Chemical absorption method carbon capture system and method suitable for variable load

Abstract

The application provides a chemical absorption method carbon capture system and method suitable for variable load. The system comprises an absorption unit, a desorption unit and a heat exchange unit connecting the absorption unit and the desorption unit; the absorption unit comprises at least two absorption sections and at least two sets of staged reflux components; the desorption unit comprises at least two desorption sections and at least two sets of staged reflux components. The method comprises: performing staged reflux on the absorbent in the absorption unit and the desorption unit, and by adjusting the lean liquid flow and the rich liquid flow, when the flue gas treatment amount entering the absorption unit changes due to the change of the power generation load, the CO2 load of the lean liquid and the CO2 load of the rich liquid remain unchanged. Under the premise of ensuring the feasibility of the system and the reasonable investment cost, by means of system modification and unique regulation method, the power generation load response speed of the capture system is improved, meanwhile, the system capture rate and the regeneration energy consumption are considered, the regulation logic of the system is simplified, and the sharp increase of the regeneration energy consumption is slowed down at the ultra-low power generation load.

Description

Technical Field

[0001] This invention relates to a chemical absorption carbon capture system and method suitable for variable loads, belonging to the field of carbon dioxide capture technology. Background Technology

[0002] CO2 capture, utilization, and storage (CCUS) technology is considered an indispensable technological approach for achieving emission reduction targets at present. CO2 capture mainly refers to the separation of high-purity CO2 gas from flue gas produced by the combustion of fossil fuels in the power and industrial sectors.

[0003] Chemical absorption technology is one of the most promising CO2 capture technologies for the coal-fired power industry. Its principle is to separate CO2 from flue gas through a reversible chemical reaction between CO2 and an organic amine absorbent. An absorbent containing a small amount of CO2 (hereinafter referred to as lean solution) enters from the top of the absorption tower and reacts counter-currently with the flue gas to absorb CO2. The absorbent after absorbing CO2 (hereinafter referred to as rich solution) is sent to the desorption tower where a high-temperature reverse reaction releases CO2, thus separating high-purity CO2 gas from the flue gas. The absorbent is regenerated in the desorption tower to become lean solution and sent back to the absorption tower, thus completing the absorbent cycle.

[0004] Coal-fired power generation is the "pillar" and "ballast" for ensuring a safe and stable power supply. While new energy sources such as wind and solar power offer advantages in energy conservation and environmental protection, their intermittent generation causes frequent fluctuations in the power grid, posing new requirements and challenges to the peak-shaving capabilities of coal-fired power units. Currently, units that have completed flexibility retrofits for thermal power plants can achieve deep peak shaving at a maximum of 15% of rated load. Chemical absorption carbon dioxide capture technology, as a crucial component of clean coal-fired power generation, urgently needs to be able to adapt to rapid changes in power generation load.

[0005] However, existing chemical absorption carbon capture processes have the following problems:

[0006] 1. The load response speed of the capture system is slow.

[0007] In conventional chemical absorption CO2 capture processes, when the power generation load changes, the flue gas treatment volume changes with the power generation load, and it is necessary to adjust the lean liquid CO2 load and rich liquid CO2 load of the absorbent to a new operating range. However, since the time for the absorbent to complete a single cycle in the system is often measured in hours, the process of stabilizing the lean liquid and rich liquid CO2 load to the target value takes several hours.

[0008] 2. It is impossible to balance the CO2 capture rate of flue gas with the energy consumption of regeneration capture.

[0009] Assuming the system's rated CO2 capture rate is 90% and the unit's power generation load is 50%, if a higher lean CO2 load is adopted to achieve a reasonable CO2 capture rate (90%) and lower energy consumption for regeneration, then if the power generation load increases and the flue gas treatment volume increases, the CO2 capture rate will not meet the target (<90%) during system regulation. If a lower lean CO2 load strategy is adopted, the capture rate can still meet the demand when the power generation load increases, but the current CO2 capture rate (>90%) is excessive, and the regeneration energy consumption is too high.

[0010] 3. Generator sets consume a lot of energy when operating at ultra-low load.

[0011] When the unit operates at a prolonged period of ultra-low power generation load (e.g., 20% power generation load), the mainstream flow rates of lean and rich solutions cannot be too low in order to ensure mass transfer efficiency in the absorption and desorption towers. Therefore, a large amount of absorbent still circulates between the low-temperature absorption tower (40-60℃) and the high-temperature desorption tower (100-120℃), resulting in significant heat loss in the lean and rich solution heat exchangers and a substantial increase in the energy consumption required to capture a unit of CO2. Summary of the Invention

[0012] To address the aforementioned technical problems, the present invention aims to provide a chemical absorption carbon capture system and method suitable for variable loads. This invention can improve the power generation load response speed of the capture system while simultaneously considering the system capture rate and regeneration energy consumption.

[0013] To achieve the above objectives, the first aspect of the present invention provides a chemical absorption carbon capture system suitable for variable loads, comprising: an absorption unit, a desorption unit, and a heat exchange unit connecting the absorption unit and the desorption unit;

[0014] The absorption unit is used to make the absorbent come into countercurrent contact with the flue gas to absorb CO2 in the flue gas. It includes at least two absorption sections and at least two sets of staged reflux assemblies. The staged reflux assembly includes at least an absorption unit reflux pipeline. The absorption unit reflux pipeline is used to make the absorbent flow back from below a certain absorption section to above it or back to above an absorption section above the certain absorption section.

[0015] The desorption unit is used to regenerate the absorbent and release CO2, and includes at least two desorption sections and at least two sets of staged reflux assemblies. The staged reflux assembly includes at least a desorption unit reflux pipeline, which is used to allow the absorbent to reflux from below a certain desorption section to above it or to reflux to above a desorption section above the certain desorption section.

[0016] A second aspect of the present invention provides a chemical absorption carbon capture method suitable for variable loads, the method comprising the following steps:

[0017] S1: The flue gas enters the absorption unit and comes into countercurrent contact with the lean liquid to absorb CO2 in the flue gas, thus obtaining treated flue gas and rich liquid.

[0018] S2: The rich liquid enters the desorption unit after exchanging heat with the lean liquid in the heat exchange unit. The rich liquid is regenerated by the steam in the reboiler and CO2 is released to obtain regenerated gas and lean liquid. The lean liquid enters the absorption unit after exchanging heat with the rich liquid in the heat exchange unit.

[0019] S3: The absorbent in the absorption unit and the desorption unit is refluxed in at least two stages using a staged reflux assembly. By adjusting the lean liquid flow rate and the rich liquid flow rate, the CO2 load of the lean liquid and the CO2 load of the rich liquid remain basically unchanged when the amount of flue gas treated in the absorption unit changes due to changes in the power generation load.

[0020] The absorption unit includes at least two absorption sections and at least two sets of staged reflux assemblies. The staged reflux assembly includes at least an absorption unit reflux pipeline. The absorption unit reflux pipeline is used to allow the absorbent to reflux from below an absorption section to above it or to reflux to above an absorption section above the absorption section.

[0021] The desorption unit includes at least two desorption sections and at least two sets of staged reflux assemblies. The staged reflux assembly includes at least a desorption unit reflux pipeline. The desorption unit reflux pipeline is used to allow the absorbent to reflux from below a certain desorption section to above it or to reflux to above a desorption section above the certain desorption section.

[0022] The technical solution of the present invention has at least the following beneficial effects:

[0023] 1. When changes in power generation load lead to changes in flue gas treatment volume, since only changes in absorbent flow rate are involved and absorbent CO2 load regulation is not involved, the system regulation and balancing time is reduced from several hours to less than fifteen minutes.

[0024] 2. The energy consumption of absorbent regeneration is closely related to the CO2 load of lean and rich liquid. A constant CO2 load of lean and rich liquid ensures that the regeneration energy consumption remains stable within a relatively optimal range when the power generation load changes.

[0025] 3. In the context of deep flue gas peak shaving, the flue gas CO2 flow rate is significantly reduced. This invention significantly reduces the lean liquid flow rate (lean liquid mainstream flow rate) and the rich liquid flow rate (rich liquid mainstream flow rate), reduces the heat exchange loss of the lean and rich liquid heat exchange units, and has a significant advantage in regeneration energy consumption compared with existing processes.

[0026] 4. The flow control linkage logic is simple and easy to implement, and does not involve linkage with the CO2 load of the absorbent, reducing the need for frequent testing of the CO2 load of the absorbent. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the chemical absorption carbon capture system suitable for variable load in Embodiment 1 of the present invention.

[0028] Figure 2 This is a schematic diagram of the structure of the chemical absorption carbon capture system suitable for variable load in Embodiment 3 of the present invention.

[0029] Figure 3 This is a schematic diagram of the structure of the chemical absorption carbon capture system suitable for variable load in Embodiment 4 of the present invention.

[0030] Explanation of icon numbers:

[0031] 1-Absorption unit; 2-Desorption unit; 3-Heat exchange unit;

[0032] 101-First absorption section; 102-Second absorption section; 103-Third absorption section; 104-First collection tank; 105-Third-stage reflux pipeline of absorption unit; 106-Second collection tank; 107-Second-stage reflux pipeline of absorption unit; 108-Third collection tank; 109-First-stage reflux pipeline of absorption unit; 110-Interstage cooler; 111-Lean liquid cooler; 112-Fourth absorption section; 113-Fifth absorption section; 114-Seventh collection tank; 115-Fourth-stage reflux pipeline of absorption unit; 116-Eighth collection tank; 117-Fifth-stage reflux pipeline of absorption unit;

[0033] 201 - Reboiler; 202 - First desorption section; 203 - Second desorption section; 204 - Third desorption section; 205 - Fourth collection tank; 206 - Third-stage reflux pipeline of desorption unit; 207 - Fifth collection tank; 208 - Second-stage reflux pipeline of desorption unit; 209 - Sixth collection tank; 210 - First-stage reflux pipeline of desorption unit. Detailed Implementation

[0034] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0035] According to specific embodiments of the present invention, such as Figures 1 to 3 As shown, the present invention provides a chemical absorption carbon capture system suitable for variable loads, which includes: an absorption unit 1, a desorption unit 2, and a heat exchange unit 3 connecting the absorption unit 1 and the desorption unit 2.

[0036] The absorption unit 1 is used to make the absorbent come into countercurrent contact with the flue gas to absorb CO2 in the flue gas. It includes at least two absorption sections and at least two sets of staged reflux assemblies. The staged reflux assembly includes at least an absorption unit reflux pipeline. The absorption unit reflux pipeline is used to make the absorbent flow back from below a certain absorption section to above it or back to above an absorption section above the certain absorption section.

[0037] The desorption unit 2 is used to regenerate the absorbent and release CO2, and includes at least two desorption sections and at least two sets of staged reflux assemblies. The staged reflux assembly includes at least a desorption unit reflux pipeline, which is used to allow the absorbent to reflux from below a certain desorption section to above it or to reflux to above a desorption section above the certain desorption section.

