A modified Solvay process with low‐temperature calcination of NaHCO₃ using monoethanolamine: Solubility determination and thermodynamic modeling

Abstract

An energy‐saving, modified Solvay process for dense soda ash production was proposed to replace the high‐temperature, calcination step of NaHCO3. We found NaHCO3 completely decomposed into anhydrous, Na2CO3 at 353 K in a mixed‐solvent containing at least 65 wt% of monoethanolamine (MEA), which is an amine‐absorbent prevalently used for CO2 capture. A chemical model was built after the determination of solubilities and through data regression for the solid–liquid system: Na‐Cl‐NH4‐CO3‐HCO3‐MEA‐H2O. Reparameterization for paired‐ion interactions were performed via the mixed‐solvent electrolyte model. Thermodynamic analysis elucidated the shift in ion dominance from HCO3− to CO32+, thereby providing the phase transition mechanisms. An exploratory, fed‐batch experiment was implemented to verify the accuracy of the model, for which the obtained solids were in the form of saleable, dense soda ash products; bulk densities up to 1.01 g/cm3 were achieved in the laboratory.

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

“…In this paper, the dissolution method was used to determine the solubility of Na 2 SO 4 and (NH 4 ) 2 SO 4 salts in a mixed aqueous MEA solution at different temperatures and MEA concentration levels. The detailed procedure for solubility experiments has been described previously; , therefore, only a brief summary is described here. After adding the measured MEA solution into the jacketed reactors with magnetic stirring, the temperatures with a precision of ±0.1 °C were reassured by the water thermostat, although the water bath did indicate the temperature.…”

“…explored the effect of an amine and an organic solvent to facilitate the reaction of NaCl solutions with CO 2 to prepare sodium bicarbonate and hydrogen chloride. Ethylene glycol was added as an antisolvent to produce super dense soda and reached a remarkable bulk density of 1,550 kg/m 3 . − From all amine-compound groups, monoethanolamine (MEA) was found to be a great aid in CO 2 capturing. , Just recently, MEA was astonishingly found as a solvent media for the transformation of sodium bicarbonate to sodium carbonate, replacing the most costlier calcination step (290 °C) of the Solvay process. MEA is the least expensive water-miscible organic solvent and has shown great feasibility. , Also, the separation of the Na 2 SO 4 –(NH 4 ) 2 SO 4 –H 2 O system was studied by Cisternas et al They indicated that the double salts tend to form during low temperature and disappear at higher temperatures, yet there is still no resolution for the separation difficulty.…”

“…10−12 From all amine-compound groups, monoethanolamine (MEA) was found to be a great aid in CO 2 capturing. 13,14 Just recently, MEA was astonishingly found as a solvent media for the transformation of sodium bicarbonate to sodium carbonate, 15 replacing the most costlier calcination step (290 °C) of the Solvay process. MEA is the least expensive water-miscible organic solvent and has shown great feasibility.…”

Solubility and Modeling for NaHCO3 and NH4HCO3 Crystals in the System Na+–NH4+–SO42––Cl––H2O from 283.15 to 323.15 K

“…According to the “Mineral Commodity Summaries 2019” reported by the United States Geological Survey, the total worldwide production of soda ash was 55 million tons in 2018 . Conventional methods of producing soda ash are commonly known as the Solvay process and the Trona process, by which soda ash is either produced synthetically or mined directly . In other words, for regions in the world where the mining of trona demonstrates a low feasibility, the Solvay process must be in place for the manufacture of soda ash .…”

“…2 Conventional methods of producing soda ash are commonly known as the Solvay process and the Trona process, by which soda ash is either produced synthetically or mined directly. 3 In other words, for regions in the world where the mining of trona demonstrates a low feasibility, the Solvay process must be in place for the manufacture of soda ash. 4 For places where natural soda deposits are abundant, soda ash is produced with trona or sodium carbonate-rich brines through the Trona process, which compares favorably in terms of cost efficiency and environmental impact.…”