Multiple Steady States in the Photocatalytic Reactor for Colored Compounds Degradation

The paper reports the occurrence of multiple steady-state zones in most of the constructions of fixed-bed photocatalytic reactors. Such a phenomenon has not been ever observed in a field of photocatalytic reactors. The simulation has been provided for a common case in a photocatalysis—the degradation of colored compounds. The mathematical model of the photocatalytic reactor with immobilized bed has been stated by a simple ideal mixing model (analogous to the CSTR model). The solution has been continued by the two parameters—the Damköhler number and the absorption coefficient related to the inlet stream concentration. Some branches of steady states include the limit point. The performed two-parametric continuation of the limit point showed the cusp bifurcation point. Besides the numerical simulation, the physical explanation of the observed phenomenon has been provided; the multiple steady-states occurrence is controlled by light absorption–reaction rate junction. When the reaction rate is limited by the light absorption, we can say that a light barrier occurs. The dynamical simulations show that when the process is operated in a field of multiple steady states, the overall reactor efficiency is related to the reactor set-up mode.