Dynamic Simulation and Control of the Demethanizer Unit in Natural Gas Refining Plant

The NGL refinery of the Sirri Island has a major role in the production of high-value products. One of the most important refinery units is the demethanizer unit, comprising of a complex network of distillation towers and heat exchangers. In the first step, using the Aspen Hysys software, a proper steady state model was developed for this unit in which the simulation of the main equipment that is, distillation towers and heat exchangers were carried out. The steady state simulation results are in good agreement with the data gathered from the real plant. Then, the simulation was transferred from steady state to dynamic mode in which the main equipment such as distillation towers and control valves were sized. Here, the available controllers which are currently present in the real plant, were added to the simulation. Using the auto tuning variation (ATV) method and by considering the desired behavior namely, stability, fast response, and absence of oscillation, the overall performance of the controllers were examined under different scenarios. Based on the results, it was identified that with carefully tuning the controllers parameters, much better performance can be achieved.