A carbon dioxide capture system

Abstract

The application discloses a carbon dioxide capturing system and relates to the technical field of carbon dioxide capturing. The application combines a heat exchange device with a heat pump, utilizes the characteristics of water vaporization and latent heat absorption, fully utilizes the reaction heat of CO2 absorption, realizes the heat grade promotion of water vapor generated by the heat exchange device through the heat pump, further releases a large amount of latent heat, and then generates high-temperature steam by using the latent heat, so that energy is provided for the carbon dioxide desorption process, the steam latent heat is reused, the reaction heat of the carbon dioxide absorption stage can be used for the heat absorption process of the desorption stage, the problem of heat consumption caused by the large and repeated temperature rising and falling process between the absorption and desorption devices in the traditional carbon dioxide capturing process is solved, the energy consumption of the absorbent regeneration process and the carbon dioxide capturing process is obviously reduced, the CO2 absorption efficiency is improved, and large-scale industrial popularization and application can be facilitated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon dioxide capture, in particular to a carbon dioxide capture system. BACKGROUND

[0002] Carbon capture, utilization and storage (CCUS) technology refers to capturing and separating CO2 from relevant emission sources, transporting to factories for utilization or long-term storage in places such as oceans and oil and gas fields, so as to reduce greenhouse gas emissions. This technology is considered to be the most promising carbon emission reduction technology. CO2 capture technology is the key link of CCUS technology. At present, CO2 capture processes can be divided into the following three categories: pre-combustion capture, oxygen-enriched combustion capture (in-combustion capture) and post-combustion capture. Most CO2 capture is by post-combustion capture technology. The mainstream technologies for post-combustion CO2 capture of fossil fuels include chemical absorption method, physical absorption method, adsorption separation method and membrane separation method, etc. Among them, the chemical absorption method is the most widely used due to its fast absorption speed, large absorption capacity, good market prospects and other characteristics.

[0003] The principle of the chemical absorption method is that the solvent reacts with CO2 to absorb it at low temperature, and when heated, the saturated absorbent undergoes an inverse reaction to desorb CO2. As shown in the traditional chemical absorption process shown in Figure 1 , wherein the flue gas with a certain CO2 concentration is pretreated (including dust removal, desulfurization, denitrification, etc.) and then enters the absorption tower to contact with the absorbent (i.e. lean liquid) countercurrently. Through mass transfer, diffusion and reaction processes, CO2 reacts with the absorbent to form stable or metastable compounds that can be dissolved in water. The absorbent (i.e. rich liquid) that has absorbed CO2 flows into the regeneration tower after being heated by the heat exchanger and exchanges heat with high-temperature steam again. The stable or metastable compounds decompose and release CO2 when heated, and the CO2 desorbed from the regeneration tower is subjected to subsequent cooling, drying and purification processes to become a CO2 product with high purity. At the same time, the absorbent (i.e. lean liquid) that desorbs CO2 is cooled by the heat exchanger and then returned to the absorption tower to recycle CO2 absorption.

[0004] The chemical absorption methods currently studied and applied more are activated hot potassium base method and polyol amine method, such as a method for capturing carbon dioxide in flue tail gas by using potassium carbonate solution disclosed in Chinese patent application No. 201810687897.8, and a method for capturing carbon dioxide by using potassium hydroxide and potassium carbonate disclosed in Chinese patent application No. 201810688782.4. The above methods have the advantages of fast absorption speed, high purification degree, high purity of regenerated gas and the like, but have the disadvantages of low absorbent concentration, large amount of solvent evaporation (molar ratio of water vapor to CO2 in hot potassium base method is 1.8-2.2), easy evaporation and degradation of organic solvent, high energy consumption for regeneration (generally greater than 2.4 GJ / t CO2), especially high operation cost and regeneration energy consumption, which hinders its large-scale industrial popularization and application. SUMMARY

[0005] To solve the above problems existing in the prior art, the present application provides a carbon dioxide capture system with high efficiency and low energy consumption.

[0006] To achieve the above object, the present application provides the following solutions.

[0007] A carbon dioxide capture system, comprising: a carbon dioxide absorption device, a solid-liquid separation device, a carbon dioxide desorption device, a first heat exchange device, a second heat exchange device and a heat pump.

