GB938761A - Method of producing dicalcium silicate clinker and/or products containing it - Google Patents

Abstract

Dicalcium orthosilicate clinker, which is capable of disintegration by rapid cooling into a powder of grain size 0,5-20 microns, is produced by adding carbon or a material producing carbon, such as brown coal, coke, peat, tar, dry pitch or sawdust, to raw materials, e.g. mixtures of ashes, slates, smoke dusts, marls, clay, limestone or slags, which on sintering give a Ca2SiO4 clinker, heating the materials to the sintering temperature, e.g. 1250 DEG C., and adding water thereto to react with the carbon to form carbon monoxide and nascent hydrogen which effects reduction of highly oxidised stabilizers, i.e. ions at their highest valency or oxidation level such as Cr6+, As5+, Mn7+, Te6+, P5+, Ge4+, V5,, entailing an increase of their ionic radii which destroys their stabilizing action of inhibiting the transformation of the Ca2SiO4 from the b to the g phase. The raw materials are preferably selected to avoid formation of alite and reducing conditions are such that any iron compounds of the brownmillerite type are decomposed to CaO, FeO and metallic iron. For producing Ca2SiO4 powder of above grain size, the clinker, e.g. at 1250 DEG C., is rapidly cooled to a temperature e.g. 700 DEG C. to favour transformation from the b phase to the g phase, then rapidly cooled e.g. to 200 DEG C. to effect physical disintegration of the clinker.