Effect of desulfurization agent, temperature and roasting-reduction process time on high-pressure acid leaching (HPAL) nickel laterite residue

About 80% of nickel laterite ore's feed from high pressure acid leaching (HPAL) process becomes residue with Fe content of about 45% in the hematite compound makes this residue potentially reusable and not just thrown into dam or placement in a deep sea. The big challenge is to reduce the sulfur content by 5-6% of the residue so it can be used by the steel and industry. This study intends to examine the effect of adding desulfurizing agents (CaO, ZnO, and Na2CO3), temperature (600-900°C) and duration (15-120 minutes) of roasting-reduction to the reduction of sulfur content. The addition of a reducing agent using biomass charcoal with a fixed ratio of 10 wt.% and 10 wt.% desulfurizing agent is intended to change the residual compound from hematite to magnetite, the mixture is pelletizing manually. The desulfurization agent has the role of binding sulfur in the sulfate bond SO2-, either in the form of CaSO4, ZnSO4, or Na2SO4, so that the sulfur content in the magnetite product can be significantly reduced. Changes that occur during the process are observed and analyzed for roasting-reduction products using XRF, XRD. From this study can be concluded that to improve the quality, the longer the process will be better, but for the best combustion efficiency, within 30-60 minutes with the use of Na2CO3 agent is enough. At a temperature of 800-900°C for 30-60 minutes, the addition of Na2CO3 has a greater effect because the discovery peaks of Fe metal and wustite compounds because Boudoard reaction. The sulfur reduced from 6.183 to 1.5 wt.% with degree of reduction 65%.