DE102007042158A1 - Gas supply system for a gas-fueled internal combustion engine - Google Patents

Abstract

The invention relates to a gas supply system for a powered with gaseous fuel internal combustion engine 3, with a first gas line system 4, via which in a cargo tank 17 with cryogenic liquefied natural gas due to heating in the cargo tank 17 evaporating natural gas as Natural Boil-off gas in the direction of the Internal combustion engine 3 is conveyed, and with a second gas line system 22, via which, if the amount of Natural Boil-off gas is insufficient for the drive, liquid natural gas from the charge tank 17 with cryogenic liquefied natural gas removed, an evaporator 12 can be fed and after evaporation as a forced boil-off gas is miscible with the natural boil-off gas to promote this mixture towards the internal combustion engine 3. In order to create a novel gas supply system with which an optimized increase in the methane number of the mixture with little effort, it is provided that the second gas line system 22 via the evaporation device 12, the vaporized gas in a spray tank 8 and in addition via a control valve 7 on the vaporization device 12 separately carries liquid gas into the spray tank 8, the spray tank 8 comprises a temperature sensor 9 and a control which controls the flow rate of the liquid gas through the control valve 7 as a function of the temperature sensor 9, so that the temperature of the vaporized gas from the evaporation device 12 and possibly ...

Description

The The invention relates to a gas supply system for a Internal combustion engine according to the preamble of claim 1. Furthermore The invention relates to a method for providing an internal combustion engine combustible blend of natural boil off gas and forced boil off gas according to the preamble of claim 9.

In Gas tankers or other vehicles using natural gas as fuel natural gas is transported in liquefied state (LNG), the temperature of the cryogenic, liquefied natural gas at about -162 ° C and the pressure of the same at is at about atmospheric pressure. Gas tank or Cargo tanks, which are the recording of the transported, tiefkalt serve liquefied natural gas, are elaborately thermally insulated. Nevertheless, a certain warming of the entrained natural gas can not be avoided, which is why in the gas tank with cryogenic liquefied natural gas due to heating in the tank natural gas as a so-called natural boil-off gas evaporated. To one in consequence of this inevitable evaporation in the gas tank with cryogenic liquefied natural gas counteract the resulting increase in pressure, the natural boil-off gas removed from the gas container. The same principle applies for stationary, gas-powered drive systems with cargo tanks for cryogenic liquefied natural gas.

From the WO 2005/058692 A1 or the WO 2005/058684 It is already known that in the cargo tank with cryogenic liquefied natural gas due to heating vaporizing natural gas, ie the natural boil-off gas, a gas consumer, in particular to feed an internal combustion engine of a gas tanker, so as to the natural boil-off gas for driving the Gas tanker to use. Furthermore, it is also already known in this prior art that, if the amount of natural Boil-off gas is not sufficient, liquid natural gas from the gas container with cryogenic liquefied natural gas can be removed and fed to an evaporator.

The from the gas tank with cryogenic liquefied Natural gas taken from natural gas evaporates in the evaporation device partially and after evaporation as a so-called forced-boil-off gas Miscible with Natrual Boil-Off gas. This mix of the natural boil-off gas and the forced boil-off gas is then the gas consumer, in particular be fed to the drive by internal combustion engines. Not evaporating higher boiling components of natural gas in known systems unused in the gas tank or Charge tank returned.

The Composition of the mixture of the natural boil-off gas and the forced boil-off gas depends on different conditions and is subject to therefore changes. The mixture of the natural boil-off gas and the forced boil-off gas can only be used in an internal combustion engine such as As a diesel-gas or gasoline engine and formed in the Drive burned when the same a certain knock resistance having. As a measure of the knock resistance of this Mixture can be a so-called methane number of the mixture used be, with this methane number in about the ratio from methane to other components of the mixture of the natural boil-off gas and the forced boil-off gas. The methane number of any Gas mixture can by means of various commercial equipment be determined.

With the previously known gas supply systems for an internal combustion engine Although, to some extent, it can be considered in terms of knock resistance sufficient mixture of natural boil-off gas and forced boil-off gas be provided, d. H. it can vaporize the methane number of the Gases are increased, however, the mixture is not yet to be considered optimal. There is therefore a need for a gas supply system for the operation of internal combustion engines, by means of which such a mixture with optimized anti-knock properties, in particular a methane number greater than or equal to 80 provided can be.

Of these, Based on the present invention, the problem is based a novel gas supply system for a drive of Internal combustion engines and a novel method for providing a burnable in an internal combustion engine mixture of natural boil-off gas and To create forced-boil-off gas, with this an optimized boost the methane number of the mixture with little effort possible is.

