Carbon dioxide desorption system and method using phase change heat storage material and solar collector for peak regulation

Abstract

Disclosed in the present invention are a carbon dioxide desorption system and method using a phase change heat storage material and a solar collector for peak regulation. The carbon dioxide desorption system comprises a carbon dioxide desorption column (1), a phase change heat exchanger (10) and a solar collector (12); a rich solution conveying pipe (2) is connected to the top of the carbon dioxide desorption column (1), while a lean solution conveying pipe (3) is connected to the bottom of the carbon dioxide desorption column (1); a heat conduction medium pipe (101), a phase change material layer (103) and a solution heat exchange coil (102) are provided in the phase change heat exchanger (10), the phase change material layer (103) being filled with a phase change material; the positions of the carbon dioxide desorption column (1) close to the middle and the bottom are respectively connected to an inlet and an outlet of the solution heat exchange coil (102); an inlet and an outlet of the solar collector (12) are respectively connected to two ends, i.e. an outlet and an inlet, of the heat conduction medium pipe (101).

Description

A carbon dioxide desorption system and method using phase change heat storage material and solar collector peak regulation Technical Field

[0001] The present invention belongs to the field of carbon dioxide capture, and relates to a carbon dioxide desorption system and method using phase change heat storage materials and solar collectors for peak regulation. Background Art

[0002] Carbon dioxide capture technology is used to remove carbon dioxide from gas streams or to separate it as a gaseous product. Capture is the first step in carbon capture and storage (CCS). Carbon dioxide must be present at a high purity for transportation and storage. In most cases, the concentration of carbon dioxide in industrial exhaust gases does not meet this requirement, so it must be separated from the exhaust gases. This process is called carbon dioxide capture. Technical issues

[0003] Currently, the commonly used method in the field of carbon dioxide capture is to use steam as a heating source to heat the solution to release carbon dioxide after the solution absorbs carbon dioxide. However, in actual application, there is usually a large amount of steam consumption, steam heat loss during the cooling and pressure reduction process, and waste of steam waste heat after heat exchange, resulting in high energy consumption of the carbon capture system, insufficient resource utilization, and high capture cost. Technical Solutions

[0004] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a carbon dioxide desorption system and method using phase change heat storage materials and solar collectors for peak regulation, thereby ensuring the normal and stable desorption operation of the carbon dioxide capture system during the day and greatly reducing the operating costs and steam consumption of the daytime carbon capture system.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A carbon dioxide desorption system using phase change heat storage materials and solar thermal collectors for peak regulation, comprising a carbon dioxide desorption tower, a phase change heat storage device and a solar thermal collector;

[0007] The top of the carbon dioxide desorption tower is connected to a rich liquid delivery pipe, and the bottom of the carbon dioxide desorption tower is connected to a lean liquid delivery pipe; the phase change heat exchanger is provided with a heat transfer medium pipeline, a phase change material layer and a solution heat exchange coil, and the phase change material layer is filled with phase change material;

[0008] The carbon dioxide desorption tower is connected to the inlet and outlet of the solution heat exchange coil near the middle and near the bottom respectively, and the inlet and outlet of the solar collector are connected to the outlet and inlet ends of the heat transfer medium pipeline respectively.

[0009] Preferably, a rich liquid heating pipe is connected to the inlet of the solution heat exchange coil near the middle of the carbon dioxide desorption tower, and a lean liquid reflux pipe is connected to the outlet of the solution heat exchange coil near the bottom of the carbon dioxide desorption tower; a steam heat exchanger is connected between the rich liquid heating pipe and the lean liquid reflux pipe, the inlet of the steam heat exchanger is connected to the rich liquid heating pipe, and the outlet of the steam heat exchanger is connected to the lean liquid reflux pipe, a rich liquid steam heat exchange valve is provided at the inlet of the steam heat exchanger, a rich liquid phase change heat inlet valve is provided at the rich liquid heating pipe near the phase change heat exchanger, and a rich liquid phase change heat outlet valve is provided at the lean liquid reflux pipe near the phase change heat exchanger.

[0010] Preferably, the interior of the shell is a two-layer sealed structure, the outer layer is a heat transfer medium pipeline, and the inner layer is a phase change material layer. The heat transfer medium pipeline is attached to the outer wall of the phase change material layer, and the solution heat exchange coil is buried inside the phase change material layer.

