Exhaust system for power generating apparatus

Abstract

An exhaust system for a power generating apparatus comprising a heat source for combusting a fuel in air to produce power, which exhaust system being adapted to receive a flowing exhaust gas and comprising a catalyst system for treating the exhaust gas, which catalyst system comprising a first oxidation catalyst and a second catalyst, wherein the first oxidation catalyst is positioned downstream from the heat source so that the flowing exhaust gas contacts the first oxidation catalyst before the second catalyst.

Description

FIELD OF THE INVENTION[0001]The invention relates to an exhaust system for a power generating apparatus, such as a gas turbine, which exhaust system being adapted to receive a flowing exhaust gas and comprising a catalyst system for treating the exhaust gas, which catalyst system comprising a system of oxidation catalysts. In particular, the invention relates to methods of using such systems to reduce exhaust emissions from a power generating apparatus between start-up of the power generating apparatus and full-load.BACKGROUND[0002]In normal operation, gas turbine power plants generate significant amounts of carbon dioxide (CO2), water, carbon monoxide (CO), volatile organic compounds (VOCs) and oxides of nitrogen (NOx) as part of the combustion process. Various regulatory agencies world-wide, such as the U.S. Environmental Protection Agency, are charged with reducing exhaust emissions.[0003]Gas turbine engines typically operate by drawing air into a compressor to increase the gas p...

AI Technical Summary

Benefits of technology

The invention is a system that uses two beds of oxidation catalysts to reduce emissions during start-up and running at full load in a gas turbine. The first bed is placed at a high temperature to allow for faster reduction during start-up, while the second bed is placed at a lower temperature to complete the reduction of CO and VOCs. The system provides better overall performance, is less susceptible to poisoning, and reduces the likelihood of exhaust gas bypassing the catalyst system. The first bed promotes NOx reduction, while the second bed promotes CO and VOC oxidation and NOx reduction during the start-up phase. The system also ensures a beneficial mixture of NO and NO2 in the exhaust gas, which promotes faster NOx reduction on the SCR catalyst. The first and second beds can be located a distance apart to allow for higher conversion.

Problems solved by technology

However, as exhaust gas temperatures increases from start-up to full load operation, the equilibrium constant for the NO to NO2 reaction is shifted so that the reaction is thermodynamically limited.

Images