A dual-fuel engine supply system and control method using BOG

Abstract

The object of the present invention is to provide a dual-fuel engine supply system and control method using BOG, which includes a dual-fuel engine, an LNG supply system, a BOG cold energy utilization system, a BOG combustion system, an ethanol reforming hydrogen production system, and an intake system; the LNG supply system includes a storage tank, a pressure sensor, a submersible pump, valves, a heat exchanger, and a buffer tank; the BOG cold energy utilization system includes valves, a heat exchanger, a compressor, and an expander; the BOG combustion system includes a dual-fuel engine, a generator, a storage battery, and electrical equipment; the ethanol reforming hydrogen production system includes an ethanol storage tank, valves, a high-temperature reaction furnace, and a hydrogen storage tank; the intake system includes a mixer, a turbine, and a compressor. The present invention can process the surplus BOG and utilize its cold energy and chemical energy; at the same time, using the heat of the exhaust gas after BOG combustion, reform ethanol to obtain hydrogen, and mix it with natural gas to inhibit the misfire and knocking phenomena of the dual-fuel engine.

Description

Technical Field

[0001] The present invention relates to a dual-fuel engine system and a control method, specifically to a fuel supply system and a control method for a dual-fuel engine. Background Art

[0002] Currently, with the increasingly deteriorating global environment and the decreasing petroleum reserves, in order to improve the global environment and cope with the energy crisis, people have turned their attention to LNG. LNG has become the preferred fuel to replace traditional petroleum fuels due to its high energy density, rich reserves, low sulfur content, and relatively small air pollution caused by complete combustion.

[0003] On LNG carriers, due to the large storage tanks in their supply systems, a large amount of BOG is generated during transportation due to heat absorption and evaporation from the environment, which increases the pressure in the LNG storage tank. When the pressure in the tank is higher than the safety value, the BOG in the tank must be discharged. Directly discharging BOG into the atmosphere will cause problems such as energy waste and environmental pollution, and there are also safety hazards; at the same time, the operating boundary of the dual-fuel engine is relatively narrow, and phenomena such as misfire and knock are likely to occur.

[0004] To solve the above problems, a BOG treatment device is provided to effectively utilize the excess cold energy and chemical energy of BOG; a scholar proposed adding hydrogen to natural gas and using the fast combustion speed of hydrogen to strengthen combustion, prevent misfire in the dual-fuel engine, and achieve clean combustion while suppressing knock.

[0005] Bioethanol, as a renewable energy source, can produce a mixture containing hydrogen and carbon monoxide through certain catalytic reactions, which is used to assist the combustion of the dual-fuel engine. Summary of the Invention

[0006] The purpose of the present invention is to provide a dual-fuel engine fuel supply system and a control method that can solve problems such as excessive BOG in the storage tank of the dual-fuel engine supply system and unstable air-fuel ratio of the dual-fuel engine, which may cause misfire or knock in the engine.

[0007] The purpose of the present invention is achieved as follows:

[0008] A dual-fuel engine supply system using BOG according to the present invention is characterized in that it includes a storage tank, a buffer tank, a first dual-fuel engine, a second dual-fuel engine, an ethanol storage tank, a hydrogen storage tank, a first to third heat exchanger, and a first to second mixer. The storage tank is connected to the first heat exchanger through a first valve, the first heat exchanger is connected to the first mixer, the first mixer is connected to the first dual-fuel engine, the storage tank is connected to the first compressor through a second valve, the first compressor is connected to the second heat exchanger, the second heat exchanger is connected to the second mixer, and the second mixer is connected to the second dual-fuel engine. The exhaust gas of the second fuel engine enters the third heat exchanger through a turbine, and the third heat exchanger is respectively connected to the second compressor and the expander. The second heat exchanger is respectively connected to the second compressor and the expander. The ethanol storage tank is connected to a high-temperature reaction furnace through a third valve, the high-temperature reaction furnace is connected to the hydrogen storage tank, and the outlet of the hydrogen storage tank branches out a first mixing pipeline and a second mixing pipeline respectively. The first mixing pipeline is connected to the first mixer, and the second mixing pipeline is connected to the second mixer. A fourth valve is installed on the first mixing pipeline, and a fifth valve is installed on the second mixing pipeline.

[0009] A dual-fuel engine supply system using BOG according to the present invention may further include:

[0010] 1. A pressure sensor is installed in the storage tank.

