Beginning Jan. 1, 2011, the U.S. Environmental Protection Agency (EPA) will introduce the next phase of its Tier 4 emissions control regulations. The regulations limit emissions of oxides of nitrogen, particulate matter, hydrocarbons and carbon monoxide. They affect the majority of non-road mobile equipment powered by diesel engines greater than 130 bkW, including mobile generator sets.
Caterpillar said stationary diesel engines, such as those used in standby and prime power generator sets, are regulated separately, but to similar standards as non-road mobile equipment. However, the challenges facing the electric power industry are unique in a number of areas, particularly above 900 bkW, where regulations focus on reducing nitrogen oxide emissions from generator sets by 90 percent, compared to a 45 percent reduction for other equipment types.
Caterpillar said it developed three engine-integrated technology packages which can be used, in combination, to address the various emission reduction levels required by the EPA regulations.
130 – 560 bkW Engine Technology: An electronically controlled air management system lowers the combustion temperature by combining a small amount of non-combustible gas with the combustion air, resulting in decreased NOx output. Aftertreatment: A diesel oxidation catalyst and particulate filter with an automated regeneration system are incorporated into the package design to reduce PM to less than the regulatory requirement.
560 – 900 bkW Engine Technology: An electronically controlled air management system lowers the combustion temperature by combining a small amount of non-combustible gas with the combustion air, resulting in decreased NOx output. As the regulated particulate matter limit is higher in this power range, the emissions control on the engine alone can meet the requirement without the need for aftertreatment.
900 bkW and above Engine Technology: Low soot combustion techniques, incorporating detail changes to piston bowl design, injector configuration and turbocharger matching. Aftertreatment: A diesel oxidation catalyst, combined with a selective catalytic reduction module, with an air-assisted urea injection system, form the clean air system for larger diesel generator sets. In addition to the Caterpillar-designed aftertreatment system, a dosing control module, diesel emissions fluid tank and air source are integrated into the generator package design.