A low-energy-consumption flue gas carbon capture and removal system and process for ultra-low CO2 concentration.

Abstract

The application relates to the field of energy-saving and environment-friendly technologies, and discloses a low-energy-consumption carbon capture and removal system and process for flue gas with ultra-low CO2 concentration, which comprises a water washing tower, an absorption tower and a regeneration tower sequentially connected through pipelines; a first rich-liquid heat exchange component and a second rich-liquid heat exchange component are further connected between the absorption tower and the regeneration tower; along the direction of material flow from the absorption tower to the regeneration tower, the first rich-liquid heat exchange component comprises a lean-rich liquid heat exchanger and a lean liquid flash gas heat pump sequentially connected; and the second rich-liquid heat exchange component comprises a steam condensate water heat exchanger and a regeneration gas heat pump sequentially connected. The composite organic amine is used as an absorbent, the rich-liquid shunt multistage heat exchange and heat energy comprehensive utilization technology of the carbon capture and removal system are combined, the carbon removal efficiency can be effectively improved, the circulation amount of the absorbent can be reduced, and the regeneration energy consumption of rich-liquid desorption can be reduced.

Description

Technical Field

[0001] This invention relates to the field of energy conservation and environmental protection technology, and more specifically, to a low-energy-consumption, ultra-low CO2 concentration flue gas carbon capture and removal system and process. Background Technology

[0002] Carbon dioxide emissions mainly come from the flue gas produced by burning fossil fuels such as coal, oil, or natural gas. The most effective and common way to remove CO2 from the flue gas is the chemical absorption process using an alcohol amine solution as the absorbent.

[0003] Chemical absorption methods using aqueous solutions of alkanolamines as absorbents, with alkyl alkanolamines (MEA, MDEA, MEA-TEA) being the most commonly used, employ packed towers for absorption and desorption. While this method is widely used, it suffers from drawbacks such as low carbon capture efficiency, high energy consumption, severe equipment corrosion, oxygen-induced degradation of the absorbent, and a lack of large-scale carbon capture processes (1 million tons of CO2 / year and above).

[0004] Especially when treating flue gas with ultra-low CO2 concentrations (3-5 vol%), more challenges arise, including: low decarbonization efficiency in capturing CO2 from flue gas with low CO2 partial pressures, and high energy consumption for absorbent regeneration (accounting for more than half of the total decarbonization energy consumption). Furthermore, the commonly used alkylolamine aqueous solutions are only suitable as absorbents for treating higher CO2 concentrations (above 10 vol%). If applied to capturing flue gas with lower CO2 concentrations, the carbon capture efficiency is low, and the absorbent circulation volume is large, resulting in high energy consumption during desorption.

[0005] Therefore, there is an urgent need for a low-energy carbon capture process with a large processing capacity that can be used for flue gas with ultra-low CO2 concentration. Summary of the Invention

[0006] The technical problem to be solved by this invention:

[0007] Currently, the main method for decarbonizing flue gas after fossil fuel combustion is through chemical adsorption with absorbents. However, this method has low carbon capture efficiency, high energy consumption, and can cause problems such as equipment corrosion and adsorbent oxidation and degradation, making it unsuitable for ultra-large-scale treatment of more than 1 million tons of CO2 per year. In addition, this method is difficult to effectively remove ultra-low CO2 content when applied to the treatment of flue gas with ultra-low CO2 concentration.

[0008] The technical solution adopted in this invention is as follows:

[0009] This invention provides a low-energy-consumption, ultra-low CO2 concentration flue gas carbon capture and removal system, comprising a water scrubbing tower, an absorption tower, and a regeneration tower connected sequentially via pipelines; a first rich liquid heat exchange component and a second rich liquid heat exchange component are connected in parallel between the absorption tower and the regeneration tower, along the direction of material flow from the absorption tower to the regeneration tower. The first rich liquid heat exchange component includes a lean and rich liquid heat exchanger and a lean liquid flash steam heat pump connected sequentially, and the second rich liquid heat exchange component includes a steam condensate heat exchanger and a regeneration gas heat pump connected sequentially.

[0010] Preferably, the outlet end of the absorption tower is also connected to a rich liquid pump, and the outlet end of the rich liquid pump is connected to the lean and rich liquid heat exchanger and the steam condensate heat exchanger respectively.

[0011] Preferably, the top of the regeneration tower is connected to a CO2 separator, and the pipeline between the regeneration tower and the CO2 separator flows through the regeneration gas heat pump.

[0012] Preferably, the bottom of the regeneration tower is also connected to a first lean liquor circulation assembly, which includes a lean liquor flash tank and a lean liquor buffer tank connected in sequence. The outlet end of the lean liquor buffer tank is connected to a lean liquor cooler and a filter, respectively. The lean liquor cooler and the filter are both connected to the feed end of the absorption tower.

[0013] Preferably, the bottom of the regeneration tower is connected to a lean liquor internal circulation component, which includes a reboiler. The feed pipe and the discharge pipe of the reboiler are both connected to the bottom of the regeneration tower.