[0011] Preferably, the phase change material is a medium-temperature phase change material having a phase change temperature of 120-150°C.

[0012] Preferably, polyethylene glycol is added to the phase change material at a mass ratio of 2%-5%.

[0013] Preferably, 2%-5% of organic carbon material is added to the phase change material.

[0014] Preferably, the carbon dioxide desorption tower is provided with multiple levels of packing layers from top to bottom.

[0015] Preferably, heat transfer oil is provided in the heat transfer medium pipeline.

[0016] A carbon dioxide desorption method for the system comprises the following steps: a carbon dioxide absorption solution enters the top of a carbon dioxide desorption tower through a rich liquid delivery pipe, and then enters a phase change heat exchanger. Heat stored in a solar thermal collector is used as a heat source for heating and heat preservation of a phase change material. The heated phase change material heats and desorbs the rich liquid, and the solution after heat exchange returns to the bottom of the carbon dioxide desorption tower.

[0017] Preferably, when the sunlight intensity is sufficient and the temperature of the heat transfer medium in the solar thermal collector reaches the phase change temperature of the phase change material in the phase change heat exchanger, the rich liquid phase change heat inlet valve and the rich liquid phase change heat outlet valve are opened, the rich liquid steam heat exchange valve is closed, and the solution enters the phase change heat exchanger for heating and desorption; when the sunlight intensity is insufficient or at night, the temperature of the heat transfer medium in the solar thermal collector cannot reach the phase change temperature of the phase change material in the phase change heat exchanger, the rich liquid phase change heat inlet valve and the rich liquid phase change heat outlet valve are closed, the rich liquid steam heat exchange valve is opened, the solution enters the steam heat exchanger, and steam is used as the heat source to heat and desorb the solution. Beneficial effects

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention improves the internal structure of the heat exchanger, places the phase change material inside the heat exchanger, and fully contacts and exchanges heat with the solution heat exchange coil. The heat-conducting medium heated by the solar thermal collector enters the phase change heat exchanger to heat and keep the phase change material in the phase change heat exchanger warm. The phase change material is used as a heat source for heat exchange of the carbon capture solution by storing a large amount of latent heat during the phase change process. The heat accumulated in the solar thermal collector is used as a heat source for heating and keeping the phase change material warm, which can ensure the normal and stable desorption operation of the carbon dioxide capture system during the day, greatly reducing the operating cost and steam consumption of the carbon capture system during the day.

[0020] Furthermore, a steam heat exchanger is provided to ensure normal operation of the carbon capture system at night or when sunlight conditions are poor.

[0021] Furthermore, polyethylene glycol is used as an auxiliary agent to improve the stability of the phase change material.

[0022] Furthermore, the use of organic carbon materials can increase the thermal conductivity of phase change materials by more than 40% and reduce the heat storage time of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG1 is a schematic diagram of a carbon dioxide desorption system for peak regulation using phase change heat storage materials and solar thermal collectors according to the present invention.

[0024] Among them: 1-carbon dioxide desorption tower; 2-rich liquid conveying pipe; 3-lean liquid conveying pipe; 4-rich liquid heating pipe; 5-lean liquid reflux pipe; 6-steam heat exchanger; 7-rich liquid steam heat exchange valve; 8-rich liquid phase change heat inlet valve; 9-rich liquid phase change heat outlet valve; 10-phase change heat exchanger; 11-heat transfer medium outlet; 12-solar collector; 13-heat transfer medium inlet; 101-heat transfer medium pipeline; 102-solution heat exchange coil; 103-phase change material layer. Modes for Carrying Out the Invention

[0025] As shown in FIG1 , the carbon dioxide desorption system using phase change heat storage materials and solar thermal collectors for peak regulation according to the present invention includes a carbon dioxide desorption tower 1 , a steam heat exchanger 6 , a phase change heat exchanger 10 and a solar thermal collector 12 .

[0026] The top of the carbon dioxide desorption tower 1 is connected to a rich liquid delivery pipe 2, and the bottom of the carbon dioxide desorption tower 1 is connected to a lean liquid delivery pipe 3. The interior of the carbon dioxide desorption tower 1 is provided with multiple levels of packing layers from top to bottom.

