Bioreactor Scale-up for Water-Gas Shift Reaction

A scale-up study has been performed with three different size reactors to establish the optimum operating conditions for the hydrogen production from synthesis gas by biological water-gas shift reaction using the photosynthetic bacterium Rhodosprilliunt rubrum. Optimum medium composition and operating conditions previously determined in a bench scale 1.25 L continuous stirred tank reactor (CSTR) were used for this study with geometrically similar 2.5, 5.0 and 14.0 L CSTR. The hydrogen production rate, cell concentration and carbon monoxide (CO) conversion were monitored in this scale-up study. The light energy supply was linearly increased with the working volume of the reactors. The agitation rates were determined by the equal power/volume rule. There were good agreement between the calculated agitation rates and the experimentally observed values for all the three different reactors, A 70% carbon monoxide conversion was obtained with 30, 60 and 150 sccm gas flow rate for the 2.5, 5.0 and 14.0 L fermentors respectively. At 70% CO conversion the 2.5 and 5.0 L reactors showed 25% improvement ir~ performance and the 14.0 L reactor showed 11% improvement. The estimated mass transfer coefficients for all four reactors showed very similar values under the optimum operating condition (average KLa= 117 h-1). A 664 h long performance of the process show very stable behavior.