[0038] In some embodiments, the upper part of the absorption unit 1 is provided with a treated flue gas outlet and a lean liquor inlet, and the lower part is provided with a flue gas inlet and a rich liquor outlet.

[0039] In some embodiments, the upper part of the desorption unit 2 is provided with a rich liquid inlet and a regenerated gas outlet, and the lower part is provided with a lean liquid outlet; the lower part of the desorption unit 2 is connected to a reboiler 201.

[0040] In some embodiments, the rich liquid outlet of the absorption unit 1 is connected to the rich liquid inlet of the desorption unit 2 through the heat exchange unit 3, and the lean liquid inlet of the absorption unit 1 is connected to the lean liquid outlet of the desorption unit 2 through the heat exchange unit 3.

[0041] Those skilled in the art will understand that the rich solution refers to the solution after CO2 absorption by the absorbent in absorption unit 1, and the lean solution refers to the solution after CO2 release by the regeneration of the absorbent in desorption unit 2. The regeneration of desorption unit 2 utilizes steam in reboiler 201 to regenerate the rich solution and release CO2, yielding regenerated gas and lean solution. Each absorption section is equipped with packing material, and each desorption section is equipped with packing material. In this embodiment of the invention, the packing material in absorption unit 1 and desorption unit 2 can be any packing material available in the prior art, and the invention does not impose any special limitations on them.

[0042] This invention creatively designs a staged reflux assembly for the absorption unit 1 and desorption unit 2, used to extract absorbent from below each absorption / desorption section and send it above or above the absorption / desorption section above that section. Through the design of the staged reflux assembly for the absorption unit 1 and desorption unit 2 of this invention, when changes in power generation load cause changes in flue gas treatment volume, the lean liquid CO2 load and rich liquid CO2 load can always remain basically unchanged, and the CO2 capture rate meets the standard.

[0043] In some embodiments, the number of staged reflux components in absorption unit 1 is 2-10 sets, and the number of staged reflux components in desorption unit 2 is 2-6 sets. Based on comprehensive considerations such as the depth of power generation load regulation requirements and investment and operating costs, this embodiment of the invention controls the number of staged reflux components in absorption unit 1 to 2-10 sets and the number of staged reflux components in desorption unit 2 to 2-6 sets. If the number of staged reflux components is lower than the above range (i.e., if the number of stages of reflux is lower than the above range), the recirculation of the mixed absorbent will change the CO2 load distribution of the absorbent in absorption unit 1 and desorption unit 2, reducing the theoretical number of trays in the tower, and causing a decrease in the system's adaptability to low power generation load conditions. If the number of staged reflux components is higher than the above range (i.e., if the number of stages of reflux is higher than the above range), the investment cost increases, the number of system control components increases, and the operating power consumption increases.

[0044] In some embodiments, the absorption section is connected to the absorption unit return pipeline via a collection tank located below it, and the desorption section is connected to the desorption unit return pipeline via a collection tank located below it. Each collection tank is provided with an outlet for allowing the absorbent to flow downwards.

[0045] In some embodiments, the collection tank has a liquid storage function; when the liquid level is lower than a set value, the absorbent in the collection tank stops flowing downwards. Preferably, the set value for the liquid level in the collection tank of absorption unit 1 is the lean liquid mainstream flow rate during the start-up of the baseline operating conditions for 2-10 minutes, and the set value for the liquid level in the collection tank of desorption unit 2 is the rich liquid mainstream flow rate during the start-up of the baseline operating conditions for 2-10 minutes. For example, if the lean liquid mainstream flow rate and the rich liquid mainstream flow rate during the start-up of the baseline operating conditions for 2-10 minutes are both 0.05 m³ / min... 3 The set value for the liquid volume in the collection tank is 0.05m. 3 The liquid collection tank in this embodiment of the invention has a liquid storage function. When the liquid volume is lower than a set value, the liquid will no longer flow to the lower absorption section or desorption section, ensuring that the circulation and reflux of each stage can be started and stopped at any time.

[0046] In some embodiments, the lean liquid inlet of the absorption unit 1 and the return inlet connected to the return pipeline of the uppermost absorption unit are the same inlet.

[0047] In some embodiments, a lean liquid cooler 111 is provided on the pipeline connected to the lean liquid inlet of the absorption unit 1.

[0048] In some embodiments, an interstage cooler 110 is provided on the absorption unit return pipe located in the middle of the absorption unit 1.

[0049] In some embodiments, the staged reflux assembly in the absorption unit 1 and the desorption unit 2 further includes a delivery pump, which is disposed on the reflux line of the absorption unit and the reflux line of the desorption unit.

[0050] In some embodiments, a transfer pump is provided on the pipeline connecting the rich liquid outlet of the absorption unit 1 to the heat exchange unit 3, and a transfer pump is provided on the pipeline connecting the lean liquid outlet of the desorption unit 2 to the heat exchange unit 3.

[0051] According to a specific embodiment of the present invention, a second aspect of the present invention provides a chemical absorption carbon capture method suitable for variable loads, the method comprising the following steps:

[0052] S1: The flue gas enters the absorption unit 1 and comes into countercurrent contact with the lean liquid to absorb CO2 in the flue gas, thus obtaining treated flue gas and rich liquid.

[0053] S2: The rich liquid enters the desorption unit 2 after exchanging heat with the lean liquid in the heat exchange unit 3. The rich liquid is regenerated by the steam in the reboiler 201 and CO2 is released to obtain regenerated gas and lean liquid. The lean liquid enters the absorption unit 1 after exchanging heat with the rich liquid in the heat exchange unit 3.

[0054] S3: The absorbent in the absorption unit 1 and the desorption unit 2 is refluxed in at least two stages using the staged reflux assembly in the absorption unit 1 and the desorption unit 2. By adjusting the lean liquid flow rate and the rich liquid flow rate, the CO2 load of the lean liquid and the CO2 load of the rich liquid remain basically unchanged when the amount of flue gas treated in the absorption unit 1 changes due to the change in power generation load.

[0055] The absorption unit 1 includes at least two absorption sections and at least two sets of staged reflux assemblies. The staged reflux assembly includes at least an absorption unit reflux pipeline. The absorption unit reflux pipeline is used to allow the absorbent to reflux from below an absorption section to above it or to reflux to above an absorption section above the absorption section.

[0056] The desorption unit 2 includes at least two desorption sections and at least two sets of staged reflux assemblies. The staged reflux assembly includes at least a desorption unit reflux pipeline, which is used to allow the absorbent to reflux from below a certain desorption section to above it or to reflux to above a desorption section above the certain desorption section.

[0057] It should be noted that, in the embodiments of the present invention, maintaining the lean solution CO2 load and the rich solution CO2 load essentially unchanged means allowing fluctuations of less than 3% in the lean solution CO2 load and the rich solution CO2 load.

[0058] It should be noted that, in this embodiment of the invention, "variable load" refers to changes in power generation load. When the power generation load changes, the amount of flue gas entering absorption unit 1 (i.e., flow rate) will change accordingly, and the flue gas CO2 flow rate (calculated by multiplying the flue gas amount by the flue gas CO2 concentration) will also change accordingly. The "lean liquid CO2 load" refers to the CO2 content in the lean liquid, and the "rich liquid CO2 load" refers to the CO2 content in the rich liquid.

[0059] In some embodiments, step S3 includes: when a change in power generation load causes a change in the amount of flue gas entering absorption unit 1, assuming the current CO2 flow rate at the flue gas inlet of absorption unit 1 is x% of the flow rate before the power generation load change, adjusting the lean liquid mainstream flow rate and the rich liquid mainstream flow rate to x% of the flow rate before the power generation load change, and activating the staged reflux assembly of desorption unit 2, adjusting the reflux flow rate of each stage of desorption unit 2 to 100% - x% of the rich liquid mainstream flow rate before the power generation load change, and then activating the staged reflux assembly of absorption unit 1, adjusting the reflux flow rate of each stage of absorption unit 1 so that the CO2 capture rate reaches a set value. Here, the lean liquid mainstream flow rate is the lean liquid flow rate in the pipeline connecting heat exchange unit 3 and the lean liquid outlet of desorption unit 2, and the rich liquid mainstream flow rate is the rich liquid flow rate in the pipeline connecting heat exchange unit 3 and the rich liquid outlet of absorption unit 1.

[0060] In some embodiments, step S3 specifically includes:

[0061] (1) All staged recirculation components of absorption unit 1 and desorption unit 2 are shut down or kept at the minimum flow rate. The operating condition after 100% power generation load reaches stability is taken as the benchmark operating condition. The benchmark indicators under the benchmark operating condition are recorded, including: flue gas CO2 flow rate at flue gas inlet of absorption unit 1, lean liquid mainstream flow rate and rich liquid mainstream flow rate; wherein, lean liquid mainstream flow rate is the lean liquid flow rate in the pipeline connecting the lean liquid outlet of heat exchange unit 3 and desorption unit 2, and rich liquid mainstream flow rate is the rich liquid flow rate in the pipeline connecting the rich liquid outlet of heat exchange unit 3 and absorption unit 1.

[0062] (2) Calculate the ratio of the flue gas CO2 flow rate at the flue gas inlet of absorption unit 1 under actual operating conditions when the power generation load changes to the flue gas CO2 flow rate at the flue gas inlet under the reference operating conditions, and record it as x%.

[0063] (3) Adjust the mainstream flow rate of lean liquor under actual working conditions to x% of the mainstream flow rate of lean liquor under the reference working conditions, and adjust the mainstream flow rate of rich liquor under actual working conditions to x% of the mainstream flow rate of rich liquor under the reference working conditions.

[0064] (4) Simultaneously turn on the staged reflux assembly of desorption unit 2, and adjust the reflux flow rate of each stage of desorption unit 2 under actual working conditions to be 100%-x% of the mainstream flow rate of rich liquid under the reference working conditions.

[0065] (5) Then turn on the staged recirculation component of the absorption unit 1 and adjust the recirculation flow rate of each stage of the absorption unit 1 under actual working conditions so that the CO2 capture rate reaches the set value; then when the power generation load changes and the amount of flue gas entering the absorption unit 1 changes, keep the lean liquid CO2 load and the rich liquid CO2 load basically unchanged.

[0066] Those skilled in the art will understand that, in the embodiments, in order to determine that when the change in power generation load causes a change in the amount of flue gas entering the absorption unit 1, the lean liquid CO2 load and the rich liquid CO2 load remain basically unchanged, the lean liquid CO2 load and the rich liquid CO2 load need to be tested under both the baseline operating conditions and the actual operating conditions.

[0067] It should be noted that, in the embodiments of the present invention, the reflux flow rates of each stage of the absorption unit 1 and the desorption unit 2 refer to the flow rates in the reflux pipelines of the absorption unit and the desorption unit, respectively.

[0068] In some embodiments, in step S3, the CO2 capture rate is set to 90%.

[0069] In some embodiments, in step S3 (4), when the flue gas CO2 flow rate at the flue gas inlet of the absorption unit 1 is lower than 90% of the flue gas CO2 flow rate at the flue gas inlet under the reference operating conditions, the staged reflux assembly of the desorption unit 2 is turned on.

