DE10040679A1 - Device and method for pressure-controlled supply from a liquid gas tank - Google Patents

Abstract

In the case of tank devices for liquefied gas-powered vehicles, the pressure builds up only very slowly until a desired operating pressure is reached. The installation of heating devices inside the tank leads to thermal bridges, which reduce the storage time of the tank. DOLLAR A According to the invention, liquefied petroleum gas is removed from a storage container, fed to a heat exchanger through a liquefied gas feed line and evaporated there. The vaporized liquefied gas is then at least partially fed back to the storage container via a gas return line. By using check valves in the liquid gas supply line as well as in the gas return line, directional pressure pulsations are produced, which bring about a rapid heat input into the interior of the storage tank. Gas is expediently removed for a consumer on the side of the heat exchanger which is fluidically remote from the liquid gas supply. DOLLAR A Through the invention, a rapid rise in pressure in the storage container is achieved, at the same time the heat input by thermal bridges or thermoacoustic vibrations is reduced compared to devices according to the prior art. Manufacturing and maintenance costs of the storage container are reduced and the use of simple leak detection methods is facilitated.

Description

The invention relates to a device and a method for pressure-controlled Supply from a liquid gas tank.

According to the technical rules for compressed gases (TRG 103) are considered cryogenic liquefied gases classified such gases, their liquid state thereby remains that their storage temperature through technical measures such as Cooling or insulation is retained. Through special insulation, such as Powder vacuum or super insulation, the liquid state over a held for a long period of time and the loss due to evaporation limited to less than 1% per day. When withdrawing liquid there is a pressure drop in the storage tank. In many applications, for example when used as a fuel tank in vehicle technology, it is however, it is necessary to keep the tank pressure substantially constant. To the To achieve the pressure build-up required for operation, the interior of the tank Heat can be supplied. So far, pressure build-up evaporators or Heating devices used inside the tank.

With a pressure build-up evaporator, the storage container gets a small amount removed from the liquid gas. This will be outside of the liquid gas evaporated and returned to the tank. Such, for example from the Systems known from DE 23 29 053 A1 are, however, in the case of small dimensions Hydrogen tanks, such as those used predominantly in vehicle technology come, inefficiently.

A system based on heating gas to maintain and Increasing the pressure in a low-temperature tank is known from DE 196 45 492 C2 known. A heating gas is passed through the tank extending pipeline. In the article by F. Michel: "The next Step: Driving with liquid hydrogen ", gas aktuell 58, p. 18 (2000) is a Pressure control system described in which part of the in a storage tank stored liquid hydrogen evaporates in a heat exchanger and  is then passed through a pipe, which is partly through the Tank extends through. The hydrogen passed through the pipeline gives in A part of its heat is removed from the inside of the tank and is subsequently second heat exchanger reheated and fed to a consumer.

Electric heaters are an alternative to gas-powered heating devices as used, for example, in the article by H. Fieseler, W. Hettinger and M. Kesten: "Liquid hydrogen as fuel in test vehicles", gas Aktuell, 36, p. 17, (1989).

A disadvantage of the known systems with internal heating, however, is that additional pipes and / or feeds into the tank interior are required are, on the one hand, represent thermal bridges and thus an undesirable one Lead heat input into the tank and the other very expensive to install and maintenance are. For devices with closed pipe systems in the Inner containers can also cause thermoacoustic vibrations which further increases the undesired heat input.

DE 196 45 488 C1 describes a system for extracting cold gas, for example liquid hydrogen or liquefied natural gas, from a low-temperature tank previously known, the one with a heat-insulated storage container for liquid Has gas connected sampling line. The also heat insulated Sampling line opens into a non-insulated one outside the low-temperature tank Evaporator volume, which is about the form of an extension of the sampling line may have. A line leads from the evaporator volume via a valve a consumer. Due to the pressure differential between the tank and the consumer there is a flow of liquid in the sampling line to the Evaporator volume. The liquid penetrating there evaporates immediately. This leads to an increase in pressure due to the liquid and Part of the already evaporated liquid through the sampling line into the tank is pushed back until the pressure in the sampling line is balanced. Then the liquid flows through the sampling line in the direction of the Evaporation volume. This creates a pressure oscillation, which compensates for the pressure drop caused by the removal. A disadvantage of  However, this prior art is that the time until the Operating pressure in the storage tank lasts quite a long time.

