WO1991007620A1 - Device for expelling substances from pressurised containers - Google Patents

Abstract

Device for expelling a substance (2) from a pressurised container (1) through a valve aperture (8) using hydrogen (4) as the propellant which produces an overpressure in the pressurised container and is preferably released at its ambient temperature and/or by the application of extra heat at constant partial pressure from a hydride storage material (6) in which it is stored when pressure is relieved by the freeing of the exit aperture. The hydride storage material is preferably a metal hydride held in a hydride container (7) integrated into or connected to the pressurised container which is connected to the inside of the pressurised container (4) via a valve which closes at increased pressure and is so arranged that it also withstands high pressures. This provides a device with an environmentally acceptable propellant gas which, owing to the facility for opening the hydrogen store, can be safely handled and, moreover, is re-usable by recharging with hydrogen.

Description

Austreibun ^cr multiplexing frame generating apparatus for substances from pressurized containers The invention relates to devices for expelling Sub¬ punch from pressurized containers and proceeds from a device having the features in the preamble of claim 1.

A wide variety of atomizing devices are used both for industrial and commercial purposes and for private use. The conventional mechanically operated systems have the advantage of working without propellant, but they have the disadvantage that only short pressure surges are possible, the spray pressure is also low and cannot be kept constant. As a result, the reproducibility of the aerosol quality is influenced, which is why this purely mechanical solution is usually only found in spray cans or bottles for private use.

The expulsion of liquids with the aid of propellant gases under pressure from a container has the advantage that a constant and sufficient spray pressure is achieved as a result of the constant partial pressure of the propellant at a predetermined temperature, but the propellant gases used to date are environmentally harmful. Attempts are being made to replace the still frequently used fluorocarbons (CFCs), which are considered to be the cause of the damage to the ozone layer, and increasingly less harmful partially halogenated chlorofluorocarbons (HCFCs 22) are being used. This can reduce the damage to the ozone layer, but it cannot be completely ruled out. This is all the more the case because the customary propellant gases are designed so that they exist in two phases, liquid and gaseous, under the given operating conditions. As a result, the liquid phase of the propellant forms a solution with the substances to be atomized, so that a large part of the propellant is expelled during atomization.

Harmful blowing agents that escape to the outside are avoided in an atomization system (US Pat. No. 4,513,884). There it is proposed to contain a liquid to be atomized in a tendency and tightly closable container to insert an initially gas-empty plastic bag so that the container can be transported without being under pressure or can also be filled later. The plastic bag contains a predetermined number of sealed bags which are filled with soda. Furthermore, a bag filled with citric acid is provided, which is opened manually to the inside of the bag before the container is closed. The acid solution then reacts with the soda from the nearest pocket, which must be designed so that it bursts at the same time as the acid solution pocket is opened. The resulting carbon dioxide inflates the pocket so that liquid can be expelled when the closed container is relieved of pressure. When the liquid level is reduced, the remaining pockets burst successively when the bag is inflated further. In order to prevent liquid from being trapped under the inflated pocket, a siphon tube is also accommodated in the container.

Although this system ensures a more or less continuous extension depending on the number of pockets, it has a considerable number of disadvantages.

As can be seen from EP-PA0171556, which deals with the production of functional bags for this application, this production is first of all complex and not uncritical. The sealing points of the bags must be designed so that on the one hand it is ensured that the bags burst at the desired time, but on the other hand the bag is not destroyed in the process. In this case, the substance to be atomized and thus also the atomized substance would mix dangerously with the acid and the carbon dioxide. In addition, the generation of carbon dioxide causes disposal problems even if the bag is intact, since the entire bag must be disposed of and cannot be reused.

Furthermore, the system is also not user-friendly, because the pressure vessel must be opened by destroying the acid pocket to initiate gas generation. The entire container is therefore relatively complex and is in principle only suitable for applications in which any refilling is desired.

The invention is based on the object, starting from the features in the preamble of patent claim 1, of specifying a device for expelling an atomizable substance from a pressure container, which on the one hand ensures a constant and sufficiently high propellant gas pressure during the entire period of use and on the other hand the mentioned avoids harmful blowing agents and also chemical substances.

