RU2773583C2 - Device and method for supplying gas with methane number optimized for at least one heat engine, in particular, of vessel for transportation of liquefied gas - Google Patents

Abstract

FIELD: refrigeration equipment.

SUBSTANCE: device (10) and method are designed to supply gas with a methane number optimized for heat engine (12), in particular, of a vessel for the transportation of liquefied gas. Pump (16) is designed to sink to the bottom of tank (14) for the storage of liquefied gas, and it contains outlet (16a) for gas in a liquid form. Evaporator (18) contains the first circuit having inlet (18aa), it is connected to the outlet of the pump, and it additionally contains outlet (18ab) for gas in a liquid form and gas in a gaseous form. Phase separator (20) contains inlet (20a) connected to the specified outlet of the evaporator and two outlets (20b, 20c), including first outlet (20c) for gas in a liquid form and second outlet (20b) for gas in a gaseous form. Heater (22) has the first circuit containing inlet (22a) connected to the outlet of the separator and outlet (22b) for heated gas in a gaseous form to be supplied to the engine. Device (10) contains tank (44) for the storage of gas in a liquid form, first inlet (44a) of which is connected to first outlet (20c) of the specified separator. Tank (44) includes outlet (44b, 44c) made with the possibility of supplying a medium for cooling line (45) for liquefied gas circulation and/or feeding burner (52).

EFFECT: supply of an engine with gas having an optimal methane number.

17 cl, 5 dwg

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

The invention relates to a device and method for supplying gas with a methane number, optimized for at least one heat engine, in particular, a ship for transporting liquefied gas.

PRIOR ART

A ship for the transport of liquefied gas, such as liquefied natural gas (LNG), is equipped with main and auxiliary engines, which are internal combustion engines that run on fuel and, in particular, fuel gas. The fuel gas used to power these engines is obtained from the transported liquefied gas.

Liquefied gas contains heavy gases and light gases, with heavy gases having a higher molecular weight than light gases and having a higher evaporation temperature than light gases. As an example, methane is a light gas having an evaporation temperature of about -160°C at atmospheric pressure, and n-butane is a heavy gas having an evaporation temperature of about 0°C at atmospheric pressure.

It is known that the preferred methane number of a fuel gas intended to power engines should be as high as possible in order to avoid knocking (or lapping) problems in engines. To this end, the fuel gas must have the highest possible concentration of light gases.

In practice, the methane number of the fuel gas must be suitable for the operating conditions of the engines and therefore may change over time.

The present invention proposes an improvement to existing technology that allows at least one engine to be supplied with a gas having an optimum methane number.

SUMMARY OF THE PRESENT INVENTION

The invention provides a device for supplying a gas with an optimized methane number to at least one internal combustion engine, in particular an LPG transport vessel, characterized in that it includes at least

- a pump designed to be immersed in the bottom of a tank for storing liquefied gas and having an outlet for gas in liquid form;

- an evaporator including a first circuit including an inlet connected to a pump outlet and further including an outlet for gas in liquid form and gas in gaseous form;

a phase separator including an inlet connected to said outlet of the evaporator and further including two outlets comprising a first outlet for gas in liquid form and a second outlet for gas in gaseous form.

In accordance with the first aspect of the present invention, the device further includes

a heater including a first circuit including an inlet connected to a second separator outlet and an outlet for heated gas in gaseous form to power at least one engine.

In order to increase the methane number in the gas to be supplied to the engine or engines, the invention therefore proposes to carry out phase separation of the liquefied gas and then store the gas in a gaseous form which is rich in light gases and therefore has a high methane number. Phase separation is initiated in the evaporator, which allows the liquefied gas to be heated to a temperature sufficient to vaporize light gases, but not heavy gases. The mixture is then introduced into a separator where the liquid and gaseous phases are separated. The gas in gaseous form, containing light gases, is heated in a heater before being fed into the engine or engines. This heating is necessary because the temperature of the liquefied gas in the storage tank is very low (approximately -160°C) and the gas remains cold in the evaporator and separator (below 0°C). Thus, evaporation and separation occur at low temperatures, which are determined to optimize phase separation and ensure evaporation of light, and only light, gases. Thereafter, the heater suitably performs the function of heating the gas in gaseous form to a temperature ideal for the operation of the engine or engines, for example greater than 0°C.

