Abstract: Blast furnace gas containing dust particles has the coarsest particles removed and the result wet scrubbed before being fed to a treatment apparatus for separating the remaining coarse dust, which has a low lead and zinc concentration. The gas dust is fed to a separator in the form of a thickener where coarse particles are removed through an outlet while the remaining gas dust is fed to a settling basin. This concentrates the dust particles before they are fed via pipe to a second separator having two hydrocyclones. Here the coarse particles are removed via pipe. The coarse particles from the outlet and pipe are suitable for feeding to a blast furnace as they are low in lead and zinc. The presence of the settling basin gives a more distinct separation if the dust particles by the hydrocyclones and the hydrocyclones can operate more efficiently.

Abstract: Zinc and lead are separated together out of dust derived from a gas-cleaning installation in iron or steel making by a flotation-separation treatment. In order economically to provide a good separation of these metals and to leave a residue which is re-usable in an ore-preparation process in the iron and steel industry, the flotation-separation treatment is at a pH of 7 to 9 and is effective to achieve a separation, according to size of the dust particles, of a floated component in which the zinc and lead are concentrated and a non-floated component which is suitable for re-use.