PID control system for biogas desulfurization under anoxic conditions

Abstract

BACKGROUND A high H2S elimination capacity has been achieved by anoxic biotrickling filters but accurate control of the nitrate dosage is required. Different control strategies have been used in biotrickling filters but proportional-integral-derivative (PID) control studies have not been reported to date. The aim of this study was to demonstrate the stability and robustness of PID control in an anoxic biotrickling filter.

RESULTS Three PID tuning methods were tested: Ziegler–Nichols, Approximate M-constrained integral gain optimization (AMIGO), and maintained oscillation. The best results were obtained using PID control by the maintained oscillation method, where the system reached stabilization 0.41 h after the H2S inlet step. Moreover, the nitrate consumption was 15.4% lower than that without control.

CONCLUSION The biotrickling filter operated with a PID control strategy proved to be highly stable and robust against the perturbations and disturbances evaluated. The control system was able to operate satisfactorily to a change in the set-point of the outlet H2S concentrations from 25 to 200 ppmV. The desulfurized biogas could be fed directly to an internal combustion engine or solid oxide fuel cell (SOFC) equipped with a zeolite clean unit. © 2017 Society of Chemical Industry