Experimental model validation of an integrated process for the removal of carbon dioxide from aqueous ammonia solutions

Abstract

In this work modelling and experimental validation of an integrated process for the removal of carbon dioxide from ammonia solutions – the so called decarbonisation – is presented. In this process, carbon dioxide and small amount of ammonia is stripped out from the solution at ambient pressure in a packed column. Recovery of the stripped ammonia can be reached by combining absorption of ammonia and condensation of stripping steam. The integration of stripping, absorption and direct-contact condensation (DCC) can be achieved in one compact unit in which stripping takes place in the lower part of the packed column, and the DCC and ammonia absorption in its upper part. This unit has been modelled in a rigorous way considering heat and mass transfer as well as reaction rates in multicomponent reactive stripping, absorption and direct-contact condensation in packed columns ( Maćkowiak et al., 2009). Extensive experimental investigations in a pilot scale packed column with diameters of 0.15 and 0.32 m have been performed for both, the stripping and for DCC. Relevant operation parameters as well as column dimensions were varied during the experiments in order to investigate their influence on the selectivity of the decarbonisation and to achieve a broad data base for the validation. Experimental validation of the two sub-processes and the entire decarbonisation shows good agreement between calculated and experimental values. Based on the validated model a successful optimisation of the decarbonisation process in industrial scale has been performed, leading to increased carbon dioxide removal and reduction of ammonia losses.