Mathematical Simulation And Rheologi Cal Properties Of Photosynthetic Bacteria Hydrogen Production System With Supemicro Straw

ABSTRACT: This paper is supported by the National Natural Science Foundation (No. 50976029).Energy shortage and environment pollution is the most serious problems in 21th century. So it is necessary to search cellulose hydrogen with low-cost crop straw as raw material and develop industrial-scale biomass hydrogen production technology to supply energy inadequate, protect national energy security strategy, reduce dependence on fossil fuel and improve biomass recycling. Biomass straw photosynthetic hydrogen production is multiphase flow system consisting of solid phase and liquid phase. The fluid rheological properties in the reactor can influence temperature and velocity evenly distribution, photosynthetic pigment synthesis, lighting suface sedimentary and contact between photosynthesis bacteria and biomass straw. The change on the original liquid characteristics and biochemical reaction process influence bioreactor overall hybrid behavior, mass and heat transfer, and ultimately affect the ability of photosynthetic bacteria produce hydrogen. In addition, multiphase flow make some area become stagnant area and some area have bigger wallop which would reduce biomass straw photosynthetic hydrogen production reactor service life. So studying flow field mathematical simulation and rheological properties of photosynthetic bacteria hydrogen production system with ultramicro straw is very important.It was mainly based on the principle of multiphase flow and the characteristics of photosynthetic bacteria hydrogen production to research rheological properties and system turbidity. Furthermore, it revealed the influence of rheological properties and turbidity on biomass straw hydrogen production, analyzed velocity field and concentration field distribution, completed flow field mathematical simulation, and established multiphase flow mathematical model. The results showed that:(1)Particle size and process parameters was main influence factors on relative viscosity of hydrogen production system. When the total mass of particles remained unchanged, the smaller particle size enhanced the interaction strength among each other, reduced the liquidity of the system. The relative viscosity of hydrogen production system with ultramicro biomass straw were higher than other granularity. The orthogonal experiment indicated that the infuence of hydrogen production process parameters on relative viscosity was substrate concentration> temperature > inoculation>illumination. The mixtuere of supemicro straw hydrogen production was non-newtonian fluid, and its rheological properties became more complex with hydrogen production process.(2) The turbidity of hydrogen production system mainly influenced by solid phase particle concentration, particle size and pretreatment. The turbidity was the highest for ultramicro sorghum hydrogen production system, and increased with the increase of the solid phase particle concentration, while total variation which slightly increased at first and then decreased during the hydrogen production process unchanged with different pretreatment. Ultramicro deal was conducive to hydrogen production, but the capacity of hydrogen production lagged behind turbidity and viscosity changes.(3) The increased degradation ability of photosynthetic bacteria on biomass straw caused liquid relative viscosity and settlement resistance increase when inoculation increased, and particle size minished. Meanwhile, photosynthetic bacteria growth made system turbidity increase. After photosynthetic bacteria going into stabilization and decay period, exocellular polysaccharide was broken into hydrogen, volatile fatty acids and alcohols which made liquid relative viscosity significantly decrease, solid phase settling velocity increase, system turbidity rapidly reduce and hydrogen production amount increase.(4) Relative viscosity was not very different in the photobioreactor. The wallop of inflow wate make solid particles float, system turbidity increase, and solid-liquid contact area increase. The velocity of upflow chamber were significantly higher than downflow chamber in the same positions. The influence of substrate concentration mainly was that flow ability bacome bad due to the impact of relative viscosity. According to matlab software, 33℃temperature, 3500 Lx illumination, 25% inoculation and 55 g/L substrate were appropriate for the biological hydrogen production of PSB with ultramicro straw.(5)The CFD technology was applied to simulate and analyze the flow field in photosynthetic hydrogen production reactor. Based on mixture model, information about flow field was obtained in detail. The flow velocity of photosynthetic hydrogen production reactor evolved from the mainstream to the surrounding area, and gradually achieved uniform distribution. The bottom of reactor had obvious plug-flow movement which made sedimentation solid particles move forward and assemble in the upflow chamber. The height and the concentrations of solid-phase distribution of upflow chamber were significantly higher than downflow chamber. Most areas of the reactor were eddy current, and the maximum eddy current was at the bottom of the reactor, which was conducive to mix photosynthetic bacteria and straw particles and enhance mass transfer. In addition, the calculated results showed that the simulation results of flow field and notes were in accordance with the experimental results.