The gasifying agent is the most significant parameter that affects the yield from the thermochemical conversion process. However, different names were used for different products at different times in the past such as town gas, water gas, producer gas, and blast furnace gas. The name “syngas” is a general term for any gasification product. It can be produced from different feedstock like coal, liquid hydrocarbons, biomass, and other waste products and the quality varies depending on the feedstock and the gasification process. It also consists of other gases like methane, nitrogen, and carbon dioxide apart from these major gases. This is a name given for a mixture mainly comprised of CO and H 2 at varied proportions. Syngas, an abbreviation for synthesis gas, is an end product of gasification.
This conversion process is believed to be the major source of energy in the future, and instrumental in the move from carbon based to hydrogen based energy : Carbonaceous Fuel + Limited air = O + H 2 + C H 4 + C O 2 + H 2 O + N 2
This process consists of many reactions and details about the gasification process can be found elsewhere. The process is called gasification and the produced gas is called syngas. When high carbon solid fuel reacts with a controlled amount of gasifying agent at an elevated temperature of more than 600☌, carbon monoxide (CO) and hydrogen (H 2) are formed as depicted in (1). It is a thermochemical conversion process that increases the hydrogen-to-carbon ratio of the feedstock by breaking carbon bonds and adding hydrogen to the gaseous products. Among the conversion technologies, gasification is the most reliable and energy efficient with advantages in both upstream and downstream flexibility. Scarcity of conventional petroleum resources and advancement in the solid-to-gas conversion technologies has revived interest in the use of solid fuels. Therefore, proper optimization of major engine variables should be done in the current engine technology. However, late injection stratification leads to injection duration limitation leading to restriction of output power and torque. Therefore, stratification under lean operation should be used in order to keep their performance and emissions of NOx comparable to CNG counterpart. Besides, syngases have higher laminar flame speed as compared to CNG. Syngases have very low stoichiometric air-fuel ratio as a result they are not suitable for stoichiometric application. Their fuel properties are compared to those of CNG and hydrogen and the effects on the performance and emissions are studied. Therefore, three different syngases selected from the two major gasification product categories are used as case studies. Products of gasification vary with the variation of input parameters. In this paper, the technological development, success, and challenges for application of syngas in power generating plants, the trends of engine technologies, and the potential of this fuel in the current engine technology are highlighted. It was widely used for spark-ignition engines in the WWII era before being replaced with gasoline.
Syngas from biomass and solid waste is a carbon-neutral fuel believed to be a promising fuel for future engines.