On the specially created experimental installation is investigated low temperature slagification in an interval of temperatures 500 up to 1200 ОC. Is detected, that low temperature slagification is connected to a plastic state of main coal weight and occurs at temperatures below than melting temperature of ashes. The temperature intervals of a beginning and most active slagification for Kuznetsks, Karagandas, Ekibastuzks and Berezovsks coals are defined. The detected porous structure of slag, allows to specify necessity of duly application of methods of deleting of slag, in order to prevent its sintering and solidification. On expiration of a mild period the slag is cemented with a surface of heating, that essentially complicates deleting slag and clearing of surfaces.