Multi-stage ammonia process decarbonation method

Abstract

The present invention relates to a method for multi-stage ammonia process decarbonation, which comprises removing CO from a process gas using ammonia as an absorbent in an absorber having four or more stages of absorption, the first stage of absorption, the second stage of absorption, the third stage of absorption, the fourth stage of absorption, and any higher stage of absorption being arranged in sequence along the flow direction of the process gas. 2 and controlling the temperature of the process gas in the second and third stages of absorption to be equal to or greater than the temperature of the process gas in the first stage of absorption and controlling the temperature of the process gas in the fourth and any higher stages of absorption to be less than the temperature of the process gas in the first stage of absorption.

Description

[Technical field]

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims priority to and the benefit of Chinese Patent Application No. 202210553333.1, filed on May 20, 2022, the disclosure of which is incorporated herein by reference in its entirety. The present invention relates to the technical field of environmental protection, in particular to the CO 2 The present invention relates to a multi-stage decarbonation method having improved capture efficiency. [Background technology]

[0002] Climate warming is an issue that affects the development of all humankind, and CO 2 is the main cause of climate warming. Industrial gases produced during chemical production contain large amounts of carbon dioxide. 2 In order to control emissions on a large scale and combat global warming, 2 Therefore, the focus needs to shift to developing technologies that can capture these compounds efficiently.

[0003] The chemical absorption method, which uses aqueous ammonia as the absorbing liquid, has the characteristics of strong absorption capacity, low corrosion, low energy consumption for regeneration, low replenishment cost, the absorbent is not easily decomposed by other components in the flue gas, and multiple acid gas pollutants can be removed simultaneously, and has been widely studied by engineers at home and abroad.

[0004] Chinese Patent No. 102078743 describes an improved CO2 ion exchanger that contains an ammonia carbonate solution and an additive. 2 An inorganic absorbent is disclosed. The total ammonia mass fraction of the ammonia carbonate solution is 4%-12%, the additive is sodium phosphate or potassium phosphate, the ratio of the molar concentration of the additive to the total ammonia molar concentration of the ammonia carbonate solution is 0.04-0.20, and the balance is deionized water. This invention is 2Controlling the composition of the inorganic sorbent improves the decarbonation efficiency and reduces ammonia leakage. However, the use of additives can affect the product purity of ammonium bicarbonate.

[0005] China Patent Publication No. 102688676 discloses an ammonia process decarbonation method for power plant flue gas. After the flue gas is cooled to 45°C-55°C by desulfurization and dust removal, it enters the decarbonation absorption tower, where it comes into countercurrent contact with the absorbing liquid, where the CO in the flue gas is decarbonated. 2 The total ammonia mass fraction of the absorption liquid is controlled to 3%-5% so that CO 2 After absorbing CO, the rich solution is introduced into the regeneration tower and heated to produce CO. 2 The desorption temperature here is 85°C to 95°C. The absorption liquid then returns to the decarbonation and absorption tower to start a new absorption. Sodium bicarbonate or potassium bicarbonate is added to the absorption liquid, and the concentration of the added sodium bicarbonate or potassium bicarbonate is 0.1 mol / L to 0.5 mol / L. This technology is characterized by high CO 2 Desorption rate and CO in the absorption liquid in the recycle process 2 Keep the load constant and CO 2 This is an ammonia process decarbonation method for power plant flue gas, which ensures the absorption capacity of the solution for

[0006] China Patent Publication No. 103007719 discloses a flue gas double circulation ammonia process decarbonation device, which is designed with two circulation zones in which solid products are separated from the bottom, to solve the problems of the existing device for absorbing carbon dioxide in power plant flue gas in ammonia process, that is, the absorption rate is not high and the device is prone to clogging. This device proposes to solve the problem of solid clogging by simply providing two circulation zones, without considering the relationship between the ammonia process decarbonation absorption and temperature control.

