Development of a high efficiency cogeneration system using biogas for the lower pollution of the environment - (Part 3): combustion characteristics in lower load of a dual fueled CGS using intake air heating and EGR

摘要

In the utilization of the dual fueled cogeneration system (CGS) operated with biogas and gas oil, the CGS has a problem that its thermal efficiency is decreased under dual fuel operation in lower loads. It is supposed that the causes of the problem are the emission of unburned methane that loses energy of biogas, and the decline of combustion speed which decreases conversion efficiency from heat to mechanical power. To solve these problems, the CGS was remodeled with the intake air heating and the exhaust gas re-circulation (EGR) to improve methane combustion. The test results indicate that the intake air heating is effective on improvement of combustion and on reduction of unburned methane emissions although it increases NO{sub}x emissions. EGR also accelerates combustion of methane due to intake air temperature higher, and reduces NO{sub}x emissions because it decreases 02 concentration of charge. Therefore, it is concluded that EGR is the