[0014] Preferably, the pipeline between the lean liquid flash evaporator and the lean liquid buffer tank is connected to the lean-rich liquid heat exchanger.

[0015] Preferably, the pipeline between the lean liquid flash evaporator and the lean liquid buffer tank is also equipped with a lean liquid pump.

[0016] The low-energy-consumption, ultra-low CO2 concentration flue gas carbon capture and removal process using the above system includes the following steps:

[0017] S1 preprocessing:

[0018] The flue gas to be treated is washed, dust removed, and cooled.

[0019] S2 CO2 capture:

[0020] The pretreated flue gas and CO2 absorbent are introduced into the absorption tower, mixed in contact, and CO2 is captured and absorbed. The captured gas is discharged from the top of the absorption tower, and a rich liquid is formed at the bottom of the absorption tower.

[0021] S3 Rich Liquid Split Heat Exchange:

[0022] The rich liquid is divided into two streams. One stream exchanges heat with the liquid phase flowing out of the lean liquid flash tank through a lean-rich liquid heat exchanger, and then exchanges heat through a lean liquid flash heat pump.

[0023] The other route first passes through a steam-condensate heat exchanger, and then through a regenerated gas heat pump for heat exchange;

[0024] The two rich solutions undergo heat exchange separately, and then are fed together into the regeneration tower for desorption.

[0025] S4 lean solution heat exchange:

[0026] The lean liquor formed in the regeneration tower is discharged from the bottom of the regeneration tower and fed into the lean liquor flash tank for treatment. The gas phase in the lean liquor flash tank exchanges heat with the rich liquor through the lean liquor flash vapor heat pump and is then sent back to the absorption tower. The liquid phase in the lean liquor flash tank first exchanges heat with the rich liquor through the lean-rich liquor heat exchanger, and then is pumped into the lean liquor buffer tank. After cooling and filtration, it is sent back to the absorption tower.

[0027] S5 CO2 separation:

[0028] The gas phase in the regeneration tower is discharged from the top, first exchanged heat with the rich liquid through the regeneration gas heat pump, and then passed into the CO2 separator for gas-liquid separation. The separated CO2-containing gas is sent to the CO2 recovery and treatment process, while the separated condensate is sent to the solution storage tank.

[0029] Preferably, in step S2, the CO2 absorbent includes a composite absorbent, an activator, an antioxidant, an antifoaming agent, and a corrosion inhibitor, wherein the composite absorbent includes triethanolamine and N-methyldiethanolamine.

[0030] Preferably, in step S3, the flow rate of the rich solution is controlled to be 3600–6000 m³ / h. 3 / h, the flow rate of the other rich solution is 1400-1600 m³ / h. 3 / h.

[0031] The beneficial effects of this invention are as follows:

[0032] This invention improves the decarbonization efficiency of ultra-low CO2 concentration flue gas and reduces CO2 capture energy consumption from the following two aspects: First, it proposes a CO2 absorbent with high-efficiency carbon capture for ultra-low CO2 concentration flue gas, which improves the CO2 absorption rate while reducing the rich liquid circulation volume and the regeneration energy consumption of rich liquid desorption. Second, it optimizes and improves the CO2 capture process by adopting multiple comprehensive energy-saving technologies, such as rich liquid diversion multi-stage heat exchange and comprehensive heat energy utilization technology, to further reduce process energy consumption.

[0033] Among them, the CO2 absorbent refers to the composite organic amine SMEA. Compared with the traditional decarbonization adsorbent, when treating the same ultra-low CO2 concentration (3-5 vol%) flue gas, the CO2 removal efficiency can be increased by 8-10%, while the absorption liquid circulation volume is reduced by 10-15%.

[0034] This invention improves and optimizes the carbon capture and removal process by employing a multi-stage heat exchange system with rich liquor diversion and comprehensive thermal energy utilization. The rich liquor is diverted and subjected to staged heat exchange, while a heat pump is used to achieve heat exchange between the rich and lean liquors. This enables highly efficient carbon removal on a large scale for flue gas with ultra-low CO2 concentrations, achieving a comprehensive energy consumption as low as 2.44–2.64 GJ / tCO2. In contrast, traditional CO2 removal processes consume as much as 3.15 GJ / tCO2. The carbon capture and removal process proposed in this invention reduces comprehensive energy consumption by 16.2–22.5%.

[0035] In summary, compared with traditional chemical absorbents and CO2 removal processes, the CO2 absorbent used in this invention can improve its absorption efficiency, reduce the absorbent circulation volume, and, by employing rich-liquid split-flow multi-stage heat exchange and comprehensive thermal energy utilization technology, reduce steam consumption and overall energy consumption. Therefore, the flue gas carbon capture and removal process provided by this invention is applicable to CO2 capture and removal treatment of ultra-low CO2 concentration flue gas, with high decarbonization efficiency and low energy consumption, and can be used for treatment scales exceeding 1 million tons of CO2 per year. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of the ultra-low CO2 concentration flue gas carbon capture and removal system of the present invention.

