Temperature control method for desorption process of shipborne carbon capture system

Abstract

The invention provides a desorption temperature control method of a shipborne carbon capture system, which is suitable for an alcohol amine solution chemical absorption method and is used for controlling a pump and a valve in a desorption process of the shipborne carbon capture system. The system comprises a desorption tower unit and a gas-liquid separation unit of the shipborne carbon capture system, and the process control of a temperature characteristic value in the CO2 desorption process of the shipborne carbon capture system is realized through linkage control among main equipment, so that the efficiency of a rich amine solution in the CO2 desorption process is improved, the control precision is improved, and the safe and stable operation of the system is ensured.

Description

Technical Field

[0001] The present invention relates to the technical fields of ship emission control and ship carbon capture, and in particular to a temperature control method for a desorption process of a shipboard carbon capture system. Background Art

[0002] Under the urgent need of global climate change and environmental protection, the International Maritime Organization (IMO) actively promotes the low-carbon and zero-carbon transformation of ship energy, aiming to reduce greenhouse gas emissions from the shipping industry. However, new alternative fuels still have problems such as limited carbon reduction capacity, insufficient supply of green fuels, and difficulty in combustion control. Therefore, most of the current energy demand is still met by fossil fuels. A large amount of greenhouse gases (Greenhouse Gases) will be emitted during the combustion of fossil fuels, which has many adverse effects on climate change.

[0003] In order to meet this challenge, shipboard carbon capture technology, as an effective means of negative emissions, has received increasing attention from the industry. This technology mainly relies on chemical absorption, which efficiently captures CO2 in flue gas through specific absorbents (such as amine solutions). It has the advantages of fast absorption rate, large absorption capacity and relatively low desorption energy consumption. In the desorption stage of the carbon capture process, precise control of the desorption temperature is crucial to improving desorption efficiency and reducing energy consumption. Unfortunately, however, there is currently a lack of specialized patented technology for the application of amine solution chemical absorption in shipboard carbon capture systems, especially in the control of desorption temperature.

[0004] In view of the limitations of existing technologies, it is particularly important to develop a method for controlling the temperature of the desorption process of a shipboard carbon capture system. This method aims to overcome the shortcomings of existing technologies and achieve efficient and energy-saving CO2 capture and desorption processes by precisely controlling the desorption temperature, thereby providing strong technical support for the low-carbon transformation of ship energy and helping the global shipping industry achieve green and sustainable development. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a desorption temperature control method for a shipboard carbon capture system suitable for an alcohol amine solution chemical absorption method, which is beneficial to improving the controllability of the system, improving the desorption efficiency, and reducing the desorption energy consumption.

[0006] The technical solution of the present invention is as follows:

[0007] A shipboard carbon capture system for an alcohol amine solution chemical absorption method, characterized in that it includes:

[0008] Engine exhaust treatment module, used to treat exhaust gas discharged from the engine, including SCR reactor and EGC system;

[0009] An absorption tower, arranged after the engine exhaust treatment module, is used to receive the treated exhaust gas and spray an alcohol amine solution from the top to absorb CO2 in the exhaust gas;

[0010] A backwash tower, connected to the absorption tower, for flushing the tail gas after absorbing CO2;

[0011] The rich liquid desorption module comprises a desorption tower B and a desorption tower A, wherein the desorption tower B is used for preliminarily desorbing the rich liquid after absorbing CO2, and the desorption tower A is used for further desorbing the semi-lean liquid from the desorption tower B, and a reboiler is provided in the middle section of the desorption tower A to heat the semi-lean liquid;

[0012] The lean liquid circulation and replenishment module includes a lean amine liquid delivery pump and a lean amine liquid storage tank, which are used to circulate the lean liquid after complete desorption back to the absorption tower and replenish new lean amine liquid as needed;

[0013] The CO2 capture and storage module includes a gas-liquid separation tank, a buffer tank, a compressor and a liquefaction device, which are used to process the desorbed CO2 gas and store it in liquid form.

