Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture
Reexamination Certificate
1997-06-10
2001-03-27
Griffin, Steven P. (Department: 1754)
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
C423S24000R, C423S24000R, C423S245100, C423S245200, C423S245300, C423S246000, C423S247000, C423S248000
Reexamination Certificate
active
06207120
ABSTRACT:
TECHNICAL FIELD
This invention relates to catalytic vent gas treatment systems for abatement of volatile chemical emissions. More particularly, the present invention relates to apparatus and methods for abatement of carbon monoxide and volatile organic compound emissions from industrial processes having a vent gas stream containing potential pollutants.
The instant invention provides vent gas treatments which include; oxidizing, simultaneously a selected combustible fluid dispersed in a vent gas stream and destroying a substantial fraction of the hazardous volatile organic compounds by oxidation over an oxidation catalyst at elevated temperatures, controlling the amount of combustible fluid being delivered to the vent gas stream so as to provide sufficient reactants for the catalytic oxidation to maintain a suitable range of reaction temperatures, cooling the oxidation effluent stream with the untreated vent gas steam, and passing the cooled oxidation effluent gas stream through a gas scrubbing tower.
Several aspects of this invention relate to processes for commercial manufacture of organic acids, particularly dibasic aromatic acids formed from a corresponding methyl substituted aromatic compound by liquid-phase oxidation of the methyl groups by contact with source of dioxygen, such as compressed air, in the presence of an oxidation catalyst system containing one or more compounds derived from a halogen. Integrated treatment systems according to this invention are, advantageously, used for abatement of carbon monoxide and volatile organic compound emissions from liquid-phase oxidation processes of forming aromatic acids.
Processes in accordance with this invention achieve, typically, destruction efficiencies for carbon monoxide in a range upward from about 90 percent to about 95 percent and higher, destruction efficiencies for hydrocarbons in a range upward from bout 80 percent to about 90 percent or greater. Processes using selected oxidation catalysts in accordance with this invention may, advantageously, achieve destruction efficiencies for alkyl halide compounds in a range upward from about 50 percent to about 85 percent or more.
BACKGROUND OF THE INVENTION
Both thermal and catalytic incineration is widely known and used for destruction of hazardous volatile organic compounds found in waste air and other gas streams which result from a variety of industrial processes. These streams result from processes for manufacture of organic chemicals and polymers, and from operations in which volatile organic solvents are used for cleaning and degreasing purposes in metal processing, machining and finishing. While catalytic incineration is able to operate at significantly lower temperatures and with considerably lower residence times than the thermal incineration alternative, additional equipment including a furnace and/or other heat exchange equipment have, typically, been required to provide a suitably elevated operating temperature to obtain catalytic activity for destruction of hazardous volatile organic compounds from a variety of industrial processes.
In any commercially viable application of catalytic incineration, special care is required in selection of an oxidation catalyst system appropriate to the volatile organic compounds which it is desired to destroy, and to avoid exposure of the selected catalyst to compounds which destroy its catalytic activity. Many of the gas streams which must be treated contain significant amounts of a halogen and/or halogenated compounds. However, precious metal catalysts used in conventional catalytic incineration are severely inhibited in their performance by the halogen atoms from the destruction of these compounds, and this desirable process cannot generally be used with such catalysts for these gas streams.
Recent and continuing interest in reduction of atmospheric pollution from internal combustion engines used in automotive and other vehicular applications is shown by numerous disclosures of apparatus for such intermittent operation. It is typically, stated that a reduction of atmospheric pollution and/or that some regulatory standard could be met using the disclosed apparatus. Achievement of significant improvement, however, may depend upon combination of any particular apparatus with modified engine designs and special fuels. Fuel quality improvements included, generally, both removal from the fuel composition of compounds which are known precursors of particular pollutants and blending with additional compounds which may change the composition of exhaust gases.
Recently issued U.S. Pat. No. 5,193,340 in the name of Tetsuya Kamihara and assigned to Nissan Motor Co. Ltd., is a representative of exhaust gas systems for internal combustion engine application. Most diesel engines are now equipped with a trap filter dispose in an exhaust passageway for trapping particulates and the like which are discharged from a diesel engine. When the back pressure of the engine increases due to the accumulation of the particulates trapped by the trap filter, the particulates are periodically burned to regenerate the trap filter. In the Kamihara apparatus the trap filter contains an oxidation catalyst for assisting burning of the particulates collected in the filter prior to regeneration. An injector valve is provided to inject diesel fuel into the exhaust passageway upstream of the trap filter, so that the trap filter is supplied with diesel fuel. The diesel fuel is burned in the trap filter under the action of the oxidation catalyst thereby burning the particulates so as to achieve a regeneration operation for the trap filter. When in operation, the amount of diesel fuel injected is controlled to increase as an intake air amount supplied to the engine increases and to decrease as an exhaust gas temperature increases, to limit or avoid thermal damage to the trap filter. When the particulates are periodically burned to regenerate the trap filter, the back pressure of the engine due to the accumulation of the particulates trapped by the trap filter is decreased thereby preventing the pack pressure from affecting engine performance. Undisclosed amounts of increased gaseous pollutants are exhausting to the atmosphere from the system during regeneration operation due to the additional diesel fuel burned.
Additional methods for filtering combustible particles from exhaust gases and rejuvenating the filter bed and its catalyst section are, for example, described in U.S. Pat. No. 4,322,287, U.S. Pat. No. 4,359,862 and U.S. Pat. No. 4,372,111 in the names of Kashmir S. Kirk and Martin Alperstein, and U.S. Pat. No. 4,359,863 in the names of Kashmir S. Kirk and Robert B. Burns, all assigned to Texaco Inc.
An earlier example of catalytic incineration equipment in which a gas-permeable bed of solids adapted to exchange heat with a gas stream is alternately heated with hot effluent from a catalytic oxidation bed and cooled with gas flowing into the bed by periodically reversing the direction of gas flow through the beds is described in U.S. Pat. No. 2,946,651 in the name of Eugene J. Houdry and assigned to Oxy-Catalyst, Inc. In operation, the patent states that sufficient diesel oil was injected into the heated gas stream and vaporized and then catalytically oxidized on the catalytic bed being used to heat the bed of gas-permeable solids. The catalyst employed was in the form of pellets of activated alumina impregnated with 5 percent of copper and chromium oxides and 0.1 inch in size. The heat exchange bed was the same size pellets composed of a dense fused alumina (Corhart).
Additional methods using preheating and or reversing flow for catalytic cleaning of exhaust gases are, for example, described in U.S. Pat. No. 4,059,676 in the names of Kang Yang and James D. Reedy, and assigned to Continental Oil Company; U.S. Pat. No. 4,877,592 in the names of Jury S. Matros, Viktor A. Chumachenko, Ljudmila J. Zudilina, Alexandr S. Noskov and Evgeny S. Bugdan, and assigned to Institut Kataliza Sibirskogo Otdelenia Akademii Nauk SSSR; Spetsialnoe Konstruktorsko-Technologiches
Abrams Kenneth J.
Belmonte Frank G.
Oppenheim Judith P.
BP Amoco Corporation
Chi Anthony R.
Griffin Steven P.
Nave Eileen E.
Nemo Thomas E.
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