CN105569881B - A kind of method for realizing the efficient no pollution operation of liquefied natural gas power engine of boat and ship - Google Patents

Abstract

The invention discloses a method for realizing high-efficiency and zero-pollution operation of a liquefied natural gas powered ship engine. , the exhaust from the combustion chamber of the engine passes through the waste heat recovery device and the seawater precooler to recover waste heat; part of the exhaust after the waste heat is recovered enters the main channel, and the other part enters the bypass at the upstream fulcrum of the bypass channel connected with the main channel channel, and then remove nitrogen and sulfur; the exhaust gas that has been treated for nitrogen and sulfur removal returns to the main channel from the one-way valve at the downstream fulcrum of the bypass channel, and enters the water cooling separation device and the carbon dioxide cooling separation device together with the gas in the main channel. The remaining gas in the gas is argon-based gas, which enters the mixed pressure regulating gas distribution device. The method not only maintains a reasonable combustion speed, but also avoids the formation of nitrogen oxides in the combustion process of the existing engine.

Description

A method for realizing high-efficiency and zero-pollution operation of liquefied natural gas-powered ship engines

technical field

The invention relates to the fields of high-efficiency clean combustion and high-efficiency energy utilization of internal combustion engines, in particular to a method for realizing high-efficiency and zero-pollution operation of liquefied natural gas-powered ship engines.

Background technique

Two-stroke large-scale low-speed diesel engines have the characteristics of low fuel consumption, stable output torque, and low fuel quality requirements, and have been widely used in the three main ocean-going ships (oil tankers, container ships, and bulk carriers). However, with the deterioration of the earth's environment, the International Maritime Organization and many countries have formulated increasingly stringent regulations on marine emissions, and strict regulations on NOx and SOx emissions from ship engines. Compared with diesel or heavy oil, natural gas has lower sulfur content, more complete combustion, and no particulate matter emissions. At the same time, with the continuous development of natural gas mining and use technologies, its application costs continue to decline. LNG is the abbreviation of Liquefied Natural Gas. Liquefied natural gas can significantly increase the volumetric calorific value of natural gas, and solve the problem that compressed natural gas (CNG) is not easy to carry in mobile power devices. With the development of natural gas liquefaction technology, LNG storage and transportation, etc. With the maturity of technology, LNG-powered ships using LNG as fuel for ship engines are developing rapidly.

Substituting natural gas for diesel or heavy oil as fuel for marine engines can reduce SOx and particulate matter emissions, but the reduction of NOx emissions is not obvious, and relevant technologies need to be adopted to meet the requirements of emission regulations. The liquefaction temperature of LNG is -162°C, and it has a cold energy of 231kW h/t. However, the existing LNG-powered ships only use its low temperature for refrigeration, and do not make full use of its cold energy. Today’s ocean-going ships sail, fuel costs account for 50%-70% of the entire ocean-going ship transportation. A 50,000-ton LNG-powered bulk carrier consumes about 50-80 tons of LNG a day. If the thermal efficiency of the ship’s engine is improved, it will It can save a lot of fuel, reduce carbon emissions, and reduce transportation costs.

The title of the invention is "A Method and Device for Recycling LNG Cold Energy for Automobile Zero Emission and Air Conditioning", and the publication number is CN103832244A. The problem of this method is that when using LNG cold energy to cool the exhaust of the engine, there is a lack of protection against combustion. The treatment methods for various pollutants produced have failed to achieve zero pollution of the engine, and have also failed to improve the thermal efficiency of the engine.

The title of the invention is "working gas cycle engine" and the Chinese patent publication number CN101512125 discloses the following content: the engine supplies gas composed of oxygen, hydrogen as fuel and argon as working gas to the combustion chamber. The upstream condensing part condenses the water vapor contained in the exhaust gas into primary condensed water by exchanging heat between the exhaust gas from the combustion chamber and the atmosphere, and uses the gas separated from the primary condensed water as primary condensed water The gas is discharged after separation. The first condensate is stored in the storage tank. The downstream condensing part uses the latent heat of vaporization of the condensed water stored in the water storage tank to further condense the water vapor contained in the gas after the first condensed water is separated into the second condensed water, and convert the water vapor from the first condensed water into the second condensed water. The gas after the second condensed water is separated from the separated gas is discharged, thereby avoiding a significant decrease in the heat capacity ratio of the working gas. The problem with this engine is that hydrogen is used as the engine fuel. Hydrogen is more expensive than natural gas, and the transportation cost is high. It cannot be used on a large scale at this stage. At the same time, this method fails to improve the thermal efficiency of the engine.

The title of the invention is "Hydrogen Engine Using Circulating Working Gas", and the Chinese patent with the publication number CN101389840 discloses the following content: the hydrogen engine supplies hydrogen, oxygen and argon as working gas to the combustion chamber to burn the hydrogen. Through the condenser, the _H2O in the cycle gas discharged from the combustion chamber is separated and removed from the gas. When the concentration of carbon dioxide in the cycle gas is higher than a predetermined concentration, the three-way valve is switched so that the cycle gas flows through the product removal unit (carbon dioxide absorption unit), thereby separating and removing carbon dioxide from the cycle gas. Although compared with the previous patent, this engine adds circulating argon to improve the thermal efficiency of the engine and adds a carbon dioxide removal device, but it does not overcome the problem that hydrogen cannot be used as a large-scale and low-cost fuel at the present stage.

The title of the invention is "A method for producing liquid oxygen and liquid nitrogen by using LNG cold energy air separation", and the Chinese patent publication number 104807289A discloses the following content: the crude nitrogen from the cold box of the air separation tower is passed through the cold box of the main heat exchanger After reheating, the medium-pressure low-temperature nitrogen separated by the confluence gas-liquid separation tank is reheated through the cold box of the circulating heat exchanger, and the reheated low-pressure low-temperature nitrogen is reheated through the cold box of the circulating heat exchanger, and then pressurized by _N2 The pressurized medium-pressure and normal-temperature nitrogen enters the cycle N ₂ booster to pressurize to high-pressure nitrogen; the high-pressure nitrogen is pre-cooled through the cold box of the circulating heat exchanger; High-purity and high-pressure liquid nitrogen is obtained from the bottom of the upper tower of the cold box of the cold energy recovery tower, and the high-pressure liquid nitrogen is throttled by a throttle valve to obtain medium-pressure liquid nitrogen and medium-pressure nitrogen. . The problem with this method is that it does not indicate how to effectively utilize the cold energy of the generated liquid oxygen and liquid nitrogen, nor how to effectively utilize the cold energy of LNG to become natural gas after being utilized.

