Modeling For Multiphase Flow And Transport With Biochemical Reaction In Immobilized Photobioreactor For Hydrogen Production

Currently, due to the continual increase requirement of energy sources , the reduce of finite reserved fossil fuel and the environment pollution brought by fossil fuel burning,etc.,the energy issue will be up against great challenge in 21th century. Photo-biohydrogen production technology, combing solar energy utilizing, waste water biodegradation and hydrogen production, and taking the advantages of environment resource recovery and energy regeneration, thus have abroad applied foreground,and attract a number of foreign and domestic researcher's attention. The integration of immobilized cells technology with photo-hydrogen production can improve the hydrogen production rate and operating stability of photobioreactor. Therefore, further study on the two-phase behaviors, mass and heat transport characteristics, and photosynthetic bacteria biochemistry reaction properties in immobilized cell packed bed photobioreactor is the theoretical foundation of application of such photo-biohydrogen production technology by photobioreactor, and meanwhile shows great academic values.In our study, we forcus on the theoretical research on the biodegradation and hydrogen production characteristics in two kinds of immobilized cell packed bed photobioreactor for hydrogen production. A new two phase mixture model for completely describing gas-liquid flow, light transfer and biochemical reaction characteristics was established meanwhile, we also aimed at the biofilm photobioreactor, and a two phase mixture model was built for describing fluid flow characteristics coupled with biochemical reaction characteristics.A good agreement between the calculated results using our models and experiments results was obtained. The main research contents and achievements are as follows:1) Aimed at the immobilized cell granules packed bed bioreactor, we established the mass transfer model in immobilized cell granules, in order to study fluid flow characteristics and the influences of operating parameters. Based on these, then. A one dimension steady state two phase mixture model was creatively established for describing the multiphase flow, and substrate and products transfer in immobilized cell granules packed bed.2) Based on the one dimension two-phase mixture model established above, the effect of operating conditions and structure parameters of packed bed on glucose consumption efficiency and HPR were studied theoretically. The model results also revealed that illumination intensity, substrate solution pH value and temperature mainly affected kinetic reaction rate and metabolic ability of photosynthetic bacteria, and further lead to effect on glucose consumption efficiency and HPR. The inlet substrate solution flow rate mainly influenced the mass resistance and mass transfer flux. Moreover, the structure parameters of photobioreactor such as porosity, granule radius and height had influence on the biodegrading characteristics and hydrogen production properties by changing the mass transfer area of substrate and products of packed bed.3) Based on the actual situation such as the light absorption in immobilized granules, bulk solution and organic class separately, we added the influence factors of light attenuation to our model. Then, combined with Lambert-beer law of light transfer theory, the light transfer expression was obtained for describing the light intensity distribution in photobioreactor. Based on the above theory, a two dimension steady state two-phase mixture model was creativity established coupled wth biochemical reaction, light attenuation, gas-liquid flow and substrate and products transfer. The model results showed that in low light intensity, the glucose consumption efficiency and HPR increased with the light intensity increase; the substrate concentration decreased along the fluid flow direction, and increased along the light transfer direction; however, the HPR is reverse.4) Aimed at the biofilm packed bed bioreactor of hydrogen production, the porous packed bed was simplified for a parallel plate channel and then the biochemical reaction dynamics model of substrate transfer in biofilm was established. Base on the above theory, a theoretical model named one dimension steady state two-phase mixture model was creatively built containing species diffusion and biochemical reaction. The results of model ware basically in agreement with the experimental data. The model results also revealed that with the increasment of the illumination intensity or the pH value of substrate solution, the consumption efficiency and the hydrogen production rate increased at first then decreased.