WO2006082122A1

WO2006082122A1 - Method and device for filling pressure vessels with non-liquefied gases or gas mixtures

Info

Publication number: WO2006082122A1
Application number: PCT/EP2006/050166
Authority: WO
Inventors: Herrmann Grabhorn; Friedhelm Herzog
Original assignee: Messer Group Gmbh
Priority date: 2005-02-02
Filing date: 2006-01-11
Publication date: 2006-08-10
Also published as: EP1846691A1; EP1846691B1; ATE519065T1; DE102005004665A1

Abstract

In order to be able to achieve high pressures, pressure vessels are filled according to the principle of 'cold filling', i.e. the filler gas is filled into the pressure vessel in a cold state. Once the pressure vessel is filled and the gas is heated to ambient pressure, the pressure in the pressure vessels multiplies several times. A problem that often occurs is that during filling the filler gas or a component of the filler gas mixture freezes out, thereby resulting in a malfunction of the filling device. For this purpose, the filler gas is transported to the pressure vessel to be charged in a cold yet gaseous state. The filler gas is supplied to a heat exchanger in a liquefied state and is then evaporated. The evaporated filler gas or the gas component are returned to the heat exchanger, where it thermally contacts the still liquid filler gas and is cooled to at least approximately the temperature of the liquid filler gas. The gas treated in this manner is very cold but at the same time available in a gaseous state of matter.

Description

Method and device for filling pressure vessels with non-liquefied gases or gas mixtures

The invention relates to a method and a device for filling of pressure vessels with cold gas or gas mixture, in which a Füügas or a component of Füllgasgemisches stored in a reservoir at low temperatures in the liquefied state and fed to a pressure vessel for filling.

In order to store gases with a high storage density, storage takes place either in the liquid state or in gaseous form under high pressures. Although the storage in the liquid state allows a very high storage density, but it is only at the cost of more or less large evaporation losses possible, which are unavoidable even with well-insulated containers.

Up to now compressors have mainly been used for pressure storage of gases, which allow an operating pressure in the pressure vessel of about 200 bar. However, the compressors are very complex in construction and operation, also recent applications, such as applications in the fuel tent technology or gas generators for airbags, the need for much higher pressures of 700 bar or more. Such pressures can not be realized with conventional compression technology or only with unreasonably high costs.

From EP 0 033 386 A1 and WO 99/05465 methods for filling pressure vessels are known in which the Füligas is liquefied before being fed to the pressurized container to be geflienden or cooled to a temperature which is only slightly above its boiling temperature. From WO 02/066884 AI a further improved method is known in which the pressure vessel is cooled before and / or during the supply of cold or liquefied filling gas, for example by immersion in a bath in liquid Nitrogen. After completion of the filling process, the pressure vessel is sealed pressure-tight. Since the gas volume with the cooling - while maintaining the pressure - approximately proportional to the temperature behaves, succeeds in this way an increase in the effective storage capacity by a factor of about 2-3. As the gas warms up, the pressure in the pressure vessel rises sharply. These methods are suitable, for example, to inexpensively handle pressure vessels approved for pressures of 70 bar or more. In particular, this method is suitable for affirming small-volume tanks, in particular gas generators for airbags, fuel tanks for gas-powered vehicles or fuel cell systems.

The known methods have the disadvantage that during the fusing process, condensation or freezing of the filling gas or a filling gas component can occur. While the condensation in the interior of the pressure vessel to be filled is usually unproblematic or even intended, freezing of the gas in the supply lines to the pressure vessel can lead to closure of the supply line.

In order to avoid freezing of the filling gas, the filling gas stored in the liquid state can be vaporized and heated by means of a heat exchanger before it is fed to the pressure vessel. The disadvantage of this is that the temperature of the vaporized filling gas is difficult to control, which results in a deterioration of the result.

Object of the present invention is therefore to provide a way to fill pressure vessels with cold, non-liquefied gas, in which a condensation or freezing of the filling gas or a Füllgaskomponente is reliably avoided.

This problem is solved in a method of the type mentioned in that the filling gas or Füllgaskomponente supplied from the reservoir prior to its delivery to the pressure vessel in the liquefied state a heat exchanger, and evaporates the vaporized filling gas or vaporized Füllgaskomponente heat exchanger surfaces of the heat exchanger in thermal contact with the liquefied Füilgas or the liquefied Füllgaskomponente is brought from the reservoir.

