Dynamic process intensification of separation systems




Yan, Lingqing

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Distillation is the dominant technology for separating liquid mixtures in the chemical industry. On the one hand, distillation technology is considered to be mature and well understood in terms of design, operation and control. On the other hand, distillation, as a thermal process, involves continuous heating and cooling cycles. The thermal processes in distillation have low thermal efficiency and make the operation of distillation towers energy-intensive (typically represented in terms of heat input to the reboiler). Reducing the energy consumption of distillation towers is significant for the chemical industry considering the dominance of the technology and the magnitude of the energy consumption across the entire chemical industry. Over past few decades, process intensification has emerged as a new processing paradigm and has found practical applications. In the distillation realm, intensified technologies such as dividing wall columns and reactive distillations are available. These technologies, however, involves design changes in terms of either column con figuration or internal structure. Such devices require significant capital expenditure and therefore have limited applications to the columns that are already in operation. This dissertation aims to reduce the operation costs in terms of reboiler/heat duty of distillation while minimizing the associated capital expenditures. A new operational based approach for process intensification, referred to as "Dynamic Process Intensification", is proposed. The new method is applied to distillation systems processing various mixtures from common binary mixtures to realistic petrochemical feedstocks. This dissertation covers nonlinear characteristics of distillation columns, designing the optimal operation strategy with respect to the static and dynamic behaviors of distillation to maximize energy savings, and, last but not least, validating the controllability of distillation towers (both the conventional and intensified designs) to ensure the feasibility of the proposed work.


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