Use this URL to cite or link to this record in EThOS:
Title: Synthesis and optimisation of low temperature gas separation processes
Author: Wang, Jiaona
ISNI:       0000 0001 3560 0901
Awarding Body: University of Manchester : UMIST
Current Institution: University of Manchester
Date of Award: 2004
Availability of Full Text:
Access from EThOS:
This thesis includes two sections. The first section presents a new synthesis framework for screening low temperature heat integrated separation systems. The synthesis and optimisation of low temperature gas separation processes is complex due to the large number of design options for both the separation system and the refrigeration system. In this thesis, task representation is applied to the separation system to accommodate both simple and complex distillation columns. Each task has been developed with several device representations. Condensation for separation is provided by the refrigeration system or heat integration. Design issues for the refrigeration system address the choice of refrigerant, selection of refrigeration structure and heat integration between the refrigeration system with separation processes and within separation process. A sequence-based superstructure is presented to accommodate all options in separation processes. The optimisation framework starts from the investigation of all the task representations for the separation system. Short-cut models of all the novel separation options are provided. An integration procedure is presented based on shaft power targeting. The large number of design options makes conventional enumerative or MiLP methods impractical. Also, for the MINLP, it is difficult to reach the actual optimum due to the highly non-linear nature of the models. In this thesis, the optimisation is carried out using a stochastic method (Genetic Algorithm) which can efficiently tackle mixed variables. Various case studies are examined for various design scenarios. Dephlegmation is an effective low temperature gas separation process, which has been used to reduce power consumption and improve separation efficiency. However, most existing models of a dephlegmator have focused on separation process simulation, the heat exchange characteristics and the refrigeration design were either ignored or based on highly simplified assumptions. The second section of this thesis presents a new framework for the design of dephlegmators that addresses simulation of the multi-component partial condensation, selection of plate-fin heat exchangers and design of the refrigeration process. For simulation, a film model is applied to estimate local mass and heat transfer and integrate for the total area separation. In the design of plate-fin heat exchangers, the key issue is to determine the controlling stream according to the flow pattern in the separation passages Design of refrigeration focuses on the optimisation of the composition when mixed refrigerants are used and on partition temperature when cascade cycles are used. A systematic methodology is proposed to include all these aspects. Various cases are used to provide guidelines in the design of dephlegmators used in multi-component gas mixtures with different refrigeration systems.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available