Effects of Reducing Time on Metallization Degree of Carbothermic Reduction of Tall Pellets Bed

摘要

Recently, mere and more attention has been paid on alternative ironmaking processes due to the sustainable development. Aimed for the development of a new direct reduction technology, PSH process, the effects of reducing time on the metallization degree (MD) of carbothermic reduction of tall pellets bed at high temperature (1 500℃) are investigated at lab-scale in present work. The experimental results show, (1) In case of 50 min of reducing time, the MD of bottom layer DRI (Direct Reduced Iron) is lower, about 13%. MD of total pellets bed is about 58%. (2) In case of 60 min, the MD of bottom layer DRI increases to 63%. MD of total pellets bed increases to 80%. But for this case, the longer reducing time may result in some disadvantage, e.g. re-oxidation of top layer DRI, low efficiency of thermal energy, and low productivity. (3) Hot charge can obviously increase the metallization degree of DRI, especially for the bottom layers. In case of 50 min, compared with cold charge operation, the MD of bottom layer increases from 13% to 78%. Then the MD of total DRI bed increases from 58% to 85% by hot charge operation. Therefore, 50 min and hot charge are proposed based on the investigation in present work. These experimental results can give some theoretical references for the development of PSH process in future.