Vacuum balance and related studies of carbons used in zinc-lead production

Abstract

The reduction of metal oxide to metal is an essential step in the extractive metallurgy of zinc and lead. The performance of metallurgical cokes in this reaction is governed by inter alia, their reactivity. In this research the reactivity of selected carbons, including some metallurgical cokes, is investigated as follows. The surface and solid state properties of the materials are examined by vacuum microbalance and microscopic techniques. Their oxidation is studied by thermogravimetry and differential thermal analysis. The extent of reaction is correlated with reaction conditions, for example, temperature and time of oxidation, flow rate and surrounding atmosphere, and particle size, porosity and crystallinity of the carbons. The nitrogen adsorption isotherms of the carbons were recorded at −196°C on a CI Mark II microbalance, specific surface areas were calculated by the BET method. The oxidations were carried out on a Stanton-Redcroft mass flow balance, model MF-H5; the TG and DTA curves were recorded simultaneously on the same sample. The crystallinity and particle size were characterised by scanning and transmission electron microscopy (Jeol SEM35 and Philips EM300 electron microscopes). Results are presented for a selection of charcoals, graphites and cokes.