Gas supply system and method for supplying gas to a high-pressure gas injection engine

Abstract

A gas supply system (1) for supplying a gas stored in a liquefied gas tank (3), preferably in an LNG tank, to a high-pressure gas injection engine (2) comprises a high-pressure pump (5) which supplies liquefied gas (F1) from the liquefied gas tank (3), a condenser (6) in which a high-pressure heat exchanger (13) is arranged, a high-pressure evaporator (7) which is connected to the high-pressure pump (5) via the high-pressure heat exchanger (13) and is arranged downstream of the condenser (6), wherein the gas is conducted downstream of the high-pressure evaporator (7) to the high-pressure gas injection engine (2), a compressor (9) to which evaporated gas (F2) is supplied from the liquefied gas tank (3), wherein the compressor (9) is connected downstream via a conducting unit (15d) to the condenser (6) to conduct the evaporated gas (F2) into the condenser (6), and a condensation nucleus generator (10) which is supplied with liquefied gas (F1) from the high-pressure pump (5), wherein the condensation nucleus generator (10) and the conducting unit (15d) are arranged in the condenser (6) in such a way that the condensation nuclei generated by the condensation nucleus generator (10) promote the condensation of the evaporated gas (F2) conducted into the condenser (6) to form liquefied gas (F1) and in such a way that the liquefied gas (F1) formed in the condenser (6) is conducted to the high-pressure pump (5) and / or to the liquefied gas tank (3).

Description

TECHNICAL FIELD

[0001] The invention relates to a gas supply system. The invention further relates to a method for supplying a high-pressure gas injection engine with gas. BACKGROUND

[0002] Natural gas is an energy source that is becoming increasingly important. In commercial shipping, natural gas is increasingly used as an alternative fuel to meet new adaptability requirements relating to exhaust gas purification and the reduction of greenhouse gases in the shipping industry. Natural gas used as a fuel is usually stored on board in liquid form, in English "liquefied natural gas" or abbreviated "LNG", and is stored in a liquefied gas tank at approximately atmospheric pressure and a temperature of approximately -163 degrees Celsius (°C). Due to the minimum boiling point of approximately -162 degrees Celsius of the liquefied gas at atmospheric pressure, the liquefied gas is continuously vaporized by external heat acting on the LNG tank, which accumulates as vaporized gas on the top of the LNG tank, in English "boil off gas" abbreviated BOG, which leads to an increase in pressure in the LNG tank. To counteract this pressure increase, a BOG re-liquefaction device is known, which liquefies the boil off gas and feeds it back to the LNG tank as liquefied gas. Another possibility for this is to use the boil off gas directly as a ship propulsion fuel. For this purpose, the natural gas is compressed at high pressure, for example in the range of 150-300 bar absolute (bara) or 150-400 bara, to form high-pressure natural gas and is introduced into a high-pressure gas injection engine. Such an engine is marketed, for example, by the company MAN-SE under the name ME-GI engine. Such an engine preferably forms the main propulsion system of a merchant ship.

[0003] The patent document KR 102011 0030149 discloses a gas supply system for supplying a high-pressure gas injection engine of a liquefied gas tank ship with gas. The system is able, on the one hand, to compress the natural gas stored in the LNG tank so that it is introduced into the high-pressure gas injection engine and, on the other hand, to prevent an excessively high pressure rise in the LNG tank by re-liquefying the boil off gas when necessary, which is then fed to the high-pressure gas injection engine and / or the LNG tank. The gas supply system disclosed in the patent document KR 102011 0030149 has the disadvantage that it is relatively complex and expensive and uses an external cooling circuit and requires a considerable energy consumption for its operation.

[0004] Patent document KR 100726 290 shows a method for recovering excess boil-off gas by manipulating the liquefaction, re-liquefaction or use of the boil-off gas. The method comprises the steps of liquefying the boil-off gas, selectively sending the liquefied gas back to the gas storage tank or selectively sending the liquefied gas to a liquefied gas evaporator via first and second manipulable valves. A quantity of the liquefied gas is evaporated in the liquefied gas evaporator, which is thus adapted to be sent out as fuel by manipulating the temperature, pressure and flow rate. The method further comprises sending the evaporated gas to the propulsion system as fuel and recovering the liquefied boil-off gas or opening / closing the first, second, third and fourth valves to burn a small amount of the boil-off gas. In this system, the specific heat capacity of the injected supercooled LNG is used to re-liquefy the BOG. However, it is a low-pressure system and is not suitable for supplying fuel gas to a high-pressure gas injection engine. SUMMARY

[0005] It is the task of the present invention to form an economically more advantageous fuel gas supply system. Furthermore, it is the task of the present invention to form an economically more advantageous method for supplying fuel gas to a high-pressure gas injection engine. This task is solved by the fuel gas supply system of the present invention.

[0006] This task is solved in particular by a fuel gas supply system for supplying a gas stored in a liquefied gas tank, in particular in a liquefied gas tank, to a high-pressure gas injection engine, comprising a high-pressure pump which can be connected in fluid connection with the liquefied gas tank, preferably via a low-pressure pump, to supply liquefied gas from the liquefied gas tank and to compress the liquefied gas to high-pressure liquefied gas or to provide it as high-pressure liquefied gas; comprising a condenser in which a high-pressure heat exchanger is arranged; comprising a high-pressure evaporator which is connected in fluid connection with the high-pressure pump via the high-pressure heat exchanger and is arranged downstream of the condenser, wherein the high-pressure evaporator converts the high-pressure liquefied gas into high-pressure fuel gas and the high-pressure fuel gas is guided downstream of the high-pressure evaporator to the high-pressure gas injection engine; comprising a compressor which can be connected in fluid connection with the liquefied gas tank to supply boil-off gas from the liquefied gas tank, wherein the compressor can be connected in fluid connection downstream via a guiding unit to an inner chamber of the condenser to guide the boil-off gas into the inner chamber; and further comprising a condensation nucleus generator which is connected in fluid connection downstream of the high-pressure pump, wherein the condensation nucleus generator is designed in such a way that it generates from the high-pressure liquefied gas liquid droplets of liquefied gas as condensation nuclei, wherein the condensation nuclei are fed by the condensation nucleus generator into the inner chamber in order to promote the condensation of the guided-in boil-off gas via the condensation nuclei, thus forming liquefied gas from it itself, and the liquefied gas formed in the condenser is guided to the high-pressure pump and / or to the liquefied gas tank.

