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  Device for generating highly compressed gasUSPTO Application #: 20070248472Title: Device for generating highly compressed gas Abstract: In order to generate a highly compressed gas, a multistage high-pressure compressor is used, which has a number of 3 compressor stages (10a, 10b, 10c, 10d). A vortex tube (20a, 20b, 20c, 20d) is connected downstream from these compressor stages (10a, 10b, 10c, 10d). The pressure difference between the pressure line (4) of the high-pressure compressor and the compressed gas reservoir (7) to be filled is used for driving, together with an expansion turbine (5), a pre-compressor (2) for pre-compressing the gas before entering the first compressor stage (10a). Alternatively, a vortex tube for cooling gas can be mounted between the last compressor stage (10d) and the compressed gas reservoir (7). The inventive device permits a direct filling of a compressed gas reservoir in order to reach a limit value of the pressure in the compressed gas reservoir at a predetermined limit temperature, said limit value being stipulated according to the technical rules. (end of abstract)
Agent: Renner Otto Boisselle & Sklar, LLP - Cleveland, OH, US Inventors: Klaus Bãumer, Dirk Grullch, Norbert Schoiz, Herbert Wlegand USPTO Applicaton #: 20070248472 - Class: 417251000 (USPTO) Related Patent Categories: Pumps, Successive Stages, With Interstage Discharge Or Additional Discharge From Former Stage The Patent Description & Claims data below is from USPTO Patent Application 20070248472. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The invention refers to a device for generating highly compressed gas with a single-stage or a multistage compressor. Besides various other applications, the present device is useful in a gas fueling system for fueling vehicles running on natural gas, methane or similar gases or on hydrogen. [0002] A problem with gases as an energy storage in vehicles is the greater storage volume required as compared to liquid energy sources, which, for natural gas, is greater by three orders of magnitude under ambient conditions. For this reason, it has been regulated that natural gas is available at gas stations at a pressure of 250 bar so that, as defined by technical rules, a pressure of 200 bar is reached and not exceeded in the pressure gas container of a vehicle at a reference temperature of 15.degree. C. Thus, compared to a fuel-operated vehicle, at least only three times the storage volume has to be made available in a car. [0003] In gas fueling installations, the pressurizing work to be performed causes a heating of the gas in the pressure gas container. The Joule-Thomson effect (a change in the gas temperature by throttling) of the real gas generally counter-acts this heating. However, it is only under very favorable conditions, i.e. at sufficiently low temperatures, that the Joule-Thomson effect and the heat dissipation to the environment suffice to compensate for the heating caused by the pressurizing work of the gas. In gas fueling installations without a cooling device, if these favorable conditions do not exist, the pressure gas container will be filled short upon decanting. This is due to the fact that the pressurizing work creates a high temperature and thus a corresponding high pressure in the pressure gas container, whereby the available pressure difference for filling is reduced to such an extent that the fueling operation takes a long time and is therefore terminated before the pressure gas container holds the volume of gas possible according to technical specifications. [0004] DE 197 05 601 A1 describes a natural gas fueling method without cooling of the gas, wherein the fueling of the pressure gas container is continued until the pressure in the conduit to the pressure gas container exceeds a maximum pressure. Another possibility provides that the fueling operation is terminated as soon as the mass flow falls below a limit value. [0005] WO 97/06385 A1 describes a gas charging system for high-pressure gas bottles. Here, the gas is cooled by flushing the high-pressure gas bottle to be filled, whereby two connections for the feed and the return flow are needed. In the flushing circuit, the gas is cooled via a heat exchanger or by mixing it with gas in a reservoir. [0006] EP 0 653 585 A1 describes a system for fueling a pressure gas container. Here, a test pulse is performed, which is evaluated with reference to the thermal equation of state for the real gas. Further, a switching to reservoirs at higher pressures (multiple unit method) during the fueling is described. The fueling operation is performed intermittently. No cooling device is provided for the gas. [0007] DE 102 18 678 A1 describes a method and a device, wherein the gas for filling the pressure gas container is fed from a high-pressure reservoir through a vortex tube acting as a cooling device. The vortex tube takes advantage of the differential pressure prevailing in the fueling system to separate the gas flow into a hot gas flow and a cold gas flow. The latter is then supplied to the pressure gas container. The functionality of this method is based on the fact that the gas is fed to a swirl generator at a supercritical pressure ratio, the generator being arranged axially between two pipes having different inlet diameters. A decrease in temperature through the use of a vortex tube can be achieved if, and only if, supercritical pressure ratios exist. At a critical pressure ratio for natural gas of .pi.*=0.5427 and a pressure in the reservoir of p.sub.v=250 bar, which is generally not reached, when a plurality of vehicles are refueled in shirt succession, a subcritical condition is obtained when the pressure in the pressure gas container has risen to p.sub.o=135 bar. This means that, when filling a pressure gas container with natural gas in a pressure range from p.sub.o=135 bar to p.sub.o=200 bar, the use of a vortex tube will result in no further decrease in the gas temperature under the preconditions defined by the technical specifications. [0008] A direct fueling is feasible where setting up publicly accessible natural gas fueling stations is not economic. Vehicles--and not only those of individual transport--could be refueled where they are during their standstill times. This may be in industrial parks, garages or car boards. Many households or buildings have natural gas available for heating. A compressor (natural gas compressor) could compress this natural gas at night from the regular natural gas network level of 50 mbar to 200 bar at a reference temperature of 15.degree. C. A vehicle could be fueled therewith. [0009] Another possible field of application for such a fueling system is seen in agriculture, where large volumes of biological gas are produced. Instead of feeding this biological gas into a public gas network, it could be compressed in situ and be used to operate agricultural vehicles and machines. In the future, this would allow to replace biodiesel in agriculture. [0010] One requirement to be fulfilled