Direct Reduction of Heavy Nonferrous Metals from Sulfide Compounds

Abstract

The results of long-term work of the group of authors on the problem of the direct reduction of heavy nonferrous metals directly from sulfide compounds contained in concentrates (lead) and metallurgical products (copper, nickel)—white matte and copper and nickel concentrates—from the separation of a converter matte are summarized. The preparation of materials for the reduction and the reduction process itself include the conversion of metal sulfides into oxygen compounds (oxidizing and sintering roasting) with the reduction of metals with carbon-containing reagents (coal and СО), as well as the reduction of copper and, partly, lead from oxide melts with sulfides. Sulfides conversion and reduction operations are associated with the release of sulfur- and carbon-containing compounds (SO₂, SO₃, CO, and CO₂) and, consequently, with the need to capture and utilize gaseous and solid products. A fundamentally new process of the direct reduction of metals from sulfides using their own sulfide sulfur as a reducing agent is proposed. The reducing process occurs through the possible formation of short-circuited electrode pairs in the 2Me^z+–zS^–2 system due to the donor–acceptor interactions, primarily π binding. The process can be successful occurrence upon the removal of the products (product) of the electrochemical reaction, in particular, S⁰. Caustic soda is proposed as a reagent. Using the example of the above production materials, the possibility of reducing the metals is shown at temperatures of 550–700°C with the achievement of their deep extraction (more than 99%). The product of sulfide sulfur oxidation, elemental sulfur, reacts with the melt of caustic soda and accumulates in the form of nonvolatile sodium compounds in it.