PREDICTION OF BLAST-FURNACE PERFORMANCE WITH TOP GAS RECYCLING

Top gas recycling has been suggested as a method for reducing blast fu rnace fuel rates and thus reducing carbon emissions from the ironmakin g process. Three methods of top gas recycling are numerically investig ated using a mathematical model to predict the furnace performance at fixed blast volume and constant coke, ore and pulverised coal composit ions with varying recycle volumes. For each recycling method, a first calculation sequence is performed varying recycle volume at fixed ore: fuel ratio, and also a second sequence at fixed average liquid metal o utflow temperature. Simple replacement of normal blast gases with recy cled top gas is predicted to cause the production rate to decrease and the fuel rate to increase. Likewise, oxygen enriched blast replacemen t has similar effects, although the severity is less as the blast oxyg en rate is maintained in this case. Both of these methods reduce furna ce efficiency. Hot reducing gas (HRG) replacement, where CO2 is stripp ed from the recycled gas, leads to an increase in production of up to 25% with a simultaneous decrease in fuel rate of 20% at fixed metal te mperature, These calculations show that top gas recycling could be use d to increasing furnace efficiency while decreasing carbon emissions t hus making a positive contribution to efforts to prevent global warmin g.