CN-121988135-A - Regeneration system and process of carbon trapping absorbent

CN121988135ACN 121988135 ACN121988135 ACN 121988135ACN-121988135-A

Abstract

The invention discloses a regeneration system and a process of a carbon capture absorbent, wherein the system comprises the following components: the device comprises a lean-rich liquid heat exchanger, a desorber, a reboiler, a desorber air compressor unit, at least one set of steam CO 2 separation unit, a desorber air cooler, a gas-liquid separator and an absorbent cooler. The regeneration system and the process of the carbon trapping absorbent solve the problem of higher energy consumption of a desorption unit in the CO 2 trapping process by a chemical absorption method.

Inventors

ZHOU HUAQUN
GAO FEI
WANG RUOXIN
LIU TAORAN
LIU YILONG
SHI WEN
LI YINGWEN
LIU KEFENG
DONG WEIGANG
CAI YONG

Assignees

中国石油天然气股份有限公司

Dates

Publication Date: 20260508
Application Date: 20241107

Claims (9)

1. A regeneration system of a carbon capture absorbent is characterized by comprising a lean-rich liquid heat exchanger, a desorber, a reboiler, a desorption gas compressor unit, at least one set of steam CO 2 separation unit, a desorption gas cooler, a gas-liquid separator and an absorbent cooler, wherein the bottom of the desorber is connected with the reboiler and is provided with liquid and gas channels, a gas discharge port at the top of the desorber is connected with an inlet of the desorption gas compressor unit, compressed gas is connected with the steam CO 2 separation unit, the steam CO 2 separation unit is provided with two gas outlets, a first gas outlet is connected with the desorption gas cooler or the desorption gas compressor unit, a second gas outlet is connected with a gas inlet of the desorber or the reboiler, the desorption gas cooler is connected with the gas-liquid separator through a gas-liquid two-phase pipeline, the absorbent to be regenerated is mainly separated into a regenerated absorbent and crude CO 2 product gas through the regeneration system of the carbon capture absorbent, liquid discharge ports of the absorber and the lean-rich liquid heat exchanger are respectively connected with the lean-rich liquid heat exchanger, and the lean-rich liquid heat exchanger is cooled after being cooled, and the lean-liquid heat exchanger is connected with the heat exchanger heat exchange and the heat exchanger heat exchange is cooled.
2. The regeneration system of a carbon capture absorbent according to claim 1, wherein the desorption gas compressor unit comprises at least one desorption gas compressor, when the compression ratio is not high, one single-stage compression is used, one desorption gas compressor is arranged in the desorption gas compressor unit, one end of the desorption gas compressor is connected with a top gas phase pipeline of the desorber, the other end of the desorption gas compressor is combined with an inlet of a steam CO 2 separation unit, when the compression ratio is high, multi-stage compression is used, two or more desorption gas compressors are arranged in the desorption gas compressor unit, when the single-stage compression is used, the desorption gas generated by compression is separated by the steam CO 2 separation unit to obtain a rich vapor gas and a rich CO 2 gas, the rich vapor gas is directly fed into the desorber or the reboiler as a heat source to be subjected to subsequent cooling and gas-liquid separation, when the multi-stage compression is used, the desorption gas generated by the previous-stage desorption gas compressor unit and the steam CO 2 separation unit is combined with the inlet of the steam CO 2 separation unit, and the rich vapor gas generated by the previous-stage desorption gas compressor is fed into the steam CO 5629 separation unit as a heat source or the rich CO gas is further compressed by the steam compressor unit to obtain the rich vapor gas which is fed into the one-stage compression device or the high-stage compression device.
3. The regeneration system of a carbon capture absorbent according to claim 1, wherein the steam CO 2 separation unit comprises a phase change heat exchanger, a secondary cooler, a flash tank and a pressure reducing device, wherein the desorption gas generated by the desorption gas compressor unit is cooled in the phase change heat exchanger and the secondary cooler, part of water vapor is condensed, CO 2 -rich gas and condensed water are separated, the condensed water is returned to the phase change heat exchanger after being decompressed, and the condensed water is subjected to secondary vaporization and is converted into water vapor-rich gas after receiving heat of high-temperature gas.
4. The regeneration system of a carbon capture absorbent according to claim 1, wherein the vapor CO 2 separation unit comprises 2 phase-change heat exchangers, 2 phase-change heat exchangers are connected in series, the desorption gas compressor unit is sequentially connected with the 2 phase-change heat exchangers and exchanges heat with condensed water from a flash tank and a gas-liquid separator respectively, a hot outlet of the phase-change heat exchanger is a gas-liquid two-phase pipeline and is connected with the flash tank, a gas outlet of the flash tank is connected with a compressor or a desorption gas cooler, a liquid outlet of the flash tank is connected with a cold feed inlet of a first phase-change heat exchanger after passing through a pressure reducing device, heat exchange is carried out between the desorption gas and the condensed water of the flash tank in the first heat exchanger, the condensed water is separated from a second gas outlet after vaporization, the liquid outlet of the gas-liquid separator is divided into two paths, wherein one path is connected with a cold feed inlet of the second phase-change heat exchanger, the condensed water is subjected to heat exchange by desorption gas-liquid separator in the second phase-change heat exchanger, and enters a cold feed inlet of the first heat exchanger after heat exchange.
5. The carbon capture absorbent regeneration system of claim 1 wherein the liquid outlet line of the gas-liquid separator is split into two paths, one of which is connected to the inlet of the desorber compressor train, and liquid is introduced into the desorber compressor train using a liquid spray device.
6. The carbon capture absorber regeneration system of claim 5 wherein the vapor-rich gas recovered in the stripping gas is used as a heat source to enter the reboiler or to enter the desorber.
7. A process for regenerating a carbon capture absorbent, comprising the steps of: s1, carrying out heat exchange on an absorbent rich solution to be regenerated and a desorbed absorbent lean solution; S2, the absorbent rich liquid enters a desorber to be desorbed after heat exchange, the desorption pressure is recorded as p0, the purpose of desorption is achieved by heat supply of a reboiler, and the reboiling temperature is recorded as T0; S3, pressurizing the desorption gas by a desorption gas compressor unit, wherein the pressure is recorded as p1, the range of p1-p0 is 0.3-0.8 MPa, and separating the pressurized desorption gas by a steam CO 2 separation unit to obtain CO 2 -rich gas and steam-rich gas, wherein the steam-rich gas returns to a desorber or a reboiler for heating; S4, the rich steam from the step S3 is combined, steam generated by a reboiler is fed into a desorber to contact with a liquid absorbent, CO 2 is desorbed from the absorbent, the steam is partially condensed from a gas phase, and phase change latent heat generated by the steam condensation provides heat required by a desorption process; and S5, returning the desorbed absorbent lean solution to the step S1 to exchange heat with the absorbent rich solution to be regenerated, and cooling by a cooler to complete the regeneration process.
8. The process for regenerating a carbon capture absorber of claim 7, wherein the absorber comprises an aqueous solution of one or more of Monoethanolamine (MEA), piperazine (PZ), N-Methyldiethanol (MDEA).
9. The process for regenerating a carbon capture absorber according to claim 7, wherein the pressure p1 of the desorption gas after pressurization by the desorption gas compressor unit is 0.3 to 0.8mpa.