In this application, "light gas" refers to a gas having a molecular weight of less than 28 g/mol (for example, methane, nitrogen and ethane), and "heavy gas" refers to a gas having a molecular weight of more than 28 g/mol (eg propane, butane, pentane and other hydrocarbons).

The device according to the present invention may have one or more of the following features, either alone or in combination with each other:

said evaporator has a heat exchanger and/or an expansion valve;

said separator has a heat exchanger and/or an expansion valve;

said evaporator includes a second circuit for circulating a heat carrier, such as glycol or steam;

- the outlet of the first circuit of the evaporator is connected to the first inlet of the mixer, which further includes a second inlet connected to the outlet of the pump, and an outlet connected to the inlet of the separator;

- the device includes means for controlling the temperature of the liquefied gas in the evaporator and/or in the separator to optimize evaporation and/or phase separation;

said temperature control means is connected to a valve connected to an inlet of said second evaporator circuit;

said temperature control means is connected to a valve connected to the second inlet of the mixer;

said temperature control means is connected to at least one temperature sensor installed in said separator;

said temperature control means is connected to a means for controlling the methane number of the gas at the outlet of said heater;

said methane number control means is configured to control said temperature control means and obtain data relating to the liquefied gas and operating parameters of said at least one engine;

the device further includes a gas storage tank in liquid form, the first inlet of which is connected to the first outlet of said separator;

said tank includes at least one outlet configured to supply a medium for cooling the liquefied gas circulation line and/or at least one burner;

- said at least one outlet of said tank is connected to the burner by means of a valve and/or a heater;

- the device includes a compressor, including an inlet for connection with an outlet for gas in gaseous form contained in said tank, and an outlet for compressed gas;

- the specified outlet for compressed gas is connected to the outlet of the specified heater to power at least one engine;

said compressed gas outlet is connected to a second inlet of said tank;

said tank includes a second inlet connected to pressurized nitrogen supply means.

The present invention also relates to a method for supplying a gas with an optimized methane number to at least one internal combustion engine, in particular an LPG transport vessel, using the apparatus described above, characterized in that

- liquefied gas is pumped out by means of a pump at a temperature not exceeding or equal to -160°C;

- the pumped liquefied gas is heated in the evaporator to a temperature of -130 to -10°C inclusive, and preferably from -100 to -40°C inclusive, in order to evaporate some gases, called light gases, and other gases, called heavy gases, remaining in liquid form;

- liquid and gaseous phases are separated in the separator; and then

- the gas in gaseous form coming from the separator is heated to a temperature exceeding 0°C, and, for example, about 20°C.

Preferably:

- liquefied gas is pumped out by a pump under pressure from 7 to 12 bar inclusive and is, for example, 8 bar;

- the pressure in the evaporator is from 6 to 10 bar inclusive and is, for example, 7 bar;

- the pressure in the separator is from 5 to 7 bar inclusive and is, for example, 6.2 bar; as well as

- the pressure in the heater is from 5 to 7 bar inclusive and is, for example, 6 bar.

The pressure in the tank is between 1 and 10 bar inclusive and is, for example, 2 bar.

In accordance with the second aspect of the present invention, the device further includes

- bypass means, including an outlet for gas in gaseous form, designed to power at least one engine, and at least one inlet connected to the inlet of the separator and / or outlet for gas in gaseous form the shape of the specified tank.

Natural evaporation takes place in the LPG storage tank. Gases that evaporate naturally are the lightest gases because they have the lowest evaporation temperatures. In other words, the gases produced by the natural evaporation of liquefied gas have a high methane number and are particularly suitable for direct use, perhaps if heated, as fuel for an engine or engines.

The bypass means may comprise at least a valve and/or a compressor.

The apparatus may include a heat exchange type heater including a first circuit including an inlet connected to a compressor outlet and further comprising an outlet for heated gas in gaseous form to power at least one engine. Alternatively, a heater may be built into the compressor.

This device may have some or all of the functions of the device in accordance with the first aspect of the present invention.

According to a third aspect of the present invention, the device further includes

- a tank for storing gas in liquid form, the first inlet of which is connected to the first outlet of the specified separator, and the specified tank contains at least one outlet, made with the possibility

подачи среды для охлаждения линии циркуляции сжиженного газа; и/или

medium supply for cooling the liquefied gas circulation line; and/or

питания по меньшей мере одной горелки.

supply of at least one burner.

