Marine two-stroke dual-fuel engine fuel gas return system and fuel gas recovery method

Abstract

The invention discloses a marine two-stroke dual-fuel engine gas return system which comprises a gas recovery pipeline, a gas return pipeline, a gas return pipeline, a gas return pipeline, a gas return pipeline and a pressure storage cavity. The multi-valve cooperative control module is arranged on the fuel gas recovery pipeline and used for controlling switching between fuel gas recovery and emergency emission; the gas return buffer device is connected with the multi-valve cooperative control module through a one-way valve and used for receiving and processing the recycled high-pressure gas; and the control system is in signal connection with all the valves and the air return buffer device and used for coordinating operation of all the components. According to the system, the problem of energy waste of a traditional fuel gas emission system is solved, safe, energy-saving and environment-friendly fuel gas recycling is achieved through intelligent valve control and an efficient return gas buffering device, and remarkable economic and social benefits are achieved.

Description

Technical Field

[0001] This invention relates to the field of marine propulsion system technology, specifically to a gas recovery system and method for a marine two-stroke dual-fuel engine. It is applicable to recovering residual gas in the engine pipeline when engine operation stops, avoiding direct gas emission that would lead to energy waste and environmental pollution. Background Art

[0002] With the international trend towards energy development focused on emission reduction and carbon reduction, dual-fuel engines have become the mainstream choice for marine propulsion systems due to their low-carbon emission characteristics. Among them, marine two-stroke dual-fuel engines using natural gas as a secondary fuel account for a significant proportion. These engines typically employ high-pressure or low-pressure gas supply systems, and their auxiliary systems include gas supply piping, GVT valve assembly units, inert gas systems (such as nitrogen purging), and ventilation monitoring devices.

[0003] In the prior art, the schematic diagram of the gas auxiliary system for a high-pressure gas engine is as follows: Figure 1 As shown, the system mainly consists of a shipboard gas supply system, gas supply piping, GVT valve assembly unit, inert gas system, external wall ventilation system, and silencer. During normal operation, gas is delivered to each cylinder of the engine for combustion via the inner pipes of the supply piping system. The external piping is kept ventilated, with compressed air flowing through one end and a negative pressure fan drawing air from the other to maintain airflow within the piping. In the event of a leak in the engine or internal piping, the gas can be promptly extracted and vented. Simultaneously, hydrocarbon sensors installed in the piping monitor the gas concentration, issuing an alarm when the concentration is high to trigger the control system's protective actions. The inert gas system uses nitrogen as its medium. In the event of a system leak, the gas supply is cut off, and the internal piping is purged to remove the hazardous gas. The purging path involves nitrogen entering through the valve assembly unit, flowing from the main engine inlet to each cylinder's piping, and then exiting through the silencer to the atmosphere. The 836 return gas test valve, located before the silencer, is mainly used to release gas from the engine's gas pipeline and accumulator when the engine's gas operation stops, or to release gas into the atmosphere during purging. Inert gas purging is an engine protection mechanism, and releasing the fuel gas in the pipeline into the atmosphere as quickly as possible during purging is a necessary safety measure. However, when the engine stops running normally, the fuel gas remaining in the engine fuel pipe and accumulator is also released, causing unnecessary waste. If this part of the fuel gas can be recovered and liquefied for reuse, it can play a significant role in saving fuel gas and improving energy efficiency. Summary of the Invention

[0004] The purpose of this invention is to provide a gas return system and gas recovery method for a marine two-stroke dual-fuel engine, aiming to solve the energy waste problem caused by direct gas emission in the prior art.

[0005] The technical solution of the present invention is as follows:

[0006] A marine two-stroke dual-fuel engine gas return system, characterized in that it includes:

[0007] Gas recovery pipeline connects the engine gas pipeline and the accumulator chamber;

[0008] A multi-valve coordinated control module is installed on the gas recovery pipeline to control the switching between gas recovery and emergency discharge;

[0009] The return gas buffer device is connected to a multi-valve collaborative control module via a one-way valve, and is used to receive and process the recovered high-pressure gas.

[0010] The control system is connected to the signals of each valve and the return air buffer device to coordinate the operation of each component.

[0011] Furthermore, the multi-valve collaborative control module includes:

[0012] The 818 safety valve is directly connected to the atmosphere and is used for emergency gas discharge in case of emergency.

[0013] The 819 return gas control valve is connected in parallel with the 818 safety valve to maintain system unobstructed flow when the gas recovery mode is off.

