DE2923561A1 - Medium-pressure methane tanks for motor vehicles - contg. solid for adsorbing or forming adduct with methane - Google Patents

Abstract

Methane tanks contain a solid packing material (I) capable of adsorbing or forming an adduct with CH4 and have a design pressure of up to 15 bar. (I) must be capable of increasing the CH4 capacity by a factor of at least 10 (measured at 10 bar and room temp.) compared with the empty tank. (I) can be (a) an opt. modified zeolite, esp. a CaX or CaY zeolite, (b) a silica gel, pref. with an alkanised or otherwise dipole-modified surface, or (c) a material with a layer lattice structure capable of forming intercalation cpds., e.g. produced by incorporating alkali metal atoms into graphite. The tanks are capable of storing useful amts. of CH4 at moderate pressures without being excessively heavy, e.g. a 7-litre tank at 10 bar can store as much energy as a 1-litre gasoline tank.

Description

Nuclear research facility July eh.
Company with limited liability

Methane pressure tanks for automobiles

The invention "relates to a methane pressure vessel for motor vehicles with a! Ellung from a methane adsorbing "or accumulating pesticide.

It is "known that methane is used as a fuel for gasoline engines in a similar way as hydrogen is suitable and is characterized by high knock resistance and favorable composition of the exhaust gases from higher hydrocarbons (see for example "Hut", Volume I, Verlag Wilhelm Ernst, Berlin 1941).

A wider use of propellant gases than fuels for motor vehicle traffic, however, the opposite stands for liquid Fuels much more difficult storage in general and especially the problematic storage in the motor vehicle contrary, since considerable amounts of gas in a small space only by means of high pressures and / or low temperatures can be saved.

For the hydrogen, this problem was solved by introducing hydride formers into the storage container

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Take up hydrogen with mutual formation (and so that a possible compression of the same result), but if necessary release it again when heat is supplied. FeTi masses, for example, have been considered as suitable hydride formers for this purpose. Analog hates that compression of methane through compound formation are unfortunately unknown. Explained from this that so far no more detailed study programs seem to exist for the development of methane-powered vehicles.

Although a few years ago (in DE-OS 2302 403) a concept was also designed with regard to internal combustion engines Method for saving vci sasen, among other things CH., Described in storage containers, after which an adsorbent for the gas is introduced into the container which can then be saved at lower pressures. The increase given as an example for methane the amount of storage by $ 78 at pressures of 70 kg / cm (which is increased to improve methane compression should be) but makes this procedure appear so unattractive that it is not surprising that this method has obviously not been taken into account so far, since the degree of compression achieved is only moderate and, above all, the pressure range considered for storage is still far above that, what is believed to be portable for general daily use.

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ORIGINAL INSPECTED

A methane storage tank for motor vehicles that was interesting for practical use was thus - also starting from from the teaching of DE-OS 2 302 403 - not yet known.

The invention is therefore based on the object of the applicability of methane by developing a storage container to improve for methane, with the sensible exploitable quantities of methane at moderate pressures with technically portable effort and without excessive weight.

It has been found that significantly higher degrees of methane compression are achieved with solids quenching at pressures that appear portable for practical use.

The methane pressure vessel according to the invention is therefore characterized by a solid filling, which is one (S ^ Ven3Lciitungν (bd ~ 10bar) compared to the empty tank of at least about 10 at room temperature and by a pressure design of the container for up to about 15 bar.

Methane densities ν of at least about 10 can be achieved with materials whose lattice structures have a have considerable absorption capacity for the methane molecules. Materials that depend on the lattice geometry are therefore suitable allow penetration of the methane molecule to the inner receiving areas and, in addition, surface forces in particular develop that an increased fixation or deposition of methane molecules on the achievable Surfaces.

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ORIGINAL INSPECTED

The cage-like lattice structures known as zeolites with the general composition AIpO-,. xSiOp. (M, Ka, K, Ca, Ba) O nri ± x = 2-7, in particular <3 _t are with regard to the costs, the specific Weight and storage capacity "preferred storage materials, with zeolites of structure type X (faujasite type) or type A being particularly suitable, as described, for example, by DWBreck in" Zeolit.e Molecular Sieves ", J. Wiley, New York (1974) Pages 29 to 133 and 593 to 725 are identified in more detail.