[0007] Chinese Patent Application No. 200880122376.2 describes a multi-stage CO2 filtration system for treating a flue gas stream. 2 A removal system and method is disclosed. Through the use of an absorber container, the flue gas stream is contacted with an ionic solution containing ammonia under low temperature conditions between 0°C and 20°C, the solution in the first absorption stage having a higher temperature and a lower ammonia-to-carbon ratio than the solution in the third absorption stage. Ammonia leakage can be reduced by controlling the low temperature and making the third stage a lower temperature. However, a higher ammonia-to-carbon ratio in the third stage increases ammonia leakage.

[0008] Therefore, there remains a need for an ammonia process decarbonation method that exhibits high absorption efficiency and can effectively control ammonia leakage. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Chinese Patent No. 102078743 [Patent Document 2] China Patent Application Publication No. 102688676 [Patent Document 3] China Patent Application Publication No. 103007719 [Patent Document 4] Chinese Patent Application No. 200880122376.2 Summary of the Invention

[0010] The present inventors have conducted extensive research to solve the problems of low absorption efficiency and serious ammonia leakage in the existing ammonia-based decarbonation process. As a result, they have found that by providing four or more absorption stages and controlling the temperature profile of each absorption stage, optionally in combination with the control of ammonia addition, high absorption efficiency and effective ammonia leakage control in the ammonia-based decarbonation process can be achieved, and the present invention has been completed.

[0011] Therefore, an object of the present invention is a method for multi-stage ammonia process decarbonation, which comprises the steps of: decarbonating CO from a process gas using ammonia as absorbent in an absorber with four or more absorption stages, the first absorption stage, the second absorption stage, the third absorption stage, the fourth absorption stage and any higher absorption stage being arranged in sequence along the flow direction of the process gas. 2 and controlling the temperature of the process gas in the second and third stage absorptions to be equal to or greater than the temperature of the process gas in the first stage absorption and controlling the temperature of the process gas in the fourth and any higher stage absorptions to be less than the temperature of the process gas in the first stage absorption.

[0012] The method of the present invention can effectively reduce energy consumption, increase absorption efficiency, and effectively control ammonia leakage.

[0013] A further object of the invention is to provide an apparatus for carrying out the method of the invention, comprising: a first stage absorption vessel, a second stage absorption vessel, a third stage absorption vessel, a fourth stage absorption vessel, and any higher stage absorption vessels, arranged in sequence along a flow direction of a process gas; an ammonia addition section configured to supply an ammonia absorbent to one or more of the absorption vessels; and temperature control means configured to control the temperature of the process gas in the second and third stage absorption vessels to be equal to or greater than the temperature of the process gas in the first stage absorption vessel, and to control the temperature of the process gas in the fourth and any higher stage absorption vessels to be less than the temperature of the process gas in the first stage absorption vessel. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram of an ammonia process decarbonation unit according to some embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] In a first aspect, the disclosure provides a method for multi-stage ammonia process decarbonation, comprising the steps of: removing CO from a process gas using ammonia as an absorbent in an absorber having four or more stages of absorption, the first stage of absorption, a second stage of absorption, a third stage of absorption, a fourth stage of absorption, and any higher stage of absorption arranged in sequence along the flow direction of the process gas; 2 and controlling the temperature of the process gas in the second and third stage absorptions to be equal to or greater than the temperature of the process gas in the first stage absorption and controlling the temperature of the process gas in the fourth and any higher stage absorptions to be less than the temperature of the process gas in the first stage absorption.

[0016] As will be appreciated by those skilled in the art, water can be used as the absorption medium in the methods of the present disclosure.

[0017] In some embodiments, the temperature of the process gas in the second and third stages of absorption is controlled to be at least 1° C., preferably at least 2° C., more preferably at least 3° C. higher than the temperature of the process gas in the first stage. Preferably, the temperature of the process gas in the second and third stages of absorption is controlled to be no more than 30° C., preferably no more than 25° C., more preferably no more than 20° C. higher than the temperature of the process gas in the first stage of absorption.

