Rotary Furnace Smelting

Two broad types of rotary furnace are used - the rotary kiln and the short rotary furnace. Rotary kilns are characterised by large length to diameter ratios of the order of 10 to 15 1, whereas for the short rotary furnace the length to diameter ratio rarely exceeds 1.5 1. 

For the smelting of battery pastes the reactions given by Equations 11.7 to 11.14 take place  

The gas phase mainly contains CO and CO2, but some SO2 can be present due to limited reaction according to Equation 11.14 - the roast reaction  

It should be noted that CO2 generated from sodium carbonate will react according to Equation 11.8 and thns will lead to increased fuel consumption. For this reason and because of the cost of soda ash, the balance between the addition of iron and soda ash should favour a greater proportion of iron. 

A high FeS content in the matte tends to increase the lead content and reduce lead recovery to bullion by reducing the reaction given by Equation 11.11. The equilibrium constant (k) for Equation 11.11 is given by Equation 11.15  

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Indonesia and Singapore use slow-speed rotary furnaces. Both Malaysia and Thailand have added new electric-furnace smelting capacity in order to improve smelting efficiencies. Reverberatory and rotary furnaces are also used in Indonesia. On the other hand, the smelters in Central Africa, including those in Zaire and Rwanda as well as those in South Africa, which are far away from coal sources, use electric furnaces because of the availabiUty of electric power. 

Newer secondary recovery plants use lead paste desulfurization to reduce sulfur dioxide emissions and waste sludge generation during smelting. Battery paste containing lead sulfate and lead oxide is desulfurized with soda ash to produce market-grade sodium sulfate solution. The desulfurized paste is processed in a reverberatory furnace. The lead carbonate product may then be treated in a short rotary furnace. The battery grids and posts are processed separately in a rotary smelter. 

This air-oxy/fuel burner concept was first tried in 1989 at a Canadian aluminum dross reclamation plant where drosses and skimmings are smelted.2 The dross, with 10% salt, is charged through the burner end of a 25,000 lb (11,000 kg) rotary furnace, fired by a dual-fuel burner of 20 x 106 Btu/h (6 MW) capacity for melting. The... 

Lead rotary furnaces are used either for melting battery scrap or smelting concentrates. Oxy/fuel technology was introduced about 20 years ago in lead scrap-melting furnaces. Most of the lead rotary furnaces have been converted to oxy/fuel in Europe. The benefits of oxy/fuel burners in secondary plants include up to 100% production increases energy savings of up to 60% lower CO, C02, and NOx 85% lower combustion products 50% lower furnace off-gas and up to 60% lower particulate emissions. 

Simplistic operation. No complex equipment is needed in the operation of a plant. The rotary furnace requires little maintenance compared with other smelting operations. 

This technique can be applied on any rotary furnace and in the preheating of pouring ladles. Oxybumers do not find implementation in non-ferrous foundries, although they are used e.g. in secondary copper smelting. 

Smelting Updraught Sinter Machine / Blast Furnace Updraught Sin Machine / Blast Furnace Updraught Sinter Machine / Imperial Smelting Furnace QSL-Process Short Rotary Furnace Sinter Machine / Blast Furnace Dross Rovorberatory... 

Treatment of Cu ross Reverberatny Furnace Rotary Furnace Meltina to Matte Recycle te Smelting Furnace Screened, Conditioned and Sold te Union Minere... 

The number of primary and secondary smelters within a given size range is illustrated in Figure 1.7, which shows the significant difference in numbers and in plant capacities. The scale of these plants also has an impact on the technologies used for secondary smelting in comparison with primary smelting, and the most common approach is the use of the short rotary furnace. 

Secondary lead smelting is predominantly based on the treatment of scrap lead-acid batteries, as detailed in Chapter 10. A wide range of smelting methods are used for the treatment of secondary lead, originally based on traditional smelting methods such as the hearth and blast furnace, feeding whole batteries, but are changing under stricter environmental controls to the use of prior separation and specialised reduction in rotary furnaces or newer electrochemical techniques. 

Process Rotary furnace Imperial smelting furnace/ISF Electric arc furnace/ EAF/steel Electric arc furnace/ E AE/ferromanganese Converter steel furnace/ ferromanganese Oxy reducer... 

Primary smelting can be carried out in a reverberatory, rotary, or electric furnace. The choice depends more on economic circumstances than on technical considerations (3). Thus, in the Far East, reverberatory furnaces fired with anthracite coal as the reductant were and still are widely used. 

H2S04 leaching Smelting in rotary kiln-electric furnace... 

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