[0070] In some embodiments, in step S3 (5), after turning on the staged reflux assembly of the absorption unit 1, the flow rate of each staged reflux of the absorption unit 1 under actual operating conditions is first adjusted to be 100%-x% of the mainstream flow rate of the lean liquid under the reference operating conditions, and then the flow rate of each staged reflux of the absorption unit 1 under actual operating conditions is adjusted so that the CO2 capture rate reaches the set value.

[0071] In some embodiments, step S3 (5) further includes: recording the reflux flow rate of each stage of the absorption unit 1 when the CO2 capture rate reaches the set value, denoted as y, plotting the x%-y curve based on different actual operating conditions, and subsequently adjusting the reflux flow rate of each stage of the absorption unit 1 with reference to the x%-y curve.

[0072] In some embodiments, in step S3, the benchmark index under the benchmark operating condition further includes: regenerated gas CO2 flow rate; and step S3 further includes: (6) adjusting the steam extraction amount of reboiler 201, which specifically includes: adjusting the steam usage amount of reboiler 201 under the actual operating condition, so that the regenerated gas CO2 flow rate is x% of the regenerated gas CO2 flow rate under the benchmark operating condition, and adjusting the steam extraction amount of reboiler 201 based on the steam usage amount of reboiler 201. Preferably, the benchmark index under the benchmark operating condition further includes: the steam usage of reboiler 201; and step S3 (3) further includes: adjusting the steam usage of reboiler 201 under the actual operating condition to x% of the steam usage of reboiler 201 under the benchmark operating condition, and step S3 (6) further includes: continuing to adjust the steam usage of reboiler 201 under the actual operating condition, so that the regenerated gas CO2 flow rate is x% of the regenerated gas CO2 flow rate under the benchmark operating condition, and adjusting the steam extraction rate of reboiler 201 based on the steam usage of reboiler 201. More preferably, step S3 (6) further includes: recording the steam usage of reboiler 201 when the regenerated gas CO2 flow rate is x% of the regenerated gas CO2 flow rate under the benchmark operating condition, denoted as z, plotting the x%-z curve based on different actual operating conditions, and subsequently adjusting the steam extraction rate of reboiler 201 with reference to the x%-z curve.

[0073] In some embodiments, the above method further includes step S4: when the power generation load changes further, by further regulating the lean liquid flow rate and the rich liquid flow rate, the lean liquid CO2 load and the rich liquid CO2 load remain basically unchanged when the power generation load change causes the flue gas treatment volume entering the absorption unit 1 to change. The method of further regulating the lean liquid flow rate and the rich liquid flow rate is the same as (2) to (5) (or (2) to (6)) in step S3.

[0074] In some embodiments, the above method further includes step S5: when the power generation load returns to 100%, the lean liquid mainstream flow rate, the rich liquid mainstream flow rate, and the steam usage of the reboiler 201 under the actual operating conditions are adjusted to be the same as under the baseline operating conditions. At the same time, the staged reflux components of the absorption unit 1 and the desorption unit 2 are all shut down or kept at the minimum flow rate, so that when the power generation load changes and the amount of flue gas treated in the absorption unit 1 changes, the lean liquid CO2 load and the rich liquid CO2 load remain basically unchanged.

[0075] In some embodiments, in step S3 (and steps S4 and S5), when the flue gas CO2 flow rate at the flue gas inlet of the absorption unit 1 under actual operating conditions is more than 90% of the flue gas CO2 flow rate at the flue gas inlet under reference operating conditions, the staged reflux assembly of the absorption unit 1 and the desorption unit 2 maintains the minimum flow rate operation.

[0076] In some embodiments, the minimum flow rates of the staged reflux components of the absorption unit 1 and the desorption unit 2 are 10% of the mainstream flow rate of the lean solution and 10% of the mainstream flow rate of the rich solution under the reference conditions, respectively.

[0077] In this embodiment of the invention, the staged reflux assembly of the desorption unit 2 and the absorption unit 1 can be selectively turned on and kept running at the lowest flow rate when the flue gas rated CO2 flow rate is 90%-100%, thereby avoiding frequent start-stop of the pump.

[0078] The above methods for regulating lean and rich liquid flow rates are based on the CO2 balance relationship:

[0079] Q CO2in *r co2 =F rich α rich -F lean α lean

[0080] Among them, Q CO2in The CO2 flow rate of the inlet flue gas is expressed in kmol / h.

[0081] r co2 CO2 capture rate;

[0082] F rich For the rich liquid flow rate, m 3 / h;

[0083] F lean For lean liquid flow rate, m 3 / h;

[0084] a rich For rich liquid loading, kmol / m 3 ;

[0085] α lean For lean solution loading, kmol / m 3 .

[0086] The flow rates of rich solutions and lean solutions are quite similar, and can be approximated as the solution circulation rate.

[0087]

[0088] Since the CO2 capture rate requirement remains unchanged, the technical approach of this embodiment of the invention is to keep both the lean liquid CO2 load and the rich liquid CO2 load essentially constant. Therefore, the changes in the lean liquid flow rate and the rich liquid flow rate are proportional to the changes in the inlet flue gas CO2 flow rate.

[0089] F lean ∝Q CO2in ;

[0090] F rich ∝Q CO2in.

[0091] In response to changes in power generation load, this embodiment of the invention employs a constant lean-rich liquid CO2 load and a controlled lean-rich liquid flow rate. When the power generation load is lower than the rated load, maintaining the lean-rich liquid load results in a reduction in the lean-rich liquid flow rate. At this time, the absorbent in the absorption unit 1 and desorption unit 2 is refluxed in stages to ensure that the liquid spray density in the absorption unit 1 and desorption unit 2 is sufficient, so that the gas-liquid reaction in the tower has a sufficient effective mass transfer specific surface area, thus ensuring the CO2 capture rate and regeneration rate of the system.

[0092] This invention provides a chemical absorption carbon capture system and method suitable for variable loads. While ensuring system feasibility and reasonable investment costs, this invention addresses the problem of poor adaptability of existing chemical absorption CO2 capture systems to rapid changes in power generation flue gas load through system modification and unique control methods. It significantly improves the power generation load response speed of the capture system, while simultaneously considering the system capture rate and regeneration energy consumption, simplifying the system's control logic, and mitigating the sharp increase in regeneration energy consumption at ultra-low power generation loads.

[0093] The technical solutions of the present invention are illustrated in detail below through embodiments and comparative examples. However, the present invention is not limited to these embodiments, and various modifications can be made within the scope of the key points of the present invention.

[0094] Example 1

[0095] This embodiment provides a chemical absorption carbon capture system suitable for variable loads, the structure of which is as follows: Figure 1 As shown, the system includes: an absorption unit 1, a desorption unit 2, and a heat exchange unit 3;

[0096] The upper part of the absorption unit 1 is provided with a treated flue gas outlet and a lean liquor inlet, and the lower part is provided with a flue gas inlet and a rich liquor outlet.

[0097] The absorption unit 1 includes three absorption sections, from bottom to top: a first absorption section 101, a second absorption section 102, and a third absorption section 103. Each absorption section is equipped with packing material. The absorption unit 1 includes three sets of staged reflux assemblies, each of which includes at least an absorption unit reflux pipeline. Specifically, a first collection tank 104 is located below the first absorption section 101, connected to the third-stage reflux outlet of the absorption unit. A third-stage reflux inlet is located above the first absorption section 101, and the third-stage reflux outlet is connected to the third-stage reflux inlet via a third-stage reflux pipeline 105 outside the absorption unit 1. A second collection tank 106 is located below the second absorption section 102. 06 connects to the secondary reflux outlet of the absorption unit. A secondary reflux inlet of the absorption unit is located above the second absorption section 102. The secondary reflux outlet of the absorption unit is connected to the secondary reflux inlet of the absorption unit via a secondary reflux pipeline 107 outside the absorption unit 1. A third collection tank 108 is located below the third absorption section 103. The third collection tank 108 connects to the primary reflux outlet of the absorption unit. A primary reflux inlet of the absorption unit is located above the third absorption section 103. The primary reflux outlet of the absorption unit is connected to the primary reflux inlet of the absorption unit via a primary reflux pipeline 109 outside the absorption unit 1. The first collection tank 104, the second collection tank 106, and the third collection tank 108 are each provided with an outlet for the absorbent to flow downwards.

[0098] An interstage cooler 110 is installed on the secondary reflux pipeline 107 of the absorption unit, and an interstage cooling absorbent inlet is provided between the tertiary reflux inlet and the secondary reflux outlet of the absorption unit. The secondary reflux pipeline 107 of the absorption unit splits into two branch pipelines at the rear end of the interstage cooler 110. One branch pipeline is connected to the secondary reflux inlet of the absorption unit (for upward reflux), and the other branch pipeline is connected to the interstage cooling absorbent inlet (for downward reflux). In this embodiment, interstage cooling is provided in the middle of the absorption unit 1. The upper reflux of the absorption section with interstage cooling shares the same liquid collection tank, interstage cooler 110 and liquid extraction pipeline in the reflux pipeline with the interstage cooling, so as to achieve the effects of cooling and reflux at the same time.

[0099] The upper part of the desorption unit 2 is provided with a rich liquid inlet and a regenerated gas outlet, and the lower part is provided with a lean liquid outlet; the lower part of the desorption unit is connected to a reboiler 201.

[0100] The desorption unit 2 internally includes three desorption sections, from bottom to top: a first desorption section 202, a second desorption section 203, and a third desorption section 204; each desorption section is equipped with packing material; the desorption unit 2 includes three sets of staged reflux assemblies, each set of staged reflux assemblies including at least a desorption unit reflux pipeline; specifically, a fourth collection tank 205 is located below the first desorption section 202, connected to the third-stage reflux outlet of the desorption unit, and a third-stage reflux inlet is located above the first desorption section 202; the third-stage reflux outlet of the desorption unit is connected to the third-stage reflux inlet of the desorption unit through a third-stage reflux pipeline 206 outside the desorption unit 2; a fifth collection tank 207 is located below the second desorption section 203, and the fifth collection tank 207... 07 connects to the secondary reflux outlet of the desorption unit. A secondary reflux inlet of the desorption unit is located above the second desorption section 203. The secondary reflux outlet of the desorption unit is connected to the secondary reflux inlet of the desorption unit via a secondary reflux pipeline 208 outside the desorption unit 2. A sixth collection tank 209 is located below the third desorption section 204. The sixth collection tank 209 connects to the primary reflux outlet of the desorption unit. A primary reflux inlet of the desorption unit is located above the third desorption section 204. The primary reflux outlet of the desorption unit is connected to the primary reflux inlet of the desorption unit via a primary reflux pipeline 210 outside the desorption unit 2. The fourth collection tank 205, the fifth collection tank 207, and the sixth collection tank 209 are each provided with an outlet for the absorbent to flow downwards.

