El medio ambiente en la minería

EL MEDIO AMBIENTE EN LA MINERIA 96 process involves higher capital and operating costs than the us~al goethite and jarosite processes. ",<' . ::~~,. The hematite plant at R~hr-Zink in Datteln was brought into production in 1979. It was the decisive step in achieving a r~i9ue free ;hydr()metallurgical zinc extraction process and Ruhr-Zink was the ilist plant in the world to do it. , ',,-,', Figure 9- Simpli~ed Process Diagram of the Hematite ProéeSS , As a result of{urfherp:tocess development it háS recently becomerpossible to improve the hematite quality significantly. Tbe hematite of the second genera– tion will have a chemical composition of 65-67% Fe and less than 0.2% Zn. As a conclusion it can be stated that the hematite process gives modem industry a valuable solution to the iron problem of hydrometallurgical zinc production. Arsenic removal from washing acid Copper, zinc and lead ores contain arsenic in appreciable quantities. During smelting operation, highly volatile arsenic components arrive at the S02 gas treatment section and contaminate the washing acid as arsenic oxide (As203). Neutralization of washing acid with lime and disposal oC tbe relatively large quantities of gypsum containing calcium arsenate is now wid~ly accepted as . "urueasible because of ·Conversión of calcium arsenate to calclum carbonate 'under the influence ofatmospheric carbon dioxide, with subsequent redissolu– tion and mobilization of arsenate. Increasing sensibility of the public with regard to industrial activities cause environmental pressure on legislation in most industriali7..ed parts of theworld. Actual emissions in Germany for the non-ferrous industries are Jimited to 1 " mgINm 3 for gaseous components and to 0.1 mgll forwaterwhenJed to public P•. sewers. ',. TheSachtleben-Lurgi-Process reinoves arsenic and other métals frómwashing acid in the form .of ipsoluble sulphides and al10ws the purified acid to be used for standard sulphuric acid applications. The reactions take place in a stirred tank reactor. Figüre 10 shows a simplifiect Procéss Block Diagram. • - .•;' t .0:.. • Figure 10 - The Sachtleben:.Lurgi-Process for the removalof arsenic from washing acid. .. ,.- The extremely low solubilityofmetal sulphides is utilized to precipitate metals from aqueous solutions. The low pH ·value of washing acid allows for the precipitation of arsenic (As2S3), antimony (Sh2S3), tin (SnS), mercury (HgS), lead (PbS), bismuth (BilS3), copper (CuS) and cadmium (CdS) only, whereas nickel, cobalt, iron, manganese and zinc cannot be removed b.Y the process.