Refrigeration – Storage of solidified or liquified gas – Including cryostat
Patent
1990-10-12
1993-08-24
Bennet, Henry A.
Refrigeration
Storage of solidified or liquified gas
Including cryostat
62 471, 62 501, 62 502, F17C 7102, B01J 1400
Patent
active
052378241
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a process and apparatus for delivering supercritical fluid and in particular to a process and apparatus that utilizes a high pressure vessel to deliver supercritical fluid.
2. Description of the Prior Art
Previously, supercritical fluid has been delivered through the use of high pressure pumps such as syringe pumps, membrane pumps and dual-piston pumps. Due to the high pressure requirements, these pumps are extremely expensive and are often prone to leaking, thereby reducing the efficiency. Also, these pumps can be unreliable for the delivery of fluids whose critical temperatures are below or slightly above room temperature. Since the supercritical fluid has a much lower viscosity than a "normal" liquid, the pump "leaks" if its head is above the critical temperature of the fluid. To solve this problem, it is necessary to cool off the heads, thereby increasing the complexity of the process. Further, the membrane and dual-piston pumps deliver fluid in pulses. In addition, all of the pumps are noisy. While syringe pumps can develop a high pressure quickly and do not produce a pulsating output, they have a small volume which may necessitate refilling the pump partway through an extraction process with which the pump is being used. Also, syringe pumps are more expensive than other pumps. In addition, the greater the pressure that a pump must produce, the greater the difficulty in controlling leakage and, generally, pumps are not used to produce a pressure greater than 10,000 psi. Pumps are subject to long term maintenance.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process and apparatus for supercritical fluid delivery based on high pressure vessels where a continuous supply of supercritical fluid can be produced on a consistent basis.
A process for delivering supercritical fluid for various uses has a high pressure vessel with means to cool and means to heat said vessel. The vessel has an inlet and an outlet with control means to control the flow of fluid through said inlet and through said outlet. The inlet is connected to a pressurized fluid source and the process includes the steps of lowering the temperature of the vessel below the critical temperature of the fluid while opening the inlet to fill the vessel with fluid, closing the inlet, heating the vessel while monitoring the temperature and pressure to greatly increase the pressure until the desired pressure is attained, opening the outlet to deliver supercritical fluid from the vessel while continuously adjusting the temperature during the delivery of the fluid to control the pressure as desired.
An apparatus for continuously delivering supercritical fluid is characterized by two high pressure vessels, each vessel having an inlet and an outlet. The vessels are connected in parallel and the inlets of each vessel are connected to a pressurized fluid source. There are means to cool and means to heat each vessel with control means to cool, heat, fill and empty the two vessels independently.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a block diagram of an electronic circuit for controlling pressure in an extraction system;
FIG. 2 is a block diagram of an apparatus, having two high pressure vessels, for delivering supercritical fluid;
FIG. 3 is a schematic drawing of a system for delivering supercritical fluid having a single high pressure vessel;
FIG. 4 is a graph of the change of pressure with temperature in a high pressure vessel;
FIG. 5 is a block diagram of a supercritical fluid delivery system having two high pressure vessels, one vessel containing a modifier; and
FIG. 6 is a schematic diagram of a supercritical fluid delivery system having two high pressure vessels with outlets controlled by check valves.
DESCRIPTION OF A PREFERRED EMBODIMENT
In FIG. 1, there is shown an electronic circuit for controlling the pressure in an extraction system with which the supercritical fluid delivery system of the present inve
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Bennet Henry A.
Kilner Christopher B.
Schnurr Daryl W.
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