Liquid purification or separation – Automatic control
Reexamination Certificate
1994-03-21
2001-06-26
Savage, Matthew O. (Department: 1723)
Liquid purification or separation
Automatic control
C210S251000, C210S541000, C210S542000, C422S256000, C422S257000, C422S258000, C422S259000, C422S260000
Reexamination Certificate
active
06251267
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to supercritical fluid extraction.
In supercritical fluid extraction, an extraction vessel is held at a temperature above the critical point and is supplied with fluid at a pressure above the critical pressure. Under these conditions, the fluid within the extraction vessel is a supercritical fluid. In one type of apparatus for supercritical extraction, there is a specially constructed extraction vessel within a source of heat.
A prior art apparatus for supercritical extraction of this type is described by B. W. Wright, et. al., in ANAL. CHEM. 59, 38-44 (January 1987) using a glass-lined extraction chamber within a bolted stainless steel extraction vessel heated in an oven. This type of extraction apparatus has the disadvantages of: (1) requiring time consuming steps to open the pressurized extraction vessel before use to insert the sample and again to open it after use to remove the spent sample; and (2) under some circumstances, requiring the handling of a hot extraction vessel.
Prior art apparatuses for automatically changing samples are known. For example, Beckman Instruments, Inc. has produced a radioimmuno and a biogamma analyzer that incorporates a sample changer with an elevator mechanism that raises sample vials from a sample changer to a lead-shielded radiation counting chamber above the sample chamber. Also, a gamma series 300 unit manufactured by Beckman Instruments, Inc., automatically interposes a thick lead shutter that separates the sample vial and the counting chamber from the environment outside the counting chamber. These devices are described in Beckman Bulletin 7250 dated approximately 1972 or 1973. Another apparatus was produced by Micromedic Systems, a division of Rhom and Haas, called the Micromedic Concept 4. It is described in Bulletin M1515 dated 1976.
Two patents describing systems of this type are U.S. Pat. No. 3,257,561 to Packard et al issued Jun. 21, 1966, for RADIOACTIVITY LEVEL DETECTING APPARATUS FOR SAMPLES CARRIED BY PORTABLE TRAYS WITH TRANSFER AND INDEXING MEANS FOR THE TRAYS and U.S. Pat. No. 3,198,948 to Olson issued Aug. 3, 1965, for APPARATUS FOR MEASURING ACTIVITY LEVELS OF RADIOACTIVE SAMPLES.
These devices are not suitable for handling the high temperature, high pressure fluid systems necessary for supercritical extraction.
To control the flow of supercritical fluids for an automatic supercritical fluid extractor, automatic valves are needed. Preferably, the valves are of economical construction and contain all the features of being able to handle high pressure, high temperature and have long life.
Prior art inexpensive automatically programmable valves do not contain all of these features and thus suffer from one of more of the disadvantages of short life, inability to handle high temperature, high cost or inability to handle high pressure.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a novel supercritical extraction technique.
It is a still further object of the invention to provide a novel supercritical extraction apparatus.
It is a further object of the invention to provide a novel supercritical extraction technique which is able to use less expensive containers for samples to be extracted than prior techniques.
It is a still further object of the invention to provide a novel supercritical extraction apparatus and method in which a series of samples may be automatically processed with a minimum of handling by an operator.
It is a still further object of the invention to provide a novel supercritical extraction apparatus and method which utilizes a novel inexpensive valve for controlling the flow of supercritical fluid.
It is a still further object of the invention to provide a novel inexpensive valve capable of handling high temperatures, high pressures, and of having long life.
In accordance with the above and further objects of the invention, a supercritical fluid extraction system includes a cartridge capable of holding the sample to be extracted and a pressure vessel into which the cartridge fits. The pressure vessel fits into a heater and the cartridge is removably mounted to a breech plug that seals the pressure vessel. There are separate outlets for the cartridge and pressure vessel to permit equalization of pressure on the inside and outside of the cartridge without contamination from impurities outside the cartridge but inside the pressure vessel.
The cartridge: (1) may be removed by a handle that is separated from the cartridge by a thermal barrier and extends outside of the pressure vessel so that the cartridge may be removed by the handle even though the cartridge is still hot; (2) receives the supercritical fluid at a pressure similar to the pressure in the pressure vessel and at substantially the same time so that the cartridge may be made of plastic and need not be excessively strong since its internal pressure is matched by the pressure outside of it; and (3) is easily fastened to a plug for the pressure vessel and the combination is easily inserted into the pressure vessel and removed from it.
A heating block for heating the cartridge is mounted to hang from the cabinet for the apparatus and the valves and tubing used in supercritical fluid extraction are mounted close enough to be heated by it to avoid premature condensation. The pressure vessel is press fit into the heater and the cartridge fits into the pressure vessel with only slight clearance to reduce heat loss and increase speed of operation.
To permit programmable valves to open and close and thus control the flow of high pressure fluids into the pressure chamber of a supercritical fluid extractor, a valve is provided having a valve seat that receives a spherical or ball-shaped valve element and a valve stem that is moved reciprocally to force the valve element into the seat or to release it. The ball is free to rotate upon being released and the supercritical fluid flows past the ball through the seat and into the pressure vessel.
To avoid scarring the ball as it rotates which would reduce its life, in one embodiment, the face of the stem is at least 1.3 times as hard as the valve seat and no more than 0.5 times as hard as the surface of the spherical valve element. The spherical valve element is at least three times as hard as the valve seat, and the valve seat has a hardness sufficient to withstand a pressure of 20,000 p.s.i. without substantial scarring. In the preferred embodiment, the face of the stem is at least 1.3 times as hard as the valve seat and no more than 0.8 times as hard as the surface of the spherical valve element.
In the preferred embodiment, the reciprocating stem that forces the valve element to close or releases it is controlled by a rotary motor. The rotary motor can be controlled by a program in a computer or other programmable circuit that activates the motor or clutch or the like to cause rotation. The rotating stem is connected to a rotary element that moves up and down to move the stem but does not cause the stem to rotate with it but only causes it to reciprocate.
To automate the operation under the control of a microprocessor, a motor operated fraction collector, a motor operated sample source and a motor operated sample injector automatically move samples and collection containers into an extraction station, injects samples into the extraction pressure vessel, performs extraction and collects extractant in different appropriate collection containers in a timed sequence to permit extracting of a series of samples with minimum human handling.
In the preferred embodiment, a movable motor member is aligned with an opening in a sample cartridge reel that moves sample cartridges carrying samples into the extraction station and with an opening in the extraction pressure vessel. The movable member is dimensioned to be capable of sealing a correspondingly sized opening in the pressure vessel and adapted to move the sample cartridge into the pressure vessel and seal the pressure vessel. Motors are provided to operate the valves to permit the e
Allington Robert William
Clay Dale Lee
Jameson Daniel Gene
Winter Robin Randall
Carney Vincent L.
Isco, Inc.
Savage Matthew O.
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