Stationary IC Engines
Large IC engines are used for power generation as well as in gas compression and in the oil and gas sector. They are also used in shipping. Typical emissions to air that can be controlled are NOx, CO, unburned Hydrocarbon (fuel) referred to as Volatile Organic compounds and particulate material. Three-way catalysts can remove NOx, CO and VOC from a gasoline engine exhaust. Here the exhaust gas chemistry is controlled to ensure a balance of oxidation with reduction.
Diesel engines, using lean burn combustion so there is a surplus of oxygen in the exhaust gas, require separate SCR and oxidation processes to reduce the NOx and oxidise the CO and VOCs. In clean exhaust gas particulate matter can be oxidised in a wall flow filter. For other cases e.g. exhaust gas from sulphur containing fuel such as HFO, other filtration methods such as applications of filter candles have been developed.
IC engine Gas compressors such as the Loudon compressor station in Clarksburg, and that in Sacramento have been running with catalytic after treatment since 2004. The emissions for four of these engines are reported in the table below. The emissions of NOx and CO meet with local permitting requirements.
With advanced catalyst design and cleaner exhaust gas, catalysts age and decay less rapidly and recharge periods can be extended lowering the total cost of operation.