[0014] Furthermore, it also includes:

[0015] A rich amine liquid delivery pump and a lean amine liquid cooler are arranged before the rich liquid desorption module and are used to deliver and cool the rich liquid after absorbing CO2;

[0016] A semi-lean amine liquid circulation pump and a semi-lean amine liquid-lean amine liquid heat exchanger are arranged between desorption tower B and desorption tower A, and are used for circulating and exchanging heat of the semi-lean amine liquid;

[0017] The acid gas cooler is installed before the gas-liquid separation tank to cool the desorbed CO2 gas.

[0018] The present invention also provides a desorption temperature control method for the above-mentioned ship-borne carbon capture system, which is characterized in that it includes:

[0019] According to the liquid level signal at the bottom of desorption tower B, the frequency of semi-lean amine liquid circulation pump P-B01 and the opening of valve V-B01 are adjusted;

[0020] The frequency of the lean amine liquid circulation pump P-A01 is adjusted according to the liquid level signal at the bottom of desorption tower A, and the opening of the inlet valve of the thermal oil heating system and the flow rate of the thermal oil are adjusted according to the temperature signal at the top of desorption tower A;

[0021] The reboiler is heated by a thermal oil heating system, and the heating system is controlled by the temperature signal at the top of the desorption tower A;

[0022] The opening of the cooling water flow control valve is adjusted according to the temperature signal, the opening and closing of the stop valve V-E01 at the outlet of the gas-liquid separation tank is controlled according to the pressure signal, and the opening and closing of the stop valve entering the top of the desorption tower B is controlled according to the liquid level signal.

[0023] Further, in the liquid level control step of the desorption tower B, when the liquid level is low, the frequency of the semi-lean amine liquid circulation pump is reduced and the opening of the valve V-B01 is reduced to prevent emptying; when the liquid level is high, the frequency is increased and the opening is increased;

[0024] In the temperature control step of the desorption tower A, the frequency of the thermal oil pump is reduced and the opening of the valve V-D01 is reduced when the temperature increases, and the frequency is increased and the opening is increased when the temperature decreases.

[0025] Furthermore, it also includes the control of backwash tower flushing water circulation, lean amine liquid effective component concentration monitoring and replenishment, and CO2 gas compression and liquefaction.

[0026] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0027] 1) The present invention ensures efficient absorption and flushing of CO2 in tail gas by optimizing the design of the absorption tower and the backwash tower, and effectively improves the capture rate of CO2. The coordinated use of desorption tower B and desorption tower A in the rich liquid desorption module and the heating effect of the reboiler enable the CO2 in the rich liquid to be fully desorbed, further improving the capture efficiency.

[0028] 2) The application of multi-parameter control systems such as liquid level, temperature and pressure ensures the stable operation of the shipboard carbon capture system under different working conditions. Through the precise desorption temperature control method, the desorption efficiency reduction or system failure caused by temperature fluctuations is effectively avoided, and the overall reliability of the system is improved. By optimizing the desorption process, energy consumption and heat loss are reduced, and the operating cost of the system is reduced. After compression and liquefaction, the captured CO2 gas can be stored in a CO2 storage tank, which provides the possibility for subsequent use, such as industrial production, geological storage, etc., thereby realizing the recycling of resources and energy conservation and emission reduction.

[0029] 3) It can effectively improve control efficiency, enhance control accuracy, and ensure system safety and stable operation. The design is simple and reasonable, easy to operate, and can effectively utilize the original control signal of the system to reduce the complexity of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the main partitions of a ship-borne carbon capture system for an alcohol amine solution chemical absorption method according to an embodiment of the present invention;

[0031] Figure 2 It is a schematic diagram of the temperature control scheme of the desorption process of the shipboard carbon capture system;

