Reactions of Magnesite Refractories with SO₃ Gas under Existing of Alkalisulfate

Abstract

Magnesite refractories reacted with SO₃ gas to form MgSO₄ as solid phase. When Na₂SO₄ existed, however, the MgSO₄ reacted with Na₂SO₄ to form liquid at above 670°C. Over the range of 670°C to 814°C, Na₂SO₄⋅3MgSO₄ crystallized from liquid with proceeding of the reaction, but at above 814°C, did not. As a result of formation of liquid, the amount of SO₃ picked up by the refractories increased particularly at 814°C to 1000°C and was maximum about 1000°C, but at above the temperature it decreased. Liquid formed by the reaction was transformed into Na₂SO₄⋅3MgSO₄ and MgSO₄ during cooling.
When K₂SO₄ existed, reaction of the refractories with SO₃ gas was similar to the reaction in the case of existing of Na₂SO₄. Over the range 884°C to 1000°C the amount of SO₃ picked up by the refractories was particularly increased and liquid formed by the reaction was transformed into K₂SO₄⋅2MgSO₄ and MgSO₄ during cooling.