TABLE OF CONTENTS Nickel is relatively small in tonnage, but unit price is relatively high and hence gross value is high It is used primarily in the manufacture of stainless steel (> 60%) with superalloys for gas turbines an important second use. Nickel often is a component of high chromium alloy foundry products notes for heat and wear resistance. Stainless is used extensively in the food and chemical industry and these are thus the primary source of recycle stainless steel. Superalloys are recycled by the gas turbine industry manufacturing industry or its customers the aircraft and electrical generation industries.
Cobalt is smaller than nickel in tonnage but is one of the highest priced of the common base metals. Used in superalloys and as a catalyst (with nickel, molybdenum and vanadium) in the food, chemical and petro-chemical.
Nickel and cobalt are recycled from alloy scrap and a variety of metallurgical dusts. Common grades of nickel scrap are derived from nickel silver clippings, nickel silver sheet, plate, pipe, rod, tubes, wire, screen, etc. Both pyrometallurgical and hydrometallurgical techniques have been applied.
In a process developed by the U.S. Bureau of Mines, the mixed scrap is converted to a matte containing 4 7 percent sulfur by adding sulfur directly to the molten metal. The matte is then granulated and ground to a minus 35-mesh particle size and leached with a solution of hydrochloric acid plus chlorine. This treatment leaches essentially all nickel, cobalt, chromium, iron, aluminum and...
