Author(s)

Benson Kariuki^1,2*, Paul Njogu¹, Joseph Kamau¹, Robert Kinyua¹, Sameer Bachani²

¹Institute of Energy and Environmental Technology, Jomo Kenyatta University of Agriculture & Technology, Nairobi, Kenya.
²Department of Mechanical and Automotive Engineering, Technical University of Mombasa, Mombasa, Kenya.

Despite diesel engines being highly efficient, with low fuel consumption and reduced carbon dioxide emissions, they emit relatively high levels of particulate matter and oxides of nitrogen (NO_x) due to high exhaust gas temperatures. Engine emissions show the quality and completeness of combustion. This paper aims to present the results of a study comparing exhaust emissions from a diesel and syngas powered engine. Syngas was produced from co-firing coal and biomass in a gasifier then cleaned, cooled and applied as an alternative fuel in an engine operated from 0 - 100% load. Exhaust-emissions were monitored at this load conditions. The exhaust-temperature was measured using thermocouples and the emission gases were analyzed using Testo 350. The emissions were lower and decreased as the engine load increased, except for sulphur dioxide and NO_x. The study shows that levels of carbon monoxide, were higher in a range of 46.5 - 80.2%, while carbon dioxide was 3.3 - 18% higher compared to those from diesel. Hydrocarbon emissions were 480 and 1250 ppm for diesel and syngas respectively. The study reveals that the engine operates optimally at higher loads since hydrocarbons and oxides of carbon are low due to complete combustion at higher temperatures. Exhaust gas temperature was higher in the syngas fuel and increased as the engine load increased in the range of 455.83 - 480.03˚C which influenced the formation of NO_x. NO_x from diesel was found to be higher, ranging from 32.5 - 40.5%, compared to those from syngas with an engine load of 75%. The study observed that relative to diesel, the emissions of sulfur dioxide at 50% engine load were lower in a range of 23.7 - 57.1%. Emissions of hydrocarbons depended on the degree of substitution of diesel and engine load. The study therefore shows that, relative to diesel, emissions decreased when syngas was used with upgraded syngas from Prosporis juliflora presenting as the best alternative followed by Hyphanae compressa, and lastly rice husk. For optimal performance of the syngas fuelled engine, the study reports that the engine should be operated at engine loads above 50% with strategies on NO_x emissions considered.

Emissions, Engine Load, Temperature, Neat-Diesel, Syngas

Kariuki, B. , Njogu, P. , Kamau, J. , Kinyua, R. and Bachani, S. (2024) Comparative Study of Exhaust Emissions from Diesel and Syngas Powered 3.5 kW Compression Ignition Engine with and without Load. Journal of Power and Energy Engineering, 12, 30-46. doi: 10.4236/jpee.2024.128003.