a dust rich in zinc that is recovered in adapters equipped with condensers (extractors) during the production of zinc in horizontal retorts. The term “blue powder” also refers to the dust trapped in scrubbers; scrubbers are used to purify the gases of vertical retorts during zinc production.
Blue powder represents 2–5 percent of the zinc charged into a retort. The particle size of blue powder is less than 100 microns. Blue powder contains 85-95 percent Zn, 1.5-2.5 percent Pb, 2-6 percent C, 0.5-2 percent Cd, and 2-2.5 percent other impurities. It is sometimes rich in cadmium and may act as a raw material in the recovery of cadmium.
Blue powder with the highest degree of purity is used in the cementation (precipitation) of such metals as gold, silver, copper, cadmium, and indium, and also in the chemical industry. Impure blue powder is either processed separately to recover zinc and cadmium (the residue is returned into the initial charge of a retort) or fed directly into an initial charge.