(346e) Advanced Process Control of Methanol Production from Natural Gas

With the increasing production of natural gas in the US, natural gas-to-Methanol plants are receiving renewed interest. Methanol is an essential feedstock for obtaining more complex chemical structures, such as acetic acid, methyl tertiary butyl ether, dimethyl ether, and methylamine. It is also used in the manufacture of a variety of industrial and consumer products. In this research, a plant-wide dynamic simulation model of the methanol production process is developed based on an actual manufacturing plant at Natgasoline LLC. Based on this dynamic model, a hierarchical control system comprised of Dynamic Matrix Control (DMC) and a basic regulatory control loop is constructed to optimize the plant operation in terms of eliminating methanol losses and minimizing the utility cost under various process upsets. Rigorous DMCplus controller models are developed based on the subspace identification model and simulated in the ASPEN manufacturing software platform. The DMCplus controller developed in this study shows promising results by minimizing methanol losses by over 80% and utility cost by over 30%. The controller shows robustness in handling variations of ±20% feed flow and ±20% feed composition disturbance. Furthermore, the controller also handles disturbance due to the variation of hydrogen content in the syngas. The developed hierarchical multivariable control system significantly outperforms the regulatory PID control strategy in optimizing the methanol process under process constraints.