Aproblem faced by the primary metal and glass industries is their intense energy usage. For example, the secondary aluminum processing industry uses about 1,000 Btu/lb of aluminum to remove oil, paint, plastics and other organics from the scrap. Another 3,000 Btu/lb is used in melting the scrap, for a total energy use of 4,000 Btu/lb. In addition, emissions and generation of waste materials are also industry problems. An innovative melter and dryer developed by Energy Research Co. (ERCo) demonstrated a capability to reduce energy use for the secondary aluminum industry. Scrap is first dried and/or decoated in a con-trolled-atmosphere, indirect-heated rotating kiln (IDEX) that completely removes organics. The heat content of the organics drives the process with little or no supplementary fuel required. Preheated scrap from the IDEX is then fed to the top of a vertical flotation melter (VFM) where it falls through a melting cone and into a holding furnace. The products of combustion (POC) flow up through the cone, counter-current and in direct contact with the scrap. The gases impose a variable drag force on the scrap, which impedes its descent. For most scrap pieces, equilibrium is achieved in which the scrap weight equals the gas drag force and the scrap is "hung-up" and does not fall for 15 to 30 seconds. This greatly increases the scrap residence time, allowing the scrap to be melted in the cone. As the scrap reaches a liquid state, it takes on a more aerodynamic drop shape, which reduces the drag force and allows it to fall into the holding furnace.
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