[0018] In some embodiments, the temperature of the process gas in the fourth stage and any higher stage absorption is controlled to be at least 1° C., preferably at least 2° C., more preferably at least 3° C. lower than the temperature of the process gas in the first stage absorption. Preferably, the temperature of the process gas in the fourth stage and any higher stage absorption is controlled to be 25° C. or less, preferably 20° C. or less, more preferably 15° C. or less lower than the temperature of the process gas in the first stage absorption.

[0019] In this method, ammonia is added in multiple stages in the absorber, and the amount of ammonia added to the circulating liquid in the final stage of decarbonation absorption is less than that in the previous stage, or no ammonia is added to the circulating liquid in the final stage of decarbonation absorption. The addition of ammonia to the absorption circulating liquid may result in the formation of carbamates or carbonates. Therefore, such a method of ammonia addition, i.e., adding less ammonia to the circulating liquid in the final stage of decarbonation absorption than that in the previous stage, or no ammonia is added to the circulating liquid in the final stage of decarbonation absorption, is advantageous in suppressing the formation of carbamates or carbonates and controlling ammonia leakage.

[0020] In some embodiments, the amount of ammonia added to the circulating liquid in the final stage of decarbonation absorption is 20 wt % or less, preferably 10 wt % or less, more preferably 5 wt % or less, and even more preferably 0 wt % of the total amount of ammonia added in the entire process.

[0021] In some embodiments, the temperature of the process gas in the second stage absorption and the temperature of the process gas in the third stage absorption are controlled to be the same.

[0022] In some embodiments, the temperature of the process gas in the second stage absorption is controlled to be, for example, at least 1° C., or 2° C., or 3° C. lower than the temperature of the process gas in the third stage absorption.

[0023] In some embodiments, the temperature of the process gas in the first stage absorption is controlled to be in the range of 10°C to 30°C, the temperature of the process gas in the second and third stages absorption is controlled to be in the range of 15°C to 35°C, and the temperature of the process gas in the fourth and any higher stages absorption is controlled to be in the range of 5°C to 25°C, with the proviso that the temperature of the process gas in the second and third stages absorption is equal to or greater than the temperature of the process gas in the first stage absorption, and the temperature of the process gas in the fourth and any higher stages absorption is less than the temperature of the process gas in the first stage absorption.

[0024] In some embodiments, the methods of the present disclosure include controlling the temperature of the process gas and / or the amount of ammonia added in the first stage absorption to promote the production of ammonium bicarbonate in the first stage absorption.

[0025] In some embodiments, multi-stage ammonia addition is performed in the absorber, and the amount of ammonia added to the circulating liquid in the first stage of decarbonation absorption is less than the amount of ammonia added to the circulating liquid in the second stage of decarbonation absorption, or no ammonia is added to the circulating liquid in the first stage of decarbonation absorption. The amount of ammonia added to the circulating liquid in the first stage of decarbonation absorption is preferably 70% by weight or less, for example, 50% by weight or less, 30% by weight or less, or 10% by weight or less of the amount of ammonia added to the circulating liquid in the second stage of decarbonation absorption. Such an ammonia addition method can be useful for increasing the production of ammonium bicarbonate.

[0026] In some embodiments, the method of the present disclosure further includes collecting the ammonium bicarbonate solution or slurry in the first stage absorption and producing solid ammonium bicarbonate from the solution or slurry.

[0027] In some embodiments, a multi-stage absorption system of absorbers is combined into one or more towers, with devices / components that allow gas to pass through being positioned between the stages.

[0028] In some embodiments, at least one layer of circulating liquid distributor is disposed at each stage of absorption.

[0029] In some embodiments, at least one layer of gas-liquid contacting element is disposed at each stage of absorption, which gas-liquid contacting element is preferably packing.

