Application of exergy analysis for improving energy efficiency of natural gas liquids recovery processes

Thermodynamic analysis and optimization method is applied to provide design guidelines for improving energy efficiency and cost-effectiveness of natural gas liquids recovery processes. Exergy analysis is adopted in this study as a thermodynamic tool to evaluate the loss of exergy associated with irreversibility in natural gas liquids recovery processes, with which conceptual understanding on inefficient design feature or equipment can be obtained. Natural gas liquids processes are modeled and simulated within UniSim® simulator, with which detailed thermodynamic information are obtained for calculating exergy loss. The optimization framework is developed by minimizing overall exergy loss, as an objective function, subject to product specifications and engineering constraints. The optimization is carried out within MATLAB® with the aid of a stochastic solver based on genetic algorithms. The process simulator is linked and interacted with the optimization solver, in which optimal operating conditions can be determined. A case study is presented to illustrate the benefit of using exergy analysis for the design and optimization of natural gas liquids processes and to demonstrate the applicability of design method proposed in this paper.