Optimization of Water Network Retrofit Design for Petroleum Refineries with Water Reuse, Regeneration, and Recycle Strategies (W3R)

• Main Author: Ngai Yoong, Foo
• Format: Final Year Project
• Language: English
• Published: Universiti Teknologi PETRONAS 2010
• Subjects: TP Chemical technology
• Online Access: http://utpedia.utp.edu.my/10081/1/2010%20-%20Optimization%20of%20Water%20Network%20Retrofit%20Design%20for%20Petroleum%20Refineries%20with%20Water%20Reuse%2C%20R.pdf; http://utpedia.utp.edu.my/10081/

Water is a key element in the operation of petroleum refineries. In the past, wastewater was typically piped to a centralized treatment plant and research efforts were focused mainly on improving treatment technologies. It was later recognized that distributed wastewater treatment networks in which wastewater streams are treated separately may be preferable to the centralized approach. Moreover, scarcities in freshwater supply and increasingly stringent rules on wastewater discharge have emerges as issues of major concerns to plant operators, along with an increased awareness in the need to support sustainable development initiatives and minimization of water footprint. In line with these development, there are increased interests to incorporate water reuse, regeneration (i.e, treatment), and recycle (W3R) approaches in the design of refinery water network systems, with the aim of minimizing freshwater consumption and wastewater generation. This work presents an optimization model to determine the optimal design of refinery water network systems. The integrated model explicitly considers the incorporation of water minimization strategies by first postulating a source-interceptorsink superstructure that embeds many possible feasible tlowsheet alternatives for the implementation of potential W3R approaches. Subsequently, a mixed-integer nonlinear programming (MINLP) model is formulated based on the superstructure to determine the optimal water network structure in terms of the continuous variables of total stream tlowrates, contaminant concentrations and the 0-l binary variables of stream interconnections in the piping network. The superstructure and the MINLP model explicitly handles the membrane-based interceptors (primarily ultrafiltration and reverse osmosis units) and the non-membrane-based interceptors, in which in the former, the feed, permeate, and reject streams are assumed as an individual process units. The objective of the model is to minimize the fixed capital costs of installing piping interconnections and the variable cost of operating all stream interconnections while reducing the pollutants level to within limits by environmental regulations under all the associated material balances of flows and concentrations. The proposed modeling approach is implemented on an industrially-significant numerical example using the GAMS/BARON global optimization platform to obtain a globally cost-optimal water network topology.