[0037] Attached diagram labels: 1-Water washing tower, 2-Absorption tower, 31-Rich liquid pump, 32-Rich / lean liquid heat exchanger, 33-Lean liquid flash vapor heat pump, 34-Steam condensate heat exchanger, 35-Regenerated gas heat pump, 4-Regeneration tower, 41-Reboiler, 42-CO2 separator, 51-Lean liquid flash tank, 52-Lean liquid pump, 53-Lean liquid buffer tank, 54-Lean liquid cooler, 55-Filter. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0039] This invention provides a low-energy-consumption ultra-low CO2 concentration flue gas carbon capture and removal system, comprising a water washing tower 1, an absorption tower 2, and a regeneration tower 4 connected sequentially by pipelines; a first rich liquid heat exchange component and a second rich liquid heat exchange component are connected in parallel between the absorption tower 2 and the regeneration tower 4. Along the direction of material flow from the absorption tower 2 to the regeneration tower 4, the first rich liquid heat exchange component includes a lean and rich liquid heat exchanger 32 and a lean liquid flash steam heat pump 33 connected sequentially, and the second rich liquid heat exchange component includes a steam condensate heat exchanger 34 and a regeneration gas heat pump 35 connected sequentially.

[0040] In this invention, an induced draft fan is connected between the water washing tower 1 and the absorption tower 2 to pressurize the flue gas; the feed pipe at the top of the absorption tower 2 for introducing CO2 absorbent is also equipped with a flow meter and a flow valve to monitor and regulate the flow rate of the CO2 absorbent.

[0041] In this invention, the outlet end of the absorption tower 2 is also connected to a rich liquid pump 31, and the outlet end of the rich liquid pump 31 is connected to the lean and rich liquid heat exchanger 32 and the steam condensate heat exchanger 34, respectively.

[0042] In this invention, the bottom of the regeneration tower 4 is also connected to a first lean liquor circulation assembly. The first lean liquor circulation assembly includes a lean liquor flash tank 51 and a lean liquor buffer tank 53 connected in sequence. The outlet end of the lean liquor buffer tank 53 is connected to a lean liquor cooler 54 and a filter 55, respectively. Both the lean liquor cooler 54 and the filter 55 are connected to the inlet end of the absorption tower 2. Among them, the filter 55 can be multiple filters 55 connected in series, such as a particle filter 55 and an activated carbon filter 55, for multi-stage filtration.

[0043] In this invention, the bottom of the regeneration tower 4 is connected to a lean liquid internal circulation component, which includes a reboiler 41. The feed pipe and the discharge pipe of the reboiler 41 are both connected to the bottom of the regeneration tower 4 to realize the internal circulation of lean liquid in the regeneration tower 4.

[0044] In this invention, the pipeline between the lean liquid flash evaporator 51 and the lean liquid buffer tank 53 is connected to the lean and rich liquid heat exchanger 32.

[0045] In this invention, a lean liquid pump 52 is also provided in the pipeline between the lean liquid flash evaporator 51 and the lean liquid buffer tank 53.

[0046] In this invention, the top of the regeneration tower 4 is connected to a CO2 separator 42, and the pipeline between the regeneration tower 4 and the CO2 separator 42 flows through the regeneration gas heat pump 35.

[0047] In this invention, each device is equipped with a thermometer to detect the temperature changes of the materials inside the device in real time, which facilitates operation and measurement by the operators.

[0048] This invention provides a low-energy-consumption process for ultra-low CO2 concentration flue gas carbon capture and removal using the aforementioned ultra-low CO2 concentration flue gas carbon capture and removal system, comprising the following steps:

[0049] (1) Pretreatment: The flue gas containing ultra-low concentration CO2 is introduced into water washing tower 1 for washing, dust removal and cooling;

[0050] During this process, the temperature of the flue gas entering the water scrubbing tower 1 is controlled at 115–130℃, the pressure at 150–160 kPa (absolute pressure), and the flue gas flow rate into the tower is 150 × 10⁻⁶ kPa. 4 -180×10 4 Nm 3 / h, after washing and dust removal, the temperature is reduced to 40-45℃;

[0051] The inlet water temperature of the water washing tower 1 is 25-40℃, which allows the flue gas to be fully cooled after passing through the water washing tower 1. The used washing water can be pressurized and transported to the washing water cooler by the washing water pump. After cooling, it can be returned to the water washing tower 1 for recycling, or the washing water can be recycled through the circulating water network.

[0052] (2) CO2 capture: After pretreatment, the flue gas is introduced into the absorption tower 2, and CO2 absorbent is continuously introduced into the absorption tower 2. The raw gas and CO2 absorbent are mixed and captured and absorbed. The purified gas after treatment is discharged from the top of the absorption tower 2, and the liquid phase formed in the absorption tower 2 is discharged from the bottom of the absorption tower 2.

