Phase Diagram for the Na₂SO₄–(NH₄)₂SO₄–MEA–H₂O System at Elevated Temperature

Abstract

sodium sulfate from ammonia sulfate-bearing liquor when sodium sulfate is used as raw material to produce sodium bicarbonate or even dense soda ash.

New Process for Na2CO3 Production from Na2SO4 Based on Modeling the Na2SO4–(NH4)2SO4–MEA–MEG–H2O System

“…We recently reported and modeled the phase equilibria for the system Na 2 SO 4 –(NH 4 ) 2 SO 4 –MEA–H 2 O . The solubility of sodium sulfate across the entire range of MEG concentration was investigated at temperatures from 25 to 100 °C and it sharply decreased with increasing MEG concentration due to the salting-out effect .…”

“…Yan and Chen reported the parameters for the (Na + SO 4 2– ):H 2 O pair and the parameters for the (NH 4 + SO 4 2– ):H 2 O pair are available in Aspen Properties version 8.8. The phase equilibrium data of the Na 2 SO 4 (s)–(NH 4 ) 2 SO 4 –H 2 O reported by Li et al were regressed to obtain the binary interaction parameters ( C, D, and E ) for the (Na + SO 4 2– ):(NH 4 + SO 4 2– ) pair, which are given in Table . The modeling results for the system are shown in Figure in which the calculated solid liquid equilibria are compared to experimental data, indicating very good agreement.…”

“…With the binary interaction parameters for the aqueous Na 2 SO 4 –(NH 4 ) 2 SO 4 system, we used the E-NRTL activity coefficient model embedded in Aspen Plus to model the system Na 2 SO 4 –MEA–H 2 O using the experimental solubility of solid Na 2 SO 4 in aqueous MEA solution at 353 K. The regressed solubility using the newly obtained E-NRTL parameters for the (Na + SO 4 2– ):MEA pair is compared with the experimental data in Figure a with good results (average mole fraction deviation is less than 0.015). Similarly, good results were obtained by modeling the solubility of (NH 4 ) 2 SO 4 in an aqueous MEA solution, as shown in Figure b.…”

“…In previous work, 15 8. Having fully identified the binary interaction parameters for modeling the solubility of Na 2 SO 4 and (NH 4 ) 2 SO 4 in the MEA−H 2 O and MEG−H 2 O systems, we now can use the model to predict the solubility of both salts in the mixed MEA− MEG solvent aqueous solution.…”

“…This is because the addition of ethylene glycol to Na 2 CO 3 solution deceases the transition temperature of the Na 2 CO 3 monohydrate to anhydrous transformation. Instead of MEG, Wang and Li found that NaHCO 3 can be completely transformed into Na 2 CO 3 at only 353 K in an aqueous solution containing at least 65 wt % of monoethanolamine (MEA) which is often used for CO 2 capture. , Our recently published study reported that the solubility of Na 2 SO 4 sharply decreases with increasing MEA concentration while the solubility of (NH 4 ) 2 SO 4 progressively increases. This finding hints at the possibility of using MEA to salt out Na 2 SO 4 in order to accomplish its separation from (NH 4 ) 2 SO 4 .…”