System and method for capturing cement kiln flue gas carbon dioxide based on high-temperature flue gas waste heat regeneration technology

Abstract

The invention discloses a system and a method for capturing cement kiln flue gas carbon dioxide based on a high-temperature flue gas waste heat regeneration technology. The system comprises a carbon dioxide absorption system and a carbon dioxide desorption system, the carbon dioxide absorption system comprises a pretreatment tower, an induced draft fan, an absorption tower, a water washing tower and a rich liquid pump; the carbon dioxide desorption system comprises a rich and lean solution heat exchanger, a lean solution pump, a desorption tower, a regenerated gas cooler, a lean solution cooler and a high-temperature flue gas waste heat recovery reboiler. Compared with the prior art, the system and method for capturing the cement kiln flue gas carbon dioxide based on the high-temperature flue gas waste heat regeneration technology can effectively utilize the cement kiln high-temperature flue gas to replace external heat source water vapor to desorb CO2, can effectively reduce the CO2 capturing cost, realizes the cooling of the cement kiln high-temperature flue gas, and improves the recovery rate of CO2. Good application prospects are realized.

Description

Technical Field

[0001] The present invention relates to the field of CO2 capture technology, and in particular to a system and method for capturing carbon dioxide from cement kiln flue gas based on high-temperature flue gas waste heat regeneration technology. Background Art

[0002] CO2 capture, utilization, and storage (CCUS) technology is an important path to achieving large-scale, low-carbon energy utilization. Post-combustion carbon capture (CCUS) is considered the most promising carbon capture technology for large-scale industrial application due to its wide range of applications and low retrofit costs. Currently, post-combustion carbon capture technology primarily relies on chemical absorption. In an absorption tower, an absorbent chemically reacts with CO2 in flue gas, absorbing the CO2. Subsequently, in a desorption tower, an external heat source, typically high-temperature steam, drives a reverse reaction, desorbing the CO2. Patent ZL20150358538.4 proposes a process for capturing CO2 from flue gas based on wet regeneration technology. This process utilizes functionalized ion exchange resin membranes to achieve low-cost adsorption and separation of high-purity CO2. Patent CN202410999222.2 discloses a system and method for capturing CO2 using waste heat from steam turbine exhaust. This system reduces energy consumption for CO2 capture and reduces the operating load of the power plant's circulating cooling system.

[0003] However, the conventional desorption mechanism, which uses an external heat source, steam, to drive the desorption process, suffers from high capture energy consumption and operating costs, making it unsuitable for large-scale industrial application. Cement kiln flue gas is also hot (250-400°C), and its waste heat is not fully utilized, resulting in a waste of thermal resources. Therefore, the waste heat from the high-temperature flue gas of cement kilns can be used to drive the regeneration of CO2, achieving efficient, energy-saving, and low-cost CO2 capture. Summary of the Invention

[0004] To solve the above technical problems, the present invention designs a system and method for capturing carbon dioxide from cement kiln flue gas based on high-temperature flue gas waste heat regeneration technology, which can not only reduce the regeneration energy consumption and operating costs of the capture system, but also solve the problem of excessively high flue gas temperature in cement kilns.

