A model based nonlinear observer for simultaneous state and disturbance estimation in continuous anaerobic digesters
Integration of life sciences & engineering
Design, Analysis & Control of Fermentation Processes (T5-2)
Keywords: Anaerobic digestion, nonlinear observer, state estimation
Anaerobic digestion is a very important biotechnological process used in (a) sewage sludge stabilization, (b) treatment of high organic strength wastewaters, (c) treatment of the organic fraction of solid waste, and (d) production of biogas from energetic plant biomass. The process is often subject to severe disturbances, caused by either organic overloads or entry of inhibitors with the feed. In order to design a proper control algorithm that will secure robust digester operation (if possible at condition maximizing biogas production) it is important to delineate the cause of the imposed disturbance.
A simple nonlinear two-dimensional model based on Andrews kinetics is used to devise a nonlinear observer, capable of identifying the nature and magnitude of disturbance along with an estimation of the states. The observer is based on measurements of the volatile fatty acids and the generated biogas. The approach is based on estimation of the state under two sets of conditions, once neglecting the possible presence of disturbance and once assuming a particular type of disturbance and comparing the two.
The approach is applied for assessment of various disturbance types (organic overload or entry of inhibitor causing a drop in the growth rate of the methanogens) and securing safe operation under (a) open-loop operation and (b) closed-loop output feedback control for enhancement of the stability region at the steady-state maximizing the production of methane.
Presented Thursday 20, 11:36 to 11:54, in session Design, Analysis & Control of Fermentation Processes (T5-2).