The title of the invention is "A LNG Cold Energy Release and Gas Supply System for Powered Fishing Boats", and the Chinese patent with the publication number CN104712905A discloses the following content: at least including LNG storage tanks, cold energy absorption heat exchangers, heat exchangers, and cooling agent storage tank, cryogenic pump, fuel temperature regulating heat exchanger, engine cooling water tank, water pump and fuel engine, self-supercharger is installed on one side of the LNG storage tank, and the air temperature vaporizer is installed on the LNG storage tank to absorb and exchange heat with cold energy Between the LNG cold energy absorption heat exchanger, the cold energy release heat exchanger, the brine storage tank, and the cryopump are connected in sequence to form a closed loop; the LNG cold energy absorption heat exchanger is also connected to the fuel temperature adjustment heat exchanger, The fuel temperature-regulating heat exchanger, the engine cooling water tank, and the water pump are connected in sequence to form a closed circuit; the fuel temperature-regulating heat exchanger is also connected to the fuel engine through a fuel pipeline, and a flow meter is arranged on the fuel pipeline. This method uses LNG cold energy to cool the carbon dioxide in the exhaust, and then uses liquid carbon dioxide to cool the fishing boat, but the utilization efficiency of the LNG cold energy is not high, and the emission of pollutants from the fishing boat engine is not reduced.

The title of the invention is "Method and device for preparing liquid carbon dioxide and dry ice by using LNG cold energy", and the Chinese patent with the publication number CN104236252A discloses the following content: LNG is pumped into the tube side of the shell-and-tube heat exchanger. The gasification of LNG in the tube pass releases latent heat, and the low-temperature gas CO ₂ is cooled and liquefied, and then the gasification product of LNG enters the multi-flow plate-fin heat exchanger as a cold source, and the CO ₂ feed gas enters the CO ₂ compressor after cooling At the same time, the output high-pressure and high-temperature CO ₂ is cooled, and the LNG is heated and gasified into normal temperature natural gas at 10-25°C; the cooled CO ₂ enters the shell of the shell-and-tube heat exchanger, and exits from the shell of the shell-and-tube heat exchanger The outflowing liquid _CO2 is divided into two branches, one enters the liquid _CO2 storage tank, and the other enters the dry ice machine to prepare dry ice. The problem with this method is that the temperature of LNG is much lower than that of liquid carbon dioxide. The method of directly using LNG to cool carbon dioxide gas to produce liquid carbon dioxide cannot efficiently utilize the cold energy of LNG. At the same time, the patent only describes the preparation process of liquid carbon dioxide, and does not explain the cooling of LNG. How to effectively use natural gas after it can be utilized.

"Natural Gas and Petroleum" magazine, Volume 31, Issue 3, 2013, disclosed the related device described in the paper "Air Separation Process Utilizing LNG Cold Energy". The content is: the conventional air separation method uses high-pressure air cooling and expansion refrigeration to provide the cooling capacity required by the air separation system. Gas compression requires a large amount of electricity and water. After the low-temperature cold energy of LNG is used in the air separation system, the unit product Energy consumption will be greatly reduced. From a thermodynamic point of view, point out the rationality of the LNG cold energy recycling method, and improve the process of using high-quality low-temperature cold energy of LNG for air separation, in order to reduce air separation while recycling LNG cold energy Power consumption of the system. The existing problem is that it does not indicate how to effectively utilize the cold energy of the generated liquid oxygen and liquid nitrogen, nor how to effectively use the cold energy of LNG to become natural gas after being utilized.

In the third issue of 2003 of "China Ship Repairing" magazine, the waste heat boiler or other devices with similar functions are disclosed in the paper "The Present Situation of Ship Waste Heat Recovery and Application Prospect of Adsorption Refrigeration". The content is the successful application of heat pipe waste heat steam boiler and water heater on ships. The article focuses on the heat pipe steam boiler system for recovering ship exhaust waste heat, air conditioning system for adsorption refrigeration, chilled water system, and ice making system. The problem is that this paper only considers the waste heat recovery of engine exhaust, and does not propose a good treatment method for exhaust pollutants.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, to provide a high-efficiency and zero-pollution operation system for liquefied natural gas-powered ship engines that efficiently utilizes LNG cold energy, recovers waste heat from the exhaust of the engine, and realizes improved engine thermal efficiency and zero pollutant discharge. method.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A method for realizing efficient and zero-pollution operation of a liquefied natural gas-powered ship engine of the present invention comprises the following steps:

(1) The liquefied natural gas flows out of the liquefied natural gas storage tank and is vaporized into natural gas through heat exchange;

(2) The heat exchange temperature of natural gas and oxygen through the seawater preheater reaches 5-10°C; the natural gas after heat exchange enters the mixed pressure regulating gas distribution device through the natural gas pipeline installed with the natural gas flow sensor and the natural gas flow control valve. The oxygen enters the mixed pressure regulating gas distribution device through the oxygen pipeline equipped with oxygen flow sensor and oxygen flow control valve, and the argon gas and oxygen enter the mixed pressure regulating gas distribution device according to the volume ratio of 3.7:1~3.8:1 to become combustion-supporting gas. Natural gas and combustion-supporting gas are mixed in the mixing pressure regulating gas distribution device at a volume ratio of 1:9.45 to 1:9.65, and then sent to the combustion chamber of the engine for combustion. The exhaust main pipe enters the waste heat recovery device and the seawater precooler in turn to recover the waste heat and cool the exhaust to 5-10°C;

(3) Part of the exhaust gas after the waste heat is recovered enters the main channel, and the other part of the exhaust gas enters the bypass channel at the upstream fulcrum of the bypass channel connected to the main channel, and then removes nitrogen in the nitrogen oxides and sulfur oxides removal device The flow control method of the exhaust gas entering the main channel and the bypass channel is as follows: the engine electronic control unit reads the gas flow signal output by the gas flow meter in the exhaust main pipe and compares it with the set value, and then outputs the control signal to the installation The solenoid valve at the upstream fulcrum of the bypass passage, when the exhaust flow is greater than the set value, increase the opening of the solenoid valve to increase the gas flow of the bypass passage; when the exhaust flow is less than the set value, reduce the opening of the solenoid valve degree to reduce the gas flow in the bypass channel;

(4) The exhaust gas treated with nitrogen and sulfur removal returns to the main channel from the one-way valve at the downstream fulcrum of the bypass channel, and enters the water cooling separation device together with the gas in the main channel, so that the water vapor is liquefied and separated from the gas, and then After the carbon dioxide cooling and separation device, the carbon dioxide is separated from the gas in liquid form, and the remaining gas in the exhaust gas is argon-based gas that can participate in recirculation, and enters the mixed pressure regulating gas distribution device, and fresh oxygen and natural gas Mixed, re-enter the combustion chamber of the engine to participate in combustion.

