Method and device for treating anode slime
The method and furnace according to the invention enable a continuous processing of anode slime and are particularly suited to be connected to a process where anode slime is treated by hydrometallurgic methods after roasting. In the method according to the invention, the slime containing valuable metals and selenium is dried, roasted, sulfatized and cooled. The method includes steps to be carried out in succession, in continuous operation, so that the slime forms a slime layer on the conveyor and is conveyed to be treated in successive drying, roasting, sulfatizing and sulfuric acid removal and cooling units.
1. A method for treating slime containing valuable metals and selenium, in which method the slime is dried, roasted, sulfatized and cooled, wherein the method includes steps to be carried out in succession and in continuous operation, so that the slime is formed as a slime layer on the conveyor and is conveyed to be treated in succession to successive drying, roasting, sulfatizing and sulfuric acid removal and cooling units.
2. A method according to claim 1 , wherein the thickness of the slime layer is under 35 mm.
3. A method according to claim 2 , wherein the thickness of the slime layer is 10-20 mm.
4. A method according to claim 1 , wherein in the drying unit, the slime layer is heated up to 100° C., and the removal of moisture from the slime layer is boosted by a fan.
5. A method according to claim 1 , wherein in the roasting unit, the temperature of the slime layer is raised up to the range 350-550° C., and that the material transfer in the slime layer is boosted by a fan.
6. A method according to claim 1 , wherein in the sulfatizing and sulfuric acid removal unit, the temperature of the slime layer is set within the range 250-350° C., and the employed sulfatizing reagent is sulfuric acid.
7. A furnace for treating slime containing valuable metals and selenium in continuous operation, in which furnace the slime is roasted for removing the selenium and for sulfatizing the metals, wherein the furnace comprises a drying block, a roasting block, a sulfatizing and sulfuric acid removal block and a cooling block, arranged in succession, at least one conveyor that is arranged to convey the slime layer through the blocks from the beginning of the drying block to the end of the cooling block, and a slime feeder device, that is arranged to feed anode slime at a suitable speed to the moving conveyor band.
8. A furnace according to claim 7 , wherein there are two or more conveyors arranged in succession.
9. A furnace according to claim 7 , wherein the feeder device can be arranged to form an anode slime layer with a thickness of 35 mm or thinner onto the slime conveyor.
10. A furnace according to claim 7 , wherein in the drying block, in the roasting block and in the sulfatizing and sulfuric acid removal block, above the conveyor, there is in each block arranged a heater and a fan above the heater.
11. A furnace according to claim 7 , wherein the cooling block is provided with at least one cooling element for cooling the slime layer.