Optimisation of coal rate and carbon dioxide emissions in Corex process

Abstract

High carbon consumption (∼700 kg per tonne of hot metal) in the Corex process has thrown challenges for process viability as compared to blast furnace and the subsequent impact on CO2 emission. The coal rate in Corex process is a function of coal composition, the quantity of excess gas generated in the process (known as export gas) and process configuration. A model has been developed both for the smelter gasifier and the reduction shaft of the Corex process, which can predict export gas quantity as a function of coal rate for a given coal and process configuration. The process condition for zero excess gas generation in export gas stream from the smelter gasifier has been predicted from the model. This also leads to minimisation coal rate. Model computations have been carried out for different coals with varied compositions. It appears that certain coals can give rise to minimum gas rates that also lead to minimum coal rates. These process conditions also lead to minimum direct CO2 emission rates of the system. Reduction in emissions tends to push the Corex process behaviour towards a typical blast furnace system emission. Further reductions in coal rates and emissions are possible if the system is run on top gas recycle mode.