Shipborne carbon capture system and temperature control method in absorption process of shipborne carbon capture system

Abstract

The invention provides a shipborne carbon capture system and a temperature control method of an absorption process of the shipborne carbon capture system. The system adopts a chemical absorption method for carbon capture, and comprises a waste gas inlet device, a waste gas cooling tower, an absorption tower and a chemical absorbent inlet device. The process control of the temperature characteristic value of the chemical absorbent in the process of absorbing CO2 in the ship tail gas by the shipborne carbon capture system is realized through the linkage control of two units, namely the waste gas cooling tower and the absorption tower, so that the chemical absorbent keeps high forward absorption rate in the process of absorbing low-concentration CO2 in the ship tail gas; in other words, the absorption efficiency of the chemical absorbent in unit volume is improved, so that the economical efficiency of the operation of the shipborne carbon capture system is higher.

Description

Technical Field

[0001] The present invention relates to the technical field of ship emission control and ship engine carbon capture, and in particular to a ship-borne carbon capture system and a temperature control method for an absorption process thereof. Background Art

[0002] The use of alternative fuels such as natural gas, methanol and ammonia can effectively reduce carbon emissions from shipping vessels from the source, but there are still many problems to be faced, such as the limited carbon reduction capacity of natural gas fuel, insufficient supply of green methanol fuel, and difficult combustion control of ammonia fuel. These problems have not been effectively solved. As a negative emission technology, shipboard carbon capture technology can effectively reduce greenhouse gas (Green House Gas, GHG) emissions and maintain the flexibility of the original power system. The positioning and role of this technology in the field of ship applications are becoming more and more prominent. At the same time, with the gradual clarification of carbon taxes and related regulations, shipowners and ship operators have an increasingly strong demand for shipping carbon reduction solutions. The chemical absorption method has the advantages of little impact on the existing ship power system, no need to modify the existing ship engine, and relatively low system complexity. It is currently the mainstream research and development direction of shipboard carbon capture technology.

[0003] Usually, the exhaust temperature after the supercharger of a low-speed two-stroke engine of an ocean-going ship is about 200°C, and the exhaust gas volume and temperature will fluctuate and change during operation, especially during the engine load change process. That is, during the engine operation or load change process, if the air inlet of the pretreatment section and the absorption section of the shipboard carbon capture system is not controlled by temperature, it will affect the gas-liquid mass transfer rate between the raw gas (engine exhaust gas) and the chemical absorbent during the absorption process, thereby affecting the CO2 absorption capacity of the system (absorption rate and absorption capacity of the chemical absorbent).

[0004] Therefore, in the existing shipboard carbon capture system, when using alcohol amine absorbents (such as monoethanolamine MEA) to absorb CO2, temperature control is a key factor to ensure efficient absorption of carbon dioxide in exhaust gas. However, the exhaust temperature and flow rate of ocean-going ship engines fluctuate greatly, and the absorption process is an exothermic reaction, which makes it difficult to stably maintain the system temperature in the optimal reaction temperature range. At present, there is no effective patent to solve this problem, especially in the aspects of exhaust gas pretreatment and temperature control of the absorption process. Summary of the invention

[0005] The present invention aims to provide a shipboard carbon capture system and a temperature control method for its absorption process, specifically a shipboard carbon capture system using an amine solution chemical absorption method, which ensures that the temperature of the exhaust gas before entering the absorption tower and during the absorption process is maintained in an optimal reaction temperature range through a multi-stage temperature control strategy in the exhaust gas cooling tower and the absorption tower, thereby improving the CO2 absorption efficiency and the stability of the system.

[0006] In order to achieve the above object, the present invention provides a ship-borne carbon capture system, which uses a chemical absorption method to capture carbon, and the system comprises:

[0007] An exhaust gas inlet device for introducing exhaust gas from the ship's engine into the exhaust gas cooling tower;

[0008] An exhaust gas cooling tower, the exhaust gas cooling tower comprises a deionized water circulation system, a first heat exchanger and a deionized water replenishment system, wherein: the circulating water in the deionized water circulation system sprays the exhaust gas, then exchanges heat with cold source seawater through the first heat exchanger for cooling, and then circulates back to spray the exhaust gas; the exhaust gas outlet temperature is controlled by adjusting the flow of seawater entering the first heat exchanger to keep the exhaust gas within the optimal reaction temperature range of the chemical absorbent; the deionized water replenishment system automatically replenishes the deionized water reduced due to the water vapor carried away by the exhaust gas according to the liquid level signal in the tower;

[0009] The absorption tower is used to receive the waste gas after cooling from the waste gas cooling tower, and use an alcohol amine solution to capture CO2 in the waste gas; the absorption tower includes a heat exchanger assembly, a backwash section circulating water system, a demister packing layer from top to bottom, a backwash section packing layer and at least one absorption packing layer; the bottom of the absorption tower is connected to the top of the waste gas cooling tower; the heat exchanger assembly exchanges heat with the chemical absorbent through the cold source seawater to keep the temperature of the chemical absorbent in each section of the absorption tower within the optimal reaction temperature range; the backwash section circulating water system includes an overflow liquid collection tray arranged below the backwash section packing layer, which is used to perform overflow water washing on the backwash section packing layer;

[0010] The chemical absorbent inlet device is used to introduce the alcohol amine solution into the lower part of the backwash section packing layer of the absorption tower and is located above the absorption packing layer.