[0007] The task is solved, inter alia, by a gas supply system for a high-pressure gas injection engine, which is supplied with gas stored in a liquefied gas tank, comprising a high-pressure pump into which liquefied gas from the liquefied gas tank is fed, comprising a condenser in which a high-pressure heat exchanger is arranged, comprising a high-pressure evaporator which is connected to the high-pressure pump via the high-pressure heat exchanger and is arranged downstream of the condenser, wherein the gas is conducted downstream of the high-pressure evaporator into the high-pressure gas injection engine, comprising a compressor into which evaporated gas from the liquefied gas tank is fed, wherein the compressor is connected downstream via a feed-in unit to the condenser in order to conduct the evaporated gas into the condenser, and comprising a condensation nucleus generator into which liquefied gas is fed by the high-pressure pump, wherein the condensation nucleus generator and the feed-in unit are arranged in the condenser in such a way that condensation nuclei generated in the condensation nucleus generator in the condenser promote the condensation of the fed-in evaporated gas, so that liquefied gas is formed therefrom and the liquefied gas formed in the condenser is conducted into the high-pressure pump and / or the liquefied gas tank.

[0008] The task is solved, inter alia, by a method for supplying a high-pressure gas injection engine with gas, wherein the gas is stored in a liquefied gas tank partly as liquefied gas and partly as evaporated gas, wherein liquefied gas from the liquefied gas tank is fed to a high-pressure pump and is compressed by the high-pressure pump to high-pressure liquefied gas, wherein the high-pressure liquefied gas is then fed to a high-pressure heat exchanger arranged in a condenser and is subsequently fed to a high-pressure evaporator, wherein the high-pressure liquefied gas in the high-pressure evaporator is converted into high-pressure gas, so that gas at high pressure is produced, which is conducted into the high-pressure gas injection engine, wherein evaporated gas from the liquefied gas tank is fed to a compressor and is then fed into the condenser, wherein a condensation nucleus stream in the form of liquefied gas droplets is produced from the high-pressure liquefied gas in a condensation nucleus generator, which condensation nucleus stream in the condenser is fed to the fed-in evaporated gas in order to promote the condensation of the evaporated gas to liquefied gas by means of the liquefied gas droplets, and in this way liquefied gas formed in the condenser is conducted to the high-pressure pump and / or the liquefied gas tank.

[0009] The task is solved, inter alia, by a method for supplying a high-pressure gas injection engine with gas, wherein the gas is stored in a liquefied gas tank partly as liquefied gas and partly as evaporated gas, wherein liquefied gas from the liquefied gas tank is fed to a high-pressure pump and is compressed by the high-pressure pump to high-pressure liquefied gas, wherein the high-pressure liquefied gas is then fed to a high-pressure heat exchanger arranged in a condenser and is subsequently fed to a high-pressure evaporator, wherein the high-pressure liquefied gas in the high-pressure evaporator is converted into high-pressure gas, so that gas at high pressure is produced, which is conducted into the high-pressure gas injection engine, wherein evaporated gas from the liquefied gas tank is fed to a compressor and is then fed into the condenser, wherein a condensation nucleus stream in the form of liquefied gas droplets is produced from the high-pressure liquefied gas in a condensation nucleus generator, which condensation nucleus stream in the condenser is fed to the fed-in evaporated gas in order to promote the condensation of the evaporated gas to liquefied gas by means of the liquefied gas droplets, and in this way liquefied gas formed in the condenser is conducted to the high-pressure pump and / or the liquefied gas tank.

[0010] The gas supply system according to the application uses a condenser for condensing the boil-off gas to liquefied gas. For this, condensation nuclei are generated from the liquefied gas with the help of a condensation nuclei generator, which condensation nuclei come into contact with the boil-off gas in the interior of the condenser, which is located in the interior space of the condenser, so that the boil-off gas adheres to the condensation nuclei and condenses there to liquefied gas. The condensation nuclei are preferably generated with the help of high-pressure liquefied gas, which is discharged through a nozzle, in particular a spray head, so that a large number of gas droplets as condensation nuclei are generated with the help of the nozzle. The gas supply system according to the application has the advantage that the condensation takes place at a relatively low pressure, for liquefied gas for example at a pressure in the range below 50 bar absolute (bara), preferably in the range of 20 to 30 bar absolute, particularly preferably in the range of 10 to 20 bar absolute, and that a condensate or liquefied gas having a relatively low temperature is generated, for example having a temperature below -120 degrees Celsius (°C) and preferably between -120 degrees Celsius and -150 degrees Celsius. A pressure below 20 bar absolute has the advantage that a two-stage compressor is sufficient for compressing the boil-off gas F2 in the compressor 9. For a pressure in the range between 40 and 50 bar absolute, a three-stage compressor 9 is required. For cost reasons, a two-stage compressor 9 or a compression of the boil-off gas F2 in the range of 10 to 20 bar absolute is particularly preferred. The relatively low pressure in the interior of the condenser, which prevails during condensation before the boil-off gas is introduced into the condenser, requires a lower specific enthalpy for the compression process of the boil-off gas occurring upstream of the condenser. This has the advantage that a smaller, and thus less expensive, compressor is sufficient for this compression process. If the condensate is then fed to a high-pressure pump, the lower temperature of the condensate additionally leads to a reduced evaporation in the high-pressure pump and thus to an increased mean time between overhaul, which is also referred to as MTBO, of the high-pressure pump, so that the gas supply system according to the application can be operated more cost-effectively and more reliably.

