beneficial to efficiently and accurately providing cold energy for the top condenser of the rectifying tower.

Inventors

XIONG WEI
HUANG HUAFAN
LI DONGSHENG
QING YONG

Assignees

正帆科技(潍坊)有限公司
上海正帆科技股份有限公司

Dates

Publication Date: 20260512
Application Date: 20260325

Claims (10)

1. A cryogenic rectification system comprising a first stage and a second stage, characterized by comprising the following steps: The rectifying tower is provided with a tower top condenser; the high-temperature circulation unit comprises a first compressor, a first condenser and a first expansion device which are connected through pipelines, wherein the high-temperature circulation unit is provided with a high-temperature refrigerant gas which can flow to an evaporation condenser through the first compressor, the first condenser and the first expansion device in sequence, exchanges heat with a low-temperature mixed refrigerant at the evaporation condenser, absorbs heat and is changed into the high-temperature refrigerant gas again, and circulates; the low-temperature circulation unit comprises a first heat exchanger, a first gas-liquid separator, a second heat exchanger, a second expansion device, a third expansion device and a second compressor which are connected through pipelines; The low-temperature circulation unit is provided with a low-temperature mixed refrigerant, a first gas-liquid mixture, a second gas-liquid separator, a third expansion device and a second expansion device, wherein the low-temperature mixed refrigerant can be sequentially subjected to heat exchange with the high-temperature refrigerant at the evaporation condenser and the first working medium at the first heat exchanger to form a first gas-liquid mixture, the first gas-liquid mixture is separated into refrigerant liquid and refrigerant gas through the first gas-liquid separator, the refrigerant gas and the second working medium at the second heat exchanger are subjected to heat exchange and condensation, and then flow into the top condenser through the third expansion device, the refrigerant liquid is mixed with the refrigerant discharged from the top condenser through the second expansion device to form the second working medium, the second working medium is subjected to the second heat exchanger to form the first working medium, and the first working medium is subjected to the first heat exchanger and the second compressor to form the low-temperature mixed refrigerant, so that the circulation medium is formed.
2. The cryogenic rectification system of claim 1 wherein the cryogenic mixed refrigerant comprises a first refrigerant and a second refrigerant, the first refrigerant having an evaporation temperature that is lower than an evaporation temperature of the second refrigerant; The first gas-liquid separator is configured to separate a second refrigerant liquid and a first refrigerant gas, the first refrigerant gas is condensed by heat exchange with the second working medium at the second heat exchanger, the second refrigerant liquid flows into the overhead condenser through the third expansion device, and the second refrigerant liquid is mixed with the first refrigerant discharged from the overhead condenser through the second expansion device to form the second working medium.
3. The cryogenic rectification system of claim 2 wherein the outlet of the first condenser is connected to the cryogenic inlet of the evaporative condenser by the first expansion device and the high temperature outlet of the evaporative condenser is connected to the inlet of the first compressor; The outlet of the second compressor is connected with the high-temperature inlet of the evaporative condenser, and the low-temperature outlet of the evaporative condenser is connected with the high-temperature inlet of the first heat exchanger; the low-temperature outlet of the first heat exchanger is connected with the inlet of the first gas-liquid separator, the air outlet of the first gas-liquid separator is connected with the high-temperature inlet of the second heat exchanger, and the liquid outlet of the first gas-liquid separator is connected with the low-temperature inlet of the second heat exchanger through the second expansion device; the low-temperature outlet of the second heat exchanger is connected with the inlet of the tower top condenser through the third expansion device, and the outlet of the tower top condenser is connected with the low-temperature inlet of the second heat exchanger.
4. The cryogenic rectification system of claim 1 wherein the cryogenic mixed refrigerant comprises a second refrigerant, a third refrigerant and a first refrigerant having progressively lower evaporating temperatures; The low-temperature circulation unit further comprises a second gas-liquid separator, a fourth expansion device and a third heat exchanger which are connected through pipelines, wherein the first gas-liquid mixture is used for separating second refrigerant liquid and refrigerant gas through the first gas-liquid separator, the refrigerant gas comprises first refrigerant gas and third refrigerant gas, the refrigerant gas is used for forming a second gas-liquid mixture through heat exchange condensation with the second working medium at the second heat exchanger, the second gas-liquid mixture is used for separating third refrigerant liquid and first refrigerant gas through the second gas-liquid separator, the first refrigerant gas is used for heat exchange condensation with the third working medium at the third heat exchanger, the third refrigerant liquid flows into the top condenser through the third expansion device, the third refrigerant liquid is mixed with the first working medium discharged from the top condenser through the fourth expansion device to form the third working medium, the third working medium flows into the second heat exchanger through the third heat exchanger, and the second working medium flows into the second heat exchanger through the second expansion device.
