Improving the Desulfurization Degree of High-Grade Nickel Matte via a Two-Step Oxidation Roasting Process
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INTRODUCTION
METALLIC nickel and the corresponding various products have attracted much attention because of their applications in many technological fields such as the new energy, iron and steel, military manufacturing, and electroplating industries.[1–7] Traditionally, nickel is mainly produced from pyrometallurgical processes.[8] Especially, sulfide raw materials are produced into nickel matte, which is further converted into high-grade nickel matte. Then, the high-grade nickel matte is transformed into crude nickel by oxidizing the blowing converting process and further processed hydrometallurgically into metallic nickel. However, with this process, it is hard to meet the demands for production of high value-added products and the comprehensive use of the mineral resources. Some technologies have been proposed to solve these problems, for instance,
ZHAO XI, ZHIXING WANG, XINHAI LI, HUAJUN GUO, and GUOCHUN YAN are with the School of Metallurgy and Environment, Central South University, Changsha 410083, P.R. China. JIEXI WANG is with the School of Metallurgy and Environment, Central South University and also with the Powder Metallurgy Research Institute, Central South University, Changsha, 410083, P.R. China. Contact email: [email protected] Manuscript submitted November 28, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS B
high-pressure sulfuric acid leaching,[9,10] chlorination leaching,[11,12] and ammonia leaching.[13–15] Among those, carbonyl processing techniques have drawn the greatest attention in recent years because products with high purity and special morphology can be obtained.[16] Jilin Jien Nickel Industry Co. Ltd. (China) developed the medium-pressure technology to produce carbonyl nickel from the calcine of high-grade nickel matte. However, the industrial production of the calcine also faces some problems such as the incomplete oxidation of high-grade nickel matte and the caking of calcine in the discharge hole of furnace. Previous studies on oxidation roasting of nickel sulfides mainly focused on nickel concentrates. Pandher and Utigard[17] studied the oxidation behaviors of the nickel concentrate and found that there was little mass change below 450 C and almost no SO2 was detected. Sulfides were suggested to transform into sulfates at the temperatures ranging from 450 C to 700 C, leading to an increase in the sample mass. Moreover, the produced sulfates would decompose above 700 C, causing a sharp mass decrease. Yu et al.[18] studied the oxidation roasting of nickel sulfide concentrate in a fluidized bed roaster between 650 C and 775 C. They found that the oxidation of nickel/cobalt sulfides was very slow, even when the roasting temperature was high enough. Another work by Yu and Utigard[19] studied the oxidation mechanism of nickel concentrate in air from
ambient temperature up to 1000 C. The results indicated that Ni1xS would transform into NiO and NiSO4 and the decomposition of NiSO4 would take place at 942 C. To the best of our knowledge, there is little work reporting the oxi
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