1. Gold processing technology
Ø Oridinary gold ore
Cyanide leaching process is generally used for ordinary gold ore, which is featured with lower cost, high recovery, and wide adaptability to the ore. The main processe includes flotation, cyanidation, scrubbing, purification, displacement and refining. Representative projects include Laizhou Gold Smelter, Zhaoyuan Gold Mine, Xincheng Gold Mine, Phases I & II works of Sanshandao gold mine; representative projects with application of flotation and cyanidation-carbon-in-pulp process (CIP) include Hebei Yu'eryan Gold Mine and Jianchaling Gold Mine.
Ø Refractory gold
Refractory gold needs to be pretreated before cyanide leaching, which is aimed to have typical refractory gold ore oxidized to form porous feed and thus make easier contact between cyanide solution and gold ore. Processes for refractory gold treatment generally include roasting, bio-leaching and pressure oxidation (POX).
As for the roasting process, the sulfide wrapping gold is roast in one or two stages at high temperature to gold exposed. The process features less investment, simple operation, wide adaptability to feed and higher gold recovery. But as for the arsenic-bearing gold concentrate, gold recovery is reduced due to higher gold content in tailings. Representative projects include Zhaoyuan Gold Smelter Project, Zhongyuan Gold Smelter Project and gold project for Shandong Humon Smelting Co., Ltd.
Zhongyuan Gold Smelter
Bio-leaching refers to having sulfur, iron and arsenic contained in gold ores oxidized and decomposed into solution by bio-leaching to expose gold wrapped in sulfides. The process has advantages of low investment, high recovery of certain gold concentrate and less environmental pollution. Representative project includes Yantai Gold Smelter Project.
The basic principle of POX is to destroy sulfur and arsenic compounds wrapping the gold under high temperature, high pressure and aerobic conditions to expose gold, and achieving the purpose of improving gold recovery by cyanidation. The process has such advantages as rapid reaction speed, high adaptability, complete sulfide decomposition and high recovery of gold and silver; and compared with other processes, such process is characterized by high chemical stability with arsenic in gold concentrate existing in residue in the form of iron arsenate (FeAsO4·2H2O) after pretreatment by POX, which has smaller impact on environment. In addition, this process is suitable both for treating both concentrates and ROM ores. Representative projects include Guizhou Shuiyindong 500 t/a mixed ore modification project; Zhaojin Jinchiling Gold Mine 300 t/d gold concentrates project, which is under design currently.
2. Precious metal recovery technology
Ø Recovered precious metals will achieve 99.999% grade of gold, silver, platinum and other noble metals through chlorination, electrolytic refining technologies, such as Chengdu 540 plant (Great Wall Gold and Silver Refinery), Chengdu Tianze Noble Metals Plant.
Ø Recover noble metals from the catalyst. Xuzhou HOOTECH's secondary utilization project of noble metals has an annual processing capability of 9500t catalyst used in petrochemical industry, recovering platinum, rhodium, palladium, silver and other precious metals from catalysts, and the project was put into production in 2011.
3. Recovery of osmium, ruthenium, platinum, palladium, gold, rhodium, iridium from nickel anode slime
Ø In Jinchuan Group Co., Ltd, osmium, ruthenium, platinum, palladium, gold, rhodium, iridium are recovered from nickel anode slime through rectification and extraction.