H2 Reduction of Na2SO4 to Na2S Based on Dilute-Phase Fluidization

Abstract

Sodium sulfate (Na2SO4) is used in the ecofriendly production of sodium sulfide (Na2S) through H2 reduction, thereby facilitating the valorization of Na2SO4. However, studies on this technique remain at the laboratory stage. This paper proposes a novel process involving the external circulation of Na2S in a dilute-phase fluidized system to address the low-temperature eutectic formation between Na2S and Na2SO4 during the H2 reduction of Na2SO4 to Na2S. The process aims to increase the reaction temperature of the Na2SO4 while reducing the volume of the liquid phase formed to prevent sintering blockages and enhance the reduction rate. In a proprietary experimental setup, the H2 reduction process in a dilute-phase fluidized system was investigated. The Na2S/Na2SO4 ratio and reaction temperature were determined to be critical factors influencing the Na2SO4 reduction rate. The melting point of the system increased and the amount of liquid phase produced decreased as the Na2S content was increased to more than 60%. The Na2S–Na2SO4 mixture (mass ratio of 80:20) existed as a solid at the reaction temperature of 740 °C. After roasting for 10 s, the Na2SO4 reduction rate reached 93.7% and the Na2S content in the mixture increased to 98.74%.