5. The cryogenic rectification system of claim 4 wherein the cryogenic outlet of the second heat exchanger is connected to the inlet of the second gas-liquid separator, the outlet of the second gas-liquid separator is connected to the high temperature inlet of the third heat exchanger, the outlet of the second gas-liquid separator is connected to the cryogenic inlet of the third heat exchanger via the fourth expansion device, the cryogenic outlet of the third heat exchanger is connected to the inlet of the overhead condenser via the second expansion device, the outlet of the overhead condenser is connected to the cryogenic inlet of the third heat exchanger, and the high temperature outlet of the third heat exchanger is connected to the cryogenic inlet of the second heat exchanger.
6. The cryogenic rectification system of claim 1 wherein the cryogenic cycle unit further comprises a fifth expansion device, an inlet of the fifth expansion device being selectively connected to an outlet of the second compressor, an outlet of the fifth expansion device being connected to an inlet of the overhead condenser.
7. The cryogenic rectification system of claim 1 further comprising an emergency unit comprising a second condenser, an outlet of the overhead condenser being selectively connectable to an inlet of the second condenser, an outlet of the second condenser being selectively connectable to an inlet of the overhead condenser.
8. The cryogenic rectification system of claim 1 wherein the cryogenic cycle unit further comprises a regenerator provided with heat exchange channels through which the high temperature outlet of the first heat exchanger is connected to the inlet of the second compressor, and wherein the cryogenic rectification system further is provided with a feed conduit connected to the feed inlet of the rectification column through the heat exchange channels.
9. The cryogenic rectification system of claim 4 wherein a buffer tank is further provided between said third expansion device outlet and said overhead condenser inlet; The cryogenic rectification system is also provided with a control unit, wherein the control unit comprises a controller, a conveying device, a control device and a temperature sensor arranged on the buffer tank, and the conveying device comprises a conveying pump and a flow control valve which are arranged at a pipeline connecting the outlet of the buffer tank and the inlet of the tower top condenser; the control device comprises a pressure control valve arranged at a pipeline connecting the low-temperature inlet of the third heat exchanger and the outlet of the tower top condenser; The temperature sensor, the delivery pump, the flow control valve and the pressure control valve are all in signal connection with the controller; The controller is at least provided with a means for increasing the flow rate of the flow rate control valve when the temperature sensor detects that the temperature at the top of the rectifying column is higher than a set value, and a means for decreasing the flow rate of the flow rate control valve.
10. A cryogenic rectification process employing the cryogenic rectification system of any one of claims 1 to 9, the cryogenic rectification process comprising: Injecting high-temperature refrigerant into the high-temperature circulation unit, enabling the high-temperature refrigerant gas to flow to the evaporation condenser through the first compressor, the first condenser and the first expansion device in sequence, performing heat exchange with low-temperature mixed refrigerant at the evaporation condenser, absorbing heat and re-phase to become the high-temperature refrigerant gas, and circulating the high-temperature refrigerant gas; The method comprises the steps of injecting a low-temperature mixed refrigerant into a low-temperature circulation unit, enabling gas of the low-temperature mixed refrigerant to be sequentially subjected to heat exchange with the high-temperature refrigerant at an evaporation condenser and a first working medium at a first heat exchanger to form a first gas-liquid mixture, utilizing the first gas-liquid separator to conduct gas-liquid separation on the first gas-liquid mixture to obtain refrigerant liquid and refrigerant gas, enabling the refrigerant gas to be subjected to heat exchange condensation with a second working medium at a second heat exchanger, then conveying the refrigerant gas to a top condenser of a rectifying tower through a third expansion device, and carrying out heat exchange with a top gas phase of the rectifying tower to realize low-temperature rectification, enabling the refrigerant liquid to be subjected to heat exchange with the refrigerant discharged from the top condenser through the second expansion device to form the second working medium, enabling the first working medium to be subjected to heat exchange through the second heat exchanger to form the first working medium, and enabling the first working medium to be subjected to heat exchange with the second compressor to form the gas of the low-temperature mixed refrigerant, and circulating the low-temperature mixed refrigerant; Optionally, the low-temperature mixed refrigerant includes a first refrigerant and a second refrigerant, the first refrigerant having an evaporation temperature lower than an evaporation temperature of the second refrigerant, the second refrigerant having an evaporation temperature lower than an evaporation temperature of the high-temperature refrigerant; optionally, the high temperature refrigerant comprises at least one of R404A, R507, R414A, R454C, or R448A; Optionally, the low temperature mixed refrigerant includes at least two of R290, R170, R1150, R14, R23; optionally, the low temperature mixed refrigerant includes R290, R14, and R23.