[0008] The top end outlet of the carbon dioxide absorption device is connected with the first inlet of the first heat exchange device through a gas pipeline; the side end outlet of the carbon dioxide absorption device is connected with the second inlet of the first heat exchange device through a slurry pipeline; the first side end inlet of the carbon dioxide absorption device is connected with the first outlet of the first heat exchange device through a slurry pipeline; and the bottom end of the carbon dioxide absorption device is provided with a gas inlet.

[0009] The second outlet of the first heat exchange device is connected with the first inlet of the heat pump through a steam pipeline; the first outlet of the heat pump is connected with the third inlet of the first heat exchange device and the first inlet of the second heat exchange device through a liquid pipeline respectively; the second outlet of the heat pump is connected with the first side end inlet of the carbon dioxide desorption device through a steam pipeline; the top end outlet of the carbon dioxide desorption device is connected with the second inlet of the second heat exchange device through a gas pipeline; the first outlet of the second heat exchange device is connected with the second inlet of the heat pump through a steam pipeline; the second outlet of the second heat exchange device is connected with the first side end inlet of the carbon dioxide absorption device through a liquid pipeline; the bottom end outlet of the carbon dioxide absorption device is connected with the first inlet of the solid-liquid separation device through a slurry pipeline; the first outlet of the solid-liquid separation device is connected with the second side end inlet of the carbon dioxide desorption device through a pipeline; the bottom end outlet of the carbon dioxide desorption device and the second outlet of the solid-liquid separation device are both connected with the second side end inlet of the carbon dioxide absorption device through a slurry pipeline.

[0010] Optionally, the carbon dioxide absorption device is at least a primary absorption tower.

[0011] The primary absorption tower is filled with a carbon dioxide absorbent.

[0012] Optionally, the carbon dioxide absorbent is a compound solution capable of realizing a reaction crystallization phase change.

[0013] Optionally, the compound solution includes a potassium carbonate solution and / or a sodium carbonate solution.

[0014] Optionally, the carbon dioxide absorption device is a reaction-separation integrated device.

[0015] Optionally, the reaction-separation integrated device includes a micro-bubble gas distributor, a preliminary separation device and an absorption tower.

[0016] The micro-bubble gas distributor is arranged at the bottom of the absorption tower, the gas inlet is arranged on the absorption tower, and gas enters the absorption tower from the gas inlet and is dispersed into bubbles smaller than a preset value through the micro-bubble gas distributor.

[0017] The absorption tower comprises a main pipeline, a first pipeline and a second pipeline; the main pipeline is filled with a carbon dioxide absorbent; the first pipeline and the second pipeline are in communication with the main pipeline and are integrally arranged; after the bubbles react with the carbon dioxide absorbent in the main pipeline, the bubbles enter the preliminary separation device through the second pipeline; after preliminary solid-liquid separation, the preliminary separation device returns small-particle slurry to the main pipeline, and large-particle slurry enters the solid-liquid separation device through a liquid pipeline; the concentration of the small-particle slurry is less than that of the large-particle slurry, and the size of the slurry particles is determined based on a set particle value.

[0018] Optionally, the first heat exchange device is provided with an unreacted gas outlet, and the second heat exchange device is provided with a carbon dioxide gas outlet.

[0019] Optionally, the first heat exchange device and the second heat exchange device are both cooling heat exchange evaporators.

[0020] According to the specific embodiments of the present application, the following technical effects are disclosed:

[0021] The carbon dioxide capture system provided by the present application combines the heat exchange device (i.e. the first heat exchange device and the second heat exchange device) with the heat pump, utilizes the characteristics that a large amount of latent heat is absorbed and a large amount of latent heat is released during liquefaction, fully utilizes the reaction heat absorbed, and raises the heat grade of the water vapor generated by the heat exchange device through the heat pump (the cycle performance coefficient COP is generally 4-10), thereby providing energy for the carbon dioxide desorption process, realizing the reuse of steam latent heat, not only using all the reaction heat of the carbon dioxide absorption stage for the endothermic process of the desorption stage, but also solving the problem of heat consumption caused by the large and repeated temperature rising and falling process between the absorption and desorption devices in the traditional carbon dioxide chemical capture process, significantly reducing the energy consumption of the absorbent regeneration process and the carbon dioxide capture process, improving the efficiency, and further solving the problems of high energy consumption and inability to be applied in large-scale industrial promotion in the prior art. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0023] Figure 1 It is a schematic diagram of the traditional chemical absorption process;