This device may have some or all of the functions of the device in accordance with the first and/or second aspects of the present invention.

In accordance with another aspect, the invention provides a method for adjusting the methane number of a gas for supply to at least one internal combustion engine, in particular a vessel for transporting liquefied gas, characterized in that it comprises the following steps

- selection of liquefied gas;

- partial evaporation of liquefied gas in order to produce gas in gaseous form, including light gases from liquefied gas, heavy gases from liquefied gas remaining in liquid form,

wherein the methane number of the gas in gaseous form is controlled by controlling the temperature at which vaporization occurs.

In this case, the evaporation is forced, in contrast to the natural evaporation that occurs at the liquid/gas interface in the LPG storage tank.

The method according to the present invention may have one or more of the following features and include one or more of the following steps, existing separately from each other or in combination with each other

- the temperature is controlled by changing the flow rate at which the heat transfer fluid is supplied to the evaporator circuit, configured to perform said evaporation;

- the temperature is controlled by mixing the liquefied gas after partial evaporation with the selected liquefied gas, which has not undergone partial evaporation;

- the temperature is controlled depending on the temperature of the gas in gaseous form;

- the temperature is controlled depending on the data relating to the liquefied gas and/or the operating parameters of at least one of the specified engine.

BRIEF DESCRIPTION OF THE FIGURES

The invention will be better understood and other details, features and advantages of the present invention will become more apparent upon reading the following description, given by way of non-limiting example and with reference to the accompanying drawings, in which

- fig. 1 is a schematic view of a methane number optimized gas supply device according to a first embodiment of the present invention;

- fig. 2 is a schematic view of a methane number optimized gas supply device according to a second embodiment of the present invention;

- fig. 3 is a schematic view of a methane number optimized gas supply device according to a third embodiment of the present invention;

- fig. 4 is a schematic view of a methane number optimized gas supply device according to a fourth embodiment of the present invention; and

- fig. 5 is a flowchart showing the steps of a method for adjusting the methane number of a gas for supply to at least one internal combustion engine.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, the terms "upstream" and "downstream" refer to the flow of a medium, such as a gas or liquid, in a pipe or loop.

In FIG. 1 shows a first embodiment of a device 10 for supplying gas with an optimized methane number to at least one internal combustion engine 12, in particular an LPG transport vessel. This engine 12 may be the main engine or an auxiliary engine of the vessel.

The ship includes at least one tank 14 for storing liquefied gas, such as liquefied natural gas (LNG). The tank 14 is at atmospheric pressure or under pressure. LNG is stored in a tank in liquid form at a temperature of around -160°C. LNG undergoes natural evaporation and some LNG vaporizes, so the tank also contains some gas in gaseous form.

Reference 16 denotes a pump that is immersed in LNG and therefore designed to feed LNG and not gas in gaseous form. The pump 16 is thus preferably located at the bottom of the tank.

In addition to the pump 16, the device 10 includes an evaporator 18, a separator 20 and a heater 22. Here they are connected in series one after the other, downstream of the pump 16.

The pump 16 includes an outlet 16a for LNG, that is, for gas in liquid form. The outlet 16a is connected to the inlet 18aa of the first liquid circuit of the evaporator 18, which here is a two-circuit heat exchanger. The first circuit of the evaporator 18 includes an outlet 18ab connected to an inlet 20a of the separator.

The second evaporator circuit 18 includes an inlet 18ba and an outlet 18bb and circulates a heat transfer medium such as steam or glycol. The circulation of the coolant in the secondary circuit ensures that the temperature of the LNG taken from the tank 14 is raised to a predetermined temperature that ensures partial evaporation of the LNG.

Part of the LNG containing light gases such as nitrogen, methane and ethane evaporates, while the other part of LNG containing heavy gases such as n-butane remains in liquid form. The outlet 18ab of the first evaporator circuit is thus an outlet for gas in gaseous and liquid form.

This two-phase gas mixture is fed into the separator 20 through its inlet 20a. Phase separation is the task of the separator 20, which includes an outlet 20b for gas in gaseous form and an outlet 20c for gas in liquid form containing heavy gases. The separator can be made according to classical technology, for example, honeycomb or gravity type.

