EP1466122A1

EP1466122A1 - Method for filling a storage tank with a gaseous fuel

Info

Publication number: EP1466122A1
Application number: EP03729429A
Authority: EP
Inventors: Robert Adler
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2002-01-15
Filing date: 2003-01-07
Publication date: 2004-10-13
Also published as: AU2003235622A1; DE10201273A1; WO2003060374A1

Abstract

The invention relates to a method for filling a storage tank, in particular a motor vehicle storage tank with a gaseous fuel, in particular with gaseous hydrogen, at a pressure in excess of 300 bar, whereby the fuel is compressed and temporarily stored. According to the invention, the condensed fuel is stored temporarily at one or more pressure levels and during the filling process, the storage tank to be filled is filled from one temporary storage container if the fuel is stored at one pressure level and from one or more temporary storage containers if the fuel is stored at more than one pressure level, said filling process preferably starting with the temporary storage container that has the lowest pressure level. Once the pressure between the storage container to be filled and the temporary storage container or containers has equalised, said storage tank is filled at a final pressure by means of at least one compressor, which compresses the gaseous fuel from the temporary storage container or containers.

Description

description

Process for filling a storage tank with a gaseous fuel

The invention relates to a method for refueling a storage container, in particular a motor vehicle storage container, with a gaseous fuel, in particular with gaseous hydrogen, to a pressure of more than 300 bar, the fuel being compressed and temporarily stored.

In the following, the letters "G" for "gaseous" and "L" for "liquid" or "liquid" are prefixed in the names of special cryogenic media according to their physical state; for example GH ₂ or LH ₂ for gaseous or liquid hydrogen. The term "CNG" is also used for compressed natural gas.

Hydrogen in particular is currently becoming increasingly important as an energy source due to increasing energy requirements and increased environmental awareness. Aircraft, ships, submarines, trucks, buses and passenger cars are already being piloted using hydrogen-powered turbines or engines.

Furthermore, vehicles are already being tested in the field, in which electrical energy is generated by means of a fuel cell, which in turn drives an electric motor. The hydrogen required to operate the fuel cell is stored in these vehicles either in liquid or gaseous and compressed form.

Generic methods for refueling storage tanks with gaseous hydrogen at a pressure of more than 300 bar - usually around 450 bar pressure have already been realized in the storage tank to be refueled - have the disadvantage that the gaseous fuel initially has a pressure of about 500 bar compressed and then on this pressure

(intermediate) must be saved so that it is possible to refuel one or more vehicles in a short time at any time. A disadvantage of this procedure, however, is that the entire amount of gas must be compressed to the high pressure and stored. The storage containers or bundles required for this are comparatively expensive; furthermore, they must be sized accordingly.

The object of the present invention is to provide a generic method for refueling a storage container, in which the aforementioned disadvantages can be avoided. In addition, the power consumption required for the compression of the gaseous fuel should be reduced and the refueling temperature should be reduced by approx. 20 to 30 ° C.

To achieve the aforementioned object, a generic method for refueling a storage tank is proposed, which is characterized in that - the compressed fuel is temporarily stored at one or more pressure levels, the storage tank to be refueled during the refueling process in the event of a pressure level from the buffer store or in the case several pressure levels is refueled from the intermediate store or stores, preferably with the one located at the lowest pressure level

Intermediate storage is started, and after reaching a compensating pressure between the storage tank to be refueled and the one or more intermediate stores, the filling of the storage tank to be refueled to the final pressure by means of at least one compressor which removes the gaseous fuel from the or at least one of the

Intermediate storage compressed, takes place.

In practice, three or more intermediate pressure levels are preferably provided in practice, in particular when refueling a storage container with gaseous hydrogen.

However, the provision of only one intermediate storage pressure level can represent a comparatively inexpensive and technically satisfactory solution, for example when refueling a storage container with CNG. The method according to the invention for refueling a storage tank is therefore proposed that the compressed fuel be temporarily stored at a low, medium and high pressure level, - the storage tank to be refueled during the refueling process is first refueled from the low-pressure level store and then from the medium-pressure level store and after reaching a compensating pressure between the storage tank to be refueled and the medium-pressure level store, filling the storage tank to be refueled to the final pressure by means of at least one

Compressor, which compresses the gaseous fuel from the medium-pressure level storage.

The method according to the invention and further refinements of the same, which are the subject matter of the subclaims, are explained in more detail below with reference to the exemplary embodiment shown in the figure. The figure shows the schematic structure of a gas station for gaseous hydrogen, in which the method according to the invention can be implemented with three intermediate pressure levels.