[0101] The rich liquid outlet of absorption unit 1 is connected to the rich liquid inlet of desorption unit 2 through heat exchange unit 3, and the lean liquid inlet of absorption unit 1 is connected to the lean liquid outlet of desorption unit 2 through heat exchange unit 3.

[0102] The absorption unit 1 and desorption unit 2 are the absorption tower and desorption tower, respectively, both with a tower diameter of 300 mm. The total height of the packing in the absorption unit 1 is 15 m (5 m per section), and the total height of the packing in the desorption unit 2 is 9 m (3 m per section). The packing in both the absorption unit 1 and the desorption unit 2 is conventional packing in the art; in this embodiment, Mellapak 250Y stainless steel packing is specifically used.

[0103] The first collection tank 104, the second collection tank 106, the third collection tank 108, the fourth collection tank 205, the fifth collection tank 207, and the sixth collection tank 209 all have a liquid storage function. When the liquid level in each tank falls below a set value, the absorbent stops flowing downwards. The set value for the liquid level in the first collection tank 104, the second collection tank 106, the third collection tank 108, the fourth collection tank 205, the fifth collection tank 207, and the sixth collection tank 209 is 0.05m. 3In other words, the liquid volume settings of the first collection tank 104, the second collection tank 106, and the third collection tank 108 of the absorption unit 1 are the lean liquid mainstream flow rates during the start-up of the baseline operating conditions for 2-10 minutes, and the liquid volume settings of the fourth collection tank 205, the fifth collection tank 207, and the sixth collection tank 209 of the desorption unit 2 are the rich liquid mainstream flow rates during the start-up of the baseline operating conditions for 2-10 minutes.

[0104] The lean liquid inlet of absorption unit 1 and the primary reflux inlet of the absorption unit above the third absorption section 103 are the same inlet.

[0105] A lean liquid cooler 111 is installed on the pipeline connected to the lean liquid inlet of absorption unit 1.

[0106] The staged reflux assembly in absorption unit 1 and desorption unit 2 further includes several transfer pumps, which are respectively installed on the tertiary reflux pipeline 105 of absorption unit, the secondary reflux pipeline 107 of absorption unit, the primary reflux pipeline 109 of absorption unit, the tertiary reflux pipeline 206 of desorption unit, the secondary reflux pipeline 208 of desorption unit, and the primary reflux pipeline 210 of desorption unit.

[0107] A transfer pump is installed on the pipeline connecting the rich liquid outlet of absorption unit 1 to heat exchange unit 3, and a transfer pump is installed on the pipeline connecting the lean liquid outlet of desorption unit 2 to heat exchange unit 3.

[0108] This embodiment also provides a chemical absorption carbon capture method suitable for variable loads, which uses the system described above. The rated flue gas treatment capacity (i.e., flow rate) is 300 Nm³. 3 The flue gas CO2 concentration is 12 vol.%, the CO2 capture rate is set at 90%, and the rated regeneration gas CO2 flow rate is 32.4 Nm³ / h. 3 The absorbent used is a 30wt.% aqueous solution of MEA (ethanolamine) per hour, and the system absorbent loading is 1.5t.

[0109] The method includes the following steps:

[0110] S1: The flue gas enters the absorption unit 1 and comes into countercurrent contact with the lean liquid to absorb CO2 in the flue gas, thus obtaining treated flue gas and rich liquid.

[0111] S2: The rich liquid enters the desorption unit 2 after exchanging heat with the lean liquid in the heat exchange unit 3. The rich liquid is regenerated by the steam in the reboiler 201 and CO2 is released to obtain regenerated gas and lean liquid. The lean liquid enters the absorption unit 1 after exchanging heat with the rich liquid in the heat exchange unit 3.

[0112] S3: (1) Close all the staged recirculation components of absorption unit 1 and desorption unit 2, and take the operating condition after the power generation load reaches stability as the benchmark operating condition. Record the benchmark indicators under the benchmark operating condition, which include: flue gas CO2 flow rate at the flue gas inlet of absorption unit 1 (calculated by flue gas flow rate × flue gas CO2 concentration), lean liquid mainstream flow rate, rich liquid mainstream flow rate and regenerated gas CO2 flow rate; wherein, the lean liquid mainstream flow rate is the lean liquid flow rate in the pipeline connecting the lean liquid outlet of heat exchange unit 3 and desorption unit 2, and the rich liquid mainstream flow rate is the rich liquid flow rate in the pipeline connecting the rich liquid outlet of heat exchange unit 3 and absorption unit 1; the flue gas flow rate at the flue gas inlet of absorption unit 1 under the benchmark operating condition is 300 Nm 3 At this time, the steam usage of reboiler 201 is 115 kg / h, and the mainstream flow rate of lean liquor is 1.15 m³ / h. The CO2 concentration in the flue gas is 12.1 vol.%. 3 / h, the lean solution CO2 loading is 0.253 mol CO2 / mol MEA, and the rich solution mainstream flow rate is 1.26 m³ / h. 3 The CO2 loading rate of the rich liquid was 0.533 mol CO2 / mol MEA, the CO2 capture rate was 90.6%, and the CO2 flow rate of the regenerated gas was 32.6 Nm³ / h. 3 / h, the regeneration energy consumption is 4.07GJ / t CO2;

[0113] (2) Then change the operating conditions and switch the flue gas CO2 flow rate to 50% of the rated flue gas CO2 flow rate (the rated flue gas CO2 flow rate is the flue gas CO2 flow rate under the reference operating conditions). The flue gas CO2 concentration is tested to be 11.9 vol.%, which means that the ratio of the flue gas CO2 flow rate at the flue gas inlet of absorption unit 1 under the actual operating conditions when the power generation load changes to the flue gas CO2 flow rate at the flue gas inlet under the reference operating conditions is recorded as 50% (i.e. x%).

[0114] (3) Adjust the lean liquid mainstream flow rate under actual operating conditions to 50% of the lean liquid mainstream flow rate under the reference operating conditions, i.e., 0.575m. 3 / h, adjust the mainstream flow rate of the rich liquid under actual operating conditions to 50% of the mainstream flow rate of the rich liquid under the reference operating conditions, i.e., 0.63m 3 / h, adjust the steam consumption of reboiler 201 under actual operating conditions to 50% of the steam consumption of reboiler 201 under reference operating conditions, i.e., 57.5kg / h;

[0115] (4) Simultaneously activate the staged reflux assembly of desorption unit 2, and adjust the reflux flow rates of each stage in desorption unit 2 under actual operating conditions (i.e., the flow rates in the tertiary reflux pipeline 206, the secondary reflux pipeline 208, and the primary reflux pipeline 210 of the desorption unit) to be 100%-50% (i.e., 100%-x%) of the mainstream flow rate of the rich liquid under the reference operating conditions, i.e., 0.63m 3 / h;

[0116] (5) Then turn on the staged reflux assembly of absorption unit 1, and first adjust the reflux flow rate of each stage of absorption unit 1 under actual operating conditions (i.e., the flow rate in the third-stage reflux pipeline 105, the second-stage reflux pipeline 107, and the first-stage reflux pipeline 109 of absorption unit) to be 100%-50% of the lean liquid mainstream flow rate under the reference operating conditions, i.e., 0.575m 3 / h, then adjust the recirculation flow rate of each stage of absorption unit 1 under actual operating conditions to achieve a CO2 capture rate of 90%, at which point the recirculation flow rate of each stage of absorption unit 1 is 0.520m³ / h. 3 / h; and when the change in power generation load causes the change in the amount of flue gas entering the absorption unit, the lean liquid CO2 load and the rich liquid CO2 load remain basically unchanged; selectively including: recording the recirculation flow rate of each stage of absorption unit 1 when the CO2 capture rate reaches the set value, denoted as y, and drawing the x%-y curve based on different actual operating conditions, and subsequently adjusting the recirculation flow rate of each stage of absorption unit 1 with reference to the x%-y curve.

[0117] (6) Continue to adjust the steam usage of reboiler 201 under actual operating conditions to 60.5 kg / h, so that the regenerated gas CO2 flow rate is 50% of the regenerated gas CO2 flow rate under the reference operating conditions. Adjust the steam extraction rate of reboiler 201 based on the steam usage of reboiler 201. Optionally, this includes: recording the steam usage of reboiler 201 when the regenerated gas CO2 flow rate is x% of the regenerated gas CO2 flow rate under the reference operating conditions, denoted as z. Plot the x%-z curve based on different actual operating conditions, and subsequently adjust the steam extraction rate of reboiler 201 with reference to the x%-z curve.

[0118] The changes in indicators were tested and recorded at 15 min, 30 min, 1 h, and 2 h after changing operating conditions. The CO2 capture rate was 90.1%, 90.3%, 90.4%, and 90.3% over time, respectively. The lean liquid CO2 load was 0.252, 0.254, 0.252, and 0.251 mol CO2 / mol MEA over time, respectively, and the rich liquid CO2 load was 0.531, 0.532, 0.534, and 0.533 mol CO2 / mol MEA over time, respectively. It can be seen that the capture rate and lean / rich liquid loads tend to stabilize within 15 min under changing operating conditions, and the system's equilibrium adjustment time is extremely short. The measured CO2 flow rate of the regenerated gas under 50% of the rated CO2 flow rate of the flue gas was 16.4 Nm³. 3 The regeneration energy consumption is 4.30 GJ / t CO2 per hour, which is 2.5% lower than that of Comparative Example 1 below.

[0119] In this embodiment, the flue gas CO2 flow rate was then switched from 50% of the rated flow rate back to 100% of the rated flow rate, and the tested flue gas CO2 concentration was 12.0 vol.%.

[0120] At this point, the above method further includes:

[0121] Adjust the lean liquor mainstream flow rate, the rich liquor mainstream flow rate, and the steam usage of reboiler 201 back to the values ​​under the baseline operating conditions, i.e., adjust the lean liquor mainstream flow rate to 1.15m³ / h. 3 / h, the mainstream flow rate of the rich solution is 1.26m³ / h. 3 The steam usage of reboiler 201 is 115 kg / h. At the same time, the staged reflux components of absorption unit 1 and desorption unit 2 are all shut down. Thus, when the amount of flue gas entering absorption unit 1 changes due to changes in power generation load, the lean liquid CO2 load and rich liquid CO2 load remain basically unchanged.

[0122] The changes in indicators were tested and recorded at 15 min, 30 min, 1 h, and 2 h after the system was operating under varying conditions. The CO2 capture rate was 90.6%, 90.5%, 90.6%, and 90.4% over time, respectively. The CO2 load of the lean solution was 0.251, 0.250, 0.250, and 0.251 mol CO2 / mol MEA over time, respectively, and the CO2 load of the rich solution was 0.532, 0.532, 0.532, and 0.533 mol CO2 / mol MEA over time, respectively. It can be seen that the capture rate and the lean and rich solution loads tend to stabilize within 15 min under varying conditions, and the regenerated gas CO2 flow rate is 32.4 Nm³. 3 The system regeneration energy consumption is 4.07 GJ / t CO2 per hour.