[0011] The chemical absorbent used in the present invention is an alcohol amine solution.

[0012] Furthermore, the alcoholamine solution originates from the bottom of the desorption tower.

[0013] Furthermore, the seawater flow rate of the first heat exchanger is controlled by a temperature signal of the exhaust gas discharged from the exhaust gas cooling tower, and is achieved by adjusting the valve opening of the seawater flow regulating valve in the first heat exchanger.

[0014] Furthermore, the heat exchanger assembly includes a plurality of independently controlled heat exchangers, which adjust the seawater flow entering each heat exchanger according to the chemical absorbent temperature signal in different areas of the absorption tower, so as to achieve precise control of the temperature of the chemical absorbent in each section of the absorption tower.

[0015] Furthermore, the heat exchanger assembly includes a chemical absorbent inlet section heat exchanger, a backwash section heat exchanger, and an absorption section heat exchanger.

[0016] Furthermore, the chemical absorbent enters the heat exchanger, and the flow rate of seawater entering the heat exchanger is adjusted according to the temperature signal before the chemical absorbent enters the absorption tower.

[0017] Furthermore, the backwash section heat exchanger adjusts the flow rate of seawater entering the heat exchanger according to the temperature signal of the circulating water before entering the backwash section packing layer.

[0018] Furthermore, the absorption section heat exchanger adjusts the flow rate of seawater entering the heat exchanger according to the temperature signal of the chemical absorbent in the tower.

[0019] Furthermore, the absorption tower comprises multiple absorption filler layers, and each absorption filler layer is equipped with an absorption section heat exchanger.

[0020] Furthermore, the heat exchanger of the present invention comprises a first heat exchanger, a chemical absorbent inlet heat exchanger, a backwashing heat exchanger, and an absorption heat exchanger, and the flow of seawater entering the heat exchanger is regulated by the valve opening of a seawater flow regulating valve. Preferably, the regulating valve is preferably an electrically regulated three-way valve, in which a portion of the seawater (the cold inlet seawater temperature is 32°C by default) flows through the heat exchanger, and the other portion of the seawater is directly discharged overboard through the bypass of the three-way valve.

[0021] Furthermore, the absorption tower also includes a liquid level control system and an absorbent replenishing device. The liquid level control system monitors the liquid level signals of each section. When the liquid level is too low, the solution circulation pump is stopped, and when the liquid level is too high, the frequency of the circulation pump is increased. The absorbent replenishing device monitors the concentration of the rich amine solution in the absorption tower. When it is lower than a preset minimum value, fresh alcoholamine solution is replenished into the absorption tower, and when it is higher than a preset maximum value, deionized water is replenished into the absorption tower.

[0022] In the present invention, after the alcohol amine solution absorbs CO2, a rich amine solution is formed. After the rich amine solution is heated, high-concentration CO2 is released and the alcohol amine solution is regenerated for recycling.

[0023] The present invention also provides a method for controlling the temperature of the absorption process of a shipboard carbon capture system. The method is applied to a shipboard carbon capture system that uses a chemical absorption method to capture carbon. The system includes an exhaust gas cooling tower and an absorption tower. The method includes the following steps:

[0024] a. Introduce the exhaust gas of the ship engine into the exhaust gas cooling tower;

[0025] b. In the exhaust gas cooling tower, the circulating water is used to spray the exhaust gas, which is then cooled by heat exchange with the cold source seawater in the first heat exchanger and then circulated back to spray the exhaust gas; according to the temperature signal of the exhaust gas discharged from the exhaust gas cooling tower, the flow rate of seawater entering the first heat exchanger is adjusted to control the exhaust gas outlet temperature to remain within the optimal reaction temperature range of the chemical absorbent; at the same time, according to the liquid level signal in the tower, the deionized water that is reduced due to the exhaust gas taking away water vapor is automatically supplemented;

[0026] c. The waste gas cooled by the waste gas cooling tower is introduced into the absorption tower, and the alcohol amine solution is introduced below the backwash section packing layer of the absorption tower and above the absorption packing layer. The alcohol amine solution is used in the absorption tower to capture the CO2 in the waste gas; in the absorption tower, the chemical absorbent is heat exchanged through the heat exchanger assembly to maintain the temperature of the chemical absorbent in each section of the absorption tower within the optimal reaction temperature range; at the same time, the backwash section packing layer is overflow-washed.