[0011] A "high-pressure pump" in the sense of the application is understood in particular as a pump which generates an absolute pressure of at least 80 bar, preferably an absolute pressure of 100 to 400 bar, typically an absolute pressure of 150 to 300 bar. It can be a positive displacement machine, for example a piston pump. Conversely, a "low-pressure pump" is understood as a pump, for example a fluid machine, which generates an absolute pressure of less than 80 bar, typically an absolute pressure of 5 to 25 bar.

[0012] The liquefied tank is preferably an LNG tank and the fuel gas is natural gas, in particular methane. However, other fuel gases are also conceivable, in particular ethylene, ethane or ammonia. The system and the method must then be operated under adapted pressure and temperature conditions. In the case of ammonia as fuel, for example, the high-pressure pump should generate an absolute pressure of 300 to 400 bar. Such a liquefied gas can be fed in the form of liquefied gas droplets into the interior of the condenser in the condensation section of the condenser with a temperature of -10 to +10 degrees Celsius and an absolute pressure of 5 to 10 bar.

[0013] In a preferred embodiment, if only a small amount of liquefied gas is injected by means of the condensation nucleus generator, this is sufficient in comparison with the mass flow of the gas stream to be condensed. In particular, this is sufficient when the mass flow of liquefied gas (Fl) in the condensation nucleus generator is 1% to 5% of the mass flow of the evaporated gas (F2).

[0014] The fuel gas supply system according to the application thus has the advantage that the re-liquefaction pressure and the re-liquefaction temperature of the evaporated gas to be re- liquefied or the re-liquefaction pressure and the re-liquefaction temperature of the liquefied gas resulting therefrom are reduced.

[0015] The fuel gas supply system according to the application has the further advantage that the compression of the evaporated gas upstream of the condenser requires a smaller specific enthalpy, so that the compressor can be designed at low cost and, in addition, the operating costs (OPEX, "Operational Expenditures") for the compressor are reduced, in particular the energy costs.

[0016] The fuel gas supply system according to the application has the further advantage that, as a result of the improved condensation, a smaller condenser design is required, which reduces the capital expenditure (CAPEX, "Capital Expenditure"). The heat exchanger according to the application is a heat exchanger based on indirect heat transfer, i.e. the media flows are separated by a heat-permeable wall. Thereby, a high-pressure heat exchanger can be realized, in which the cooling liquid is fed to the cooling section at high pressure, for example 80 to 300 bar absolute, and leaves it again at essentially the same pressure. As a result of the improved condensation, a high-pressure heat exchanger with a smaller heat transfer surface is sufficient, so that a smaller high-pressure heat exchanger and thus a smaller condenser are required in the condenser.

[0017] The fuel gas supply system according to the application has the further advantage that the efficiency of the high-pressure pump is improved by the reduced, lower temperature of the liquefied gas condensed from the evaporated gas.

[0018] Preferably, the side stream of high-pressure liquefied gas is tapped off from or downstream of the high-pressure pump. Advantageously, this side stream of high-pressure liquefied gas is cooled in a heat exchanger, into which the boil-off gas from the liquid gas tank is introduced. Advantageously, the condenser for condensing the boil-off gas comprises a condensation nucleus generator or a spraying system for generating liquid droplets, into which the supercooled high-pressure liquefied gas is fed in order to generate condensation nuclei or aerosol droplets, and into which the condensation nuclei are introduced or sprayed inside the condenser, wherein the condensation nuclei serve to improve the degree of condensation of the boil-off gas. The spraying of the liquefied gas takes place with a special nozzle, which ensures the correct droplet size, so that these LNG droplets can act as condensation nuclei. For this, the physical surface effect, the curvature effect or the interface effect, also known as the Gibbs-Thomson effect, is used. This technical principle is known from the field of nanotechnology and aerosol technology. When the nozzle is a high-pressure nozzle, it is particularly preferred to have a high-pressure nozzle with a nozzle diameter in the range of 1 to 1000 micrometers (pm), preferably 5 to 500 micrometers. Such a high-pressure nozzle is suitable for generating liquid droplets in the relevant range, typically with a diameter of 100 micrometers to 100 micrometers, preferably 500 micrometers to 50 micrometers.

[0019] In a preferred embodiment, the boil-off gas (F2) enters the condenser from above, wherein the high-pressure heat exchanger itself extends in vertical direction inside the condenser and is arranged such that the high-pressure liquefied gas inside the high-pressure heat exchanger flows from bottom to top. Thus, a natural temperature gradient in the interior of the condenser is supported. Preferably, the condensation nucleus generator is arranged such that the condensation nuclei generated by the condensation nucleus generator are introduced into the condensation section of the interior of the condenser, wherein the interior has a condensation temperature. For example at a pressure of 17 bar absolute, the boiling point temperature of natural gas is at about -110 degrees Celsius. In order to achieve a complete re-liquefaction of the boil-off gas F2 in the condenser, the actual condensation temperature has to be about -120 degrees Celsius. Preferably, the condensation nucleus generator is arranged such that the first half, preferably the first third, of the cooling ducts of the high-pressure heat exchanger in the flow direction of the liquefied gas (F1) enter the interior of the condenser. BRIEF DESCRIPTION OF DRAWINGS

[0020] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description, serve to explain the principles of the application:

[0021] Figure 1 a first embodiment of a gas supply system is schematically shown;

[0022] Figure 2 a second embodiment of a gas supply system is schematically shown;

[0023] Figure 3A third embodiment of a gas supply system is schematically shown;

[0024] Figure 4 A fourth embodiment of a gas supply system is schematically shown;

[0025] Figure 5 A fifth embodiment of a gas supply system is schematically shown;

[0026] Figure 6 A condenser is schematically shown.

