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Utilisation of steel slags as neutralising agents in biooxidation of a refractory gold concentrate and their influence on the subsequent cyanidation

机译:钢渣作为中和剂在难处理金精矿的生物氧化中的应用及其对后续氰化的影响

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摘要

A study on the possibilities to utilise steel slag as neutralising agent in biooxidation of a refractory gold concentrate has been done with reference to commercial grade slaked lime. The idea has been to reduce the operating costs for neutralisation in the biooxidation plant, which is known to be the second largest operating cost. Other benefits would be savings in cost for landfilling of slag, possibilities to recycle elements present in the slag and savings of virgin limestone deposits. The slags used were an EAF slag and a slag from ladle refining; both originating from Swedish scrap based steel-making. Continuous biooxidation of the refractory gold concentrate was conducted in a single-stage 5 L reactor at a retention time of 56 h. The neutralisation capacity was determined by comparing the amount needed, per ton of feed concentrate added, to maintain the desired pH of 1.5 during steady state operation. Slaked lime had the highest neutralisation capacity with 110 kg/ton feed followed by ladle slag and EAF slag with values of 152 and 267 kg/ton feed, respectively. Sulphide mineral oxidation was similar and high in all cases although the ladle slag results were slightly better. Gold recoveries after cyanide leaching on the residues obtained were also similar and were in the range of 86-89%. However, the cyanide consumption expressed as kilogram cyanide per ton of concentrate fed to biooxidation, was double in the case of ladle slag and three times as much for the EAF slag compared to the slaked lime experiment. The increased cyanide consumption could not be explained only by the increased amount of elemental sulphur obtained in the slag experiments. The elemental sulphur formed had different reactivities as seen from the thiocyanate formation and cyanide losses due to thiocyanate formation were 16%, 32% and 40% for EAF slag, slaked lime and ladle slag, respectively. It is concluded that the ladle slag could be a possible replacement for limestone if they are mixed in proper proportions so that the microbial carbon dioxide demand is met whereas the EAF slag is less suitable due to the very fine reaction products obtained which gave operational problems with filtration and washing. To come further, experiments with the normal multi-stage biooxidation set-up with total retention time of 120 h should be performed which would increase the sulphur oxidation and eventually also reduce the cyanide consumption.
机译:参照商业级熟石灰,已经对利用钢渣作为中和剂进行难熔金精矿生物氧化的可能性进行了研究。想法是降低生物氧化工厂中和的操作成本,这被认为是第二大操作成本。其他好处包括节省填埋炉渣的成本,回收炉渣中存在的元素的可能性以及节省原始石灰石沉积物。所使用的炉渣是电弧炉炉渣和钢包精炼炉渣。两者均源自瑞典的废钢制造。难熔金精矿的连续生物氧化在5 L单级反应器中进行,保留时间为56 h。通过比较每吨添加的饲料浓缩物在稳态操作过程中维持所需pH值1.5所需的量来确定中和能力。熟石灰的中和能力最高,进料为110千克/吨,其次是钢包渣和电炉渣,进料分别为152和267千克/吨。尽管钢包渣的结果略好,但硫化物的矿物氧化在所有情况下都相似且较高。氰化物浸提后获得的残留物上的金回收率也相似,在86-89%的范围内。然而,与生石灰实验相比,钢包渣的氰化物消耗量为每吨精矿进行生物氧化时的氰化物公斤,是二倍,而EAF渣的氰化物消耗量为三倍。氰化物消耗的增加不能仅通过在炉渣实验中获得的元素硫的增加来解释。从硫氰酸盐的形成来看,形成的元素硫具有不同的反应性,EAF炉渣,熟石灰和钢包炉渣由于硫氰酸盐形成而导致的氰化物损失分别为16%,32%和40%。结论是,如果将钢包渣以适当的比例混合,从而可以满足微生物对二氧化碳的需求,则钢包渣可以替代石灰石,而电炉渣由于获得的非常精细的反应产物而不太适合,这给操作带来了问题。过滤和洗涤。更进一步,应该使用正常的多阶段生物氧化装置进行实验,总保留时间为120小时,这将增加硫的氧化作用并最终也减少氰化物的消耗。

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