THE RECOVERY OF NICKEL FROM HPAL LATERITE SOLUTIONS USING LIX~R84-INS AND SOME POSSIBLE IMPURITY CONTROL STRATEGIES

摘要

The recovery of nickel from laterite sourced ammoniacal leach solutions using the ketoxime, LIX~R84-INS, has been practiced by two Australian plants. One circuit used a HPAL-MHP route while the other uses a RRAL-^sSX route. Both plants have demonstrated the technical viability of this recovery route. While current sentiment seems to favour the intermediate product MHP route, the RRAL circuit operated by Queensland Nickel has been successful over 16 years of operation. Currently two nickel laterite projects under active consideration are evaluating the solvent extraction of nickel using LIX~R84-INS. One of these, the Vermelho project of Companhia Vale do Rio Doce, may use the HPAL-MHP route combined with so vent extraction and acid strip followed by electrowinning while the other, the BHP Billiton Ravensthorpe project, will use the HPAL-MHP solvent extraction-ammonia strip route. Operating plants using an aged circuit organic show significantly different solvent extraction characteristics from pilot circuits using fresh organic. These differences result from the degradation of the organic during operation. This degradation is associated with the extraction of cobalt (II) by the organic and the subsequent removal of this cobalt using a reductive strip. Plant operators have successfully overcome the operational issues associated with this degradation. Re-oximation of the organic plays an important role in maintaining the health of the circuit organic but cannot completely eliminate the need to add fresh oxime and diluent. Although the performance of aged circuit organic differs from that of fresh organic, it should be noted that both of the Australian LIX~R84-INS solvent extraction circuits were successfully designed using data obtained in pilot plants operating with fresh organic. Investigative work by Cognis, by project teams, and by plant operators over the past decade have significantly increased the nickel industries understanding of the technology involved in operating a LIX~R84-INS nickel solvent extraction circuit There are many potential circuits available for the recovery of nickel from latentes but the LIX~R84-INS based circuits have emerged as strong contenders for any new laterite nickel project. Current opinion seems to favor the MHP-ammonia leach-acid strip circuit but the ammonia strip analogue and possibly the RRAL-ASX circuit should also be evaluated for any new laterite project before a final decision is made.