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, Na₂SO₄ precipitated and entered the system, which had negative influence on the matte converting process. The reaction behaviors of copper matte powder containing  Na₂SO₄ have been studied through thermodynamic calculation and single-particle experiments. Calculated results showed that a liquid sulfate phase, Na₂S containing copper matte, and Cu-Na alloy may form in the processing conditions of the converting process. The influence of the  Na₂SO₄ dosage, fluxing conditions, and processing temperature has been systematically studied, and the results obtained showed that: (1);  Na₂SO₄ physically precipitated on matte particles, and the Cu-Na alloy phase was found within copper phase in reacted particles; (2);  Na₂SO₄ 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 Na2SO4 amount; (3); CaO flux was able to promote the converting reactions and Na2SO4 transformation; (4);  Na₂SO₄ melt and formed a sulphate layer on matte particles at 1000 degrees C, Cu-Na alloy phase was found in samples collected at 1200 degrees C, and Cu-Na-O phase was detected in blister copper at 1600 degrees C.