[0027] The phase change heat exchanger 10 includes a shell, and a solution inlet and a heat transfer medium outlet 11 are respectively provided on both sides of the top end of the shell, and a solution outlet and a heat transfer medium inlet 13 are respectively provided on both sides of the bottom end of the shell. The interior of the shell is a two-layer sealed structure, the outer layer is a heat transfer medium pipe 101, and the inner layer is a phase change material layer 103. The two ends of the heat transfer medium pipe 101 are respectively connected to the heat transfer medium outlet 11 and the heat transfer medium inlet 13, and the two ends of the solution heat exchange coil 102 are respectively connected to the solution inlet and the solution outlet. The interior of the phase change material layer 103 is sealed and filled with phase change material. The heat transfer medium pipe 101 is attached to the outer wall of the phase change material layer 103 to heat and insulate the phase change material. The solution heat exchange coil 102 is buried in the interior of the phase change material layer 103 and is arranged in a spiral shape to fully exchange heat with the phase change material to increase the temperature.

[0028] Select medium-temperature phase change materials with a phase change temperature of 120-150°C and low cost, such as magnesium chloride hexahydrate with a phase change temperature of 118°C and erythritol with a phase change temperature of 126°C. In addition, 2%-5% by mass of polyethylene glycol can be added to the phase change material as an additive to improve the stability of the phase change material, or 2%-5% by mass of organic carbon materials such as graphene or carbon nanotubes can be added to increase the thermal conductivity of the phase change material by more than 40% and reduce the heat storage time of the material.

[0029] A rich liquid heating pipe 4 is used near the middle of the carbon dioxide desorption tower 1 to be connected to the solution inlet of the phase change heat exchanger 10, and a lean liquid reflux pipe 5 is used near the bottom of the carbon dioxide desorption tower 1 to be connected to the solution outlet of the phase change heat exchanger 10. The semi-lean liquid after heating and desorption in the packing layer enters the phase change heat exchanger 10 through the rich liquid heating pipe 4, is heated and desorbed through the phase change material layer 103, and the lean liquid after heating and desorption returns to the carbon dioxide desorption tower 1 through the lean liquid reflux pipe 5.

[0030] A medium inlet is provided at the top of the solar thermal collector 12, and a medium outlet is provided at the bottom of the solar thermal collector 12. The medium inlet of the solar thermal collector 12 is connected to the heat conducting medium outlet 11 of the phase change heat exchanger 10, and the medium outlet of the solar thermal collector 12 is connected to the heat conducting medium inlet 13 of the phase change heat exchanger 10. After the heat conducting medium is heated inside the solar thermal collector 12, it is transported to the heat conducting medium pipeline 101 of the phase change heat exchanger 10 to heat and insulate the phase change material. The heat conducting medium after heat exchange returns to the solar thermal collector 12 for reheating.

[0031] A steam heat exchanger 6 is connected between the rich liquid heating pipe 4 and the lean liquid return pipe 5. The inlet of the steam heat exchanger 6 is connected to the rich liquid heating pipe 4, and the outlet of the steam heat exchanger 6 is connected to the lean liquid return pipe 5. A rich liquid steam heat exchange valve 7 is provided at the inlet of the steam heat exchanger 6. A rich liquid phase change heat inlet valve 8 is provided near the phase change heat exchanger 10 of the rich liquid heating pipe 4, and a rich liquid phase change heat outlet valve 9 is provided near the phase change heat exchanger 10 of the lean liquid return pipe 5. By switching the rich liquid steam heat exchange valve 7, the rich liquid phase change heat inlet valve 8, and the rich liquid phase change heat outlet valve 9, the solution heating route and method can be controlled. When the rich liquid steam heat exchange valve 7 is closed and the rich liquid phase change heat inlet valve 8 and the rich liquid phase change heat outlet valve 9 are opened, the solution is heated and desorbed through the phase change heat exchanger 10. When the rich liquid steam heat exchange valve 7 is opened and the rich liquid phase change heat inlet valve 8 and the rich liquid phase change heat outlet valve 9 are closed, the solution is heated and desorbed through the steam heat exchanger 6.

