Effects of potassium hydroxide and aluminum oxide on the performance of a modified solvay process for CO ₂ capture: A comparative study

Abstract

In a previous work, the overall performance of modified Solvay process was investigated in the absence of ammonia, where carbon dioxide and brine treatments were accomplished in a single reaction and in the presence of calcium hydroxide (Ca(OH) 2 ). In this study, the impact of alkaline and amphoteric oxides, namely potassium hydroxide (KOH) and aluminum oxide (Al 2 O 3 ), on the pH level, CO 2 capture capacity, ions reduction, and type of produced solids was investigated at a temperature of 20 C and a gas flow rate of 1 L/min. At the stoichiometric ratio and less than the solubility limit, the KOH/brine mixture achieved a CO 2 uptake of 0.31 g CO 2 /g KOH. In comparison, about 0.92 g of CO 2 was captured by 1 g of CaO when CaO was added to the brine in an amount that was more than the solubility limit but less than the stoichiometric ratio. Moreover, the percentage of the ions reduction for the KOH and CaO was almost the same except for the sulfate ions, as the best removal was for the CaO. The poorest CO 2 capture and ions removal occurred with the Al 2 O 3 . X-ray diffraction was used to identify most of the solid products, and the obtained results proved that KOH is a promising alkaline for the combined process. In addition, potassium chloride crystals were produced when KOH was utilized, which is a very valuable product, and it can also be easily separated. Although Al 2 O 3 showed no reactivity, it revealed good results in terms of magnesium ions recovery and could be considered as a coagulant for recovering magnesium ions in the reject brine solution.

KOH-Based Modified Solvay Process for Removing Na Ions from High Salinity Reject Brine at High Temperatures

“…In this research, all experiments were conducted in a novel inert-particle spouted bed reactor (IPSBR) developed by El-Nass et al [17,18]. Figure 1 shows a schematic diagram of the reactor [9]. The inert particles were composed of poly(methyl methacrylate) with an average density and diameter of 1020 kg/m 3 and 0.013 m, respectively.…”

“…mass of CO 2 reacted (g) mass of KOH used (g) (5) Figure 1. A schematic diagram of the inert-particle spouted bed reactor system (IPSBR) [9].…”

“…Recently, Mourad et al [9] investigated the effectiveness of potassium hydroxide (KOH) in the Solvay process. KOH was selected owing to its potential in directly capturing CO 2 from ambient air [10][11][12][13][14][15].…”

“…KOH was selected owing to its potential in directly capturing CO 2 from ambient air [10][11][12][13][14][15]. The overall reaction of the modified Solvay process based on KOH as the alkaline material can be described using Equation (3) [9]. NaCl + CO 2 + KOH ↔ NaHCO 3 + KCl (∆G 20 C = −130.6 kJ/kmol) (3) This process was studied under the same optimized conditions of temperature, pressure, and gas flowrate previously reported by El-Naas et al [4], where CaO was used as the alkaline material instead of NH 3 .…”

“…The CO 2 uptake and Na + removal reached up to 0.31 g CO2/g KOH and 29%, respectively, at a temperature, pressure, gas flowrate, and KOH concentration of 20 • C, 1 atm, 1 L/min, and 70.57 g/L, respectively. Moreover, the main products formed in this reaction, such as NaHCO 3 and potassium chloride (KCl), have various industrial applications [9].…”