Performance of reactive distillation columns with multiple reactive sections for the disproportionation of trichlorosilane to silane
With reference to the disproportionation of trichlorosilane to silane, a three-stage consecutive reversible reaction with a rather unfavorable reaction kinetics, in-depth comparison in steady-state performance is performed between the column with a single reactive section and those with multiple reactive sections, adopting the equal number of trays and the equal amount of catalyst. The reactive distillation column with multiple reactive sections appears to be considerably superior in the aspect of economic advantages to the reactive distillation columns with single reactive section and these strengths originate essentially from the additional degrees of freedom resulted from the arrangement of multiple reactive sections in process synthesis and design. Arrangement of side-condensers is also examined towards the columns with multiple reactive sections and the outcomes reveal the thermodynamic rational to adopt multiple reactive sections in process development. Although these findings are derived from the specific case study chosen, it should be regarded as the significant potential for analyzing the reactive distillation columns with intricate multiple reversible reactions and separating intricate multiple components.
Reactive distillation columns with two reactive sections: Feed splitting plus external recycle
Abstract For the separations of the reacting mixtures with the most unexpected relative volatility order (i.e., the reactants feature the highest and lowest relative volatilities and the products the intermediate ones), feed splitting (FS) should be combined with top-bottom external recycle (TBER) in the design of reactive distillation columns with two reactive sections (RDC-TRS). Despite FS lessens the reactants with the highest and lowest relative volatilities flowing through the intermediate product extraction stage, the TBER is still effective to improve the contact of the reactants in the upper/lower reactive section and intensifies consequently internal mass and energy integration between the reaction operation and the separation operation involved. The design strategy is evaluated in terms of the separations of esterifications of lactic acid with methanol and palmitic acid with isopropanol. The simultaneous employment of FS and TBER is found to favor greatly system performance and the resultant process design is superior to those with one reactive section reinforced by a TBER and/or FS. These outcomes imply that the RDC-TRS with FS plus TBER should be the most competitive alternative for the separations of the reacting mixtures with the most unexpected relative volatility order.
Deepening Internal Mass Integration in Design of Reactive Distillation Columns, 1: Principle and Procedure
For a reactive distillation column involving reactions with negligible or no thermal effect, the thermodynamic efficiency can be improved substantially through deepening internal mass integration between the reaction operation and the separation operation involved. Four strategies, including the superimposition of reactive section onto rectifying and stripping sections, relocation of feed stages, and redistribution of catalyst within the reactive section, can be used to intensify the internal mass integration. With a systematic application of these strategies, a sequential procedure is devised for the synthesis and design of reactive distillation columns involving reactions with negligible or no thermal effect. Four hypothetical ideal reactive distillation systems are used as examples to evaluate the philosophy proposed, and a substantial reduction of utility consumption is secured in addition to a further abatement in fixed investment. These striking results are evidence of the strong necessity and efficacy of deepening internal mass integration in the synthesis and design of reactive distillation columns involving reactions with negligible or no thermal effect.