This problem is solved by a gas supply system according to claim 1. According to the invention, the gas supply system comprises a second gas line system, which leads via the evaporation device, the vaporized gas in a spray tank, wherein the second gas line system additionally leads via a control valve on separate ways of the evaporation device liquid gas into the spray tank. The spray tank in turn comprises a temperature sensor and a controller that controls the flow rate of the liquid gas through the control valve in response to the temperature sensor, so that the temperature of the vaporized gas from the evaporator controlled by spraying the liquid gas in the spray tank is lowered and so heavy hydrocarbons in the Condensate gas and in liquid form from the Spray tank are derived and from the spray tank from the engine gas with a defined methane number can be fed.

Im figured You can sense the spraying of the vaporized gas with liquid gas (LNG) in the spray tank as washing or Consider cooling the forced boil-off gas (vaporized gas).

With Help of the spray tank, the temperature sensor and the control depending on the measured values of the temperature sensor in the spray tank of the liquid gas quantity, the methane number controlled by the internal combustion engine gas mixture be raised.

The Temperature of the gas (at a defined pressure) is a measure of the composition and thus a measure of the methane number of the gas leaving the spray tank. Thus, the internal combustion engine preferably via droplet and heat exchangers gas with a defined methane number, the methane number is greater than or equal to 80, fed become. Condensate which is in the spray tank and droplet separator is collected via a line or over a Kondensatabscheider by preferably a recooling Heat exchanger routed back into the cargo tank. Consequently would be guaranteed a so-called spray cycle.

To Mixture of the thus provided forced boil-off gas with the natural boil-off gas is located an optimized with regard to the knock resistance mixture Natural boil-off gas and forced boil-off gas in front.

The inventive method for providing a Combustible natural-boil-off-gas mixture burned in an internal combustion engine and forced-boil-off gas is defined in claim 9.

preferred Further developments of the invention will become apparent from the dependent claims and the description below. Embodiments of the Invention are, but are not limited to, based explained in more detail in the drawings. Showing:

1 A gas supply system according to the invention for an internal combustion engine according to a first embodiment of the invention, after which the spray tank is operated at a pressure level of the internal combustion engine,

2 A gas supply system according to the invention for an internal combustion engine according to a second embodiment of the invention, after which the spray tank is operated at a pressure level of the charge tank,

3 A gas supply system according to the invention for an internal combustion engine according to a third embodiment of the invention, in which the natural boil-off gas is passed through the spray tank, so that the spray tank is operated at the pressure level of the cargo tank,

4 A gas supply system according to the invention for an internal combustion engine according to a fourth embodiment of the invention, in which the Natrual Boil-off gas is passed through the spray tank and by an upstream pressure increasing means, so that the spray tank is operated at a pressure level of the internal combustion engine, and

5 A further gas supply system according to the invention for an internal combustion engine according to a fifth exemplary embodiment of the invention.

The present invention relates to a gas supply system for an internal combustion engine, wherein cryogenic liquefied natural gas as fuel in a cargo tank 17 is present.

The gas supply system according to the invention will be described below with reference to 1 to 5 described in more detail, wherein 1 to 5 each show different embodiments of the gas supply system according to the invention.

So shows 1 a first embodiment of a gas supply system according to the invention of an internal combustion engine 3 , The gas supply system has two gas piping systems 4 and 22 ,

About a first gas line system 4 can so-called natural boil-off gas in the direction of the internal combustion engine 3 be encouraged. The natural boil-off gas is created by evaporation of one in the cargo tank 17 held liquid and cryogenic natural gas due to heating of the liquid natural gas in the cargo tank 17 , wherein the natural boil-off gas via a gas line of the first gas line system 4 from the cargo tank 17 is dissipated. About in the gas line switched compressors 1 Natural-Boil-Off-Gas is the combustion engine 3 fed. The compressor line 1 . 1' . 1'' , is above the gas pressure level in front of the internal combustion engine 3 regulated.

Then if the amount of natural boil-off gas for the internal combustion engine 3 is not sufficient, with the help of a second gas line system 22 liquid cryogenic natural gas the cargo tank 17 removable and an evaporation device 12 the gas supply system fed. In the evaporation device 12 is the cargo tank 17 withdrawn liquid natural gas partially vaporizable and as a so-called forced-boil-off gas via a mixing point 31 with the natural boil-off gas from the first gas line system 4 miscible.

Downstream of the mixing point 31 Accordingly, there is a mixture of natural boil-off gas and forced boil-off gas, which in a heat exchanger 2 preferably at room temperature and then the engine 3 can be fed.