[0024] Figure 2This is a schematic diagram of the carbon dioxide capture system provided in Embodiment 1 of the present invention;

[0025] Figure 3 This is a schematic diagram of the carbon dioxide capture system provided in Embodiment 2 of the present invention;

[0026] Figure 4 This is a schematic diagram of the carbon dioxide capture system provided in Embodiment 3 of the present invention.

[0027] Symbol explanation:

[0028] 1-Carbon dioxide absorption device, 2-Solid-liquid separation device, 3-Carbon dioxide desorption device, 4-First heat exchange device, 5-Second heat exchange device, 6-Heat pump, 7-Gas inlet, 8-Unreacted gas outlet, 9-Carbon dioxide gas outlet, 10-Microbubble gas distributor, 11-Preliminary separation device, 12-Absorption tower, 13-First pipeline, 14-Second pipeline. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] The purpose of this invention is to provide a carbon dioxide capture system with high efficiency and low energy consumption, so as to solve the problems of high energy consumption and inability to be widely used in industrial applications in the prior art.

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Example 1

[0033] like Figure 2 As shown, the carbon dioxide capture system provided in this embodiment includes: a carbon dioxide absorption device 1, a solid-liquid separation device 2, a carbon dioxide desorption device 3, a first heat exchange device 4, a second heat exchange device 5, and a heat pump 6.

[0034] The top outlet of the carbon dioxide absorption device 1 is connected to the first inlet of the first heat exchanger 4 via a gas pipeline. The side outlet of the carbon dioxide absorption device 1 is connected to the second inlet of the first heat exchanger 4 via a slurry pipeline. The first side inlet of the carbon dioxide absorption device 1 is connected to the first outlet of the first heat exchanger 4 via a slurry pipeline. A gas inlet 7 is provided at the bottom of the carbon dioxide absorption device 1.

[0035] The second outlet of the first heat exchange device 4 is connected with the first inlet of the heat pump 6 through a steam pipeline. The first outlet of the heat pump 6 is connected with the third inlet of the first heat exchange device 4 and the first inlet of the second heat exchange device 5 respectively through a liquid pipeline. The second outlet of the heat pump 6 is connected with the first side end inlet of the carbon dioxide desorption device 3 through a steam pipeline. The top end outlet of the carbon dioxide desorption device 3 is connected with the second inlet of the second heat exchange device 5 through a gas pipeline. The first outlet of the second heat exchange device 5 is connected with the second inlet of the heat pump 6 through a steam pipeline. The second outlet of the second heat exchange device 5 is connected with the first side end inlet of the carbon dioxide absorption device 1 through a liquid pipeline. The bottom end outlet of the carbon dioxide absorption device 1 is connected with the first inlet of the solid-liquid separation device 2 through a slurry pipeline. The first outlet of the solid-liquid separation device 2 is connected with the second side end inlet of the carbon dioxide desorption device 3 through a pipeline. The bottom end outlet of the carbon dioxide desorption device 3 and the second outlet of the solid-liquid separation device 2 are both connected with the second side end inlet of the carbon dioxide absorption device 1 through a slurry pipeline.

[0036] In this embodiment, the carbon dioxide absorption device 1 is a primary absorption tower. The primary absorption tower is filled with a carbon dioxide absorbent. The carbon dioxide absorbent is a solution of a compound capable of realizing a reaction crystallization phase change, such as a potassium carbonate solution and / or a sodium carbonate solution.

[0037] Further, the first heat exchange device 4 is provided with an unreacted gas outlet 8, and the second heat exchange device 5 is provided with a carbon dioxide gas outlet 9.

[0038] In order to further improve the utilization effect of the latent heat characteristics of water vapor, the first heat exchange device 4 and the second heat exchange device 5 used in this embodiment are preferably cooling heat exchange evaporators.