The vaporized filling gas is thus cooled by the heat exchange with the still liquid Füilgas and then fed to the pressure vessel to be filled. During evaporation, the filling gas is at least as much energy supplied as it corresponds to its enthalpy of vaporization. During cooling by the thermal contact with the still liquid Füligas this enthalpy of vaporization can not be removed from it, however. The temperature of the vaporized filling gas approaches the temperature of the still liquid fill gas, without the vaporized filling gas condensing again. The degree of convergence of the temperatures of the vaporized Füälgases to the still liquid filling gas depends inter alia on the structure of the heat exchanger, the heating power used for heating the gas and the flow rate. In the ideal case, which is of course not fully achievable under realistic conditions, the temperatures are the same and the energy contents of the evaporated or still liquid filling gas differ only by the enthalpy of vaporization. It does not matter, in a soft way, the amount of energy corresponding to the enthalpy of evaporation is supplied to the filling gas. A thermal contact with another medium, either fluidly separated on heat exchanger surfaces or without material separation, such as by mixing, is considered as well as an active heating, for example by an electric or other heating device, or a combination of different heaters.

In order to keep the temperature of the vaporized gas as low as possible, it is expedient to regulate the heating power and / or the flow rate of the fill gas through the heat exchanger for heating the filling gas in dependence on the temperature of the filling gas. This keeps the heating costs as low as possible. The temperature used as a control variable can be detected in the heat exchanger, in a connecting line between the thermally interconnected sections of the heat exchanger or in a filling line, downstream of the heat exchanger. Alternatively, the proportion of still liquid gas can be measured at the filling gas and taken as an output for adjusting the heating power. The measurement of the liquid fraction is preferably carried out in the region of the outlet of the first section of the heat exchanger.

A further advantageous embodiment of the method according to the invention provides that the fill gas is released before it is fed to the pressure vessel. Due to the boiling point depression occurring during the expansion, it is thus avoided that condensation of the fill gas occurs due to a sudden pressure fluctuation in the lines. A particularly advantageous variant for the vaporization of the filling gas is to heat the filling gas to be vaporized leaving the heat exchanger by admixing a warmer additional gas of the same or a different composition. The energy required for evaporation receives the fill gas from the admixed additional gas.

The object of the invention is also achieved in a device for loading of Druckbehälterπ with cold gas or gas mixture in which a Fϋllgas or a component of a filling gas mixture stored in a reservoir in the liquefied state and fed to a pressure vessel for filling, achieved in that between reservoir and A heat exchanger with thermally interconnected sections is provided pressure vessel, wherein a first portion of the heat exchanger via a Füllgaszuleitung with the reservoir and a second section via a Füllgasableitung with the BefÃ¼ileinrichtung is fluidly connected and between the first and the second section is a connecting line and means for Heating the filling gas is provided.

The filling gas or the filling gas component thus first passes through the first section of a heat exchanger and is at least partially evaporated by the thermal contact with the vaporized filling gas from the second section of the heat exchanger. The device for heating the filling gas, which may be arranged within the first section of the heat exchanger or in the connecting line between the two sections of the heat exchanger, causes the supply of energy to the filling gas, which corresponds at least to the enthalpy of vaporization. In the second section of the heat exchanger, which is thermally connected to the first section, the temperature of the vaporized filling gas is approximated to the temperature of the still liquid filling gas,

Advantageously, a controllable heating device is provided as means for heating the filling gas, which is data-connected with sensors for detecting physical parameters of the filling gas, such as temperature or pressure. An expedient embodiment of the device according to the invention provides that a pressure stage is arranged in the connecting line and / or in the Füllgasabieitung. The pressure stage, which is, for example, a pressure reducer or a controllable throttle valve, ensures the maintenance of the gaseous state of the downstream of the pressure stage filling gas also in the case of pressure fluctuations in the Füllgaszuleitung to be filled pressure vessel due to the lowered due to the relaxation boiling point. By installing the pressure stage, the heating power of the filling gas can also be set to a value which is lower than the enthalpy of vaporization, provided that the requirement is satisfied that the filling gas is in the gaseous state at the reduced pressure and the energy supplied to it.

Advantageously, the connecting line with a gas supply flow s- connected, by means of which an additional gas can be fed into the Verbindungsieitung. In this way, in particular filling gas mixtures can be prepared in a simple manner and without the risk of condensation of a Füligaskomponente. The additional gas can also be used to heat the filling gas.

Reference to the drawings, an embodiment of the invention will be explained in more detail.

The device 1 shown schematically in the drawing (Fig.) Is used to fill pressure vessels 2 in a Befülieinrichtung 3 with a filling gas mixture.