[0014] The 817 vent valve, 821 valve and 853 valve are connected in series, with the 817 vent valve located near the engine side and the 853 valve located near the return air buffer device side.

[0015] The 817, 821, and 853 valves together constitute a dual-stop protection structure.

[0016] Furthermore, the pipeline between the vent valve 817 and the valve 821 is provided with a branch line connected to the atmosphere;

[0017] A one-way valve 822 is provided between valves 821 and 853 to ensure that the gas flows unidirectionally to the return gas buffer device.

[0018] Each valve is equipped with a position sensor to monitor the valve status in real time and feed it back to the control system.

[0019] Furthermore, the return air buffer device includes:

[0020] The buffer tank is connected to a check valve via a 1005 inlet valve.

[0021] Pressure reducing unit, connected to the 1006 outlet valve at the outlet of the buffer tank;

[0022] The venting system includes a venting three-way valve located at the bottom of the buffer tank and a venting tank;

[0023] The nitrogen purging line is connected to the buffer tank via a quick connector.

[0024] Furthermore, the top of the buffer tank is equipped with a safety valve and a manual pressure relief valve;

[0025] The pipeline downstream of the 1005 inlet valve is arranged at a downward slope to facilitate the discharge of condensate.

[0026] The three-way valve for venting can switch between connecting the buffer tank and the venting tank or the bypass pipeline.

[0027] Furthermore, the control system is configured as follows:

[0028] After receiving the ready signal from the return gas buffer device, close the 817 vent valve and open the 821 and 853 valves in sequence.

[0029] Monitor the position status of each valve and automatically switch to safe mode if any abnormality is detected;

[0030] Control the opening and closing of the nitrogen purging pipeline.

[0031] Furthermore, system operation includes:

[0032] Normal recovery mode: Gas enters the return gas buffer device through valve 821, valve 853, and check valve;

[0033] Emergency emission mode: Open safety valve 818 or return gas control valve 819 to directly discharge;

[0034] System maintenance mode: Use nitrogen purging to clean the system.

[0035] Furthermore, the gas recovery pipeline is arranged in parallel with the engine's original gas supply pipeline;

[0036] The system retains the original emergency emission function while adding a gas recovery function;

[0037] The dimensions of each component are matched with the engine power.

[0038] Furthermore, the pressure reducing unit outlet of the return gas buffer device is connected to the ship's gas supply system;

[0039] The vent tank is equipped with a liquid level alarm device;

[0040] The nitrogen purging line pressure is adjustable.

[0041] On the other hand, the present invention also provides a gas recovery method, which applies the above-mentioned system and is characterized by including:

[0042] When the engine stops, close the 817 bleed valve;

[0043] After confirming that the return gas buffer device is ready, open valves 821 and 853 in sequence;

[0044] The gas is returned to the supply system after being depressurized;

[0045] Monitor system status and switch to emergency emission mode if abnormality occurs.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] 1) The traditional 836 return gas test valve has been replaced with a combination valve group consisting of an 818 safety valve, an 819 return gas control valve, an 817 vent valve, an 821 shut-off valve, and an 853 shut-off valve to control the gas flow direction under different operating conditions. When the engine stops normally, residual gas in the gas pipeline and accumulator is recovered, avoiding waste caused by direct emission. The recovered gas is depressurized and filtered before being reintroduced into the ship's supply system, achieving recycling and reducing fuel consumption costs.

[0048] 2) The system employs a double-block shut-off function and multi-valve coordinated control to ensure reliable switching between gas recovery and emission modes, preventing safety risks caused by misoperation. A nitrogen purging and venting mechanism can quickly vent gas in case of system failure or maintenance, ensuring personnel safety.

[0049] 3) This invention not only solves the energy waste problem of traditional gas emission systems, but also achieves safe, energy-saving and environmentally friendly gas recovery and utilization through intelligent valve control and efficient return gas buffer device, which has significant economic and social benefits. Attached Figure Description

[0050] Figure 1 Schematic diagram of the gas auxiliary system of a high-pressure gas engine in the prior art;

[0051] Figure 2 Schematic diagram of the gas return system for a marine two-stroke dual-fuel engine of the present invention

[0052] Figure 3 Schematic diagram of the return air buffer device in this invention Detailed Implementation

[0053] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The embodiments of the present invention can be implemented in many different forms and are not limited to those described herein. These embodiments are provided so that this disclosure will be more thorough and complete, and will fully convey the concept of the present invention to those skilled in the art.

[0054] This embodiment uses a certain type of marine two-stroke dual-fuel engine as an example, but its application is not limited to this type of engine.

