Dynamic control strategy of a distillation system for a composition-adjustable organic Rankine cycle

Wang, E., Yu, Z. and Collings, P. (2017) Dynamic control strategy of a distillation system for a composition-adjustable organic Rankine cycle. Energy, 141, pp. 1038-1051. (doi: 10.1016/j.energy.2017.09.141)

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Abstract

Using zeotropic mixtures as working fluids can improve the thermal efficiency of Organic Rankine cycle (ORC) power plants for utilising geothermal energy. However, currently, such ORC systems cannot regulate the composition of zeotropic mixtures when their operating conditions change. A composition-adjustable ORC system could potentially improve the thermal efficiency by closely matching the cycle to the changing ambient conditions provided that the composition of the working fluid mixture can be adjusted in an economic way. In this paper, a dynamic composition control strategy has been proposed and analysed for such a composition-adjustable ORC system. This method employs a distillation column to separate the two components of the mixture, which can then be pumped back to the main ORC system to adjust the composition of the zeotropic mixture to the required level according to the ambient temperature. The dynamic composition control strategy is simulated using an optimisation algorithm. The design method of the distillation column is presented and its dynamic response characteristics have been analysed using Aspen Plus Dynamics. The results indicate that the average power output can be significantly improved using a composition-adjustable ORC system when the ambient temperature decreases. The size of the distillation system is relatively small and its energy (mainly thermal) consumption is only around 1 percent of the system’s input heat. The research results also show that the dynamic response characteristics of the distillation system can satisfy the requirements of the ORC system.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Wang, Dr Enhua and Collings, Mr Peter and Yu, Professor Zhibin
Authors: Wang, E., Yu, Z., and Collings, P.
College/School:College of Science and Engineering > School of Engineering > Systems Power and Energy
Journal Name:Energy
Publisher:Elsevier
ISSN:0360-5442
ISSN (Online):0360-5442
Published Online:30 September 2017
Copyright Holders:Copyright © 2017 The Authors
First Published:First published in Energy 141: 1038-1051
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
684301Dynamic Organic Rankine Cycle for Recovering Industrial Waste HeatZhibin YuEngineering and Physical Sciences Research Council (EPSRC)EP/N005228/1ENG - ENGINEERING SYSTEMS POWER & ENERGY
709761Thermally Driven Heat Pump Based on an Integrated Thermodynamic Cycle for Low Carbon Domestic Heating (Therma-Pump)Zhibin YuEngineering and Physical Sciences Research Council (EPSRC)EP/N020472/1ENG - ENGINEERING SYSTEMS POWER & ENERGY