Modeling and Dynamic Control of a Bioreactor for Glycerin Conversion to 1,3 Propanediol

The increasing production of biodiesel generates high quantities of glycerin as major co-product in the process. The potential use of glycerol includes pharmaceutical, cosmetics and food industries; furthermore, its bioconversion to 1,3 propanediol (PDO) represents a novel application in biopolymers area. This investigation focuses on the development of a dynamic model and control of 1,3 PDO production from residual glycerol of biodiesel process by Clostridium diolis strain in a continuous bioreactor. The biological conversion was simulated using the Monod model with product inhibition factor and includes temperature and Ph influence on biomass growth rate. Dynamic behavior of the bioreactor showed a maximum mass flow of 1,3 PDO equal to 79.95 mM*h⁻¹ with a dilution rate 0.23 h⁻¹, while the maximum concentration of the product 539.5 mM*L⁻¹ was achieved with 0.1 h⁻¹ as dilution rate. Based on the model evaluated, two control strategies were implemented, a proportional integral control (PI) and a dynamic matrix control (DMC), its performance was compared using the integral of the absolute error (IAE) at four operating conditions; the results showed IAE values of 13.5 and 53.4 for the best DMC performance (λ = 1) and for the PID 11.9 and 54.8. Also, the integral of the average valve signal (IMV) was evaluated showing a 40% reduction for DMC performance respect to PID performance, improving as well the use of the control valve during continuous operation.