Audun Aspelund

A new process synthesis methodology utilizing pressure exergy in subambient processes

Abstract A graphical representation using the concept of Attainable Region is developed to represent all possible Composite Curves for a pressurized cold stream below ambient to include the cooling effect when the stream is expanded to its target pressure. The Attainable Region is an addition to the ExPAnD methodology, a new tool for Process Synthesis extending Pinch Analysis by explicitly accounting for pressure and including Exergy calculations. The methodology shows great potential for minimizing total shaft work in subambient processes.

An Overview of New Methodologies for the Design of Cryogenic Processes with an emphasis on LNG

Process Synthesis is a term used to describe a class of general and systematic methods for the conceptual design of processing plants and energy systems. The term also refers to the development of the process flowsheet (structure or topology), the selection of unit operations and the determination of the most important operating conditions. The paper shows how design tools can be developed for subambient processes by combining and expanding Process Synthesis methods such as Heuristic Rules, Pinch Analysis, Exergy Analysis, Deterministic Optimization methods (such as Mathematical Programming) and Stochastic Optimization methods (such as Tabu Search). With special emphasis on LNG processes, the use of rigorous Process Simulation and advanced Thermodynamic Packages is an indispensable part of the design exercise. The single most important contribution of this work is the inclusion of pressure as an important design variable.