Zinc removal from basic oxygen steelmaking (BOS) filter cake by sintering

Abstract

Zinc removal from basic oxygen steelmaking filter cake was studied by tablet testing and in a millipot under different conditions. The results from tablet testing show that coke and metallic iron in filter cake play the role of reductants to remove zinc during sintering. Zinc removal increased with increasing temperature and decreasing partial pressure of oxygen. Zinc removal reached 24.6% when a tablet of filter cake without addition of coke was sintered at 1300 °C in a nitrogen atmosphere. Addition of 3 to 9 wt% of coke breeze into filter cake enhanced the zinc removal to 60.6 to 91.4%, in an atmosphere with 0.5 vol% oxygen. The results from millipot sintering show that adding filter cake in the form of tablets was effective in removing zinc, especially when additional coke was added into the tableted filter cake. Zinc vapour generated at high temperature in the reducing atmosphere diffused out of the tablets and was carried with flowing gas, and then re-oxidized and deposited on the lower layer of sintering material in the bed. Positioning the filter cake in the form of tablets at the bottom of the sinter bed is therefore suggested as a possibility for zinc removal from filter cake.

Keywords: Mechanism of zinc removal; Millipot sintering; Recycling; Sinter plant; Steelmaking dust; Tablet testing.