OIT Issues U.S. Casting Industry Profile.

The U.S. Dept. of Energy's Office of Industrial Technologies (OIT) has released a report titled "Energy and Environmental Profile of the U.S. Metalcasting Industry," which presents benchmark energy use and environmental data for the industry as a whole and at the process level for each of the industry's major unit operations.

In addition to supplying the most current estimates of energy use for each major industry process, the report summarizes inputs/outputs for these processes and characterizes air emissions, effluents and wastes generated by these processes. The profile was developed in support of OIT's "Industries of the Future" strategy for promoting energy efficiency. Processes covered include molding, coremaking, lost foam casting and diecasting.

Findings reported by the profile include:

* energy used in the molding department of a typical sand casting foundry is between 7-20% of the foundry's total energy consumption;

* approximately 50% of the total energy used in iron foundries with cupolas is consumed in the furnaces. Traditional cupolas have thermal efficiencies of 40-50%, with inefficiencies due to incomplete combustion of coke and deficient heat exchange in the cupola stack. Cupola modifications that can increase energy efficiency include the use of preheated blast air (hot blast) and oxygen-enriched blast or incorporating recuperative heating to utilize the combustion potential of off-gas;

* wet scrubbers and baghouses are the most commonly used devices for removing particulate from cupola exhaust gas, and typical efficiencies for removing particulates in baghouses exceeds 99%, with scrubbers and afterburners removing 95%;

* preheating systems in electric arc melting operations provide the advantages of dryers and significant energy savings in the furnace. Gas-fired preheaters have thermal efficiencies of 60%, which is lower than furnace efficiency, however the use of relatively inexpensive gas reduces net operating costs;

* 20% more energy is required to new virgin gray iron in coreless induction furnaces than iron scrap. Coreless furnaces have electrical efficiencies from 76-81%, and induction furnaces operated in tandem can achieve a maximum electric power utilization exceeding 80%. About 75% of the energy delivered to the furnace is used for increasing the temperature of the metal, with the water-cooling system being the major source of energy loss (typically 20-30%);

* cleaning and finishing account for an estimated 7% of energy use, or approximately 1 million Btu/ton of good castings shipped;

* typical energy consumption during sand reclamation is 150 kW/ton using electric equipment. The preferred system in U.S. foundries is a combination of calcining in a thermal unit followed by processing in a simple pneumatic scrubber;

* lost foam casting can reduce energy consumption by 27% when compared to green sand or resin-bonded sand processes;

* typically, 5 million Btu/hr of natural gas is required per ton of metal die castings. Requirements for electric resistance die heating are 4 million Btu/ton of metal.