[0039] Based on the structure of the carbon dioxide capture system provided in the above embodiment, the implementation principle is as follows:

[0040] The treated gas enters the carbon dioxide absorption device 1 from the gas inlet 7, and the CO2 in the treated gas reacts with the absorbent filled in the carbon dioxide absorption device 1 to generate a solid absorption product. The unreacted gas and water vapor enter the first heat exchange device 4 through a gas pipeline, wherein the water vapor becomes liquid water through phase change and returns to the carbon dioxide absorption device 1, and the unreacted gas is discharged through the unreacted gas outlet 8. The slurry in the carbon dioxide absorption device 1 enters the first heat exchange device 4 through a slurry pipeline, and the slurry is heat exchanged in the first heat exchange device 4 and then returns to the carbon dioxide absorption device 1 through the slurry pipeline. The water vapor generated by the first heat exchange device 4 enters the heat pump 6 through a steam pipeline. The liquid water generated by the heat pump 6 finally returns to the first heat exchange device 4 and the second heat exchange device 5 through a liquid pipeline. The water vapor generated by the heat pump 6 enters the carbon dioxide desorption device 3 through a steam pipeline.

[0041] The solid absorption product in the carbon dioxide absorption device 1 enters the solid-liquid separation device 2 through the slurry pipeline, the separated clear liquid returns to the carbon dioxide absorption device 1 through the clear liquid return pipeline, and the separated solid enters the carbon dioxide desorption device 3 through the pipeline.

[0042] After the solid absorption product is desorbed in the carbon dioxide desorption device 3, the generated CO2 and water vapor enter the second heat exchange device 5 through the gas pipeline, the water vapor is converted into liquid water through phase change and returns to the carbon dioxide absorption device 1, the CO2 is collected through the CO2 gas outlet, the water vapor generated by the second heat exchange device 5 enters the heat pump 6 through the steam pipeline, the liquid water generated by the heat pump 6 finally returns to the first heat exchange device 4 and the second heat exchange device 5 through the liquid pipeline, and the high-temperature steam generated by the heat pump 6 enters the carbon dioxide desorption device 3 through the steam pipeline.

[0043] After the solid absorption product is desorbed in the carbon dioxide desorption device 3, the generated absorption agent returns to the carbon dioxide absorption device 1 through the pipeline.

[0044] For example, when a potassium carbonate solution with a mass concentration of 50% is used as the absorption agent, flue gas enters the carbon dioxide absorption device 1 from the gas inlet 7, the reaction temperature in the carbon dioxide absorption device 1 is 105°C, the CO2 in the flue gas reacts with the potassium carbonate solution to generate potassium bicarbonate solid, 105°C water vapor and unreacted gas enter the first heat exchange device 4 through the gas pipeline, there is boiling water at 100°C in the first heat exchange device 4, the 105°C water vapor is condensed into liquid water to separate from the unreacted gas and returns to the carbon dioxide absorption device 1 through the liquid pipeline for recycling, and the unreacted gas is discharged from the unreacted gas outlet 8. The 105°C slurry enters the first heat exchange device 4 through the slurry pipeline, the 105°C slurry is returned to the carbon dioxide absorption device 1 through the slurry pipeline after heat exchange with the 100°C boiling water, the boiling water in the first heat exchange device 4 is continuously vaporized into water vapor after absorbing heat and enters the heat pump 6, the water vapor is converted into liquid water in the heat pump 6 while releasing a large amount of latent heat, generating 130°C steam which enters the carbon dioxide desorption device 3, and the low-temperature liquid water in the heat pump 6 returns to the first heat exchange device 4 and the second heat exchange device 5 through the liquid pipeline for recycling.

[0045] The potassium bicarbonate slurry in the carbon dioxide absorption device 1 enters the solid-liquid separation device 2 through the slurry pipeline, the separated clear liquid returns to the carbon dioxide absorption device 1 through the clear liquid return pipeline for recycling, and the separated potassium bicarbonate solid enters the carbon dioxide desorption device 3 through the pipeline.