[0123] Example 2

[0124] This embodiment provides a chemical absorption carbon capture method suitable for variable loads, using the system of Example 1. The rated flue gas treatment capacity (i.e., flow rate) is 300 Nm³. 3 The flue gas CO2 concentration is 12 vol.%, the CO2 capture rate is set at 90%, and the rated regeneration gas CO2 flow rate is 32.4 Nm³ / h. 3 The absorbent used is a 30wt.% MEA aqueous solution, and the system absorbent loading is 1.5t.

[0125] The method includes the following steps:

[0126] S1: The flue gas enters the absorption unit 1 and comes into countercurrent contact with the lean liquid to absorb CO2 in the flue gas, thus obtaining treated flue gas and rich liquid.

[0127] S2: The rich liquid enters the desorption unit 2 after exchanging heat with the lean liquid in the heat exchange unit 3. The rich liquid is regenerated by the steam in the reboiler 201 and CO2 is released to obtain regenerated gas and lean liquid. The lean liquid enters the absorption unit 1 after exchanging heat with the rich liquid in the heat exchange unit 3.

[0128] S3: (1) Close all the staged reflux components of absorption unit 1 and desorption unit 2, and take the operating condition after the power generation load reaches 100% stability as the benchmark operating condition. Record the benchmark indicators under the benchmark operating condition, which include: flue gas CO2 flow rate at the flue gas inlet of absorption unit, lean liquid mainstream flow rate, rich liquid mainstream flow rate and regenerated gas CO2 flow rate; wherein, the lean liquid mainstream flow rate is the lean liquid flow rate in the pipeline connecting the heat exchange unit 3 and the lean liquid outlet of desorption unit 2, and the rich liquid mainstream flow rate is the rich liquid flow rate in the pipeline connecting the heat exchange unit 3 and the rich liquid outlet of absorption unit 1; the flue gas flow rate at the flue gas inlet of absorption unit 1 under the benchmark operating condition is 300 Nm 3 At this time, the steam usage of reboiler 201 is 115 kg / h, and the mainstream flow rate of lean liquor is 1.15 m³ / h. The CO2 concentration in the flue gas is 12.1 vol.%. 3 / h, the lean solution CO2 loading is 0.253 mol CO2 / mol MEA, and the rich solution mainstream flow rate is 1.26 m³ / h. 3 The CO2 loading rate of the rich liquid was 0.533 mol CO2 / mol MEA, the CO2 capture rate was 90.6%, and the CO2 flow rate of the regenerated gas was 32.6 Nm³ / h. 3 / h, the regeneration energy consumption is 4.07GJ / t CO2;

[0129] (2) Then the operating conditions were changed so that the flue gas CO2 flow rate slowly decreased from 100% of the rated flow rate. After 2 hours, it decreased to 20% of the rated flow rate and remained stable. The flue gas CO2 concentration was tested to be about 12 vol.% during the whole process. That is, the ratio of the flue gas CO2 flow rate at the flue gas inlet of absorption unit 1 under the actual operating conditions when the power generation load changes to the flue gas CO2 flow rate at the flue gas inlet under the reference operating conditions is recorded as 20% (i.e. x%).

[0130] (3) Adjust the lean liquid mainstream flow rate under actual operating conditions to 20% of the lean liquid mainstream flow rate under the reference operating conditions, i.e., 0.23m. 3 / h, adjust the mainstream flow rate of the rich liquid under actual operating conditions to 20% of the mainstream flow rate of the rich liquid under the reference operating conditions, i.e., 0.25m 3 / h;

[0131] (4) Simultaneously, when the flue gas CO2 flow rate is lower than 90% of the baseline operating condition, the staged reflux assembly of desorption unit 2 is activated, and the reflux flow rates of each stage of desorption unit 2 under actual operating conditions (i.e., the flow rates in the tertiary reflux pipeline 206, the secondary reflux pipeline 208, and the primary reflux pipeline 210 of the desorption unit) are adjusted to be 100%-20% (i.e., 100%-x%) of the mainstream flow rate of the rich liquid under the baseline operating condition, i.e., 1.01m 3 / h, the reflux flow rate of each stage in desorption unit 2 is all from 0.12m³ / h. 3 / h increased to 1.01m over time. 3 / h and stable;

[0132] (5) Then, turn on the staged reflux assembly of absorption unit 1 and adjust the reflux flow rates of each stage of absorption unit 1 under actual operating conditions (i.e., the flow rates in the third-stage reflux pipeline 105, the second-stage reflux pipeline 107, and the first-stage reflux pipeline 109 of absorption unit) so that the CO2 capture rate reaches the set value of 90%. At this time, the reflux flow rates of each stage of absorption unit 1 are all from 0.09m³. 3 / h rose to 0.78m 3 / h; and when the change in power generation load causes the flue gas treatment volume entering absorption unit 1 to change, the lean liquid CO2 load and rich liquid CO2 load remain basically unchanged; selectively including: recording the recirculation flow rate of each stage of absorption unit 1 when the CO2 capture rate reaches the set value, denoted as y, and drawing the x%-y curve based on different actual operating conditions, and subsequently adjusting the recirculation flow rate of each stage of absorption unit 1 with reference to the x%-y curve.

[0133] (6) Adjust the steam usage of reboiler 201 under actual operating conditions to 29.5 kg / h, so that the regenerated gas CO2 flow rate is 20% of the regenerated gas CO2 flow rate under the reference operating conditions. Adjust the steam extraction rate of reboiler 201 based on the steam usage of reboiler 201. Optionally, this includes: recording the steam usage of reboiler 201 when the regenerated gas CO2 flow rate is x% of the regenerated gas CO2 flow rate under the reference operating conditions, denoted as z. Plot the x%-z curve based on different actual operating conditions, and subsequently adjust the steam extraction rate of reboiler 201 with reference to the x%-z curve.

[0134] The changes in indicators at 0 min, 30 min, 1 h, 1 h 30 min, 2 h, 2 h 30 min, 3 h, 3 h 30 min, and 4 h after changing operating conditions were tested and recorded. The CO2 capture rate over time was 90.1%, 88.9%, 89.3%, 90.4%, 91.1%, 90.9%, 90.8%, 90.6%, and 90.7%, respectively. The CO2 load of the lean solution over time was 0.251, 0.257, 0.255, 0.251, 0.249, 0.251, 0.252, 0.251, and 0.253 mol CO2 / mol MEA, respectively. The CO2 load of the rich solution over time was 0.531, 0.523, 0.526, 0.533, 0.531, 0.530, 0.530, 0.532, and 0.531 mol CO2 / mol MEA, respectively. It can be seen that the system's capture rate and lean / rich liquid load tend to stabilize throughout the entire variable operating condition period, and it can still operate at 20% of the rated CO2 flow rate of the flue gas. At 20% of the rated CO2 flow rate of the flue gas, the system's regeneration gas CO2 flow rate is 6.5 Nm³. 3 / h, the regeneration energy consumption is 5.22GJ / tCO2.

[0135] Example 3

[0136] This embodiment provides a chemical absorption carbon capture system suitable for variable loads, the structure of which is as follows: Figure 2 As shown, the system is basically the same as that in Embodiment 1, except that: the absorption unit 1 is equipped with 2 absorption sections and 2 sets of staged reflux components, and the absorption unit 1 includes 5 sets of staged reflux components.

[0137] Specifically, the absorption unit 1 includes five absorption sections, from bottom to top: a first absorption section 101, a second absorption section 102, a third absorption section 103, a fourth absorption section 112, and a fifth absorption section 113; each absorption section is equipped with packing material; the absorption unit 1 includes five sets of staged reflux assemblies, each set of staged reflux assemblies including at least an absorption unit reflux pipeline; a first collection tank 104 is located below the first absorption section 101, the first collection tank 104 is connected to the fifth-stage reflux outlet of the absorption unit, and a [missing information - likely a conduit or structure] is located above the first absorption section 101. The absorption unit has a fifth-stage reflux inlet and an absorption unit fifth-stage reflux outlet connected to the absorption unit fifth-stage reflux inlet via an absorption unit fifth-stage reflux pipeline 117 outside the absorption unit 1; a second collection tank 106 is provided below the second absorption section 102, and the second collection tank 106 is connected to the absorption unit fourth-stage reflux outlet; a fourth-stage reflux inlet is provided above the second absorption section 102, and the absorption unit fourth-stage reflux outlet is connected to the absorption unit fourth-stage reflux inlet via an absorption unit fourth-stage reflux pipeline 115 outside the absorption unit 1; the third absorption section 103... A third collection tank 108 is installed below, connected to the third-stage reflux outlet of the absorption unit. A third-stage reflux inlet of the absorption unit is installed above the third absorption section 103. The third-stage reflux outlet of the absorption unit is connected to the third-stage reflux inlet of the absorption unit via a third-stage reflux pipeline 105 outside the absorption unit 1. A seventh collection tank 114 is installed below the fourth absorption section 112, connected to the second-stage reflux outlet of the absorption unit. A second-stage reflux inlet of the absorption unit is installed above the fourth absorption section 112. The reflux outlet is connected to the secondary reflux inlet of the absorption unit via the secondary reflux pipeline 107 outside the absorption unit 1; an eighth collection tank 116 is provided below the fifth absorption section 113, and the eighth collection tank 116 is connected to the primary reflux outlet of the absorption unit; a primary reflux inlet of the absorption unit is provided above the fifth absorption section 113, and the primary reflux outlet of the absorption unit is connected to the primary reflux inlet of the absorption unit via the primary reflux pipeline 109 outside the absorption unit 1; all collection tanks are provided with outlets for the absorbent to flow downwards;

[0138] An interstage cooler 110 is installed on the three-stage return pipeline 105 of the absorption unit, and an interstage cooling absorbent inlet is provided between the four-stage return inlet and the three-stage return outlet of the absorption unit. The three-stage return pipeline 105 of the absorption unit is divided into two branch pipelines at the rear end of the interstage cooler 110. One branch pipeline is connected to the three-stage return inlet of the absorption unit (for upward return), and the other branch pipeline is connected to the interstage cooling absorbent inlet (for downward return).

[0139] The absorption unit 1 and desorption unit 2 are the absorption tower and desorption tower, respectively, both with a tower diameter of 300 mm. The total height of the packing in the absorption unit 1 is 21 m (the bottom three sections of packing are 5 m each, and the top two sections are 3 m each), and the total height of the packing in the desorption unit 2 is 9 m (each section of packing is 3 m). The packing in both the absorption unit 1 and the desorption unit 2 is conventional packing in the art; in this embodiment, Mellapak 250Y stainless steel packing is specifically used.

[0140] All collection tanks have a liquid storage function; when the liquid level falls below a set value, the absorbent stops flowing downwards. The set liquid level for all collection tanks is 0.05m. 3 .

[0141] The lean liquid inlet of absorption unit 1 and the primary reflux inlet of the absorption unit above the fifth absorption section 113 are the same inlet.

[0142] A lean liquid cooler 111 is installed on the pipeline connected to the lean liquid inlet of absorption unit 1.