Compared with existing inventions, the present invention has the following two advantages:

First, the mixture of argon and pure oxygen is used as the combustion-supporting gas, which not only maintains a reasonable combustion speed, but also avoids the generation of nitrogen oxides in the combustion process of the existing engine. The exhaust gas of the engine is re-introduced into the intake pipe for circulation after gradient cooling and separation treatment, realizing zero emission of harmful gases from the marine engine.

Second, the isentropic index of argon is higher than that of nitrogen. According to the method of constant oxygen volume fraction, using argon instead of nitrogen to participate in the combustion process in the engine cylinder can increase the theoretical constant volume heating cycle efficiency of the engine by more than 10%. At the same time, the whole scheme provides the ship with a sufficient amount of heat sources of various temperature grades, which greatly reduces the power consumption of the ship's basic devices such as air conditioners, cold storage, water heaters, and steam generators. Although the pure oxygen preparation process requires a certain amount of However, considering the power system and thermal system of the ship comprehensively, it is calculated that the output power of the engine used for the propeller can be reduced from the existing 12% to 4%, realizing the energy saving during the operation of the ship.

Third, the temperature of LNG in the ship's LNG storage tank is -162°C. Before combustion, it needs to be heated and vaporized to room temperature. The cold energy of LNG during the vaporization process can be used to separate air to produce pure oxygen. The existing industrial cryogenic air separation device uses vapor compression refrigeration to achieve cooling, and simultaneously separates and produces liquid nitrogen and liquid oxygen; using the cold energy of LNG can replace part of the vapor compression refrigeration process and reduce the energy consumed in the vapor compression refrigeration process. Electric energy, in addition, the device for producing liquid nitrogen can be omitted, and only the device for producing liquid oxygen can be kept, which simplifies the device and reduces energy consumption on the basis of the original industrial cryogenic air separation principle. After 1kg of LNG is vaporized, 4kg of oxygen is needed to react with it. According to this proportional relationship, using LNG cold energy to produce oxygen, the power consumption is 0.43kW·h/kgO ₂ , which is 0.49kW·h/kgO2 compared with the existing industrial oxygen production energy consumption. ₂ compared to 12% energy saving. At the same time, liquid oxygen needs to heat up and vaporize before entering the engine to participate in the combustion reaction. This part of the cold energy will be used in the process of cooling and separating the water vapor and carbon dioxide in the exhaust.

Description of drawings

Fig. 1 is a flow chart of a method for realizing efficient and zero-pollution operation of a liquefied natural gas-powered ship engine according to the present invention;

Fig. 2 is the processing flowchart of exhaust gas in the engine exhaust cycle process of the present invention;

Figure 3 is a logic diagram of the engine electronic control system.

detailed description

The present invention will be described in detail below in conjunction with specific embodiments.

As shown in the accompanying drawings, a method for realizing efficient and zero-pollution operation of a liquefied natural gas-powered ship engine of the present invention comprises the following steps:

(1) The liquefied natural gas flows out from the liquefied natural gas storage tank 12, and is vaporized into natural gas through heat exchange;

(2) The heat exchange temperature of natural gas and oxygen reaches 5-10° C. through the seawater preheater 13; the natural gas after heat exchange enters the mixed pressure regulating gas distribution device 15 through the natural gas pipeline equipped with a natural gas flow sensor and a natural gas flow control valve 14, The oxygen after heat exchange enters the mixed pressure regulating gas distribution device 15 through the oxygen pipeline equipped with oxygen flow sensor and oxygen flow control valve 16, and the argon gas and oxygen enter the mixed pressure regulating gas distribution device according to the volume ratio of 3.7:1～3.8:1 15 becomes combustion-supporting gas, and natural gas and combustion-supporting gas (composed of argon and oxygen) are mixed in the mixing pressure regulating gas distribution device 15 at a volume ratio of 1:9.45 to 1:9.65, and then sent to the combustion chamber of the engine for combustion. The exhaust from the chamber enters the waste heat recovery device 11 and the seawater precooler 9 to recover waste heat and cool the exhaust to 5-10°C through the exhaust main pipe equipped with an oxygen concentration sensor and a gas flow meter;

A preferred control method for the volume ratio of combustion-supporting gas and natural gas in the mixing pressure regulating gas distribution device 15 in this step is: the engine electronic control unit receives the oxygen concentration signal in the engine exhaust output by the oxygen concentration sensor and compares it with the set Comparing the maximum allowable value of exhaust oxygen concentration, when the oxygen concentration in the exhaust gas is lower than the set value (it is recommended that the volume percentage of oxygen in the exhaust gas is less than 1%), the engine electronic control unit ECU outputs a control signal to the oxygen flow control valve 16 and natural gas flow control valve 14 to control the intake of natural gas and oxygen, so that the volume ratio of natural gas and combustion-supporting gas is 1:9.45 to 1:9.65; when the oxygen concentration in the exhaust gas is higher than the set value, the engine electronic control unit ECU Output control signals to the oxygen flow control valve 16 and the natural gas flow control valve 14 to control the intake of natural gas and oxygen, and reduce the oxygen supply in the next 1 second, so that the volume ratio of natural gas and combustion-supporting gas is 1:9.35～ 1:9.55, and then the engine electronic control unit ECU outputs control signals to the oxygen flow control valve 16 and the natural gas flow control valve 14, so that the volume ratio of natural gas and combustion-supporting gas is 1:9.45～1:9.65; the advantages of this are: 1. The oxygen content in the gas is basically the same as the oxygen content in the air. After mixing with natural gas in a given proportion, the isentropic index of the mixed gas is about 1.53, which is higher than the isentropic index of 1.40 after mixing air and natural gas in the same proportion. Improve the thermal efficiency of the engine; 2. Under a given gas ratio, lean fuel combustion in the engine cylinder can make natural gas burn quickly and fully; 3. According to the oxygen concentration value detected by the oxygen concentration sensor in the exhaust manifold, when the exhaust When the oxygen concentration value in the exhaust is higher than the normal value (it is recommended that the volume percentage of oxygen in the exhaust gas is less than 1%), the ECU sends a signal to adjust the natural gas flow control valve 14 in a short period of time (theoretically only needs to last for several engines The working cycle is about tens of milliseconds, but considering the hysteresis and inertia of the valve switch, set the time within 1s) to increase the natural gas supply, and then adjust the valve that controls the natural gas flow to restore the original gas supply flow. During the period of time, the engine performs fuel-rich combustion, consumes excess oxygen, and restores the oxygen concentration in the exhaust to a lower level.