So is needed in the engine more natural gas than from the cargo tank 17 evaporates, this is done by means of a pressure sensor 21 in the first gas line system 4 or in the cargo tank 17 detected and additional natural gas by controlling a valve 10 in the second gas line system 22 the evaporation device 12 supplied in which the liquid natural gas by means of a pump 18 in the cargo tank 17 pressurized and through a heat exchanger 13 to the two control valves 7 and 10 is directed. By means of the valve 10 is the flow of natural gas through the evaporator 12 depending on the measured values of the pressure sensor 21 regulated and that in the evaporation device 12 gas is generated in the lower part of a spray tank 8th guided. About in the spray tank 8th through a temperature sensor 9 measured temperature is the flow rate at the valve 7 of the second gas line system 22 regulated and liquid, cold gas (LNG) at the top of the spray tank 8th fed. By spraying liquid natural gas by means of a spraying device 30 in the spray tank 8th The temperature of the vaporized gas is at the top of the spray tank 8th controlled lowered. Furthermore, then the internal combustion engine 3 over a droplet separator 5 and a heat exchanger 6 supplied with respect to the methane number optimally adjusted gas. Condensate which is in the spray tank 8th and in the droplet separator 5 is collected via a line 15 and via a condensate separator 14 through a recooling heat exchanger 13 over a line 16 back into the cargo tank 17 directed.

By the arrangement of the compressor 1 in the first supply line 4 before the mixing point 31 becomes the spray tank 8th at a pressure level of the internal combustion engine 3 operated.

In summary, therefore, shows 1 a gas supply system for a gaseous fuel powered internal combustion engine 3 with a first gas line system 4 , about which in a cargo tank 17 with cryogenic liquefied natural gas due to heating in the cargo tank 17 Evaporating natural gas as a natural boil-off gas in the direction of the internal combustion engine 3 is recoverable and with a second gas line system 22 , via which, if the amount of natural boil-off gas is insufficient for the drive, liquid natural gas from the charge tank 17 Removable with cryogenic liquefied natural gas, an evaporation device 12 feedable and, after partial evaporation as a forced boil-off gas, is miscible with the natural boil-off gas to provide the mixture of the natural boil off gas and the forced boil off gas toward the internal combustion engine 3 to promote. This leads the second gas line system 22 via the evaporation device 12 the vaporized gas into the spray tank 8th and the second gas line system 22 additionally leads via a control valve 7 on from the evaporator 12 separate way, liquid gas in the spray tank. The spray tank 8th includes a temperature sensor 9 and a scheme that depends on the temperature sensor 9 the flow rate of the liquid gas through the control valve 7 controls, so that the temperature of the vaporized gas from the evaporation device 12 by spraying the liquid gas in the spray tank 8th can be lowered and thus condense heavy hydrocarbons in the gas and in liquid form from the spray tank 8th are derivable and from the spray tank 8th from the supply engine 3 Gas can be supplied with a defined methane number.

That in the spray tank 8th forming condensate can by means of a steam trap 14 the cargo tank 17 be forwarded again.

In the first gas line system 4 or cargo tank 17 is a pressure sensor 21 to determine the pressure in the cargo tank 17 provided by means of this and a cooperating with this control valve 10 the evaporation rate, ie the flow rate of the forced boil-off gas through the evaporator 12 is controllable.

The gas, which is the spray tank 8th in the direction of the internal combustion engine 3 This is about a droplet separator 5 and a heat exchanger 6 fed. That is in the droplet separator 5 forming condensate is by means of a pipe 15 the cargo tank 17 re-deliverable.

The condensate flow of the droplet separator 5 and / or the condensate 14 is in a heat exchanger 13 in front of the cargo tank 17 rückkühlbar.

The method of providing one in internal combustion engines 3 combustible mixture of natural-boil-off-gas and forced-boil-off-gas, being in a cargo tank 17 with cryogenic liquefied natural gas due to heating in the cargo tank 17 Evaporating natural gas as a natural boil-off gas in the direction of the internal combustion engine 3 and, if the amount of natural boil-off gas is insufficient for operation, then liquid natural gas is discharged from the charge tank 17 taken, an evaporation device 12 supplied and mixed after partial evaporation as a forced boil-off gas with the natural boil-off gas, the steps comprises that at least the vaporized gas a spray tank 8th in which the temperature of the gas passed (forced-boil-off gas) by spraying liquid natural gas (LNG) from the charge tank 17 is reduced so that heavy hydrocarbons condense in the gas and are discharged in liquid form.