[0032] In the figure, 01 is the engine; 02 is the SCR reactor; 03 is the induced draft fan; 04 is the EGC; 05 is the EGC pump; 06 is the water treatment system; 07 is the absorption tower; 08 is the backwash tower; 09 is the flushing water delivery pump; 10 is the backwash circulation pump; 11 is the rich amine liquid delivery pump; 12 is the lean amine liquid cooler; 13 is the lean amine liquid precision filter; 14 is the desorption tower A; 15 is the reboiler; 16 is the desorption tower B; 17 is the semi-lean amine liquid-lean amine liquid heat exchanger; 18 is the semi-lean amine liquid circulation pump; 19 is the lean amine liquid delivery pump; 20 is the amine liquid The conveying pump is as follows: 21 is a lean amine liquid storage tank; 22 is a gas-liquid separation tank; 23 is a gas-liquid separation tank reflux pump; 24 is a buffer tank; 25 is a compressor; 26 is a liquefaction equipment; H is a thermal oil heating system, E is an acid gas cooler, P is an oil injection pump, V1, V3, V4, and V5 are stop valves, V2 is a three-way valve, stream 1 is a rich amine solution, stream 2 is a circulating cooling water inlet of the acid gas cooler, stream 2' is a circulating cooling water return of the acid gas cooler, stream 3 is a CO2 gas outlet of the gas-liquid separation tank, and stream 4 is a lean amine solution. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments, but this should not limit the protection scope of the present invention.

[0034] This embodiment provides a shipboard carbon capture system for alcohol amine solution chemical absorption method and a desorption temperature control method thereof, aiming to improve system efficiency and overcome the limitations of the prior art. The system starts with the exhaust gas treatment of the engine 01. The exhaust gas first passes through the SCR reactor 02 to remove NOx, and then is washed by the EGC system 04 to remove particulate matter and other pollutants. The treated exhaust gas finally enters the shipboard carbon capture system.

[0035] System overview Figure 1 As shown:

[0036] Tail gas absorption stage: Tail gas enters from the bottom of absorption tower 07 and contacts with the alcohol amine solution sprayed from the top in reverse direction to achieve efficient absorption of CO2. The tail gas after absorption is flushed by backwash tower 08 and discharged, and the flushing water is circulated back to absorption tower 07 through flushing water delivery pump 09.

[0037] Rich liquid desorption stage: The rich liquid (stream 1) after absorbing CO2 enters the desorption tower B16 for preliminary desorption after passing through the rich amine liquid delivery pump 11 and the lean amine liquid cooler 12. The semi-lean liquid after desorption passes through the semi-lean amine liquid circulation pump 18 and the semi-lean amine liquid-lean amine liquid heat exchanger 17, and enters the desorption tower A14 for deep desorption. The middle section of the desorption tower A is equipped with a reboiler 15 to promote the full desorption of the semi-lean liquid by heating.

[0038] Lean liquid circulation and replenishment: The completely desorbed lean liquid is returned to the absorption tower 07 via the lean amine liquid delivery pump 19 and the heat exchanger 11. New liquid is replenished from the lean amine liquid storage tank 21 in due time according to the concentration of the effective components of the lean amine liquid.

[0039] CO2 capture and storage: The CO2 gas discharged from the desorption tower B is processed by the gas-liquid separation tank 22, the buffer tank 24, the compressor 25 and the liquefaction equipment 26, and then stored in the CO2 storage tank.

[0040] Desorption temperature control method, such as Figure 2 As shown:

[0041] Liquid level control of desorption tower B: The semi-lean amine liquid circulation pump 18 usually runs at a fixed frequency. When the liquid level at the bottom of desorption tower B is low, the frequency of 18 is reduced and the opening of valve V4 is reduced to prevent emptying; when the liquid level is high, the frequency is increased and the opening is increased.

[0042] Liquid level and temperature control of desorption tower A: The lean amine liquid circulation pump 19 also mainly operates at a fixed frequency. When the liquid level is low, the frequency of 19 is reduced, and when it is high, it is increased. For temperature control, the temperature signal at the top of desorption tower A is used to adjust the opening of the inlet valve V5 of the thermal oil heating system and the flow rate of thermal oil, which is achieved by adjusting the frequency of the thermal oil pump P.

[0043] Reboiler heating control: The reboiler is heated by a thermal oil heating system, and the heating system is controlled by the temperature signal at the top of the desorption tower A to ensure a stable and efficient desorption process.

[0044] Gas-liquid separation and cooling control: The desorbed gas is cooled by the acid gas cooler E and enters the gas-liquid separation tank 22. The temperature, pressure and liquid level are precisely controlled by adjusting the cooling water flow (using the three-way valve V2) and the bypass discharge, as well as controlling the stop valve V3 entering the desorption tower B. Specifically, the opening of the bypass valve V2 is adjusted according to the temperature signal, the opening and closing of V1 is controlled according to the pressure signal, and the opening and closing of V3 is controlled according to the liquid level signal to ensure stable operation of the system.