[0030] In some embodiments, the method of the present disclosure further includes reducing the temperature of the circulating liquid supplied to the stage by use of a heat exchanger, and reducing the temperature of the process gas by spraying the process gas with the circulating liquid.

[0031] In the method of the present disclosure, among the multiple stages of absorption liquid used in sequence along the flow direction of the process gas, the absorption liquid in the preceding stage is replenished with the absorption liquid in the immediately succeeding stage, and the absorption liquid in the final stage is replenished with water.

[0032] In a second aspect, the present disclosure provides an apparatus for carrying out the method of the present invention, comprising: a first stage absorption vessel, a second stage absorption vessel, a third stage absorption vessel, a fourth stage absorption vessel, and any higher stage absorption vessels, arranged in sequence along a flow direction of a process gas; an ammonia addition section configured to supply an ammonia absorbent to one or more of the absorption vessels; temperature control means for controlling the temperature of the process gas in the second and third stages of absorption above the temperature of the process gas in the first stage of absorption and for controlling the temperature of the process gas in the fourth and any higher stages of absorption below the temperature of the process gas in the first stage of absorption; The present invention provides an apparatus comprising:

[0033] In some embodiments, in the apparatus of the present disclosure, the ammonia addition unit is configured to supply ammonia absorbent to multiple absorption vessels such that the amount of ammonia added to the decarbonation circulating liquid in the final absorption vessel is less than the amount of ammonia added in the previous stage, or such that no ammonia is added to the decarbonation circulating liquid in the final absorption vessel.

[0034] In some embodiments, in the apparatus of the present disclosure, the ammonia addition unit is configured to supply ammonia absorbent to the multiple absorber stages such that the amount of ammonia added to the decarbonation circulating liquid in the first absorber stage is less than the amount of ammonia added in the second stage, or such that no ammonia is added to the decarbonation circulating liquid in the first stage.

[0035] In some embodiments, in the apparatus of the present disclosure, the temperature control means is configured to control the temperature of the process gas in the second and third stage absorption to be the same.

[0036] In some embodiments, in the apparatus of the present disclosure, the temperature control means is configured to control the temperature of the process gas in the second stage absorption to be less than the temperature of the process gas in the third stage absorption.

[0037] In some embodiments, in the apparatus of the present disclosure, the temperature control means is configured to control the temperature of the process gas in the first stage of absorption to be in the range of 10°C to 30°C, the temperature of the process gas in the second and third stages of absorption to be in the range of 15°C to 35°C, and the temperature of the process gas in the fourth and any higher stages of absorption to be in the range of 5°C to 25°C, with the proviso that the temperature of the process gas in the second and third stages of absorption is equal to or greater than the temperature of the process gas in the first stage of absorption, and the temperature of the process gas in the fourth and any higher stages of absorption is less than the temperature of the process gas in the first stage of absorption.

[0038] In some embodiments, the apparatus of the present disclosure further comprises an ammonium bicarbonate post-treatment section configured to receive the ammonium bicarbonate solution or slurry from the first stage absorption and produce solid ammonium bicarbonate therefrom.

[0039] In some embodiments, in the apparatus of the present disclosure, multiple stages of absorption vessels are combined into one or more towers, with equipment / components that allow gas to pass through being placed between the stages.

[0040] In some embodiments, in the apparatus of the present disclosure, at least one layer of circulating liquid distributor is disposed in each stage of absorption.

[0041] In some embodiments, in the apparatus of the present disclosure, at least one layer of gas-liquid contacting component, such as packing, is disposed in each stage of absorption.

[0042] In some embodiments, in the apparatus of the present disclosure, among the multiple stages of absorption liquid used in sequence along the flow direction of the process gas, the absorption liquid in the preceding stage is replenished with the absorption liquid in the immediately succeeding stage, and the absorption liquid in the final stage is replenished with water.

