Phase equilibrium of Na2SO4-NH3-CO2-H2O system in preparation of sodium bicarbonate from sodium sulfate
It is of great significance to master the phase equilibrium law of Na2SO4-NH3-CO2-H2O system to optimize the process of preparing sodium bicarbonate with high utilization of sodium sulfate.In this paper,the liquid-solid equilibrium relationship of Na2SO4-NH3-CO2-H2O system and its sub-system Na2SO4-NH3-H2O was studied by isothermal solution equilibrium method at 303.15K,323.15K and 343.15K at 101.3-1099.0kPa.The equilibrium law of SO42-,CO32- and HCO3- in the Na2SO4-NH3-CO2-H2O system and the Na2SO4-NH3-CO2-H2O system were obtained.The results showed that ammonia in the Na2SO4-NH3-H2O system had a strong salt-out effect on sodium sulfate.Under the action of ammonia,the equilibrium solid phase of the system existed in the form of anhydrous sodium sulfate when the temperature was lower than 305.55K.At the same time,the solution of sodium sulfate ammonia salt water could promote the dissolution of sodium sulfate by carbonation of carbon dioxide.Low temperature and high pressure could promote the carbonation of sodium sulfate ammonia brine solution and improve the conversion of sodium sulfate to sodium bicarbonate.
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