The outlet 20b of the separator 20 is connected to the inlet 22a of the heater 22, the function of which is to increase the temperature of the gas in gaseous form to supply the gas with an optimized methane number to the engine 12 at a suitable temperature, and more specifically, at a temperature within the acceptable range for the engine 12 , that is, in the range from 0°C to 60°C, as indicated below.

The device 10 of FIG. 1 functions as follows. The liquefied gas is withdrawn by the pump 16 at a temperature not exceeding or equal to -160° C. and at a pressure, for example, of the order of 8 bar. The evacuated gas is heated in the evaporator 18 to -130 to -10° C. inclusive, preferably -100 to -40° C. inclusive, in order to vaporize the light gases, while the heavy gases remain in liquid form. The pressure in the evaporator 18 is between 6 and 8 bar inclusive, and is, for example, 7 bar. A mixture of phases is introduced into separator 20 to separate these phases. The pressure in the separator is between 5 and 7 bar inclusive, and is, for example, 6.2 bar. The gas in gaseous form exiting the outlet 20b is heated by the heater 22 to a temperature in excess of 0°C and, for example, of the order of 20°C. The pressure in the heater is between 5 and 7 bar inclusive, and is, for example, 6 bar. The engine 12 is thus supplied with fuel gas at a temperature between 0° C. and 60° C. inclusive, for example at 20° C. and at a pressure of, for example, 6 bar.

In FIG. 2 shows another embodiment of the device 10, which here further includes means 24 for adjusting the methane number of the gas to be supplied to the engine 12.

The control means 24 may take the form of a data processing unit including, inter alia, means for inputting, storing and backing up data, computing means, and actuators.

The control means 24 is designed to obtain information such as operating parameters 26 of the engine 12 and data 28 related to LNG, such as its composition, density, temperature, etc.

The parameters 26 describe, in particular, the operating conditions that the engine 12 must achieve. For the given operating conditions of the engine 12, there is a desired methane number for the fuel gas supplied to the engine. In addition, there are curves, or they can be obtained upstream and stored in the control means 24 to calculate the operating temperature of the evaporator 18 depending on the desired methane number and data 28 related to LNG.

Data 28 can be obtained using a chromatograph, which is an instrument capable of determining the composition of a gas or liquefied natural gas and the concentration of its components. This tool may be located in the device 10, between the LNG outlet from the tank 14 and the fuel gas inlet of the engines 12.

The means 24 is connected to a temperature control means 30, which is connected to at least one temperature sensor 32 installed, for example, in the separator 20, and in particular in the upper stage of the separator, for measuring the temperature of the gas in gaseous form.

The control means 30 may be a comparator that will receive a signal from the sensor 32 corresponding to the temperature reading and compare it with a setpoint calculated by the means 24 for signaling the means 24 for adjusting the operating temperature of the evaporator 18 and/or separator 20.

In the example shown, the valve 34 is located in the second circuit of the evaporator 18 upstream of the inlet 18ba and its flow rate is controlled by means 24, 30.

In addition, a mixer 36 is installed between the outlet 18ba and the inlet 20a. This mixer 36 includes two inlets, one of which is connected to the outlet 18ba and the other is connected to the outlet 16a of the pump 16 upstream of the evaporator 18. Another valve 38 is located upstream of the mixer inlet 36b and controls the flow rate of the liquefied gas to the mixer. The function of the mixer 36 is to mix a certain amount of liquefied gas withdrawn from the tank 14 with a certain amount of two-phase gas leaving the evaporator 18 to supply the temperature-optimized two-phase gas mixture to the separator 20. The flow rate of valve 38 is controlled by means 24, 30.

In FIG. 2 also shows an embodiment of bypass means 40, which here are configured to bypass separator 20 and heater 22.

The bypass means 40 include an inlet 40a connected to an outlet 18ab of an evaporator 18 or a mixer 36 and an outlet 40b connected to an outlet 20b of a separator 20 or an outlet 22b of a heater 22. The bypass means 40 include a flow valve 42, which is regulated by means 24, 30.

In FIG. 3 shows another embodiment of the device 10, which here includes a tank 44 for storing gas in liquid form, the first inlet 44a of which is connected to the first outlet 20c of the separator 20.