[0027] Furthermore, in step b, the seawater flow rate of the first heat exchanger is controlled by a temperature signal of the exhaust gas discharged from the exhaust gas cooling tower, which is achieved by adjusting the valve opening of the seawater flow regulating valve in the first heat exchanger.

[0028] Furthermore, the heat exchanger assembly in step c includes a plurality of independently controlled heat exchangers, and the seawater flow entering each heat exchanger is adjusted according to the temperature signal of the chemical absorbent in different areas of the absorption tower, so as to achieve precise control of the temperature of the chemical absorbent in each section of the absorption tower.

[0029] Furthermore, the heat exchanger assembly comprises a chemical absorbent inlet section heat exchanger, a backwash section heat exchanger and an absorption section heat exchanger, and each heat exchanger independently adjusts the incoming seawater flow rate.

[0030] Furthermore, the temperature control method further comprises replenishing fresh alcoholamine solution to the absorption tower when the concentration of the rich amine solution in the absorption tower is lower than a preset minimum value, and replenishing deionized water to the absorption tower when the concentration of the rich amine solution in the absorption tower is higher than a preset maximum value.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] The present invention realizes process control of the temperature characteristic value of the chemical absorbent during the process of the shipboard carbon capture system absorbing CO2 in the ship's exhaust gas through the linkage control of the exhaust gas cooling tower and the absorption tower, thereby achieving the chemical absorbent to maintain a high positive absorption rate in the process of absorbing low-concentration CO2 in the ship's exhaust gas; that is, the CO2 absorption efficiency per unit volume of the chemical absorbent is improved, thereby improving the economic efficiency of the operation of the shipboard carbon capture system. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of a ship-borne carbon capture system of the present invention. DETAILED DESCRIPTION

[0034] The technical scheme of the present invention is described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments improved or adjusted by ordinary technicians in the field belong to the protection scope of the present invention. Since the present invention mainly focuses on the improvement of the methanol removal process by water washing and the operation of the methanol recovery tower, the other parts are basically the same as the prior art, so the embodiments will focus on the enumeration of the experimental data of methanol removal by water washing and the methanol recovery tower.

[0035] Figure 1 The invention content of this patent provides a ship-borne carbon capture system using chemical absorption as the technical route, including: an exhaust gas inlet device, an exhaust gas cooling tower A, an absorption tower B and a chemical absorbent inlet device.

[0036] The exhaust gas inlet device is used to introduce the exhaust gas from the ship engine into the exhaust gas cooling tower A.

[0037] Waste gas cooling tower A, the waste gas cooling tower includes a deionized water circulation system, a first heat exchanger E-A01 and a deionized water replenishment system, wherein: the circulating water in the deionized water circulation system sprays the waste gas, then exchanges heat with the cold source seawater through the first heat exchanger for cooling, and then circulates back to spray the waste gas. The circulating water exchanges heat with the waste gas in the waste gas cooling tower in a spraying manner, and the deionized water flowing to the bottom exchanges heat with the cold source seawater through the first heat exchanger E-A01; the waste gas outlet temperature is controlled by adjusting the flow of seawater entering the heat exchanger to keep the waste gas within the optimal reaction temperature range of the chemical absorbent; the deionized water replenishment system automatically replenishes the deionized water that is reduced due to the water vapor carried away by the waste gas according to the liquid level signal (LT / LIC) in the tower. Figure 1 As shown, the exhaust gas inlet device introduces the exhaust gas (stream 1) into the exhaust gas cooling tower A before entering the absorption tower, and cools the exhaust gas of the ship engine through the closed circulation of deionized water; the characteristic design of temperature control is that the temperature signal (TT: temperature transmitter, TI: temperature indication / signal) of the exhaust gas discharged from the exhaust gas cooling tower A is associated with the valve opening of the cold source seawater supply regulating valve V-A01 in the first heat exchanger E-A01 during the deionized water circulation process. Preferably, the regulating valve V-A01 is a three-way valve. The cold source provided by the cold source is controlled by pumping in a sufficient amount of seawater (stream 7), allowing a part of the seawater (the default cold inlet seawater temperature is 32°C) to flow through the heat exchanger, and the other part of the seawater is directly discharged overboard through the bypass of the electrically regulated three-way valve V-A01.

[0038] By controlling the opening of the bypass valve, the flow of seawater entering the heat exchanger is adjusted, so that the deionized water used for circulating cooling can provide sufficient cooling capacity for the exhaust gas under different flue gas temperatures and flows within the designed feed gas temperature range (after T / C of a ship's low-speed two-stroke engine).

