Feedback and Feedforward Control of a Biotrickling Filter for H2S Desulfurization with Nitrite as Electron Acceptor

Javier Brito,Martín Ramírez,Fernando Almenglo,Domingo Cantero

doi:10.3390/app9132669

Abstract

Biotrickling filters’ control for H2S removal has special challenges because of complexity of the systems. Feedback and feedforward control were implemented in an anoxic biotrickling filter, operated in co-current flow mode and using nitrite as an electron acceptor. The feedback controller was tuned by three methods—two based on Ziegler-Nichols’ rules (step-response and maintained oscillation) and the third using the Approximate M-constrained Integral Gain Optimization (AMIGO). Inlet H2S staircase step perturbations were studied using a feedforward control and the effect of EBRT considered by feedback control. The tuning method by maintained oscillation shows the lower errors. The selected controller was a PI, because unstable behavior at the lowest H2S inlet loading was found under a PID controller. The PI control was able to maintain an outlet H2S concentration of 14.7 ± 0.45 ppmV at three EBRT, studied at 117 s, 92 s and 67 s. Therefore, desulfurized biogas could be used to feed a fuel cell. Feedforward control enhances BTF performance compared to the system without control. The maximum outlet H2S concentration was reduced by 26.18%, although sulfur selectivity did not exceed 55%, as elemental sulfur was the main oxidation product.

Highlights

Control systems were initially developed in the chemical industry; it is easy to find several applications in bioprocess, combined with the development of data acquisition systems
Feedforward control enhances biotrickling filter (BTF) performance compared to the system without control
The experimental work was done in a lab scale BTF operated in co-current gas flow mode

Summary

Introduction

Control systems were initially developed in the chemical industry; it is easy to find several applications in bioprocess, combined with the development of data acquisition systems. These tools have allowed efficient monitoring of bioprocesses, contributing positively to the development of process-saving costs and guaranteeing the right conditions for the growth and maintenance of the microorganisms involved in these systems. The controller calculates error as the difference between the measured controlled variable and the set point value. The output of a PID controller can be calculated as follows [1]: Z kp de(t) u(t) = kp ·e(t) +

Methods

Results

Conclusion