Gas separation: processes – Solid sorption – Inorganic gas or liquid particle sorbed
Reexamination Certificate
2001-11-12
2003-07-15
Simmons, David A. (Department: 1724)
Gas separation: processes
Solid sorption
Inorganic gas or liquid particle sorbed
C095S143000, C095S903000, C096S108000, C096S130000, C206S000700, C502S416000
Reexamination Certificate
active
06592653
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to storage and dispensing systems for the selective dispensing of fluids from a vessel or storage container in which the fluid component(s) are held in sorptive relationship to a solid carbon sorbent medium having low adsorption Heels, and are desorptively released from the carbon sorbent medium in the dispensing operation.
2. Description of the Related Art
In a wide variety of industrial processes and applications, there is a need for a reliable source of process fluid(s).
Such process and application areas include semiconductor manufacturing, ion implantation, manufacture of flat panel displays, medical intervention and therapy, water treatment, emergency breathing equipment, welding operations, space-based delivery of liquids and gases, etc.
U.S. Pat. No. 4,744,221 issued May 17, 1988 to Karl O. Knollmueller discloses a method of storing and subsequently delivering arsine, by contacting arsine at a temperature of from about −30° C. to about +30° C. with a zeolite of pore size in the range of from about 5 to about 15 Angstroms to adsorb arsine on the zeolite, and then dispensing the arsine by heating the zeolite to an elevated temperature of up to about 175° C. for sufficient time to release the arsine from the zeolite material.
The method disclosed in the Knoilmueller patent is disadvantageous in that it requires the provision of heating means for the zeolite material, which must be constructed and arranged to heat the zeolite to sufficient temperature to desorb the previously sorbed arsine from the zeolite in the desired quantity.
The use of a heating jacket or other means exterior to the vessel holding the arsine-bearing zeolite is problematic in that the vessel typically has a significant heat capacity, and therefore introduces a significant lag time to the dispensing operation. Further, heating of arsine causes it to decompose, resulting in the formation of hydrogen gas, which introduces an explosive hazard into the process system. Additionally, such thermally-mediated decomposition of arsine effects substantial increase in gas pressure in the process system, which may be extremely disadvantageous from the standpoint of system life and operating efficiency, as well as safety concerns.
The provision of interiorly disposed heating coil or other heating elements in the zeolite bed itself is problematic since it is difficult with such means to uniformly heat the zeolite bed to achieve the desired uniformity of arsine gas release.
The use of heated carrier gas streams passed through the bed of zeolite in its containment vessel may overcome the foregoing deficiencies, but the temperatures necessary to achieve the heated carrier gas desorption of arsine may be undesirably high or otherwise unsuitable for the end use of the arsine gas, so that cooling or other treatment is required to condition the dispensed gas for ultimate use.
U.S. Pat. No. 5,518,528 issued May 21, 1996 in the names of Glenn M. Tom and James V. McManus, describes a gas storage and dispensing system, for the storage and dispensing of gases, which overcomes the above-discussed disadvantages of the gas supply process disclosed in the Knollmueller patent. The gas storage and dispensing system of the Tom et al. patent comprises an adsorption-desorption apparatus, for storage and dispensing of a gas, e.g., a gas selected from the group consisting of hydride gases, halide gases, and organometallic Group V compounds, including: a storage and dispensing vessel constructed and arranged for holding a solid-phase physical sorbent medium, and for selectively flowing gas into and out of said vessel; a solid-phase physical sorbent medium disposed in said storage and dispensing vessel at an interior gas pressure; a sorbate gas physically adsorbed on the solid-phase physical sorbent medium; a dispensing assembly coupled in gas flow communication with the storage and dispensing vessel, and constructed and arranged to provide, exteriorly of the storage and dispensing vessel, a pressure below said interior pressure, to effect desorption of sorbate gas from the solid-phase physical sorbent medium, and gas flow of desorbed gas through the dispensing assembly.
The storage and dispensing vessel of the Tom et al. patent embodies a substantial advance in the art, relative to the prior art use of high pressure gas cylinders. Conventional high pressure gas cylinders are susceptible to leakage from damaged or malfunctioning regulator assemblies, as well as to rupture if internal decomposition of the gas leads to rapid increasing interior gas pressure in the cylinder and the risk of cylinder rupture or other unwanted bulk release of gas from the cylinder. The gas storage and dispensing vessel of the Tom et al. patent reduces the pressure of stored sorbate gases by reversibly adsorbing them onto a carrier sorbent medium such as a zeolite or activated carbon material.
The efficiency of the fluid storage and delivery system of the Tom et al. patent is directly affected by the sorbent material employed therein. Therefore, there is a continuing need in the art to identify and utilize improved sorbent materials in such fluid storage and delivery systems, and it is accordingly an object of the present invention to provide a fluid storage and dispensing system utilizing a high efficiency sorbent material which offers significant advantages in cost, ease of use, and performance characteristics.
SUMMARY OF THE INVENTION
The present invention contemplates a system for storage and dispensing of a sorbable fluid, e.g., a gas, vapor, liquid, multiphase fluid, etc., including fluid mixtures as well as single component fluids.
In one aspect, the invention relates to an adsorption-desorption apparatus, which comprises a storage and dispensing vessel for holding a low Heel carbon sorbent medium therein at an interior gas pressure, a sorbable fluid physically adsorbed on said low Heel carbon sorbent medium; and a dispensing assembly coupled in gas flow communication with the storage and dispensing vessel and arranged for dispensing from the vessel sorbable fluid desorbed from the solid-phase carbon sorbent medium.
The term “Heel” is defined herein as the amount of residual sorbate fluid (in grams) that is retained by a sorbent material after desorption, under a certain pressure and at a certain temperature, per unit volume (in liters) of bed of the sorbent material, which is considered irremovable or disproportionately difficult to remove from the sorbent material. This portion of sorbate fluid constitutes waste and reduces the sufficiency of the fluid storage and dispensing system.
The phrase “low Heel” as used in the present application is defined as being characterized by at least one of the following: (i) Heel, measured for gaseous arsine (AsH
3
) at 20° C. at 20 Torr, of not more than 50 grams AsH
3
per liter of bed of the sorbent material; (ii) Heel, measured for gaseous boron trifluoride (BF
3
) at 20° C. at 20 Torr, of not more than 20 grams boron trifloride per liter of bed of the sorbent material; (iii) Heel, measured for gaseous germanium tetrafluoride (GeF
4
) at 20° C. at 20 Torr, of not more than 250 grams GeF
4
per liter of bed of the sorbent material; (iv) Heel, measured for gaseous arsenic pentafluoride (AsF
5
) at 20° C. at 20 Torr, of not more than 700 grams AsF
5
per liter of bed of the sorbent material; (v) Heel, measured for gaseous trimethyl silane (3MS) at 20° C. at 20 Torr, of not more than 160 grams 3MS per liter of bed of the sorbent material; and (vi) Heel, measured for gaseous ethane (C
2
H
6
) at 21° C. at 25 Torr, of not more than 10 grams ethane per liter of bed of the sorbent material.
Preferably, the carbon sorbent material employed by the present invention has both a low Heel and a high Sorbent Working Capacity.
The phrase “Sorbent Working Capacity” (C
w
) is defined herein as the amount of sorbate fluid (in grams) originally loaded on the sorbent medium that is removable from the sorbent medium in the fluid dispensing op
Salsbury Joseph
Wang Luping
Advanced Technology & Materials Inc.
Lawrence Frank
Ryann William F.
Simmons David A.
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