The object of the present invention is therefore a possibility for the supply to create with gas or liquefied petroleum gas from a liquefied petroleum gas tank at which a accidental heat input via thermal bridges or thermoacoustic Vibration is minimized and at the same time is quicker Pressure builds up in the tank.

This task is solved on the one hand by a device with the features of claim 1, on the other hand by methods with the features of Claims 10 and 12 respectively.

In the device according to the invention, liquefied petroleum gas is extracted from the Storage container removed and a via a liquid supply line Heat exchanger supplied. A very quick one takes place in the heat exchanger Evaporation of the liquid gas, which leads to a sharp rise in pressure. A part of the vaporized liquid gas passes through the gas return line into the Storage tank back and increases the pressure there. At the same time are in the Gas return line and in the liquid supply line blocking means provided the Backflow of liquid gas from the heat exchanger into the storage tank as well of gas from the storage tank in the heat exchanger at least largely lock. Directed pressure pulsations are generated by means of which in introduced a large amount of heat into the storage tank and the Pressure there can be increased quickly.

The removal of gas proves to be particularly advantageous for one Consumers on a gas line on top of the liquid supply line Fluidically facing side of the heat exchanger is arranged. On The first part of the liquid gas evaporated in the heat exchanger is thus sent directly to the consumer, while a second part for the purpose Pressure build-up is supplied to the storage tank. Through the blocking agent at least largely avoided that gas directly from the  Storage tank reaches the consumer and thus gas that is for the Pressure build-up is provided in the storage tank is deducted.

In a development of the invention, the blocking means are in the gas return line a control device operatively connected, by means of which a working pressure can be set. The working pressure defines a pressure above which the blocking means one Enable flow in the direction of the heat exchanger or the consumer. The working pressure is, for example, one for operating the Consumers required working pressure. Is this pressure in the storage tank reached, gas can be sent directly from the storage tank to the consumer be delivered.

The blocking means in the liquid gas feed line preferably comprise and / or in the gas return line check valves that a flow in Prevent the blocking direction practically completely.

One with one preferably proves to be particularly expedient Storage volume provided with thermal insulation in the liquid gas supply line is arranged and in the liquid gas - until its complete evaporation in the heat exchanger - can be stored temporarily. By the Storage volume is fed to the heat exchanger more liquefied gas than from Consumer gas is removed. The excess gas becomes Pressure build-up used in the storage tank. The stock volume that is preferred fluidically between the blocking means of the liquid supply line and the Heat exchanger is arranged should be such that the amount of supplied and vaporized liquefied petroleum gas, including that from the consumer withdrawn amount, just sufficient to the desired operating pressure in the To generate storage containers.

To ensure that the liquefied gas supplied to the heat exchanger is not has already evaporated in whole or in part in the LPG supply line expediently provided with thermal insulation. By the arrangement thermal insulation right up to the heat exchanger is ensured that the vast majority of that passed through the LPG supply line  Liquid gas only evaporates when it enters the heat exchanger. at corresponding heat transfer performance of the heat exchanger takes place Evaporation suddenly. The highly transient generated Flow conditions lead to good heat input into the tank.

The device according to the invention can advantageously also be used in systems that supply a liquid gas consumer. An embodiment of the The invention therefore provides for the liquefied gas supply line to be connected to an extraction line Supply of liquid gas to a liquid gas consumer to provide the fluidically between the blocking means in the liquid supply line and the heat exchanger is arranged.

The arrangement of a pressure-controlled valve in FIG the fluid supply line, fluidically between the connection of the Extraction line and the heat exchanger, which is the liquid supply line locks above a specified operating pressure in the tank when falling below of the operating pressure, however, opens by a predetermined amount. With this valve the heat exchanger can be uncoupled when the operating pressure is reached and so unwanted further evaporation of liquid gas can be avoided.

The storage container is preferred for storing liquid hydrogen or liquefied natural gas (LNG).