[0045] Example:

[0046] The amount of ship engine exhaust gas treated is 60000Nm 3 / h, the exhaust gas temperature is 200℃, the pressure is 1.3bar(a), the volume fraction of CO2 in the exhaust gas is 5vol.%, and an amine solution is used as the absorbent.

[0047] The absorbent (rich amine solution, stream 1) from the absorption tower enters the desorption tower B16. The desorption tower is in the form of a packed tower with reverse gas-liquid contact. The rich amine solution pours down into the packing layer from the upper end of the second packing layer. The gas discharged after desorption in the desorption tower A14 enters the tower body from the bottom of the tower. The amine liquid after desorption from stream 1 enters the desorption tower B, passes through the semi-lean amine liquid circulation pump 18 at the bottom of the tower, and then passes through the lean and rich amine liquid heat exchanger 17 for heat exchange and enters the desorption tower A. The temperature of the rich amine solution from the absorption tower is 106°C, the amine liquid circulation volume is 120t / h, and the head is 60m. The temperature of the desorption tower B is controlled at 105-110°C during the desorption process. The absorbent is an alcohol amine solution with an alcohol amine concentration of 40wt.%. The circulation volume of the semi-lean amine liquid circulation pump is 120t / h, and the head is 60m. The upper limit of the heat exchange capacity of the lean and rich amine liquid heat exchanger is 270kW. During the heat exchange process, the hot inlet is 124℃, the hot outlet is 109℃, the cold inlet is 105℃, and the cold outlet is 119℃. The opening of valve V4 is usually 90%, and its opening is adjusted with the liquid level at the bottom of desorption tower B.

[0048] After the semi-lean amine liquid enters the desorption tower A, it pours down into the packing layer from the top of the desorption tower A. The lean amine solution after desorbing CO2 passes through the lean amine liquid delivery pump 19, and after heat exchange through the lean and rich amine liquid heat exchanger, it enters the absorption tower (stream 4). The temperature of the desorption tower A during the desorption process is controlled at 118-124°C. After heating and desorption, the semi-lean liquid passes through the lean and rich amine liquid heat exchanger and returns to the absorption tower. The circulation capacity of the lean amine liquid delivery pump is 120t / h, and the head is 60m.

[0049] When the semi-lean amine liquid enters the desorption tower A, part of the liquid enters the reboiler 15 to vaporize and form secondary steam, and forms a gas phase reflux in the tower. The reboiler is heated by the thermal oil heating system H. The power upper limit of the reboiler is 500kW, the temperature of the liquid entering the reboiler is 123℃, and the temperature of the steam leaving the reboiler is 124℃. The reboiler is provided with heat by the thermal oil, and the circulation volume of the oil injection pump P is 160m 3 / h, head 40m, the opening of valve V5 is usually 90%, and the frequency of the oil injection pump and the opening of the valve are adjusted according to the temperature signal at the top of the desorption tower A.

[0050] After the desorbed gas is discharged from the top of the desorber B, it is cooled by the acid gas cooler E and then enters the gas-liquid separation tank 22. The gas-liquid separation tank separates the gaseous CO2 from the alcohol amine solution, and the separated alcohol amine solution is sent back to the desorber through the gas-liquid separation tank reflux pump 23. The separated CO2 is discharged after passing through the stop valve V1. The upper limit of the heat exchange of the acid gas cooler is 270kW. During the heat exchange process, the hot inlet is 94℃, the hot outlet is 45℃, the cold inlet is 25℃, and the cold outlet is 45℃. The cooling water demand (stream 2) is 220m 3 / h@4bar(g); The opening of valve V2 is usually 80% (80% enters the main road, 20% is discharged overboard), and its opening is adjusted according to the fluctuation of the temperature signal of the heat output. The temperature of the amine liquid after separation in the gas-liquid separation tank is 45°C, the circulation volume of the gas-liquid separation tank reflux pump is 12t / h, the head is 40m, and the opening of valve V3 is usually 90%, and its opening is adjusted according to the liquid level height at the bottom of the gas-liquid separation tank. The separated CO2 is discharged through valve V1, and the opening of valve V1 is usually 90%, and its opening is adjusted according to the pressure intensity signal at the top of desorption tower B.

