Complex distillation arrangements to improve energy efficiency in NGL recovery process

Recovery of natural gas liquids (NGL) has become more and more economically attractive as a number of components in natural gas are often separated from the bulk gas and sold separately. There are numerous process configurations and methods known to increase NGL recovery from a feed gas. Using the integrated concept can be potential enhancements to the overall facility availability and project economics. In this work, our aim is how to utilize complex distillation arrangements, such as the double prefractionator arrangement (DPA), double dividing wall column arrangement (DDWC) and Agrawal arrangement, to improve the performance in depropanizing, debutanizing and deisobutanizing fractionation steps in NGL processing. Starting from an initial conventional column sequence, design for the DPA and DDWC were obtained. The results show that the DDWC offers many benefits by decreasing the reboiler and condenser duty. In addition, the reducing of number of columns and their diameter may give a chance to reduce the investment costs. Furthermore, interreboiling of the bottom section of the 2nd DWC was also applied to improve the performance of the DDWC.