[0005] The present invention adopts the following technical solutions: A system for capturing carbon dioxide from cement kiln flue gas based on high-temperature flue gas waste heat regeneration technology, comprising a carbon dioxide absorption system and a carbon dioxide desorption system; the carbon dioxide absorption system comprises a pretreatment tower, an induced draft fan, an absorption tower, a water scrubber, and a rich liquid pump; the carbon dioxide desorption system comprises a lean and rich liquid heat exchanger, a lean liquid pump, a desorption tower, a regenerated gas cooler, a lean liquid cooler, and a high-temperature flue gas waste heat recovery reboiler; In the carbon dioxide absorption system, the flue gas outlet of the high-temperature flue gas waste heat recovery reboiler is connected to the induced draft fan through the pretreatment tower, the flue gas outlet of the induced draft fan is connected to the bottom of the absorption tower, the absorbent lean liquid inlet pipe is connected to the upper part of the absorption tower, the decarbonized flue gas after absorbing CO2 is connected to the water scrubber, and the absorbent rich liquid outlet of the bottom of the absorption tower is connected to the lean and rich liquid heat exchanger through the rich liquid pump; In the carbon dioxide desorption system, the rich liquid outlet of the lean-rich liquid heat exchanger is connected to the upper part of the desorption tower, the regenerated gas outlet on the top of the desorption tower is connected to the regenerated gas cooler, the semi-rich liquid outlet of the absorbent in the tower bottom of the desorption tower is connected to the high-temperature flue gas waste heat recovery reboiler, the absorbent lean liquid at the bottom of the high-temperature flue gas waste heat recovery reboiler is connected to the tower bottom of the desorption tower through the secondary steam outlet, the absorbent lean liquid outlet of the tower bottom of the desorption tower is connected to the lean-rich liquid heat exchanger through a lean liquid pump, the semi-cold lean liquid outlet of the lean-rich liquid heat exchanger is connected to the lean liquid cooler, the cold lean liquid outlet of the lean liquid cooler is connected to the absorption tower, the hot flue gas inlet of the cement kiln is connected to the high-temperature flue gas waste heat recovery reboiler, and the cold flue gas outlet of the cement kiln is connected to the flue gas inlet of the pretreatment tower.

[0006] Preferably, the temperature of the high-temperature flue gas in the high-temperature flue gas waste heat recovery reboiler is 250-400°C.

[0007] Preferably, the high-temperature flue gas waste heat recovery reboiler is a shell and tube heat exchanger or a plate heat exchanger.

[0008] Preferably, the cold flue gas from the cement kiln after heat exchange and cooling in the high-temperature flue gas waste heat recovery reboiler is further cooled by heat exchange with cooling water in the pretreatment tower.

[0009] Based on the above system, a method for capturing carbon dioxide from cement kiln flue gas based on high-temperature flue gas waste heat regeneration technology is provided, and the method steps are as follows: S1. The high-temperature flue gas from the cement kiln is cooled by heat exchange in the high-temperature flue gas waste heat recovery reboiler to become cold flue gas from the cement kiln. The cold flue gas is further cooled by heat exchange with the cooling water in the pretreatment tower and then enters the absorption tower through the induced draft fan. The decarbonized flue gas with CO2 removed is discharged through the water scrubber. S2. The absorbent rich liquid generated after the absorbent lean liquid passes through the absorption unit in the absorption tower flows through the rich liquid pump to the lean and rich liquid heat exchanger to be heated into absorbent hot rich liquid and enters the desorption tower. The desorbed CO2 is cooled and cooled by the regeneration gas cooler to become product gas. The absorbent semi-lean liquid is recovered by the high-temperature flue gas waste heat reboiler to generate secondary steam and absorbent lean liquid mixture and return to the desorption tower. The absorbent hot lean liquid flows out from the bottom of the desorption tower, flows through the lean liquid pump to the lean and rich liquid heat exchanger and the lean liquid cooler for cooling, and then returns to the absorption tower.

[0010] The beneficial effects of the present invention are: compared with the existing technology, the system and method for capturing carbon dioxide from cement kiln flue gas based on high-temperature flue gas waste heat regeneration technology provided by the present invention can effectively utilize the high-temperature flue gas from the cement kiln instead of external heat source water vapor to desorb CO2, which can effectively reduce the cost of CO2 capture and achieve cooling of the high-temperature flue gas from the cement kiln, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a structural schematic diagram of the present invention; Among them, 1. Cement kiln high-temperature flue gas, 2. Cement kiln cold flue gas, 3. Cooling water, 4. Absorbent lean solution, 5. Decarbonized flue gas, 6. Absorbent rich solution, 7. Absorbent semi-lean solution, 8. Absorbent hot lean solution, 9. Product gas; 1001. Pretreatment tower, 1002. Induced draft fan, 1003. Absorption tower, 1004. Water washing tower, 1005. Rich liquid pump; 1006. Lean and rich liquid heat exchanger, 1007. Desorption tower, 1008. Regeneration gas cooler, 1009. High-temperature flue gas waste heat recovery reboiler, 1010. Lean liquid pump, 1011. Lean liquid cooler. DETAILED DESCRIPTION

