Patent Application
20060260327
This invention relates generally to the field of gas liquefaction systems.
Cryogenics (technology that uses very low temperatures) is already popular in applications such as high-end medical equipment, scientific research, food processing and semiconductor industries. Our research indicates enormous potential for a broader application of this technology in various new marketplaces and industries. Liquid gas, such as liquid nitrogen, has application in all of the above.
One limitation in adapting cryogenic technology concerns the current supply system of liquid nitrogen. It is generally available from Industrial Gas Suppliers, only for customers who purchase large amounts and live in urban areas. Generally, the supply of liquid nitrogen suffers from a host of drawbacks. Liquid nitrogen is produced at an industrial site and can be delivered to a purchaser, generally within two days on placing an order (provided a sufficiently large quantity is ordered, e.g. 100 litres). Once the liquid nitrogen has been delivered, it must be stored. The longer it is stored, (and the further the delivery site is from the industrial site) the more LN2 is lost through boil off. Storage of large amounts of LN2 presents a hazard and may require transfer to smaller containers for handling.
All of the above points to the need for a means of liquid gas supply that is readily available on site, and doesn't suffer from the drawbacks associated with transfer and storage of large quantities of liquid gas.
Thus there is a potential new market in delivering On Site Liquefaction Systems, which allow anyone to access Liquid nitrogen easily, anywhere, at reasonable cost. Effective use of the technologies available allows us to develop unique liquefaction systems. Combining technology with marketing, we promote our cryogenic solution to international markets.
Liquid nitrogen has application in many areas including: medical and veterinary treatment; research and laboratory applications; education; machinery shops; and, obviously, refrigeration.
A small-scale gas liquefaction system is provided that can be used in, for example, medical office, restaurant and bar, and machine shop settings. The liquefaction system requires little or no special set up and can be simply plugged into a standard (single-phase 115 VAC) wall outlet. Depending on the specific embodiment, it will produce 1-20 liters of liquefied gas per day. It provides an economical option for users of relatively small quantities of, for example, liquid nitrogen to obtain liquefied gas.
The gas liquefaction system will liquefy 1-20 liters per day of air, nitrogen, oxygen, argon or natural gas.
The invention comprises a gas generator, a cooling unit having a stirling, pulse-tube or stirling-pulse-tube cooler, and an insulated container below said cooling unit to receive the liquefied gas. The aforesaid components are sized and configured to allow the liquefaction system to be located on a counter top. Although in the preferred embodiment the invention is used to produce liquid nitrogen from air, alternate embodiments may be used to produce liquid oxygen, natural gas, argon or air.
The gas generator and cooling unit together occupy an envelope no larger than 675 mm width, 400 mm depth and 778.1 mm height. The cooling unit itself has maximum dimensions of approximately 152 mm width, 290 mm depth and 369 mm height.
The liquefied gas falls from the cooling unit directly into an insulated container or dewar, which is connected to the cooling unit with a gas-tight seal. The insulated container can be quickly and easily disengaged from the cooling unit, thereby eliminating the need to transfer the liquefied gas to portable containers. The risks associated with handling the liquefied gases are thereby minimized.
The invention itself both as to organization and method of operation, as well as additional objects and advantages thereof, will become readily apparent from the following detailed description when read in connection with the accompanying drawings, wherein:
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In the preferred embodiment the gas generator 20 is a nitrogen gas generator that separates nitrogen gas from the air. Suitable gas generators are available from Compressed Gas Technologies Inc. (Windsor, ON, Canada) and System Instruments Co., Ltd. (Tokyo, Japan). In the various alternate embodiments the gas generator will generally have to filter the air to remove dust, etc., and include means for removing water vapour from the gas before it is cooled. In alternate embodiments the gas generator 20 may provide oxygen gas, natural gas, or air to the cooling unit 30 for liquefaction. Commercially available gas generators currently come with physical dimensions as small as 27.5 cm wide, 40 cm deep and 55 cm high.
In the cooling unit 30 the gas from the gas generator 20 is cooled by a stirling, pulse-tube or stirling-pulse-tube cooler to a temperature below the liquefication temperature for that gas. Suitable coolers are available from Sunpower, Inc. (Ohio) and Smach Co., Ltd. (Osaka, Japan). These coolers were originally developed to provide cooling for high end electronic devices for communication, infrared detection and CCD devices. The liquified gas falls from the cooling unit into an insulated container 40 (e.g. a dewar). It is not necessary that the gas be pressurized (relative to the ambient pressure). However, to avoid contamination by reverse flow of air, the pressure inside the insulated container 40 is maintained slightly higher than atmospheric pressure.
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Gas may be fed to the cooling unit 30 and insulated container 40 from the gas generator 20 in a number of ways. In the embodiment of
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In the preferred embodiments, the insulated container 40 may be detached from the system 10 and 50 to drain the liquefied gas. Alternatively, the insulated container 40 could be essentially a holding tank, from which liquefied gas could be drained via a drain port (e.g. like a water tap on a sink).
The insulated container 40 could have a gas tight sealing mechanism such that when it is disconnected from the cooling unit 30, the liquefied contents are completely isolated from the environment. In such embodiments, the insulated container 40 would also likely have a pressure release mechanism. The insulated container 40 could also be open to the air once disconnected from the cooling unit 30.
In the preferred embodiment the gas liquefaction system 10 and 50 includes means for monitoring the liquid level in the insulated container 40 such that, when the liquid reaches a certain level, the cooling unit 30 and gas supply 20 are turned off or disconnected from the insulated container 40.
Nitrogen gas generators separate nitrogen gas from air by filtration. Thus the exhaust is enriched with oxygen gas. Therefore, in embodiments of the present gas liquefaction system that are used to produce liquid nitrogen from air, it is desirable to keep the flames and heat sources away from the system.
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tumors or cancer, especially those of the skin, cervix, eye, brain, prostate and liver cancer;
certain early changes in the skin that might signal possible cancer;
actinic keratosis, a skin condition caused by sun exposure, can be treated with cryotherapy;
cervical dysplasia, or abnormal precancerous cells in a woman's cervix that can lead to cancer of the cervix;
warts, including genital warts from human papilloma virus;
other common skin lesions, such as skin tags, hemangiomas, or seborrheic keratoses;
bleeding during standard surgery;
The gas liquefaction system 50 can also be used to quickly freeze, for example, cocktail and beer glasses. It can also be used in mechanical settings or machine shops, 60 where metal parts can be quickly cooled in order make them fit together.
Accordingly, while this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to this description. It is therefore contemplated that the appended claims will cover any such modifications or embodiments as fall within the true scope of the invention.
