Mamoru Onoda

Pelletizing of nickel residue from laterite for direct reduction process

Abstract Pelletizing and reduction tests for direct reduction process using nickel leaching residue were carried out. Green pellet showed sufficient compressive strength and drop resistance for handling without addition of bentonite. The compressive strength of fired pellet was greatly increased when a small amount of limestone was added and the maximum strength was achieved at a CaO/SiO2 ratio of 0.2. Pellet with a compressive strength of 240 kg/pellet and a porosity of 30% was obtained by means of a pot-grate furnace at a firing temperature of 1220°C. When reduction tests were carried out by using non-coking coal as reductant, the highest degree of reduction (85.8%) was achieved at a reduction temperature of 1100°C.

Sponge iron production using petroleum coke by-produced in heavy oil thermal cracking

The KKI process is a new combination process to produce lighter oil from vacuum residual oil (VR) by thermal cracking and simultaneously to reduce iron ore to sponge iron with deposited carbon as reductant.VR is cracked thermally to lighter oil in a fluidized bed reactor with fine iron ore as fluidized medium. The cracked oil is withdrawn from the reactor for treatment to petroleum products in usual fashion.Iron ore is covered with by-product coke in the reactor. The iron ore covered with coke is withdrawn continuously from the reactor and subsequently reduced easily to sponge iron in the reduction furnace.Two types of reduction system are employed and these are selected in proportion to sulfur content in the VR. For low sulfur VR, a rotary kiln is used and for high sulfur VR, a fluidized bed reduction furnace is used.According to the results of experiments using pilot plants for thermal cracking, rotary kiln reduction and fluidized bed reduction, the yield of petroleum products was almost equal to that of conventional thermal cracking processes and sponge iron briquettes with reduction degree more than 92% was effectievely produced by rotary kiln. Even if a high sulfur VR was used, sponge iron with low sulfur less than 0.05% and reduction degree higher than 95% was obtained by fluidized bed reduction.