(390e) Energy Optimization of a Low-Temperature Distillation System for Upgradation of High CO2 Content Natural Gas

High CO₂ content in raw natural gas reduces the overall calorific value and creates numerous transportation and handling complications. Substantial reserves of sour natural gas, especially those with high CO₂ content, remain undeveloped because of technical and economic challenges. Low-temperature distillation (LTD) is a key technology for purification of high CO₂ content natural gas. In this process, methane is recovered as the top product, whereas CO₂ and heavy hydrocarbons are recovered from the bottoms of a series of distillation columns. Because of low thermodynamic efficiency of conventional distillation processes, the LTD process is highly energy intensive. The principle challenge in the design of an LTD system is to optimize the operating conditions of a series of distillation columns while simultaneously minimizing the total utility requirements and avoiding CO₂ solidification.

In this study, an LTD process for upgradation of high CO₂ content natural gas was optimized using Aspen Plus®. Effect of recycle streams, feed split, feed location, and extractive solvent flow rate have been explored in detail. The optimized system can recover 6% more methane with 12% lower energy consumption while maintaining the target 98.8% purity and avoiding CO₂ solidification.