[0012] The technical solution of the present invention is further described in detail below through specific embodiments and in conjunction with the accompanying drawings: Example: As shown in the attached Figure 1 As shown, a system for capturing carbon dioxide from cement kiln flue gas based on high-temperature flue gas waste heat regeneration technology includes a carbon dioxide absorption system and a carbon dioxide desorption system; the carbon dioxide absorption system includes a pretreatment tower 1001, an induced draft fan 1002, an absorption tower 1003, a water scrubber 1004, and a rich liquid pump 1005; the carbon dioxide desorption system includes a lean and rich liquid heat exchanger 1006, a lean liquid pump 1010, a desorption tower 1007, a regenerated gas cooler 1008, a lean liquid cooler 1011, and a high-temperature flue gas waste heat recovery reboiler 1009; In the carbon dioxide absorption system, the flue gas outlet of the high-temperature flue gas waste heat recovery reboiler is connected to the induced draft fan through the pretreatment tower, the flue gas outlet of the induced draft fan is connected to the bottom of the absorption tower, the absorbent lean liquid inlet pipe is connected to the upper part of the absorption tower, the decarbonized flue gas after absorbing CO2 is connected to the water scrubber, and the absorbent rich liquid outlet of the bottom of the absorption tower is connected to the lean and rich liquid heat exchanger through the rich liquid pump; In the carbon dioxide desorption system, the rich liquid outlet of the lean-rich liquid heat exchanger is connected to the upper part of the desorption tower, the regenerated gas outlet on the top of the desorption tower is connected to the regenerated gas cooler, the semi-rich liquid outlet of the absorbent in the tower bottom of the desorption tower is connected to the high-temperature flue gas waste heat recovery reboiler, the absorbent lean liquid at the bottom of the high-temperature flue gas waste heat recovery reboiler is connected to the tower bottom of the desorption tower through the secondary steam outlet, the absorbent lean liquid outlet of the tower bottom of the desorption tower is connected to the lean-rich liquid heat exchanger through a lean liquid pump, the semi-cold lean liquid outlet of the lean-rich liquid heat exchanger is connected to the lean liquid cooler, the cold lean liquid outlet of the lean liquid cooler is connected to the absorption tower, the hot flue gas inlet of the cement kiln is connected to the high-temperature flue gas waste heat recovery reboiler, and the cold flue gas outlet of the cement kiln is connected to the flue gas inlet of the pretreatment tower.

[0013] The high temperature flue gas temperature in the high temperature flue gas waste heat recovery reboiler is 250-400℃. The high temperature flue gas waste heat recovery reboiler is a type of shell and tube heat exchanger or plate heat exchanger.

[0014] The cold flue gas from the cement kiln after heat exchange and cooling in the high-temperature flue gas waste heat recovery reboiler is further cooled by heat exchange with the cooling water in the pretreatment tower.

