Patent Application
20250214027
The present disclosure relates to the technical field of wet carbon capture, in particular to a wet carbon capture process coupling water balance control with utilization of internal heat of a system.
Carbon emissions from low partial pressure gas sources are an indispensable part to be captured for achieving “carbon neutrality” since they account for 70% or higher of the total carbon dioxide to be captured in industry at present. Based on the existing engineering experience at home and abroad, it is the first choice to capture and recover carbon from low partial pressure gas sources on a large scale by using the wet process.
The wet process is still difficult to implement water balance control of a capture device or fully utilize internal heat besides degradation and volatilization loss of its essential absorbents. The existing process is restricted in flexibility of entire water balance control since water balance merely relies on a temperature difference of flue gas entering and leaving an absorption tower and temperatures of the flue gas leaving the absorption tower are tied to a temperature of cooling water and volatilization of the absorbent. Especially in recent years, water balance control of a traditional process has become increasingly hard after an introduction and use of a series of high-concentration absorbents such as phase change absorbents and low-moisture water absorbents. In addition, it is a pressing problem to implement the highly automated operation of a carbon capture device after engineering application, in which the water balance operation flexibility is an essential factor.
The water balance refers to the balance between the amount of moisture carried by a carbonaceous gas source into the carbon capture system and the amount of moisture carried by gas of a discharge system during the normal operation of the carbon capture device. Since the balance is very crucial to engineering, the fluctuation range and frequency of imbalance should be controlled to the maximum extent even if it is impossible to guarantee the dynamic balance all the time. With flue gas from a power plant as an example of a capture object, the flue gas usually contains saturated water vapor, and is cooled and purified by pretreatment systems such as a bath tower before entering the absorption tower. During cooling, continuous liquid discharge and alkali replenishment are required since part of water vapor will liquefy and remain in the bath tower and an alkali wash solution will consequently increase uninterruptedly in the bath tower. In this way, waste liquid discharge and consumption of alkali are both increased. In addition, the water balance control of an absorption-regeneration unit can merely rely on adjustment of temperatures of the flue gas entering and the absorption tower. Such adjustment is vulnerable to numerous factors, cannot be implemented in a wide range and is limited in extent consequently.
At present, the capture process of the wet device is mainly optimized from aspects of improvement in utilization of internal heat of the system and exertion of the maximum absorption efficiency of the absorbent, specifically, optimized temperature distribution of the absorption-regeneration unit, utilization of secondary steam in lean solution flash mechanical vapor recompression (MVR), and the recovery of heat from regeneration gas based on a heat pump principle. Despite that the methods can achieve certain results after being practiced in some devices, the utilization of regeneration gas heat is scarcely improved through the improvement and optimization of the process, and improvement in redundancy of the process and reduction of waste liquid discharge are rarely reported for the system water balance control.
In order to solve the problems in the prior art, the present disclosure provides a wet carbon capture process coupling water balance control with utilization of internal heat of a system, and a specific technical solution is as follows.
The wet carbon capture process coupling water balance control with utilization of internal heat of a system includes a pretreatment unit, an absorption unit, a regeneration unit, and a separation unit connected in sequence, wherein:
In some embodiments, the absorption unit includes:
In some embodiments, the recovery unit further includes:
In some embodiments, the regeneration unit includes:
The present disclosure has the following beneficial effects.
In the figures: 110: pretreatment tower; 120: wash water cooler; 210: absorption tower; 220: water wash solution cooler; 310: regeneration tower; 320: reboiler; 330: lean solution cooler; 340: lean-rich solution heat exchanger; 410: regeneration gas cooler; 420: gas-liquid separator; 510: regeneration gas washing tower; and 520: secondary washing tower.
In order to make objectives, technical solutions and advantages of examples of the present disclosure clearer, the technical solutions of the present disclosure will be clearly and completely described with reference to the examples.
The present disclosure provides a wet carbon capture process coupling water balance control with utilization of internal heat of a system.
It should be noted that all the one-way pipes outside the pretreatment tower are provided with pumps for driving the solution to flow. Meanwhile, with reference to
It should be noted that the water washing section and the alkali washing section are separated by a solution collection tray, the solution in the water washing section may be intercepted by the solution collection tray, and gas in the alkali washing section can enter the water washing section through the solution collection tray.
It should be noted that in the present disclosure, sodium hydroxide or sodium bicarbonate may be used as the alkali wash solution to deal with the flue gas. In some other examples, the alkali wash solution may be set specifically according to gas to be treated, which is not limitation to the present disclosure.
In the process, the flue gas enters from a gas inlet of the pretreatment tower 110, passes through the alkali washing section and the cooling section in turn, and then is discharged from a gas outlet. The flue gas is purified by the alkali washing section and cooled by the cooling section. In the present disclosure, a cooling structure of a traditional alkali wash solution is divided into the alkali washing section and the cooling section, and the alkali washing section merely removes impurities from the flue gas, such that it is no longer necessary to continuously replenish the pretreatment unit with alkali, and the consumption of the alkali is reduced.
