High-Energy Synthesis Gases from Waste as Energy Source for Internal Combustion Engine

The aim of the presented article is to analyse the influence of the composition of synthesis gases with mass lower heating values in the range from 12 to 20 MJ/kg on the performance, economic, and internal parameters of an atmospheric two-cylinder spark-ignition combustion engine suitable for a micro-generation unit. The analysed performance parameter was the torque. The economic parameters analysed were the hourly fuel consumption and the engine's effective efficiency. The analysed internal parameters of the engine were the indicated mean effective pressure, the pressure profiles in the cylinder, the course of the maximum pressure in the cylinder, and the course of the burning-out of the fuel in the cylinder. The analysed synthesis gases were produced by thermo-chemical processes from waste containing combustible components (methane, hydrogen and carbon monoxide) as well as inert gases (carbon dioxide and nitrogen). Higher hydrocarbons, which may be present in a synthesis gas, were not considered in this contribution because of their easy liquefaction at higher pressures in pressure bottles. A total of ten gases were analysed, all of which fall into the category of high-energy synthesis gases. The measured data from the operation of the combustion engine running on the examined gases were compared with the reference fuel methane. The measured results show a decrease in the performance parameters and an increase in the hourly fuel consumption for all operating loads. Specifically, at the engine speed of 1500 rpm, the drop in performance parameters was in the range from 9% to 24%. The performance parameters were directly proportional to the lower volumetric heating value of the stoichiometric mixture of gases with air. The rising fuel consumption proportionally matched the increase in the mass proportion of fuel in the stoichiometric mixture with air. The effective efficiency of the engine varied from 27.4% to 31.3% for different gas compositions, compared to 31.6% for methane. The conclusive results indicate that the proportion of hydrogen, methane and inert gases in the stoichiometric mixture of synthesis gases with air has the greatest influence on the course of fuel burning-out. The article points to the potential of energy recovery from waste by transforming waste into high-energy synthesis gases and their use in cogeneration.