[0143] The staged reflux assembly of absorption unit 1 further includes several delivery pumps, which are respectively installed on the fifth-stage reflux pipeline 117, the fourth-stage reflux pipeline 115, the third-stage reflux pipeline 105, the second-stage reflux pipeline 107, and the first-stage reflux pipeline 109 of absorption unit.

[0144] A transfer pump is installed on the pipeline connecting the rich liquid outlet of absorption unit 1 to heat exchange unit 3, and a transfer pump is installed on the pipeline connecting the lean liquid outlet of desorption unit 2 to heat exchange unit 3.

[0145] This embodiment also provides a chemical absorption carbon capture method suitable for variable loads, which uses the system described above. The rated flue gas treatment capacity (i.e., flow rate) is 300 Nm³. 3 The flue gas CO2 concentration is 12 vol.%, the CO2 capture rate is set at 90%, and the rated regeneration gas CO2 flow rate is 32.4 Nm³ / h. 3 The absorbent used is a 30wt.% MEA aqueous solution, and the system absorbent loading is 1.5t.

[0146] The method includes the following steps:

[0147] S1: The flue gas enters the absorption unit 1 and comes into countercurrent contact with the lean liquid to absorb CO2 in the flue gas, thus obtaining treated flue gas and rich liquid.

[0148] S2: The rich liquid enters the desorption unit 2 after exchanging heat with the lean liquid in the heat exchange unit 3. The rich liquid is regenerated by the steam in the reboiler 201 and CO2 is released to obtain regenerated gas and lean liquid. The lean liquid enters the absorption unit 1 after exchanging heat with the rich liquid in the heat exchange unit 3.

[0149] S3: (1) Close all the staged recirculation components of absorption unit 1 and desorption unit 2, and take the operating condition after the power generation load reaches stability as the benchmark operating condition. Record the benchmark indicators under the benchmark operating condition, which include: flue gas CO2 flow rate at the flue gas inlet of absorption unit 1 (calculated by flue gas flow rate × flue gas CO2 concentration), lean liquid mainstream flow rate, rich liquid mainstream flow rate and regenerated gas CO2 flow rate; wherein, the lean liquid mainstream flow rate is the lean liquid flow rate in the pipeline connecting the lean liquid outlet of heat exchange unit 3 and desorption unit 2, and the rich liquid mainstream flow rate is the rich liquid flow rate in the pipeline connecting the rich liquid outlet of heat exchange unit 3 and absorption unit 1; the flue gas flow rate at the flue gas inlet of absorption unit 1 under the benchmark operating condition is 300 Nm 3 At a flow rate of 12.0 vol.% in the flue gas CO2 concentration, the steam usage of reboiler 201 is 112 kg / h, and the lean liquor mainstream flow rate is 1.14 m³ / h. 3 / h, the lean solution CO2 loading is 0.266 mol CO2 / mol MEA, and the rich solution mainstream flow rate is 1.25 m³ / h. 3 The CO2 loading rate of the rich liquid is 0.545 mol CO2 / mol MEA, the CO2 capture rate is 89.8%, and the CO2 flow rate of the regenerated gas is 32.4 Nm³ / h. 3 / h, the regeneration energy consumption is 3.97GJ / t CO2;

[0150] (2) Then change the operating conditions and switch the flue gas CO2 flow rate to 50% of the rated flue gas CO2 flow rate (the rated flue gas CO2 flow rate is the flue gas CO2 flow rate under the reference operating conditions). The flue gas CO2 concentration is tested to be 12.0 vol.%, which means that the ratio of the flue gas CO2 flow rate at the flue gas inlet of absorption unit 1 under the actual operating conditions when the power generation load changes to the flue gas CO2 flow rate at the flue gas inlet under the reference operating conditions is recorded as 50% (i.e. x%).

[0151] (3) Adjust the lean liquid mainstream flow rate under actual operating conditions to 50% of the lean liquid mainstream flow rate under the reference operating conditions, i.e., 0.57m. 3 / h, adjust the mainstream flow rate of the rich liquid under actual operating conditions to 50% of the mainstream flow rate of the rich liquid under the reference operating conditions, i.e., 0.625m 3 / h, adjust the steam consumption of reboiler 201 under actual operating conditions to 50% of the steam consumption of reboiler 201 under reference operating conditions, i.e. 56kg / h.

[0152] (4) Simultaneously activate the staged reflux assembly of desorption unit 2, and adjust the reflux flow rates of each stage in desorption unit 2 under actual operating conditions (i.e., the flow rates in the tertiary reflux pipeline 206, the secondary reflux pipeline 208, and the primary reflux pipeline 210 of the desorption unit) to be 100%-50% (i.e., 100%-x%) of the mainstream flow rate of the rich liquid under the reference operating conditions, i.e., 0.63m 3 / h;

[0153] (5) Then, turn on the staged reflux assembly of absorption unit 1. First, adjust the reflux flow rates of each stage of absorption unit 1 under actual operating conditions (i.e., the flow rates in the fifth-stage reflux pipeline 117, the fourth-stage reflux pipeline 115, the third-stage reflux pipeline 105, the second-stage reflux pipeline 107, and the first-stage reflux pipeline 109 of absorption unit) to be 100%-50% of the mainstream flow rate of lean liquid under the reference operating conditions, i.e., 0.57m. 3 / h, then adjust the recirculation flow rate of each stage of absorption unit 1 under actual operating conditions to achieve a CO2 capture rate of 90%, at which point the recirculation flow rate of each stage of absorption unit 1 is 0.51m. 3 / h; and when the change in power generation load causes the flue gas treatment volume entering absorption unit 1 to change, the lean liquid CO2 load and rich liquid CO2 load remain basically unchanged; selectively including: recording the recirculation flow rate of each stage of absorption unit 1 when the CO2 capture rate reaches the set value, denoted as y, and drawing the x%-y curve based on different actual operating conditions, and subsequently adjusting the recirculation flow rate of each stage of absorption unit 1 with reference to the x%-y curve.

[0154] (6) Continue to adjust the steam usage of reboiler 201 under actual operating conditions to 59 kg / h, so that the regenerated gas CO2 flow rate is 50% of the regenerated gas CO2 flow rate under the reference operating conditions. Adjust the steam extraction rate of reboiler 201 based on the steam usage of reboiler 201. Optionally, this includes: recording the steam usage of reboiler 201 when the regenerated gas CO2 flow rate is x% of the regenerated gas CO2 flow rate under the reference operating conditions, denoted as z. Plot the x%-z curve based on different actual operating conditions, and subsequently adjust the steam extraction rate of reboiler 201 with reference to the x%-z curve.

[0155] The changes in indicators were tested and recorded at 15 min, 30 min, 1 h, and 2 h after changing operating conditions. The CO2 capture rate was 90.1%, 90.3%, 90.4%, and 90.3% over time, respectively. The lean liquid CO2 load was 0.265, 0.266, 0.264, and 0.264 mol CO2 / mol MEA over time, respectively, and the rich liquid CO2 load was 0.544, 0.545, 0.543, and 0.545 mol CO2 / mol MEA over time, respectively. It can be seen that the capture rate and lean / rich liquid loads tend to stabilize within 15 min under changing operating conditions, and the system's equilibrium adjustment time is extremely short. The measured CO2 flow rate of the regenerated gas under 50% of the rated CO2 flow rate of the flue gas was 16.2 Nm³. 3 / h, the regeneration energy consumption is 4.22GJ / t CO2.

[0156] In this embodiment, the flue gas CO2 flow rate was then switched from 50% of the rated flow rate back to 100% of the rated flow rate, and the tested flue gas CO2 concentration was 12.0 vol.%.

[0157] At this point, the above method further includes:

[0158] Adjust the lean liquor mainstream flow rate, the rich liquor mainstream flow rate, and the steam usage of reboiler 201 back to the values ​​under the baseline operating conditions, i.e., adjust the lean liquor mainstream flow rate to 1.15m³ / h. 3 / h, the mainstream flow rate of the rich solution is 1.26m³ / h. 3 The steam usage of reboiler 201 is 111 kg / h. At the same time, the staged reflux components of absorption unit 1 and desorption unit 2 are all shut down. Thus, when the amount of flue gas entering absorption unit 1 changes due to changes in power generation load, the lean liquid CO2 load and rich liquid CO2 load remain basically unchanged.

[0159] The changes in indicators were tested and recorded at 15 min, 30 min, 1 h, and 2 h after the system was operating under varying conditions. The CO2 capture rate was 90.4%, 90.3%, 90.5%, and 90.4% over time, respectively. The CO2 load of the lean solution was 0.261, 0.263, 0.262, and 0.264 mol CO2 / mol MEA over time, respectively, and the CO2 load of the rich solution was 0.545, 0.546, 0.546, and 0.546 mol CO2 / mol MEA over time, respectively. It can be seen that the capture rate and the lean and rich solution loads tend to stabilize within 15 min under varying conditions, with a regenerated gas CO2 flow rate of 32.5 Nm³. 3 The system regeneration energy consumption is 3.94 GJ / t CO2 per hour.

[0160] Example 4

[0161] This embodiment provides a chemical absorption carbon capture system suitable for variable loads, the structure of which is as follows: Figure 3 As shown, the system is basically the same as that in Embodiment 1, except that the two absorption sections at the bottom inside the absorption unit 1 are merged into a single reflux stage, and the two desorption sections at the bottom inside the desorption unit 2 are merged into a single reflux stage. Therefore, both the absorption unit 1 and the desorption unit 2 include two sets of staged reflux components.

[0162] Specifically, the absorption unit 1 includes three absorption sections, from bottom to top: a first absorption section 101, a second absorption section 102, and a third absorption section 103; each absorption section is equipped with packing material; the absorption unit 1 includes two sets of staged reflux assemblies, each set of staged reflux assemblies including at least an absorption unit reflux pipeline; a first collection tank 104 is located below the first absorption section 101, connected to the secondary reflux outlet of the absorption unit; a secondary reflux inlet is located above the second absorption section 102, and the secondary reflux outlet of the absorption unit connects to the absorption unit via a suction... The secondary reflux pipeline 107 of the absorption unit outside the absorption unit 1 is connected to the secondary reflux inlet of the absorption unit; a third collection tank 108 is provided below the third absorption section 103, and the third collection tank 108 is connected to the primary reflux outlet of the absorption unit; a primary reflux inlet of the absorption unit is provided above the third absorption section 103, and the primary reflux outlet of the absorption unit is connected to the primary reflux inlet of the absorption unit through the primary reflux pipeline 109 outside the absorption unit 1; the first collection tank 104 and the third collection tank 108 are respectively provided with outlets for the absorbent to flow downwards;

[0163] The desorption unit 2 internally comprises three desorption sections, from bottom to top: a first desorption section 202, a second desorption section 203, and a third desorption section 204; each desorption section is equipped with packing material; the desorption unit 2 includes two sets of staged reflux assemblies, each set of staged reflux assemblies including at least a desorption unit reflux pipeline; a fourth collection tank 205 is located below the first desorption section 202, connected to the secondary reflux outlet of the desorption unit; a secondary reflux inlet is located above the second desorption section 203, and the secondary reflux outlet of the desorption unit connects to the desorption unit... The secondary reflux pipeline 208 of the desorption unit outside unit 2 is connected to the secondary reflux inlet of the desorption unit; a sixth collection tank 209 is provided below the third desorption section 204, and the sixth collection tank 209 is connected to the primary reflux outlet of the desorption unit; a primary reflux inlet of the desorption unit is provided above the third desorption section 204, and the primary reflux outlet of the desorption unit is connected to the primary reflux inlet of the desorption unit through the primary reflux pipeline 210 of the desorption unit outside unit 2; the fourth collection tank 205 and the sixth collection tank 209 are respectively provided with outlets for the absorbent to flow downwards.

