Slagging gasification melts the ash in gasification to a slag, which is a low leaching potentially saleable product. The slagging gasifier operates at high temperatures of about 1500^oC for the ash to be melted. The high gasifying temperatures ensure the destruction of complex hydrocarbons such as aromatics, and even methane. This results in lower energy requirements for gas purification (Perdaman, 2009 p.25).

To reduce the melting point of ash, limestone is added as fluxing agent to the coal. In this way, the gasification process proceeds in lower temperatures improving the thermal efficiency. Slagging gasification will decrease oxygen consumption, thereby reducing electricity use for oxygen production (Perdaman, 2009 p.25).