El medio ambiente en la minería

95 ANGELSELKE standard technology has been considered in order to show the impact on the sulphuric aeíd plant on the overall energy system. Figure 6 - Energy Block Diagram for a 100.000 tpy Cu-smelter based in flash furnace and PS converters. The aeíd plant of a copper srnelter is a service unit to improve the environ– mental situation and to recover a byproduet. If therefore should never in– fluence the availability of the smelter. The situation is similarwith any energy recovery system both in the smelter and the aeid planto Energy recovery rnay improve tbe overall economics and represents a complementary aspect in establishing the processing concepto Figure 7 - Energy Bart Chart for a 100.000 tpy Cu-srnelter based on flash furnace and PS-converters. Energy recovery is possibJe in the smelter from waste heat utilization and in aeíd plants from excess heat generated by S02fS03-conversion and absorp– tion/formation of sulphurie aeíd. The energy has been used to produce ami/or superheat steam, hot gas and hot water for heating and process purposes. The steamean be transformed to electric energy,whenever price andlor availability of power justify it. Residue treatment in the zinc industry based on the hematite process One of today's major targets in the classical rosting-Ieach-electrowinning of zinc is without any doubt the removal of iron from the zinc sulphate solution without the production ofwaste residues. Even with sophisticated leaching and residue treatment processes such as jarosite or goethite a final residue is produced. This residue still contains sorne heavy metals and therefore it has to be stored in special ponds. Although jarosite and goetbite are insoluble chemical compounds their environmental stability as waste materials is not yet know. Figure 8 shows a comparison of varioos residues treatment processes. Hematite is the most important mineral rawmaterial for primary iron produc– tion. The chemical formation ofthis material has not yet produced a sufficient– Iy clean concentrate. The product is therefore al present sold to the cement indostry. Nevertheless this is of course a great advance in comparison to dumping of the conventional iron residue in the foem of jarosile or goethite. The hematite process was developed al approximately the same time in the 1970's in Akita Zinc Co. Ltd. and inDatteln by Ruhr-Zink GmbH. The reason for this step Was principally ecol~ogical bul it also make possible almost 100% recovery of the main metal zinc, lead and silver and avoid dumping. But the