CFD and statistical approach to optimize the average air velocity and air volume fraction in an inert-particles spouted-bed reactor (IPSBR) system

Inert-particles spouted bed reactor (IPSBR) is characterized by intense mixing generated by the circular motion of the inert particles. The operating parameters play an important role in the performance of the IPSBR system, and therefore, parameter optimization is critical for the design and scale-up of this gas-liquid contact system. Computational fluid dynamics (CFD) provides detailed modeling of the system hydrodynamics, enabling the determination of the operating conditions that optimize the performance of this contact system. The present work optimizes the main IPSBR operating parameters, which include a feed-gas velocity in the range 0.5-1.5 m/s, orifice diameter in the range 0.001-0.005 m, gas head in the range 0.15-0.35 m, mixing-particle diameter in the range 0.009-0.0225 m, and mixing-particle to reactor volume fraction in the range 2.0-10.0 vol % (which represents 0.01-0.1 kg of mixing particles loading). The effects of these parameters on the average air velocity and average air volume fraction in the upper, middle, and conical regions of the reactor were studied. The specific distance for each region has been measured from the orifice point to be 50 mm for the conical region, 350 mm for the middle region and 550 mm for the upper rejoin. The selected factors were optimized to obtain the minimum air velocity distribution (maximum gas residence time) and the maximum air volume fraction (maximum interfacial area concentration) because these conditions will increase the gas holdup, the gas-liquid contact area, and the mass transfer coefficient among phases. Response surface methodology (RSM) was used to determine the optimum operating conditions. The regression analysis showed an excellent fit of the experimental data to a second-order polynomial model. The interaction between the process variables was evaluated using the obtained three-dimensional surface plots. The analysis revealed that under the optimized parameters of a feed-gas velocity of 1.5 m/s, orifice diameter of 0.001 m, gas head of 0.164 m, mixing-particle diameter of 0.0225 m, and mixing-particle loading of 0.02 kg, the minimum average air velocity and highest air volume fraction were observed throughout the reactor.This work was supported by the ADNOC Refining Research Center , Abu Dhabi, UAE.Scopu

Effects of potassium hydroxide and aluminum oxide on the performance of a modified solvay process for CO2 capture: A comparative study

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 (Al2O3), on the pH level, CO2 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 CO2 uptake of 0.31 g CO2/g KOH. In comparison, about 0.92 g of CO2 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 CO2 capture and ions removal occurred with the Al2O3. 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 Al2O3 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.The authors are sincerely grateful to Dr. Hussain Awad, Emmanuel Galiwango, and Jawad Mustafa from Chemical and Petroleum Engineering Department at UAE University for their help.Scopu

Optimization of magnesium recovery from reject brine for reuse in desalination post-treatment

In this work, the recovery of magnesium from desalination reject brine through reaction with ammonia has been evaluated and statistically optimized using response surface methodology. The process is based on precipitation of magnesium hydroxide by the reaction of MgCO3 in the brine with ammonium hydroxide. A software, which is designed for studying chemical reaction and equilibrium, was employed to perform the thermodynamic analysis of the reaction of magnesium carbonate with ammonia, which was found to be exothermic and spontaneous in the temperature range of 0–22 °C. Central composite design (5-level, 3-factor) was used to optimize the process to obtain the maximum response of magnesium recovery as a function of reaction temperature, brine salinity, and ammonia to magnesium molar ratio. Maximum recovery of 99% was obtained at a temperature of 15 °C, brine salinity of 85 g/L, and a molar ratio of 4.4NH3: 1 Mg. The predicted response was in excellent agreement with the experimental results. The collected solid product at optimum conditions was characterized using X-ray Diffraction, Energy Dispersive Spectra analysis and thermogravimetric analysis. The analysis indicated the high purity of the recovered product in the form of Brucite (Mg(OH)2).The authors would like to acknowledge the financial support provided by Takreer Research Center . The authors would also like to thank Dr. Hussain Awad and Eng. Haliemeh Sweidan from The Chemical and Petroleum Engineering Department at the UAE University for their help.Scopu

Identification of early indicators of altered metabolism in normal development using a rodent model system

10.1242/dmm.031815DMM Disease Models and Mechanisms1133181