Basic Research On Process Of Fermentative Hydrogen Production From Biomass

Under the background of increasing depletion of fossil energy and environmental pollution worsening, development of renewable energy to deal with current energy and environmental crisis has become problems common concerned and to be solved in the world today. Bio-hydrogen production from biomass has been attracting extensive attention as an environmentally friendly process that does not consume fossil fuels. And a lot of research results have been made. However, this technology remains in an early stage of experimentation and investigation. Strains of poor stability, low utilization rate of substrate, and process mechanism of fuzzy become the bottlenecks which hinder its industrial development. Based on this and existing research, optimization of critical process conditions, discussion on mechanism, study on kinetics and relevant fluid phase equilibria, and resource utilization of fermentation liquid waste were conducted on process of bio-hydrogen production from biomass with dairy manure compost as strains. The results will have a great significance in science theory and engineering applications.Experimental design and experiments of strains enrichment process for bio-hydrogen production were carried out by response surface method. Response surface model with yield of hydrogen production as the optimization goal was built. Optimum conditions of strains enrichment of bio-hydrogen production from biomass was forecasted. The yield of hydrogen production of sucrose of5batch verifying experiments had excellent repetition. The average value was270.26mL/(g·sucrose) which was consistent with the model prediction.Two-stage pretreatment of corn stalk by dilute sulfuric acid assisted steam explosion and enhancement of dilute acid hydrolysis with Fe2+was proposed. Experimental design and experiments of this technology were carried out. Response surface model with saccharification rate of corn stalk as the optimization goal was built. Under the optimal conditions of model prediction, saccharification rate of corn stalk reached35.5%, and the yield of hydrogen production was151.50mL H2/(g·corn stalk).The study showed that byproducts of biomass pretreatment process such as furfural,5-hydroxymethylfurfural, acetic acid were toxic to strains of bio-hydrogen production from biomass. Activated carbon adsorption detoxification of corn stalk hydrolysate was proposed. Under the optimal conditions of detoxification, removal rate of furfural,5-hydroxymethylfurfural, acetic acid were91.5%,87.86%, and20.52%, respectively. And the loss ratio of total reducing sugar was7.09%. The results of kinetics studies of activated carbon adsorption of furfural,5-hydroxymethylfurfural, acetic acid, and total reducing sugar indicated that activated carbon adsorption process of each substance followed the pseudo-second-order kinetics. And the yield of hydrogen production of corn stalk increased to169.74mL H2/(g·corn stalk) after detoxification.Kinetics data of bio-hydrogen production of sucrose, glucose, xylose, and corn stalk in30L reactor were obtained. The kinetic models of microbial growth, hydrogen generation, and substrate consumption of the four substrates were built. The comparison of three kinds of kinetic model parameters of four substrates showed that glucose was best for the bio-hydrogen production. The yield of hydrogen production of bio-hydrogen production from corn stalk by adding glucose of3.0g/L reached213.4mL H2/(g·corn stalk). The utilization rate of corn stalk reached60.85%, and H2concentration in gas products at the reaction stationary phase was more than50%. The discussion of process mechanism of bio-hydrogen production showed that the hydrogen was mainly produced by the butyric acid type fermentation in the process of bio-hydrogen production from corn stalk with dairy manure compost as strains.Using the laser monitoring observation technique, the solubilities of xylose and glucose which are the key intermediates of bio-hydrogen production process in fatty acid, mixed fatty acids, and mixed solvents of fatty acids+water were determined. The experimental data were correlated with Apelblat model, and the equation parameters were obtained completely. The standard enthalpy, standard entropy and standard Gibbs free energy change of xylose and glucose in fatty acid, mixed fatty acids, and mixed solvents of fatty acids+water were calculated.△solH>0reveals that the interactions between the xylose, or glucose and solvent molecules are weaker than those between the solvent molecules. The dissolved process is endothermic and the break of association bond is principal.△solS>0shows that when xylose, or glucose dissolved into solvents, the array of solvents molecular was disturbed, the degree of order decrease, randomness increases and entropy increases. The positive△solH and AsolS reveal that the dissolution process of xylose, or glucose in the studied systems were entropy-driven processes.The complexation extraction with tributyl phosphate-octanol as complexing agent was used to recover the mixed carboxylic acid in the fermentation liquid waste of bio-hydrogen production from corn stalk. Under the optimized extraction and back extraction conditions, the extraction rate of mixed carboxylic acid reached98.76%, and the back-extraction rate reached99.10%. The extraction effect of complexing agent was essentially unchanged after ten times of extraction and back-extraction.The results not only will be expedite technological progress of bio-hydrogen production from biomass, but also will be sure to promote the development of relevant subjects.