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The present work evaluates and optimizes CO 2 absorption in a bubble column for the Pz-H 2 O−CO 2 system. We analyzed the impact of the different operating conditions on the hydrodynamic and mass-transfer performance. For the optimization of the process, variable conditions were used in the multivariate statistical method of response surface methodology. The central composite design is used to characterize the operating condition to fit the models by the least-squares method. The experimental data were fitted to quadratic equations using multiple regressions and analyzed using analysis of variance (ANOVA). An approved experiment was carried out to analyze the correctness of the optimization method, and a maximum CO 2 removal efficiency of 97.9%, an absorption rate of 3.12 g/min, an N CO 2 of 0.0164 mol/m 2 •s, and a CO 2 loading of 0.258 mol/mol were obtained under the optimized conditions. Our results suggest that Pz concentration, solution flow rate, CO 2 flow rate, and speed of stirrer were obtained to be 0.162 M, 0.502 l/h, 2.199 l/min, and 68.89 rpm, respectively, based on the optimal conditions. The p-value for all dependent variables was less than 0.05, and that points that all three models were remarkable. In addition, the experiment values acquired for the CO 2 capture were found to agree satisfactorily with the model values (R 2 = 0.944−0.999).

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Several well-known correlations such as the Bingham-plastic, power-law, and Herschel−Bulkley models have been used so far to determine the rheological parameters of drilling fluids. For some particular fluids, however, even a three-parameter model such as Herschel−Bulkley does not exhibit appropriate behavior. On the other hand, determination of the rheological parameters by numerical methods such as nonlinear regression may provide meaningless values, i.e. negative yield stresses. This is particularly notable in determination of yield stress, which identifies the capacity of the drilling fluid to carry the cuttings. In this work, a new equation has been developed which is capable of determining the rheological parameters and, more particularly, the yield stress of drilling fluids. It is demonstrated that the developed correlation improves the prediction of the rheological parameters of the fluids by including a logarithmic term. The velocity profiles and pressure drop values obtained for several drilling fluids in an annulus geometry exhibit the suitability of this novel equation in comparison with the previously mentioned equations.