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1、NEW NICKEL PROCESS INCREASING PRODUCTION AT OUTOKUMPU HARJAVALTA METALS OY,FINLAND TABLE OF CONTENTS1.0 Introduction 22.0 Nickel Smelter 33.0 Nicke! Refinery 54.0 Conclusions 18 Presented atALTA 1997 Nickel/Cobalt Pressure Leaching & HydrometallurgyForum, May 19-20,1997,Perth Ausffalia1.0 INTRODUCTI
2、ON Outokumpu Oy has produced nickel at Harjavalta Works in Finland since 1960. The production has been based on flash smelting technology and electrowinning of nickel. The capacity of the process has been increased gradually to 18000 tpa by several small expansions and process improvements. The prod
3、uction relied on domestic nickel concentrates until thaAt the turn of the 1990s a new nickel strategy was developed and Outokumpu started nickel exploration in Austraiia and Canada. The work secured long term delivery contracts of nickel concentrates from Mt. Keith and starting of mining operations
4、at Forrestania and Silver Swan in Australia.At the same time Outokumpu studied different alteratives to expand the nickel and copper production. n 1993, a decision was made to invest in the expansion and modernisation of Harjavalta operations. Outokumpu decided to increase nickel production from 180
5、00 tpa to 32000 tpa and blister copper production from 100000 tpa to 160000 tpa. The copper refinery in Pori was expanded from 72000 tpa to 125000 tpa. In addition, the expansion included a new oxygen plant, two hydrogen plants and a new sulphuric acid plant. The construction startad in 1993 and the
6、 Harjavalta project was completed in 1996. During the construction the nickel production was decided to increase further to 40000 tpa . The realised capital expenditure of the whole expansion project of Harjavalta was FIM 1600 million ($US370 million) .The expansion of the nickel production has mean
7、t several process changes in tha nickel smelter and refinery . The decision to invest in nickel was preceded by research and development work at Outokumpu Harjavalta Matals Oy and at Outokumpu Rasaarch Oy . The investigation program led to the following improvements of the process: Development of di
8、rect Outokumpu Nickel Smelting (DON) Process.Leaching process for high iron nickel matteUtilization of Outokumpu-developed and designed reactors for atmospheric and pressure leaching.Utilization of Outokumpu-developed solvent extraction process in the nickel/cobalt separationUtilization of the Sherr
9、itt process for hydrogen reduction of nickal and cobalt.Sulphur outlet as ammonium sulphateThe process improvements were incorporated in the existing nickel flash smelter,matte refinery and electrowinning procaiss. The capacity of the nickel refinery is 18000 tpa nickel cathodes and 22000 tpa brique
10、ttes. 2.0 NICKEL SMELTER In tha 1980s Outokumpu started to develop a converterless direct smelting process to praduce a high grade nickel matte for further refining. The process was tested on a pilot scale at Outokumpu Research Oy in Pori and found to be viable . The benefits of this process were in
11、 a simplified flowsheet and high grade S02 gas flow to the acid plant. The process was named the direct Outokumpu Nickel Smelting Process or DON Process /1-3/. At tum of 1990s Outokumpu continued the development work on the DON Process based on a feed with high nickel and magnesia content and low ir
12、on content. As a result of this work the DON Prccess was further developed to produce two mattes: Low iron matte in the flash smalting fumace (FSF) to be leachad in the existing leaching circuit of Harjavalta. High iron matte in the electric furnace (EF) to be Ieached in a new EF matte leaching circ
13、uit.By producing two mattes it was possible to eliminate the converters which has meant a simple process with low investment, maintenance and operating costs. In addition, it is now possibla to smelt concentrates with a high magnesium content. The ferric residue from the EF matte leaching is added t
14、o the smelting charge to increase the iron to magnesium ratio and to reduce smelting temperature of the slag. Futher, the cobalt recovery of the DON Pracess is higher than in the conventional smelting process. In Harjavaltas case, it was essential that the process could use the existing flash furnac
15、e and electricfurnace as well as the existing leaching plant. Figure l shows the flowsheet of the DON Process at Harjavalta nickel smelter. The primary feed of the nickel smelter is a blend of various concentrates. Also nickel containing secondary materials are used as a feed. In addition to the flue dust from the waste heat boiler and the electrostatic precipitator, the iron precipitate from the EF matte leaching is circulated back to the flash furnace. This makes it possible to convert leach residue to disposable fayalite slag. Concentrates