This object is achieved by the subject matter of patent claim 1. According to the invention, the known, mostly liquefied, propellant gases are replaced by hydrogen, which is stored in a hydride material and is released therefrom when energy is supplied, preferably in the form of ambient heat. The released hydrogen is used as a blowing agent for expelling atomizable substances, liquids, paste-like substances, such as sealants, for example in the form of silicone or also, for example, pulverized substances, from a container in which the released hydrogen has an overpressure (under normal conditions over 1 bar). The overpressure generated is constant at a given temperature, because the hydrogen stored in a hydride generates a certain constant partial pressure over a wide hydrogenation range at constant temperature. If the atomizing opening of the pressure vessel is opened and thus a pressure relief occurs in the pressure vessel, it continues to escape. long hydrogen from the hydride material and expels the substance until the opening is closed again and the equilibrium partial pressure of the hydrogen is present in the hydride material. This ensures continuous and complete emptying with sufficient spray pressure. Propellants (noble gases, air), which cannot be liquefied under the given operating conditions, cannot do this and are therefore unsuitable as propellants.

In contrast to the chemical design of the type mentioned above, in which gas must be generated by the successive triggering of chemical reactions, the solution according to the invention accordingly contains a real gas store with the described advantages of the continuous generation of an environmentally friendly gas. It is also advantageous that the released hydrogen, in contrast to the chemically produced gases or the propellant gases mentioned at the outset, e.g. can be easily stored again by cooling the pressure vessel.

In principle, all types of hydrides are suitable which, at the temperature of the respective environment in which the substance container is to be used, have the property of releasing the stored hydrogen again. In particular in cold environments, it is also possible to trigger or intensify this process by supplying heat, for example by means of the hand warmth of the user of the device.

Regardless of whether the hydride material is mixed with the substance to be atomized in the pressure vessel, for example in the form of so-called pellets, or is received in a storage vessel and the interior of the pressure vessel is pressurized by the hydrogen released, there is the advantage according to the invention that the hydrogen as blowing agent is not harmful to the ozone layer, since it is a natural component of the earth's atmosphere with an average of 0.03 g Hydrogen per ton of air, whereby it only occurs in traces in the lower atmospheric layers and forms the main component in the upper layers.

The possibility of mixing with the substance to be atomized, which is fundamentally not possible with the chemical system mentioned, lends itself to organic hydrides which always generate the same partial pressure at certain temperatures. In addition, metal hydrides are particularly suitable for the purpose according to the invention, the hydrogen storage properties of which are already used in the development of hydrogen stores for H ₂ -driven motor vehicles. The alloys previously proposed for this purpose or for example for fuel cells (titanium-iron, titanium-manganese, nickel mixed metal, calcium-nickel or, for example, alloys with vanadium) have a high storage capacity for hydrogen and work in a wide temperature range. and pressure range. The hydrogen is stored in high concentrations in a small volume and released under constant pressure until it is discharged.

The hydrogen uptake is largely reversible, ie the hydrogen is released again by reducing the pressure at a given temperature or increasing the temperature at a given pressure. The equilibrium partial pressure of the hydrogen stored in a metal hydride is consequently dependent on the temperature of the metal hydride. At room temperature (20 to 25 ^β C), some known metal hydrides, for example titanium-iron alloys, have hydrogen partial pressures of 3 to 5 bar and are therefore well suited as hydrogen stores for atomizing devices.

The powdered metal hydrides or, if appropriate, also non-metal-like hydrides are preferably received in a hybrid container which is optionally integrated into the pressure container, ie the spray can or bottle, or is connected to the outside thereof. In contrast to the previously used propellants the ability to isolate the propellant and the propellant storage from the container, which increases safety. For this purpose, the pressure coupling of the two containers via a valve is recommended, which closes in the event of sudden heating and associated pressure rise in the hydride storage container and thus prevents the pressure in the pressure container from increasing further and destroying it. The hydride container, which only needs a few cm ³ capacity, can easily be designed so stable that it can withstand considerable pressure increases and pressures that are far above the spray pressure or expulsion pressure, thus ensuring a safe containment of the hydrogen.

In contrast to the systems with conventional propellants, which only guarantee safe handling up to relatively low temperatures, the invention thus enables not only an environmentally friendly but also a safe device by using the hydrogen storage device, which can be easily separated from the overpressure container.

Hydrogen storage with metal hydride material accommodated in the pressure vessel are known per se in a wide variety of designs from numerous publications (for example DE-OS 35 02 311, US-PS 35 16 263, US-PS 41 33 426 and DE-OS 32 23 777) . However, these only deal with creating storage with the highest possible capacity, which e.g. can have different filling densities and provide sufficient space for expansion during reloading. Although such storage containers have been known for over twenty years, no consideration has so far been given to utilizing properties other than the hydrogen-storing and releasing effect.

If the hydrogen is not to come into contact with the expelling substance, an indirect pressurization can also be carried out with the help of a double container, as is shown in FIG Principle has also been proposed for previous blowing agents. The substance to be atomized is accommodated in a compressible bag-like or bellows-like container, which is located in the actual pressure container. According to the invention, this is preferably subjected to hydrogen pressure via a valve, so that when the spray nozzle is opened, the spray substance is expelled by compressing the container. This solution is particularly recommended for substances in which hydrogen dissolves easily and would thus be driven out to a greater extent.

