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A Turbulent contact absorber (TCA) column has been installed and operated at Petroleum University of Technology (PUT) to absorb CO2 using caustic solution. In order to survey column efficiency, calculation of mass transfer coefficients (kl, kg) and interfacial area (a) is necessary. Generally because of measurement problems, these parameters are expressed as overall mass transfer coefficient (Koga). CO2 absorption by aqueous solutions (such as caustic) is considered as chemical absorption which takes place in liquid boundary layer and the rate of absorption is a severe function of gas-liquid interfacial area. Through variation of system specifications such as caustic concentration, gas rate, liquid rate and liquid to gas ratio (L/G), which resulted from 70 practical experiments with various operating conditions, subordination of effective interfacial area was investigated; a direct predictive method based on chemical absorption was presented to calculate effective interfacial area; and best operating conditions for TCA column was concluded. The final results from practical experiments illustrated that, at low L/G ratios in absorption processes, using a TCA column whose cross sectional area and packing height is about 0.1 of same parameters in a packed column which operates at the same conditions, five times efficiency can be yielded.Index Terms-CO 2 absorption, Effective interfacial area, TCA, Three phase fluidized bed

In order to increase the life of the asphalt mixture and reduce the cost of the pavement life cycle, methods must be provided to improve the quality. Accordingly, the effects of aggregate surface coating with hydrophobic material in order to modify the aggregate mixture’s polar properties and reduce its hydrophilic properties are investigated. To this end, limestone and granite aggregates, 60-70 bitumen, and Two types of additives were used as the primary materials for the construction of asphalt mixtures. Thermodynamic concepts with cyclic loading have been used to evaluate the effects of these additives. The results obtained in this study indicate that the hydrophobic coating on the aggregate surface has increased the acidic components and decreased the alkaline components of the surface free energy for both types of aggregates. These changes will increase the bitumen-aggregate adhesion and make a better coating of bitumen on the aggregate surface. The results based on thermodynamic concepts suggest that the aggregate surface coating has reduced the system’s separation energy and the desire for stripping. The results of the dynamic modulus in wet to dry conditions also approve this outcome. The combination of thermodynamic concepts and the cyclic loading results show that the coating on the aggregate surface has reduced the aggregate’s stripping from bitumen. It is also obvious that the samples made with granite aggregates, which have acidic properties, are prone to moisture damage and have a higher tendency to strip.

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