Chia, Dian Ning; (2024) Advancing Fluid Separation Technologies: Innovative Approaches in Hybrid Distillation-Membrane Processes and Batch HPLCs. Doctoral thesis (Ph.D), UCL (University College London).

Text Dian Ning CHIA - PhD Thesis.pdf - Accepted Version Access restricted to UCL open access staff until 1 March 2025. Download (26MB)

Abstract

This thesis presents a comprehensive study in two distinct yet critical areas of fluid separation technologies: hybrid distillation-membrane processes and batch high-performance liquid chromatography (HPLC). It addresses the challenges associated with the design and optimisation of those two processes by proposing a superstructure model for each process. The research starts by exploring approaches to improving the efficiency of optimisation for complex chemical processes. The optimisation of chemical processes often requires the solution of mixed integer non-linear programming problems, posing challenges to optimisation tasks. The approaches proposed include an initialisation procedure for deterministic optimisation, five speed-up approaches for stochastic optimisation, and a combined sequential stochastic-deterministic optimisation approach. Several case studies with different complex chemical processes revealed that the proposed approaches could yield optimal designs more efficiently. The thesis then explores the hybrid distillation-membrane process comprising two main separation processes, distillation columns and membranes. The modelling and optimisation of distillation columns are well-studied in the literature but not for membranes. Therefore, this work proposes a superstructure model for the membranes and discusses the solutions to tackle its optimisation challenges. Then, with the membrane superstructure proposed, this work delves deeper into the superstructure modelling and optimisation of a basic hybrid distillation-pervaporation process and advanced hybrid dividing wall columns. A thorough comparison of the basic and advanced hybrid processes with their conventional counterparts showed that using membranes in hybrid processes can reduce overall energy consumption. Finally, the thesis ventures into batch HPLC, where the study on superstructure modelling and optimisation is minimal. This work provides a step-by-step formulation of a superstructure model for batch HPLC that can handle various operating policies, including the conventional elution mode and close-loop recycling policies. Superstructure optimisation has auspicious results in time efficiency compared to the conventional approach that optimises one policy at a time.

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