This non ferrous metal requires specific heating applications at each step of the process.
rule-of-thumb you may apply 4.6-7 MJ/kg (2000-3000 BTU/lb) to obtain the heat necessary to
melt a load at a temperature of approx. 680oC with the pouring temperature higher at
The major factors that will effect this figure include the type of insulation (light weight ceramic insulation materials are generally more efficient than fire bricks) and the burner type.
To obtain the rapid combustion necessary in a small combustion space, or to melt larger loads, a forced draft type burner is generally used.
The most economical is the pre-mix package using a variety of configurations and controls. Multiple furnaces can be fed from a single air supply cutting costs even further. Sealed nozzle mix burners are quiet, efficient and have a wide operating range. Package burners are compact however back heat may be a problem.
This stage is not always used in the process but as the metal is already at a high temperature and there are losses only through the refractory and the flue, the smaller holding furnace can be fired with a simple atmospheric torch type burner. The gas input rate is approx. 1 MJ/kg (500 BTU/lb).
If direct temperature control is desired a special ceramic type probe sheath is necessary to withstand the corrosive effects of the aluminium. Economical digital electronic control is used to modulate the burner according to demand.
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