[0046] The reaction temperature in the carbon dioxide desorption device 3 is 115°C, the potassium bicarbonate solid is decomposed by the heat energy provided by the heat pump 6 to generate potassium carbonate, water vapor and CO2, wherein the water vapor and CO2 enter the second heat exchange device 5 through the gas pipeline, the second heat exchange device 5 has boiling water at 100°C under normal pressure, the decomposed water vapor is condensed into liquid water to separate from the CO2 gas and return to the carbon dioxide absorption device 1 for recycling, the CO2 gas is discharged from the CO2 gas outlet, and the boiling water is continuously vaporized into water vapor into the heat pump 6, the water vapor in the heat pump 6 is changed into liquid water by phase change while releasing a large amount of latent heat to generate 130°C steam to continue to heat the carbon dioxide desorption device 3, and the low-temperature liquid water in the heat pump 6 returns to the first heat exchange device 4 and the second heat exchange device 5 through the liquid pipeline for recycling.

[0047] The potassium carbonate solid generated in the carbon dioxide desorption device 3 is returned to the carbon dioxide absorption device 1 through the pipeline as an absorbent for recycling.

[0048] Example 2

[0049] This example uses the carbon dioxide capture system as shown in Figure 3 The difference between this example and the carbon dioxide capture system used in Example 1 is that the carbon dioxide absorption device 1 in this example is a two-stage absorption tower in series.

[0050] This example uses a potassium carbonate solution with a mass concentration of 50% as an absorbent, flue gas enters the first-stage absorption tower of the carbon dioxide absorption device 1 from the gas inlet 7, the reaction temperature in the carbon dioxide absorption device 1 is 105°C, CO2 in the flue gas reacts with the potassium carbonate solution to generate potassium bicarbonate solid, 105°C water vapor and unreacted gas enter the second-stage absorption tower of the carbon dioxide absorption device 1 through the gas pipeline, the remaining CO2 in the unreacted gas continues to react with the potassium carbonate solution to generate potassium bicarbonate solid, the unreacted gas and water vapor in the second-stage absorption tower enter the first heat exchange device 4 through the gas pipeline, the slurry at 105°C enters the first heat exchange device 4 through the slurry pipeline, the first heat exchange device 4 has boiling water at 100°C under normal pressure, the 105°C water vapor is condensed into liquid water to separate from the unreacted gas and return to the carbon dioxide absorption device 1 through the liquid pipeline, the unreacted gas is discharged from the unreacted gas outlet 8, the slurry at 105°C is returned to the carbon dioxide absorption device 1 through the slurry pipeline after heat exchange with the boiling water in the first heat exchange device 4, the boiling water is continuously vaporized into water vapor into the heat pump 6 after absorbing heat, the water vapor in the heat pump 6 is changed into liquid water by phase change while releasing a large amount of latent heat to generate 130°C steam into the carbon dioxide desorption device 3, and the low-temperature liquid water in the heat pump 6 returns to the first heat exchange device 4 and the second heat exchange device 5 through the liquid pipeline for recycling.

[0051] The slurry in the first and second absorption towers of the carbon dioxide absorption device 1 enters the solid-liquid separation device 2 through a slurry pipeline, the clear liquid after separation returns to the two absorption towers of the carbon dioxide absorption device 1 through a clear liquid return pipeline for recycling, and the potassium bicarbonate solid after separation enters the carbon dioxide desorption device 3 through a pipeline.

[0052] The reaction temperature in the carbon dioxide desorption device 3 is 115°C, the potassium bicarbonate solid is decomposed by the heat energy provided by the heat pump 6 to generate potassium carbonate, water vapor and CO2, wherein the water vapor and CO2 enter the second heat exchange device 5 through a gas pipeline, the second heat exchange device 5 has boiling water at 100°C under normal pressure, the generated water vapor is condensed into liquid water to separate from the CO2 gas and return to the carbon dioxide absorption device 1 for recycling, the CO2 gas is discharged from the CO2 gas outlet 8, and the boiling water is continuously vaporized into water vapor into the heat pump 6, the water vapor is phase-changed into liquid water in the heat pump 6 while releasing a large amount of latent heat, generating 130°C steam to continue to provide heat for the carbon dioxide desorption device 3, and the low-temperature liquid water in the heat pump 6 returns to the first heat exchange device 4 and the second heat exchange device 5 through a liquid pipeline for recycling.