[0053] Among them, the CO2 absorbent flow rate is controlled at 5000–7500 m³ / h. 3 / h, the CO2 absorbent uses a composite organic amine SMEA, specifically including: composite absorbent, activator, antioxidant, defoamer, and corrosion inhibitor; the composite absorbent includes 60-70% triethanolamine (TEA) and 30-40% N-methyldiethanolamine (MDEA), the activator includes 1-10% piperazine and 0.1-1% diethylene glycolamine, the antioxidant is 0.1-0.5% sodium metavanadate (NaVO3), the defoamer is a polyether-type defoamer, and the corrosion inhibitor is 0.1-0.3% potassium dichromate (all by mass fraction);

[0054] After treatment by absorption tower 2, the CO2 content in the purified flue gas can be lower than 0.28 vol%, meaning the CO2 removal rate can be as high as 88-92%.

[0055] (3) Rich liquid diversion heat exchange: The liquid phase discharged from the bottom of the absorption tower 2 is discharged through the rich liquid pump 31 and divided into two streams:

[0056] One of the routes is rich in solution, with a concentration of 3600–6000 m. 3The flow rate of / h first exchanges heat with the liquid phase lean liquid flowing out of the lean liquid flash tank 51 through the lean liquid heat exchanger 32, and the temperature rises from 45-60℃ to 65-80℃. Then it exchanges heat with the lean liquid flash heat pump 33, and the temperature rises from 65-80℃ to 100-115℃.

[0057] Another route is rich in solution, at 1400-1600m 3 The flow rate of / h is first treated by the steam condensate heat exchanger 34, where the temperature is raised from 50-65℃ to 70-85℃, and then the regenerated gas heat pump 35 is used for heat exchange, where the temperature is raised from 70-85℃ to 110-125℃.

[0058] The two rich liquids are heat-exchanged separately, and then both are fed into regeneration tower 4 for desorption.

[0059] By using rich liquid diversion and staged heat exchange, the consumption of high-grade heat source steam during rich liquid heat exchange can be greatly reduced without the need for multiple heat exchange processes.

[0060] (4) Lean liquor heat exchange: The lean liquor formed in the regeneration tower is discharged from the bottom of the regeneration tower and fed into the lean liquor flash tank 51. The gas phase formed in the lean liquor flash tank 51 is discharged from the top of the lean liquor flash tank 51 and exchanges heat with the rich liquor through the lean liquor flash heat pump 33, reducing the temperature from 105-110℃ to 45-65℃, and then sent back to the absorption tower 2. The liquid phase formed in the lean liquor flash tank 51 first exchanges heat with the rich liquor through the lean-rich liquor heat exchanger 32, and then is sent to the lean liquor buffer tank 53 through the lean liquor pump 52. In the lean liquor buffer tank 53, part of the lean liquor is cooled by the lean liquor cooler 54, reducing the temperature from 45-65℃ to 35-45℃, and then sent back to the absorption tower 2. The other part of the lean liquor is filtered by the filter 55 and then sent back to the absorption tower 2 to realize the recycling of CO2 absorbent.

[0061] In addition, the reboiler 41 connected to the bottom of the regeneration tower 4 can perform internal circulation of lean liquor; the material heating temperature in the reboiler 41 is 105-110°C to maintain the temperature at the bottom of the regeneration tower 4; the condensate formed in the reboiler 41 exchanges heat with the steam condensate heat exchanger 34, and the condensate after heat exchange is discharged and collected for recycling.

[0062] (5) CO2 separation: In regeneration tower 4, the rich liquid decomposes upon heating, releasing CO2. The CO2, along with a large amount of water vapor and a small amount of decarbonization solvent vapor, is discharged from the top of regeneration tower 4, which is the regeneration gas. The regeneration gas discharged from the top of regeneration tower 4 is first cooled by heat exchange with the rich liquid through regeneration gas heat pump 35, and then fed into CO2 separator 42 for treatment. After separation by CO2 separator 42, the regeneration gas can obtain a flow rate of 1.1×10⁻⁶. 5 -1.2×10 5 m 3CO2-containing gas with a CO2 concentration ≥ 95 vol% per hour is sent to the CO2 recovery and treatment process, while the separated condensate is sent to the solution storage tank.

[0063] <Example>

[0064] Example 1

[0065] 170×10 4 Nm 3 Flue gas with a temperature of 120℃, an absolute pressure of 153kPa, and a CO2 content of 2.86 vol% per hour is washed and dust removed in a water scrubbing tower and cooled to about 44℃.

[0066] The purified flue gas undergoes gas-liquid separation. The separated flue gas is then fed into an induced draft fan for pressurization. After being pressurized to a slightly positive pressure, it is transported along a pipeline to the bottom of the absorption tower. Simultaneously, CO2 absorbent is introduced from the top of the absorption tower, allowing the flue gas at the bottom to come into counter-current contact with the CO2 absorbent at the top, thus achieving CO2 capture and removal. The decarbonized and purified flue gas is then discharged from the top of the absorption tower.

[0067] In this embodiment, the CO2 absorbent, by mass fraction, includes 62.2% triethanolamine, 32.7% N-methyldiethanolamine, 3.75% piperazine, 0.65% diethylene glycolamine, 0.31% NaVO3, 0.14% polyether defoamer (7733# defoamer produced by Hefei Xinwancheng Environmental Protection Technology Co., Ltd.), and 0.25% potassium dichromate.