In contrast, water-based liquids have the advantage that the solubility of the hydrogen in them is minimal and is about 2% by volume. In contrast to the previous propellant gases, there is the advantage with such spray substances that only extremely small amounts of hydrogen are expelled. These quantities are also below the ignition limit of the hydrogen so that it cannot be ignited in the spray jet.

When storing larger quantities of used or unused devices according to the invention, it may be advantageous, for safety reasons, to coat the entire container with a catalyst material in the form of a net or a coating, so that, for example, weak points (seams, etc.) unintentionally escaping hydrogen recombines with oxygen present in the air. In this way, an ignition hazard can be avoided even with increased hydrogen leakage. It is also possible, after the pressure vessels have been emptied, to trigger a targeted release of hydrogen with the catalytic recombination via a controlled leak, which only forms or is generated in the vessel or in the valve after the emptying. Thus, the remaining hydrogen can independently catalytically recombine with atmospheric oxygen into water by controlled diffusion from the hydride container and the pressure container. In the case of substances in which hydrogen is dissolved to an increasing extent and thus also expelled, the spray system can also be designed such that the hydrogen already recombines before it emerges. This can be achieved if air and thus atmospheric oxygen is sucked in between the outlet valve and the outlet nozzle through an additional opening during spraying due to the so-called water jet pump effect. A catalytic network or a corresponding coating in this space between the outlet valve and nozzle then in turn automatically triggers a catalytic recombination so that the escape of the hydrogen is prevented.

If the device according to the invention is exposed to extreme temperature fluctuations and very high pressures occur as a result of high temperatures in the hydride container, a relief valve can be provided in the hydride container for self-regulating pressure limitation in addition to the valve towards the pressure container. The integration of a catalyst in this valve is also recommended here. It is thus possible, even under extreme conditions, to compensate for the hazard potential which is caused by the ignitability of the hydrogen. In contrast to the previous propellant gas bottles, there is the possibility of eliminating the risk of explosion by regulating the pressure because the propellant is released from a store which can be encapsulated by the actual pressure vessel.

An additional advantage with regard to environmental protection is the rechargeability of the hydride storage. Thus, in particular when the hydride reservoir is connected to the pressure vessel in the form of an independent unit, the hydride material can be loaded with hydrogen again without problems and the unit can thus be reused. However, reloading is also necessary with the hydride storage integrated in the pressure container. rather possible via the opening or valve opening of the hydride container before the spray bottle or the pressure container is refilled with the substance to be atomized.

According to the invention, the already known container shapes, spray valves, nozzles and their removal and actuation devices can be used as pressure containers and spray systems. The hydride container, which is very small with a few cm ³ in comparison to known containers of hydrogen storage for motor vehicles, can already be designed as a pressure vessel with a few mm wall thickness with a high safety distance without the entire device becoming unwieldy. If the hydride material is mixed directly with the substance in the pressure vessel, it is recommended, as in the case of the existing spray bottles, to specify a maximum permissible ambient temperature.

Metal hydrides, which are in finely divided form in powder form or in the form of a matrix of several metals and are suitable for the device according to the invention, are already commercially available and their properties are precisely known. In addition, an abundance of hydrides not yet offered and tested as hydrogen storage is conceivable as a hydrogen fuel gas dispenser.

Even if a secured hydride storage container is used, the additional costs are also low in terms of recyclability. When the hydrides are mixed with the substance to be driven out, there are practically no additional costs compared to the direct use of blowing agents without a storage medium.

The invention is explained in more detail below on the basis of an exemplary embodiment which is illustrated in the figure.

In the exemplary embodiment, a device for expelling an atomizable substance is shown which is integrated in a pressure container in the form of a spray can 1. The spray substance 2, a liquid or, for example, a powdered material, is removed with the aid of a riser pipe 3 which extends through the bottle-shaped spray can to a little above the bottom thereof. Above the spray substance level there is a gas space 4 in which hydrogen as the propellant gas is at a pressure of a few bar, ie a few 10 ⁵ Pascals. The pressure corresponds to the hydrogen partial pressure of the hydride material reservoir 6 at the present ambient temperature, to which the gas space 4 is connected via a hydrogen outlet valve 5. The valve is designed so that penetration of the spray substance into the hydride material container 7 is prevented, ie if the spray can is tilted or turned over, the valve closes automatically. Solutions that can be used are a sintered metal in the valve which only allows the hydrogen, but not the spray substance, to pass through, or a simple sealing ball. The valve is otherwise only closed when the hydrogen pressure in the reservoir 6 rises sharply as a result of a sharp rise in temperature and exceeds a maximum permissible pressure for the spray can. The hydride reservoir 6 is in the form of a powdered metal hydride in a hydride container 7, which is the short one. Neck of the bottle-shaped can 1 forms. The riser pipe is guided through the hydride tank 7. A spray opening (nozzle), not shown, is opened by means of a spray valve indicated at 8. For example, as with most spray systems, a simple mechanism that is pressed down with a finger can be used to actuate the spray valve.

