3 Reactors - Reactors and Fluid Dynamics From mines to...

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1 Reactors and Fluid Dynamics From mines to metals • Mining – open-cast or underground • Concentrating – milling, flotation • Pyrometallurgy – drying, roasting, smelting, converting, condensing, granulation, atomizing • Hydrometallurgy – base-metals refining, precious-metals refining • Marketing and sales Pyrometallurgical processes • Pyrometallurgy involves high temperatures and the application of energy to materials • Are complex processes involving gas, solids, slag, and metal (and sometimes other phases as well, such as matte, speiss, bullion, doré, dross, etc.) • Thermodynamics – Collection of useful mathematical quantities that are measurable – Principle of energy conservation – Principle of increasing entropy • Kinetics – favoured (fast) at high temperature Natural state of iron? Process examples • Gas-solid reactions • Gas-liquid-liquid reactions • Phase separation (immiscible & different density) • Reduction MeO + C = Me + CO • Oxidation Me + ½ O 2 = MeO • Converting FeS + O 2 = FeO + SO 2 • How do you choose the type of reactor? Purpose of the reactor The main purpose of a pyrometallurgical reactor is to bring the reacting materials together under conditions where the chemical equations are favourable, to supply (or remove) the necessary energy, and finally to allow a separation of the product phases
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2 Fixed Bed • Solids remain in place, forming a porous burden • Fluid (typically gas) flows through the voids between particles Fluid in Fluid out Grate Grate Sintering Machine DUST HOOD Sinter WINDBOX IGNITION BOX Fuel Air Feed GRATE PALLET Off gas Shaft Furnace • Solids enter the top of the reactor and slowly descend as the process progresses • Gas flows counter- current to the solids, thereby providing efficient transfer of energy Fluid in Product out Fluid out Solids in 18 th Century Shaft Furnace A shaft furnace from the eighteenth century showing continuous charging at the top Iron Blast Furnace • The blast furnace has a tapered structure through which hot gas rises • The furnace is constructed as a shaft with the fire at the bottom, and the fuel and ore are added from the top Lead Blast Furnace • Tsumeb, Namibia
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3 Shaft Furnace for Copper • Asarco use a shaft furnace for melting copper • The shaft furnace is highly adaptable to meet the needs of different types of fuel including naphtha, natural gas, propane and butane. The furnace is also capable of switching from one gaseous fuel to another. ht p:/ www.asarcotechnologies.com/shaft_furnace.htm Fluidized Bed Reactor • Solid particles are lifted by the flowing gas • Particles “bubble and boil” and this promotes very good contact between solids and gas Fluidized Bed Reactor • Solids may be fed as a slurry (water can be added to control temperature) • A cyclone captures dust that is carried out of the reactor Fluidized Bed Reactor • Pyrite roaster, Ergo gold plant, Springs, South Africa • Externally heated, often to produce a metallic vapour • Combustion gas
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This note was uploaded on 05/13/2011 for the course METALLURGY 1133 at Murdoch.

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3 Reactors - Reactors and Fluid Dynamics From mines to...

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