[0068] The decarbonized flue gas discharged from the top of the absorption tower was sampled and tested, and the CO2 content was found to be 0.27 vol%. The CO2 removal rate was calculated to be 90.6%.

[0069] After flue gas purification, a rich liquid remains at the bottom of the absorption tower after CO2 absorption. This rich liquid is discharged from the bottom of the absorption tower and divided into two streams. One stream of rich liquid flows at a rate of 4778 m³ / s. 3 At a flow rate of / h, the liquid first exchanges heat with the lean liquid flowing out of the lean liquid flash tank through a lean-rich liquid heat exchanger, raising the temperature from 51℃ to 68℃. Then, it exchanges heat again through a lean liquid flash heat pump, raising the temperature from 68℃ to 106℃. Meanwhile, another rich liquid flows at a flow rate of 1560m³ / h. 3 The flow rate is / h. After being processed by a steam condensate heat exchanger, the temperature rises from 51℃ to 72℃. Then, after heat exchange by a regenerated gas heat pump, the temperature rises from 72℃ to 116℃. The two rich liquids are then mixed and fed into the regeneration tower.

[0070] Inside the regeneration tower, the rich liquor decomposes upon heating, releasing CO2. The CO2, along with a large amount of water vapor and a small amount of decarbonization solvent vapor, is discharged from the top of the regeneration tower. The regeneration gas discharged from the top of the regeneration tower is first cooled by heat exchange with the rich liquor via a regeneration gas heat pump, and then introduced into a CO2 separator for gas-liquid separation. After separation, a flow rate of 1.112 × 10⁻⁶ is obtained. 5 m 3 CO2-containing gas with a CO2 concentration of 99.52 vol% is sent to the CO2 recovery and treatment process, while the separated condensate is sent to the solution storage tank.

[0071] The lean liquor formed in the regeneration tower is discharged from the bottom of the regeneration tower and treated in a lean liquor flash tank. The gas phase in the lean liquor flash tank is discharged from the top of the lean liquor flash tank and exchanges heat with the rich liquor through a lean liquor flash heat pump, reducing the temperature from 107°C to 62°C, before being sent back to the absorption tower. The liquid phase in the lean liquor flash tank first exchanges heat with the rich liquor through a lean-rich liquor heat exchanger, then is pumped to the lean liquor buffer tank by a lean liquor pump, and then its temperature is reduced from 62°C to 41°C by a lean liquor cooler. After being treated by a filter, it is sent back to the absorption tower, thus enabling the CO2 absorbent to be recycled.

[0072] In addition, the lean liquor in the regeneration tower is heated by a reboiler connected to the bottom of the regeneration tower, so that the material at the bottom of the tower is heated to 108°C and then circulated back into the regeneration tower to realize the internal circulation of the lean liquor in the regeneration tower; the condensate formed by the reboiler exchanges heat with the steam condensate heat exchanger, and the condensate after heat exchange is discharged and collected.

[0073] The measured drug circulation volume was 6325m³. 3 / h, with a comprehensive energy consumption of approximately 2.52 GJ / tCO2.

[0074] Example 2

[0075] 170×10 4 Nm 3 Flue gas with a temperature of 122℃, an absolute pressure of 153kPa, and a CO2 content of 2.69 vol% per hour is washed and dust removed in a water scrubbing tower and cooled to about 44℃.

[0076] The purified flue gas undergoes gas-liquid separation. The separated flue gas is then fed into an induced draft fan for pressurization. After being pressurized to a slightly positive pressure, it is transported along a pipeline to the bottom of the absorption tower. Simultaneously, CO2 absorbent is introduced from the top of the absorption tower, allowing the flue gas at the bottom to come into counter-current contact with the CO2 absorbent at the top, thus achieving CO2 capture and removal. The decarbonized and purified flue gas is then discharged from the top of the absorption tower.

[0077] In this embodiment, the CO2 absorbent, by mass fraction, includes 62.2% triethanolamine, 32.7% N-methyldiethanolamine, 3.75% piperazine, 0.65% diethylene glycolamine, 0.31% NaVO3, 0.14% polyether defoamer (7733# defoamer produced by Hefei Xinwancheng Environmental Protection Technology Co., Ltd.), and 0.25% potassium dichromate.

[0078] The decarbonized flue gas discharged from the top of the absorption tower was sampled and tested, and the CO2 content was found to be 0.29 vol%. The CO2 removal rate was calculated to be 89.2%.

[0079] After flue gas purification, a rich liquid remains at the bottom of the absorption tower after CO2 absorption. This rich liquid is discharged from the bottom of the absorption tower and divided into two streams. One stream of rich liquid flows at a rate of 4965 m³ / h. 3 The liquid stream, flowing at a rate of 1560 m³ / h, first exchanges heat with the lean liquid from the lean flash tank via a lean-rich liquid heat exchanger, raising its temperature from 54°C to 76°C. It then passes through a lean liquid flash heat pump for further heat exchange, raising its temperature from 76°C to 111°C. Meanwhile, another rich liquid stream flows at a rate of 1560 m³ / h. 3 The flow rate is / h. After being processed by the steam condensate heat exchanger, the temperature is raised from 55℃ to 79℃. Then, after heat exchange by the regeneration gas heat pump, the temperature is raised from 79℃ to 120℃. The two rich liquids are then mixed and fed into the regeneration tower.

