Production of hydrogen-rich synthetic gas from low-grade coals by microwave steam-plasmas

•Hydrogen-rich synthetic gas production from low-grade coal.•Complete carbon conversion of low-grade coal at high temperature.•High-efficiency gasification by microwave steam-plasmas.

Indonesian brown-coal with high ash-content is gasified by two microwave steam-plasmas heating up the gas temperature in a reaction chamber of 1145 l in a swirl-type gasifier for production of hydrogen-rich synthetic gas. With additional heating of synthetic gas by a partial oxidation of coal, the inner temperature of the gasifier can reach to 1700 °C. The carbon conversion rate at the chamber temperature of 1640 °C is almost 100 percent, ensuring a complete gasification of carbons in a low-grade coal. The cold gas efficiency of the hydrogen-rich synthetic gas is 84%, very high in a relatively-small gasifier like the experiment here. The total calorific value of the synthetic gas is 500 kW.