(358b) Study on Advanced Control for Natural Gas Dehydration Plant

Mono ethylene glycol (MEG) based natural gas dehydration process is facing significant glycol losses through stripper column due to vaporization. The regulatory control strategy can minimize this problem at a certain level. This strategy can perform effectively under certain upset conditions as well [1]. However, to run the plant more efficiently and economically it is necessary to apply advanced control technologies to absorb more severe process upsets and eliminate MEG losses as much as possible. In this study, a plant-wide dynamic simulation model for a natural gas dehydration plant has been firstly developed and examined. Based on that, a hierarchical control system comprised of Dynamic Matrix Control (DMC) and basic regulatory control loops is constructed to optimize the plant operation in terms eliminating MEG losses and minimize the operating costs with ensured product qualities under various process upsets. Rigorous DMCplus and DMC3 (adaptative dynamic matrix controller) controller models are respectively developed based on the subspace identification model and simulated with Aspen manufacturing platform. Both DMCplus and DMC3 controllers show promising results of minimizing MEG losses by over 90%. Although DMC3 perform a little better than DMCplus, both controllers are actually very robust, which can handle ±25% feed and ±25% chiller temperature disturbances. Through virtual simulations, this study also shows that the developed hierarchical control system outperforms the regulatory PID controller strategy in minimizing MEG losses under process constraints.

References:

1. Haque, M.E.; Xu, Q.; Palanki, S. Glycol Loss Minimization for a Natural Gas Dehydration Plant under Upset Conditions, Eng. Chem. Res. 2019, 58, 1994-2008.