[0080] Inside the regeneration tower, the rich liquor decomposes upon heating, releasing CO2. The CO2, along with a large amount of water vapor and a small amount of decarbonization solvent vapor, is discharged from the top of the regeneration tower. The regeneration gas discharged from the top of the regeneration tower is first cooled by heat exchange with the rich liquor via a regeneration gas heat pump, and then introduced into a CO2 separator for gas-liquid separation. After separation, a flow rate of 1.109 × 10⁻⁶ is obtained. 5 m 3 CO2-containing gas with a CO2 concentration of 78.14 vol% per hour is sent to the CO2 recovery and treatment process, while the separated condensate is sent to the solution storage tank.

[0081] The lean liquor formed in the regeneration tower is discharged from the bottom of the regeneration tower and treated in a lean liquor flash tank. The gas phase in the lean liquor flash tank is discharged from the top of the lean liquor flash tank and exchanges heat with the rich liquor through a lean liquor flash heat pump, reducing the temperature from 108℃ to 62℃, before being sent back to the absorption tower. The liquid phase in the lean liquor flash tank first exchanges heat with the rich liquor through a lean-rich liquor heat exchanger, then is pumped to the lean liquor buffer tank by a lean liquor pump, and then its temperature is reduced from 62℃ to 39℃ by a lean liquor cooler. After being treated by a filter, it is sent back to the absorption tower, thus enabling the CO2 absorbent to be recycled.

[0082] In addition, the lean liquor in the regeneration tower is heated by a reboiler connected to the bottom of the regeneration tower, so that the material at the bottom of the tower is heated to 108°C and then circulated back into the regeneration tower to realize the internal circulation of the lean liquor in the regeneration tower; the condensate formed by the reboiler exchanges heat with the steam condensate heat exchanger, and the condensate after heat exchange is discharged and collected.

[0083] The measured drug circulation volume was 6398m³. 3 / h, with a comprehensive energy consumption of approximately 2.64 GJ / tCO2.

[0084] <Comparative Example>

[0085] Comparative Example 1

[0086] The difference between this comparative example and Example 1 is that the CO2 absorbent is replaced with a traditional aqueous solution of alcohol amines in order to compare the absorption effect of the absorbent.

[0087] 170×10 4 Nm 3 Flue gas with a temperature of 120℃, an absolute pressure of 153kPa, and a CO2 content of 2.86 vol% per hour is washed and dust removed in a water scrubbing tower and cooled to about 44℃.

[0088] The purified flue gas undergoes gas-liquid separation. The separated flue gas is then fed into an induced draft fan for pressurization. After being pressurized to a slightly positive pressure, it is transported along the pipeline to the bottom of the absorption tower. At the same time, an aqueous solution of amine is introduced from the top of the absorption tower, so that the flue gas at the bottom of the absorption tower comes into counter-current contact with the aqueous solution of amine at the top. The decarbonized and purified flue gas is discharged from the top of the absorption tower.

[0089] The decarbonized flue gas discharged from the top of the absorption tower was sampled and tested, and the CO2 content was found to be 0.55 vol%. The CO2 removal rate was calculated to be 80.8%, which is 9.8% lower than that in Example 1.

[0090] After flue gas purification, a rich liquid remains at the bottom of the absorption tower after CO2 absorption. This rich liquid is discharged from the bottom of the absorption tower and divided into two streams. One stream of rich liquid flows at a rate of 4778 m³ / s. 3 The liquid stream, flowing at a rate of 1560 m³ / h, first exchanges heat with the lean liquid from the lean flash tank via a lean-rich liquid heat exchanger, raising its temperature from 51°C to 71°C. It then passes through a lean liquid flash heat pump for further heat exchange, raising its temperature from 71°C to 108°C. Meanwhile, another rich liquid stream flows at a rate of 1560 m³ / h. 3 The flow rate is / h. After being processed by a steam condensate heat exchanger, the temperature rises from 53℃ to 75℃. Then, after heat exchange by a regenerated gas heat pump, the temperature rises from 75℃ to 119℃. The two rich liquids are then mixed and fed into the regeneration tower.

[0091] Inside the regeneration tower, the rich liquor decomposes upon heating, releasing CO2. The CO2, along with a large amount of water vapor and a small amount of decarbonization solvent vapor, is discharged from the top of the regeneration tower. The regeneration gas discharged from the top of the regeneration tower is first cooled by heat exchange with the rich liquor via a regeneration gas heat pump, and then introduced into a CO2 separator for gas-liquid separation. After separation, a flow rate of 1.100 × 10⁻⁶ is obtained. 5 m 3 CO2-containing gas with a CO2 concentration of 78.14 vol% per hour is sent to the CO2 recovery and treatment process, while the separated condensate is sent to the solution storage tank.