[0039] Problem solved: The exhaust gas flow and temperature fluctuations emitted by ship engines are solved, so that the feed gas of the absorption tower in the shipboard carbon capture system (the exhaust gas of the ship engine after passing through the exhaust gas cooling tower) is always maintained in the optimal reaction temperature range of the specified chemical absorbent (for example, 40wt% MEA, the feed gas temperature of the absorption process should be controlled at 25℃~40℃), ensuring the efficient reaction process of chemical absorbent absorbing CO2.

[0040] Specifically, the deionized water replenishment system is arranged at the top of the exhaust gas cooling tower A, and deionized water replenishment water (stream 6) is replenished into the exhaust gas cooling tower A to replenish the saturated water vapor carried away by the exhaust gas of the ship engine flowing through the exhaust gas cooling tower A. The replenishment logic is: through the liquid level signal (LT: liquid level transmitter, LIC: liquid level indication control), this liquid level model is set to high, medium and low liquid level signals. When the medium or low liquid level signal is displayed, the deionized water replenishment valve V-A02 is opened; when the high liquid level signal is displayed, the deionized water replenishment valve V-A02 is closed.

[0041] The absorption tower B is used to receive the waste gas after being cooled from the waste gas cooling tower A, and use an amine solution to capture CO2 in the waste gas; the absorption tower includes a heat exchanger assembly, a backwash section circulating water system, a demister packing layer from top to bottom, a backwash section packing layer and at least one absorption packing layer; the bottom of the absorption tower is connected to the top of the waste gas cooling tower; the heat exchanger assembly exchanges heat with the chemical absorbent through the cold source seawater to keep the temperature of the chemical absorbent in each section of the absorption tower within the optimal reaction temperature range; the backwash section circulating water system includes an overflow liquid collection tray arranged below the backwash section packing layer, which is used to perform overflow water washing on the backwash section packing layer.

[0042] The chemical absorbent inlet device is used to introduce the alcohol amine solution below the backwash section packing layer of the absorption tower and above the absorption packing layer. The chemical absorbent used in the present invention is an alcohol amine solution. In the whole process of carbon capture by the alcohol amine solution, the reaction principle is:

[0043] Alcohol amine solution + low concentration CO2 in waste gas → rich amine solution + purified waste gas (emptying) ↑

[0044] Rich amine solution + heat source → alcohol amine solution + high concentration CO2↑

[0045] For example, the chemical absorbent is monoethanolamine (MEA).

[0046] The reaction of MEA absorbing CO2 is: According to Le Chatelier's Principle, temperature increase will cause the reaction equilibrium to move in the reverse direction, which is not conducive to the formation of products; that is, temperature increase will reduce the solubility of CO2 in the chemical absorbent, thereby reducing the amount of CO2 absorbed. Other alcohol amine absorbents also have the problem of heat release during the absorption process. The process of MEA absorbing CO2 is an exothermic reaction, and the heat released is about 70-100kJ / mol CO2, which will cause the system temperature to rise significantly during the absorption process.

[0047] The absorption tower includes at least one layer of absorption filler layer, as a specific embodiment, such as Figure 1 As shown, the absorption tower includes a first absorption filler layer and a second absorption filler layer. In actual engineering design, the absorption filler layer can be further refined and divided into multiple sections to accurately control the process parameters of the absorption process.

[0048] like Figure 1 As shown, the chemical absorbent enters the device, and the amine solution (stream 5' and / or stream 5) enters the absorption tower B from above the first absorption packing layer of the absorption tower B and below the backwashing section packing layer, that is, between the backwashing section packing layer and the first absorption packing layer.

[0049] In the present invention, after the alcohol amine solution absorbs CO2, a rich amine solution is formed. After the rich amine solution is heated, high-concentration CO2 is released, and the alcohol amine solution is regenerated for recycling. Usually, the heating of the rich amine solution is carried out in the desorption tower, and the alcohol amine solution is regenerated at the bottom of the desorption tower, and then the alcohol amine solution (stream 5) from the bottom of the desorption tower is introduced into the absorption tower B. The lean amine solution at the bottom of the desorption tower is in a high-temperature state, and after heat exchange with the rich amine solution (stream 4) at the bottom of the absorption tower in a low-temperature state, it continues to be circulated as an absorbent.

[0050] The feed gas of absorption tower B is the ship engine exhaust gas (stream 2) cooled by the exhaust gas cooling tower, and the chemical absorbent is an amine solution; the chemical absorbent forms a uniform liquid film on the filler surface of the absorption filler layer to absorb CO2 in the ship engine exhaust gas.

[0051] Absorption tower B is in the form of a packed tower, with gas and liquid in reverse contact, feed gas enters the tower body from the bottom of the tower, and the chemical absorbent drips downward into the absorption packing layer.