[0011] A control method for a dual-fuel engine supply system using BOG according to the present invention is characterized in that when the LNG carrier is operating and the pressure measured by the pressure sensor in the storage tank is lower than the set value, the LNG in the storage tank flows into the first heat exchanger through the first valve, exchanges heat with the water glycol solution, and the obtained gas enters the buffer tank, and then flows into the first mixer to be mixed with air and a hydrogen-carbon monoxide mixture, and enters the first dual-fuel engine for combustion.

[0012] A control method for a dual-fuel engine supply system using BOG according to the present invention may further include:

[0013] 1. When the LNG carrier is not operating and the pressure measured by the pressure sensor in the storage tank is greater than the set value, the BOG in the storage tank enters the second heat exchanger through the second valve and the first compressor, exchanges heat with nitrogen, and the obtained gas enters the second dual-fuel engine for combustion and drives a generator to generate electricity. At the same time, the engine exhaust gas is respectively introduced into the turbine to drive the compressor to work, and then enters the third heat exchanger to complete the Brayton cycle. The output work of the expander drives the generator to charge the battery, and at the same time, the battery supplies power to the second compressor, the electric resistance heater, and other electrical equipment; at the same time, the electric resistance heater in the high-temperature reaction furnace generates heat, increasing the temperature of the high-temperature reaction furnace, causing the ethanol in the ethanol storage tank to react to obtain a hydrogen-carbon monoxide mixture, which is introduced into the hydrogen storage tank, and then into the second mixer to be mixed with the gas and air, and finally enters the second dual-fuel engine.

[0014] 2. When the LNG carrier is not operating and the pressure sensor in the storage tank measures a pressure lower than the set value, stop working.

[0015] 3. When the LNG carrier is operating and the pressure sensor in the storage tank measures a pressure greater than the set value, the LNG in the storage tank flows into the first heat exchanger through the first valve, exchanges heat with the water glycol solution, and the resulting gas enters the buffer tank, then flows into the first mixer to mix with air and a hydrogen-carbon monoxide mixture, and enters the first dual-fuel engine for combustion; the BOG in the storage tank enters the second heat exchanger through the second valve and the first compressor, exchanges heat with nitrogen, and the resulting gas enters the second dual-fuel engine for combustion, driving a generator to generate electricity. At the same time, the engine exhaust gas is divided into a turbine to drive the compressor to work, and then enters the third heat exchanger to complete the Brayton cycle. The output work of the expander drives the generator to charge the battery, and at the same time, the battery supplies power to the second compressor, the electric resistor, and other electrical equipment; at the same time, the electric resistor of the high-temperature reactor generates heat, increasing the temperature of the high-temperature reactor, causing the ethanol in the ethanol storage tank to react to obtain a hydrogen-carbon monoxide mixture, which is then introduced into the hydrogen storage tank, and then into the first mixer and the second mixer to mix with gas and air, and finally enters the first dual-fuel engine and the second dual-fuel engine.

[0016] The advantages of the present invention are as follows: It can effectively utilize the cold energy and chemical energy of BOG, avoid energy waste, reduce risks, be safer, and use the waste gas energy generated by BOG combustion to catalytically reform ethanol to obtain a hydrogen-carbon monoxide mixture, which is introduced into the engine, effectively suppressing the misfire and knocking phenomenon of the dual-fuel engine and achieving efficient and clean combustion. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic structural diagram of the present invention;

[0018] Figure 2 is a schematic diagram of four control modes. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention will be described in more detail with reference to the accompanying drawings as follows:

[0020] Combined with Figure 1-2 , a dual-fuel engine supply system and control method using BOG according to the present invention includes a dual-fuel engine 8, an LNG supply system, a BOG cold energy utilization system, a BOG combustion system, an ethanol reforming hydrogen production system, and an intake system.

[0021] The LNG supply system includes a storage tank 1, a pressure sensor 21, a submersible pump 20, valves 2, a heat exchanger 3, and a buffer tank 4; the BOG cold energy utilization system includes valves 22, heat exchangers 18, 24, compressors 19, 25, and an expander 23; the BOG combustion system includes a dual-fuel engine 16, a generator 28, a storage battery 29, and electrical equipment 30; the ethanol reforming hydrogen production system includes an ethanol storage tank 9, valves 10, 13, 15, a high-temperature reaction furnace 11, an electric resistance 14, and a hydrogen storage tank 12; the intake system includes mixers 5, 17, turbines 7, 27, a compressor 6, 26.