[0027] In principle, identical parts are provided with the same reference numerals in the Figures. DETAILED DESCRIPTION

[0028] Figure 1A gas supply system 1 is shown for supplying gas, preferably methane, to a high-pressure gas injection engine 2, preferably a ME-GI engine. The gas is stored in an LNG tank 3, partly as liquefied petroleum gas (LPG) F1 and partly as evaporated gas F2 due to the evaporation of LPG F1 occurring in the LNG tank 3. This evaporated gas F2 is also referred to as BOG or NBOG (natural evaporated gas). To supply the high-pressure gas injection engine 2 with gas having an absolute pressure in, for example, the range of 150-300 bar, the LPG F1 located in the LNG tank 3 is sent to a high-pressure pump 5 via a low-pressure pump 4 and a low-pressure fluid line 16a. This pump increases the pressure of the LPG F1 to a high pressure, for example, in the range of 150-300 bar. This high-pressure liquefied gas is then fed to a high-pressure evaporator 7 via high-pressure fluid line 17a, high-pressure heat exchanger 13, and high-pressure fluid line 17b. The evaporator evaporates the high-pressure liquefied gas into a gaseous or supercritical high-pressure gas, which, in the illustrated embodiment, has an absolute pressure of approximately 300 bar, and is then fed to a high-pressure gas injection engine 2. The illustrated gas supply system 1 also includes a condenser 6 with an inner cavity 6d, in which the liquefied gas F1 and the evaporated gas F2 are located, at least during operation of the gas supply system. The evaporated gas F2 is fed from the LNG tank 3 to a compressor 9 via gas line 15a, which compresses the evaporated gas F2. The compressed evaporated gas F2 is then introduced into the inner cavity 6d of the condenser 6 via gas line 15c and subsequently via an inlet unit 15d. The gas supply system 1 also includes a condensation nucleus generator 10, which is fed with the high-pressure liquefied gas by a high-pressure pump 5 via a side stream 18a or via a high-pressure fluid line. The nucleus generator 10 and the inlet unit 15d are arranged in such a coordinated manner within the condenser 6 that the liquid nuclei 10a and liquefied gas droplets generated by the nucleus generator 10 and injected into the inner cavity 6d promote the condensation of the introduced evaporative gas F2 within the condenser 6. This causes the evaporative gas F2 to accumulate on the nuclei and condense into liquefied gas F1, which then accumulates in the lower region of the condenser 6. This accumulated liquefied gas F1 in the condenser 6 is then fed to the high-pressure pump 5 via the outlet 6e and the return line 21, or, as... Figure 3 As shown, the gas is selectively fed to high-pressure pump 5 and / or LNG tank 3. (As indicated) Figure 1It is shown that the high-pressure heat exchanger 13 is arranged within or inside the condenser 6 to cool and at the same time condense the contents of this condenser 6, in particular the evaporated gas F2 located therein, by indirect heat exchange. Thus, the supercritical high-pressure liquefied gas flowing through the heat exchanger 13 has the function of a radiator. The compressor 9 is designed, for example, as a piston compressor, for example as a labyrinth piston compressor, and is designed, for example, as a two- or three-stage piston compressor, wherein at least one piston compressor, preferably the first piston compressor arranged downstream of the LNG tank 3, is designed as a labyrinth piston compressor. However, the compressor or at least one compressor stage can also be designed as a turbine compressor or other compressor technology.

[0029] The gas supply system 1 can furthermore optionally comprise a low-pressure fluid line 16b and a valve 25a to feed at least part of the flow of liquefied gas Fl delivered by the low-pressure pump 4 to a low-pressure evaporator 12, which evaporates the liquefied gas Fl into a gaseous low-pressure gas at an absolute pressure in the range of, for example, 7 to 9 bar. This low-pressure gas is introduced into a low-pressure consumer 11, for example a gas generator or a boiler.

[0030] Figure 6 An embodiment of the condenser 6 is shown in detail as it can be used in a gas supply system 1 according to Figure 1 The evaporated gas F2 is introduced into the inner chamber of the condenser 6 via the gas line 15c and the introduction unit 15d at the top. A side stream of high-pressure liquefied gas is injected into the inner chamber 6d of the condenser 6 via the high-pressure fluid line and the condensation nucleus generator 10 and forms a multitude of liquid droplets 10a which serve as condensation nuclei. The return line 21 is connected to the inner chamber of the condenser 6 below to remove the liquefied gas Fl located in the area below the inner chamber. The high-pressure heat exchanger 13 extends in the inner chamber 6d of the condenser 6, preferably in vertical direction from bottom to top, wherein high-pressure liquefied gas is fed in via the high-pressure fluid line 17a and removed via the high-pressure fluid line 17b. Advantageously, as Figure 4 It is shown that the majority of the high-pressure heat exchanger 13, for example 9 / 10, extends within the part of the inner chamber 6d in which the evaporated gas F2 or the mixture of evaporated gas F2 and liquid droplets of liquefied gas Fl is located.

[0031] The condenser 6 can be operated during operation, for example, with the following method. High-pressure liquefied gas is fed to the high-pressure heat exchanger 13 at an absolute pressure of 300 bar and leaves this heat exchanger again at substantially the same pressure. Evaporation gas F2 is fed from above via the introduction unit 15d into the interior space 6d of the condenser 6 at an absolute pressure of 17 bar and a temperature of +40°C. The evaporation gas F2 flowing downward from the introduction unit 15d is cooled in the interior of the condenser 6 by the high-pressure heat exchanger 13, so that a condensation portion 6a is formed between the surface 6b of the liquefied gas Fl and the boundary region 6c, in which region the evaporation gas F2 has a temperature (taking into account the pressure in the interior space 6d) which is lower than the evaporation temperature of the liquefied gas Fl. Condensation nuclei in the form of liquefied gas droplets 10a produced by the condensation nucleus generator 10 are preferably sprayed into the condensation portion 6a, so that the evaporation gas F2 located in this portion condenses on these condensation nuclei and is then guided via the surface 6b into the partial volume 6e of the condenser 6 which contains the liquefied gas Fl. In the method embodiment described here, the liquefied gas Fl has a pressure of 17 bar absolute and a temperature of -120 degrees Celsius in the partial volume 6e.

