Patent ID: 7517383

Claim:
A method for recovering zinc from a zinc calcine and zinc suiphide concentrate in connection with an electrolytic precipitation of zinc in three stages in atmospheric conditions and at a temperature between 80° C. and the boiling point of the solution, whereby solids and solution move countercurrently in relation to each other and acid content of the leaching stages rises in the direction of the flow of the solids, the method comprising: a) feeding zinc calcine to a first neutral leaching stage, wherein the leaching in the first stage is carried out with a solution conducted from a second leaching stage, and wherein a zinc sulphate solution obtained from the first leaching stage is directed via solution purification to zinc electrolysis; b) feeding both zinc concentrate and solids obtained from the first leaching stage to the second concentrate leaching and jarosite precipitation stage, wherein iron contained in raw materials is precipitated as jarosite, and the concentrate leaching is carried out with a solution conducted from a third leaching stage, and wherein the acid content in the second stage is kept at about 2-20 g/L H 2 SO 4 ; c) feeding solids obtained from the second stage to a third leaching stage, wherein the solids obtained from the second stage comprise undissolved ferrites, a portion of the concentrate, and the precipitated jarosite, wherein the ferrites and the portion of the concentrate from the second stage are leached with electrolysis return acid, wherein the acid content in the third stage is kept at about 25-70 g/L H 2 SO 4 , and wherein the undissolved precipitate comprises jarosite.