Chemical apparatus and process disinfecting – deodorizing – preser – Physical type apparatus – Means separating or dissolving a material constituent
Reexamination Certificate
1999-02-18
2001-01-30
Soderquist, Arlen (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Physical type apparatus
Means separating or dissolving a material constituent
C422S070000, C134S040000, C210S198200
Reexamination Certificate
active
06180069
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to supercritical fluid extraction apparatus and particularly to a system for cleaning flow restrictors employed in such apparatus.
The use of supercritical fluid extraction is known for the analysis of the content of fat in samples. One such system that is commercially available is the FA-100 fat analyzer manufactured by Leco Corporation of St. Joseph, Mich. In this system, a carrier fluid such as liquefied carbon dioxide is heated under pressure from 31° to 150° C. to become a supercritical fluid that passes through a heated extraction assembly in which samples are placed. The supercritical fluid and solvated sample then flows through a flow restrictor, preferably a heated variable restrictor valve, and subsequently into a trap for the collection of fat contained in the sample. Although in the preferred embodiment heated variable restrictor valves are employed, other flow restrictors for the purposes of removing the fat content of a sample, such as capillary tubes or manually adjusted restrictor valves, can also be employed.
With such systems, the flow restrictor eventually becomes clogged with the sample material extracted, which is deposited in the restrictor until at some point in time it prevents the proper functioning of the equipment. It is necessary, therefore, to remove and clean the flow restrictors from the system on a schedule which is a function of how often the equipment is being used but can be required on at least a monthly basis. This requires an operator to disconnect and remove the flow restrictors from the system, clean the flow restrictors either mechanically or chemically or both, and subsequently reassemble the apparatus, resulting in significant cost as well as down time for the operation of the system.
SUMMARY OF THE INVENTION
There exists a need, therefore, for a system in which the restrictor in a supercritical fluid fat analyzer can be cleaned without requiring disassembly of the system and one which minimizes interference with the operation of the system and requires little operator intervention. The system of the present invention accomplishes these goals by providing a source of oxidizing gas which flows through the system during a cleaning cycle in which the flow restrictors are heated for a period of time sufficient to oxidize and remove the built up residue from prior analysis. In a preferred embodiment of the invention, the source of oxidizing gas is compressed air which is supplied at a pressure of from about 20 to about 40 psi into the normal flow path for the supercritical fluid, while at the same time the flow restrictors are heated to a temperature of from about 300° to about 400° C. and preferably about 350° C. In a preferred embodiment of the present invention, a heater assembly employs a resistance heater that is positioned to heat a plurality of heated variable restrictor valves employed in a system. In a preferred embodiment of the invention also, the cleaning cycle is automatically timed for a period of approximately 12 hours, such that the system can be cleaned overnight when analyses are not normally performed.
With such a system and method, therefore, the flow restrictors are cleaned without requiring removal of the flow restrictors from the analyzer, their disassembly and mechanical and/or mechanical and chemical cleaning, reassembly, and reattachment. Further, the system of the present invention can be used to clean the flow restrictors automatically during time periods when the system is not in operation and requires only the entry of a clean cycle command by an operator, therefore, eliminating the time consuming operator intervention required in prior art systems.
These and other features, objects and advantages of the present invention will become apparent upon reading the following description thereof together with reference to the accompanying drawings.
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H. Engelhardt et al, J. Chromatogr. Sci. 1993, 31, 13-19, Jan. 1993.
SFX Supercritical Fluid Extraction from Isco, Feb., 1996.
Super Critical Fluid Extraction as a Method for Fat Determination, A Marketing Report, 1987.
Supercritical Fluid Extraction, by Dionex, Jan., 1993.
Supercritical Fluid Extraction and Its Use in Chromatogrphic Sample Preparations, Blackie Academic (published more than one year ago).
Supercritical Fluid Technologies Inc. brochure (1996).
Leco Corporation
Price Heneveld Cooper DeWitt & Litton
Soderquist Arlen
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