[0043] An exemplary embodiment of the apparatus / method of the present invention will now be described with reference to the accompanying drawings. A process gas 1 containing carbon dioxide enters an absorber 2 and first undergoes first stage absorption 3. The liquid is pumped to the top of the first stage by the first stage circulation pump 4, flows through the first stage packing 5 to contact the process gas, and then returns to the bottom of the first stage. The first stage circulation liquid is cooled by a heat exchanger 31, and the temperature of the process gas decreases after the circulation liquid contacts the process gas. Ammonia 27 is added to the first stage absorption liquid through a pipe, and carbon dioxide in the process gas is absorbed by gas-liquid contact. The process gas after the first stage absorption and cooling enters the second stage absorption through a liquid collector 6, and the process process in the second stage is the same as that in the first stage. The second stage absorption liquid overflows into the first stage absorption. The process gas after the second stage absorption and cooling enters the third stage absorption through the liquid collector 10, and the process of the third stage is the same as that of the first stage. The third stage absorption liquid overflows into the second stage absorption. The treated process gas then passes through the similar third stage absorption, fourth stage absorption, fifth stage absorption, and sixth stage absorption in sequence.

[0044] The ammonium bicarbonate solution / slurry is discharged from the bottom of the first stage absorption via a pump (not shown) for the production of solid ammonium bicarbonate.

[0045] Make-up water 29 for this system is fed to the sixth stage of absorption. A demister is located at the top of the sixth stage of absorption, and demisted process gas is discharged overhead. EXAMPLES

[0046] Example 1 Ammonia process decarbonation was carried out using the apparatus shown in the accompanying drawing.

[0047] In this method, the amount of ammonia added to the absorption liquid in the first stage was 2% by weight of the total amount of ammonia added, the amount of ammonia added to the absorption liquid in the second stage was 8% by weight of the total amount of ammonia added, the amount of ammonia added to the absorption liquid in the third stage was 40% by weight of the total amount of ammonia added, the amount of ammonia added to the absorption liquid in the fourth stage was 40% by weight of the total amount of ammonia added, the amount of ammonia added to the absorption liquid in the fifth stage was 10% by weight of the total amount of ammonia added, and no ammonia was added to the absorption liquid in the sixth stage.

[0048] The temperatures in the individual absorption stages were controlled as follows: 1st stage: 25℃ 2nd stage: 30℃ 3rd stage: 33℃ 4th stage: 22℃ 5th stage: 22℃ 6th stage: 22℃

[0049] 99.6% liquid ammonia was used as the absorbent for decarbonation. The parameters of the process gas before decarbonation are shown in the table below.

[0050] [Table 1]

[0051] The main parameters after treatment by the decarbonation tower are shown in the table below.

[0052] [Table 2]

[0053] Comparative Example 1 The only difference compared to Example 1 was the addition of ammonia. Ammonia was added to all decarbonation and absorption zones from the first stage to the sixth stage, and the amount of ammonia added in the six stages was the same.

[0054] Because the amount of ammonia added in the first stage decarbonation absorption zone reached 16.7%, it became difficult to produce ammonium hydrogen carbonate in the solution, and ammonium hydrogen carbonate crystals could not be obtained. The amount of ammonia added in the sixth stage decarbonation absorption zone reached 16.7%, and the amount of ammonia leakage for decarbonation increased significantly, and the amount of ammonia leakage in the process gas after decarbonation reached a maximum of 5000 ppm. Therefore, the subsequent ammonia removal section had an increased ammonia removal load.

[0055] The main parameters of the gas after decarbonation are shown in the table below.

[0056] [Table 3]

[0057] Comparative Example 2 The only difference compared to Example 1 was the temperature control. The temperature of the first stage decarboxylation and absorption region was 25°C, and the temperatures of the second to sixth stages decarboxylation and absorption regions were the same, all set at 22°C.

