A thermodynamic model of nickel smelting and direct high-grade nickel matte smelting processes: Part I. Model developmen
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I. INTRODUCTION
MOST nickel-sulfide minerals are inevitably associated with copper and iron sulfides and are often associated with a minor amount of valuable metals such as cobalt and some detrimental impurities such as arsenic, antimony, and bismuth. Depending on their source, the concentrates usually contain nickel and copper in a mass-percent ratio between 1.5:1 and 15:1.[1] Since the distribution behaviors of minor elements between the matte, slag, and gas during the pyrometallurgical treatments of nickel-copper sulfide concentrates will affect the quality of the final products, the revenues gained from byproducts, and pollution control, a study of the distributions in a nickel smelting system is necessary to achieve desirable control of minor elements. There were two nickel flash-smelting methods (the INCO flash-smelting process and the Outokumpu flash-smelting process) in the nickel industry before 1994. They were developed by International Nickel Company (Sudbury, Canada) and Outokumpu Oy (Harjavalta, Finland), respectively. The chemistry of the two processes is similar: iron and sulfur are oxidized from the concentrates to produce a molten nickel-copper matte of a low matte grade. The low-grade mattes from the two types of flash furnaces are converted to high-grade matte (above 70 pct Ni ⫹ Cu in the matte) in Peirce–Smith converters. Because of the requirements of energy savings and of pollution control, many nickel smelters have recently considered the modification of existing operating conditions or the development of new processes with a view to a reduction of slag losses, a reduction of emissions of hazardous gases, product quality control, and energy savings in the face of a ¨ TZ, PENGFU TAN, Ph.D., Research Fellow, and DIETER NEUSCHU Professor, Dr. -Ing, are with the Institute of Theoretical Process Metallurgy, Aachen University of Technology (RWTH Aachen), Kopernikusstr. 16, D-52056 Aachen, Germany. Manuscript submitted March 17, 2000. METALLURGICAL AND MATERIALS TRANSACTIONS B
wide range of raw-material and scrap compositions. One new nickel pyrometallurgical process, Outokumpu direct high-grade nickel matte smelting, also termed the Outokumpu direct oxygen nickel (DON) process, has been developed.[2] It is one of the latest applications of the Outokumpu flash-smelting technology. The first DON smelter was started in 1995, in Harjavalta, Finland.[3] In the DON smelter, the nickel concentrate is smelted in one step into a highgrade nickel-copper matte without conventional converting. The new conditions and the new process lead to some significant changes of the minor-element distribution. An understanding of the behavior of the elements, in order to recover valuable metals such as Ni, Cu, and Co or to eliminate detrimental impurities such as As, Sb, and Bi, is presented here. II. PREVIOUS WORK Thermodynamic modeling was used to simulate copper smelting[4–13] and lead smelting[14] in a number of studies and proved to be very successful. One of the authors and a co-worker have also developed thermodyn
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