[0164] The absorption unit 1 and desorption unit 2 are the absorption tower and desorption tower, respectively, both with a tower diameter of 300 mm. The total height of the packing in the absorption unit 1 is 15 m (5 m per section), and the total height of the packing in the desorption unit 2 is 9 m (3 m per section). The packing in both the absorption unit 1 and the desorption unit 2 is conventional packing in the art; in this embodiment, Mellapak 250Y stainless steel packing is specifically used.

[0165] All collection tanks have a liquid storage function; when the liquid level falls below a set value, the absorbent stops flowing downwards. The set liquid level for all collection tanks is 0.05m. 3 .

[0166] The lean liquid inlet of absorption unit 1 and the primary reflux inlet of the absorption unit above the third absorption section 103 are the same inlet.

[0167] A lean liquid cooler 111 is installed on the pipeline connected to the lean liquid inlet of absorption unit 1.

[0168] The staged reflux assembly in absorption unit 1 and desorption unit 2 further includes several delivery pumps, which are respectively installed on the secondary reflux pipeline 107 of absorption unit, the primary reflux pipeline 109 of absorption unit, the secondary reflux pipeline 208 of desorption unit, and the primary reflux pipeline 210 of desorption unit.

[0169] A transfer pump is installed on the pipeline connecting the rich liquid outlet of absorption unit 1 to heat exchange unit 3, and a transfer pump is installed on the pipeline connecting the lean liquid outlet of desorption unit 2 to heat exchange unit 3.

[0170] This embodiment provides a chemical absorption carbon capture method suitable for variable loads, which employs the system described above. The rated flue gas treatment capacity (i.e., flow rate) is 300 Nm³. 3 The flue gas CO2 concentration is 12 vol.%, the CO2 capture rate is set at 90%, and the rated regeneration gas CO2 flow rate is 32.4 Nm³ / h. 3 The absorbent used is a 30wt.% MEA aqueous solution, and the system absorbent loading is 1.5t.

[0171] This method is basically the same as that in Example 2, and specifically includes the following steps:

[0172] S1: The flue gas enters the absorption unit 1 and comes into countercurrent contact with the lean liquid to absorb CO2 in the flue gas, thus obtaining treated flue gas and rich liquid.

[0173] S2: The rich liquid enters the desorption unit 2 after exchanging heat with the lean liquid in the heat exchange unit 3. The rich liquid is regenerated by the steam in the reboiler 201 and CO2 is released to obtain regenerated gas and lean liquid. The lean liquid enters the absorption unit 1 after exchanging heat with the rich liquid in the heat exchange unit 3.

[0174] S3: (1) Close all the staged reflux components of absorption unit 1 and desorption unit 2, and take the operating condition after the 100% power generation load reaches stability as the benchmark operating condition. Record the benchmark indicators under the benchmark operating condition, which include: flue gas CO2 flow rate at the flue gas inlet of absorption unit 1, lean liquid mainstream flow rate, rich liquid mainstream flow rate and regenerated gas CO2 flow rate; wherein, the lean liquid mainstream flow rate is the lean liquid flow rate in the pipeline connecting the heat exchange unit 3 and the lean liquid outlet of desorption unit 2, and the rich liquid mainstream flow rate is the rich liquid flow rate in the pipeline connecting the heat exchange unit 3 and the rich liquid outlet of absorption unit 1; the flue gas flow rate at the flue gas inlet of absorption unit 1 under the benchmark operating condition is 300 Nm 3 At a flow rate of 12.0 vol.% in the flue gas CO2 concentration, the steam usage of reboiler 201 is 115 kg / h, and the lean liquor mainstream flow rate is 1.15 m³ / h. 3 / h, the lean solution CO2 loading is 0.253 mol CO2 / mol MEA, and the rich solution mainstream flow rate is 1.26 m³ / h. 3 The CO2 loading rate of the rich liquid was 0.534 mol CO2 / mol MEA, the CO2 capture rate was 90.1%, and the CO2 flow rate of the regenerated gas was 32.3 Nm³ / h. 3 / h, the regeneration energy consumption is 4.07GJ / t CO2;

[0175] (2) Then the operating conditions were changed so that the flue gas CO2 flow rate slowly decreased from 100% of the rated flow rate. After 2 hours, it decreased to 20% of the rated flow rate and remained stable. The flue gas CO2 concentration was tested to be about 12 vol.% during the whole process. That is, the ratio of the flue gas CO2 flow rate at the flue gas inlet of absorption unit 1 under the actual operating conditions when the power generation load changes to the flue gas CO2 flow rate at the flue gas inlet under the reference operating conditions is recorded as 20% (i.e. x%).

[0176] (3) Adjust the lean liquid mainstream flow rate under actual operating conditions to 20% of the lean liquid mainstream flow rate under the reference operating conditions, i.e., 0.23m. 3 / h, adjust the mainstream flow rate of the rich liquid under actual operating conditions to 20% of the mainstream flow rate of the rich liquid under the reference operating conditions, i.e., 0.25m 3 / h;

[0177] (4) Simultaneously, when the flue gas CO2 flow rate is lower than 90% of the baseline operating condition, the staged reflux assembly of desorption unit 2 is activated, and the reflux flow rates of each stage of desorption unit 2 under actual operating conditions (i.e., the flow rates in the tertiary reflux pipeline 206, the secondary reflux pipeline 208, and the primary reflux pipeline 210 of the desorption unit) are adjusted to be 100%-20% (i.e., 100%-x%) of the mainstream flow rate of the rich liquid under the baseline operating condition, i.e., 1.01m 3 / h, the reflux flow rate of each stage in desorption unit 2 is all from 0.12m³ / h. 3 / h increased to 1.01m over time. 3 / h and stable;

[0178] (5) Then, turn on the staged reflux assembly of absorption unit 1 and adjust the reflux flow rates of each stage of absorption unit 1 under actual operating conditions (i.e., the flow rates in the third-stage reflux pipeline 105, the second-stage reflux pipeline 107, and the first-stage reflux pipeline 109 of absorption unit) so that the CO2 capture rate reaches the set value of 90%. At this time, the reflux flow rates of each stage of absorption unit 1 are all adjusted from 0.10 m³ / s. 3 / h rose to 0.92m 3 / h; and when the change in power generation load causes the flue gas treatment volume entering absorption unit 1 to change, the lean liquid CO2 load and rich liquid CO2 load remain basically unchanged; selectively including: recording the recirculation flow rate of each stage of absorption unit 1 when the CO2 capture rate reaches the set value, denoted as y, and drawing the x%-y curve based on different actual operating conditions, and subsequently adjusting the recirculation flow rate of each stage of absorption unit 1 with reference to the x%-y curve.

[0179] (6) Adjust the steam usage of reboiler 201 under actual operating conditions to 30.7 kg / h, so that the regenerated gas CO2 flow rate is 20% of the regenerated gas CO2 flow rate under the reference operating conditions. Adjust the steam extraction rate of reboiler 201 based on the steam usage of reboiler 201. Optionally, record the steam usage of reboiler 201 when the regenerated gas CO2 flow rate is x% of the regenerated gas CO2 flow rate under the reference operating conditions, denoted as z. Plot the x%-z curve based on different actual operating conditions, and subsequently adjust the steam extraction rate of reboiler 201 with reference to the x%-z curve.

[0180] The changes in indicators at 0 min, 30 min, 1 h, 1 h 30 min, 2 h, 2 h 30 min, 3 h, 3 h 30 min, and 4 h after changing operating conditions were tested and recorded. The CO2 capture rate over time was 90.1%, 88.9%, 89.3%, 90.4%, 91.1%, 90.9%, 90.8%, 90.6%, and 90.7%, respectively. The CO2 load of the lean solution over time was 0.250, 0.248, 0.246, 0.242, 0.243, 0.242, 0.241, 0.243, and 0.242 mol CO2 / mol MEA, respectively. The CO2 load of the rich solution over time was 0.530, 0.528, 0.523, 0.522, 0.520, 0.520, 0.522, 0.521, and 0.520 mol CO2 / mol MEA, respectively. It can be seen that the system's capture rate and lean / rich liquid load tend to stabilize throughout the entire variable operating condition period, and it can still operate at 20% of the rated CO2 flow rate of the flue gas. At 20% of the rated CO2 flow rate of the flue gas, the system's regeneration gas CO2 flow rate is 6.5 Nm³. 3The regeneration energy consumption is 5.43 GJ / tCO2 per hour. This is an increase in regeneration energy consumption compared to Example 2.

[0181] Comparative Example 1

[0182] This comparative example provides a chemical absorption carbon capture method suitable for variable loads, using the system of Example 1. The rated flue gas treatment capacity (i.e., flow rate) is 300 Nm³. 3 The flue gas CO2 concentration is 12 vol.%, the CO2 capture rate is set at 90%, and the rated regeneration gas CO2 flow rate is 32.4 Nm³ / h. 3 The absorbent used is a 30wt.% MEA aqueous solution, and the system absorbent loading is 1.5t.

[0183] This method employs conventional processes, with the staged reflux components of absorption unit 1 and desorption unit 2 always kept in a closed state.

[0184] The method includes the following steps:

[0185] S1: The flue gas enters the absorption unit 1 and comes into countercurrent contact with the lean liquid to absorb CO2 in the flue gas, thus obtaining treated flue gas and rich liquid.

[0186] S2: The rich liquid enters the desorption unit 2 after exchanging heat with the lean liquid in the heat exchange unit 3. The rich liquid is regenerated by the steam in the reboiler 201 and CO2 is released to obtain regenerated gas and lean liquid. The lean liquid enters the absorption unit 1 after exchanging heat with the rich liquid in the heat exchange unit 3.

