CN-121972000-A - Cryogenic rectification system and cryogenic rectification process

CN121972000ACN 121972000 ACN121972000 ACN 121972000ACN-121972000-A

Abstract

A low temperature rectification system and a low temperature rectification method belong to the field of low temperature rectification. The high-temperature refrigerant of the high-temperature circulation unit absorbs heat of the low-temperature mixed refrigerant in the low-temperature circulation unit. The low-temperature circulation unit provides cold energy for the tower top condenser, and the refrigerant subjected to heat exchange with the materials is discharged to the thermal circulation unit from the tower top condenser. The first heat exchanger, the first compressor and the second compressor of the thermal circulation unit are utilized to compress and heat the refrigerant, provide energy for the intermediate reboiler and the tower kettle reboiler, then flow back to the low-temperature circulation unit, and exchange heat with the high-temperature circulation unit again, so that the circulation is realized. Above-mentioned cryogenic rectification system not only can provide the cold energy to cryogenic rectification, has still realized the heat and has recycled to middle reboiler's setting can replace traditional last tower reboiler and lower tower condenser, has saved partial independent heat source and partial cold source, and it is more abundant to go up the energy utilization between tower and the lower tower, and multi-tower parallel operation also can improve separation efficiency, and then reduces the energy consumption.

Inventors

XIONG WEI
HUANG HUAFAN
LIU HUI
LIU XUBO

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: 20260505
Application Date: 20260325

Claims (11)

1. A cryogenic rectification system comprising a first stage and a second stage, characterized by comprising the following steps: The rectifying unit comprises a lower tower and a plurality of upper towers which are arranged in parallel, wherein the top of the lower tower is connected with the plurality of upper towers through an intermediate reboiler, and the bottom of the lower tower is provided with a tower kettle reboiler; The system comprises a high-temperature circulation unit and a low-temperature circulation unit, wherein the high-temperature circulation unit is provided with a circulation channel for circulating high-temperature refrigerant, and the low-temperature circulation unit is provided with a circulation channel for circulating low-temperature mixed refrigerant; The heat circulation unit comprises a first heat exchanger, a high-temperature outlet of the tower top condenser is connected with a low-temperature inlet of the first heat exchanger, the high-temperature outlet of the first heat exchanger is connected with a high-temperature inlet of the intermediate reboiler through a first compressor, a low-temperature outlet of the intermediate reboiler is connected with a high-temperature inlet of the tower kettle reboiler through a second compressor, a low-temperature outlet of the tower kettle reboiler is connected with a high-temperature inlet of the first heat exchanger, and a low-temperature outlet of the first heat exchanger is connected with a refrigerant inlet of the low-temperature circulation unit.
2. The cryogenic rectification system of claim 1 wherein the thermal cycle unit is further provided with a second heat exchanger, the low temperature outlet of the intermediate reboiler being selectively connectable to the high temperature inlet of the second heat exchanger, the low temperature outlet of the second heat exchanger being connectable to the high temperature inlet of the first heat exchanger.
3. The cryogenic rectification system of claim 1 wherein said high temperature circulation unit comprises a first compressor, a first condenser and a first expansion device, an outlet of said first condenser being connected to a low temperature inlet of said evaporative condenser by said first expansion device, a high temperature outlet of said evaporative condenser being connected to an inlet of said first compressor, an outlet of said first compressor being connected to an inlet of said first condenser to form a circulation path for said high temperature refrigerant.
4. The cryogenic rectification system of claim 3 wherein the cryogenic cycle 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 connected by piping; 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 low-temperature inlet of the tower top condenser through the third expansion device, the high-temperature outlet of the tower top condenser is connected with the low-temperature inlet of the first heat exchanger, and the low-temperature outlet of the first heat exchanger is connected with the low-temperature inlet of the second heat exchanger.
5. The cryogenic rectification system of claim 4 wherein the cryogenic cycle unit further comprises a second gas-liquid separator, a fourth expansion device and a third heat exchanger connected by piping; The low-temperature outlet of the second heat exchanger is connected with the inlet of the second gas-liquid separator, the air outlet of the second gas-liquid separator is connected with the high-temperature inlet of the third heat exchanger, the liquid outlet of the second gas-liquid separator is connected with the low-temperature inlet of the third heat exchanger through the fourth expansion device, the low-temperature outlet of the third heat exchanger is connected with the low-temperature inlet of the tower top condenser through the second expansion device, the high-temperature outlet of the tower top condenser is connected with the low-temperature inlet of the first heat exchanger, the low-temperature outlet of the first heat exchanger is connected with the low-temperature inlet of the third heat exchanger, and the high-temperature outlet of the third heat exchanger is connected with the low-temperature inlet of the second heat exchanger.
6. The cryogenic rectification system of claim 4 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 a feed conduit connected through the heat exchange channels to the feed inlet of the upper column.
7. The cryogenic rectification system of claim 4 further comprising an emergency unit comprising a second condenser, the first cryogenic outlet of the heat exchanger being selectively connectable to the inlet of the second condenser, the second condenser outlet being selectively connectable to the low temperature inlet of the overhead condenser.
8. The cryogenic rectification system of claim 1 wherein said rectification unit comprises six of said upper columns arranged in parallel, each of said upper columns being provided with a feed inlet, the refrigerant outlet of said cryogenic cycle unit being provided with a main pipe and six branch pipes connected to said main pipe, the six branch pipes being connected in one-to-one correspondence with the cryogenic inlets of the six of said overhead condensers.
9. The cryogenic rectification system of claim 8 wherein the main pipe is provided with a circulation pump.
10. The cryogenic rectification system of claim 1 wherein the column bottoms reboiler is provided with a discharge port.
11. A cryogenic rectification process employing the cryogenic rectification system of any one of claims 1to 10, the cryogenic rectification process comprising: delivering raw materials to a feed inlet of each upper tower; Injecting high-temperature refrigerant into the high-temperature circulation unit, injecting low-temperature mixed refrigerant into the low-temperature circulation unit, enabling the low-temperature mixed refrigerant to exchange heat with the high-temperature refrigerant through the evaporation condenser to absorb cold energy, and conveying the cold energy to the top condenser of each upper tower through a refrigerant outlet of the low-temperature circulation unit; The low-temperature mixed refrigerant discharged from the high-temperature outlet of the tower top condenser is conveyed to the first heat exchanger to exchange heat and absorb heat, then is compressed by the first compressor, and is conveyed to the intermediate reboiler to provide heat for the intermediate reboiler; delivering the low-temperature mixed refrigerant discharged from the low-temperature outlet of the intermediate reboiler to a second compressor for compression, and then delivering the refrigerant to the tower kettle reboiler for providing heat for the tower kettle reboiler; and the low-temperature refrigerant discharged from the low-temperature outlet of the tower kettle reboiler flows back to the low-temperature circulation unit through the first heat exchanger.