[0052] The absorption tower B also includes a liquid level control system and an absorbent replenishing device. The liquid level control system monitors the liquid level signals of each section. When the liquid level is too low, the solution circulation pump is stopped, and when the liquid level is too high, the frequency of the circulation pump is increased. The absorbent replenishing device monitors the concentration of the rich amine solution in the absorption tower. When it is lower than a preset minimum value, fresh alcoholamine solution is replenished to the absorption tower, and when it is higher than a preset maximum value, deionized water is replenished to the absorption tower.

[0053] A specific operation mode of the absorbent replenishing device is as follows: make-up water (stream 6') comes from the replenishment fresh water (deionized water) tank and enters the absorbent tower from the top of the absorbent tower; the exhaust gas of the absorbent tower will take away part of the water in the shipboard carbon capture system during the absorption of carbon dioxide by the chemical absorbent. In order to ensure that the concentration of the absorbent recycled in the system is maintained at the design value (for example, the concentration of MEA chemical absorbent is 40wt.%), the reaction balance of the absorption and desorption reaction process is not destroyed, and the operation burden of the system liquid circuit is not caused. For example, the viscosity will usually increase when the concentration of the chemical absorbent increases. Control logic of make-up water (stream 6'): the replenishment method of make-up water is to replenish in small doses through the diaphragm pump P-B01, and the replenishment amount is controlled by the concentration sensor (CT: concentration transmitter, CIC: concentration indication control) at the bottom of the absorbent tower. The concentration sensor is in the form of a refractometer. When the concentration of the rich amine solution is higher than the preset maximum value, for example, the concentration of the MEA chemical absorbent is 43wt.%, the metering pump is activated to pump deionized water in small amounts and multiple times. When the concentration sensor shows that the MEA concentration is close to 40wt.%, the pump is stopped.

[0054] The chemical absorbent (stream 5) in the system circulation comes from the alcohol amine solution after the thermal decomposition of the rich amine solution in the desorber, and usually passes through the heat exchanger for the lean and rich amine solution for heat exchange. Before the chemical absorbent enters the absorber, fresh chemical absorbent (stream 5') will be added according to the actual operation situation. The fresh chemical absorbent is added in small doses through the diaphragm pump P-B02. The amount of addition is controlled by the concentration sensor at the bottom of the absorber (CT: concentration transmitter, CIC: concentration indication control). The concentration sensor is in the form of a refractometer. When the concentration of the rich amine solution is lower than the preset minimum value, the metering pump is activated to pump in small amounts and multiple times. For example, when the concentration of the MEA chemical absorbent is 36wt.%, the metering pump is activated to pump in small amounts and multiple times fresh MEA chemical absorbent (40wt.%). When the concentration sensor shows that the MEA concentration reaches 40wt.%, the pump is stopped.

[0055] A specific operation mode of the liquid level control system is as follows: an overflow liquid collection tray is provided under the first absorption packing layer, and the absorbent reacts by flowing into the packing in the form of overflow; when the liquid level sensor (LT: liquid level transmitter, LIC: liquid level indication control) alarms low, the first chemical absorbent circulation pump P-B04 is stopped to prevent the liquid from being emptied, and when the liquid level signal recovers to above the middle liquid level, the operation is resumed. An overflow liquid collection tray is provided under the second absorption packing layer, and the absorbent reacts by flowing into the packing in the form of overflow; when the liquid level sensor (LT: liquid level transmitter, LIC: liquid level indication control) alarms low, the second chemical absorbent circulation pump P-B05 is stopped to prevent the liquid from being emptied, and when the liquid level signal recovers to above the middle liquid level, the operation is resumed. The rich amine solution pump P-B06 at the bottom of the tower usually runs at a fixed frequency during normal operation of the equipment. When the exhaust gas treatment capacity of the equipment fluctuates and the liquid collection plate fluctuates significantly, when the liquid level signal is high, increase the frequency of pump P-B06; when the liquid level signal is low, stop pump P-B06.

[0056] like Figure 1 As shown, the heat exchanger assembly includes a chemical absorbent entering section heat exchanger E-B02, a backwash section heat exchanger E-B01, a first absorption section heat exchanger E-B03 and a second absorption section heat exchanger E-B04.

