Fluent material handling – with receiver or receiver coacting mea – Processes – Filling dispensers
Reexamination Certificate
2003-04-09
2004-09-21
Huson, Gregory L. (Department: 3751)
Fluent material handling, with receiver or receiver coacting mea
Processes
Filling dispensers
C141S004000, C141S018000, C141S047000, C141S094000
Reexamination Certificate
active
06792981
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for introducing a compressed gas into a pressure vessel in which a gas is compressed in initial and final compression stages which can be powered by a common source. More particularly, the present invention relates to such a method and apparatus in which the compressed gas is produced by compressing a higher pressure gas stored in a higher pressure storage bank which is charged in part by compressing a lower pressure gas in the final compression stage. Even more particularly, the present invention relates to such a method and apparatus in which the gas is hydrogen and the pressure vessel is a vehicle fuel tank.
BACKGROUND OF THE INVENTION
There exists a variety of industrial requirements for introducing compressed gases into pressure vessels, for instance, industrial gases and fuels such as compressed natural gas and hydrogen. With respect to hydrogen, there has been an increased interest in utilizing hydrogen as a fuel for internal combustion engines and fuel cells such as found in automobiles and buses. In order to store sufficient amounts of hydrogen to make the utilization of hydrogen practical for such purposes, the hydrogen must be stored in the vehicle fuel tank at high pressure, typically in excess of 5000 psig.
One important aspect in making the use of hydrogen practical is to provide equipment to conduct a filling operation that closely matches consumer expectations with respect to conventional fossil fuel filling. This expectation involves filling vehicle fuel tanks with hydrogen in between about 3 and about 5 minutes. Such rapid hydrogen filling can be accomplished with the use of high pressure cascaded storage tanks that sequentially dispense the hydrogen at high pressure. In cascade filling, when a consumer arrives at the filling station and connects a transfer hose to his or her vehicle, the fuel tank is connected to one of the cascaded storage tanks. Hydrogen flows out of the storage tank until pressure between the vehicle storage tank and the hydrogen storage tank equalizes. Hydrogen is then dispensed from another storage tank in the cascade to complete the filling of the tank. When one tank is dispensing, another tank can be filled or topped off with hydrogen.
The problem with cascade dispensing, as described above, is that the compressor that is used in connection with the filling of the cascaded tanks cannot be efficiently designed in that it has to be sized to compress the hydrogen from a low pressure to a high pressure to completely fill a tank and also to compress hydrogen from a medium pressure to a high pressure after a tank has undergone pressure equalization with a vehicle fuel tank. Hence, the compressor is oversized with respect to operations in a range from medium pressure to high pressure. Moreover, if the hydrogen is to be made on site, by for instance electrolysis, there are periods of time in which such equipment is not efficiently utilized in that the equipment must be turned down or off between filling periods.
Another large disadvantage with cascade dispensing is that direct tank to tank pressure transfer results in a lower pressure level in the vehicle as compared to the highest pressure storage bank. Assuming the banks are not re-pressurized between vehicle fills, any subsequent vehicle final pressure will be lower than the previous vehicle. This pressure decrease can be minimized by with the use of large storage volumes (higher capital and larger footprint penalty). As an option, the product compressor can be used to top off the vehicle tanks once the pressure transfers from the cascade banks are completed, however, this top off fill could take a considerable amount of time relative to consumer “fast fill” expectations.
The problem of dispensing fuels at high pressure has been encountered in connection with compressed natural gases. For instance in U.S. Pat. No. 5,351,726, a compressed natural gas refueling system is disclosed in which a single stage hydraulic compressor is provided to operate at suction pressures ranging from about 330 psig up to about 3600 psig and at discharge pressure ranging from 330 psig to 4500 psig. Compressed natural gas is supplied to an intermediate pressure storage tank at an intermediate pressure that is above the inlet source pressure for the natural gas. When vehicles are to be refueled, the vehicle is first refueled directly from the intermediate pressure storage tank. After equalization of pressure, the compressor compresses gas from the intermediate storage tank to the vehicle fuel tank to complete the refueling operation. Since the compressor does not have to function to compress natural gas from the supply pressure to the vehicle fill pressure at one time, the compressor itself can be a more compact energy efficient unit than a compressor size that would otherwise be required for such application.
In hydrogen filling applications, the hydrogen fill pressures are higher than those of the prior art involved in compressed natural gas. In addition, as with any vehicle filling station, footprint size becomes paramount. In addition, while there exists many sources of natural gas, hydrogen must be delivered and stored on site or at least made on site. In order to efficiently utilize systems that involve the manufacture of hydrogen on site, it is more efficient to allow for a continual utilization of the generation facilities. For instance, a facility that is designed to supply hydrogen on demand must be sized larger than a facility that continually supplies a nominal amount of hydrogen.
As will be discussed, the present invention provides a method of filling a vehicle fuel tank with hydrogen in which hydrogen sources can be continually used and that allows compact compression systems to be fabricated that are capable of compressing the hydrogen to the high vehicle fill pressures.
SUMMARY OF THE INVENTION
The present invention provides a method of introducing a compressed gas into a pressure vessel. In accordance with the method, a feed stream of a gas is compressed in an initial compression stage to form a lower pressure gas stream. During introduction of the compressed gas into the pressure vessel, a lower pressure storage bank is charged with the lower pressure gas stream, thereby to store lower pressure gas. Additionally, a compressed gas stream and therefore, the compressed gas, is introduced into a pressure vessel. The compressed gas stream is formed by compressing a stream of higher pressure gas in a final compression stage. The higher pressure gas is stored in a higher pressure storage bank.
During periods between the introduction of the compressed gas into the pressure vessel, the higher pressure storage bank can be charged with the compressed gas stream. The compressed gas is formed by compressing a combined stream in the final compression stage. The combined gas stream is composed of the lower pressure gas stream and a stream of stored lower pressure gas from the lower pressure storage bank.
The present invention advantageously allows the feed stream to be continually compressed and therefore continuously utilized. As will be discussed, the present invention has particular application to hydrogen fueling operations. As can be appreciated, since the source of hydrogen, for instance, an electrolysis unit or a steam methane reformer, can be made to continually produce said feed stream to be compressed, the source itself can be more fully utilized than prior art systems in which hydrogen is produced, stored and then dispensed. This allows the hydrogen source to be operated at a lower energy input, for instance, electricity in the case of electrolysis unit, or the source unit to be of a lessor scale than otherwise would have been required had the source unit been designed for intermittent operation. It is to be noted that the present invention also contemplates discontinuous operation.
The charging of a higher pressure storage bank can further comprise initially compressing the combined gas stream in the final compression st
Abdelwahab Ahmed
Bollinger Robert B.
Manning Michael S.
Smolarek James
deVore Peter
Huson Gregory L.
Praxair Technology Inc.
Rosenblum David M.
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