DEVELOPMENT OF A NONEQUILIBRIUM STAGE MODEL FOR THE DESIGN AND SIMULATION OF GAS PROCESSING UNITS AND VERIFICATION WITH PLANT DATA (REACTIVE SEPARATIONS, SELECTIVE HYDROGEN SULFIDE REMOVAL)

A nonequilibrium stage model is developed for the design and simulation of Gas Treating Units. This model is based on the interphase mass and energy transfer rates, and there is no need to specify the efficiency of the stage or the component. Mass and energy transfer rates are determined by the extent to which the phases are not in equilibrium. It is a rigorous model and the effect of reaction on the degree of separation is determined by considering all the elementary reactions taking place in the system.; The approach is similar for both trayed and packed columns, and it uses real trays and packings. Detailed tray to tray profiles of compositions and temperatures are totally predicted without a prior fitting of anything to plant data. The model predicts such things as the exact location and magnitude of a temperature bulge in an absorber, making it possible to provide necessary interstage coolers at the right location, and the type and concentration of solvent to be used for treating a given gas stream at the minimum cost. It can also predict the experimentally observed phenomena such as the stripping of one component due to the absorption of a second component in the bottom sections of an absorber.; This model is applied to gas treating processes for removing CO(,2) and H(,2)S individually and in combination using aqueous alkanolamine solutions. The predictive powers of this model are illustrated by simulating pilot plants and full scale commercial units. The simulator predictions are compared to the plant results for the removal of CO(,2) from natural gas and synthesis gas using primary and secondary alkanolamines, and for the selective removal of H(,2)S from acid gas mixtures using primary and tertiary alkanolamines. The comparison is excellent for both the absorber and stripper columns, and it convincingly demonstrates the capabilities of the model. The same model can be extended with relative ease for gas treating using reactive solvents other than alkanolamines and a similar approach can be adopted to model other areas of reactive separation processes as well, like sour H(,2)O stripper and liquid-liquid extraction of LNG and LPG for the removal of acidic components.