POST COMBUSTION BEHAVIOR IN IN-BATH TYPE SMELTING REDUCTION FURNACE

In order to make a research on a new smelting reduction process, the iron bath based Smelting Reduction Furnace (SRF) with 5-ton iron bath capacity was installed in 1986 at NKK's Fukuyama Works and these test facilities were stepwisely built up. In this paper, post combustion behavior in the SRF is described, based on the integrated operations with the SRF directly connected to the Pre-reduction Furnace (PRF). Essential conditions to achieve high post combustion coupled with high heat transfer efficiency are summarized as follows; 1) Height adjustment of a top blowing lance according to the change of slag surface level, permitting post combustion within slag which is considered to be a major heat transfer medium, 2) Intensive agitation of slag phase by bottom blowing of gas, 3) Ultra soft blowing of oxygen through a double flow lance, and 4) Pressurized operation in which the depression of carry-over of charged coal is attainable. Under these conditions, longterm continuous operations over 10 h were stably carried out at high level of post combustion of 50% with heat transfer efficiency of more than 85% even in the use of high volatile coals. In the tests using various carbonaceous materials such as coke, medium volatile coal and high volatile coals, effects of volatile matter on post combustion were investigated. Furthermore, modelling of post combustion was studied to optimize the operating conditions in a larger scale furnace.