چكيده به لاتين
Chemical absorption technology is widely used in the industry to remove carbon dioxide after combustion. To develop this method, it is necessary to develop and identify optimal absorbents in order to absorb more and reduce energy absorption. The aqueous solutions of alkali metal hydroxides are of interest to researchers due to the need for low energy and their compatibility with the environment, which has the advantages of these absorbents in comparison with aqueous alkanoamine solutions. In this study, due to the high potential of these absorbents, carbon dioxide absorption has been studied using both aqueous sodium hydroxide and potassium hydroxide in laboratory and theory. The absorption experiments, designed with the RSM and CCD design software, were designed in a batch reactor at a temperature of 25-65°C, a pressure of 2-6 bar and The concentration of 0.31-1.21 mol/lit. Loading and absorption percentage of carbon dioxide were in aqueous solution of sodium hydroxide in the range of 0.45-0.98 and 11.47%-72.93% and in aqueous solution of potassium hydroxide in the range of 0.49-1.06 and 12.85%-74.99% respectively. RSM has been used to analyze the results of experiment with using second-order quadratic polynomial model. Also, numerical optimization for each solvent has been performed to find the maximum amount of loading and the percentage of carbon dioxide absorption under optimum conditions. These values for sodium hydroxide solution were estimated respectively 0.79% and 27.2%, and 0.88% and 28.8% for the potassium hydroxide solvent. By comparing the performance of two absorbents, the loading and absorption percentage of potassium hydroxide in most points were slightly higher than the sodium hydroxide. In order to find the concentration of components in the liquid bulk during absorption, a thermodynamic modeling was performed with the Pitzer model that nonlinear equations of equilibrium chemical reaction, charge and mass balance simultaneously with the Newton-Raphson method in MATLAB software has been solved. The results are similar to those presented in previous studies. By adding phase equilibrium equations, the concentration of water and carbon dioxide was calculated at the instant of equilibrium. Also, the amount of carbon dioxide loading was calculated and it was compared with its experimental value. The relative error in the modeling points for both solvents was obtained in the range of 11-24%, and it was found that the relative error in the loadings 1 and 1.5, is below the 10%.
