(547k) Implementation of a Control Strategy for a Multitasking Reactive Distillation Column with an Intermediate Condenser

Authors: 
Ramírez-Corona, N., Universidad de las Americas Puebla
Palacios-Rosas, A., Universidad de las Americas Puebla
Segovia-Hernández, J. G., Universidad de Guanajuato
Ortega-González, M. E., Universidad de las Americas Puebla
With the increasing energy demand around the world, global warming, and the continual decrease in fossil fuel reserves, there is growing interest in many countries in renewable, clean and sustainable energies. Most photovoltaic solar cells use various crystalline and amorphous structures of silicon as their semiconductor element. These, can be obtained from silane as a precursor. Silane is commonly synthesized as a result of the disproportionation reactions of trichlorosilane, in a process involving two reactors and various separation units. However, the unfavorable chemical equilibrium in the reaction system causes a substantial recycle ratio, with consequential high investment and energy costs. As a result, previous studies have proposed and designed a new reactive distillation column (RD). This takes advantage of the chemical characteristics of the disproportionation reactions and the significantly different boiling points of their components. The incorporation of an intermediate condenser within the rectification zone in the reactive distillation may alleviate the refrigeration load of the overhead condenser. The optimal design and operating conditions for this RD with an intermediate condenser have been evaluated under steady state conditions. This paper studies the dynamic behavior of the formerly explained system, working in a multitask mode to produce silane, monochlorosilane, and dichlorosilane, with high purity, by adequately switching the operating conditions. Three different control strategies were tested against perturbations in the intermediate condenser’s refrigeration duty, and the associated side stream. The results showed that the best configuration implies a dual temperature control. The reactive distillation column with an intermediate condenser was capable producing the three products, with a purity equal to, or higher than, 99.5%. This control strategy allows successfully stabilization of the system after the tested perturbations. Additionally, a proposal for controlling the rectification zone temperature with the refrigeration load of the intermediate condenser, was also built and tested.