Syngas (Synthetic Gas) is the name given to the gas produced by gasification and pyrolysis processes. It is given off when a carbon material is broken down by heat (700C +) with a controlled amount (or absence) of oxygen or steam, without combustion. The typical main components of Syngas are hydrogen, carbon monoxide and carbon dioxide. Other gases are also produced. The composition of Syngas will vary greatly due to the type of process and the raw material. Gasification produces gas only whereas a pyrolysis will produce a liquid fraction as well.
Gasification is an established process, the manufacture of charcoal is a crude version. Syngas production from the gasification of coal to produce coke was used as “town gas”. Coke oven gas is now used within the steel industry. Gasification of waste material, such as wood or household waste, is undertaken but few plants are successful on a large and environmentally clean scale.
Syngas can be used directly in engines with coke oven gas a good example. However, the variability of the gas and the contaminants, particularly tars, can make it problematic. With waste feedstocks gas clean-up is essential.
Syngas can often have a very low calorific value. This and the hydrogen component of syngas reducing the methane number lead to a de-rate when compared to a natural gas output.