The Befülieinrichtung 3 itself is a known device, as it is described for example in WO 02/066884. The components of the filling gas mixture - in the embodiment argon (Ar) and helium (He) - are stored in storage containers 4,5. While in the reservoir 5 helium is stored under pressure in the gaseous state at temperatures of, for example, 20 ° C, the argon is in the reservoir 4 in the cryogenic, liquefied state. Incidentally, the storage containers 4, 5 are commercially available containers for the storage of gases, which in a known manner are not shown here with fittings, such as shut-off valves, pressure relief valves, pressure reducers and the like. are equipped dergl. The reservoir 4 is fluidly connected via a thermally insulated Füllgaszuleitung 6 with a heat exchanger 7. The heat exchanger 7 comprises two fluidically separated sections, here referred to as primary section 8 and secondary section 9, which are thermally connected to each other via a heat exchanger surface 10. While the primary section 8 of the heat exchanger 7 is fluidly connected to the Füllgaszuleitung 8, the secondary section 9 is connected via a likewise thermally insulated Füllgasableitung 12 with the filling device 3 and thus the pressure vessels 2 to be filled. The primary section 8 of the heat exchanger 7 has an output which is flow-connected via a connecting line 13 to an input of the secondary section 9. At or in the connecting line 13, the devices described below are provided.

In the vicinity of the output of the primary section 8 of the heat exchanger 7, for example, directly at the output of the primary section 8. In the Verbindungsieitung 13, an electric heater 15 is arranged to heat the filling gas. The heating device 15 is provided with a measuring and control device 14, by means of which the output to the Füilgas heating power is regulated in dependence on the temperature of the filling gas. The temperature of the filling gas used as a controlled variable is measured by means of a sensor 16 in a section of the connecting line 13 located downstream of the heating device 15. Downstream of the heater 15, an arrangement 17 is provided in the embodiment for reducing pressure, by means of which the pressure of the filling gas can be lowered by a predetermined value. The arrangement 17 may be, for example, a pressure reducer or a controllable throttle valve. Downstream of the arrangement 17 opens into the connecting line 13 at a junction 18, a gas supply 19, which is connected to the reservoir 5 for a further filling gas component, helium in the exemplary embodiment, flow-connected. In the gas supply line 19, an arrangement 20 is also provided for reducing pressure. Furthermore, 16 shut-off valves 22,23 are arranged in the connecting line 13 and the gas supply line.

When operating the device 1 is provided as a filling gas liquefied argon from the reservoir 4 via the Füllgaszuleitung 6 the primary section 8 of the Heat exchanger 7 supplied. There takes place due to the thermal contact with the secondary portion 9 of the heat exchanger 7, an at least partial evaporation of the filling gas. Subsequently, the filling gas of the heater 15 is supplied, which supplies the filling gas with an energy which corresponds at least to the enthalpy of vaporization, ie, at the latest downstream of the Heizeinήchtung 15, the filling gas is completely evaporated. Via the connecting line 13, the vaporized FülSgas is passed into the secondary section 9 of the heat exchanger 7 and reaches there on the heat exchanger surface 10 in thermal contact with the still liquid filling gas in the primary section 8 of the heat exchanger 7. Due to the thermal contact, the gaseous filling gas cools down in the Idealfail down to the temperature of the still liquid filling gas, but can not condense due to the temperature and pressure conditions itself. The filling gas is thus in a very cold, but gaseous state. In this state, the filling gas is supplied to the pressure vessels 2 via the isolated Füllgasableitung 12 for filling, A provided in the Füligasableitung 12 pressure buffer 22 serves to dampen possible pressure fluctuations in the Füilgasableitung 12, which may arise during the filling of the pressure vessel 2, and to equalize the Befülivorgang overall. After completion of the filling and the closing of the pressure vessel 2, the filling gas in the pressure vessels 2 gradually heats up to ambient temperature and increases its pressure considerably. If, for example, the pressure vessels 2 to be filled are cooled, for example with liquid nitrogen, and thus condenses the gas inside the pressure vessel 2 during filling, pressures can be achieved after closure of the pressure vessel 2 and its subsequent heating to ambient temperature, which reduces the inlet pressure by several hundred times exceed. Even pressure vessels designed for maximum pressures can be filled with gas whose pressure during filling is in the range of atmospheric pressure or only a few bar (10 ° Pa).

