Removing chlorine of CuCl residue from zinc hydrometallurgy by microwave roasting

LU Shuai-dan(卢帅丹)^{1, 2, 3}, XIA Yi(夏仡)¹, HUANG Chang-yuan(黄昌元)⁴, WU Guo-qin(吴国钦)⁴, PENG Jin-hui(彭金辉)^{1, 2, 3}, JU Shao-hua(巨少华)^{1, 2, 3}, ZHANG Li-bo(张利波)^{1, 2, 3}

(1. National Local Joint Engineering Laboratory of Engineering Applications of
Microwave Energy and Equipment Technology, Kunming 650093, China;
2. Key Laboratory of Unconventional Metallurgy of Ministry of Education
(Kunming University of Science and Technology), Kunming 650093, China;
3. Faculty of Metallurgical and Energy Engineering,
Kunming University of Science and Technology, Kunming 650093, China;
4. Mengzi Metallurgy Co. Ltd., Honghe 661400, China)

Abstract:Most Zn hydrometallurgy factories adopt Cu₂SO₄ as a dechlorination reagent from zinc solution nowadays, thus much CuCl residue is produced. The existing process of treating this residue is washing with water or sodium carbonate solution, which would cause a lot of troubles to water treatment and waste discharge. A method of microwave roasting was adopted for dechlorination of CuCl residue. A 1.5 kW microwave roasting equipment with dust collection and tail gas adsorption systems was set up and applied during the experiment. By investigating the effect of temperature, heat preservation time, moisture content of raw material and grain size of samples on the dechlorination, the optimal experimental condition is obtained. When the samples with 2% moisture and <150 μm grain size are microwave roasted at 400 °C for 2 h, the Cl content turns from 14.27% to 1.35% and the dechlorination rate is as high as 90%, while that with conventional heating is only 60%-80%. The phase change of the roasting process investigated with X-ray diffraction verifies that CuCl in CuCl residue is removed by being transformed into CuO.

Key words:microwave roasting; zinc hydrometallurgy; dechlorination; CuCl residue