(3) Part of the exhaust gas after the waste heat is recovered enters the main channel, and the other part of the exhaust gas enters the bypass channel at the upstream fulcrum 7 of the bypass channel connected with the main channel, and then enters the nitrogen oxide and sulfur oxide removal device 10 The flow control method of the exhaust gas entering the main channel and the bypass channel after removing nitrogen and sulfur is as follows: the engine electronic control unit ECU reads the gas flow signal output by the gas flow meter in the exhaust manifold and compares it with the set value, and then outputs the control signal. The signal is sent to the solenoid valve installed at the fulcrum 7 upstream of the bypass channel. When the exhaust flow is greater than the set value (such as: the exhaust flow value when the engine output power accounts for 75% of the rated engine power), the solenoid valve opening will be increased. To increase the gas flow of the bypass channel; when the exhaust flow is less than the set value, reduce the opening of the solenoid valve to reduce the gas flow of the bypass channel; the purpose of increasing the bypass channel is to remove the gas flow without increasing the exhaust resistance. Nitrogen oxides and sulfur oxides in exhaust gas.

(4) The exhaust gas that has been treated for nitrogen and sulfur removal returns to the main channel from the one-way valve at the fulcrum 8 downstream of the bypass channel, and enters the water cooling separation device 4 together with the gas in the main channel, so that the water vapor is liquefied and separated from the gas , and then through the carbon dioxide cooling and separating device 5, the carbon dioxide is separated from the gas in liquid form, and the remaining gas in the exhaust gas is argon-based gas that can participate in recirculation, and enters the mixing pressure regulating gas distribution device 15, and fresh Oxygen and natural gas mixed, enter the combustion chamber of engine 19 again to participate in combustion.

In the step (1), the liquefied natural gas exchanges heat with the main heat exchanger 2 in the air separation unit to heat up, and the cold energy in the liquefied natural gas is used to cool the air entering the air separation unit to separate oxygen, in the form of liquid oxygen Stored in liquid oxygen storage tank 3. The air separation unit is an existing equipment. The method only changes the heat exchange working medium of the main heat exchanger in the air separation unit, and uses LNG to cool the working medium in the main heat exchanger.

The preparation process of oxygen in the described step (1) is: the air passes through the air separation unit to separate the liquid oxygen, and the liquid oxygen enters the liquid oxygen storage tank 3 for storage, and the liquid oxygen flows out from the liquid oxygen storage tank 3. The water cooling and separating device 4 and the carbon dioxide cooling and separating device 5 exchange heat with the exhaust gas discharged from the engine, the cold energy of the liquid oxygen is utilized, the liquid oxygen is vaporized into oxygen and enters the oxygen storage tank 17, and the oxygen flows out to the seawater preheater 13 for heat exchange .

Preferably, during the exhaust gas gradient cooling and separation process, the water produced in the water cooling and separation device 4 is a combustion product with very few impurities, and after chemical treatment such as acid-base adjustment, it is used as domestic water on ships. The liquid carbon dioxide produced in the carbon dioxide cooling and separation device, according to the cooling capacity of the cold storage on the ship, is taken to continue cooling and compressing to make dry ice for refrigeration in the cold storage, and the rest of the liquid carbon dioxide can be stored in the storage tank for ballast or combined with seawater After heat exchange, it becomes carbon dioxide gas and is discharged into the atmosphere.

As shown in Figure 1, air first enters the air separation unit 1, and liquid oxygen flows out from the air separation unit 1 and enters the liquid oxygen storage tank 3 for storage; LNG flows out from the LNG storage tank 12 and passes through the main heat exchanger 2 of the air separation unit When using low-temperature LNG to cool the air that needs to be separated, save the power consumption in the process of separating air for oxygen production, realize the separation of nitrogen and oxygen in the air, store the generated liquid oxygen in the liquid oxygen storage tank, and discharge the useless nitrogen into the atmosphere .

LNG vaporizes into natural gas and enters the seawater preheater 13; liquid oxygen flows out from the liquid oxygen storage tank 3, and when passing through the water cooling separation device 4 and the carbon dioxide cooling separation device 5, the cold energy is utilized, and is vaporized into oxygen and enters the oxygen storage tank 17. It flows out to the seawater preheater 13; after the natural gas and oxygen are heated in the seawater preheater 13, the gas product—argon, which is separated from the engine exhaust through exhaust gradient cooling and separation—enters the mixed pressure regulating gas distribution device 15 to form A certain proportion of normal-pressure mixed gas enters the ship engine 19 to burn and perform work; the exhaust gas of the engine passes through the waste heat recovery device 11, where the heat energy is utilized, the temperature and pressure of the exhaust gas are reduced, and then enters the seawater precooler 9; After the seawater is cooled to normal temperature, at the fulcrum 7 upstream of the bypass channel, part of the exhaust gas enters the bypass channel to remove nitrogen and sulfur in the nitrogen oxide and sulfur oxide removal device 10, and then returns to the main channel from the downstream fulcrum 8 of the bypass channel , enter the water cooling separation device 4 together with the gas that has not passed through the bypass channel, so that the water vapor is liquefied and separated from the gas, and then passes through the carbon dioxide cooling separation device 5, so that the carbon dioxide is separated from the gas in liquid form. The separated product liquid water enters the water tank 6. The water is a combustion product of the engine with very few impurities. After simple chemical treatment, it can be used as domestic water on the ship; the separated product liquid carbon dioxide is stored in the liquid carbon dioxide storage tank 18. To meet the needs of refrigeration capacity, take part of it to continue cooling and compressing to make dry ice for refrigeration in cold storage, and the rest of the liquid carbon dioxide can be stored in storage tanks to replace the consumed LNG ballast, or it can be discharged into the atmosphere as carbon dioxide gas after exchanging heat with seawater . The remaining gas in the exhaust is argon-based gas that can participate in recirculation, enters the mixed pressure regulating gas distribution device, mixes with fresh oxygen and natural gas, and enters the engine 19 again to participate in combustion.