[0057] In order to reduce the escape of amines in the exhaust gas at the outlet of the absorber, the solutes in the amine solution, especially MEA, are easily soluble in water, so a backwash section packing layer is set before the outlet of the absorber. During the backwash process, the reaction heat of the absorption process and the exhaust heat will accumulate during the operation of the system, and the above-mentioned make-up water (stream 6') enters the backwash section packing layer by overflow, so an overflow liquid collection tray is set below the backwash section packing layer; the backwash water is always circulated, and a sufficient amount of seawater (stream 7") is pumped in to allow part of the seawater to flow through the heat exchanger E-B01, and the other part of the seawater is directly discharged overboard through the bypass of the electrically regulated three-way valve V-B01. The opening of the bypass valve is controlled by the temperature signal (TT: temperature transmitter, TI: temperature indication / signal) before the backwash water enters the backwash section packing layer. Pump P-B03 pumps the backwash water in the overflow liquid collection tray set below the backwash section packing layer into the heat exchanger E-B01 for heat exchange treatment, and then enters the backwash section packing layer after heat exchange treatment. A temperature monitoring device is set on the pipeline from the heat exchanger to the absorption tower to obtain the temperature signal of the backwash water after heat exchange treatment.

[0058] A demister packing layer is arranged above the backwash section packing layer. The demister packing layer reduces the saturated water discharged from the top of the tower along with the gas phase, maintains the water balance of the system, and reduces the supplement of deionized water. At the same time, because the alcohol amine solute is easily soluble in water, the amine escape is reduced.

[0059] In order to ensure the stability of the absorption temperature in the absorption tower, an additional temperature control loop is set in this patent, and sufficient seawater (stream 7') is pumped into the system, so that part of the seawater flows through the chemical absorbent and enters the heat exchanger E-B02, while the other part of the seawater is directly discharged overboard through the three-way valve V-B02 of the electric regulating valve opening bypass. The opening of the bypass valve is controlled by the temperature signal (TT: temperature transmitter, TI: temperature indication / signal) before the amine solution enters the absorption tower, and the flow of seawater (heat exchanger cold inlet) entering the heat exchanger is adjusted, and the excess cold inlet (seawater) is directly discharged.

[0060] In order to ensure the stability of the absorption temperature in the absorption tower, the system is also equipped with a first absorption section heat exchanger E-B03. The temperature signal of the chemical absorbent entering the tower during the reaction process is used to control the opening of the cold seawater inlet valve V-B03 (stream 7”) of the first absorption section heat exchanger E-B03, and adjust the seawater flow entering the heat exchanger. The excess cold seawater is directly discharged overboard. Pump P-B04 pumps the chemical absorbent in the liquid collection tray below the first absorption packing layer into the heat exchanger E-B03 for heat exchange treatment, and then enters the first absorption packing layer after heat exchange treatment. A temperature monitoring device is set on the pipeline from the heat exchanger to the absorption tower to obtain the temperature signal of the chemical absorbent after heat exchange treatment.

[0061] In order to ensure the temperature stability of the absorption reaction process in the absorption tower, the system is also equipped with a second absorption section heat exchanger E-B04. The temperature signal of the chemical absorbent entering the tower during the reaction process is used to control the opening of the cold seawater inlet valve V-B04 of the second absorption section heat exchanger E-B04 (stream 7") to adjust the seawater flow entering the heat exchanger, and the excess cold seawater is directly discharged overboard. Pump P-B05 pumps the chemical absorbent in the liquid collection tray below the second absorption packing layer into the heat exchanger E-B04 for heat exchange treatment, and then enters the second absorption packing layer after heat exchange treatment. A temperature monitoring device is set on the pipeline from the heat exchanger to the absorption tower to obtain the temperature signal of the chemical absorbent after heat exchange treatment.

[0062] Example 1

[0063] Taking a specific engineering case as an example, the amount of ship engine exhaust gas treated is 60000Nm3 / h, the exhaust gas temperature is 200℃, the pressure is 1.3bar(a), the CO2 volume fraction in the exhaust gas is 5vol.%, and MEA is used as the absorbent. The exhaust temperature of the exhaust gas cooling tower A is set at 40℃, and the exhaust gas is cooled by direct spraying of deionized water. The temperature operating range is 35-45℃. The exhaust gas temperature within this temperature range is more conducive to the subsequent absorption reaction. The deionized water circulation volume of pump P-A01 is 180m 3 / h, head 60m; the upper limit of heat exchange capacity of heat exchanger E-A01 is 3700kW, during the heat exchange process, hot inlet is 51℃, hot outlet is 36℃, cold inlet is 32℃, cold outlet is 46℃, and the seawater demand (stream 7) is 220m 3 / h@4bar(g); The opening of valve V-A01 is usually 80% (80% into the main channel, 20% discharged overboard), and its opening is adjusted with the temperature fluctuation of stream 2; stream 6, the replenishment amount of deionized water is 3.2t / h.

[0064] The absorption tower B can realize isothermal absorption process in the above control, and the temperature in the tower is controlled at 40-45°C during the absorption process to ensure the best reaction kinetics during the absorption process. The chemical absorbent is MEA, the absorbent concentration is 40wt.%, and the circulation rate is 120t / h.