[0053] The potassium carbonate solid generated in the carbon dioxide desorption device 3 is returned to the two absorption towers of the carbon dioxide absorption device 1 for recycling as an absorbent.

[0054] Example 3

[0055] This example uses the carbon dioxide capture system as shown in Figure 4 to capture CO2 in flue gas, the difference between this example and example 1 is that the carbon dioxide absorption device 1 in this example is a reaction-separation integrated device, which can realize the concentration and particle size adjustment of large particle crystalline products after absorbing CO2. In addition, the carbon dioxide absorption device 1 in this example uses micro-bubble technology, which can generate micro-bubbles below 500μm. Finally, in order to further increase the CO2 absorption rate, the absorbent uses a high-concentration potassium carbonate and sodium carbonate mixed absorbent.

[0056] The reaction-separation integrated device includes a micro-bubble gas distributor 10, a preliminary separation device 11 and an absorption tower 12.

[0057] The micro-bubble gas distributor 10 is arranged in the absorption tower 12, the gas inlet 7 is arranged on the absorption tower 12, and the gas enters the absorption tower 12 from the gas inlet 7 and is dispersed into bubbles smaller than a preset value (for example, 500μm) after the micro-bubble gas distributor 10.

[0058] The absorption tower comprises a main pipeline, a first pipeline 13 and a second pipeline 14. The main pipeline is filled with a carbon dioxide absorbent. The first pipeline 13 and the second pipeline 14 are both in communication with the main pipeline and are integrally arranged. After the bubbles react with the carbon dioxide absorbent in the main pipeline, the bubbles enter the preliminary separation device 11 through the second pipeline 14. After the preliminary separation device 11 performs preliminary solid-liquid separation, small-particle slurry is returned to the main pipeline, and large-particle slurry enters the solid-liquid separation device 2 through a liquid pipeline. The concentration of the small-particle slurry is lower than that of the large-particle slurry, and the size of the slurry particles can be set according to actual application requirements.

[0059] In this embodiment, a mixed solution composed of a potassium carbonate solution with a mass concentration of 60% and a sodium carbonate solution with a mass concentration of 25% is used as the absorbent. Flue gas enters the carbon dioxide absorption device 1 from the gas inlet 7, is dispersed into fine bubbles smaller than 500 μm by the micro-bubble gas distributor 10 to improve the reaction rate, and the reaction temperature in the carbon dioxide absorption device 1 is 105°C. CO2 in the flue gas reacts with the potassium carbonate / sodium carbonate solution to generate potassium bicarbonate and sodium bicarbonate solids. The 105°C slurry first undergoes preliminary solid-liquid separation in the preliminary separation device 11 in the reaction-separation integrated carbon dioxide absorption device 1. Low-concentration slurry (i.e., small-particle slurry) is returned to the carbon dioxide absorption device 1 from the top outlet of the preliminary separation device 11 through the first pipeline 13 to continue to participate in the reaction, and high-solid-content concentrated slurry is formed at the bottom outlet of the preliminary separation device 11.

[0060] The 105°C water vapor and unreacted gas in the carbon dioxide absorption device 1 enter the first heat exchange device 4 through a gas pipeline, and the low-concentration slurry enters the first heat exchange device 4 through a slurry pipeline. The first heat exchange device 4 contains boiling water at 100°C under normal pressure. The 105°C water vapor is condensed into liquid water to separate from the unreacted gas and is returned to the carbon dioxide absorption device 1 through a liquid pipeline for recycling. The unreacted gas is discharged from the unreacted gas outlet 8. The 105°C low-concentration slurry exchanges heat with the 100°C boiling water and is returned to the carbon dioxide absorption device 1 through a slurry pipeline. The boiling water in the first heat exchange device 4 absorbs heat and continuously vaporizes into water vapor that enters the heat pump 6. The water vapor in the heat pump 6 changes into liquid water through phase change while releasing a large amount of latent heat, generating 130°C steam that enters the carbon dioxide desorption device 3. The low-temperature liquid water in the heat pump 6 is returned to the first heat exchange device 4 and the second heat exchange device 5 through a liquid pipeline for recycling.