[0058] The second and third stage decarbonation absorption regions are controlled at a relatively low temperature, and the temperature difference with the cold heat source is small, so the heat exchange area required for the heat exchangers 32 and 33 is larger than that of Example 1, resulting in increased capital investment costs. In addition, when the ambient temperature is 22°C, the cold heat source used for the heat exchangers 32 and 33 for the second and third stage decarbonation absorption regions of Example 1 can be low-temperature ambient air cooled by an air cooler, thereby saving operating costs. In Comparative Example 2, since the ambient temperature and the target temperature are set to the same 22°C, cooling by an air cooler is not possible, and cold water, which consumes a lot of energy, is used for cooling. [Explanation of symbols]

[0059] The symbols in FIG. 1 have the following meanings: 1 Process gas 2. Absorber 3 Absorption in the first stage of the absorber 4. First stage circulation pump 5. First stage packing 6 First stage liquid collector 7 Second stage circulation pump 8 Absorption of the second stage of the absorber 9 Second stage packing 10 Second stage liquid collector 11 Third stage circulation pump 12 Absorption of the third stage of the absorber 13 Third stage packing 14 Third stage liquid collector 15 Fourth stage circulation pump 16 Absorption of the fourth stage of the absorber 17 Fourth stage packing 18 Fourth stage liquid collector 19 5th stage circulation pump 20 Absorption of the fifth stage of the absorber 21 5th stage packing 22 Fifth Stage Liquid Collector 23 6th stage circulation pump 24 6th stage packing 25 Absorption of the sixth stage of the absorber 26 Demistar 27 Ammonia 28 Ammonium bicarbonate solution / slurry 29 Makeup water 30 Decarbonated gas 31 First stage heat exchanger 32 Second stage heat exchanger 33 Third stage heat exchanger 34 4th stage heat exchanger 35 5th stage heat exchanger 36 6th stage heat exchanger

Claims

1. 1. A method for multi-stage ammonia process decarbonation comprising: In an absorber having four or more absorption stages, in which a first absorption stage, a second absorption stage, a third absorption stage, a fourth absorption stage, and any higher absorption stage are arranged in this order along the flow direction of the process gas, CO is extracted from the process gas using ammonia as an absorbent. ２ Absorbing and controlling the temperature of the process gas in said second stage absorption and said third stage absorption to be equal to or greater than the temperature of the process gas in said first stage absorption and controlling the temperature of the process gas in said fourth stage absorption and any higher stage absorption to be less than the temperature of the process gas in said first stage absorption.

2. Features: Ammonia is added in multiple stages in the absorber, and the amount of ammonia added to the circulating liquid in the final stage of the decarbonation and absorption is made smaller than the amount of ammonia added to the circulating liquid in the previous stage, or ammonia is not added to the circulating liquid in the final stage of the decarbonation and absorption. Adding ammonia in multiple stages in the absorber, and making the amount of ammonia added to the circulating liquid in the first stage of decarbonation and absorption less than the amount of ammonia added to the circulating liquid in the second stage of decarbonation and absorption, or not adding ammonia to the circulating liquid in the first stage of decarbonation and absorption; The method of claim 1 , comprising at least one of:

3. Features: the temperature of the process gas in the second absorption stage and the temperature of the process gas in the third absorption stage are controlled to be the same, or the temperature of the process gas in the third absorption stage is controlled to be higher than the temperature of the process gas in the second absorption stage; the temperature of the process gas in the first stage absorption is controlled to be in the range of 10°C to 30°C; the temperature of the process gas in the second and third stages of absorption is controlled to be in the range of 15°C to 35°C; the temperature of the process gas in the fourth stage and any higher stage absorption is controlled to be in the range of 5° C. to 25° C.; with the proviso that the temperature of the process gas in the second and third stages of absorption is equal to or greater than the temperature of the process gas in the first stage of absorption and the temperature of the process gas in the fourth and any higher stages of absorption is less than the temperature of the process gas in the first stage of absorption.

