The integrated coal gasification combined cycle (IGCC) is expected to improve the thermal efficiency of coal-fired power generation more. In Japan, coal gasifiers will be required to handle various coals imported from many countries, just as existing pulverized coal-fired boilers do. In the coal gasifier, ash contained in coal is fused into liquid slag, and the fused slag flows through a slag-tapping hole separately from the syngas. The hole must be heated adequately to maintain the flow of the fused slag. In this study, a heating technique that works by supplying additional oxygen and nitrogen just below the slag-tapping hole was developed to handle coals with high ash fusing temperature. In gasification tests conducted in a 150 t/d coal gasifier, the fused slag was separated stably from coal at 1783 K which was the highest temperature handled without using flux or auxiliary fuel. This technique can expand the versatility of coal gasifiers as far as the coal types that can be used. (C) 2015 Elsevier B.V. All rights reserved.