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# Coupling Process Plants and Utility Systems for Site Scale Steam Integration

journal contribution

posted on 2013-10-16, 00:00 authored by B. J. Zhang, X. L. Luo, X. Z. Chen, Q. L. ChenThe
refining and petrochemical industries generally own process
plants and utility systems. Process plants are configured to finish
the transformation and separation of materials, and utility systems
supply the energy requirements for the process plants. Therefore,
integrating two of them is more favorable than optimizing them individually.
A coupling mixed integer nonlinear programming model is presented
in this work to integrate process plants and utility systems; the
objective is to minimize the energy costs to meet the requirements
of the process operations and to maintain a steam balance in the total
site. The mathematical model includes three parts: the heat integration
of the process plants, the optimization of the utility system, and
the coupling equations for the site-scale steam integration. The heat
integration of the process plant is formulated on the basis of pinch
analysis involving heat loads of the process heaters and steam generation
and requirements. An optimization of the utility system is also proposed
to provide the relationship between steam balance, power generation,
and fuel requirements. Coupling equations are used to balance the
steam streams in each level between the process plants and utility
systems. Two real industrial examples are also investigated to demonstrate
the performance of the presented mathematical model. The solution
results indicate not only a more profitable integration scheme but
also increases in energy utilization efficiencies and the operational
capacities of the utility systems.