Tank 44 is designed to receive and store gas in liquid form, including heavy gases produced by partial evaporation and phase separation of the pumped LNG.

The tank, for example, is configured to store gas in liquid form at a pressure of the order of 2 to 3 bar. The temperature of the gas in the tank car can be very low and one use of this gas can be to cool the LNG circulation line. Another use of the gas contained in the tank 44 may be combustion in the burners 52 DF (dual fuel) or gas (burning gas) or boiler, for example, to produce steam used on board. This steam can be used to supply the second loop to evaporator 18 or even heater 22. The steam can be used to heat the ship's LNG storage tank so that its temperature is not too low, as this increases the viscosity of the LNG.

The tank 44 includes one or more outlets 44b, such as an outlet for cooling the LNG circulation line 45 as mentioned above. This outlet 44b is connected to a valve 46. The circulation of liquefied gas at low temperature in the pipeline ensures that this pipeline is cooled, for example, before a gas receiving operation (filling a ship's tank), to limit thermal shock during this operation.

The tank 44 includes an outlet 44c connected to a valve 48 or even a heater 50 to feed a burner or burners 52. in liquid form, which participated in the cooling of the conduit 45, and thus heated by the heat exchanger, could be used to feed the burner. This circuit is supplied with valve 54.

In FIG. 3, the embodiment further includes bypass means 56, which here are configured to bypass the evaporator 18, separator 20, and heater 22.

The bypass means 56 comprise a compressor 58 including an inlet 58a connected to an outlet 14a of a gas tank 14 (produced by natural evaporation of liquefied natural gas). Compressor outlet 58b is connected directly, or through valve 60, to heater outlet 22b for supplying natural evaporation gas to engine 12, and/or to another inlet 44b of tank 44, also directly or through valve 62. Alternatively or additionally Specifically, means 64 for supplying gas, such as pressurized nitrogen, is connected to the inlet 44d of the tank.

Supplying the tank with gas at pressure, for example in excess of 6 bar, from compressor 58 or means 64 provides a forced and enhanced flow of gas in liquid form through outlets 44b, 44c of the tank.

Valves 46, 48, 54, 60, 62 can be actuated by means 24, 30.

In FIG. 4, the embodiment combines all the features described with reference to the embodiments of FIG. 13.

Fig. 5 is a flowchart showing the steps of a method for adjusting the methane number of gas supplied to engine 12.

The ship, equipped with the engine 12, moves at a given speed, designated as V1. To achieve this speed V1, the engine 12 or main engines of the vessel must be operated under operating conditions R1. To achieve these conditions R1, the fuel gas supplied to the engine must have a minimum methane number MNm. This number MNm is transmitted by means 24 to means 30 which compares it with the current number MNa. This MNa number is calculated from 28 LNG data, such as its composition.

If MNa is greater than or equal to MNm, bypass means 40 or 56 can be used to directly feed engine 12 with natural or forced evaporation gas that already has an optimum methane number for engine operating conditions.

Otherwise, if MNa is less than MNm, the means 24, 30 obtain the temperature T1 measured by the sensor 32 and calculate the optimum operating temperature of the evaporator 18. They set this temperature so that the amount of forced evaporation gas produced in the evaporator is the required minimum of in relation to the required methane number. In practice, during iterations, the temperature T1 is repeatedly measured and adjusted until the fuel gas has the correct composition and hence the methane number required for the required operating conditions. As mentioned above, the relationship between gas temperature and gas composition is a thermodynamic relationship, and there are many known models. Means 24, 30 actuate valves 34, 38 respectively.

The relationship between gas composition and its methane number is usually determined by the engine manufacturer or can be derived from EN 16726.

