FE315 Finnish expert report on best available techniques in zinc production
Sigmund Fugleberg, 1999.
The Finnish Environment 315, p. 45. URN:ISBN 9521105054. The publication is available also in printed form (ISBN 952-11-0505-4).
Abstract
The aim of this BAT report is to identify available techniques for the reduction of emissions and energy use in the primary zinc production in Finland. The electrolytic zinc process used operates mostly on sulphide concentrates and comprises the following: roasting of the concentrate to calcine; mercury removal from the SO2 gas before acid production; precipitation of the iron as jarosite in the leaching of the calcine; production of cadmium by melt refining and a low contaminant copper cake for copper smelting in the purification; conventional electro winning and melting and casting of the zinc.
Precipitation of iron as jarosite is acid-consuming. The zinc, cadmium and copper containing weak acids from the copper and nickel smelters are utilised as reagents. The ability to utilise these acids reduces the total quantity of wastes in Finland compared to precipitation of a sulphate-free iron compound and neutralising of the acids with lime to give gypsum. The high stability of jarosite in acid media ensures high extraction from all raw materials, which saves natural resources. Liquid effluents from the process result from the cooling water system, the sulphuric acid plant and from the wet gas cleaning system. The main air emissions are SO2 and particulate emissions.
|