Figure 2 depicts the exhaust gas treatment flow during the engine exhaust cycle. Natural gas contains traces of nitrogen and sulfur elements, and a small amount of engine oil will participate in the combustion process in the engine cylinder. The engine oil may also contain nitrogen and sulfur elements, so there are nitrogen oxides and sulfur oxides in the exhaust of the engine. Considering all possibilities, the gas components present in the engine exhaust must be several of the following listed gases: argon, carbon dioxide, water vapor, natural gas, oxygen, carbon monoxide, nitrogen oxides, and sulfur oxides. Ship engines are usually equipped with waste heat recovery devices, most of which are waste heat boilers. After the engine exhaust passes through the waste heat recovery device, the temperature and pressure will decrease. After that, the gas in the main channel is passed into the seawater precooler to cool down to normal temperature, and is divided into two channels at the upstream fulcrum of the bypass channel. According to the control of the engine electronic control unit ECU, a part of the gas enters the bypass channel for nitrogen removal, Sulfur treatment, and then return to the main channel from the downstream fulcrum of the bypass channel. The nitrogen and sulfur removal device in the bypass channel can be a lye adsorption device or a device based on other principles, but this device cannot generate new gases when removing sulfur oxides and nitrogen dioxide. Then, all the gases in the main channel pass through the water heat exchange separation device and the carbon dioxide separation device in sequence. In the water cooling separation device, the gas in the main channel is cooled to 2-5°C (to ensure that the water vapor in the mixed gas in the main channel is basically cooled to liquid water), and the water vapor is separated from other gases in the form of liquid water. In the carbon dioxide cooling and separation device, the gas in the main channel is cooled to -83°C (to ensure that all the carbon dioxide in the mixed gas in the main channel is separated in liquid form), and the carbon dioxide is separated from the gas in liquid form. In this way, the gas remaining in the exhaust gas may only be some of the gases listed below: argon, natural gas, oxygen, carbon monoxide. These gases are all gases that can participate in recirculation, mix with fresh oxygen and natural gas, and enter the engine again to participate in combustion.

Figure 3 shows the logic diagram of the control system added by the engine electronic control unit ECU in order to realize the smooth operation of the engine. One of the things that can interfere with the smooth running of an engine is the cumulative effect of the gas cycle because the treated exhaust gas is all circulated. For example, if the exhaust gas treatment system does not have nitrogen and sulfur removal devices, the nitrogen oxides and sulfur oxides produced by the combustion of a small amount of engine oil will gradually accumulate during the continuous cycle. When the concentration of nitrogen oxides and sulfur oxides in the mixed gas When it is large enough, it will affect the normal operation of the engine. Another cumulative effect of gas circulation may occur on natural gas and oxygen. If the amount of oxygen in the gas distribution process exceeds the amount of oxygen required for the complete combustion of natural gas, there will be oxygen in the exhaust gas. If the two gases are not controlled When the gas volume is adjusted, the oxygen content in the exhaust gas will gradually accumulate, affecting the normal operation of the engine. Therefore, the engine electronic control unit ECU needs to increase the control function. 1. Set up a bypass channel, and install a device for removing nitrogen oxides and sulfur oxides in the bypass channel. This device can be a lye adsorption device or a device based on other principles, but this device cannot generate new gases when removing sulfur oxides and nitrogen dioxide. In the process of removing nitrogen oxides and sulfur oxides, the resistance of the gas is relatively large, and the pressure drops significantly. Therefore, the process of removing nitrogen oxides and sulfur oxides needs to be set in the bypass channel, and the upstream fulcrum of the bypass channel is controlled For the amount of gas entering the bypass channel, a one-way valve is installed at the downstream fulcrum of the bypass channel to ensure that the gas in the main channel does not flow back at the downstream fulcrum of the bypass channel. The amount of gas entering the bypass channel is determined by the engine electronic control unit ECU according to the signal of the gas flow sensor in the exhaust manifold of the engine. If the exhaust flow rate is large, the gas flow rate in the bypass channel will be increased; if the exhaust stray is small, the gas flow rate in the bypass channel will be reduced. flow. 2. Install an oxygen concentration sensor in the exhaust manifold of the engine to detect the oxygen concentration in the exhaust, and set the maximum allowable value of the exhaust oxygen concentration in the electronic control unit ECU. When the oxygen concentration in the exhaust is lower than the set value , the electronic control unit ECU controls the intake of natural gas and oxygen, so that the oxygen supply is slightly greater than the amount of oxygen consumed by the complete combustion of natural gas, so that the oxygen concentration in the exhaust after combustion will increase; when the oxygen concentration in the exhaust is higher than the set value, the electronic control unit ECU controls the intake of natural gas and oxygen, and reduces the oxygen supply in the next short period of time, so that the oxygen supply is slightly smaller than the amount of oxygen consumed by the complete combustion of natural gas, and the oxygen concentration in the engine exhaust Decrease rapidly to maintain smooth engine operation during such dynamic adjustments.

Example 1

(1) The liquefied natural gas flows out from the liquefied natural gas storage tank 12, the main heat exchanger in the liquefied natural gas and the air separation unit heats up, and the cold energy in the liquefied natural gas is used to cool the air entering the air separation unit to separate oxygen , stored in liquid oxygen storage tanks in the form of liquid oxygen. The liquid oxygen flows out of the liquid oxygen storage tank, and exchanges heat with the exhaust gas discharged from the engine when passing through the water cooling and separation device and the carbon dioxide cooling and separation device. The cold energy of the liquid oxygen is utilized, and the liquid oxygen is vaporized into oxygen and enters the oxygen storage tank;

(2) The heat exchange temperature of natural gas and oxygen reaches 5-8° C. through the seawater preheater 13; the natural gas after heat exchange enters the mixed pressure regulating gas distribution device 15 through the natural gas pipeline equipped with a natural gas flow sensor and a natural gas flow control valve 14, The oxygen after heat exchange enters the mixed pressure regulating gas distribution device 15 through the oxygen pipeline equipped with an oxygen flow sensor and an oxygen flow control valve 16, and the volume ratio of argon to oxygen is 3.8:1 (at this time, the oxygen content in the combustion-supporting gas is 20.83 %) into the mixed pressure regulating gas distribution device 15 to become combustion-supporting gas, natural gas and combustion-supporting gas (composition of argon and oxygen) with a volume ratio of 1:9.65 (the volume fraction of excess oxygen in the combustible gas mixture at this time is 0.47%) After being mixed in the mixing pressure regulating gas distribution device 15, it is sent to the combustion chamber of the engine for combustion. The exhaust gas from the combustion chamber of the engine passes through the exhaust manifold equipped with an oxygen concentration sensor and a gas flow meter and enters the waste heat recovery device 11 and the seawater precooler in turn. 9 Recover waste heat and cool the exhaust gas to 5-8°C;

