Phase equilibrium data regression is an unavoidable task necessary to obtain the appropriate values for any model to be used in separation equipment design for chemical process simulation and optimization. The accuracy of this process depends on different factors such as the experimental data quality, the selected model and the calculation algorithm. The present paper summarizes the results and conclusions achieved in our research on the capabilities and limitations of the existing G E models and about strategies that can be included in the correlation algorithms to improve the convergence and avoid inconsistencies. The NRTL model has been selected as a representative local composition model. New capabilities of this model, but also several relevant limitations, have been identified and some examples of the application of a modified NRTL equation have been discussed. Furthermore, a regression algorithm has been developed that allows for the advisable simultaneous regression of all the condensed phase equilibrium regions that are present in ternary systems at constant T and P. It includes specific strategies designed to avoid some of the pitfalls frequently found in commercial regression tools for phase equilibrium calculations. Most of the proposed strategies are based on the geometrical interpretation of the lowest common tangent plane equilibrium criterion, which allows an unambiguous comprehension of the behavior of the mixtures. The paper aims to show all the work as a whole in order to reveal the necessary efforts that must be devoted to overcome the difficulties that still exist in the phase equilibrium data regression problem.
Abstract:The effect of three synthesised mesoporous catalysts (a SBA-15 and two MCM-41) on the smoke of two reference tobaccos (1R5F and 3R4F) has been studied. Mixtures of the catalysts and each tobacco were smoked under the ISO 3388 standard conditions. The gaseous compounds and the particulate matter condensed in the filter tip (TPM-F) and in a trap located downstream (TPM-T) from the mainstream smoke were analysed separately. The results obtained show that these catalysts directly mixed with tobacco are capable of reducing the yield of most of the compounds studied in the mainstream tobacco smoke. SBA-15 is a better additive for reducing the amount of the compounds analysed in 1R5F and 3R4F tobaccos, both in the liquid fraction (TPM-F and TPM-T) and in the gas fraction. The effect of the studied catalysts is higher on the full-flavour cigarette than on the ultra-low one. As an example, the reductions observed for CO and nicotine in TPM-T from 3R4F as a consequence of the SBA-15 addition were 46% and 77%, respectively. Thus, although the three checked materials are able to provide noticeable reductions, the best is the one having the higher size of pores (SBA-15).
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