ABSTRACT
The removal of acid gases, such as CO2 and H2S, from natural, refinery and synthesis gas streams by absorption using different solvents is a significant operation in gas processing. Another important application of absorption-based technologies is CO2 separation from flue gases in many industries – such as fossil-fuel power plants, steel and cement production. According to the Intergovernmental Panel on Climate Change (IPCC), carbon dioxide is recognized as a major manmade greenhouse gas contributing to global warming. The problem of CO2 increasing emissions has led to international commitment to regulate the CO2 emissions by all developed countries. The idea of carbon dioxide sequestration, which includes its capture and storage in underground rock formations, has progressed steadily over the past 10 years. It is claimed that this solution could play an important role in solving the problem of increasing greenhouse gas emissions.The physical or chemical absorption of CO2 are generally recognized as the most efficient CO2 separation technologies at present. The most commonly used physical solvents are methanol at low temperatures (Rectisol, Lurgi GmbH), propylene carbonate (Fluor-Solvent), N-methyl-2-pyrrolidone (Purisol, Lurgi GmbH) and dimethyl ether of polyethylene glycol (Selexol, Norton Chem) (Kohl & Nielsen 1997). The common feature of these processes is that they are used in absorber-stripper mode, requiring two separate steps in CO2 separation. This technology is known as a pressure swing absorption process, in which low pressure is used to desorb CO2 and to regenerate the solvent. Although, in many practical situations, the operational and capital costs of the desorption column may be greater than the costs of the absorption column,
studies devoted to desorption are not as numerous as those concerning absorption and there is little information in the literature on the design aspects of desorption columns. The problem of predicting the desorption rates arises when the process is accompanied by bubble nucleation in the liquid bulk. This phenomenon completely changes the hydrodynamic conditions in the liquid phase and the diffusive mass transfer equations cannot describe the process rate in terms of analogues to absorption.
