(548z) Optimization Based Improved Water Recycle Strategies for Modern Oil Refineries
Due to the present global scenario of rising fresh water demands on scarce water resources, increasingly stressed by water pollution and climate change, opportunities for improving industrial water management have been gaining interest. Towards this end, refineries being one of the major water consuming industry, it is important to improve the disposal, management and treatment of industrial waste water in achieving sustainable development goal (SDG) in a refinery. To explore substantial recycling and reuse with zero liquid discharge practice in an oil refinery complex, here we propose a mathematical optimization framework. Synergistic integration of process knowledge with mathematical models has been used to develop an integrated superstructure of water network in refinery plants in this work. It is shown that the formulation of the optimization problem with both environmental and economic objectives and a systematic utilization of process based decision making helped to converge the formulated NLP problem of a large refinery complex to global optimal solution with significant minimization of computational efforts. The novel features of proposed optimization model include total dissolved solids (TDS) based segregation of waste water streams for distributed treatment plant (Low TDS and High TDS units), phenolics based segregation of sour water, and optimal cycles of concentration based operation of cooling tower for improvement in water foot print and reduction of waste water treatment load in a refinery complex. The application of proposed model for analysis of economic benefits and optimal water routing in the refinery water system has been shown on a representative case study of a large sized refinery complex. A new efficient routing scheme of treated waste water to boiler and cooling tower in optimal ratios has been identified in the resulted global solution of the optimization problem.
Keywords: Refinery water system, Sustainable water management, Integrated superstructure, simultaneous optimization, Distributed effluent treatment plant