Stationary reciprocating internal combustion (IC) engines are widely used around the world in a variety applications including natural gas production, natural gas transmission, power generation, combined heat and power (CHP) generation, pumping, and carbon dioxide production for greenhouses. These engines can be spark ignited (natural gas, propane or gasoline) or compression ignited (diesel). As demand for distributed generation of electricity increases, stationary engines have been found to be very reliable for prime power, backup or emergency standby power and for peak power.
Diesel engines are widely used in emergency back up generators and for water pumping, especially when the electrical grid is down. In places where an electrical grid is not accessible or available, diesel engines are used to generate prime power as a distributed generating source. Many of these places are often very remote, such as an island.
Johnson Matthey leads the world in the development and application of diesel oxidation catalyst (DOC) and diesel particulate filter (DPF) and offers a wide range of catalysts, catalytic converters, DOCs and CRT® DPF's. These products have high sulphur tolerance and reduced SO2 conversion for the reduction of CO, HC and PM emissions.
Gas engines, typically fuelled by natural gas or propane, are widely used for prime power and for gas compression. In gas compression, the types of engines are either rich burn or lean burn. Rich burn (or stoichiometric) engines have an air to fuel ratio that is balanced, resulting in an exhaust O2 content of about 0.5%. Lean burn gas engines have an exhaust O2 content typically >8%. For gas production, or gas gathering, the engines can be either rich or lean. For gas transmission, the engines are all lean burning
Gas engines are also used for prime power applications, especially where it is convenient to connect a natural gas line to the engine. Both stoichiometric and lean burn engines are used for decentralised power or distributed generation, cogeneration and combined heat and power plant (CHP) applications.
Regulators are concerned with controlling NOx , HC and CO emissions from stationary engines. Since NOx and VOC combine with UV light to form ground level ozone, air agencies are most concerned with reducing NOx emissions. More recently, controlling PM emissions from stationary diesel engines have been gaining ground. California , USA started the trend by categorizing diesel particulate emissions as an air toxic. This prompted the regulation of PM in California. Since PM also contributes to haze caused by fine particulate such as sulfates, controlling PM emissions will likely increase in the future.
In Europe, regional and local agencies in coordination with the European Union (EU) and European Environment Agency (EEA) have mandated the control of emissions from these engines to varying degrees, depending on factors such as engine size, engine location, site limits, operating hours, annual emissions rate, regional non-attainment status, existing or new engine, etc. NOx , CO and VOC emissions have been specifically targeted. In the US, rules have recently been specifically developed to control Hazardous Air Pollutants (HAP) including formaldehyde, acetaldehyde, acrolein and methanol. In Europe, countries such as Denmark and Germany have also sought to regulate these compounds. In California, particulate matter (PM) has been deemed an air toxic and programs have been instituted to control PM from stationary diesel engines with similar measures under way in Europe and the rest of North America.
Primary measures to reduce exhaust emissions involving in-cylinder, fuelling and lubrication oil modifications can be very effective but can also adversely affect output performance. Increasingly, secondary measures, involving catalytic and filtration technologies are being specified to meet local or national emissions regulations.
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