[0061] The high-solid-content concentrated slurry (i.e., large-particle slurry) formed at the bottom outlet of the preliminary separation device 11 enters the solid-liquid separation device 2 through a slurry pipeline. The clear liquid after separation is returned to the carbon dioxide absorption device 1 through a clear liquid return pipeline for recycling. The separated potassium bicarbonate and sodium bicarbonate solids enter the carbon dioxide desorption device 3 through a pipeline.

[0062] The reaction temperature in the carbon dioxide desorption device 3 is 115℃, the decomposition reaction of the potassium bicarbonate / sodium bicarbonate solid mixture is generated by the heat energy provided by the heat pump 6, and the potassium carbonate / sodium carbonate mixture, water vapor and CO2 are generated, wherein the water vapor and CO2 enter the second heat exchange device 5 through the gas pipeline, the boiling water at normal pressure 100℃ in the second heat exchange device 5, the generated water vapor is condensed into liquid water to separate from the CO2 gas, and returns to the carbon dioxide absorption device 1 for recycling, the CO2 gas is discharged from the CO2 gas outlet 8, the boiling water is continuously heated and vaporized into water vapor into the heat pump 6, the water vapor in the heat pump 6 is changed into liquid water by phase change, and a large amount of latent heat is released, generating 130℃ steam to continue to heat the carbon dioxide desorption device 3, and the low-temperature liquid water in the heat pump 6 returns to the first heat exchange device 4 and the second heat exchange device 5 through the liquid pipeline for recycling.

[0063] The potassium carbonate / sodium carbonate mixed solid generated in the carbon dioxide desorption device 3 is returned to the carbon dioxide absorption device 1 through the pipeline as an absorbent for recycling.

[0064] Based on the above description, the present application has the following advantages compared with the prior art:

[0065] Firstly, the present application uses a compound aqueous solution as an absorbent, and after the absorbent absorbs CO2 in the carbon dioxide absorption device, the absorbent changes phase to generate a solid-state absorption product. After solid-liquid separation of the solid-liquid mixture in the carbon dioxide absorption device, only the solid-state absorption product is sent to the carbon dioxide desorption device for heating and decomposition to realize the desorption process, without the need to heat a large amount of liquid. This can greatly reduce the energy consumption of desorption and regeneration. On the other hand, since the carbon dioxide desorption process has a higher temperature than the absorption process, the absorbent solution after desorption needs to be cooled before entering the carbon dioxide absorption device for repeated use. Therefore, the present application can avoid the waste of low-grade heat caused by the cooling of a large amount of absorbent solution after desorption, thereby reducing energy consumption.

[0066] Secondly, the present application combines the heat exchange device with the heat pump, uses the characteristics that the latent heat of water vaporization is 2000 times and 1000 times more than the specific heat of gas and liquid respectively, fully utilizes the reaction heat of CO2 absorption, and uses the latent heat recovery heat pump (the cycle performance coefficient COP is generally 4-10) to realize the upgrading of the heat grade of the water vapor generated by the heat exchange device, thereby providing energy for the carbon dioxide desorption process, realizing the reuse of the latent heat of steam, not only can the reaction heat of the carbon dioxide absorption stage be used for the endothermic process of the desorption stage, but also avoids the large and repeated temperature rising and falling process between the absorption and desorption devices in the traditional carbon dioxide chemical capture process, thereby reducing the heat consumption, the theoretical regeneration energy consumption of the absorbent can be reduced to below 0.8 GJ / (t CO2), and the comprehensive regeneration energy consumption is expected to be reduced to below 1.4 GJ / (t CO2), thereby significantly reducing the energy consumption of the absorbent regeneration process and the carbon dioxide capture process.

[0067] Thirdly, the present application uses high-concentration absorbent (the absorbent concentration is more than twice that of the traditional method) for phase change reaction, not only overcomes the low chemical absorption reaction rate caused by the low concentration of absorbent in the traditional method to prevent reaction crystallization deposition and cause pipeline blockage, but also significantly reduces the reactor volume of the absorption and regeneration device.

[0068] Finally, the present application realizes the recycling of water participating in heat exchange and chemical reaction through the phase change of water in a closed system, thereby reducing water consumption.

[0069] In addition, the present application avoids the repeated transportation of a large amount of solvent in the traditional method through the phase change of water and absorbent, thereby reducing power consumption.

