Effect of MgCl2 and pressure on vapor-liquid equilibrium in separation of water in water plus ethylene glycol system

In the process of preparing anhydrous magnesium chloride by the alcohol-ammonia method using ethylene glycol (EG) as the solvent, the dehydration process of the water + EG + magnesium chloride (MgCl2) system is crucial. Therefore, this work analyzed the effect of MgCl2 and pressure on vapor-liquid equilibrium in separation of water in water + ethylene glycol system. The isobaric vapor-liquid equilibrium (VLE) data for the water + EG + MgCl2 system were measured at 101.3 kPa with MgCl2 mass fractions of 0, 0.05, 0.07, and 0.10. It was found that the addition of MgCl2 raised the phase equilibrium temperature of the water + EG system and decreased the relative volatility of water relative to EG. Additionally, the VLE data for the water + EG + MgCl2 system at 71.3, 41.3 and 11.3 kPa were measured with the MgCl2 mass fraction of 0.10. The equilibrium temperature was effectively lowered, and the relative volatility was significantly increased by reducing the system pressure. The experimental data obtained in this work was consistent in thermodynamics test through Van Ness method. Moreover, the NRTL model was used to correlate experimental data. The root-mean-square deviations between the measured and calculated values of temperature (T) and vapor phase mole fraction (y1) were less than 0.53 K and 0.006 respectively. The NRTL model prediction with the regressed parameters was found in agreement with the experimental data.