That through the evaporation device 12 guided gas is doing in the lower part of the spray tank 8th and the amount of the liquid gas to be sprayed by means of a spray device 30 in the upper area of the spray tank 8th guided, wherein the amount of the liquid gas to be sprayed as a function of the temperature in the spray tank 8th by means of a valve 7 is regulated, so that the temperature of the forced-boil-off gas in the upper area of the spray tank 8th is lowered in a controlled manner.

The temperature of the gas in the spray tank 8th is by means of a temperature sensor 9 in the area above the spraying device 30 or in the gas discharge to the spray tank 8th measured.

The spray tank 8th is with the for the internal combustion engine 3 operated increased internal pressure.

2 to 5 show further embodiments of a gas supply system according to the invention for a drive by internal combustion engines, wherein the same reference numerals are used to avoid unnecessary repetition for the same components and will be discussed below only on such details, through which the embodiments of the 2 to 5 from the embodiment of 1 or distinguish between them.

Thus, the embodiment differs from the 2 from the embodiment of 1 only by the arrangement of a pressure increasing device 1' downstream of the gas mixture between the mixing point 31 and the internal combustion engine 3 so that the spray tank 8th with an internal pressure at the pressure level of the cargo tank 17 is operated.

3 shows an embodiment of a gas supply unit, in which the first gas line system 4 ' instead of the spray tank 8th also through the spray tank 8th is guided, the mixing point 31 in the supply line 22 from the evaporation device 12 to the spray tank 8th located. The pressure booster 1' is downstream of the engine 3 supplied gas to the spray tank 8th downstream, leaving the spray tank 8th with an internal pressure at the pressure level of the cargo tank 17 is operated.

4 shows a small modification of the embodiment of 3 in the embodiment of the 4 instead of the compressor 1' of the embodiment of 3 a compressor 1'' in the supply line 4 ' before the mixing point 31 upstream, so that the spray tank 8th at a pressure level in front of the combustion engine 3 is operated.

This embodiment (as well as according to 2 ) results in a drastically reduced spray tank volume. The statements according to 3 and 4 to improve the methane number of natural boil-off gas are particularly interesting in operating states with a high proportion of natural boil-off gas and low share of forced-boil-off gas.

5 shows a further embodiment of the gas supply system according to the invention, in which for the application of the control valves 7 and 10 of the spray tank 8th with liquid gas one outside the cargo tank 17 arranged pressure booster 19 is provided. The pressure booster 19 acts with a flow vessel 20 together to aspirate liquid gas, the precursor 20 by yourself in the cargo tank 17 located pressure booster 18 is fillable.

In the 5 illustrated embodiment is a combination with the embodiments of 1 to 4 ,

1, 1 ', 1' '

compressor

2

heat exchangers

3

drive

4, 4

supply line

5

demister

6

heat exchangers

7

control valve

8th

spray tank

9

temperature sensor

10

Control valve

12

Forced evaporation device

13

Wärmtauscher (Back cooling)

14

condensate

15

management

16

management

17

cargo tank

18

pump

19

Pressure increasing means

20

balance tank

21

pressure sensor

22

feed

30

sprayer

31

mixing point

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• WO 2005/058692 A1 [0003]
• WO 2005/058684 [0003]

Claims (17)