[0070] Each embodiment in the specification is described in a progressive manner, and each embodiment focuses on the difference from other embodiments, and the same or similar parts between each embodiment can be referred to each other.

[0071] The principles and implementation modes of the present application are described by applying specific examples, and the above embodiment description is only used to help understand the method of the present application and its core idea; meanwhile, for those skilled in the art, according to the idea of the present application, the specific implementation mode and application range can be changed. In conclusion, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A carbon dioxide capture system, characterized by, The application relates to a carbon dioxide absorption device, a solid-liquid separation device, a carbon dioxide desorption device, a first heat exchange device, a second heat exchange device and a heat pump. The top end outlet of the carbon dioxide absorption device is connected with the first inlet of the first heat exchange device through a gas pipeline; the side end outlet of the carbon dioxide absorption device is connected with the second inlet of the first heat exchange device through a slurry pipeline; the first side end inlet of the carbon dioxide absorption device is connected with the first outlet of the first heat exchange device through a slurry pipeline; and the bottom end of the carbon dioxide absorption device is provided with a gas inlet. The second outlet of the first heat exchange device is connected with the first inlet of the heat pump through a steam pipeline; the first outlet of the heat pump is connected with the third inlet of the first heat exchange device and the first inlet of the second heat exchange device through a liquid pipeline; the second outlet of the heat pump is connected with the first side end inlet of the carbon dioxide desorption device through a steam pipeline; the top end outlet of the carbon dioxide desorption device is connected with the second inlet of the second heat exchange device through a gas pipeline; the first outlet of the second heat exchange device is connected with the second inlet of the heat pump through a steam pipeline; the second outlet of the second heat exchange device is connected with the first side end inlet of the carbon dioxide absorption device through a liquid pipeline; the bottom end outlet of the carbon dioxide absorption device is connected with the first inlet of the solid-liquid separation device through a slurry pipeline; the first outlet of the solid-liquid separation device is connected with the second side end inlet of the carbon dioxide desorption device through a pipeline; and the bottom end outlet of the carbon dioxide desorption device and the second outlet of the solid-liquid separation device are both connected with the second side end inlet of the carbon dioxide absorption device through a slurry pipeline. The carbon dioxide absorption device is at least a primary absorption tower.

2. The carbon dioxide capture system of claim 1, wherein, The primary absorption tower is filled with a carbon dioxide absorption agent. The carbon dioxide absorption agent is a compound solution capable of realizing reaction crystallization phase change.

3. The carbon dioxide capture system of claim 2, wherein, The compound solution comprises a potassium carbonate solution and / or a sodium carbonate solution.

4. The carbon dioxide capture system of claim 3, wherein, The carbon dioxide absorption device is a reaction separation integrated device.

5. The carbon dioxide capture system of claim 1, wherein, The reaction separation integrated device comprises a micro-bubble gas distributor, a preliminary separation device and an absorption tower.

6. The carbon dioxide capture system of claim 5, wherein, The micro-bubble gas distributor is arranged at the bottom of the absorption tower, the gas inlet is arranged on the absorption tower, and gas enters the absorption tower from the gas inlet and is dispersed into bubbles smaller than a preset value through the micro-bubble gas distributor. The absorption tower comprises a main pipeline, a first pipeline and a second pipeline; the main pipeline is filled with a carbon dioxide absorption agent; the first pipeline and the second pipeline are both in communication with the main pipeline and are integrally arranged; after the bubbles react with the carbon dioxide absorption agent in the main pipeline, the bubbles enter the preliminary separation device through the second pipeline; after the preliminary separation device performs preliminary solid-liquid separation, small-particle slurry is returned to the main pipeline, and large-particle slurry enters the solid-liquid separation device through a liquid pipeline; the concentration of the small-particle slurry is smaller than that of the large-particle slurry, and the size of the slurry particles is determined based on a set particle value. ​ 7. The carbon dioxide capture system of claim 1, wherein, The first heat exchange device is provided with an unreacted gas outlet, and the second heat exchange device is provided with a carbon dioxide gas outlet.

8. The carbon dioxide capture system of claim 1, wherein, The first heat exchange device and the second heat exchange device are both cooling heat exchange evaporators.

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