Via line 1, hydrogen is fed to a buffer 2 at the suction point at a pressure of 3 to 20 bar. From this, the required hydrogen is drawn off via line 3 and fed to the first stage 4 of a two-stage compressor system. In this first stage 4, the hydrogen is compressed to a pressure between 17 and 150 bar. The compressed hydrogen is then fed via line 5 to a cooler 6 and cooled to a temperature between 20 and 60 ° C. in the latter. The compressed hydrogen stream is then fed via line 7 to the second compressor stage 8 and compressed to a pressure of 300 bar. Again, the compression heat is removed in an aftercooler (not shown in the figure) before the compressed hydrogen is fed via lines 9 and 12 to two stores 10 and 13 - which will be discussed in more detail below.

The stage pressure ratio of the compressor stages 4 and 8 will be determined by the inlet pressure of the hydrogen prevailing in line 1. The compressors 4 and 8 work on electricity consumption. They are preferably driven hydraulically and cooled with hydraulic oil in the outer jacket. An approximately isothermal compression of the gaseous hydrogen can thereby be achieved.

The compressed hydrogen is stored in both stores 10 and 13

(Between) are stored. The stores 10 and 13 are constructed, for example, from six bundles each with a geometric volume of 600 l each. With a filling pressure of 300 bar and a compressibility factor of approx. 0.9, this results in a filling volume of approx. 162 m ³ hydrogen per bundle. The stores 10 and 13 thus each have a capacity of 972 m ³ .

In the following, the store 10 will be referred to as a low-pressure level store and the store 13 as a medium-pressure level store.

The required compressor capacity in normal operation is approx. 300 Nm ³ at an inlet pressure of 15 bar. This requires an electrical output of 46 KW, which results in a specific electricity requirement of 0.15 KWh / Nm ³ .

When the hydrogen filling station is ready for operation, the two stores 10 and 13 are filled with 300 bar of hydrogen.

In addition, a further store 18 - hereinafter referred to as a high-pressure level store - is provided, which is filled with gaseous hydrogen at a pressure of 450 bar. The memory 18 consists, for example, of a 50 liter buffer bottle.

According to advantageous embodiments of the method according to the invention, the storage pressure of the low-pressure level store 10 is between 150 and 300 bar, the storage pressure of the medium-pressure level store 13 is between 200 and 300 bar and the storage pressure of the high-pressure level store 18 is between 400 and 450 bar.

The maximum storage volume of the high-pressure level store 18 is preferably 1 to 10% of the maximum storage volume of the low-pressure level store 10 and preferably 1 to 10% of the maximum storage volume of the medium-pressure level store 13. The stores 10, 13 and 18 are connected via extraction lines 11, 14 and 19 to a common line 15 leading to the refueling coupling.

In the case of refueling, the initial pressure in the storage tank to be refueled - that is, for example, the motor vehicle storage tank - is first determined using a test burst. A heating curve is calculated from this pressure and compared with the outside temperature, which results in the filling pressure. This test surge is fed from the high-pressure level store 18. Due to the associated drop in pressure in the high-pressure level store 18, the compressors 4 and 8 are switched to the so-called high booster mode.

According to the invention, the hydrogen compressed and stored to at least three pressure levels - namely the low 10, the medium 13 and the high pressure level 18 - is initially extracted from the low pressure level accumulator 10 during the refueling process and then from the medium pressure level accumulator 13 via the extraction lines 11 and 14 as well 15 relaxed in the storage tank to be refueled and this filled at least up to the highest pressure prevailing in the medium pressure level storage 13.

Here, the maximum flow is preferably regulated to 90 m ³ / min. When filling an empty vehicle storage tank, the hydrogen is regulated to approx. 250 bar so that the maximum flow rate is not exceeded even at a high differential pressure. During the subsequent filling to maximum pressure (for example 450 bar), the controller (not shown in the figure) is switched off by a control valve (also not shown in the figure).

After reaching the equilibrium pressure between the storage tank to be refueled and the medium-pressure level store 13, the storage tank to be refueled is filled to the final pressure in that the second compressor stage 8 takes the gaseous hydrogen from the line 16

Medium-pressure level accumulator 13 sucks, compressed to, for example, 450 bar and fed via lines 17 and 15 to the refueling coupling and via this to the storage tank to be refueled; During this process step, the compressor 8 operates in the so-called high booster mode. The inlet pressure of the second compressor stage 8 should preferably be at least 150 bar. In high booster mode, an electrical output of va. 85 KW needed. The filling capacity in high booster mode is at least 32.5 Nm ³ hydrogen / min and a maximum of 43 Nm ³ hydrogen / min.