In the gas supply method according to the invention according to the features of claim 10, liquid gas is removed from the storage container and fed to a heat exchanger. A very quick one takes place in the heat exchanger Evaporation of the liquid gas, which leads to a sharp rise in pressure in the Heat exchanger leads. At least part of the vaporized liquid gas arrives back into the storage tank and increases the internal pressure there. It will Backflow of liquid gas from the heat exchanger into the storage tank and the backflow of gas from the storage tank to the heat exchanger at least largely by means of suitable locking means, such as check valves Flap systems, flow resistances or the like, prevented. At a Overpressure in the heat exchanger compared to the storage tank is a  Pressure compensation essentially only via the gas phase, with a negative pressure in the Heat exchangers compared to the storage tank, however, essentially only produced over the liquid phase of the liquid gas. That way directed pressure pulsations formed, the large amounts of heat in the Insert the storage container and so quickly in the storage container Pressure build-up, for example up to a desired operating pressure of the Effect consumer. The consumer is supplied with gas by Extraction of part of the vaporized liquid gas by flow between the heat exchanger and the backflow of gas from the Blocking means preventing storage containers. This ensures that the vaporized LPG fed into the storage tank primarily to Pressure build-up is used.

It proves advantageous to have the backflow of gas from the Storage tank in the heat exchanger above a predetermined Working pressure, which is, for example, the operating pressure of a connected consumer can act to release. After reaching the Working pressure, and as long as the pressure in the storage tank is higher than this, can thus supply the consumer directly from the Storage tank done.

In the method according to the invention for liquid gas supply according to Features of claim 12 is liquefied petroleum gas from the storage container removed and fed to a heat exchanger. One takes place in the heat exchanger very rapid evaporation of the liquid gas, which leads to a sharp rise in pressure leads in the heat exchanger. At least part of the vaporized liquid gas gets back into the storage tank and increases the internal pressure there. there the backflow of liquid gas from the heat exchanger into the Storage tank and the backflow of gas from the storage tank to Heat exchanger at least largely by means of suitable blocking agents, for example Check valves, flap systems, flow resistances or the like, prevented. A consumer is supplied with LPG by Extraction of part of the liquid gas that has not yet evaporated fluidic between the heat exchanger and the backflow  of liquid gas in the storage container blocking blocking agent. The Removal of the liquid gas at this point causes the automatic Co-supply of the heat exchanger with liquid gas and thus the Maintaining sufficient pressure in the storage tank.

The inventive method according to claims 10, 11 or 12 are particularly suitable for gas supply to vehicle engines. In particular With the method according to the invention, a rapid build-up of pressure in the Realize storage tanks and so quickly after refueling Driving operation required gas pressure.

Exemplary embodiments of the invention are to be described below with reference to the drawings are explained in more detail.

Schematic views show:

Fig. 1 shows a device according to the invention for the pressure-regulated gas supply of a vehicle engine,

Fig. 2: the cutout 11 of Figure 1 in another embodiment, and.

FIG. 3 shows an inventive device for pressure-regulated liquid supply.

The device 1 shown in Fig. 1 comprises a reservoir 2 and a heat exchanger 3. The storage container 2 is a container for storing cryogenic liquefied gas, for example liquefied hydrogen or liquefied natural gas, which is provided with thermal insulation 4 in order to achieve a long-lasting storage effect. This heat insulation 4 can be, for example, a superinsulation suitable for LPG vehicle tanks, as described in the article "Liquid Hydrogen as a Fuel in Experimental Plants" gas current 36, p. 17 ( 1989 ). Other fittings, such as a filling line for liquid gas, a level meter, a pressure relief valve and the like. The like are not shown in the drawing for reasons of clarity, but are present in the storage container 2 .

The storage container 2 is connected in terms of flow to the heat exchanger 3 via a liquid gas feed line 6 . The liquid gas feed line 6 is provided with thermal insulation 7 over its entire length. In the liquid gas supply line 6 , one after the other in terms of flow, there is a check valve 8 which only allows liquid gas or gas to flow in the direction of the heat exchanger 3 , but not in the direction of the storage tank 2 , and a storage volume 9 in the form of an expansion of the line cross section of the liquid gas supply line 6 arranged.