[0032] The method for operating the gas supply system 1 will be explained in detail in accordance with the following example. In contrast to a liquefied gas tanker, whose cargo space is mainly composed of LNG tanks, a conventional merchant ship has relatively small liquefied gas tanks, since the cargo space is provided for the goods to be transported. The high-pressure gas injection engine 2 of such a merchant ship has a gas requirement of, for example, about 10 tons / hour (T / h) during the voyage. The boil-off rate (BOR) is calculated in the LNG tank of the merchant ship, so that the amount of liquefied gas evaporates to, for example, about 800 kilograms / hour (kg / h) of evaporation gas F2. On the one hand, the high-pressure gas injection engine 2 has the task of supplying the high-pressure gas injection engine 2 with different, however sufficient, amounts of high-pressure gas depending on the load. Furthermore, the gas supply system 1 has the task of monitoring the gas pressure in the LNG tank 3 and ensuring that the gas pressure does not exceed a predetermined value. Furthermore, the gas supply system 1 ensures the task of using the excess evaporation gas located in the LNG tank in an economically and ecologically advantageous manner and, in particular, to supply the high-pressure gas injection engine 2 with fuel and, if necessary, to supply the low-pressure consumers 11 with fuel.

[0033] The liquefied gas Fl, which is located in the LNG tank 3, is stored at approximately atmospheric pressure and at a temperature of approximately -163°C, is fed with the aid of the low-pressure pump 4 to the high-pressure pump 5 and is compressed there at a temperature of -150°C (degrees Celsius) at a pressure of approximately 7 bar absolute pressure. In order to supply the high-pressure gas injection engine 2 with sufficient high-pressure gas, the liquefied gas Fl is then compressed in the high-pressure pump 5 at a delivery temperature of -150 degrees Celsius at a pressure of 300 bar absolute pressure into high-pressure liquefied gas and is then vaporized in the high-pressure evaporator 7 into gaseous or supercritical high-pressure gas. The high-pressure gas produced in this way is fed to the high-pressure gas injection engine 2. The delivery quantity of the high-pressure gas can be adjusted by manipulating the delivery quantity of the high-pressure pump 5 and, if necessary, the low-pressure pump 4.

[0034] The boil-off gas F2 is discharged from the tank 3 at approximately atmospheric pressure and at a temperature of approximately -162°C and is then compressed in the compressor 9 at a pressure of approximately 18 bar absolute pressure at an outlet temperature of +40°C. The thus compressed boil-off gas F2 is preferably introduced into the interior space 6d of the condenser 6 at this pressure and temperature.

[0035] As Figure 6 It is shown that the high-pressure liquefied gas, which is located in the high-pressure heat exchanger 13, flows upwards inside the condenser 6 at a pressure of 300 bar absolute pressure and at a delivery temperature of -150 degrees Celsius, so that the compressed boil-off gas F2 is introduced into the interior space 6d of the condenser 6 from above and flows downwards along the high-pressure heat exchanger 13 in the upper part of the condenser 6 and the compressed boil-off gas F2 thus flows counter-currently to the high-pressure liquefied gas flowing in the high-pressure heat exchanger 13, whereby the boil-off gas F2 is cooled and preferably cooled to its condensation temperature. The boil-off gas F2 has a boiling point temperature of approximately -110 degrees Celsius at a pressure of 17 bar absolute pressure. In order to achieve complete re-liquefaction of the boil-off gas F2 in the condenser 6, the high-pressure heat exchanger 13 or the high-pressure gas flowing therein must have sufficient potential energy to take over the enthalpy at a temperature of less than -110 degrees Celsius. In view of the necessary degree of super-saturation for condensation at 17 bar, the actual condensation temperature is approximately 5 to 10 Kelvin (K) below the boiling point temperature of 17 bar, so that condensation takes place at approximately -120°C.

[0036] The supercritical high-pressure gas or high-pressure liquefied gas with a temperature of -150 degrees Celsius enters the high-pressure heat exchanger 13 on the high-pressure side and is not directly used for heat transfer, since the heat transfer through the supercritical high-pressure gas and the wall of the high-pressure heat exchanger 13 must take into account a plurality of temperature gradients. As a first approach, it is assumed that the wall temperature of the high-pressure heat exchanger 13 on the side facing the boil-off gas F2 is -145°C. This allows the transfer of enthalpy energy from the boil-off gas F2 to the supercritical high-pressure gas or high-pressure liquefied gas to be achieved within a temperature window of 25° K.

[0037] To improve the efficiency of the re-liquefaction of the boil-off gas F2 into liquefied gas Fl in the condenser 6, a condensation nucleus generator 10 is used to generate liquefied gas droplets that serve as condensation nuclei, which are sprayed into the inner chamber 6d of the condenser 6. To this end, a part of the high-pressure liquefied gas Fl compressed by the high-pressure pump 5 is fed in a side stream 18a to the condensation nucleus generator 10, wherein the supplied high-pressure liquefied gas has a pressure of 300 bar absolute and a temperature of -150°C. The liquefied gas droplets in the condensation nucleus generator 10 are sprayed into the inner chamber 6d of the condenser 6. The droplets 10a generated in the condensation nucleus generator 10, for example by the aid of at least one nozzle, are guided into the condensation section 6a of the condenser 6, in which section the temperature of the boil-off gas F2 has already fallen below its condensation temperature of -110°C. The liquefied gas droplets 10a entering the condenser 6 are thus also subcooled, since the condensation temperature of the boil-off gas F2 is 110°C at an absolute pressure of 17 bar.

