Recently, the reaction of composite pellet consisting of the iron ore and carbonaceous materials such as coal, char and coke was investigated. The fast reaction rate and relatively low starting temperature were reported by many researchers. In such a reaction condition, the mechanism of reaction will be changed during reaction from the situation that the iron ore and carbon are directly contacting and to the separate situation.
The simultaneous reaction between reduction and gasification of carbon was examined using hematite–graphite facing pair, which is to clarify the effect of reaction occurring in the separated place. From the definition of coupling phenomenon, the discussion about the 'produced energy' related to the production of entropy was carried out in view point of two aspects that were (a) the gas composition change and (b) the evolution of reaction heat.
The starting temperature of gasification decreased from 900°C to 600°C in the facing pair under CO₂ atmosphere and to 250°C under CO atmosphere. The effect of reaction heat of reduction was measured and discussed through new mechanism of reduction.