The hydride container 7 is preferably made of metal with a thickness of 2 to 3 mm and has a volume of about 3 cm ³ . With this storage size, so much hydrogen is stored in the hydride reservoir 6 that, even with an empty can of a few 100 cm ³ capacity, the equilibrium partial pressure is reached at the intended operating temperature and there is therefore a sufficient spray pressure. When the device is operating, the spray valve 8 is opened. As a result of the resulting pressure relief in the gas space 4 via the riser pipe 3, hydrogen is continuously released from the hydride container and expels the spray substance continuously. Only when the spray valve 8 is closed will no more hydrogen escape when the equilibrium partial pressure is reached. When the temperature of the environment rises sharply, the valve 5 closes automatically when a predetermined pressure value is reached, so that the can 1 is not exposed to an increased hydrogen pressure as a result of an increased partial pressure. If necessary, an additional pressure relief valve can also be provided in the hydride container 7 in order to take even the most extreme temperatures into account.

In addition, the can 1 and the hydride container 7 can be covered or coated with a catalyst material or network in order to bring about a catalytic recombination of unintentionally escaping hydrogen with atmospheric oxygen to water.

The exemplary embodiment is not the simplest solution which does not require a hydride container and a hydrogen outlet valve and which mixes the hydride hydrogen storage material with the spray substance, e.g. in the form of pellets in the spray can. Compared to the known spray devices, this solution does not require any changes to the pressure vessel.

Even when using a hydride reservoir, a separate container and the hydrogen outlet valve are not absolutely necessary, but increase the safety of the device.

Since the hydride storage container is only relatively small, it can just as easily be connected to the spray can in the form of an independent unit. A hydrogen outlet valve is also recommended here. Between the spray valve and the spray opening, a suction opening for air can additionally be formed, which is sucked in during spraying and whose atmospheric oxygen, in the presence of a coating with catalyst material, brings about the recombination of the hydrogen with water before it emerges.

In the exemplary embodiment, a spray can was explained, from which an atomizable substance is expelled. However, with the device according to the invention e.g. also drive out any paste-like, non-atomizable substance.

Claims

Claims 1. Device for expelling a substance through the released opening of a pressure vessel for this substance with the aid of a propellant which generates a pressure in the pressure vessel that is higher than the environment of the vessel, characterized in that the device comprises a hydride material (6) in which hydrogen is stored, which is preferably released at the ambient temperature of the container (1) and / or by supplying further thermal energy from the hydride material as the blowing agent. 2. Device according to claim 1, characterized in that the hydride material (6) of the device is in the form of a hydride reservoir which consists of a hydride container (7) integrated in the pressure vessel (1) or arranged outside the pressure vessel, in which the Hybrid material (6) is received and the pressure is coupled to the pressure vessel interior (4). 3. Apparatus according to claim 1, characterized in that the hydride material is admixed with the substance to be expelled. 4. The device according to claim 2, characterized in that the hydride material is a metal hydride which is stored in powder form in the hydride tank (7). 5. The device according to claim 2, characterized in that the hydride container (7) and the pressure container (1) are connected to one another via a valve (5) which closes when the pressure in the hydride container increases as a result of strong heating. 6. The device according to claim 2, characterized in that the released hydrogen flows into the pressure vessel in which a compressible container with the substance contained therein is arranged, on which the increased pressure generated by the hydrogen has a compressive effect. 7. Device according to one of the preceding claims, characterized in that the hydride container and the pressure vessel are coated with a catalyst material for the catalytic recombination of escaping hydrogen with atmospheric oxygen to water. 8. The device according to claim 2, characterized in that the hydride container is preferably loaded with hydrogen again after emptying the pressure container through an opening through which it communicates with the interior of the pressure container. 9. Device according to one of the preceding claims, characterized in that a suction opening for air and a catalyst material are provided between a known outlet valve (8) and the outlet opening for the substance to be expelled, air being sucked in through this suction opening with the oxygen thereof the expelled hydrogen recombines catalytically to water before passing through the outlet opening. 10. Device according to one of claims 5 to 9, characterized in that the valve (5) is designed such that it prevents an inflow of the substance to be expelled into the hydride container (7) when the pressure container (1) is tilted.