Description

Regeneration system and process of carbon trapping absorbent Technical Field The invention relates to the technical field of carbon dioxide trapping, in particular to a device and a method for trapping carbon dioxide in flue gas by a chemical absorption method. Background The carbon dioxide trapping technology by the chemical absorption method is the most main technical route of the current low-concentration flue gas carbon dioxide trapping, and one of the main problems of the technology is high energy consumption, wherein the energy consumption is mainly concentrated in the regeneration step of the absorbent. The absorbent regeneration generally adopts a heating desorption mode, and the energy consumption mainly comprises three parts, namely sensible heat difference between discharge and feed of a desorption unit, reaction heat of CO 2 in the absorbent, and latent heat taken away by partial water evaporation during desorption. Among them, reducing the latent heat consumption of water is one of the important directions of optimizing and improving the process flow of various CO 2 capturing technologies by chemical absorption methods. The method reduces the water vapor content in the desorption gas from the technical aspect, and comprises the steps of improving the performance of an absorbent, reducing the water partial pressure of rich liquid, improving the absorption load, improving the pressure in the desorption process, segmenting the desorption process, exchanging heat between the desorption gas and the rich liquid feed, and the like, so that the water vapor content in the desorption gas can be reduced to a certain extent. CN202311603870.3 discloses a scheme combining desorption process optimization and process strengthening, controlling rich bubble point feeding during desorption, so that the content of water vapor in desorption gas can reach the theoretical minimum value, and the comprehensive better effect can be achieved by combining microwave heating or supergravity technology. From the aspect of desorption balance, after the load of the absorbent is determined and the desorption temperature and pressure are determined, the H 2O/CO2 ratio in the desorption gas can be optimized to the minimum value, but a large amount of water vapor still exists under the working condition. The heat of the desorption gas is utilized after the temperature level of the desorption gas is improved by adopting related measures, so that the latent heat of the water vapor in the desorption gas can be further recovered, and a desorption gas direct compression scheme, an absorption heat pump scheme, a compression heat pump scheme and the like are mainly adopted at present. Chinese patent CN202320948542.6 proposes an absorption heat pump scheme using the desorber heat for intermediate heating of the desorber or reboiler heating at the bottom of the column. Chinese patent CN201410182689.4 discloses a heat pump scheme that can use the heat of regenerated lean liquor and desorbed gas for reboiler or regenerator feed. In the scheme disclosed in chinese patent CN20151 0394519.7, the desorption gas is compressed to raise the temperature and then supplied to the second reboiler. The common characteristics of the above technical schemes are that the heat of the stripping gas at a lower temperature is used for the heating requirement of the stripping gas at a higher temperature, so that the latent heat in the stripping gas is recovered, the difference of the technical schemes mainly lies in the difference of the efficiency of the compression or absorption heat pump, and the difference of the recovered heat is used for heating a reboiler or the rich liquid feed, namely, the heat exchange flow is different. The heat pump type technical scheme has the main problems that the heat efficiency is low, particularly when the heat pump type heat pump is used for heating a reboiler with a higher temperature, the heat efficiency is only about 1.2 by taking an absorption heat pump as an example, the heat recovery quantity exceeds the required heat quantity of the reboiler, and low-temperature heat is transferred to a material flow to be heated in a heat exchange mode, and a certain heat transfer temperature difference is necessarily required in the middle, so that the heat utilization is insufficient. Another technical solution for reducing the heat loss of desorption gas is to use a direct steam stripping method. The traditional desorption process uses steam for heat supply, a part of heat is used for vaporization of water in the absorbent, and a direct steam stripping method is used for vaporization of water vapor without additional heat, so that the problem of latent heat loss of desorption gas is thoroughly solved. The papers of chemical industry progress 2018, dynamics engineering 2015, 35 volumes and the like describe the direct steam process and the advantages thereof in detail, and the method has obvious energy-saving effect. However, the s