[0032] The internal structure of the heat exchanger is improved, and the phase change material is placed inside the heat exchanger for full contact and heat exchange with the solution heat exchange coil 102. The heat-conducting medium heated by the solar collector 12 enters the phase change heat exchanger 10 to heat and keep the phase change material in the phase change heat exchanger 10 warm. The three-layer structure uses corrosion-resistant and high-temperature resistant materials to prevent the phase change material from corroding the pipeline in the liquid state.

[0033] A heat storage phase change material is placed in the phase change material layer 103 within the phase change heat exchanger 10. By utilizing the inherent physical properties of the phase change material, it stores a large amount of latent heat during the phase change process and then changes from a solid state to a liquid state. After heating stops, the phase change material releases heat in three stages to exchange heat with the solution. The first stage releases sensible heat from the liquid. The second stage begins when the phase change material temperature drops to the phase change temperature and begins to release a large amount of latent heat, which remains constant for a long time. Finally, the phase change material returns to a solid state and releases sensible heat from the solid material. The rich carbon dioxide capture solution enters the phase change heat exchanger 10 through the solution heat exchange coil 102, fully exchanging heat with the phase change material to increase its temperature. The heat transfer medium transported by the solar collector 12 enters the heat transfer medium pipeline 101 of the phase change heat exchanger 10 to heat and insulate the phase change material.

[0034] In this embodiment, the heat transfer medium is heat transfer oil.

[0035] By using an improved phase change heat exchanger 10 and placing a phase change material as a filling material inside the phase change heat exchanger 10, the phase change material is used as a heat source for heat exchange of the carbon capture solution due to its ability to store a large amount of latent heat during the phase change process. The heat stored in the solar collector 12 is used as a heat source for heating and heat preservation of the phase change material. This can ensure the normal and stable desorption operation of the carbon dioxide capture system during the day, greatly reducing the operating cost and steam consumption of the carbon capture system during the day. At the same time, a steam heat exchanger 6 is set outside the system to ensure the normal operation of the carbon capture system at night.

[0036] After the carbon dioxide absorption solution is saturated and exchanges heat with the lean liquid, it enters the top of the carbon dioxide desorption tower 1 through the rich liquid delivery pipe 2. It passes through the multi-stage packing layer from top to bottom for heating and desorption. The semi-lean liquid enters the phase change heat exchanger 10 or the steam heat exchanger 6 through the rich liquid heating pipe 4. The electric valve and the sunlight intensity determine whether to adopt the peak shaving strategy:

[0037] (1) When the sunshine intensity is sufficient and the temperature of the heat transfer oil in the solar collector 12 reaches the phase change temperature of the phase change material in the phase change heat exchanger 10, the rich liquid phase change heat inlet valve 8 and the rich liquid phase change heat outlet valve 9 are opened, and the rich liquid steam heat exchange valve 7 is closed. The heat of the solar collector 12 and the heat in the phase change material are used as heat sources to heat and desorb the rich liquid solution. The solution after heat exchange returns to the bottom of the carbon dioxide desorption tower 1 through the lean liquid reflux pipe 5;

[0038] (2) When the sunshine intensity is insufficient or at night, the temperature of the heat transfer oil in the solar collector 12 cannot reach the phase change temperature of the phase change material in the phase change heat exchanger 10. The rich liquid phase change heat inlet valve 8 and the rich liquid phase change heat outlet valve 9 are closed, and the rich liquid steam heat exchange valve 7 is opened. The steam in the steam heat exchanger 6 is used as a heat source to heat and desorb the solution.

Claims

1. A carbon dioxide desorption system using phase change heat storage materials and solar collectors for peak regulation, characterized in that: It includes a carbon dioxide desorption tower (1), a phase change heat exchanger (10) and a solar heat collector (12); The top of the carbon dioxide desorption tower (1) is connected to a rich liquid delivery pipe (2), and the bottom of the carbon dioxide desorption tower (1) is connected to a lean liquid delivery pipe (3); a heat transfer medium pipe (101), a phase change material layer (103) and a solution heat exchange coil (102) are provided inside the phase change heat exchanger (10), and the phase change material layer (103) is filled with phase change material; The carbon dioxide desorption tower (1) is connected to the inlet and outlet of the solution heat exchange coil (102) near the middle and near the bottom respectively, and the inlet and outlet of the solar collector (12) are connected to the outlet and inlet ends of the heat transfer medium pipeline (101) respectively.