[0015] The method steps for using the system for capturing carbon dioxide from cement kiln flue gas based on high-temperature flue gas waste heat regeneration technology are as follows: S1, cement kiln high-temperature flue gas 1 is cooled by heat exchange in a high-temperature flue gas waste heat recovery reboiler to become cement kiln cold flue gas 2. The cement kiln cold flue gas is further cooled by heat exchange with cooling water 3 in a pretreatment tower and then enters an absorption tower through an induced draft fan. The decarbonized flue gas 5 with CO2 removed is discharged after passing through a water scrubber. S2, the absorbent lean liquid 4 generates absorbent rich liquid 6 after passing through the absorption unit in the absorption tower, and flows through the rich liquid pump to the lean and rich liquid heat exchanger to be heated into absorbent hot rich liquid and enter the desorption tower. The desorbed CO2 is cooled and cooled by the regeneration gas cooler to become product gas 9. The absorbent semi-lean liquid 7 is recovered through the high-temperature flue gas waste heat reboiler to generate secondary steam and absorbent lean liquid mixture and return to the desorption tower. The absorbent hot lean liquid 8 flows out of the bottom of the desorption tower, flows through the lean liquid pump to the lean and rich liquid heat exchanger and the lean liquid cooler for cooling, and then returns to the absorption tower.

[0016] The following example is a 20,000-ton system for capturing carbon dioxide from cement kiln flue gas based on high-temperature flue gas waste heat regeneration technology. The system includes the following steps: The cement kiln's high-temperature flue gas flow rate is 21.3 t / h at a temperature of 400°C, while the semi-lean absorbent solution flow rate is 68.4 t / h at a temperature of 100.61°C. After heat exchange in the high-temperature flue gas waste heat recovery reboiler, the cold flue gas is cooled to 105°C, and the temperature of the absorbent lean solution and secondary steam mixture is 107.65°C. The high-temperature flue gas waste heat recovery reboiler has a thermal power of 1.9 MW. The cold flue gas flow rate entering the pretreatment tower is 17 t / h at a temperature of 105°C, while the cooling water flow rate is 35.1 t / h at a temperature of 33°C. The flue gas temperature at the pretreatment tower outlet is 35°C. The lean absorbent solution flow rate is 65.4 t / h at a temperature of 40°C, and the rich absorbent solution temperature at the absorber kettle outlet is 40°C. The absorbent loading is 0.500 mol CO2 / mol amine. The absorbent rich liquid passes through the lean-rich liquid heat exchanger and is heated to 88.9°C. The hot absorbent rich liquid is then fed to the desorption tower for desorption, flowing from top to bottom to the desorption unit bottom. At this point, the lean absorbent liquid temperature is 94.4°C, and the absorbent load is 0.235 mol CO2 / mol amine. The hot lean absorbent liquid passes through the lean-rich liquid heat exchanger and is cooled to 49.2°C. It then passes through the lean liquid cooler and is further cooled to 40°C before returning to the absorber. The desorbed CO2 regeneration gas has a flow rate of 2.7 t / h and a temperature of 66.9°C. After passing through the regeneration gas cooler, the product gas flow rate is 2.6 t / h and a temperature of 35°C. The condensate flow rate is 0.16 t / h.

[0017] It can be seen that compared with the existing technology, the system and method for capturing carbon dioxide from cement kiln flue gas based on high-temperature flue gas waste heat regeneration technology provided by the present invention can effectively utilize the high-temperature flue gas from the cement kiln to replace the external heat source water vapor to desorb CO2, which can effectively reduce the CO2 capture cost and achieve cooling of the high-temperature flue gas from the cement kiln, and has good application prospects.

[0018] The embodiment described above is only a preferred solution of the present invention and does not limit the present invention in any form. Other variations and modifications are possible without exceeding the technical solution described in the claims.

