The Article below will appear in the GIFA show issue of The Cast Metal Times and will be distributed at the exhibition. Written by Dr. Christopher Hall, Director of Monometer.
TIN, LEAD AND COPPER SMELTING AND RECYCLING WITH MONOMETER ROTARY FURNACES
Monometer rotary furnaces for the reclamation of tin and lead have been in particularly high demand recently, following a significant rise in commodity prices over the past few years, in particular for tin dross processing, for which up to 99.5% of the metal-bearing material in a charge can be recovered as recycled tin. The smelting process is attractively simple and does not involve salt, so the environmental impact of final waste products is low and will typically pass for low cost disposal routes.
A chrome-magnesite brick ensures long refractory life between lining changes of up to three years, while its high thermal conductivity effects good thermal efficiency by continually passing heat to the charge material as the furnace rotates. The furnace rotation effects a homogeneous heat distribution and reactivity in the charge bed, so the process consumes relatively little reductant, slag volumes are low, and the recovery cycle time is short. For example, the Monometer continuous smelting process operating in a one-tonne capacity furnace will produce up to five tonnes in an eight-hour shift, while the larger of our furnaces at 40 tonnes capacity will typically cycle 80 to 100 tonnes of material over eight to ten hours.
Monometer rotary furnaces are made in the UK to the highest standards of machining and fabrication to ensure reliable alignment of all drive train and furnace rotating components; and all welding, including the integration of spun dished ends, is checked to ASME and/or ISO certification. Following these standards furnace quality is guaranteed, and indeed proven by the many installations worldwide now having achieved in excess of 25 years continuous operation.
The Monometer smelting system extends to accommodate ores of lead, copper and tin, and has been applied in the reclamation of silver from charges of various mixed material. In each of these applications the unique bath depth and rotational programme retain metal fume within the reactive bed of the furnace chamber and effect a rapid cycle and high yield; recoveries of up to 99.5% are quoted in all offers where exhaust dusts are returned to the furnace and this performance is guaranteed subject only to a certified charge assay.
Both low NOx air-fuel and oxy-fuel burner technology are offered with Monometer deep bath smelting furnaces. This is in consideration for the varying needs of diverse processes and client circumstances. In particular, the attractions of the oxygen burner can include a lowering of emissions volumes by up to 75% with an accompanying reduction in the required size of filtration plant, cycle time reduction by up to 40% and reduced metal losses. However, these attractions are attainable for many, but not all processes. For example, a smaller and therefore less costly filtration plant requirement, (which can offset higher oxy-fuel capital costs), is typically only realised where emission volume is reduced by at least 50%, and cycle time is not always influenced significantly by flame temperature alone. This is why Monometer air-fuel systems, having been developed to maximise the heat recovery attainable from vortex recirculation (double pass) principles, remain a highly attractive option for all processes, particularly for tin and lead smelting, and are effective and economical in situations where the necessary oxygen supply is not always available locally at the site of installation.
Monometer offers a fully comprehensive service from design for special applications through to commissioning and continuous assistance after installation. A typical installation will be commissioned and proven by one of our metallurgical engineers to operate to the standards and performance quoted, and our after sales service will attend at short notice regarding any process-related requirements or other furnace needs.
For these reasons Monometer is particularly well placed with the necessary combination of experience backed up by continual development and the highest qualify of manufacture and service, to provide a reliable high performance solution for the client every time.
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