Description

Cryogenic rectification system and cryogenic rectification process Technical Field The application relates to the technical field of low-temperature rectification, in particular to a low-temperature rectification system and a low-temperature rectification method. Background The rapid development of nuclear technology and the semiconductor industry has placed a great demand for high abundance of boron-10 (for neutron control) and boron-11 (for electronic industry dopants) isotopes. Boron trifluoride (BF 3) is the most commonly used precursor material for boron isotope separation, and effective separation can be achieved by cryogenic rectification process using the small difference in boiling points of 10BF3 and 11BF3 molecules. The core of the rectification process is to maintain the rectification column in an extremely stable and accurate cryogenic environment with an optimum operating temperature of about-100 ℃ at about 173K. In the prior art, liquid nitrogen (boiling point-196 ℃) is often used as a cold source. However, the direct use of liquid nitrogen has the following drawbacks: 1. The freezing risk of the material is that the liquid nitrogen temperature is far lower than the freezing point (-127 ℃) of BF 3. The direct heat exchange can cause local supercooling in the rectifying tower, so that BF 3 is liquefied and frozen, tower plates, fillers and pipelines are blocked, the device is stopped, and even safety accidents are caused. 2. Low efficiency and unstable temperature control, in order to avoid freezing, liquid nitrogen is generally adopted to cool the intermediate secondary refrigerant, and then the secondary refrigerant is used for indirectly cooling the rectifying tower. The secondary heat exchange mode has obvious heat transfer temperature difference and heat loss, and has extremely low refrigeration efficiency and huge energy consumption. Meanwhile, the thermal inertia of the intermediate secondary refrigerant system is large, so that the temperature control response is slow, and the accurate temperature control required by the rectification process is difficult to realize. Accordingly, there is a strong need in the art for a cryogenic rectification system and method that can efficiently and accurately maintain cryogenic refrigeration. Disclosure of Invention Based on the defects, the application provides a low-temperature rectification system and a low-temperature rectification method, which can directly, efficiently and accurately provide low-temperature cold energy for a rectification tower to realize low-temperature rectification. The application is realized in the following way: In a first aspect, examples of the present application provide a cryogenic rectification system comprising a rectification column, a high temperature circulation unit and a low temperature circulation unit. Wherein the rectifying tower is provided with a tower top condenser. The high temperature circulation unit includes a first compressor, a first condenser, and a first expansion device connected by a pipe. The low-temperature circulation unit comprises a first heat exchanger, a first gas-liquid separator, a second heat exchanger, a second expansion device, a third expansion device and a second compressor which are connected through pipelines. The high-temperature circulation unit is provided with a first compressor, a first condenser and a first expansion device, wherein the high-temperature refrigerant gas can flow to the evaporation condenser sequentially, and is subjected to heat exchange with the low-temperature mixed refrigerant at the evaporation condenser, and the absorbed heat is changed into the high-temperature refrigerant gas again, so that the high-temperature refrigerant gas circulates. The low-temperature circulation unit is provided with a low-temperature mixed refrigerant which can be sequentially subjected to heat exchange with the high-temperature refrigerant at the evaporation condenser and the first working medium at the first heat exchanger to form a first gas-liquid mixture. The first gas-liquid mixture is separated into a refrigerant liquid and a refrigerant gas by a first gas-liquid separator. The refrigerant gas is condensed with the second working medium at the second heat exchanger through heat exchange, and flows into the tower top condenser through the third expansion device. The refrigerant liquid is passed through a second expansion device and mixed with refrigerant exiting the overhead condenser to form a second working fluid. The second working medium passes through the second heat exchanger to form a first working medium, and the first working medium passes through the first heat exchanger and the second compressor to form a low-temperature mixed refrigerant so as to circulate. In the implementation process, a high-temperature refrigerant is adopted in the high-temperature cycle, a low-temperature mixed refrigerant is adopted in the low-temperature cycle, and the evaporation te