Claims

1. A system for capturing carbon dioxide from cement kiln flue gas based on high-temperature flue gas waste heat regeneration technology, characterized by: It includes a carbon dioxide absorption system and a carbon dioxide desorption system; the carbon dioxide absorption system includes a pretreatment tower, an induced draft fan, an absorption tower, a water scrubber, and a rich liquid pump; the carbon dioxide desorption system includes a lean and rich liquid heat exchanger, a lean liquid pump, a desorption tower, a regenerated gas cooler, a lean liquid cooler, and a high-temperature flue gas waste heat recovery reboiler; In the carbon dioxide absorption system, the flue gas outlet of the high-temperature flue gas waste heat recovery reboiler is connected to the induced draft fan through the pretreatment tower, the flue gas outlet of the induced draft fan is connected to the bottom of the absorption tower, the absorbent lean liquid inlet pipe is connected to the upper part of the absorption tower, the decarbonized flue gas after absorbing CO2 is connected to the water scrubber, and the absorbent rich liquid outlet of the bottom of the absorption tower is connected to the lean and rich liquid heat exchanger through the rich liquid pump; In the carbon dioxide desorption system, the rich liquid outlet of the lean-rich liquid heat exchanger is connected to the upper part of the desorption tower, the regenerated gas outlet on the top of the desorption tower is connected to the regenerated gas cooler, the semi-rich liquid outlet of the absorbent in the tower bottom of the desorption tower is connected to the high-temperature flue gas waste heat recovery reboiler, the absorbent lean liquid at the bottom of the high-temperature flue gas waste heat recovery reboiler is connected to the tower bottom of the desorption tower through the secondary steam outlet, the absorbent lean liquid outlet of the tower bottom of the desorption tower is connected to the lean-rich liquid heat exchanger through a lean liquid pump, the semi-cold lean liquid outlet of the lean-rich liquid heat exchanger is connected to the lean liquid cooler, the cold lean liquid outlet of the lean liquid cooler is connected to the absorption tower, the hot flue gas inlet of the cement kiln is connected to the high-temperature flue gas waste heat recovery reboiler, and the cold flue gas outlet of the cement kiln is connected to the flue gas inlet of the pretreatment tower.

2. The system for capturing carbon dioxide from cement kiln flue gas based on high-temperature flue gas waste heat regeneration technology according to claim 1 is characterized in that: The temperature of the high-temperature flue gas in the high-temperature flue gas waste heat recovery reboiler is 250-400°C.

3. The system for capturing carbon dioxide from cement kiln flue gas based on high-temperature flue gas waste heat regeneration technology according to claim 1 is characterized in that: The high-temperature flue gas waste heat recovery reboiler is one of a shell and tube heat exchanger and a plate heat exchanger.

4. The system for capturing carbon dioxide from cement kiln flue gas based on high-temperature flue gas waste heat regeneration technology according to claim 1 is characterized in that: The cold flue gas from the cement kiln cooled by heat exchange in the high-temperature flue gas waste heat recovery reboiler is further cooled by heat exchange with cooling water in the pretreatment tower.

5. A method for capturing carbon dioxide from cement kiln flue gas based on high-temperature flue gas waste heat regeneration technology, using the system for capturing carbon dioxide from cement kiln flue gas based on high-temperature flue gas waste heat regeneration technology as described in any one of claims 1 to 4, characterized in that: The method steps are: S1. The high-temperature flue gas from the cement kiln is cooled by heat exchange in the high-temperature flue gas waste heat recovery reboiler to become cold flue gas from the cement kiln. The cold flue gas is further cooled by heat exchange with the cooling water in the pretreatment tower and then enters the absorption tower through the induced draft fan. The decarbonized flue gas with CO2 removed is discharged through the water scrubber. S2. The absorbent rich liquid generated after the absorbent lean liquid passes through the absorption unit in the absorption tower flows through the rich liquid pump to the lean and rich liquid heat exchanger to be heated into absorbent hot rich liquid and enters the desorption tower. The desorbed CO2 is cooled and cooled by the regeneration gas cooler to become product gas. The absorbent semi-lean liquid is recovered by the high-temperature flue gas waste heat reboiler to generate secondary steam and absorbent lean liquid mixture and return to the desorption tower. The absorbent hot lean liquid flows out from the bottom of the desorption tower, flows through the lean liquid pump to the lean and rich liquid heat exchanger and the lean liquid cooler for cooling, and then returns to the absorption tower.

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