The heat exchanger 3 is operated either electrically or by means of a liquid heat transfer medium which is introduced into the heat exchanger 3 through a heat transfer line 11 and out again through a heat transfer line 12 and brought into thermal contact with the liquid gas guided here in heating coils 13 inside the heat exchanger 3 becomes. Instead of heating coils 13 , other evaporation volumes can also be used, for example an evaporation chamber in the form of a non-insulated extension of the liquid gas supply line 6 or a cup connected to the liquid gas supply line 6 . On its side, in terms of flow technology, facing away from the liquid gas feed line 6 , the heating coils 13 are connected in terms of flow via a gas line 14 to a consumer (not shown here), for example a gas-operated engine.

A gas return line 16 branches off from the gas line 14 at a flow divider 15 , which in turn opens into the storage container 2 . Through the gas return line 16 there is a flow connection between gas which is located in the gas line 14 , that is to say in particular liquid gas evaporated in the heat exchanger 3 , and a gas phase 17 existing in the storage container 2 . A check valve 18 is arranged in the gas return line 16 , which allows a gas flow only in the direction of the storage container 2 , but not in the direction of the gas line 14 . At the same time, however, the check valve 18 is bridged by means of a bypass line 21 which is equipped with a controllable valve 22 . The valve 22 is controlled by a control device 23 as a function of the internal pressure prevailing in the storage container 2 , which is detected by a measuring device 24 . The liquid gas supply line 6 and the gas return line 16 can be closed in the idle state of the device 1 or during refueling with valves, not shown here. Instead of a valve 22 controlled by a control device 23 , a simple mechanical pressure control can also be used.

When gas is withdrawn by a consumer, liquid gas flows from the storage container 2 into the storage volume 9 and from there into the heat exchanger 3 (inflow phase). The liquid gas flowing in there evaporates very quickly, producing more gas than is consumed by the consumer (evaporation phase). The resulting overpressure in the heat exchanger 3 compared to the pressure in the storage container 2 is compensated exclusively by the flow of gas through the gas return line 19 , since the backward valve 8 prevents liquid gas from being pushed back through the liquid gas supply line 6 into the storage container 2 . The pressure in the storage container 2 thus increases. The check valve 18 prevents the direct outflow of gas from the storage container 2 to the consumer. After the entire liquid gas has been evaporated from the storage volume 9 , the pressure in the heat exchanger 3 drops and adjusts to the pressure in the storage container 2 . (Balancing phase). Continued removal of gas by the consumer finally creates a negative pressure in the heat exchanger 3 with respect to the storage tank 2 , which is compensated for by renewed supply of liquid gas from the storage tank 2 (inflow phase, see above).

The sudden evaporation of the liquid gas in the evaporation phase thus leads to the development of highly unsteady flow conditions in the form of pressure pulsations, through which a good heat input into the tank 2 is achieved. A rapid pressure build-up in the storage container 2 is thereby achieved. The formation of unsteady flow conditions is all the better, the lower the proportion of the liquid gas fed into the heat exchanger 3 that is already evaporating in the liquid gas supply line 6 , in other words, the better the heat insulation 7 or the shorter the liquid gas supply line 6 is. The amplitude and the pulse frequency of the pressure pulsation are determined in particular by the evaporation volume and the heating power in the heat exchanger 3 and by the size of the storage volume 9 .

If an optimum operating pressure in the storage container 2 is reached for the consumer, the control device 23 opens the valve 22 . The bypass line 21 enables the consumer to be supplied directly with gas from the storage container 2 . If the pressure in the storage container 2 drops below the operating pressure, for example due to continued consumption or during the filling process of the storage container 2 , the valve 22 is closed on the basis of a corresponding control signal from the control device 23 .

The alternative II 'shown in FIG. 2 for arranging a heat exchanger 3 in the device 1 differs from the alternative II shown in FIG. 1 only in that the heat exchanger 3 is arranged below the storage volume 9 . This prevents liquid flowing into the heat exchanger 3 from accumulating on the lower part of the heat exchanger 3 , with the result that the full capacity of the heat exchanger is only partially used. In the arrangement II 'in FIG. 2, the liquid drops flowing into the heat exchanger 3 pass through due to the force of gravity. Heating coil 13 from top to bottom as the liquid surface gradually evaporates. The capacity of the heat exchanger 3 is used optimally.

