Aluminum Casting: R&D Trends
Tapping Molten Aluminum for casting from a tilting barrel furnace.
Courtesy of Can Eng Manufacturing, Ltd.
Equipment
Combustion Technology
Energy Consumption
Process Description
R&D Trends
The majority of recent R&D has been focused on increasing the efficiency of the aluminum melting process and reducing NOx emissions from aluminum melters. Other industry efforts have been focused on improving the recycling of foundry sand through thermal reclamation.
HRS Combustion System
Nippon Furnace Kogyo Ltd., has developed an advanced regenerative burner system which is capable of preheating combustion air to 1800°F. A pair of High Cycle Regenerative (HRS) burners alternate operation at 30 seconds each. At furnace temperatures close to 2300°F, less than 100 ppm NOx (at 0% 02) can be maintained due to the “unique two stage combustion technology.” Energy savings from 30-60% are reported.
FDI Regenerative System
The Fuel Direct Injection Regenerative (FDI) System is an energy saving, low emissions burner system developed by Tokyo Gas CO., Ltd., and currently being marketed by North American Burner. The heat from the flue gas is captured in alternating regenerators to achieve air pre-heat temperatures over 1800°F. NOx levels below 100 ppm (at 11% 02) can be achieved.
PYRETRON Combustor
American Combustion, Inc. has developed a new burner which is designed to increase convective heat transfer to scrap and decrease NOx and CO emissions. The burner is designed to increase aluminum and brass scrap reclamation. NOx emissions are reported to be about 0.05 lbs./MMBtu.
Immersion Heater Furnace
Immersion Heater Furnaces heat the metal bath from the interior. These furnaces have been used for zinc baths at temperatures below 450°C but until recently could not withstand the aluminum bath conditions. Burners capable of operating over 24 hours a day for 90 days have been developed by four European gas companies and were demonstrated at Montupet foundry outside Paris.
Thermal Sand Reclamation
Until recently, thermal reclamation of foundry sand has been considered viable only for specialized recovery of materials such as zircon where the cost of the raw material excluded the possibility of immediate disposal. Increasing cost of sand disposal has made thermal reclamation economically feasible. Nearly 80% of foundry sand can be reclaimed utilizing mechanical attrition units. The remaining 20% must either be disposed, or thermally reclaimed. Thermal reclamation units use either a fluidized bed or infrared heat source to process the sand. These systems can be significant to natural gas uses, and will be utilized in greater numbers as disposal costs continue to rise.