With further reference to
It should be noted that in the present disclosure, a traditional organic amine absorbent represented by monoethanolamine, diethanolamine, aminomethyl propanol, piperazine, etc., may be selected as the absorbent. Amino acid salts such as potassium glycinate or phase change absorbents may also be used.
In the process, the flue gas discharged from the pretreatment tower 110 enters the absorption tower 210 and passes through the absorption section and the retention section in turn. The carbon dioxide in the flue gas may be absorbed by spraying of the absorption section. Since a part of the absorbent may evaporate and escape with the flue gas, and circulating water washing in the retention section may intercept the absorbent brought out by the flue gas by re-liquefying the absorbent, such that a loss of the absorbent is reduced.
In the process, the rich solution flowing out of the absorption tower 210 enters the regeneration tower 310 after passing through the lean-rich solution heat exchanger 340, and then converges and enters into the reboiler 320 through the one-way pipe outside the regeneration tower. Carbon dioxide and water in the rich solution are evaporated by the reboiler 320, and desorption is implemented. The desorbed high-temperature lean solution enters into the absorption tower 210 after passing through the lean-rich solution heat exchanger 340 and the lean solution cooler 330 in turn, thus forming recycling of the absorbent. In the present disclosure, the regeneration tower 310, the reboiler 320 and the lean solution cooler 330 desorb the absorbent to form the recycling of the absorbent. In addition, the lean solution heat exchanger 340 is configured to exchange heat between the low-temperature rich solution and the high-temperature lean solution; on one hand, the rich solution is heated to reduce a workload of reboiler 320, and on the other hand, the lean solution is cooled to reduce a workload of lean solution cooler 330.
It should be noted that the rich solution is a saturated absorbent and the lean solution is an unsaturated absorbent.
It should be noted that the reboiler 320 uses an external steam for heating, preferably a steam discharged from other combustion units.
With further reference to
It should be noted that the regeneration gas is a mixed gas of water vapor and carbon dioxide.
In the process, the regeneration gas cooler 410 may cool the water vapor, such that the water vapor in the regeneration gas is liquefied. A gas-liquid mixture is separated by the gas-liquid separator 420, such that a low-temperature regeneration gas of a mixture of the carbon dioxide and a part of the water vapor is discharged.
In the process, when the wash water in the water washing section of the pretreatment tower 110 overflows to a top of the regeneration gas washing tower 510 and is sprayed, the regeneration gas enters from a bottom of the regeneration gas washing tower 510 and exchanges heat with the wash water. Through a design of the regeneration gas washing tower 510, redundant wash water on the pretreatment tower 110 may be used to cool the regeneration gas discharged from the regeneration tower 310, the regeneration gas is precooled, and a workload of the regeneration gas cooler 410 is reduced. In addition, the secondary washing tower 520 secondarily sprays circularly wash water discharged from the regeneration gas washing tower 510 on the flue gas from the absorption tower 210, such that the wash water can be evaporated and discharged from the gas outlet of the secondary washing tower 520, and water balance is implemented. In addition, the wash water discharged from the regeneration gas washing tower 510 may be secondarily sprayed on the ex-tower flue gas out of the absorption tower 210 through the secondary washing tower 520, so that the wash water is evaporated and discharged from the gas outlet of the secondary washing tower 520, thus achieving water balance. Meanwhile, the wash water can intercept the absorbent escaping from the ex-tower flue gas out of the absorption tower secondarily to reduce the loss of the absorbent.
It should be noted that in specific process, a height of the solution outlet of the regeneration gas washing tower 510 may be set higher than that of the solution inlet of the secondary washing tower 520, such that the wash solution may directly flow into the secondary washing tower 520 by gravity.
The present disclosure has the following benefits.
Firstly, the wash water in an upper section of the pretreatment tower is sprayed on and cools the regeneration gas out of the regeneration tower for direct heat exchange, such that, heat exchange efficiency is improved and cooling water consumption of the regeneration gas cooler is reduced.
Secondly, due to a lower temperature of the upper section of the pretreatment tower, a large amount of condensed water is discharged in the form of steam through the secondary washing tower that is at a high temperature, such that wastewater discharge and alkali consumption of the pretreatment tower are greatly reduced.
Thirdly, through secondary washing of purified gas, the escape of the absorbent within the purified gas can be reduced.
Lastly, the operation flexibility of water balance control of the absorption tower is improved, that is, a temperature adjustment range of flue gas entering and leaving the capture system is greatly expanded, which can better ensure a solubility of the absorbent in the capture system.
A comparison of flue gas treatment based on the above carbon capture process in the present disclosure and that based on a traditional wet carbon capture process is shown in Table 1.
The above embodiments are merely used to illustrate the technical solution of the present disclosure rather than to limit same.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202311837562.7 | Dec 2023 | CN | national |
This application is a continuation of International Patent Application No. PCT/CN2024/077393, filed on Feb. 18, 2024, which claims priority of Chinese Patent Application No. 202311837562.7, filed on Dec. 28, 2023, the entire contents of each of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CN2024/077393 | Feb 2024 | WO |
| Child | 18797440 | US |
