High efficiency system for melting molten aluminum

A recirculating method for heating or melting solid aluminum in molten aluminum, the method including the steps of:

• (a) circulating molten aluminum from a reservoir through at least one of a pumping bay, a heating bay, an aluminum metal charging bay and a treatment bay back to said reservoir;
• and
• (b) heating said molten aluminum in said heating bay with an electric heater providing heat to said molten aluminum at a watt density of 20 to 350 watts/in.sup.2, said heater comprised of a composite material having an inner layer of metal having a coefficient of thermal expansion less than 10.times.10.sup.-6 in/in/.degree.F. and having an outer surface having a refractory coating thereon exposed to said molten aluminum and resistant to attack by said molten aluminum, said refractory coating having a coefficient of thermal expansion less than 10.times.10.sup.-6 in/in/.degree.F.

A recirculating method for heating or melting solid aluminum in molten aluminum, the method including the steps of:

• (a) circulating molten aluminum from a reservoir through a pumping bay, a heating bay, an aluminum metal charging bay and a treatment bay back to said reservoir;
• and
• (b) heating said molten aluminum in said heating bay with an electric heater providing heat to said molten aluminum at a watt density of 30 to 200 watts/in.sup.2, said heater comprised of a composite material having an inner layer of metal of titanium or titanium alloy having a coefficient of thermal expansion less than 5.times.10.sup.-6 in/in/.degree.F. and having an outer surface having a refractory coating thereon exposed to said molten aluminum and resistant to attack by said molten aluminum, said refractory coating selected from the group consisting of one of Al.sub.2 O.sub.3, ZrO.sub.2, Y.sub.2 O.sub.3 stabilized ZrO.sub.2, and Al.sub.2 O.sub.3 --TiO.sub.2 having a coefficient of thermal expansion less than 5.times.10.sup.-6 in/in/.degree.F.