Particle emissions from gas engine utilizing natural gas and propane as fuel

The International Maritime Organization (IMO) has implemented regulations to reduce emissions from ships. So far, these regulations consider only emissions of NOx and SOx globally, and stricter limits exist for special emissions control areas (ECAs) and in ports. The SOx regulation is expected to have an indirect impact on the contribution of shipping to particle emissions, i.e. the decrease of fuel sulphur level would also decrease the formation of sulphate particle emissions. In SOx emission control areas (SECA) the sulphur content of fuel is already limited to 0.1 %. Marine distillates, such as marine diesel oil (MDO) and marine gas oil (MGO) and low-sulphur residual marine fuel oils (hybrid fuels) are currently utilized in ships operating in SECAs. Also, the usage of alternative fuels such as liquefied natural gas (LNG) is increasing. Moreover, one option to achieve the SOx limit is by using exhaust after-treatment like scrubbers in combination with higher sulphur level fuels. In present study, we investigated how the different options in fulfilling the latest SECA limitations influence the particle emissions. These technologies include lower sulphur level liquid fuels, conversion to natural gas and utilization of scrubbers. Both, the particulate mass (PM) and particle number (PN) emissions were studied by experiments performed onboard and at marine engine laboratory.