4. Features: controlling the temperature of the process gas in the first stage absorption and the amount of ammonia added to the first stage absorption to promote the production of ammonium bicarbonate in the first stage absorption; collecting the ammonium bicarbonate solution or slurry from said first stage absorption and using it to produce solid ammonium bicarbonate from the ammonium bicarbonate solution or slurry; The method of claim 1 , comprising at least one of:

5. Features: the absorber is combined into one or more columns, and devices / components allowing the passage of gas are arranged between the stages; At least one circulating liquid distributor is disposed at each stage of the absorption; at least one layer of gas-liquid contacting element is disposed at each stage of absorption, the gas-liquid contacting element being preferably a packing; reducing the temperature of the circulating liquid using a heat exchanger and atomizing the circulating liquid to reduce the temperature of the process gas; Among the absorption liquids in multiple stages used in sequence along the flow direction of the process gas, the absorption liquid in the preceding stage is replenished with the absorption liquid in the immediately succeeding stage, and the absorption liquid in the final stage is replenished with water; The method of claim 1 , comprising at least one of:

6. An apparatus for carrying out the method according to any one of claims 1 to 5, comprising: a first stage absorber, a second stage absorber, a third stage absorber, a fourth stage absorber and any higher stage absorbers; an ammonia addition section configured to supply an ammonia absorbent to one or more of the absorption vessels; temperature control means for controlling the temperature of the process gas in said second and third stages of absorption above the temperature of the process gas in said first stage of absorption and for controlling the temperature of the process gas in said fourth and any higher stages of absorption below the temperature of the process gas in said first stage of absorption; An apparatus comprising:

7. Features: The ammonia addition unit is configured to supply an ammonia absorbent to the multi-stage absorption so that the amount of ammonia added to the decarbonation circulation liquid in the final stage absorption is less than the amount of ammonia added in the immediately preceding stage, or so that ammonia is not added to the decarbonation circulation liquid in the final stage absorption; the ammonia addition unit is configured to supply an ammonia absorbent to the multi-stage absorption so that an amount of ammonia added to the decarbonation circulating liquid in the first stage absorption is less than an amount of ammonia added to the decarbonation circulating liquid in the second stage absorption, or so that ammonia is not added to the decarbonation circulating liquid in the first stage absorption; the temperature control means is configured to control the temperatures of the process gas in the second and third absorption stages to be the same, or the temperature control means is configured to control the temperature of the process gas in the second absorption stage to be lower than the temperature of the process gas in the third absorption stage; said temperature control means is configured to control the temperature of the process gas in said first stage absorption to be in the range of 10°C to 30°C, to control the temperature of the process gas in said second and third stages absorption to be in the range of 15°C to 35°C and to control the temperature of the process gas in said fourth and any higher stages absorption to be in the range of 5°C to 25°C, with the proviso that the temperature of the process gas in said second and third stages absorption is equal to or greater than the temperature of the process gas in said first stage absorption and the temperature of the process gas in said fourth and any higher stages absorption is less than the temperature of the process gas in said first stage absorption; The apparatus of claim 6 , further comprising at least one of:

8. 7. The apparatus of claim 6, further comprising an ammonium bicarbonate post-treatment section configured to receive an ammonium bicarbonate solution or slurry from the first stage absorption and produce solid ammonium bicarbonate therefrom.

9. Features: The multi-stage absorption is combined into one or more columns, with devices / components allowing the passage of gas being placed between said stages; At least one circulating liquid distributor is disposed at each stage of the absorption; At least one layer of gas-liquid contacting component, preferably packing, is disposed in each stage of absorption; The device is configured such that, among the multiple stages of absorption liquid used in sequence along the flow direction of the process gas, the absorption liquid in the preceding stage is replenished with the absorption liquid in the immediately succeeding stage, and the absorption liquid in the final stage is replenished with water; The apparatus of claim 6 , further comprising at least one of:

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