In this step, the control method for the volume ratio of combustion-supporting gas and natural gas in the mixed pressure regulating gas distribution device 15 is as follows: the engine electronic control unit receives the oxygen concentration signal in the engine exhaust output from the oxygen concentration sensor and compares it with the set exhaust gas Compared with the maximum allowable value of oxygen concentration, when the volume percentage of oxygen in the exhaust gas is less than 1%, the engine electronic control unit ECU outputs control signals to the oxygen flow control valve 16 and the natural gas flow control valve 14 to control the intake volume of natural gas and oxygen , so that the volume ratio of natural gas and combustion-supporting gas is 1:9.65; when the oxygen concentration in the exhaust gas is higher than the set value, the engine electronic control unit ECU outputs a control signal to the oxygen flow control valve 16 and the natural gas flow control valve 14 to control the natural gas and oxygen intake, reduce the oxygen supply in the next 1 second, so that the volume ratio of natural gas and combustion-supporting gas is 1:9.55, and then the engine electronic control unit ECU outputs control signals to the oxygen flow control valve 16 and the natural gas flow control Valve 14, so that the volume ratio of natural gas and combustion-supporting gas is 1:9.65;

(3) Part of the exhaust gas after the waste heat is recovered enters the main channel, and the other part of the exhaust gas enters the bypass channel at the upstream fulcrum 7 of the bypass channel connected with the main channel, and then enters the nitrogen oxide and sulfur oxide removal device 10 The flow control method of the exhaust gas entering the main channel and the bypass channel after removing nitrogen and sulfur is as follows: the engine electronic control unit ECU reads the gas flow signal output by the gas flow meter in the exhaust manifold and compares it with the set value, and then outputs the control signal. The signal is sent to the solenoid valve installed at the fulcrum 7 upstream of the bypass channel. When the exhaust flow is greater than the set value (such as: the exhaust flow value when the engine output power accounts for 75% of the rated engine power), the solenoid valve opening will be increased. To increase the gas flow of the bypass channel; when the exhaust flow is less than the set value, reduce the opening of the solenoid valve to reduce the gas flow of the bypass channel; the purpose of increasing the bypass channel is to remove the gas flow without increasing the exhaust resistance. Nitrogen oxides and sulfur oxides in exhaust gas.

(4) The exhaust gas that has been treated for nitrogen and sulfur removal returns to the main channel from the one-way valve at the fulcrum 8 downstream of the bypass channel, and enters the water cooling separation device 4 together with the gas in the main channel, so that the water vapor is liquefied and separated from the gas , and then through the carbon dioxide cooling and separating device 5, the carbon dioxide is separated from the gas in liquid form, and the remaining gas in the exhaust gas is argon-based gas that can participate in recirculation, and enters the mixing pressure regulating gas distribution device 15, and fresh Oxygen and natural gas mixed, enter the combustion chamber of engine 19 again to participate in combustion.

After testing, the engine can maintain stable operation during operation. The oxygen content in the intake air of the engine is slightly lower than that of the air, but the effect on the maximum temperature in the engine cylinder is not obvious. The oxygen content in the engine exhaust changes dynamically but remains below 1%. Due to the use of argon instead of nitrogen, the isentropic index of the engine intake increases from 1.40 to 1.53, the output power of the engine increases by 14.8%, and the power consumption of the air separation unit Accounting for 20.4% of the total output power of the engine, the whole scheme provides a sufficient amount of heat sources of various temperature grades for the ship, which greatly reduces the power consumption of the ship's basic devices such as air conditioners, cold storage, water heaters, and steam generators. Considering the ship's power system and thermal system, the output work of the engine other than the propeller can be reduced from the existing 12% to about 5%.

Example 2

(1) The liquefied natural gas flows out from the liquefied natural gas storage tank 12, the main heat exchanger in the liquefied natural gas and the air separation unit heats up, and the cold energy in the liquefied natural gas is used to cool the air entering the air separation unit to separate oxygen , stored in liquid oxygen storage tanks in the form of liquid oxygen. The liquid oxygen flows out of the liquid oxygen storage tank, and exchanges heat with the exhaust gas discharged from the engine when passing through the water cooling and separation device and the carbon dioxide cooling and separation device. The cold energy of the liquid oxygen is utilized, and the liquid oxygen is vaporized into oxygen and enters the oxygen storage tank;

(2) The heat exchange temperature of natural gas and oxygen reaches 7-10°C through the seawater preheater 13; the natural gas after heat exchange enters the mixed pressure regulating gas distribution device 15 through the natural gas pipeline equipped with a natural gas flow sensor and a natural gas flow control valve 14, The oxygen after the heat exchange enters the mixed pressure regulating gas distribution device 15 through the oxygen pipeline equipped with the oxygen flow sensor and the oxygen flow control valve 16, and the argon gas and oxygen enter the mixed gas at a volume ratio of 3.7:1 (the oxygen content is 21.28% at this time). In the pressure regulating gas distribution device 15, it becomes a combustion-supporting gas, and natural gas and combustion-supporting gas (argon and oxygen composition) are mixed in the mixing pressure regulating gas distribution device 15 with a volume ratio of 1:9.45 and delivered to the combustion chamber of the engine for combustion. The exhaust gas from the combustion chamber enters the waste heat recovery device 11 and the seawater precooler 9 through the exhaust main pipe equipped with an oxygen concentration sensor and a gas flow meter to recover waste heat and cool the exhaust gas to 7-10°C;

In this step, the control method for the volume ratio of combustion-supporting gas and natural gas in the mixed pressure regulating gas distribution device 15 is as follows: the engine electronic control unit receives the oxygen concentration signal in the engine exhaust output from the oxygen concentration sensor and compares it with the set exhaust gas Compared with the maximum allowable value of oxygen concentration, when the volume percentage of oxygen in the exhaust gas is less than 1%, the engine electronic control unit ECU outputs control signals to the oxygen flow control valve 16 and the natural gas flow control valve 14 to control the intake volume of natural gas and oxygen , so that the volume ratio of natural gas and combustion-supporting gas is 1:9.45; when the oxygen concentration in the exhaust gas is higher than the set value, the engine electronic control unit ECU outputs a control signal to the oxygen flow control valve 16 and the natural gas flow control valve 14 to control the natural gas and oxygen intake, reduce the oxygen supply in the next 1 second, so that the volume ratio of natural gas and combustion-supporting gas is 1:9.35, and then the engine electronic control unit ECU outputs a control signal to the oxygen flow control valve 16 and the natural gas flow control Valve 14, so that the volume ratio of natural gas and combustion-supporting gas is 1:9.45;