Due to the previous removal of hydrogen from the medium pressure level store 13, the hydrogen still contained therein is supercooled; it has a temperature of approx. - 40 ° C. The outlet temperature of the second compressor stage 8 is therefore approx. 10 ° C., as a result of which a comparatively efficient filling of the storage tank is achieved at approx. 350 bar.

The second compressor stage 8 works only approx. 30% of the total refueling time in high booster mode. The electricity consumption per Nm ^{3 of} hydrogen in high booster mode is - based on the total gas volume - approx. 0.015 KWh / Nm ^{3 of} hydrogen. Therefore, the total electricity requirement of the method according to the invention at a refueling pressure of 350 bar is 0.165 KWh / Nm ³ hydrogen.

In order to fill up the high-pressure level store 18, hydrogen is supplied to the second compressor stage 8 via lines 17 and 17 ′ in high booster mode. A removal of the compressed hydrogen from the

High-pressure level store 18 - for example for the test burst described above - takes place via lines 19 and 15.

The method according to the invention also has the advantage that conventional flow meters can be used. So far have been verified

Flow meters only available for pressures up to 300 bar. Thus, no calibrated flow meters could be used in the refueling processes, which are part of the prior art and in which the entire amount of hydrogen was compressed to pressures of up to 500 bar. Since in high booster mode the maximum storage pressure is approx. 300 bar and the compressor 8 at this pressure from the

Medium pressure level accumulator 13 sucks, conventional, calibrated flow meters can be provided on the suction side of the compressor 8 - that is, for example, in the line 16. The method according to the invention thus makes it possible, for example, to fill two buses in succession. A third bus can then be refueled either more slowly or in the same refueling time of approx. 10 min after a waiting time of 1.6 hours. These refueling times are based on a refueling quantity of 500 Nm ³ hydrogen and are dependent on the storage volume of the low and medium pressure level storage.

The entire two-stage compressor station is preferably housed in a concrete housing consisting of an electrical and a gas space. The concrete housing is made explosion-proof - as is the case with gas control stations.

The hydraulic unit and the entire electrical installation are housed in the electrical room. The compressor stages are driven by hydraulic oil in the explosion-protected part of the housing (gas space). All cable bushings should be gastight. In the gas room, all installations must be carried out in accordance with ExZone 1. A pressure relief flap is expediently located in the roof of the gas space. Furthermore, the room air in the gas room should be monitored for hydrogen leakage. A hydrogen leak then leads to the compressor station being switched off and the individual sections being sealed off via pneumatic quick-closing valves.

Claims

claims

1. A method for refueling a storage container, in particular a motor vehicle storage container, with a gaseous fuel, in particular with gaseous hydrogen, to a pressure of more than 300 bar, the fuel being compressed and temporarily stored, characterized in that

- the compressed fuel is temporarily stored at one or more pressure levels,

- The storage tank to be refueled during the refueling process in the case of a pressure level from the intermediate store or in the case of several

Pressure levels from the intermediate store or stores is refueled, preferably starting with the intermediate store located at the lowest pressure level, and

- After reaching a compensating pressure between the storage tank to be refueled and the intermediate store or stores, the storage tank to be refueled is filled to the final pressure by means of at least one compressor which compresses the gaseous fuel from or at least one of the intermediate stores.

2. The method according to claim 1, wherein three buffer pressure levels are provided, characterized in that

- The compressed fuel is temporarily stored at a low (10), a medium (13) and a high pressure level (18), - The storage tank to be refueled during the refueling process first from the low pressure level store (10) and then from the medium pressure level store (13 ) is refueled and

- After reaching a compensating pressure between the storage tank to be refueled and the medium-pressure level store (13), the filling of the storage tank to be refueled to the final pressure by means of at least one

Compressor (4, 8), which compresses the gaseous fuel from the medium-pressure level store (13).

3. The method according to claim 2, characterized in that the storage pressure of the low pressure level (10) is between 150 and 300 bar, the storage pressure of the medium pressure level (13) is between 200 and 300 bar and the storage pressure of the high pressure level (18) between 400 and 450 bar.

4. The method according to claim 2 or 3, characterized in that the maximum storage volume of the high pressure level (18) is 1 to 10% of the maximum storage volume of the low pressure level (10).

5. The method according to any one of claims 2 to 4, characterized in that the maximum storage volume of the high pressure level (18) is 1 to 10% of the maximum storage volume of the medium pressure level (13).

6. The method according to any one of claims 1 to 5, characterized in that the compression (4, 8) of the gaseous fuel takes place essentially isothermally.

7. The method according to any one of claims 1 to 6, characterized in that the filling of the storage tank to be refueled to the final pressure by means of at least one compressor (8) and / or a compressor stage, or the compression of the gaseous fuel before it is temporarily stored serves, takes place.