Energy Targeting and Optimal Pinch Identification through Interval Constraints Logic Propagation Model for Processes with Dependant Streams

Energy efficiency optimization is critical in controlling operating costs of industrial facilities. Previous works related to the HEN targeting and design as well as process conditions modification techniques for better energy consumption is huge and the reader is advised to read the paper of N. Sahinidis, and K. Furman,2002 for detailed review of the subject. Pinch technology emanated in the late seventies, is still the technology of choice for energy conservation in many industrial complexes. During the design of new processes, process conditions are the designer's degrees of freedom. Process changes in base case designs may move the pinch point location and sometimes eliminate it completely. In such cases, the plus-minus principle becomes insufficient to systematically determine the best process changes, and exhaustive enumeration becomes unavoidable. Process conditions play pivotal role in determining process pinch point location and energy consumption and minimum number of HEN units therefore “optimal pinch point” identification is vital for smart plant design using optimal process conditions. Because of the numerous possibilities in process conditions combinations, interval arithmetic instead of real number is used throughout this paper. In this paper, ICLP model for energy consumption targeting and identifying optimal pinch point location and process conditions is introduced for chemical processes, especially the ones that exhibit streams dependence. “Pinch interval” concept that modifies “appropriate placement” rules of pinch technology for energy efficient process design under all possible combinations of process conditions is also introduced. Industrial case study from oil refining applications is used to illustrate the method.

Key Words: Interval Constraint Logic Propagation; Pinch Interval; Optimal Pinch; Energy Efficiency; appropriate placement