Apparatus, system, and method for oxidizing methane in a lean-burn engine exhaust
AssigneeMiratech Group, LLC
InventorsTracy D. Staller, Steven G. DeCicco
Life of this patent
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Abstract
A system, apparatus, and method for oxidizing methane in the exhaust gas from a lean-burn combustion gas engine in which a syngas stream comprising H2 and CO, or a combustible hydrocarbon with a light-off temperature at or below the temperature of the engine exhaust temperature, is added to and combined with the engine exhaust stream and passed through an oxidation catalyst whereupon the combustible gas oxidizes and increases the operating temperature of a platinum group oxidation catalyst sufficiently to exceed the light-off temperature of the platinum group catalyst for oxidizing methane emissions contained in the engine exhaust stream.
Claims29
A method of oxidizing methane in an exhaust gas produced by a lean-burn engine comprising the steps of:
- a) discharging from the lean-burn engine an exhaust gas stream which comprises an amount of methane, the exhaust gas stream having a temperature of less than 900° F.;
- b) delivering the exhaust gas stream through an exhaust oxidation system of an oxidation assembly, the exhaust oxidation system having one or more exhaust oxidation stages, the one or more exhaust oxidation stages comprising at least a final oxidation stage, the final oxidation stage having an oxidation catalyst therein which comprises one or more of platinum, palladium, and rhodium, and the temperature of the exhaust gas stream being less than a methane light-off temperature of the oxidation catalyst in the final oxidation stage, and
- c) prior to step (b), adding a combustible gas stream to the exhaust gas stream which flows through the exhaust oxidation system with the exhaust gas stream and is oxidized in the one or more exhaust oxidation stages to increase the temperature of the exhaust gas stream and heat the oxidation catalyst in the final oxidation stage to a temperature above the methane light-off temperature of the oxidation catalyst, the combustible gas stream and the exhaust gas stream forming a combined exhaust gas and combustible gas stream, the combustible gas stream having a light-off temperature on the oxidation catalyst in the final oxidation stage which is less than the methane light-off temperature of the oxidation catalyst, the combined exhaust gas and combustible gas stream having a temperature upstream of the one or more exhaust oxidation stages of the exhaust oxidation system which is less than the methane light-off temperature of the oxidation catalyst, and the light-off temperature of the combustible gas stream on the oxidation catalyst being less than or equal to the temperature of the combined exhaust gas and combustible gas stream upstream of the one or more exhaust oxidation stages of the exhaust oxidation system.
An oxidation system for oxidizing methane in an exhaust gas stream produced by a lean-burn engine comprising:
- one or more exhaust oxidation stages through which the exhaust gas stream is delivered, the one or more exhaust oxidation stages comprising at least a final oxidation stage, the final oxidation stage having an exhaust oxidation catalyst therein which comprises one or more of platinum, palladium, and rhodium in a total amount of from about 5 grams to about 120 grams per cubic foot of the exhaust oxidation catalyst, and the exhaust oxidation catalyst having a methane light-off temperature which is greater than a temperature of the exhaust gas stream;
- a syngas reactor in which a syngas stream comprising H2 and CO is produced by partial oxidation and/or reforming of a fuel-rich mixture comprising a stream of fuel having a stream of air combined therewith, the syngas stream being added to the exhaust gas stream prior to delivering the exhaust gas stream through the one or more exhaust oxidation stages, and the syngas stream being added to the exhaust gas stream and oxidized in the one or more exhaust oxidation stages in an amount sufficient to heat the exhaust oxidation catalyst in the final oxidation stage to a temperature above the methane light-off temperature of the exhaust oxidation catalyst;
- and
- a control system which directly or indirectly maintains the temperature of the exhaust oxidation catalyst in the final oxidation stage above the methane light-off temperature of the exhaust oxidation catalyst by directly or indirectly controlling the amount of the syngas stream which is added to the exhaust gas stream.
Dependencies are inferred from the claim text.