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Experimental Study on Characteristics of Hydrogen Production and Degradation by Immobilized Cells

Author: LiuWei
Tutor: LiaoQiang
School: Chongqing University
Course: Power Engineering and Engineering Thermophysics
Keywords: bio-hydrogen production immobilized granule characteristics of hydrogen production and degradation light conversion efficiency mass transfer model
CLC: X703
Type: Master's thesis
Year: 2009
Downloads: 127
Quote: 0
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Abstract

Serious environment pollution and exhausting fossil fuel make the energy structure facing a great challenge. Hydrogen energy is a future energy with great potential for the characteristic of clean and reproducible. Bio-hydrogen production process which operates in moderate reaction condition could be coupled with the organic contamination degradation, leading to a solution for the confliction of energy requirements and environment protection perfectly. Anaerobic dark-fermentation and light-fermentation have drawn much more attention from researchers among the bio-hydrogen production methods in the present time.Immobilization cells technology was introduced into the hydrogen production field due to its broad merits. The reactor using immobilized granule could effectively increase the biomass amount in the unit bioreactor space, enhance the tolerance ability of the bacteria and increase the hydrogen production rate and bio-degradation rate. Immobilization granule used for hydrogen production was introduced in this study. Two different types of granule suits for different circumstances was produced. Hydrogen production using continuous flow packed bed reactor and single granule reactor immobilized with photosynthetic bacteria (PSB) were developed, which was seldom reported in the present time. The research work and results mainly as follows.1. Hydrogen production using dark-fermentation and photosynthetic bacteria immobilized cells in granule were carried out. Two different types of immobilized granule suit for the dark-fermentation H2 production and PSB H2 production was produced respectively. Active carbon powder and carrageen was added to improve the mass transfer ability in the immobilized granule in the instance of acceptable dilate trait and physical intension satisfied. The diffusion coefficient of glucose in the immobilized granule was calculated through experiments and diffusion model, the diffusion coefficient is proved to be 9.0×10-5 cm2/min.2. A new hydrogen producible strain was identified and cultivated from the sewage sludge. The dark fermentation packed bed in continuous flow hydrogen production experiments was carried out, and effects of various environmental parameters include inlet substrate concentration, pH, temperature, velocity of inlet flow to the hydrogen production rate and degradation rate was studied. The result demonstrated that the optimal operation factor was as the follows: inlet substrate concentration 0.06 mmol/L, pH=6.0, temperature 35℃, velocity of inlet flow 0.000330 m3/h. When the optimal operation factor was satisfied, the maximum H2 production rate was proved to be 1.659 mmol/L/h.3. A hydrogen producible strain Rhodoseudomonas palustris CQK 01 cultivated in the laboratory was immobilized in a single granule and series experiment was took out to examine the affection of various environmental parameters (include light intensity I0,wavelengthλ, pH, temperature T )to the hydrogen production rate and degradation rate. Light intensity and wavelength was proved to be the key factors affect the H2 production behavior. Photo-inhibition occurs as the long-wavelength illumination intensity exceeds 7000 lux, and the H2 production rate was decreased accordingly. When light intensity was 7000 lx,light wavelength was 590 nm, pH was 7.0, temperature was 30℃, inlet substrate velocity of flow is 6.5 mL/h, maximum H2 production rate 0.474mmol/L was reached. Experiments using yellow LED lamp and tungsten lamp respectively were carried out. It was revealed that the light conversion efficiency (LCE) was distinctly higher when the gel granule illuminated by LED lamp, the phenomenon was related to the the intense emission energy of infrared spectrum.4. The mass transfer model coupled with bio-reaction process in the granule was set up to reveal the glucose concentration gradient distribution. It is demonstrated that the biochemical reaction is the limiting process of H2 production behavior in immobilized granule in case the substrate concentration variety and exterior diffusion resistance were ignored. More attention should be paid in the direction of improving the H2 production and substrate degradation ability of PSB in the future.

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