To produce a filling gas mixture, in the exemplary embodiment of an argon-helium mixture, an additional filling gas component - in the example Heiium - fed from the reservoir 5 via the gas supply line 19 in the connecting line 13 and mixes there with the vaporized filler gas - in the example argon. By a suitable adjustment or selection of the arrangements 17. 20 for pressure reduction, a desired mixing ratio between the components is set. Mitteis the shut-off valves 22,23, the supply of a Füllgaskomponente temporarily be completely prevented. If the additional filling gas component supplied via the gas feed line 19 has a higher temperature than the boiling temperature of the fill gas in the storage container 4, the use of the heating device 15 can be completely or partially dispensed with. The energy necessary for the evaporation is then transferred to the filling gas in whole or in part from the additional filling gas component. The filling gas mixture then passes into the secondary section 9 of the heat exchanger 7, where it is cooled as described above and passed to the filling device 3. In the above-described arrangement, the boiling point of the additional filling gas component stored in the storage tank 5 should be lower than that of the filling gas stored in the storage tank 4. If this is not the case, it must be ensured that the cooling of the filling gas mixture in the heat exchanger 7 does not result in the condensation of the additional filling gas component. This is achieved in that in this case the system, for example by means of the heater 15, a correspondingly higher energy is supplied, which prevents the condensation of the additional Füilgaskomponente.

In the context of the invention, the additional fill gas component or further filling gas components can also be added to the filling gas at another point (not shown here), in particular downstream of the secondary section 9 of the heat exchanger 7.

In the exemplary embodiment, the pressure of the filling gas in the connecting line to the arrangement 17 is reduced. Due to the boiling point reduction associated with the pressure drop, it is ensured that condensation is always reliably prevented even in the case of pressure fluctuations in the filling gas discharge line 12.

By filling the pressure vessel 2 with very cold gaseous filling gas or Füiigasgemisch 2 pressures of / OObar and more can be achieved after completion of the filling process, the closing of the pressure vessel and the subsequent heating of the pressure vessel 2 to ambient temperature without great equipment expense in the Druckbehäitem. The device 1 is therefore particularly suitable for filling of gas generators for airbags. LIST OF REFERENCE NUMBERS

1. Device

2. Pressurized container

3. Befülieinrichtung

4. Storage container

5. Reservoir

6. FülSgasleituπg

7. Heat exchanger

8. primary section (of the heat exchanger)

9. secondary section (of the heat exchanger)

10. Heat exchanger surface 11 -

12. Fill gas discharge

13. Linking rescue

14. Measuring and control device

15. Heating device

16. Temperature sensor

17. Arrangement for reducing pressure

18. Junction

19. Gas supply

20. Arrangement for reducing pressure

21. -

22. Print buffer

23. shut-off valve

24th stop valve

Claims

claims

1. A method for filling pressure vessels with cold gas or gas mixture in which a filling gas or a component of a Füligasgemisches stored in a reservoir (4) at low temperatures in the liquefied state and a pressure vessel (2) is fed to the filling, characterized in that the filling gas or the filling gas component from the storage container (4) is supplied to a heat exchanger (7) in the liquefied state before it is fed to the pressure vessel (2), and the vaporized filling gas or the vaporized filling gas component is heated at heat exchanger surfaces (10) of the heat exchanger (7). brought into thermal contact with the liquefied filling gas or the liquefied filling gas component from the reservoir (4).

2. The method according to claim 1, characterized in that the heating of the filling gas and / or the mass flow of Fϋllgases by the heat exchanger (7) is regulated in dependence on the temperature of the filling gas.

3. The method according to claim 1 or 2, characterized in that the filling gas is expanded before it is fed to the pressure vessel (2).

4. The method according to any one of the preceding claims, characterized in that the heating of the filling gas is effected by the admixture of an additional gas.

5. A device for filling pressure vessels with cold gas or gas mixture, in which a filling gas or a component of a filling gas mixture stored in a reservoir (4) in the liquefied state and for filling a pressure vessel (2) is supplied, characterized in that between reservoir ( 4) and pressure vessel (2) a heat exchanger (7) with thermally interconnected sections (8,9) is provided, wherein a first section (8) of the heat exchanger via a FüllgasΣuleitung (6) with the reservoir (4) and a second section (9) via a Füllgasableitung (12) with the filling device (3) is strömungsverfaunden and between the first section ( 8) and the second section (9) is a connecting line (13), and means (15) for heating the filling gas is provided.

6. The device according to claim 5, characterized in that as means (15) for heating the filling gas, a controllable heating device is provided, which is data-connected with sensors (16) for detecting physical parameters of the FüSIgases, such as temperature or pressure.

7. Apparatus according to claim 5 or 6, characterized in that in the connecting line (13) and / or in the Füllgasableitung a Drucksiufe (17) is arranged.

8. Device according to one of claims 5 to 7, characterized in that the connecting line (13) with a gas supply line (20) is fluidly connected, Mitteis a ZusatΣgas in the connecting line (13) can be fed,