Targeting procedures for energy savings by heat integration across plants

Heat integration across plants can be accomplished either directly using process streams or indirectly using intermediate fluids. By applying pinch analysis to a system of two plants, it is first shown that the heat transfer leading effectively to energy savings occurs at temperature levels between the pinch points of both plants. In some cases, however heat transfer in other regions is required to attain maximum savings. A systematic procedure to identify energy-saving targets is discussed as well as a strategy to determine the minimum number of intermediate-fluid circuits needed to achieve maximum savings. An MILP problem is proposed to determine the optimum location of the intermediate fluid circuits. The use of steam as intermediate fluid and extensions to a system of more than two plants are discussed.