EFFECT OF PRESENCE OF CARBON, IRON, AND SULFUR ON RATE OF ALKALI RELEASE FROM CAO-AL2O3-SIO2 SLAGS

The kinetics of alkali oxide (K2O or Na2O) release from a wide range o f CaO-Al2O3-SiO2 slags containing additions of graphite, iron, iron su lphide, or calcium sulphide has been studied. The kinetics of alkali o xide release has been determined by heating in graphite crucibles and by subsequent chemical analysis of solidified slag samples. Additions of graphite powder to the slag result in an initial rapid loss of alka li. This is associated with the kinetics being controlled by mass tran sfer brought about by stirring of the slag phase by bubbles generated by slag-graphite reactions, The presence of iron in the slag results i n the graphite crucible becoming more easily wetted by the slag and, h ence, in an enhancement of reaction kinetics. The presence of sulphur in the slag results in the graphite crucible becoming less easily wett ed by the slag and, hence, in a reduction of reaction kinetics.