[0022] The BOG cold energy utilization system can utilize the cold energy of the BOG in the storage tank 1 and the waste gas energy of the dual-fuel engine in the BOG combustion system, complete the Brayton cycle through the compressor 25 and the expander 23, and convert the work done by the expander 23 into electrical energy through the generator 28 and store it in the storage battery 29.

[0023] The BOG combustion system can pass the gas heated by the heat exchanger 18 into the dual-fuel engine 16 for combustion, drive the generator 28 to generate electricity by the dual-fuel engine 16, and store it in the storage battery 29. During system operation, the storage battery 29 supplies power to the compressor 25, the electric resistance, and other electrical equipment 30.

[0024] The ethanol reforming hydrogen production system can supply power to the electric resistance 14 by using the storage battery 29 in the BOG combustion system to create high-temperature conditions, place catalysts such as CuO / ZnO / Al2O3 in the high-temperature reaction furnace 11, ethanol enters the high-temperature reaction furnace 11 through the storage tank 9, undergoes catalytic reforming to produce hydrogen, and is passed into the hydrogen storage tank 12. When needed, the valve 13 is opened, and hydrogen is transported to the mixer 5 to be mixed with gas and air and then transported to the dual-fuel engine 8 to avoid misfire and knocking phenomena in the engine.

[0025] The control method of the present invention:

[0026] When the LNG carrier is operating and the pressure measured by the pressure sensor 21 in the storage tank 1 is greater than the set value, all systems start to work at this time. The LNG in the storage tank 1 flows through the valve 2 into the heat exchanger 3, exchanges heat with the water-ethylene glycol solution, and the gas with appropriate temperature enters the buffer tank 4, and then flows into the mixer 5 to mix with the air, hydrogen-carbon monoxide mixture, enters the dual-fuel engine 8, burns, and the exhaust gas enters the turbine 7 to drive the compressor 6 to work. The BOG in the storage tank 1 enters the heat exchanger 18 through the valve 22 and the compressor 19, exchanges heat with nitrogen, and the gas with appropriate temperature and pressure enters the dual-fuel engine 16 to burn, and drives the generator 28 to generate electricity. At the same time, the engine exhaust gas is divided into the turbine 27 to drive the compressor 26 to work, and then enters the heat exchanger 24 to complete the Brayton cycle. And the expander 23 outputs work to drive the generator 28 to charge the battery 29. At the same time, the battery 29 supplies power to the compressor 25, the electric resistance heater 14 and other electrical equipment 30; at the same time, the electric resistance heater 14 generates heat, which raises the temperature of the high-temperature reaction furnace 11, causes the ethanol in the ethanol storage tank 9 to react, obtains a hydrogen-carbon monoxide mixture, and passes it into the hydrogen storage tank 12, and then passes it into the mixer 17 and 5 to mix with the gas and air, and finally enters the dual-fuel engines 8 and 16.

[0027] When the LNG carrier is operating and the pressure measured by the pressure sensor 21 in the storage tank 1 is lower than the set value, only the LNG supply system and the dual-fuel engine 8 work at this time. The LNG in the storage tank 1 flows through the valve 2 into the heat exchanger 3, exchanges heat with the water-ethylene glycol solution, and the gas with appropriate temperature enters the buffer tank 4, and then flows into the mixer 5 to mix with the air, hydrogen-carbon monoxide mixture, enters the dual-fuel engine 8, burns, and the exhaust gas enters the turbine 7 to drive the compressor 6 to work.

[0028] When the LNG carrier is not operating and the pressure measured by the pressure sensor 21 in the storage tank 1 is greater than the set value, in addition to the LNG supply system and the dual-fuel engine 8, all systems work. The BOG in the storage tank 1 enters the heat exchanger 18 through the valve 22 and the compressor 19, exchanges heat with nitrogen, and the gas with appropriate temperature and pressure enters the dual-fuel engine 16 to burn, and drives the generator 28 to generate electricity. At the same time, the engine exhaust gas is divided into the turbine 27 to drive the compressor 26 to work, and then enters the heat exchanger 24 to complete the Brayton cycle. And the expander 23 outputs work to drive the generator 28 to charge the battery 29. At the same time, the battery 29 supplies power to the compressor 25, the electric resistance heater 14 and other electrical equipment 30; at the same time, the electric resistance heater 14 generates heat, which raises the temperature of the high-temperature reaction furnace 11, causes the ethanol in the ethanol storage tank 9 to react, obtains a hydrogen-carbon monoxide mixture, and passes it into the hydrogen storage tank 12, and then passes it into the mixer 17 to mix with the gas and air, and finally enters the dual-fuel engine 16.