by this compressor is that the compressor has to be configured such that a complete filling with fuel has to be possible within one night (about 8 hours) at 200 bar and a reference temperature of 15.degree. C. The major problems of a multistage high-pressure compressor are the intermediate cooling and the cooling of the gas at the compressor outlet, which, when entering the pressure gas container, must not exceed 60.degree. C. at any time during fueling. [0011] It is an object of the invention to provide a device for generating highly compressed gas, wherein the compressed gas, which heats up during compression, is cooled in a cooling device which is of simple structure, provides a high cooling performance and is adapted to be realized with small dimensions. [0012] The device of the present invention is defined in claim 1. According to the invention, the cooling device arranged downstream of the compressor stage is designed as a vortex tube. [0013] Vortex tubes are particularly well suited for ultra-short time decreases in temperature. In contrast to conventional gas coolers, these decreases in temperature can be achieved over very short path lengths. Moreover, the invention is based on the insight that the pressure ratio in the compressor stages of the high-pressure compressor is larger than 3. Thereby, it is guaranteed that the vortex tubes in all compressor stages will be in the supercritical range, which is essential for a trouble-free operation of the vortex tubes. [0014] A particular embodiment of the invention provides to maintain, in direct fueling, the reference temperature of 15.degree. C. at a pressure of 200 bar in the pressure gas container to be filled even if the decrease of the gas temperature in the vortex tubes is longer sufficient for this purpose under unfavorable peripheral and environmental conditions. Suitably, after the last compressor stage with an adjoining throttle point, the gas is not introduced into the pressure gas container to be filled, but is returned to the compressor inlet after an adiabatic throttling (Joule-Thomson effect). In the closed gas circuit, the gas temperature decreases continuously under isotropic compression and adiabatic throttling (production of cold by adiabatic throttling, caused by the Joule-Thomson effect in real gases). According to the invention, the gas circuit will remain closed until the decrease in temperature required by the technical specifications for the filling of the pressure gas container is reached. [0015] A particularly suitable embodiment of the invention provides for using the heat produced in the vortex tubes to heat water for domestic use or to use it for heating a building. [0016] Suitably, the output pressure of a multistage compressor is set so high that this pressure is above the critical pressure of the pressure gas container to be filled. In contrast to the filling of a pressure gas container by an overflow from a reservoir in which the gas pressure is limited to 250 bar according to the technical specifications for natural gas, these regulations do not apply to direct fueling using a high-pressure compressor, provided that the legal provisions for the pressure gas container are observed. [0017] In a preferred embodiment of the invention, throttling via an expansion unit takes the gas flow leaving the final stage of the high-pressure compressor to the pressure allowed in the pressure container. The mechanical work arising at the expansion unit is used to drive a compressor for pre-compressing the gas taken from the gas network. [0018] Using the pre-compression, the output pressure at the compressor can be varied via the input pressure at the high-pressure compressor. By throttling a defined output pressure, the ambient conditions during the fueling can be taken into account and the gas temperature in the pressure gas container can be influenced indirectly. [0019] The invention further refers to a device for decreasing the temperature of a gas from a reservoir containing pressurized gas, comprising a feed pipe leading to a swirl generator, a filling pipe leading to the pressure gas container, and a vortex tube branching from the swirl generator for conducting a rotating vortex flow. [0020] At higher temperatures, the volume of a gas is larger. Thus, for reasons of space, it is often necessary to cool the gas since then a larger gas mass can be stored in a determined volume. A typical application for gas cooling are gas fueling operations. [0021] For a fast fueling of a gas-fueled vehicle, a fueling installation is required that is adapted to perform a fast decantation of high-pressure gas from a reservoir to a pressure gas container. Such gases to be decanted may comprise natural gas or methane or similar gases, as well as gases such as nitrogen, oxygen, argon, air or hydrogen. [0022] In gas fueling operations it is intended to fill such a mass of gas into the pressure gas container, independent of the ambient temperature, that a limit value of pressure defined by the technical specifications is possibly reached in the pressure gas container at a predetermined reference temperature. For example, technical specifications provide that a pressure of 200 bar at a reference temperature of 15.degree. C. must not be exceeded in a pressure gas container. For a fast fueling operation by overflow, the reservoir must be under high pressure for the required mass of gas to be transferred into the pressure gas container. [0023] In gas fueling installations, the pressurizing work to be performed causes a heating o the gas in the pressure gas container. The Joule-Thomson effect (change in temperature of the gas by throttling) of the real gas generally counteracts this heating. However, it is only under very favorable conditions, i.e. at sufficiently low temperatures, that the Joule-Thomson effect and the heat dissipation to the environment will suffice to compensate the heat caused by the pressurizing work of the gas. If these favorable conditions do not exist, a fast decanting in gas fueling installations without cooling device will result in a short-filling of the pressure gas container. This is due to the fact that a high temperature and a corresponding high pressure are caused in the pressure gas container by the pressurizing work, whereby the pressure difference available for fueling is lowered to such a degree that the fueling operation takes a long time and is therefore terminated before the pressure gas container holds the mass of gas possible according to the technical specifications. [0024] It is another object of the invention to provide a device for lowering the temperature of a gas, which can be manufactured with small dimensions, is of a simple structure and has a short response time with a great cooling effect. Continue reading... Full patent description for Device for generating highly compressed gas Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Device for generating highly compressed gas patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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