[0038] The subcooled liquefied gas droplets 10a serve as condensation nuclei for the boil-off gas F2 to be condensed. This means that each subcooled liquefied gas droplet 10a attracts gas molecules from the boil-off gas F2 to be condensed. The condensation of the boil-off gas F2 on the liquefied gas droplets 10a is more efficient than the condensation at the outer wall of the high-pressure heat exchanger 13 for the following reasons:

[0039] - The liquefied gas droplets are subcooled at -150°C, whereby a greater potential energy for attracting gas molecules of the boil-off gas F2 is created due to the greater temperature difference.

[0040] - The specific surface area of the liquefied gas droplets is greater than the comparable surface area of the outer wall of the high-pressure heat exchanger 13, since the area of a sphere is π times greater than the area of a plane or curved surface.

[0041] Figure 2 and Figure 3 A further embodiment of the gas supply system 1 is shown, wherein, in contrast to the embodiment according to Figure 1 the heat exchanger 8 is arranged in the boil-off gas flow after the boil-off gas F2 has been discharged from the LNG tank 3, which heat exchanger serves for further cooling of the high-pressure liquefied gas after the high-pressure pump 5 and before entering the condensation nucleus generator 10. Thereby, the boil-off gas F2 flowing in the gas line 15a, suction duct 15b is heated in the heat exchanger 8. The heat exchanger 8 is preferably supplied with a side stream 18a of high-pressure liquefied gas, wherein the side stream 18a downstream of the high-pressure pump 5 or the high-pressure pump 5 is discharged from the high-pressure fluid line 17a, guided into the heat exchanger 8 and in turn preferably into the condensation nucleus generator 10. The heat exchanger 8 is preferably as Figure 2 is shown arranged upstream of the compressor 9.

[0042] It is important for the gas supply system 1 according to the invention that the supply of Figure 6The evaporated gas F2 in the condenser 6 shown is condensed in the inner cavity 6d of the condenser 6. Those skilled in the art will generally know that... Figures 1-5 The gas supply system 1 shown includes, for example, control devices (not shown) for operating the low-pressure pump 4, high-pressure pump 5, compressor 9, and valves 25a-25g, and multiple signal lines, including multiple signal lines and sensors, for example, for acquiring the pressure and / or temperature of the liquefied gas F1 and evaporative gas F2 flowing through the gas supply system 1 at different locations, and the pressure of the high-pressure liquefied gas and high-pressure gas at different locations. Therefore, those skilled in the art can readily understand, based on the content of this invention, what control options and parameter optimizations the gas supply system 1 according to the invention can provide to advantageously operate the gas supply system 1 according to the invention, and in particular ensure advantageously, preferably energy-efficiently, condensation in the condenser 6. Thus, for example, from Figure 1 It can be readily deduced that the condensation of the evaporating gas F2 in the condenser 6 is affected by the amount of evaporating gas F2 supplied by the compressor 9, and, where necessary, its temperature, and / or by the amount of high-pressure liquefied gas supplied to the nucleus generator 10 by the side streams 18a, 18b, and especially its temperature, and / or by the size and number of condensation nuclei 10a generated by the nucleus generator 10, and / or by the arrangement and orientation of the liquefied gas droplets 10a flow in the inner cavity 6d of the condenser 6, and / or by the arrangement and design of the high-pressure heat exchanger 13 in the inner cavity 6d of the condenser 6. Furthermore, the temperature of the liquefied gas droplets 10a injected into the inner cavity 6d, and / or the temperature difference between the introduced evaporating gas F2 and the droplets 10a, can be influenced by... Figures 2-5 The use, clever arrangement, and design of the heat exchanger 8 shown are influenced by this. Therefore, those skilled in the art, based on the disclosed concept of the invention and their expertise, can simply select the method parameters such that the gas supply system can operate in an economically advantageous manner, and especially in an energy-saving manner, and that the condensation method occurring particularly in the condenser 6 has a high condensation rate.

[0043] Figure 3In another embodiment a gas reservoir 14 is shown, which is connected via controllable valves 25d, 25e with the gas lines 15a, 15c. This gas reservoir 14 is used, among other things, to accommodate boil-off gas F2 during time periods in which the high-pressure gas injection engine 2 does not require fuel, for example because the ship is stationary. During this time period, no high-pressure liquefied gas is directed to the high-pressure gas injection engine 2, so that the high-pressure liquefied gas in the heat exchanger 13 in the condenser 6 is not used as a heat sink, and therefore no cooling takes place in the condenser 6, so that condensation stagnates in the condenser 6. However, during the stationary state of the ship, boil-off gas F2 is still accumulating in the LNG tank 3, which must be removed from the LNG tank 3 to prevent an undesirable pressure rise in the LNG tank 3. The gas reservoir 14 is particularly advantageous during this time period, because the boil-off gas F2 can be transported via the compressor 9 to the gas reservoir 14, can be temporarily stored there, and can then be removed from the gas reservoir 14 during the voyage of the ship or during the time in which high-pressure liquefied gas is directed to the high-pressure gas injection engine 2 and can be liquefied in the condenser 6.

[0044] The gas reservoir 14 is advantageously filled with a high-porosity solid, such as an adsorbent or a metal hydride, or a fluid solvent, whereby the storage capacity of the gas reservoir 14 is greatly increased at the same pressure and temperature compared to an empty container. If the gas reservoir 14 is not in storage operation or is empty, it is connected to the suction line 15b of the compressor 9 by opening the valve 25d and closing the valve 25e. If the gas reservoir 14 is in storage mode, it is connected to the pressure line 15c downstream of the compressor 9 by opening the valve 25e and closing the valve 25d. It can also be advantageous to direct at least a portion of the boil-off gas F2 to the low-pressure consumer 11 via the fluid line 15e, wherein a controllable valve 25c is preferably provided, and a controllable valve 25b is preferably provided in order to control the gas flow to the low-pressure consumer 11 and, if necessary, to control the distribution of the total amount between the condenser 6 and the low-pressure consumer 11. It can also be advantageous to controllably direct the liquefied gas F1 flowing from the interior space 6d of the condenser 6 via the return line 21 to the LNG tank via the valve 25f of the high-pressure pump 5 and / or via the valve 25g.

