Gas absorption process with chemical reaction by liquid solvents is widely used in the treatment of acid gases and gas purification. In this study, CO2 chemically absorption experiments by aqueous solution of sodium hydroxide (NaOH) have been done in a packed column with Raschig Ring packings. Results are used for determination of CO2 absorption rate and volumetric overall mass transfer coefficient (KGa). Generally, the volumetric overall mass transfer coefficient (KGa) for CO2-NaOH system is function of the process main operating parameters such as liquid volumetric flux, input gas phase mole fraction of CO2. Also, these experiments indicated that the overall mass transfer coefficient is enhanced by doubling of liquid volumetric flux and solvent concentration in average of 90% and 70%, respectively. Although, CO2 absorption rate is raised by increasing of liquid flow rate and solvent concentration (doubling of each of them), up to 67% and 65%, respectively

In this research, reactive absorption of hydrogen sulfide using diglycolamine solution in an industrial tray column was investigated. A nonequilibrium stage model has been developed based on dynamic film model for modeling of hydrogen sulfide reactive absorption into diglycolamine solution. In the model, simultaneous heat and mass transfer and reactions rate were considered. The model equations including partial and ordinary differential equations were solved numerically using the method of lines technique. The simulation results are presented in steady and unsteady state conditions. An industrial absorption column was employed to obtain the experimental data in both low and high pressure. The model results were evaluated using the steady state experimental data. A comparison of the experimental and simulation results showed that the average of correlation coefficient error for high pressure absorption process is 8.5 percent whereas the average of correlation coefficient error for low pressure absorption process is 7 percent.

In this research, the thermodynamics and mass transfer of CO2 absorption has been studied in a mixture of MDEA-MEA amines. A relation is presented for mass transfer flux in the reactive-absorption process. For this purpose, the effective parameters on the mass transfer flux were investigated in both liquid and gas phases. Then, using dimensional analysis with the Pi-Buckingham theorem, the effective variables were extracted as the dimensionless parameters. Also, the absorption process with MEA-MDEA is modeled according to four laws of chemical equilibrium, phase equilibrium, mass, and charge balance (considering the appropriate thermodynamic model for solvent). The experimental data of the previous research was used to calculate the dimensionless parameters. The constants of the mass flux equation are calculated with the fitting method. Also, the effects of operating parameters such as CO2 partial pressure, temperature, and dimensionless parameters such as the film parameter, enhancement factor, and loading have been investigated. The results showed that by increasing the loading and film parameter, the mass flux decreased, and the mean absolute error obtained from the proposed relationship was about 4. 3%, which indicates the high accuracy of the predicted equation.

Background and purpose: Human health is negatively affected by increase in concentration of carbon dioxide in indoor air due to the lack of proper ventilation. The aim of this study was to remove carbon dioxide from a closed space using sodium hydroxide nanofluid and determining the effect of absorbent concentration, carbon dioxide concentration, and titanium dioxide nanoparticles. Materials and methods: The experiments were conducted in a closed chamber on a laboratory scale. An air suction pump was connected to the absorption reactor and the carbon dioxide measuring device was installed inside the chamber. By injecting carbon dioxide gas inside the chamber, different concentrations in the range of 500, 2000 and 5000 ppm were created. Sodium hydroxide absorbent solution at 0. 1, 0. 2, and 0. 4% were examined. Titanium dioxide nanoparticles (0. 008%) and surfactant (0. 003%) were used to prepare nanofluids. The absorption fluids’ pH, electrical conductivity, and total inorganic carbon (TIC) were measured before and after carbon dioxide absorption. Results: By using 0. 4% sodium hydroxide solution containing 0. 008% titanium dioxide nanoparticles, the carbon dioxide removal efficiency at 500 and 5000 ppm were 72% and 44%, respectively, that were higher than the solution without nanoparticles (20% and 10%, respectively). At 5000 ppm carbon dioxide, increasing the concentration of absorption solution from 0. 1 to 0. 4% doubled the removal efficiency. The average amount of total inorganic carbon (TIC) in nanofluids increased by about 20% compared to the base fluids. The average reduction of EC in nanofluid was about 25% higher than the base fluid. The average reduction in pH value was less than one unit. Conclusion: Sodium hydroxide nanofluid containing 0. 008% of titanium dioxide nanoparticles is effective in removing carbon dioxide from the air.

In this research, the rate of CO2 absorption into methyl diethanolamine– piperazine (MDEA– PZ) solution was investigated. To model the mass transfer flux in the reactive absorption processes, the dimensionless parameters of the process were obtained using the Buckingham Pi theorem and considering the effective parameters in mass transfer. The CO2 mass transfer flux in the reactive absorption process depends on the mass transfer parameters of both the liquid and gas phases. Based on the dimensionless parameters obtained, a correlation is proposed to calculate the mass transfer flux of acidic gases in MDEA– PZ solutions. The mass transfer flux in the reactive absorption process is modeled based on the four laws of chemical equilibrium, phase equilibrium, mass balance, and charge balance. Experimental data from the literature were used to determine the constants of the derived correlation as a function of dimensionless parameters. In the provided correlation, the effects of dimensionless parameters including film parameter, CO2 loading, ratio of diffusion coefficients in the gas– liquid phase, CO2 partial to total pressure, and film thickness ratio as well as factors such as temperature, the number of free amines in the solution, the partial pressure of CO2, on the CO2 mass transfer flux were investigated. According to the results, the absorption rate decreases with increasing CO2 loading and film parameter, and the mean absolute deviation is about 3. 6%, which indicates the high accuracy of the correlation.

In this paper, a steady-state model based on mass transfer for selective absorption of hydrogen sulfide gas in MethylDiEthanolAmine (MDEA) solution, in the packed absorption tower is presented. This model is able to predict the concentration and temperature profiles in gas and liquid phases for the (MDEA-H2S-CO2H2O) system. In order to predict the profile of CO2 concentration, the second-order kinetic constants of reaction between gas and MDEA solution was used. Also, among the existing kinetic data, the best one was selected. In addition, the effective parameters in obtaining these profiles and the maximum point of selectivity factor were examined in this model. In order to evaluate accuracy of proposed model, the results were compared with from a pilot plant test as well as using operating data from absorption packed tower of the gas sweetening unit of phases 4 and 5 of South Pars Gas Complex. The obtained results reveal an acceptable compatibility between experimental data and prediction of the presented model.

In this work, reactive absorption of gases in aqueous electrolyte solutions has been investigated resulting in the development of a procedure in order to calculate the concentrations of ionic and molecular species in the liquid phase. Two duplicate experiments were conducted to investigate simultaneous reactive absorption of ammonia and carbon dioxide in partially carbonated ammonia solutions. The experiments were carried out employing an absorption pilot plant. The compositions of the electrolytes (ammonia and carbon dioxide groups) have been determined using principle knowledge of electrolyte solutions. The results revealed that the concentrations of ionic and molecular species in the liquid phase drastically influence the absorption rates of ammonia and carbon dioxide.