A process for producing hot combustible gas free of sulfur, halogens and particulate matter. The process comprises passing oxygen, steam and/or carbon dioxide through a reaction zone containing an alkali or alkaline earth metal oxide, hydroxide, bicarbonate or carbonate and a carbonaceous fuel such as coal. The sulfur and halogen in the carbonaceous fuel are removed resulting in a combustible gas substantially free of sulfur, halogens and particulate matter.