[0045] Figure 4 A further embodiment of the gas supply system 1 is shown, in which the boil-off gas F2 is fed to the heat exchanger 8 downstream of the tank 3, is then compressed in the compressor 9 to compressed boil-off gas F2, wherein the compressed boil-off gas F2 is again fed to the heat exchanger 8, so that the compressed boil-off gas F2 in the heat exchanger 8 is strongly cooled, and after this cooling, is fed to the condenser 6 via the feed unit 15d. This compressed and strongly cooled boil-off gas F2 has the advantage that it is condensed better or more easily and thus more energy-efficiently in the condenser 6.

[0046] Figure 5Another embodiment of the gas supply system 1 is shown, which is identical to the embodiment according to Figure 3 The difference of the shown embodiment is that there are two separate high pressure pumps 5, namely a first high pressure pump 5a and a second high pressure pump 5b, and two separate high pressure fluid lines 17a, 17c connected thereto. Furthermore, according to Figure 5 the embodiment differs from the embodiment according to Figure 3 that there is no valve 25g in the return line 21 and thus no return to the tank 3. According to Figure 5 the embodiment is preferably operated such that the liquefied gas Fl from the tank 3 is only introduced into the first high pressure pump 5a and compressed to high pressure liquefied gas in the first high pressure pump 5a. As Figure 5 shown, this high pressure liquefied gas is introduced into the high pressure heat exchanger 13 and then into the high pressure evaporator 7. In an advantageous method, the liquefied gas Fl, which is essentially condensate, located in the condenser 6, is fed to the second high pressure pump 5b and compressed to high pressure liquefied gas in the second high pressure pump 5b, wherein this high pressure liquefied gas is bypassed around the condenser 6 and supplied to the high pressure fluid line 17b and / or directly into the high pressure evaporator 7. This arrangement or this method has the advantage that the liquefied gas Fl discharged from the LNG tank 3 is not heated by the condensate or liquefied gas Fl produced in the condenser 6 or the liquefied gas Fl returned in the low pressure fluid line 16a. Thus, this embodiment has the advantage that the condensation in the condenser 6 has a higher efficiency or a higher degree of effectiveness. In another possible method, the second high pressure pump 5b or can introduce only the condensate or liquefied gas Fl from the condenser 6 via the valve 25f or can deliver only the liquefied gas Fl from the tank 3 via the valve 25g or can deliver a mixture containing a portion of the liquefied gas Fl from the condenser 6 and a portion of the liquefied gas Fl from the tank 3 by corresponding actuation of the two valves 25f, 25g. The mixing ratio of these two portions of liquefied gas Fl can be varied depending on the operating point of the gas supply system 1, for example in order to optimize the efficiency of the gas supply system 1, for example depending on the amount of high pressure gas required by the high pressure gas injection engine 2.

Claims

1. A gas supply system (1) for supplying a gas stored in a liquefied gas tank (3) to a high-pressure gas injection engine (2), comprising a high-pressure pump (5) which can be connected in fluid communication with the liquefied gas tank (3) to supply liquefied gas (Fl) from the liquefied gas tank (3) and to compress it to high-pressure liquefied gas, comprising a condenser (6) in which a high-pressure heat exchanger (13) is arranged, comprising a high-pressure evaporator (7) which is connected in fluid communication with the high-pressure pump (5) via the high-pressure heat exchanger (13) and is arranged downstream of the condenser (6), wherein the high-pressure evaporator (7) converts the high-pressure liquefied gas into high-pressure gas, and the high-pressure gas is fed to the high-pressure gas injection engine (2) located downstream of the high-pressure evaporator (7), comprising a compressor (9) which can be connected in fluid communication with the liquefied gas tank (3) to supply evaporated gas (F2) from the liquefied gas tank (3), wherein the compressor (9) is connected in fluid communication downstream via a lead-in unit (15d) to an inner chamber (6d) of the condenser (6) to lead the evaporated gas (F2) into the inner chamber (6d), and comprising a condensation nucleus generator (10) which is connected in fluid communication upstream to the high-pressure pump (5), wherein the condensation nucleus generator (10) is designed in such a way that it generates from the high-pressure liquefied gas liquefied gas droplets (10a) which act as condensation nuclei, wherein the condensation nucleus generator (10) leads the condensation nuclei into the inner chamber (6d) to promote condensation of the led-in evaporated gas (F2) by the condensation nuclei, so that liquefied gas (Fl) is formed therefrom, and the liquefied gas (Fl) formed in the condenser (6) is led into the high-pressure pump (5) and / or the liquefied gas tank (3).

2. The gas supply system (1) according to claim 1, characterized in that A heat exchanger (8) is arranged upstream of the compressor (9), which heat exchanger exchanges heat with the supplied evaporated gas (F2), and the condensation nucleus generator (10) can be connected in fluid communication upstream to the heat exchanger (8) and is connected immediately to the high-pressure pump (5), so that the heat exchanger (8) exchanges heat with the supplied high-pressure liquefied gas.

3. The gas supply system (1) according to claim 1, characterized in that A heat exchanger (8) is arranged upstream of the compressor (9), which heat exchanger exchanges heat with the supplied evaporated gas (F2), and wherein the compressor (9) is connected in fluid communication upstream to the heat exchanger (8), so that the heat exchanger (8) exchanges heat with the evaporated gas (F2) compressed by the compressor (9).

4. The gas supply system (1 ) according to any one of claims 1 to 3, characterized in that The evaporated gas (F2) enters the condenser (6) from above via the lead-in unit (15d), the high-pressure heat exchanger (13) extends in the vertical direction inside the condenser (6), and the high-pressure heat exchanger (13) is arranged in such a way that the high-pressure liquefied gas flows from bottom to top in the high-pressure heat exchanger (13).