[0029] When the LNG carrier is not operating and the pressure sensor 21 in the storage tank 1 measures that the pressure is lower than the set value, all systems do not work at this time.

Claims

1. A dual-fuel engine supply system using BOG, characterized in that: It includes a storage tank, a buffer tank, a first dual-fuel engine, a second dual-fuel engine, an ethanol storage tank, a hydrogen storage tank, a first heat exchanger, a second heat exchanger, a third heat exchanger, a first mixer, and a second mixer. The storage tank is connected to the first heat exchanger through a first valve. The first heat exchanger is connected to the first mixer. The first mixer is connected to the first dual-fuel engine. The storage tank is connected to a first compressor through a second valve. The first compressor is connected to the second heat exchanger. The second heat exchanger is connected to the second mixer. The second mixer is connected to the second dual-fuel engine. The exhaust gas of the second fuel engine enters the third heat exchanger through a turbine. The third heat exchanger is respectively connected to a second compressor and an expander. The second heat exchanger is respectively connected to the second compressor and the expander. The ethanol storage tank is connected to a high-temperature reaction furnace through a third valve. The high-temperature reaction furnace is connected to the hydrogen storage tank. The outlet of the hydrogen storage tank branches out into a first mixing pipeline and a second mixing pipeline. The first mixing pipeline is connected to the first mixer. The second mixing pipeline is connected to the second mixer. A fourth valve is installed on the first mixing pipeline. A fifth valve is installed on the second mixing pipeline; When the LNG carrier is operating and the pressure sensor in the storage tank measures that the pressure is lower than the set value, the LNG in the storage tank flows into the first heat exchanger through the first valve, exchanges heat with the water glycol solution, and the obtained gas enters the buffer tank, and then flows into the first mixer to mix with air and a hydrogen-carbon monoxide mixture, and enters the first dual-fuel engine for combustion; When the LNG carrier is operating and the pressure sensor in the storage tank measures that the pressure is greater than the set value, the LNG in the storage tank flows into the first heat exchanger through the first valve, exchanges heat with the water glycol solution, and the obtained gas enters the buffer tank, and then flows into the first mixer to mix with air and a hydrogen-carbon monoxide mixture, and enters the first dual-fuel engine for combustion; The BOG in the storage tank enters the second heat exchanger through the second valve and the first compressor, exchanges heat with nitrogen, and the obtained gas enters the second dual-fuel engine for combustion and drives a generator to generate electricity. At the same time, the engine exhaust gas is respectively introduced into the turbine to drive the compressor to work, and then is introduced into the third heat exchanger to complete the Brayton cycle. The expander outputs work to drive the generator to charge the battery, and at the same time the battery supplies power to the second compressor, the electric resistance heater and other electrical equipment; At the same time, the electric resistance heater of the high-temperature reaction furnace generates heat, increasing the temperature of the high-temperature reaction furnace, causing the ethanol in the ethanol storage tank to react to obtain a hydrogen-carbon monoxide mixture, which is introduced into the hydrogen storage tank, and then introduced into the first mixer and the second mixer to mix with gas and air, and finally enters the first dual-fuel engine and the second dual-fuel engine; When the LNG carrier is not in operation and the pressure sensor in the storage tank measures a pressure greater than the set value, the BOG in the storage tank enters the second heat exchanger through the second valve and the first compressor, exchanges heat with nitrogen, and the resulting gas enters the second dual-fuel engine for combustion, driving a generator to generate electricity. At the same time, the engine exhaust gas is divided to drive the compressor through the turbine, and then enters the third heat exchanger to complete the Brayton cycle. The output work of the expander drives the generator to charge the battery, and at the same time, the battery supplies power to the second compressor, the electric resistor, and other electrical equipment. At the same time, the electric resistor in the high-temperature reactor generates heat, increasing the temperature of the high-temperature reactor, causing the ethanol in the ethanol storage tank to react, producing a hydrogen-carbon monoxide mixture, which is then introduced into the hydrogen storage tank and then into the second mixer to be mixed with the gas and air, and finally enters the second dual-fuel engine. When the LNG carrier is not in operation and the pressure sensor in the storage tank measures a pressure lower than the set value, the operation stops.

2. The dual-fuel engine supply system using BOG according to claim 1, characterized in that: A pressure sensor is installed in the storage tank.

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