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 Light isotopes such as carbon (12C,13 C) and boron (10B,11 B) have important values that are not replaced in the fields of nuclear medicine, semiconductor industry, scientific research, and the like. Cryogenic rectification is one of the key technologies for separating these light isotopes. However, the biggest pain faced by this process is the extremely high production cost, which is mainly due to two aspects: (1) The separation difficulty is high, the relative volatility between the light isotopes is extremely low (very close to 1), and extremely high theoretical plate number and extremely high reflux ratio are required for realizing effective separation, so that the rectifying tower equipment is high and has remarkable energy consumption. (2) The energy cost is high, the rectification process needs to be carried out at extremely low temperature (for example, about-190 ℃ C. When 13 CO is separated and about-100 ℃ C. When 10BF3 is separated), and the investment and operation cost of a large refrigerating unit required for maintaining the low-temperature environment form the majority of the production cost. Accordingly, there is a need for a cryogenic rectification system that reduces energy consumption. Disclosure of Invention Based on the above shortcomings, the present application provides a cryogenic rectification system and a cryogenic rectification process that reduces energy consumption. 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 unit, a high temperature circulation unit, a low temperature circulation unit, and a thermal circulation unit. The rectification unit comprises a lower tower and a plurality of upper towers which are arranged in parallel, wherein the top of the lower tower is connected with the plurality of upper towers through an intermediate reboiler, and the bottom of the lower tower is provided with a tower kettle reboiler. The top of each upper tower is provided with a tower top condenser. The high temperature circulation unit is provided with a circulation passage for circulating a high temperature refrigerant, and the low temperature circulation unit is provided with a circulation passage for circulating a low temperature mixed refrigerant. The high-temperature refrigerant and the low-temperature mixed refrigerant exchange heat through the evaporative condenser. The refrigerant outlet of the low-temperature circulation unit is connected with the low-temperature inlet of the tower top condenser. The heat circulation unit comprises a first heat exchanger, a high-temperature outlet of the tower top condenser is connected with a low-temperature inlet of the first heat exchanger, the high-temperature outlet of the first heat exchanger is connected with a high-temperature inlet of an intermediate reboiler through the first compressor, the low-temperature outlet of the intermediate reboiler is connected with a high-temperature inlet of a tower kettle reboiler through the second compressor, and the low-temperature outlet of the tower kettle reboiler 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 refrigerant inlet of the low-temperature circulation unit. In the implementation process, compared with the method for directly realizing large-span cold energy by using a single refrigeration cycle unit, the low-temperature rectification system provided by the application has the advantages that the gradient cooling of refrigerants with different properties in the high-temperature cycle unit and the low-temperature cycle unit is utilized, so that the refrigeration capacity can be more efficiently provided for the rectification unit, the refrigeration efficiency is high, and the energy consumption can be reduced. In the low-temperature rectification system provided by the application, the refrigerant in a high-temperature state extracted from the high-temperature outlet of the tower top condenser is conveyed to the thermal circulation unit, preheated by the first heat exchanger and conveyed to the first compressor to be compressed into the refrigerant in a high-temperature and high-pressure state, and the refrigerant in the high-temperature and high-pressure state is used for providing energy for the intermediate reboiler to exchange heat with materials in the intermediate reboiler. After heat exchange is completed, the refrigerant is discharged from the intermediate reboiler, compressed and heated by the second compressor to obtain a high-temperature medium, the high-temperature medium is conveyed int