Reaction Behavior of Na2SO4-Containing Copper Matte Powders in a Simulated Flash Converting Process

Sodium sulfate accumulation in the water system is a common problem in the production of primary metals from sulfide minerals. In flash smelting-flash converting copper smelters, when molten copper matte quenched in industrial water to produce matte granules, Na 2 SO 4 precipitated and entered the system, which had negative influence on the matte converting process. The reaction behaviors of copper matte powder containing Na 2 SO 4 have been studied through thermodynamic calculation and single-particle experiments. Calculated results showed that a liquid sulfate phase, Na 2 S containing copper matte, and Cu–Na alloy may form in the processing conditions of the converting process. The influence of the Na 2 SO 4 dosage, fluxing conditions, and processing temperature has been systematically studied, and the results obtained showed that: (1); Na 2 SO 4 physically precipitated on matte particles, and the Cu–Na alloy phase was found within copper phase in reacted particles; (2); Na 2 SO 4 contamination hindered oxygen transfer by forming a low melting sulfate phase, and the de-sulfuration rate of matte powder changed dramatically along with the variation in Na 2 SO 4 amount; (3); CaO flux was able to promote the converting reactions and Na 2 SO 4 transformation; (4); Na 2 SO 4 melt and formed a sulphate layer on matte particles at 1000 °C, Cu–Na alloy phase was found in samples collected at 1200 °C, and Cu–Na–O phase was detected in blister copper at 1600 °C.