INVESTIGATION OF SODIUM SULFATE ADDITIONS INTO CRYOLITE-ALUMINA MELTS

摘要

In the Hall-Héroult process, sulfur impurities may not only emitrnharmful gases but also reduce current efficiency. To betterrnunderstand this process, the behaviour of sulfur compounds in arncryolite-alumina melt at 1253 K (980 ℃) was investigated in arnlaboratory cell. Sodium sulfate (Na_2SO_4) was added into thernmolten bath as a sulfur source. Furnace off-gases were passedrnthrough a mass spectrometer for qualitative assessment. Thernstability of sodium sulfate in the cryolite melt was found torndepend on the presence of carbon (t_(1/2) = 116 min) and carbonaluminiumrn(t_(1/2) = 29 min). It changed dramatically duringrnelectrolysis (t_(1/2) = 5-8 min). Detected sulfurous gases includedrnSO_2, COS, CS_2, and H2S.