Advanced operation and monitoring the economic performance of ammonia production based on natural gas steam reforming by using programmed feedforward-Ratio-Cascade controllers

The paper addresses the implementation of advanced process control (APC) and monitoring the economic performance for ammonia production facility relying on natural gas steam reforming. The plant profit optimization was the main goal in the development of a custom APC structure by using a programmed feedforward-ratio-cascade control scheme. The ammonia plant model constructed by UniSim Design software gave a basis for the implementation of a closed-loop control. Ammonia production rate set point acts as the primary/master while holding the steam-to-natural gas and air-to-natural gas molar ratios as secondary/slave controllers. Moreover, the paper considers the main process disturbances on the controlled and manipulated variables. The APC controller with economic objective function ensured better disturbance rejection, more efficient operation of the whole ammonia plant, and increased profitability of up to 7%.