Gas separation: processes – Selective diffusion of gases – Selective diffusion of gases through substantially solid...
Reexamination Certificate
2001-03-19
2003-03-04
Smith, Duane S. (Department: 1724)
Gas separation: processes
Selective diffusion of gases
Selective diffusion of gases through substantially solid...
C095S092000, C095S130000, C095S138000, C096S004000, C096S108000, C096S134000, C096S143000, C096S243000, C422S173000, C422S176000, C422S182000, C422S183000
Reexamination Certificate
active
06527828
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of thermal/wet abatement of gaseous waste streams, and more particularly to a method and system for improving performance of new scrubbers and retrofitting existing integrated scrubbers to provide maximum oxygen content in a controlled decomposition oxidation abatement process.
2. Description of the Related Art
Semiconductor manufacturing processes utilize a variety of chemicals, many of which have extremely low human tolerance levels. Such materials include gaseous hydrides of antimony, arsenic, boron, germanium, nitrogen, phosphorous, silicon, selenium and other chemical elements. A significant problem has been the removal of these materials from effluent gas streams of semiconductor manufacturing processes. While virtually all U.S. semiconductor manufacturing facilities utilize scrubbers or similar means for treatment of their effluent gases, the technology is not capable of removing all toxic or otherwise unacceptable impurities.
One solution to this problem is to incinerate the process gas to oxidize the toxic materials, converting them to less toxic forms. Conventional incinerators, however, typically achieve less than complete combustion. The problem is compounded when the process stream to be treated is composed primarily of a nonflammable gas bearing the undesirable impurities.
A further limitation of conventional incinerators is their inability to mix sufficient fuel with a nonflammable process stream in order to render the resultant mixture flammable and completely combustible. The choice of fuel gas for mixing with a nonflammable process gas is also important from the perspective of maintaining low operating costs, and the incinerator design must reflect this choice of fuel if proper burning characteristics are to be achieved. For many gases the ability to achieve higher combustion temperatures will increase the destruction efficiency of the scrubbers. Additionally the use of a higher concentration of oxygen in the thermal section of the scrubber will allow the use of a mixture that has a lower fuel value, yet will still achieve the temperatures necessary for high performance.
However, many incinerators or combustion chambers currently used in existing facilities, depending on their age and construction, are not equipped with adequate piping systems for providing an additional source of flammable fuel gas. In such situations, several options are available. Retrofitting the existing combustion chamber with additional piping to provide a controlled incineration is one such option, but the cost of this retrofitting may be prohibitive. As another option, a combustible gas may be premixed with the gaseous effluent from the semiconductor process. However, this premixing can introduce a hazard potential if the combustible mixture is ignited by the incinerator flame and the ignition propagates a flame backwards into the pipe thereby creating a concomitant explosion potential. Flame arresters can be added to prevent such flashbacks but such devices tend to clog easily because of oxide particles that are typically present in such effluent gas/combustible gas mixtures.
Accordingly, it would be advantageous to provide an improved method and system to retrofit an existing thermal reactor unit for introduction of a low cost flammable gas, which retrofit is not cost-prohibitive to install on an existing unit, and which modification does not introduce an additional explosion potential in operation of the retrofitted thermal reactor unit.
SUMMARY OF THE INVENTION
The present invention relates to a method and system for providing controlled combustion of gaseous semiconductor wastes, whereby an inexpensive fuel is introduced to facilitate the conversion of nonflammable mixtures to flammable mixtures without a cost-prohibitive retrofit of the thermal/wet integrated abatement system.
In one aspect, the invention relates to a combustion chamber having increased ability to oxidize virtually all oxidizable components in a gaseous waste stream.
Another aspect relates to improved abatement capabilities of a combustion chamber by utilizing existing ducting and adapting same to introduce oxygen for controlled decomposition oxidation of a gaseous waste stream.
Thus, in accordance with one aspect of the present invention, there is provided a system for abating gaseous waste material, comprising:
a combustion chamber having at least one gas inlet communicatively connected to a source of compressed air; and
an oxygen separation unit positioned therebetween.
Another embodiment of the present invention is directed to an abatement system for oxidative treatment of gaseous pollutants in a gas stream, the system comprising:
a thermal reactor and a gas conduit for conducting the gas stream into the thermal reactor, the gas conduit comprising at least one secondary inlet communicatively connected to a source of compressed dry air; and
an oxygen separation unit positioned between the thermal reactor and the source of compressed dry air.
Preferably, the thermal reactor is provided with an inlet for introduction of the gas stream comprising a conduit terminating with a portion of the conduit within the reactor which projects into a tube defining an area in which there is flame formation. The conduit further comprises at least one secondary inlet for introduction of different gases such as nitrogen, oxygen and fuel.
The thermal reactor further comprises a central combustion chamber accommodating heating elements. The gases exiting the thermal reactor are passed through a liquid vortex that cools the exiting gases, which then are passed through a packed bed for trapping and condensing particles. A liquid scrubber also is provided for removing chemical pollutants. The scrubber may for example comprise at least two vertically separated beds containing coated packing.
A compressor is communicatively connected to the thermal reactor to supply a source of compressed air to the oxygen separation device positioned downstream of the compressor and upstream of the thermal reactor. The compressor is used to assist in pressurizing the air flow being delivered to the oxygen separation unit, or in a subatmospheric oxygen enrichment system, utilized to increase the pressure of the oxygen-enriched stream at a location downstream of the oxygen separation unit.
The oxygen separation unit of the present invention may comprise any device with selectivity for separating one major gaseous component from the other major components in the feed gas mixture. For example, a single membrane device or alternatively a several membrane device may be provided and operated to achieve a separation of the gaseous components in air. Typically, the membrane devices are manufactured in modules, each having certain semi-permeable membrane areas for permeation. Semi-permeable membrane materials currently available which can be employed in this process include: polysulfone, cellulose acetate, polyimide, polyamide, silicone rubber, polyphenylene oxide, polycarbonate, tetra-bromo-bisphenol-A-polycarbonate, halogenated analogs of these polymers, ceramic materials, etc.
In the present application, hollow fibers formed from tetra-bromo-bisphenol-A-polycarbonate are used in a module to separate oxygen from compressed air, however other materials such as tetra-bromo-bisphenol-hexafluoro-polycarbonate can be used.
Alternatively, a ceramic material having a high selectivity for oxygen is utilized in the oxygen separation device to efficiently sorptively remove oxygen from an oxygen-containing feed gas mixture, to produce extremely high product gas purity. The ceramic material may be used as a filler material in a separation module or as a coated substrate, e.g., at least a portion of a membrane or fiber surface is coated with the oxygen-adsorbent ceramic material.
The ceramic material may comprise at least one material such as:
oxide fluorite oxygen ion conductors of the formula A
4
O
8
;
pyrochlore material of the formula A
2
B
2
O
7
;
material of the formul
Clark Daniel O.
Flippo Belynda G.
Karrup Keith
Vermeulen Robbert
Advanced Technology & Materials Inc.
Hultquist Steven J.
Smith Duane S.
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