Roasting of ores

Fluidized bed reactors were first employed on a large scale for the catalytic cracking of petroleum fractions, but in recent years they have been employed for an increasingly large variety of reactions, both catalytic and non-catalytic. The catalytic reactions include the partial oxidation of naphthalene to phthalic anhydride and the formation of acrylonitrile from propylene, ammonia, and air. The noncatalytic applications include the roasting of ores and Tie fluorination of uranium oxide. 

Noncatalytic roasting of ores such as zinc and copper concentrates ... 

Burning of coal Roasting of ores Attack of solids by acids Gas-liquid absorption with reaction Reduction of iron ore to iron and steel... 

We listed many examples early in this chapter, and they can be quite different in practice, from the msting of iron to the toasting of dough to the roasting of ore. The reactant A could be a gas or a liquid, and the film could be a sohd or liquid. The migration of A through the reacted film could be diffusion of A dissolved in C or permeation of A through a porous film of C. We describe this by a diffusion coefficient D s, but the value of D/ s and the mechanism by which transport occurs will not be discussed here. 

Car] Friedrich Plattner, 1800-1858. Professor of metallurgy at the Freiberg School of Mines Author of books on blowpipe analysis and the roasting of ores. He was an expert analyst, trained under Heinrich Rose When his careful analysis of pollux was made in 1846, the spectroscope had not yet been invented, and he was unable to recognize the presence of the new element cesium... 

Ores of copper native copper, cuprite, chalcocite, chalcopyrite, malachite, azurite. Metallurgy of ores containing native copper, oxide and carbonate ores, sulfide ores. Gangue, flux, flotation, roasting of ores, matte, blister copper. Cupric compounds copper sulfate (blue vitriol, bluestone), Bordeaux mixture, cupric chloride, cupric bromide, cupric hydroxide. Test for cupric ion with Fehling s solution. Cuprous compounds cuprous chloride, cuprous bromide, cuprous iodide, cuprous oxide. Covalent-bond structure of cuprous compounds. 

Calcination/roasting of ores Bubbling/turbulent bed regime... 

Non-catalytic reactions involving two phases are common in the mineral industry. Reactions such as the roasting of ores or the oxidation of solids are carried out on a massive scale but the rates of these processes are often controlled by physical, not chemical, effects. Reactant or product diffusion is the main rate controlling factor in many cases. As a result, mechanisms of reaction become models of reaction with consideration of factors such as external diffusion film control or the shrinking core yielding the various models. Matters are further complicated by considerations regarding particle shape and external fluid flow regimes. 

The nonpetroleum applications of fluidization have been expanding rapidly with such processes being included as manufacture of phthalic anhydride by oxidation of naphthalene, calcining of limestone, roasting of ores, and production of high-purity metals by thermal decomposition of metallic salts. 

Heterogeneous Reaction of solids and liquids. Burning of coal. Roasting of ores. Gas-liquid absorption with reaction. Production of bio-mass Ammonia synthesis. Cracking of crude oil. Oxidation of sulphur dioxide. Gas-liquid absorption with reaction (often promoters added)... 

Calcination (e.g., of aluminium trihydrate and carbonates) Catalyst regeneration Roasting of ores... 

The feed gas composition of the SO2 conversion reactor depends on the source of SO2 (sulfur combustion or roasting of ores) and is typically in the range 7-12 vol.%... 

Examples The roasting of ores, the chemical adsorption of hydrogen sulfide by metal oxides (forming sulfides), the conversion of a metal oxide with a volatile non-metal oxide into a salt (e.g., the chemical adsorption of sulfur dioxide and oxygen by calcium oxide), the reductive chlorination of ilmenite (iron titanate) whereby iron chloride and titanium oxide are formed. In some processes a second solid reactant is present (e.g., carbon) that also reacts with the gaseous reactant, forming another gaseous reactant (e.g., carbon monoxide). 

A model has been formulated which follows the cyclical behaviour of the slugging fluidized bed and adequately incorporates mixing of the solids. The results for the steady-state agree with a previously formulated time-averaged model. The new mechanistic model provides a point of departure for stability studies and for the analysis of fluidized bed combustion and roasting of ores. 

The examples of such a system are frequently encountered in chemical and metallurgical processes, such as the reduction of metal oxides, the oxidation of metals, the roasting of ores, and the decomposition of metal compounds. The production of lime and the combustion of ashy coal are further examples. 

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