A design procedure for heat-integrated distillation column sequencing of natural gas liquid fractionation processes

The separation of NGL (natural gas liquids) in gas processing is energy-intensive, requiring systematic process design and optimization to reduce energy consumption and to identify cost-effective solutions for the recovery valuable hydrocarbons. As NGL fractionation processes require a sequence of distillation columns to separate multi-component mixtures the determination of optimal energy-efficient distillation sequences and operating conditions is not a simple task. A design methodology is proposed in this study in which the process simulator Aspen HYSYS^® is linked with an optimization algorithm available in MATLAB^®. The proposed methodology involves a procedure where in the first step possible distillation sequences are screened using a short-cut distillation column model. In the second step a few selected and promising candidate distillation sequences are further simulated and optimized, again using the same short-cut model. Finally, rigorous simulations are used to validate and confirm the feasibility of the optimal designs. A case study is presented to demonstrate the applicability of the proposed design framework for the design and optimization of NGL fractionation processes in practice.