Process design physical/chemical solvent processes

In contrast to these generic tools, the second group of domain-specific software tools addresses certain tasks during the design process in the chemical engineering domain. They can roughly be classified as data retrieval, synthesis, and analysis tools. A typical example for data retrieval tools are physical property systems [1048, 1053[. Synthesis tools include flowsheet synthesis [951, 1039], plant layout and pipe routing [955], model development ]54, 558] or even solvent selection [7.37]. The most prominent examples of analysis tools are process simulators for steady-state ]518, 556, 1046] and dynamic simulation ]288, 518, 916]. 

Physico-chemical solvents are in certain respects superior also to purely physical COS absorbents. In the case of methanol, for instance, Henry s coefficient for COS absorption is only about half that for H2S. For all practical purposes, this means that the solvent rate has to be doubled if not only H2S but COS as well has to be eliminated completely (Fig. 2.7). Since, in the case of mixed solvents, COS is converted by hydroljrsis to H2S and this reaction proceeds very rapidly, physico-chemical gas cleaning units are designed only for H2S removal. Such processes are used to good effect at ambient temperature and pressures of more than 15 bar. 

Solubilities and diffusivities of gas are practically always required for design of gas-liquid process and obtaining solubility and diffusivity data for the gas-liquid system under consideration may be a chalenging problem so wide is the range of solutes and solvent the chemical engineer or researcher may encounter. Moreover the choice of a suitable gas-liquid contactor is also a question of matching these data, those concerning the reaction kinetics and the physical kinetics characteristics of the proposed reactor, i.e., specific gas-liquid interfacial area, heat and mass transfer coefficients and gas or liquid holdup. Some considerations on solubility and diffusivity will be proposed in part 1 of this review and on gas-liquid mass transfer in part 2. 

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