[0092] The lean liquor formed in the regeneration tower is discharged from the bottom of the regeneration tower and treated in a lean liquor flash tank. The gas phase in the lean liquor flash tank is discharged from the top of the lean liquor flash tank and exchanges heat with the rich liquor through a lean liquor flash heat pump, reducing the temperature from 105℃ to 63℃, before being sent back to the absorption tower. The liquid phase in the lean liquor flash tank first exchanges heat with the rich liquor through a lean-rich liquor heat exchanger, then is pumped to the lean liquor buffer tank by a lean liquor pump, and then its temperature is reduced from 61℃ to 40℃ by a lean liquor cooler. After being treated by a filter, it is sent back to the absorption tower, thus enabling the CO2 absorbent to be recycled.

[0093] In addition, the lean liquor in the regeneration tower is heated by a reboiler connected to the bottom of the regeneration tower, so that the material at the bottom of the tower is heated to 108°C and then circulated back into the regeneration tower to realize the internal circulation of the lean liquor in the regeneration tower; the condensate formed by the reboiler exchanges heat with the steam condensate heat exchanger, and the condensate after heat exchange is discharged and recycled.

[0094] The measured drug circulation volume was 6989m³. 3 / h, with a comprehensive energy consumption of approximately 2.97 GJ / tCO2.

[0095] Comparative Example 2

[0096] The difference between this comparative example and Example 1 is that an aqueous solution of alcoholic amines is used as the CO2 absorbent, and the process of rich liquid diversion multi-stage heat exchange and comprehensive utilization of heat energy is not adopted.

[0097] 170×10 4 Nm 3 Flue gas with a temperature of 120℃, an absolute pressure of 153kPa, and a CO2 content of 2.86 vol% per hour is washed and dust removed in a water scrubbing tower and cooled to about 44℃.

[0098] The purified flue gas undergoes gas-liquid separation. The separated flue gas is then fed into an induced draft fan for pressurization. After being pressurized to a slightly positive pressure, it is transported along the pipeline to the bottom of the absorption tower. At the same time, an aqueous solution of amine is introduced from the top of the absorption tower, so that the flue gas at the bottom of the absorption tower comes into counter-current contact with the aqueous solution of amine at the top. The decarbonized and purified flue gas is discharged from the top of the absorption tower.

[0099] The flue gas discharged from the top of the absorption tower after decarbonization and purification was sampled and tested. The CO2 content was found to be 0.57 vol%. The CO2 removal rate was calculated to be 80.1%. Compared with Example 1, the CO2 removal rate decreased by 10.5%, and the overall energy consumption was measured to be approximately 3.15 GJ / tCO2.

[0100] The rich liquid remaining at the bottom of the absorption tower, after being treated by heating, cooling, and filtration, is returned to the absorption tower as needed for recycling. The reagent circulation rate was measured to be 6972 m³. 3 / h.

[0101] <Experimental Example>

[0102] Samples: Examples 1-2, Comparative Examples 1-2

[0103] Random samples were taken from the flue gas treated in Examples 1-2 and Comparative Example 1 to determine the CO2 removal rate and overall energy consumption. The results are summarized in Table 1 below:

[0104] Table 1 shows the CO2 removal efficiency in the sample flue gas.

[0105] Comparison items <![CDATA[Throughput (Nm 3 / h)]]> <![CDATA[CO2 removal rate (%)]]> <![CDATA[Reagent circulation rate (m 3 / h)]]> <![CDATA[Comprehensive energy consumption (GJ / tCO2)]]> Example 1 <![CDATA[170×10 4 ]]> 90.6 6325 2.44 Example 2 <![CDATA[170×10 4 ]]> 89.2 6398 2.64 Comparative Example 1 <![CDATA[170×10 4 ]]> 80.8 6989 2.97 Comparative Example 2 <![CDATA[170×10 4 ]]> 80.1 6972 3.15

[0106] It can be seen from Table 1 above:

[0107] Using the carbon capture and removal process of Examples 1-2, the CO2 removal rate of flue gas with ultra-low CO2 concentration is as high as 89.2%–90.6%. In contrast, the CO2 removal rate of flue gas with ultra-low CO2 concentration treated by conventional adsorbents and chemical adsorption methods in Comparative Examples 1-2 is only 80.1%–83.8%. In terms of reagent circulation, the CO2 absorbent in Examples 1-2 has a higher carbon removal efficiency than that in Comparative Examples 1-2, thus requiring less reagent and a lower corresponding circulation volume. In terms of overall energy consumption, the process of Examples 1-2 has significantly lower overall energy consumption than the traditional process in Comparative Examples 1-2. In other words, the flue gas carbon capture and removal process provided by this invention can be applied to flue gas with ultra-low CO2 concentration, has a high CO2 removal rate, and significantly reduces overall energy consumption.

