Synthesis of Resource Conservation Networks for Batch and Continuous Processes
Date Issued
2011
Date
2011
Author(s)
Lee, Jui-Yuan
Abstract
This thesis deals with resource conservation in process industries through mass and property integration. For the former, the main focus is given to water network synthesis. A graphical technique is first presented for the design of batch water networks (BWNs). By generalizing some useful concepts and principles that are originally developed for continuous processes, this technique consists of a systematic procedure for stream allocation, while determining fresh water consumption and storage policy. The issue of forbidden matches between given water-using operations and its impact on design is explored. To overcome the common limitation of insight-based techniques that they are limited to single contaminant systems, a mathematical technique for the synthesis of BWN with central storage tank(s) is next presented. By assuming a fixed production schedule, the model formulation is based on a superstructure which includes all possible reuse/recycle options. In addition, the synthesis task involves the minimization of fresh water consumption and storage capacity required. An effective method is proposed to facilitate the elimination of forbidden matches.
For property integration, a generic model is developed for the synthesis of property-based resource conservation networks (PRCNs). By treating continuous processes as a special case of batch processes, this model is applicable to both operating modes. The model formulation is based on a superstructure that includes all possible network connections. Apart from direct material reuse/recycle, interception placement is considered to improve streams properties for further recovery or for discharge. In addition, storage tanks are used when a batch process is considered. The developed model is first extended into palm oil mills, with particular focus on the clay bath system for kernel/shell separation based on flotation principle. Different from previous works where the clay bath separator was simplified as a continuous unit, it is modeled more practically as a semicontinuous unit with a specific operating period. Design objectives for clay bath operation comprise the minimization of fresh resource consumption and operating cost. The second extension is to synthesize concentration-based RCNs for continuous processes, where the interaction between sinks and sources is addressed. This has yet to be considered in most previous works on RCN synthesis. Illustrative examples are solved to demonstrate the application of each technique developed in this thesis.
Subjects
Batch process
Mathematical optimization
Network synthesis
Process integration
Property integration
Resource conservation
Type
thesis
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