Production of Sodium Bicarbonate with Saline Brine and CO2 Co-Utilization: Comparing Modified Solvay Approaches

The present work investigates the production of sodium bicarbonate in combination with the co-utilization of saline brine and carbon capture, utilization, and sequestration (CCUS). The use of ammonia in the traditional Solvay process could be eliminated by using a modified Solvay process. This study compared the modification with the addition of three buffering additives: Ca(OH)2, KOH, and NH4HCO3. The effectiveness of these processes, using two qualities of saline brine (desalination and aquifer), is compared based on the purity of the produced NaHCO3. It was found that the use of Ca(OH)2 did not produce high-purity NaHCO3, while NH4HCO3 and KOH performed better. Desalination brine utilization with NH4HCO3 resulted in the production of high-purity NaHCO3, while the second most suitable method involved the use of KOH, and the main co-product formed was Na2CO3. Geochemical modeling is performed in order to have insights into the carbonation (in the reactor) and precipitation (in the oven) behavior of the reactions. It predicted the precipitation of mineral phases well, though kinetics might hinder some saturated solids to dissolve first. The present study shows that accurate characterization is critical to accurately assess the success of modified Solvay processes. The use of QXRD and SEM analyses, complemented with geochemical modeling, helped to better understand the processes and the formation of NaHCO3. Further investigations on diverse brines could provide for their better utilization by the geological carbon sequestration and water desalination industries that produce them.