Simultaneous Behavior of Pulverized Coal Char Combustion and Fine Iron Oxide Reduction by Injecting the Mixture of Coal Char and Iron Oxide

Abstract

The present study has been carried out to investigate the simultaneous behavior of combustion of 'pulverized coal char' (described as 'char' afterwards in this paper), and of reduction of fine iron ore using a laboratory scale tube furnace.
Experimental results show that apparent combustion rate of char is not affected by the ore/char mole ratio simultaneously injected. The reaction rate constant of char was not changed with changing wustite/char injection ratio. On the other hand, the rate constant of char increased proportionally with an increase of hematite/char injection ratio. This implies that hematite behaves as an effective oxygen source for char combustion.
The main reduction mechanism of fine wustite injected is found to be the direct reduction between molten wustite and unburnt carbon. Similarly, for the case of fine hematites, the direct reduction between molten magnetite thermally decomposed from hematite and solid carbon entrained into the droplet is the main reduction mechanism.
It was observed that the reduction degree of fine iron oxides mainly depends on the specific combustion heat (kJ/g-ore) which is defined as the ratio of combustion heat of char to the feeding rate of fine iron oxide.