Benefits of recycling galvanized steel scrap for recovery of high-quality steel and zinc metal

摘要

Argonne National Laboratory (ANL) and Metal Recovery Industries, Inc. (MRII), in cost-sharing collaboration, have developed an electrolytic process to separate and recover steel and zinc from galvanized steel scrap. This work has been supported by the US DOE. An assessment of available dezinc technology was begun in 1987 which (1) screened process concepts for separating and recovering zinc and steel from galvanized ferrous scrap, (2) selected electrochemical stripping in hot caustic as the most promising process, (3) evaluated the technical and economic feasibility of the selected process on the basis of fundamental electrochemical studies, (4) experimentally verified the technical and economic feasibility of the process in a phased evaluation from bench-scale controlled experiments through batch tests of actual scrap up to six ton lots, and (5) concluded that the process has technical and economic merit and requires larger- scale evaluation in a continuous mode as the final phase of process development. This work has attracted worldwide interest. Preliminary economic analysis indicates that the cost of the recovered ferrous scrap would be about $150/ton (at a base cost of $110/ton for galvanized scrap), including credit for the co-product zinc. Concentrations of zinc, lead, cadmium and other coating constituents on loose scrap are reduced by a minimum of 98%, with zinc, in particular, reduced to below 0.1%. Removal efficiencies on baled scrap with bulk densities between 60 and 245 pounds per cubic foot range from 80 to 90%. About 1000 tons of galvanized scrap bales have been treated in batch operation at MRII in Hamilton, Ontario. A pilot plant for continuous treatment of 40 ton/day of loose scrap is being built by MRII in East Chicago, Indiana, with operation starting in early 1992. 9 refs.