Direct-to-blister smelting of copper sulfide concentrates in a dual-zone Vanyukov furnace: process parameters, slag chemistry, and reduction zone optimization

Abstract

The present study investigates the thermodynamic and technological parameters governing the direct-to-blister smelting of copper sulfide concentrates in a dual-zone Vanyukov furnace (PV furnace). Industrial slag and matte samples obtained from the Balkhash Copper Smelter (Kazakhmys Smelting LLP) were analysed using synchronous thermal analysis (STA 449 F3 Jupiter) to determine complete melting temperatures. Laboratory-scale smelting experiments were conducted to determine the compositions of blister copper and smelting-zone slags under controlled oxygen-blowing conditions. Process balance calculations were performed using dedicated software (PV-BALH) to quantify the effects of burden moisture, oxygen enrichment, specific oxygen consumption, and reductant loading on melt temperature, off-gas composition, and product quality. The complete melting temperatures of PV furnace slag and converter slag were determined to be 1172.1 °C and 1195.2 °C, respectively, confirming that the operative process temperature of 1300 °C provides an adequate superheat margin. Laboratory direct-smelting trials produced blister copper containing 94.2–96.3 wt.%. Cu at a process temperature of 1300 °C. The specific oxygen consumption required to transition from matte smelting (220 Nm³/t burden) to direct-to-blister operation (470 Nm³/t burden) was quantified. The optimal burden composition was established as: Cu ≥ 15 wt.%, S ≥ 30 wt.%, SiO₂ ≈ 15 wt.%, moisture ≤ 6 wt.%. The target slag composition after reduction-zone treatment should contain 28–32 wt.% SiO₂, Fe₃O₄ ≤ 8 wt.%, and Cu ≤ 0.7 wt.%. These findings provide, for the first time, a coherent dataset for the Vanyukov furnace operating in direct-to-blister mode, as no industrial plant currently uses this configuration.