Carbonising mechanism and carbon distribution behaviour during direct reduction in shaft furnace

The process of sponge iron production in a shaft furnace has been simulated in the laboratory. On the basis of the results obtained, the carbonising mechanism and carbon distribution in the charge are discussed. Below 724°C the carbon potential in the gas phase in the shaft furnace is far higher than that in the charge. Therefore, the charge is always in the process of carbonisation via the reaction 2CO = CO2 + C. The carbon content of the sponge iron increases rapidly in the lower zone of the shaft furnace above 724°C. The main reason for this is the deposition of coal tar in the gas. The influence of the hydrogen in the gas on the carbon content of the sponge iron is negligible.