【作者】

Heikki Korpi

【摘要】

该论文已在赫尔辛基举行的第28届CIMAC大会上发表，论文的版权归CIMAC所有。As a response to emission regulations, efficient SCR systems for NOx emission reduction of diesel engines have been developed and successfully introduced on the market. Tightening emission legislation can often be met also by introducing gas-operated engines. Despite of the low NOx, SOx, PM and CO2 emissions of gas engines, hydrocarbon emissions are getting more focus by the regulators and, consequently, also in product development. The operating temperature window of a SCR system for NOx control with high-sulphur fuels is mainly determined by ammonium bisulphate condensation at low temperature and increased SO3 formation under high temperature. The exhaust gas temperature of a single-stage turbocharged engine can be tuned for SCR operation with reasonable efforts, e.g. by controlled exhaust waste-gate and air by-pass valve operation. In 2-stage turbocharged engines, the exhaust gas temperature is further decreased creating more challenges for temperature control. Installation of SCR between the turbochargers (inter-turbine SCR) provides higher operating temperatures and compressed exhaust gas with lower volumetric flow rate. These conditions enable higher catalytic activity and a more compact SCR design compared to a post-turbine installation. An installation of reactor under pressurized conditions require detailed CFD simulation to optimize the pressure drop, flow behaviour and ammonia mixing in exhaust gas to reach high catalytic performance. The operating window for hydrocarbon oxidation catalyst in lean-burn gas engines is mainly determined by the low activity at low temperatures and non-reversible deactivation at high temperatures. Depending on the catalyst chemistry and reactivity of the targeted hydrocarbon compounds, the oxidation catalyst can be located for optimum exhaust gas temperature in a pre- or post-turbine location. While commercial solutions are available for volatile organic compound reduction, more stable methane requires more efficient catalyst. Fast deactivation of the catalyst by sulphur is the main challenge for the practical application of the methane oxidation. This paper gives an overview of the emission legislative development and the aspects of developing exhaust gas aftertreatment systems for NOx and hydrocarbons for high efficiency four-stroke medium-speed engines. Aspects of exhaust gas temperatures, pressure drop, design parameters, performance, and regeneration possibilities are discussed for the application on both 1-and 2-stage turbocharged engines. Results of simulation and engine tests with part-flow and full scale catalyst systems are presented.

【会议名称】

第28届CIMAC会议

【会议地点】

芬兰 赫尔辛基

【下载次数】

2

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