Interfacial mass transfer and mass transfer coefficient in aqua ammonia packed bed absorber

A mathematical model was given to predict the mass transfer between flow of a mixture of ammonia vapor and water vapor and a flow of aqua ammonia solu tion at any interface within a packed bed absorber (PBA). The model used th e molal mass and heat transfer coefficients in both the liquid and gas phas es, the interface molal solution concentration, interface molal vapor mixtu re concentration, interface temperature, and the heat transfer coefficients in the Liquid and gas phases in both sides of the interface. The heat tran sfer coefficient was corrected to account for the mass transfer. The model was also used to derive a convenient mass transfer coefficient which was ba sed on the bulk mass concentration, not on the molal concentration, and not directly dependent on the concentration at the interface. To complete the model, mathematical correlations were derived for several thermodynamic and physical properties of aqua ammonia solution and vapor mixture. A computer program was developed to demonstrate the use of the model to predict the r ate of absorption of ammonia vapor at an interface within the packed bed at various operating conditions. (C) 1999 Published by Elsevier Science Ltd a nd IIR. All rights reserved.