[0187] S3: (1) All staged recirculation components of absorption unit 1 and desorption unit 2 are kept closed. The operating condition after 100% power generation load reaches stability is taken as the baseline operating condition. The baseline index under the baseline operating condition is recorded. The flue gas flow rate at the flue gas inlet of absorption unit 1 under the baseline operating condition is 300 Nm³. 3 At this time, the steam usage of reboiler 201 is 115 kg / h, and the mainstream flow rate of lean liquor is 1.15 m³ / h. The CO2 concentration in the flue gas is 12.3 vol.%. 3 / h, the lean solution CO2 loading is 0.251 mol CO2 / mol MEA, and the rich solution mainstream flow rate is 1.26 m³ / h. 3 The CO2 loading rate of the rich liquid is 0.532 mol CO2 / mol MEA, the CO2 capture rate is 90.4%, and the CO2 flow rate of the regenerated gas is 32.5 Nm³ / h. 3 / h, the regeneration energy consumption is 4.07GJ / tCO2;

[0188] (2) Then, the operating conditions were changed, and the flue gas CO2 flow rate was switched to 50% of the rated flue gas CO2 flow rate (the rated flue gas CO2 flow rate is the flue gas CO2 flow rate under the baseline operating conditions). The tested flue gas CO2 concentration was 11.9 vol.%, and the lean liquor mainstream flow rate was adjusted to 0.81 m³ / s. 3 / h, the mainstream flow rate of the rich solution is 0.88m³ / h. 3 The steam consumption of reboiler 201 is 62 kg / h. The changes in indicators after changing operating conditions were tested and recorded at 15 min, 30 min, 1 h, 2 h, 3 h, and 4 h. The CO2 capture rate over time was 99.3%, 98.8%, 98.1%, 93.3%, 91.1%, and 90.8%, respectively. The lean liquor CO2 load over time was 0.254, 0.253, 0.262, 0.277, 0.284, and 0.283 mol CO2 / mol MEA, respectively. The rich liquor CO2 load over time was 0.531, 0.528, 0.514, 0.494, 0.486, and 0.484 mol CO2 / mol MEA, respectively. It can be seen that the capture rate and lean / rich liquor loads tend to stabilize 3-4 h after changing operating conditions. The CO2 flow rate of the regenerated gas at 50% of the rated CO2 flow rate of the flue gas is 16.3 Nm³. 3 / h, the regeneration energy consumption is 4.41GJ / t CO2;

[0189] (3) Then, the operating conditions were changed again, and the flue gas CO2 flow rate was switched back to 100% of the rated flue gas CO2 flow rate. The tested flue gas CO2 concentration was 12.1 vol.%, and the lean liquor mainstream flow rate was adjusted to 1.15 m³ / s. 3 / h, the mainstream flow rate of the rich solution is 1.26m³ / h. 3 The steam consumption of reboiler 201 is 115 kg / h. The changes in indicators after changing operating conditions were tested and recorded at 15 min, 30 min, 1 h, 2 h, 3 h, and 4 h. The CO2 capture rate over time was 77.5%, 78.8%, 82.6%, 86.3%, 89.9%, and 90.3%, respectively. The lean liquor CO2 load over time was 0.281, 0.279, 0.272, 0.257, 0.252, and 0.253 mol CO2 / mol MEA, respectively. The rich liquor CO2 load over time was 0.487, 0.487, 0.501, 0.521, 0.528, and 0.531 mol CO2 / mol MEA, respectively. It can be seen that the capture rate and lean / rich liquor loads tend to stabilize 3-4 h after changing operating conditions. During the changing operating conditions, the capture rate does not meet the standard. When stable, the system regeneration gas CO2 flow rate is 16.1 Nm³. 3 / h, the regeneration energy consumption is 4.08GJ / t CO2.

Claims

1. A chemical absorption carbon capture method suitable for variable loads, the method comprising the following steps: S1: The flue gas enters the absorption unit and comes into countercurrent contact with the lean liquid to absorb CO2 in the flue gas, thus obtaining treated flue gas and rich liquid. S2: The rich liquid enters the desorption unit after exchanging heat with the lean liquid in the heat exchange unit. The rich liquid is regenerated by the steam in the reboiler and CO2 is released to obtain regenerated gas and lean liquid. The lean liquid enters the absorption unit after exchanging heat with the rich liquid in the heat exchange unit. S3: The absorbent in the absorption unit and the desorption unit is refluxed in at least two stages using a staged reflux assembly. By adjusting the lean liquid flow rate and the rich liquid flow rate, the CO2 load of the lean liquid and the CO2 load of the rich liquid remain basically unchanged when the amount of flue gas treated in the absorption unit changes due to changes in the power generation load. The absorption unit includes at least two absorption sections and at least two sets of staged reflux assemblies. The staged reflux assembly includes at least an absorption unit reflux pipeline. The absorption unit reflux pipeline is used to allow the absorbent to reflux from below an absorption section to above it or to reflux to above an absorption section above the absorption section. The desorption unit includes at least two desorption sections and at least two sets of staged reflux assemblies. The staged reflux assembly includes at least a desorption unit reflux pipeline. The desorption unit reflux pipeline is used to allow the absorbent to reflux from below a certain desorption section to above it or to reflux to above a desorption section above the certain desorption section. Step S3 includes: when the change in power generation load causes a change in the amount of flue gas entering the absorption unit, assuming that the CO2 flow rate of the flue gas at the flue gas inlet of the absorption unit is x% of the flow rate before the change in power generation load, the mainstream flow rates of lean liquid and rich liquid are adjusted to x% of the flow rate before the change in power generation load, and the staged reflux components of the desorption unit are turned on, and the reflux flow rates of each stage of the desorption unit are adjusted to 100%-x% of the mainstream flow rate of rich liquid before the change in power generation load. Then, the staged reflux components of the absorption unit are turned on, and the reflux flow rates of each stage of the absorption unit are adjusted so that the CO2 capture rate reaches the set value.

2. The method according to claim 1, wherein, Step S3 specifically includes: (1) All staged reflux components of the absorption unit and desorption unit are shut down or kept at the minimum flow rate. The operating condition after 100% power generation load reaches stability is taken as the benchmark operating condition. The benchmark indicators under the benchmark operating condition are recorded, including: flue gas CO2 flow rate at the flue gas inlet of the absorption unit, lean liquid mainstream flow rate and rich liquid mainstream flow rate; wherein, the lean liquid mainstream flow rate is the lean liquid flow rate in the pipeline connecting the lean liquid outlet of the heat exchange unit and the desorption unit, and the rich liquid mainstream flow rate is the rich liquid flow rate in the pipeline connecting the rich liquid outlet of the heat exchange unit and the absorption unit. (2) Calculate the ratio of the flue gas CO2 flow rate at the flue gas inlet of the absorption unit under actual operating conditions when the power generation load changes to the flue gas CO2 flow rate at the flue gas inlet under the baseline operating conditions, and denote it as x%; (3) Adjust the lean liquor mainstream flow rate under actual operating conditions to x% of the lean liquor mainstream flow rate under the benchmark operating conditions, and adjust the rich liquor mainstream flow rate under actual operating conditions to x% of the rich liquor mainstream flow rate under the benchmark operating conditions; (4) Simultaneously turn on the staged reflux assembly of the desorption unit, and adjust the reflux flow rate of each stage of the desorption unit under actual operating conditions to be 100%-x% of the mainstream flow rate of the rich liquid under the reference operating conditions. (5) Then turn on the staged recirculation component of the absorption unit and adjust the recirculation flow rate of each stage of the absorption unit under actual operating conditions so that the CO2 capture rate reaches the set value; then when the power generation load changes and the amount of flue gas entering the absorption unit changes, keep the lean liquid CO2 load and the rich liquid CO2 load basically unchanged.

3. The method according to claim 1 or 2, wherein, In step S3, the CO2 capture rate is set to 90%.

4. The method according to claim 2, wherein, In step S3 (4), when the CO2 flow rate of the flue gas at the flue gas inlet of the absorption unit is lower than 90% of the CO2 flow rate of the flue gas at the flue gas inlet under the reference operating conditions, the staged reflux component of the desorption unit is turned on.

5. The method according to claim 2, wherein, In step S3 (5), after turning on the staged reflux assembly of the absorption unit, first adjust the reflux flow rate of each stage of the absorption unit under actual operating conditions to be 100%-x% of the mainstream flow rate of the lean liquid under the reference operating conditions, and then adjust the reflux flow rate of each stage of the absorption unit under actual operating conditions so that the CO2 capture rate reaches the set value.

6. The method according to claim 2, wherein, Step S3 (5) further includes: recording the reflux flow rate of each stage of the absorption unit when the CO2 capture rate reaches the set value, denoted as y, drawing the x%-y curve based on different actual operating conditions, and subsequently adjusting the reflux flow rate of each stage of the absorption unit with reference to the x%-y curve.

7. The method according to claim 2, wherein, In step S3, the benchmark index under the benchmark operating condition further includes: regenerated gas CO2 flow rate; and step S3 further includes: (6) regulating the steam extraction amount of the reboiler, which specifically includes: adjusting the steam usage amount of the reboiler under the actual operating condition, so that the regenerated gas CO2 flow rate is x% of the regenerated gas CO2 flow rate under the benchmark operating condition, and regulating the steam extraction amount of the reboiler based on the steam usage amount of the reboiler.

8. The method according to claim 2, wherein, The benchmark index under the benchmark operating condition further includes: the steam usage of the reboiler; and step S3 (3) further includes: adjusting the steam usage of the reboiler under the actual operating condition to x% of the steam usage of the reboiler under the benchmark operating condition, and step S3 (6) further includes: continuing to adjust the steam usage of the reboiler under the actual operating condition so that the CO2 flow rate of the regenerated gas is x% of the CO2 flow rate of the regenerated gas under the benchmark operating condition, and adjusting the steam extraction amount of the reboiler based on the steam usage of the reboiler.

9. The method according to claim 8, wherein, Step S3 (6) further includes: recording the steam usage of the reboiler when the regenerated gas CO2 flow rate is x% of the regenerated gas CO2 flow rate under the baseline operating conditions, denoted as z, and plotting the x%-z curve based on different actual operating conditions, and subsequently adjusting the steam extraction amount of the reboiler with reference to the x%-z curve.

10. The method according to claim 2, wherein, In step S3, when the CO2 flow rate of the flue gas at the flue gas inlet of the absorption unit under actual operating conditions is more than 90% of the CO2 flow rate of the flue gas at the flue gas inlet under the reference operating conditions, the staged reflux assembly of the absorption unit and the desorption unit maintains the minimum flow rate operation; wherein, the minimum flow rates of the staged reflux assembly of the absorption unit and the desorption unit are 10% of the mainstream flow rate of the lean liquid and 10% of the mainstream flow rate of the rich liquid under the reference operating conditions, respectively.

11. The method according to claim 1, wherein, The number of sets of staged reflux components in the absorption unit is 2-10, and the number of sets of staged reflux components in the desorption unit is 2-6.

12. The method according to claim 1, wherein, The absorption section is connected to the return pipeline of the absorption unit via a collection tank located below it, and the desorption section is connected to the return pipeline of the desorption unit via a collection tank located below it. Each collection tank is provided with an outlet for the absorbent to flow downwards.

13. The method according to claim 12, wherein, The liquid collection tank has a liquid storage function. When the liquid level in the tank is lower than a set value, the absorbent in the liquid collection tank stops flowing downwards.

14. The method according to claim 1, wherein, An interstage cooler is installed on the return pipe of the absorption unit located in the middle of the absorption unit.

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