[0108] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A low-energy-consumption, ultra-low CO2 concentration flue gas carbon capture and removal system, characterized in that, It includes a water washing tower (1), an absorption tower (2), and a regeneration tower (4) connected sequentially by pipelines; The absorption tower (2) and the regeneration tower (4) are connected in parallel by a first rich liquid heat exchange component and a second rich liquid heat exchange component. Along the direction of material flow from the absorption tower (2) to the regeneration tower (4), the first rich liquid heat exchange component includes a lean and rich liquid heat exchanger (32) and a lean liquid flash steam heat pump (33) connected in sequence, and the second rich liquid heat exchange component includes a steam condensate heat exchanger (34) and a regeneration gas heat pump (35) connected in sequence.

2. The low-energy-consumption ultra-low CO2 concentration flue gas carbon capture and removal system according to claim 1, characterized in that, The outlet of the absorption tower (2) is also connected to a rich liquid pump (31), and the outlet of the rich liquid pump (31) is connected to the lean and rich liquid heat exchanger (32) and the steam condensate heat exchanger (34), respectively.

3. The low-energy-consumption ultra-low CO2 concentration flue gas carbon capture and removal system according to claim 1, characterized in that, The top of the regeneration tower (4) is connected to a CO2 separator (42), and the pipeline between the regeneration tower (4) and the CO2 separator (42) flows through the regeneration gas heat pump (35).

4. The low-energy-consumption ultra-low CO2 concentration flue gas carbon capture and removal system according to any one of claims 1 to 3, characterized in that, The bottom of the regeneration tower (4) is also connected to a first lean liquor circulation assembly, which includes a lean liquor flash tank (51) and a lean liquor buffer tank (53) connected in sequence. The outlet end of the lean liquor buffer tank (53) is connected to a lean liquor cooler (54) and a filter (55), respectively. The lean liquor cooler (54) and the filter (55) are both connected to the feed end of the absorption tower (2).

5. The low-energy-consumption ultra-low CO2 concentration flue gas carbon capture and removal system according to claim 4, characterized in that, The bottom of the regeneration tower (4) is connected to a lean liquid internal circulation component, which includes a reboiler (41). The feed pipe and the discharge pipe of the reboiler (41) are both connected to the bottom of the regeneration tower (4).

6. The low-energy-consumption ultra-low CO2 concentration flue gas carbon capture and removal system according to claim 5, characterized in that, The pipe between the lean liquid flash evaporator (51) and the lean liquid buffer tank (53) is connected to the lean and rich liquid heat exchanger (32).

7. The low-energy-consumption ultra-low CO2 concentration flue gas carbon capture and removal system according to claim 5, characterized in that, The pipeline between the lean liquid flash evaporator (51) and the lean liquid buffer tank (53) is also equipped with a lean liquid pump (52).

8. A low-energy-consumption, ultra-low CO2 concentration flue gas carbon capture and removal process using the system described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1 preprocessing: The flue gas to be treated is washed, dust removed, and cooled. S2 CO2 capture: The pretreated flue gas and CO2 absorbent are introduced into the absorption tower, mixed in contact, and CO2 is captured and absorbed. The captured gas is discharged from the top of the absorption tower, and a rich liquid is formed at the bottom of the absorption tower. S3 Rich Liquid Split Heat Exchange: The rich liquid is divided into two streams. One stream exchanges heat with the liquid phase flowing out of the lean liquid flash tank through a lean-rich liquid heat exchanger, and then exchanges heat through a lean liquid flash heat pump. The other route first passes through a steam-condensate heat exchanger, and then through a regenerated gas heat pump for heat exchange; The two rich solutions undergo heat exchange separately, and then are fed together into the regeneration tower for desorption. S4 lean solution heat exchange: The lean liquor formed in the regeneration tower is discharged from the bottom of the regeneration tower and fed into the lean liquor flash tank for treatment. The gas phase in the lean liquor flash tank exchanges heat with the rich liquor through the lean liquor flash vapor heat pump and is then sent back to the absorption tower. The liquid phase in the lean liquor flash tank first exchanges heat with the rich liquor through the lean-rich liquor heat exchanger, and then is pumped into the lean liquor buffer tank. After cooling and filtration, it is sent back to the absorption tower. S5 CO2 separation: The gas phase in the regeneration tower is discharged from the top, first exchanged heat with the rich liquid through the regeneration gas heat pump, and then passed into the CO2 separator for gas-liquid separation. The separated CO2-containing gas is sent to the CO2 recovery and treatment process, while the separated condensate is sent to the solution storage tank.

9. The low-energy-consumption ultra-low CO2 concentration flue gas carbon capture and removal process according to claim 8, characterized in that, In step S2, the CO2 absorbent includes a composite absorbent, an activator, an antioxidant, an antifoaming agent, and a corrosion inhibitor, wherein the composite absorbent includes triethanolamine and N-methyldiethanolamine.

10. The low-energy-consumption ultra-low CO2 concentration flue gas carbon capture and removal process according to claim 8, characterized in that, In step S3, the flow rate of the rich solution is controlled to be 3600–6000 m³ / h. 3 / h, the flow rate of the other rich solution is 1400-1600 m³ / h. 3 / h.

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