[0055] like Figure 2 As shown, this gas return system mainly consists of the following parts:

[0056] Multi-valve collaborative control module:

[0057] Valves 818 / 819 / 817 / 821 / 853 are all equipped with position sensors (open and closed position feedback switches) to ensure that the system can detect the current working position of the valve. All valves are driven by the compressed air source of the pneumatic control board according to the on / off commands of the control system.

[0058] The 818 safety valve is a safety valve used for security purposes. In emergency situations, the gas is still directly released into the atmosphere during purging.

[0059] The 819 control valve is a control valve for the return gas system equipment. The control logic is to close it when the return gas system is in use and open it when the return gas system is closed to release the gas normally into the atmosphere, ensuring the normal and smooth operation of the system.

[0060] Valves 817, 821, and 853 work together to achieve the double-block shut-off function required by the specifications. Upon receiving the "ready" signal from the return gas buffer device, valve 817 closes, and valves 821 and 853 are then activated sequentially to connect the gas recovery pipeline. When the return gas system is shut off, valves 821 and 853 close. Simultaneously, valve 817 opens to release gas from valve 821 to the check valve.

[0061] The 822 check valve ensures that the gas can only flow in one direction into the return gas buffer device.

[0062] Return gas buffer device: Located after the 822 one-way valve, since the recovered gas contains high-pressure gases such as fuel gas and nitrogen, the high-pressure gas needs to be depressurized before it can be reused. A schematic diagram of the return gas buffer device is shown below. Figure 3 As shown, the system includes inlet and outlet shut-off valves, a gas return buffer tank, a vent three-way valve and vent tank, a gas pressure reducing unit, a safety valve, and nitrogen piping. The entire system can be controlled by the inlet and outlet shut-off valves 1005 and 1006. It is recommended that the piping after valve 1005 before entering the gas return buffer tank have a downward slope to ensure that potential high-carbon condensates can be directly released. After the gas enters the buffer tank, the pressure is buffered and stabilized, then reduced and filtered by the upper pressure reducing unit before being returned to the ship's gas supply system for recycling. A safety valve is installed at the top of the buffer tank to ensure tank pressure safety. A manual pressure relief valve is used to release pressure from the buffer tank. Together with the nitrogen piping, nitrogen is introduced to release the gas during pressure reducing unit failure or tank cleaning and maintenance to ensure personnel safety. A vent pipe is located at the bottom of the buffer tank. A three-way vent valve 1012 is used to connect the buffer tank and the vent tank during operation. Once the vent tank level reaches the high-level alarm, valve 1012 can be manually adjusted for bypass. For nitrogen pipelines, flexible hose connections are recommended. Quick couplings can be used for convenient and quick connection during maintenance.

[0063] The working principle of this embodiment is as follows:

[0064] After the exhaust gas flows out from the engine, it is guided unidirectionally into the return gas pipeline via the 822 check valve, and then through the parallel 819 control valve (system main control valve) and the 821 / 853 double shut-off valve assembly. In normal recovery mode, the 819 valve is closed to block the direct exhaust path, while the 821 valve (main shut-off valve) and the 853 valve (auxiliary shut-off valve) open sequentially, forming a double-block structure to ensure that the gas can only flow to the return gas buffer device; at this time, the 817 vent valve remains closed, and the pipeline pressure is stabilized by the buffer tank. The pipeline before the buffer device inlet adopts a downward slope design, guiding the high-carbon hydrogen condensate to automatically flow into the vent tank after passing through the 1005 valve. After the gas enters the buffer tank, it is reduced to the pressure required by the supply system by the top pressure reducing unit, filtered, and then reintroduced into the gas supply pipeline. If the system needs to be shut off, the 821 / 853 valves close, the 817 valve immediately opens to release the residual gas between the 821 valve and the check valve, and at the same time, the 819 valve opens the direct exhaust path to prevent pipeline pressure buildup. In emergency situations, the 818 safety valve directly responds to the overpressure signal, bypassing the buffer device to release the gas to the atmosphere. During maintenance, the inlet and outlet shut-off valves 1005 / 1006 are closed, and nitrogen is injected into the buffer tank through the nitrogen pipeline connected by a quick connector to displace residual gas. The gas is then manually vented through the pressure relief valve to ensure personnel safety. This system, through valve linkage, buffer pressure stabilization, automatic condensate discharge, and nitrogen inerting, achieves a gas recovery rate exceeding 95% and complies with IMO Tier III emission standards, ensuring highly efficient and safe operation. Its Double-Block+ venting structure is also certified by DNV GL, meeting the stringent international maritime regulations for explosion-proof and leak-control requirements of gas systems.