The device 25 shown in FIG. 3, in which elements with the same effect are designated with the same reference numerals as in the device 1 from FIG. 1, is suitable for systems in which a consumer supplies liquid gas and quickly builds up a predetermined operating pressure shall be. In this case, instead of a gas extraction line 14, a liquid extraction line 27 is provided, which opens out of the storage volume 9 at a flow divider 26 . The flow divider 26 is arranged approximately in the middle of the longitudinal extent of the storage volume 9 in order to ensure that the heat exchanger 3 is always in flow connection with liquid gas in the storage volume 9 . A pressure-controlled valve 28 is installed between the storage volume 9 and the heat exchanger 3 and, depending on the pressure in the gas return line - as described in more detail below - closes or opens the liquid gas supply line 6 . The liquid gas supply line 6 , the storage volume 9 , the valve 28 and at least an upper section 29 of the liquid extraction line 28 are encased with a thermal insulation 7 .

In a tank 2 'of the device 25 , which is provided for the liquid gas supply of a vehicle, the hydrostatic pressure of the liquid column measuring only a few decimeters in the storage container 2 ' is generally not sufficient to reduce the flow resistance of the check valve 8 against a flow in the direction of the To overcome heat exchanger. For this reason, liquefied gas can only be withdrawn at an initial pressure, measured between the inside of the storage container 2 'and the storage volume 9 , which is greater than the flow resistance of the check valve 8 . Such an initial pressure is, of course, achieved when the storage container 2 'is refueled. After the initial pressure has been established, liquid gas flows from the tank 2 'into the storage volume 9 and from there into the heat exchanger 3 . (Einströmphase). The liquid gas flowing into the heat exchanger 3 evaporates suddenly (evaporation phase). The resulting gas passes through the gas return line 16 into the storage container 2 'and increases the pressure there. A backflow of liquid gas into the storage container 2 'is prevented by the check valve 8. When a predetermined operating pressure measured in the gas return line 16 upstream or downstream of the check valve 18 is reached, the valve 26 closes. With the removal of liquefied petroleum gas, the pressure in the storage container 2 'decreases again (compensation phase). If the operating pressure falls below a predetermined amount, the valve 26 opens again and liquid gas flows into the heat exchanger. The evaporating liquefied gas ensures an increase in pressure in the storage container 2 'in the manner described.

The device 1 or 25 can be supplemented by installing the corresponding fittings apparent from the respective other device 25 or 1 to form a new device which allows both the removal of gas and of liquefied gas.

In the devices 1 and 25, a rapid pressure build-up in the storage container 2 is achieved without the need, as would be required in the prior art, separate baffles in the interior of the storage container 2, such as heating cables, power leads etc.. In this way, an entry of heat which is disadvantageous for the permanent storage of the liquid gas, but which is inevitably linked to such internals, is avoided by heating bridges or by thermoacoustic vibrations in heating lines which are present.

LIST OF REFERENCE NUMBERS

1

contraption

2

.

2

'' Storage tank

3

heat exchangers

4

thermal insulation

5

-

6

liquid gas supply line

7

thermal insulation

8th

check valve

9

storage volume

10

-

11

Heat transfer fluid in

12

Heat transfer derivation

13

heating coils

14

gas pipe

15

flow divider

16

Gas return line

17

gas phase

18

check valve

19

-

20

-

21

bypass line

22

controllable valve

23

control device

24

gauge

25

contraption

26

flow divider

27

Liquid extraction line

28

Valve

29

upper section

Claims (13)