(3) Part of the exhaust gas after the waste heat is recovered enters the main channel, and the other part of the exhaust gas enters the bypass channel at the upstream fulcrum 7 of the bypass channel connected with the main channel, and then enters the nitrogen oxide and sulfur oxide removal device 10 The flow control method of the exhaust gas entering the main channel and the bypass channel after removing nitrogen and sulfur is as follows: the engine electronic control unit ECU reads the gas flow signal output by the gas flow meter in the exhaust manifold and compares it with the set value, and then outputs the control signal. The signal is sent to the solenoid valve installed at the fulcrum 7 upstream of the bypass channel. When the exhaust flow is greater than the set value (such as: the exhaust flow value when the engine output power accounts for 75% of the rated engine power), the solenoid valve opening will be increased. To increase the gas flow of the bypass channel; when the exhaust flow is less than the set value, reduce the opening of the solenoid valve to reduce the gas flow of the bypass channel; the purpose of increasing the bypass channel is to remove the gas flow without increasing the exhaust resistance. Nitrogen oxides and sulfur oxides in exhaust gas.

(4) The exhaust gas that has been treated for nitrogen and sulfur removal returns to the main channel from the one-way valve at the fulcrum 8 downstream of the bypass channel, and enters the water cooling separation device 4 together with the gas in the main channel, so that the water vapor is liquefied and separated from the gas , and then through the carbon dioxide cooling and separating device 5, the carbon dioxide is separated from the gas in liquid form, and the remaining gas in the exhaust gas is argon-based gas that can participate in recirculation, and enters the mixing pressure regulating gas distribution device 15, and fresh Oxygen and natural gas mixed, enter the combustion chamber of engine 19 again to participate in combustion.

After testing, the engine can maintain stable operation during operation. The oxygen content in the intake air of the engine is slightly higher than that of the air, and the maximum temperature in the engine cylinder will rise, and the increase is less than 50°C. The oxygen content in the engine exhaust changes dynamically but remains below 1%. As the isentropic index of the engine intake increases from 1.40 to 1.53 with argon instead of nitrogen, the output power of the engine increases by 15.2%, and the power consumption of the air separation unit accounts for the engine power 20.0% of the total output power, the whole scheme provides a sufficient amount of heat sources of various temperature grades for the ship, which greatly reduces the power consumption of the ship’s basic devices such as air conditioners, cold storage, water heaters, and steam generators. The power system and thermal system of the engine can be reduced from the existing 12% to 4%.

Example 3

(1) The liquefied natural gas flows out from the liquefied natural gas storage tank 12, the main heat exchanger in the liquefied natural gas and the air separation unit heats up, and the cold energy in the liquefied natural gas is used to cool the air entering the air separation unit to separate oxygen , stored in liquid oxygen storage tanks in the form of liquid oxygen. The liquid oxygen flows out of the liquid oxygen storage tank, and exchanges heat with the exhaust gas discharged from the engine when passing through the water cooling and separation device and the carbon dioxide cooling and separation device. The cold energy of the liquid oxygen is utilized, and the liquid oxygen is vaporized into oxygen and enters the oxygen storage tank;

(2) The heat exchange temperature of natural gas and oxygen reaches 6-9° C. through the seawater preheater 13; the natural gas after heat exchange enters the mixed pressure regulating gas distribution device 15 through the natural gas pipeline equipped with a natural gas flow sensor and a natural gas flow control valve 14, The oxygen after heat exchange enters the mixed pressure regulating gas distribution device 15 through the oxygen pipeline equipped with oxygen flow sensor and oxygen flow control valve 16, and argon and oxygen enter the mixed pressure regulating gas distribution device 15 at a volume ratio of 3.76:1 to become combustion-supporting Gas, natural gas and combustion-supporting gas (composed of argon and oxygen) are mixed in the mixing pressure regulating gas distribution device 15 with a volume ratio of 1:9.55 and delivered to the combustion chamber of the engine for combustion. The exhaust main pipe of the sensor and the gas flowmeter enters the waste heat recovery device 11 and the seawater precooler 9 to recover the waste heat and cool the exhaust gas to 6-9°C;

In this step, the control method for the volume ratio of combustion-supporting gas and natural gas in the mixed pressure regulating gas distribution device 15 is as follows: the engine electronic control unit receives the oxygen concentration signal in the engine exhaust output from the oxygen concentration sensor and compares it with the set exhaust gas Compared with the maximum allowable value of oxygen concentration, when the volume percentage of oxygen in the exhaust gas is less than 1%, the engine electronic control unit ECU outputs control signals to the oxygen flow control valve 16 and the natural gas flow control valve 14 to control the intake volume of natural gas and oxygen , so that the volume ratio of natural gas and combustion-supporting gas is 1:9.55; when the oxygen concentration in the exhaust gas is higher than the set value, the engine electronic control unit ECU outputs a control signal to the oxygen flow control valve 16 and the natural gas flow control valve 14 to control the natural gas and oxygen intake, reduce the oxygen supply in the next 1 second, so that the volume ratio of natural gas and combustion-supporting gas is 1:9.50, and then the engine electronic control unit ECU outputs control signals to the oxygen flow control valve 16 and the natural gas flow control Valve 14, so that the volume ratio of natural gas and combustion-supporting gas is 1:9.55;

(3) Part of the exhaust gas after the waste heat is recovered enters the main channel, and the other part of the exhaust gas enters the bypass channel at the upstream fulcrum 7 of the bypass channel connected with the main channel, and then enters the nitrogen oxide and sulfur oxide removal device 10 The flow control method of the exhaust gas entering the main channel and the bypass channel after removing nitrogen and sulfur is as follows: the engine electronic control unit ECU reads the gas flow signal output by the gas flow meter in the exhaust manifold and compares it with the set value, and then outputs the control signal. The signal is sent to the solenoid valve installed at the fulcrum 7 upstream of the bypass channel. When the exhaust flow is greater than the set value (such as: the exhaust flow value when the engine output power accounts for 75% of the rated engine power), the solenoid valve opening will be increased. To increase the gas flow of the bypass channel; when the exhaust flow is less than the set value, reduce the opening of the solenoid valve to reduce the gas flow of the bypass channel; the purpose of increasing the bypass channel is to remove the gas flow without increasing the exhaust resistance. Nitrogen oxides and sulfur oxides in exhaust gas.