Claims

1. A ship-borne carbon capture system for alcohol amine solution chemical absorption method, characterized in that: include: An engine exhaust gas treatment module, used for treating exhaust gas discharged from an engine (01), comprising an SCR reactor (02) and an EGC system (04); An absorption tower (07), arranged after the engine exhaust treatment module, is used to receive the treated exhaust gas and spray an amine solution from the top to absorb CO2 in the exhaust gas; A backwash tower (08), connected to the absorption tower (07), for flushing the tail gas after absorbing CO2; A rich liquid desorption module comprises a desorption tower B (16) and a desorption tower A (14), wherein the desorption tower B (16) is used for preliminarily desorbing the rich liquid after absorbing CO2, and the desorption tower A (14) is used for further desorbing the semi-lean liquid from the desorption tower B (16), and a reboiler (15) is provided in the middle section of the desorption tower A (14) to heat the semi-lean liquid; A lean liquid circulation and replenishment module, comprising a lean amine liquid delivery pump (19) and a lean amine liquid storage tank (21), is used to circulate the lean liquid after complete desorption back to the absorption tower (07) and replenish new lean amine liquid as needed; The CO2 capture and storage module comprises a gas-liquid separation tank (22), a buffer tank (24), a compressor (25) and a liquefaction device (26), and is used to process the desorbed CO2 gas and store it in liquid form.

2. The shipborne carbon capture system for alcohol amine solution chemical absorption method according to claim 1, characterized in that: Also includes: A rich amine liquid delivery pump (11) and a lean amine liquid cooler (12) are arranged before the rich liquid desorption module and are used to deliver and cool the rich liquid after absorbing CO2; A semi-lean amine liquid circulation pump and a semi-lean amine liquid-lean amine liquid heat exchanger are arranged between the desorption tower B (16) and the desorption tower A (14) for circulating and exchanging heat of the semi-lean amine liquid; The acid gas cooler is arranged before the gas-liquid separation tank (22) and is used to cool the desorbed CO2 gas.

3. A desorption temperature control method for the shipboard carbon capture system according to claim 1 or 2, characterized in that: include: According to the liquid level signal at the bottom of the desorption tower B (16), the frequency of the semi-lean amine liquid circulation pump (P-B01) and the opening of the valve V-B01 are adjusted; The frequency of the lean amine liquid circulation pump (P-A01) is adjusted according to the liquid level signal at the bottom of the desorption tower A (14), and the opening of the inlet valve (V-D01) of the thermal oil heating system and the flow rate of the thermal oil are adjusted according to the temperature signal at the top of the desorption tower A (14); The reboiler (15) is heated by a heat transfer oil heating system, and the heating system is controlled by a temperature signal at the top of the desorption tower A (14); The opening of the cooling water flow control valve is adjusted according to the temperature signal, the opening and closing of the stop valve V-E01 at the outlet of the gas-liquid separation tank (22) is controlled according to the pressure signal, and the opening and closing of the stop valve entering the top of the desorption tower B (16) is controlled according to the liquid level signal.

4. The desorption temperature control method according to claim 3, characterized in that: In the liquid level control step of the desorption tower B (16), when the liquid level is low, the frequency of the semi-lean amine liquid circulation pump is reduced and the opening of the valve V-B01 is reduced to prevent emptying; when the liquid level is high, the frequency is increased and the opening is increased; In the temperature control step of the desorption tower A (14), the frequency of the thermal oil pump is reduced and the opening of the valve V-D01 is reduced when the temperature rises, and the frequency is increased and the opening is increased when the temperature drops.

5. The desorption temperature control method according to claim 3 or 4, characterized in that: It also includes the control of the backwash tower (08) flushing water circulation, the monitoring and replenishment of the effective component concentration of the lean amine liquid, and the compression and liquefaction of CO2 gas.

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