Input/output Linearization Control Technique for Anaerobic Digestion Reactor with Recirculation

Abstract

Anaerobic digestion (AD) process has been generally applied in factories for wastewater treatment and energy recovery. For the AD processes, the continuously stirred tank reactor (CSTR) with recirculation are typically applied in industries for methane production from wastewater treatment. Since the recycle stream affects the inlet concentration of the reactor, the control performance of traditional PI and PID controllers used to manipulate control actuators may be limited. Additionally, the process control loops related to biochemical reactions are generally employed the operational experiences without process dynamic consideration. A control system based on input/output (I/O) linearization control technique for an anaerobic digestion (AD) process was developed in this work. The control system applied the concept of the I/O linearization technique, which followed dynamic behaviors of the reactor with a two-step (acidogenesis-methanogenesis) kinetic model. The volatile fatty acid (VFA) concentration was regulated by manipulation of the dilution rate to achieve the requested trajectories. Control performances of the closed-loop system were investigated by a simulation under servo and regulatory problems. The simulation results showed that the developed control scheme successfully forced the controlled output to achieve the desired set points and handled the introduced control problems.