[0065] Stream 6', when the system is in stable operation, the amount of deionized water added is 1.8 t / h;

[0066] Backwash tower circulating cooling water, pump P-B03 circulation volume is 110m 3 / h, head 30m; the upper limit of heat exchange capacity of heat exchanger E-B01 is 500kW, during heat exchange, hot inlet is 42℃, hot outlet is 38℃, cold inlet is 32℃, cold outlet is 36℃, and seawater demand (stream 7") is 110m 3 / h@4bar(g); The opening of valve V-B01 is usually 70%, and its opening is adjusted according to the temperature fluctuation of the circulating cooling water returning to the tower;

[0067] Stream 5, MEA circulation volume is 120t / h, head 60m; the replenishment of fresh amine liquid stream 5', under the stable operation of the system, the replenishment volume is 1.2kg / h, head 60m. The upper limit of heat exchange of heat exchanger E-B02 is 270kW. During the heat exchange process, the hot inlet is 42℃, the hot outlet is 40℃, the cold inlet is 32℃, the cold outlet is 34℃, and the seawater demand (stream 7') is 120m 3 / h@4bar(g); The opening of valve V-B01 is usually 90%, and its opening is adjusted according to the temperature fluctuation of the amine solution entering the tower. The amine solution entering the tower is set at 40°C;

[0068] Used for circulating cooling of chemical absorbent in the first absorption packing layer, the upper limit of cooling capacity is 430kW. The circulation capacity of pump P-B04 is 48m 3 / h, head 20m; the upper limit of heat exchange of heat exchanger E-B03 is 430kW, during the heat exchange process, hot inlet is 45℃, hot outlet is 38℃, cold inlet is 32℃, cold outlet is 39℃, and the seawater demand (stream 7”') is 55m 3 / h@4bar(g); The opening of valve V-B01 is usually 85%, and its opening is adjusted according to the temperature fluctuation of the circulating alcohol amine solution back to the tower;

[0069] The circulating cooling of the chemical absorbent in the second absorption packing layer has an upper limit of 470kW. The circulating capacity of pump P-B05 is 82m 3 / h, head 20m; the upper limit of heat exchange capacity of heat exchanger E-B04 is 470kW, during heat exchange, hot inlet is 45℃, hot outlet is 40℃, cold inlet is 32℃, cold outlet is 38℃, seawater demand (stream 7””) is 83m3 / h@4bar(g); the opening of valve V-B01 is usually 90%, and its opening is adjusted according to the temperature fluctuation of circulating alcohol amine solution returning to the tower;

[0070] Rich amine solution pump P-B06, 124.8t / h, head 60m.

[0071] The system processes 60,000 Nm of exhaust gas from ship engines. 3 / h, achieving a carbon capture efficiency of 81% and a CO2 capture capacity of 4803.1kg / h. The shipboard carbon capture system using this temperature control solution processes 60,000Nm of exhaust gas from ship engines. 3 / h, the carbon capture efficiency can reach 81%, and the CO2 capture capacity is 4803.1kg / h. Compared with the scheme without temperature control, the absorbent is 120t / h MEA (40wt.%), the exhaust gas treatment capacity is 60000Nm 3 / h(CO2 5vol%) In the absence of isothermal control, the absorption efficiency will be reduced. Due to the running time and the temperature in the system, the cumulative absorption efficiency can only be maintained between 50% and 70%.

Claims

1. A shipboard carbon capture system, which uses a chemical absorption method to capture carbon, characterized in that: The system comprises: An exhaust gas inlet device for introducing exhaust gas from the ship's engine into the exhaust gas cooling tower; An exhaust gas cooling tower, the exhaust gas cooling tower comprises a deionized water circulation system, a first heat exchanger and a deionized water replenishment system, wherein: the circulating water in the deionized water circulation system sprays the exhaust gas, then exchanges heat with cold source seawater through the first heat exchanger for cooling, and then circulates back to spray the exhaust gas; the exhaust gas outlet temperature is controlled by adjusting the flow of seawater entering the first heat exchanger to keep the exhaust gas within the optimal reaction temperature range of the chemical absorbent; the deionized water replenishment system automatically replenishes the deionized water reduced due to the water vapor carried away by the exhaust gas according to the liquid level signal in the tower; The absorption tower is used to receive the waste gas after cooling from the waste gas cooling tower, and use an alcohol amine solution to capture CO2 in the waste gas; the absorption tower includes a heat exchanger assembly, a backwash section circulating water system, a demister packing layer from top to bottom, a backwash section packing layer and at least one absorption packing layer; the bottom of the absorption tower is connected to the top of the waste gas cooling tower; the heat exchanger assembly exchanges heat with the chemical absorbent through the cold source seawater to keep the temperature of the chemical absorbent in each section of the absorption tower within the optimal reaction temperature range; the backwash section circulating water system includes an overflow liquid collection tray arranged below the backwash section packing layer, which is used to perform overflow water washing on the backwash section packing layer; The chemical absorbent inlet device is used to introduce the alcohol amine solution into the lower part of the backwash section packing layer of the absorption tower and is located above the absorption packing layer.