5. The gas supply system (1 ) according to any one of claims 1 to 3, characterized in that The condensation nucleus generator (10) has at least one high-pressure nozzle, which high-pressure nozzle has a diameter in the range from 1 to 1000 micrometers.

6. The gas supply system (1) according to claim 5, characterized in that The high-pressure nozzle has a diameter in the range from 5 to 500 micrometers.

7. The gas supply system (1 ) according to any one of claims 1 to 3, characterized in that The condensation nucleus generator (10) is arranged in such a way that the condensation nuclei (10a) generated by the condensation nucleus generator (10) are led into a condensation section (6a) in the inner chamber (6d) of the condenser (6), wherein the inner chamber (6d) has a condensation temperature.

8. The gas supply system (1) according to any one of claims 1 to 3, wherein the condensation nuclei generator (10) is arranged such that the condensation nuclei enter the inner chamber (6d) of the condenser (6) along the cooling duct of the first half of the high-pressure heat exchanger (13) in the flow direction of the liquefied gas (Fl).

9. The gas supply system (1) according to claim 8, wherein the condensation nuclei enter the inner chamber (6d) of the condenser (6) along the cooling duct of the first third of the high-pressure heat exchanger (13) in the flow direction of the liquefied gas (Fl).

10. The gas supply system (1 ) according to any one of claims 1 to 3, characterized in that A storage container (14) for temporarily storing the boil-off gas (F2) is arranged downstream of the liquefied gas tank (3).

11. The gas supply system (1) according to any one of claims 1 to 3, characterized in that The high-pressure pump (5) comprises at least a first high-pressure pump (5a) and a second high-pressure pump (5b), wherein the first high-pressure pump (5a) is connected in fluid communication with the condensation nuclei generator (10) and with the high-pressure evaporator (7) via the high-pressure heat exchanger (13), and wherein the second high-pressure pump (5b) is connected in fluid communication with the high-pressure evaporator (7) bypassing the high-pressure heat exchanger (13).

12. The gas supply system (1) according to claim 11, characterized in that The first high-pressure pump (5a) is connected in fluid communication with the liquefied gas tank (3) for supplying the liquefied gas (Fl) and the second high-pressure pump (5b) is connected in fluid communication with the outlet (6e) of the condenser (6) for conducting the liquefied gas (Fl) accumulated in the condenser (6) into the second high-pressure pump (5b).

13. The gas supply system (1) according to claim 12, characterized in that The second high-pressure pump (5b) is connected in fluid communication both with the outlet (6e) of the condenser (6) and with the liquefied gas tank (3), wherein valves (25f, 25g) are provided to control the portion of the liquefied gas (Fl) supplied from the condenser (6) and the portion of the liquefied gas (Fl) supplied from the liquefied gas tank (3).

14. A method for supplying a high-pressure gas injection engine (2) with gas stored in a liquefied gas tank (3) as a mixture of liquefied gas (Fl) and boil-off gas (F2), wherein the liquefied gas (Fl) is supplied from the liquefied gas tank (3) to a high-pressure pump (5) and is compressed by the high-pressure pump to high-pressure liquefied gas, wherein the high-pressure liquefied gas is then conducted to a high-pressure heat exchanger (13) arranged in a condenser (6) and subsequently to a high-pressure evaporator (7), wherein the high-pressure liquefied gas is converted in the high-pressure evaporator (7) to high-pressure gas, so that gas in a high-pressure state is produced by conducting the boil-off gas (F2) from the liquefied gas tank (3) to a compressor (9) and subsequently to the condenser (6) for conducting into the high-pressure gas injection engine (2), wherein condensation nuclei in the form of liquefied gas droplets are generated from the high-pressure liquefied gas in a condensation nuclei generator (10), the condensation nuclei stream is conducted in the condenser (6) to the boil-off gas (F2) that has been conducted, in order to promote the condensation of the boil-off gas (F2) to liquefied gas (Fl) by the liquefied gas droplets, and the liquefied gas (Fl) formed in the condenser (6) is conducted to the high-pressure pump (5) and / or to the liquefied gas tank (3).

15. The method according to claim 14, wherein a flow of condensation nuclei in the form of liquefied gas droplets is generated in the condensation nuclei generator (10) and is fed to the introduced evaporated gas (F2) in the condenser (6) in a mass flow of 1-5% of the mass flow of the gas to be condensed.

16. The method according to claim 14 or 15, characterized in that In the condenser (6), the liquefied gas (Fl) is transported from bottom to top in the high-pressure heat exchanger (13), while the evaporated gas (F2) is transported in the condenser (6) in the opposite direction from top to bottom.

17. The method of claim 14 or 15, wherein, A condensation section (6a) is formed in the inner chamber (6d) of the condenser (6), in which condensation section the evaporated gas (F2) having a temperature lower than the evaporation temperature of the liquefied gas (Fl) is present, and condensation nuclei in the form of supercooled liquefied gas droplets (10a) are sprayed into the condensation section (6a).

18. The method according to claim 17, wherein a temperature of -140 degrees Celsius to -80 degrees Celsius and an absolute pressure of 5 to 30 bar are present in the formed condensation section.

19. The method according to claim 18, wherein a temperature of -120 degrees Celsius to -100 degrees Celsius and an absolute pressure of 10 to 20 bar are present in the formed condensation section.

20. The method of claim 14 or 15, wherein, a side stream is tapped off from the high-pressure pump (5) or downstream of the high-pressure pump, wherein the side stream is cooled in the heat exchanger (8), the evaporated gas (F2) is simultaneously heated in the heat exchanger (8) from the liquefied gas tank (3), wherein the evaporated gas (F2) is introduced into the condenser (6) downstream of the heat exchanger (8) and the high-pressure liquefied gas is introduced into the condensation nuclei generator (10) downstream of the heat exchanger (8).

21. The method of claim 14 or 15, wherein, The high-pressure liquefied gas is compressed to an absolute pressure in the range of 150 bar to 400 bar.

22. A merchant ship comprising a gas supply system (1) according to any one of claims 1-13.

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