2. The carbon dioxide desorption system using phase change heat storage materials and solar collectors for peak regulation according to claim 1 is characterized in that: A rich liquid heating pipe (4) is connected to the inlet of the solution heat exchange coil (102) near the middle of the carbon dioxide desorption tower (1), and a lean liquid reflux pipe (5) is connected to the outlet of the solution heat exchange coil (102) near the bottom of the carbon dioxide desorption tower (1); a steam heat exchanger (6) is connected between the rich liquid heating pipe (4) and the lean liquid reflux pipe (5); the inlet of the steam heat exchanger (6) is connected to the rich liquid heating pipe (4), and the outlet of the steam heat exchanger (6) is connected to the lean liquid reflux pipe (5); a rich liquid steam heat exchange valve (7) is provided at the inlet of the steam heat exchanger (6); a rich liquid phase change heat inlet valve (8) is provided near the phase change heat exchanger (10) of the rich liquid heating pipe (4), and a rich liquid phase change heat outlet valve (9) is provided near the phase change heat exchanger (10) of the lean liquid reflux pipe (5).

3. The carbon dioxide desorption system using phase change heat storage materials and solar thermal collectors for peak regulation according to claim 1 is characterized in that: The interior of the shell is a two-layer sealed structure, the outer layer is a heat-conducting medium pipeline (101), and the inner layer is a phase change material layer (103). The heat-conducting medium pipeline (101) is attached to the outer wall surface of the phase change material layer (103), and the solution heat exchange coil (102) is buried inside the phase change material layer (103).

4. The carbon dioxide desorption system using phase change heat storage materials and solar thermal collectors for peak regulation according to claim 1, characterized in that: The phase change material adopts a medium-temperature phase change material with a phase change temperature of 120-150°C.

5. The carbon dioxide desorption system using phase change heat storage materials and solar collectors for peak regulation according to claim 1 is characterized in that: Polyethylene glycol with a mass ratio of 2%-5% is added to the phase change material.

6. The carbon dioxide desorption system using phase change heat storage materials and solar thermal collectors for peak regulation according to claim 1, characterized in that: 2%-5% organic carbon material is added to the phase change material.

7. The carbon dioxide desorption system using phase change heat storage materials and solar thermal collectors for peak regulation according to claim 1, characterized in that: The carbon dioxide desorption tower (1) is provided with multiple levels of packing layers from top to bottom.

8. The carbon dioxide desorption system using phase change heat storage materials and solar thermal collectors for peak regulation according to claim 1, characterized in that: Heat transfer oil is provided in the heat transfer medium pipeline (101).

9. A method for desorbing carbon dioxide based on the system according to any one of claims 1 to 8, characterized in that: The carbon dioxide absorption solution enters the top of the carbon dioxide desorption tower (1) through the rich liquid delivery pipe (2), and then enters the phase change heat exchanger (10). The heat stored in the solar thermal collector (12) is used as a heat source for heating and heat preservation of the phase change material. The heated phase change material heats and desorbs the solution rich liquid, and the solution after heat exchange returns to the bottom of the carbon dioxide desorption tower (1).

10. The carbon dioxide desorption method according to claim 9, characterized in that: When the sunshine intensity is sufficient and the temperature of the heat-conducting medium in the solar thermal collector (12) reaches the phase change temperature of the phase change material in the phase change heat exchanger (10), the rich liquid phase change heat inlet valve (8) and the rich liquid phase change heat outlet valve (9) are opened, the rich liquid steam heat exchange valve (7) is closed, and the solution enters the phase change heat exchanger (10) for heating and desorption; when the sunshine intensity is insufficient or at night, the temperature of the heat-conducting medium in the solar thermal collector (12) cannot reach the phase change temperature of the phase change material in the phase change heat exchanger (10), the rich liquid phase change heat inlet valve (8) and the rich liquid phase change heat outlet valve (9) are closed, the rich liquid steam heat exchange valve (7) is opened, and the solution enters the steam heat exchanger (6), and steam is used as a heat source to heat and desorb the solution.

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