(4) The exhaust gas that has been treated for nitrogen and sulfur removal returns to the main channel from the one-way valve at the fulcrum 8 downstream of the bypass channel, and enters the water cooling separation device 4 together with the gas in the main channel, so that the water vapor is liquefied and separated from the gas , and then through the carbon dioxide cooling and separating device 5, the carbon dioxide is separated from the gas in liquid form, and the remaining gas in the exhaust gas is argon-based gas that can participate in recirculation, and enters the mixing pressure regulating gas distribution device 15, and fresh Oxygen and natural gas mixed, enter the combustion chamber of engine 19 again to participate in combustion.

After testing, the engine can maintain stable operation during operation, and compared with Embodiments 1 and 2, the variation range of the output power of the engine during operation is smaller, within 2%. The oxygen content in the engine exhaust changes dynamically but remains below 1%. As the isentropic index of the engine intake increases from 1.40 to 1.53 with argon instead of nitrogen, the output power of the engine increases by 15.0%, and the power consumption of the air separation unit accounts for the engine power 20.1% of the total output power, the whole scheme provides a sufficient amount of heat sources of various temperature grades for the ship, which greatly reduces the power consumption of the ship’s basic devices such as air conditioners, cold storage, water heaters, and steam generators. The power system and thermal system of the engine can be reduced from the existing 12% to 4%.

Claims (5)

1. A kind of 1. method for realizing the efficient no pollution operation of liquefied natural gas power engine of boat and ship, it is characterised in that:It include with Lower step：

   (1) liquefied natural gas is flowed out from LNG tank, and natural gas is vaporizated into through heat exchange；

   (2) natural gas, oxygen reach 5-10 DEG C by seawater preheating device heat-exchange temperature；Natural gas after heat exchange is by being provided with day The natural gas line of right mass-air-flow sensor and natural gas flow control valve enters combined voltage regulation air distributing device, the oxygen after heat exchange Oxygen channel by being provided with oxygen flow sensor and oxygen flux control valve enters combined voltage regulation air distributing device, argon gas with Oxygen by volume 3.7:1~3.8:1 enter combined voltage regulation air distributing device in turn into combustion-supporting gas, natural gas and combustion-supporting gas with 1:9.45~1:9.65 volume ratio is transported to the combustion chambers burn of engine after being mixed in combined voltage regulation air distributing device, start The exhaust combustion chamber of machine passes through the exhaust main equipped with oxygen concentration sensor and gas flow meter and sequentially enters waste-heat recovery device With seawater forecooler recovery waste heat and exhaust is cooled to 5-10 DEG C；

   (3) part exhaust after waste heat is recovered enters main channel, and another part exhaust is led in the bypass connected with main channel Enter bypass passageways at the fulcrum of road upstream, denitrification sulphur is then removed in nitrogen oxides, oxysulfide removal device, into main channel Flow control methods with the exhaust of bypass passageways are：Engine electronic control unit reads the gas flowmeter in exhaust main Gas flow signals of output and compared with setting value, then output control signal, which is given, is arranged at the fulcrum of bypass passageways upstream Magnetic valve, when extraction flow is more than setting value, then increase electromagnetism valve opening to increase bypass passageways gas flow；Work as extraction flow Less than setting value, then reduce electromagnetism valve opening to reduce bypass passageways gas flow；

   (4) exhaust by denitrogenating sulphuring treatment returns to main channel from the check valve at the fulcrum of bypass passageways downstream, in main channel Gas together enter water cooling separator, vapor liquefaction is separated from gas, then by carbon dioxide refrigerated separation Device, carbon dioxide is set to be separated in liquid form from gas, remaining gas is may participate in again based on argon gas in exhaust The gas of circulation, into combined voltage regulation air distributing device, mixed with fresh oxygen and natural gas, be again introduced into the combustion of engine Burn room and participate in burning.
2. 2. the method according to claim 1 for realizing the efficient no pollution operation of liquefied natural gas power engine of boat and ship, it is special Sign is:The control method of the volume ratio of combustion-supporting gas and natural gas in combined voltage regulation air distributing device in described step (2) For：Engine electronic control unit receive oxygen concentration sensor output engine exhaust in oxygen concentration signal and with setting Density of oxygen contained in discharged gas maximum permissible value compares, when oxygen concentration is less than setting value in exhaust, engine electronic control unit output Control signal oxygen supply flow control valves and natural gas flow control valve, the air inflow of natural gas and oxygen is controlled, makes natural gas It is 1 with Combustion gas volume ratio:9.45~1:9.65；When oxygen concentration is higher than setting value in exhaust, engine electronic control system Unit output control signal oxygen supply flow control valves and natural gas flow control valve, to control the air inlet of natural gas and oxygen Amount, oxygen quantity delivered was reduced in ensuing 1 second, it is 1 to make natural gas and Combustion gas volume ratio:9.35~1:9.55 it Rear engine electronic control unit output control signal oxygen supply flow control valves and natural gas flow control valve, make natural gas with Combustion gas volume ratio is 1:9.45~1:9.65.
3. 3. the method according to claim 1 or 2 for realizing the efficient no pollution operation of liquefied natural gas power engine of boat and ship, its It is characterised by:Liquefied natural gas heats up with the main heat exchanger heat exchange in air separation unit in described step (1), in liquefied natural gas Cold energy be used for cool down into air separation unit air, to isolate oxygen, liquid oxygen storage tank is stored in the form of liquid oxygen.
4. 4. the method according to claim 3 for realizing the efficient no pollution operation of liquefied natural gas power engine of boat and ship, it is special Sign is:The preparation process of oxygen is in described step (1)：Liquid oxygen flows out from liquid oxygen storage tank, by described water cooling Waste gas when separator and carbon dioxide refrigerated separation device with engine discharge is exchanged heat, and the cold energy of liquid oxygen is utilized, liquid Oxygen is vaporizated into oxygen and enters oxygen storage tank, and oxygen is passed out to seawater preheating device and exchanged heat.
5. 5. the method according to claim 1 or 2 for realizing the efficient no pollution operation of liquefied natural gas power engine of boat and ship, its It is characterised by:The caused water in water cooling separator, after chemical treatment, as the domestic water on ship；Two Caused liquid carbon dioxide in carbonoxide refrigerated separation device, part is taken to continue to cool down compression and dry ice is made is used for freezer system Cold, remaining liquid carbon dioxide, which is stored in storage tank, is used for ballasting or with being discharged into after seawater to make heat exchange as carbon dioxide Air.