2. The system according to claim 1, characterized in that The heat exchanger assembly includes a plurality of independently controlled heat exchangers, which adjust the seawater flow entering each heat exchanger according to the chemical absorbent temperature signal of different areas in the absorption tower, so as to achieve accurate control of the temperature of the chemical absorbent in each section of the absorption tower.

3. The system according to claim 2, characterized in that The heat exchanger assembly includes a chemical absorbent inlet section heat exchanger, a backwash section heat exchanger, and an absorption section heat exchanger; the seawater flow rate of the first heat exchanger is controlled by a temperature signal of exhaust gas discharged from an exhaust gas cooling tower, and is achieved by adjusting the valve opening of a seawater flow regulating valve in the first heat exchanger; the chemical absorbent inlet section heat exchanger adjusts the seawater flow rate entering the heat exchanger according to a temperature signal before the chemical absorbent enters the absorption tower; the backwash section heat exchanger adjusts the seawater flow rate entering the heat exchanger according to a temperature signal before the circulating water enters the backwash section packing layer; the absorption section heat exchanger adjusts the seawater flow rate entering the heat exchanger according to a temperature signal of the chemical absorbent in the tower.

4. The system according to claim 2, characterized in that The absorption tower also includes a liquid level control system and an absorbent replenishing device. The liquid level control system monitors the liquid level signals of each section. When the liquid level is too low, the solution circulation pump is stopped, and when the liquid level is too high, the frequency of the circulation pump is increased. The absorbent replenishing device monitors the concentration of the rich amine solution in the absorption tower. When it is lower than a preset minimum value, fresh alcoholamine solution is replenished into the absorption tower, and when it is higher than a preset maximum value, deionized water is replenished into the absorption tower.

5. A method for controlling the temperature of an absorption process of a shipboard carbon capture system, the method being applied to a shipboard carbon capture system that uses a chemical absorption method for carbon capture, the system comprising an exhaust gas cooling tower and an absorption tower, characterized in that: The method comprises the following steps: a. Introduce the exhaust gas of the ship engine into the exhaust gas cooling tower; b. In the exhaust gas cooling tower, the circulating water is used to spray the exhaust gas, which is then cooled by heat exchange with the cold source seawater in the first heat exchanger and then circulated back to spray the exhaust gas; according to the temperature signal of the exhaust gas discharged from the exhaust gas cooling tower, the flow rate of seawater entering the first heat exchanger is adjusted to control the exhaust gas outlet temperature to remain within the optimal reaction temperature range of the chemical absorbent; at the same time, according to the liquid level signal in the tower, the deionized water that is reduced due to the exhaust gas taking away water vapor is automatically supplemented; c. The waste gas cooled by the waste gas cooling tower is introduced into the absorption tower, and the alcohol amine solution is introduced below the backwash section packing layer of the absorption tower and above the absorption packing layer. The alcohol amine solution is used in the absorption tower to capture the CO2 in the waste gas; in the absorption tower, the chemical absorbent is heat exchanged through the heat exchanger assembly to maintain the temperature of the chemical absorbent in each section of the absorption tower within the optimal reaction temperature range; at the same time, the backwash section packing layer is overflow-washed.

6. The method according to claim 5, characterized in that In step b, the seawater flow rate of the first heat exchanger is controlled by a temperature signal of the exhaust gas discharged from the exhaust gas cooling tower, and is achieved by adjusting the valve opening of the seawater flow regulating valve in the first heat exchanger.

7. The method according to claim 5, characterized in that The heat exchanger assembly in step c includes a plurality of independently controlled heat exchangers, and the seawater flow entering each heat exchanger is adjusted according to the temperature signal of the chemical absorbent in different areas of the absorption tower to achieve precise control of the temperature of the chemical absorbent in each section of the absorption tower.

8. The method according to claim 7, characterized in that The heat exchanger assembly comprises a chemical absorbent inlet section heat exchanger, a backwash section heat exchanger and an absorption section heat exchanger, and each heat exchanger independently adjusts the incoming seawater flow rate.

9. The method according to any one of claims 5 to 8, characterized in that The method also includes replenishing fresh alcoholamine solution to the absorption tower when the concentration of the rich amine solution in the absorption tower is lower than a preset minimum value, and replenishing deionized water to the absorption tower when the concentration of the rich amine solution in the absorption tower is higher than a preset maximum value.

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