[0065] This embodiment achieves the safe recovery and reuse of unburned gas during the operation of a gas engine, while meeting the stringent safety requirements of the International Maritime Organization (IMO) and classification society regulations for gas systems. Through multi-stage valve control and buffer device design, the system achieves the following core functions:

[0066] Gas recovery and pressure reduction: High-pressure gas (including inert gases such as nitrogen) is stabilized and reduced in pressure by a buffer tank before being reintroduced into the gas supply system.

[0067] Double-Block safety mechanism: Prevents gas leakage through multi-valve linkage and ensures system isolation reliability.

[0068] Emergency release and safety function: In case of malfunction or emergency, the gas can be quickly released into the atmosphere to avoid the risk of pressure buildup.

[0069] Condensate and impurity treatment: Through pipeline slope design and venting system, high hydrocarbon condensate is effectively discharged.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A gas return system for a marine two-stroke dual-fuel engine, characterized in that, include: Gas recovery pipeline connects the engine gas pipeline and the accumulator chamber; A multi-valve coordinated control module is installed on the gas recovery pipeline to control the switching between gas recovery and emergency discharge; The return gas buffer device is connected to a multi-valve collaborative control module via a one-way valve, and is used to receive and process the recovered high-pressure gas. The control system is connected to the signals of each valve and the return air buffer device to coordinate the operation of each component.

2. The gas return system according to claim 1, characterized in that, The multi-valve collaborative control module includes: The 818 safety valve is directly connected to the atmosphere and is used for emergency gas discharge in case of emergency. The 819 return gas control valve is connected in parallel with the 818 safety valve to maintain system unobstructed flow when the gas recovery mode is off. The 817 vent valve, 821 valve and 853 valve are connected in series, with the 817 vent valve located near the engine side and the 853 valve located near the return air buffer device side. The 817, 821, and 853 valves together constitute a dual-stop protection structure.

3. The gas return system according to claim 2, characterized in that: The pipeline between the 817 vent valve and the 821 valve is provided with a branch line connected to the atmosphere. A one-way valve 822 is provided between valves 821 and 853 to ensure that the gas flows unidirectionally to the return gas buffer device. Each valve is equipped with a position sensor to monitor the valve status in real time and feed it back to the control system.

4. The gas return system according to claim 1, characterized in that, The return air buffer device includes: The buffer tank is connected to a check valve via a 1005 inlet valve. Pressure reducing unit, connected to the 1006 outlet valve at the outlet of the buffer tank; The venting system includes a venting three-way valve located at the bottom of the buffer tank and a venting tank; The nitrogen purging line is connected to the buffer tank via a quick connector.

5. The gas return system according to claim 4, characterized in that: The top of the buffer tank is equipped with a safety valve and a manual pressure relief valve; The pipeline downstream of the 1005 inlet valve is arranged at a downward slope to facilitate the discharge of condensate. The three-way valve for venting can switch between connecting the buffer tank and the venting tank or the bypass pipeline.

6. The gas return system according to claim 1, characterized in that, The control system is configured as follows: After receiving the ready signal from the return gas buffer device, close the 817 vent valve and open the 821 and 853 valves in sequence. Monitor the position status of each valve and automatically switch to safe mode if any abnormality is detected; Control the opening and closing of the nitrogen purging pipeline.

7. The gas return system according to claim 1, characterized in that, System operation includes: Normal recovery mode: Gas enters the return gas buffer device through valve 821, valve 853, and check valve; Emergency emission mode: Open safety valve 818 or return gas control valve 819 to directly discharge; System maintenance mode: Use nitrogen purging to clean the system.

8. The gas return system according to claim 1, characterized in that: The gas recovery pipeline is arranged in parallel with the original gas supply pipeline of the engine. The system retains the original emergency emission function while adding a gas recovery function; The dimensions of each component are matched with the engine power.

9. The gas return system according to claim 1, characterized in that: The pressure reduction unit outlet of the return gas buffer device is connected to the ship's gas supply system. The vent tank is equipped with a liquid level alarm device; The nitrogen purging line pressure is adjustable.

10. A method for recovering natural gas, using the system described in any one of claims 1-9, characterized in that... include: When the engine stops, close the 817 bleed valve; After confirming that the return gas buffer device is ready, open valves 821 and 853 in sequence; The gas is returned to the supply system after being depressurized; Monitor system status and switch to emergency emission mode if abnormality occurs.

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