Known data on methane uptake by Ca-exchanged zeolites of the faujasite type indicate the particular usefulness of such materials. This view is supported by our own measurements on commercially available molecular sieves, which at a bulk density of about 1 g / cm showed a compression factor of 5 »1 at 10 bar and room temperature, so that with improved space filling by beads of different sizes, compression factors appear to be achievable purely arithmetically be in the region of 10. The examined material had cage openings of 5% and a chemical composition corresponding to CaO.Al ₂ O ₅

Materials that allow methane enrichment within the lattice are also supported by such layer lattices formed, the layer spacing is geometrically adapted to the storage of methane. Get into embossing So, for example, expanded graphite lattices, such as those created by the incorporation of alkali (especially sodium) into the Graphite lattice can be obtained and as intercalate compounds are known. Others geometrically adapted

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Layer grids are made, for example, by a 1,4-diazabicyclo- 2.2J-octane montmorillonite system formed, about that of J. Shabtai and others. on the 6th International Congress on Catalysis in London (July 12-16, 1976) (see "Proceedings of the Sixth International Congress on Catalysis "Volume 2, page 660 ff.).

the methane enrichment in storage masses are also recommended silica gels, especially those whose Surface is chemically modified in such a way that an adhesion tendency of the methane is achieved. As an endorser of liability Forces, dipole forces in particular come into consideration, so that silica gels are preferred whose surfaces are modified with regard to a corresponding dipole effect. Preferred materials include also silica gels with an alkanated surface, such as are commercially available.

With a compression of at least about 10 at room temperature and 10 bar methane pressure, usable methane fillings can be made can be achieved with portable tank weights under conditions such as those for propane and butane bottles are known which are filled with 10 bar overpressure.

An essential criterion of the solid according to the invention -! Filling consists in the fact that a reversible methane compression by surface effects of a general kind is achieved, so that the stored methane is released again spontaneously when the pressure drops, which

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in addition, the solid-off filling is heated of the tank can be substantially promoted. Appropriately one will use the cooling fluid coming from the engine for the tank heating, the one with decreasing • Increased tank pressure can be used to heat the tank.

For this purpose, pressure and temperature sensors can be provided in the tank, as well as microprocessors that the Control the heating agent supply to the tank depending on the determined pressure and temperature values.

A division of the fuel tatikr · «? in separate sub-containers that can be filled and emptied independently of each other, so that each a sub-container with sufficient pressure for spontaneous delivery is available even without heating.

About the storage space available within the tank As already indicated, it can be advantageous to use a pesticide filling to be provided, which consists of a mixture of pearls with matching diameters.

The dimensions of a fuel tank according to the invention can be estimated as follows: a Fm (ITTP) CH. provides usable energy that 1 kg of gasoline (1.43 Petrol). A 1 liter petrol tank would therefore be designed for 10 bar and a compression factor of 10 Methane tank of 7 1 correspond. This value appears to be quite considerable. However, there is still considerable

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Possibilities for improvement regarding the storage areas exist, a further approximation of the volumes to one another seems to be within the realm of the possible lie.

The accompanying drawing shows a scheme for a methane storage tank 1 built into a motor vehicle Sub-container 2, to which from the engine 3 heated Ilotor coolant can be sent controlled, the is then returned to the cooler 4. 5 means a gas buffer with a pressure sensor 6. Others Pressure sensors 6 are located on the carburetor 7 to measure the flow rate. The heated engine coolant is passed through Pumps 8 conveyed through the methane storage branch, in which solenoid valves 9 and temperature sensors 10 are provided are.

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Claims (6)

Nuclear Research Facility Julien
Company with limited liability Claims (1 .j Methane pressure vessel for vehicles with a
Filling made of a solid that adsorbs or attaches to methane, characterized by a solid filling!
allows a methane compression ν (at * v10 bar) compared to the empty tank of at least about 10 at room temperature and by designing the pressure of the container for up to about 15 bar. 2. Pressure vessel according to claim 1, characterized in that the solid filling by optionally modified, preferably Ca-ion-exchanged Zeolites, especially zeolites of structure type X (faujasite) or A, is formed. 3. Pressure vessel according to claim 1, characterized in that the solid filling
by silica gels, especially on their surface
alkanated or with a view to a dipole effect 030051/0213 chemically modified silica gels, is formed. 4. Pressure vessel according to one of the preceding claims, characterized in that the pesticide filling by expanded layer structures, in particular by means of the incorporation of alkali atoms into the graphite layer lattice Intercalate compounds, is formed. 5. Pressure vessel according to one of the preceding claims, characterized by a Plastic filling made from pearls with different sizes Diameters for extensive space filling. 6. Pressure vessel according to one of the preceding claims, characterized by a Division into sub-containers provided with separate supply lines with respective heating, in particular indirect heating by means of cooling fluid from the engine, which depends on the temperature and pressure in the sub-tank is supplied via processor-controlled valves. - 3 030051/0213