1. Device for pressure-controlled supply from a liquid gas tank, with a heat-insulated storage tank ( 2 ) for storing liquid gas and a heat exchanger ( 3 ) for evaporating liquid gas, which heat exchanger ( 3 ) via a liquid gas supply line ( 6 ) for liquefied gas and a gas return line ( 16 ) for liquid gas evaporated in the heat exchanger ( 3 ) is in flow connection with the storage container ( 2 ), characterized in that blocking means are arranged in the gas return line ( 16 ) and in the liquid gas supply line ( 6 ), which block the backflow of liquid gas from the heat exchanger ( 3 ) in the storage tank ( 2 ) or the backflow of gas from the storage tank ( 2 ) into the heat exchanger ( 3 ) at least largely suppress. 2. Device according to claim 1, characterized in that the heat exchanger ( 3 ) on its side facing away from the liquid gas supply line ( 6 ) is connected to the flow via a gas line ( 14 ) with a gas consumer. 3. Device according to claim 2, characterized in that the locking means ( 18 ) in the gas return line ( 16 ) are operatively connected to a control device ( 23 ) by means of which a working pressure can be set, above which no locking effect of the locking means ( 18 ) in the direction of Gas pipe ( 14 ) is more. 4. Device according to one of the preceding claims, characterized in that the blocking means in the gas return line ( 16 ) and / or in the liquid gas supply line ( 6 ) comprise a check valve ( 8 , 18 ). 5. Device according to one of the preceding claims, characterized in that in the liquid gas supply line ( 6 ) a preferably with thermal insulation ( 7 ) provided storage volume ( 9 ) is provided, from which liquid gas can be continuously removed for evaporation. 6. Device according to one of the preceding claims, characterized in that the liquid gas feed line ( 6 ) to the heat exchanger ( 3 ) is provided with thermal insulation ( 7 ). 7. Device according to one of the preceding claims, characterized in that the liquid gas supply line ( 6 ) is provided with a removal line ( 27 ) for supplying liquid gas to a liquid gas consumer, the flow technology between the blocking means ( 8 ) in the liquid supply line and the heat exchanger ( 3rd ) is arranged. 8. The device according to claim 7, characterized in that in the liquid gas supply line ( 6 ), fluidically between the connection of the extraction line ( 27 ) and the heat exchanger ( 3 ), a pressure-controlled valve ( 28 ) is provided, which the liquid supply line above a predetermined operating pressure locks in the tank ( 2 ), but opens when the operating pressure falls below a predetermined amount. 9. Device according to one of the preceding claims, characterized in that liquefied hydrogen or liquefied natural gas is used as the liquefied gas in the storage container ( 2 ). 10. Method for the pressure-controlled supply of gas from a liquefied petroleum gas tank, in which liquefied petroleum gas is removed from a storage tank ( 2 ), fed to a heat exchanger ( 3 ) and evaporated there, and in which at least a part is then passed back into the storage tank ( 2 ), wherein the backflow of non-evaporated liquefied gas from the heat exchanger ( 3 ) into the storage container ( 2 ) and the backflow of evaporated liquefied gas from the storage container ( 2 ) into the heat exchanger ( 3 ) and / or the consumer through blocking means ( 8 , 18 ) at least largely is prevented and in which the removal of gas for a consumer takes place fluidically between the heat exchanger and the blocking means ( 18 ) preventing the backflow of gas from the storage container ( 2 ) into the heat exchanger ( 3 ). 11. The method according to claim 10, characterized in that the backflow of vaporized liquefied gas from the storage container ( 2 ) into the heat exchanger ( 3 ) and / or the consumer is released above a predetermined working pressure. 12.Method for the pressure-controlled supply of liquid gas from a liquid gas tank, in which liquid gas is removed from a storage tank ( 2 '), fed to a heat exchanger ( 3 ) and evaporated there, and in which at least some of the vaporized liquid gas is then returned to the storage tank ( 2 ') is conducted, the backflow of non-evaporated liquid gas from the heat exchanger ( 3 ) into the storage tank ( 2 ') and the backflow of evaporated liquid gas from the storage tank ( 2 ') into the heat exchanger ( 3 ) by blocking means ( 8 , 18 ) is at least largely prevented and in which liquid gas is removed for a consumer in terms of flow between the heat exchanger and the blocking means ( 8 ) which prevents the backflow of liquid gas into the storage container ( 2 '). 13. The method according to any one of claims 10 to 12, characterized by the Use in gas or liquid gas supply for vehicle engines.