Gas supply system for a gaseous fuel-powered internal combustion engine ( 3 ), with a first gas line system ( 4 . 4 '' ), over which in a cargo tank ( 17 ) with cryogenic liquefied natural gas due to heating in the cargo tank ( 17 ) Evaporating natural gas as natural Boil-off gas in the direction of the internal combustion engine ( 3 ) and with a second gas pipeline system ( 22 ), via which liquid natural gas from the charge tank ( 17 ) with cryogenic liquefied natural gas, an evaporation device ( 12 ) and after partial evaporation as a forced boil-off gas with the natural boil-off gas is miscible to this mixture in the direction of the internal combustion engine ( 3 ), characterized in that the second gas line system ( 22 ) via the evaporation device ( 12 ) the vaporized gas into a spray tank ( 8th ), in addition via a control valve ( 7 ) from the evaporation device ( 12 ) separated way liquid gas into the spray tank ( 8th ) that the spray tank ( 8th ) a temperature sensor ( 9 ) and a regulation that depends on the temperature sensor ( 9 ) the flow rate of the liquid gas through the control valve ( 7 ), so that the temperature of the vaporized gas from the evaporation device ( 12 ) by spraying the liquid gas in the spray tank ( 8th ) controlled is lowered. Gas supply system according to claim 1, characterized in that in the spray tank ( 8th ) condensate with the aid of a Kondensatabscheiders ( 14 ) the charge tank ( 17 ) can be forwarded again. Gas supply system according to claim 1 or 2, characterized in that a pressure sensor ( 21 ) for determining the pressure in the first gas line system ( 4 . 4 '' ) or charge tank ( 17 ) is provided, by means of this and a cooperating with this control valve ( 10 ) the evaporation rate, ie the flow rate of the forced boil-off gas through the evaporation device ( 12 ) is controllable. Gas supply system according to one of the preceding claims, characterized in that the first gas line system ( 4 ' ) also through the spray tank ( 8th ) is guided. Gas supply system according to one of the preceding claims, characterized in that the gas which contains the spray tank 8th in the direction of the internal combustion engine ( 3 ) leaves this via a droplet separator ( 5 ) and a heat exchanger ( 6 ) can be supplied and in the droplet ( 5 ) forming condensate by means of a line ( 15 ) the charge tank ( 17 ) is zuluhrbar. Gas supply system according to claim 2 and / or Anpsruch 5, characterized in that the condensate flow of the Droplet ( 5 ) and / or the condensate separator ( 14 ) in a heat exchanger ( 13 ) in front of the cargo tank ( 17 ) can be cooled back. Gas supply system according to one of the preceding claims, characterized in that for acting on the control valves ( 7 ) and ( 10 ) of the spray tank ( 8th ) with liquid gas one outside the cargo tank ( 17 ) arranged pressure booster ( 19 ) is provided. Gas supply system according to claim 7, characterized in that the pressure increasing device ( 19 ) with a preliminary vessel ( 20 ) cooperates to draw in liquid gas, wherein the preliminary vessel ( 20 ) in the cargo tank ( 17 ) located pressure booster ( 18 ) is fillable. Method for providing a combustion engine ( 3 ) combustible mixture of natural-boil-off-gas and forced-boil-off-gas, wherein in a cargo tank ( 17 ) with cryogenic liquefied natural gas due to heating in the cargo tank ( 17 ) Evaporating natural gas as natural Boil-off gas in the direction of the internal combustion engine ( 3 ), and wherein, if the amount of the natural boil-off gas is insufficient for the drive, liquid natural gas from the charge tank ( 17 ), an evaporation device ( 12 ) and after evaporation as a forced boil-off gas at a mixing point ( 31 ) is mixed with the natural boil-off gas, characterized in that the vaporized gas is a spray tank ( 8th ), in which the temperature of the gas passed through by spraying liquid natural gas from the charge tank ( 17 ) is reduced so far that heavy hydrocarbons condense in the gas and are discharged in liquid form. A method according to claim 9, characterized in that by the evaporation device ( 12 ) guided gas into the lower area of the spray tank ( 8th ), the amount of the liquid gas to be sprayed by means of a spray device ( 30 ) in the upper area of the spray tank ( 8th ), wherein the amount of the liquid gas to be sprayed as a function of the temperature in the spray tank ( 8th ) by means of a valve ( 7 ), so that the temperature of the gas in the upper area of the spray tank ( 8th ) is lowered in a controlled manner. A method according to claim 10, characterized in that the temperature of the gas in the spray tank ( 8th ) by means of a temperature sensor ( 9 ) in the Area above the spray device ( 30 ) or in the gas discharge to the spray tank ( 8th ) is measured. Method according to one of claims 9 to 11, characterized in that the evaporation capacity of the gas supply system by means of a control valve ( 10 ) and a cooperating with this in a control loop pressure sensor ( 21 ) for determining the pressure in the gas line system or cargo tank ( 17 ) is controlled. Method according to one of claims 9 to 12, characterized in that the spray tank ( 8th ) with that for the internal combustion engine ( 3 ) increased internal pressure is operated. Method according to one of claims 9 to 12, characterized in that the spray tank ( 8th ) with an internal pressure at the pressure level of the charge tank ( 17 ) and a pressure booster ( 1' ) downstream of the gas mixture between the mixing point ( 31 ) and the internal combustion engine ( 3 ) is operated. Method according to claim 14, characterized in that the spray tank ( 8th ) a pressure booster ( 1'' ) is preceded, by this the natural boil-off gas the spray tank ( 8th ) is supplied. Method according to claim 13, characterized in that the spray tank ( 8th ) the entire amount of natural boil-off gas is supplied. Method according to one of claims 9 to 16, characterized in that from the spray tank ( 8th ) by means of a condensate separator ( 14 ) the condensate stream in a heat exchanger ( 13 ) and again the charge tank ( 17 ) and that the heating of the heat exchanger ( 13 ) either no regulation at all (eg direct operation with seawater) or at least no implication of the control in control circuits of the pressure sensor ( 21 ) and control valve ( 10 ) requirement.