Method for preparing sodium carbonate and ammonium sulfate from sodium sulfate by thermal method

The invention provides a method for preparing sodium carbonate and ammonium sulfate from sodium sulfate by a thermal method, which comprises the following steps: (1) mixing sodium sulfate, a solvent, ammonium bicarbonate or mixed gas of ammonia gas and carbon dioxide, and carrying out double decomposition reaction to obtain sodium bicarbonate and double decomposition mother liquor; calcining the sodium bicarbonate to obtain sodium carbonate; (2) heating the double-decomposition mother liquor obtained in the step (1) to obtain ammonia gas, carbon dioxide and ammonium sulfate-rich mother liquor; the ammonia gas and the carbon dioxide are reused in the step (1); (3) carrying out evaporative crystallization on the ammonium sulfate-rich mother liquor obtained in the step (2) to obtain mixed salt, and carrying out particle grading on the mixed salt to obtain ammonium sulfate and sodium sulfate; the sodium sulfate is reused in the step (1). According to the method, high-valued sodium carbonate and ammonium sulfate p