Claims (33)

1. A device (10) for supplying gas with an optimized methane number to at least one internal combustion engine (12), in particular, a vessel for transporting liquefied gas, characterized in that it includes at least - a pump (16) intended to be immersed in the bottom of a tank (14) for storing liquefied gas and having an outlet (16a) for gas in liquid form; - an evaporator (18) comprising a first circuit containing an inlet (18aa) connected to the outlet of the pump, and additionally containing an outlet (18ab) for gas in liquid form and gas in gaseous form; - a phase separator (20) comprising an inlet (20a) connected to said outlet of the evaporator and additionally including two outlets (20b, 20c), including a first outlet (20c) for gas in liquid form and a second outlet opening (20b) for gas in gaseous form; and - a heater (22) comprising a first circuit containing an inlet (22a) connected to a second separator outlet and an outlet (22b) for heated gas in gaseous form to supply at least one engine, characterized in that additionally contains a tank (44) for storing gas in liquid form, the first inlet (44a) of which is connected to the first outlet (20c) of the specified separator, while said tank (44) includes at least one outlet (44b, 44c) configured to - supply of medium for cooling the line (45) of the circulation of liquefied gas; and/or - feeding at least one burner (52). 2. Device (10) according to claim 1, characterized in that said evaporator (18) includes a second circuit for circulating a heat carrier, in particular glycol or steam. 3. Device (10) according to any of the preceding claims, characterized in that the outlet (18ab) of the first circuit of the evaporator (18) is connected to the first inlet of the mixer (36), which further includes a second inlet connected to the outlet (16a ) of the pump (16) and an outlet connected to the inlet (20a) of the separator (20). 4. Device (10) according to any one of the preceding claims, characterized in that it includes means (30) for controlling the temperature of the liquefied gas in the evaporator (18) and/or separator (20) to optimize evaporation and/or phase separation. 5. Device (10) according to claim 2, characterized in that said temperature control means (30) is connected to a valve (34) connected to the inlet of said second evaporator circuit (18). 6. Device (10) according to claim 3, characterized in that said temperature control means (30) is connected to a valve (38) connected to the second inlet of the mixer (36). 7. The device according to one of paragraphs. 4-6, characterized in that said temperature control means (30) is connected to at least one temperature sensor (32) installed in said separator (20). 8. Device (10) according to one of paragraphs. 4-7, said temperature control means (30) is connected to means (24) for controlling the methane number of the gas at the outlet of said heater (22). 9. Device (10) according to claim 1, characterized in that said methane number control means (24) is configured to control said temperature control means (30) and obtain data (28) relating to liquefied gas and operating parameters (26 ) of said at least one engine (12). 10. The device (10) according to claim 1, characterized in that said at least one outlet (44b, 44c) of said tank (44) is connected to the burner (52) through a valve (46, 48, 54) and /or heater (50). 11. Device (10) according to any of the preceding claims, characterized in that it includes a compressor (58) containing an inlet (58a) configured to be connected to an outlet (14a) for gas in gaseous form contained in said tank ( 14) and an outlet (58b) for compressed gas. 12. Device (10) according to claim 1, characterized in that said compressed gas outlet (58b) is connected to outlet (22b) of said heater (22) to power at least one motor (12). 13. The device (10) according to one of paragraphs. 1 or 10-12, characterized in that said compressed gas outlet (58b) is connected to a second inlet (44d) of said tank (44). 14. Device (10) according to claim 1 or claim 10, characterized in that said tank (44) includes a second inlet (44d) connected to means (64) for supplying pressurized nitrogen. 15. A method for supplying gas with an optimized methane number to at least one internal combustion engine, in particular a vessel for transporting liquefied gas, by means of a device (10) according to any one of the preceding claims, characterized in that - liquefied gas is pumped out by means of a pump (16) at a temperature not exceeding or equal to -160°C; - the pumped liquefied gas is heated in the evaporator (18) to a temperature of -130 to -10°C inclusive, preferably from -100 to -40°C inclusive, in order to evaporate some gases, called light gases, and other gases, called heavy gases remaining in liquid form; - liquid and gaseous phases are separated in the separator (20); and then - the gas in gaseous form coming from the separator (20) is heated to a temperature exceeding 0°C, in particular of the order of 20°C. 16. The method according to p. 15, characterized in that - liquefied gas is pumped out by pump (16) under pressure from 7 to 9 bar inclusive, in particular 8 bar; - the pressure in the evaporator (18) is between 6 and 12 bar inclusive and is in particular 7 bar; - the pressure in the separator (20) is between 5 and 7 bar inclusive and is in particular 6.2 bar; and - the pressure in the heater (22) is between 5 and 7 bar inclusive and is in particular 6 bar. 17. The method according to claim 16, characterized in that the pressure in the tank (44) is in the range from 1 to 10 bar inclusive and is, in particular, 2 bar.

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