Research On Efficient Hydrogen Production From The Mixture Of Biomass And Crude Glycerin

With fossil fuel depleting and increasing serious environmental problems, more and more efforts have been paid on biomass energy development and utilization. Hydrogen is a clean energy carrier in 21st century. Biomass, as the carbon-neutral source of renewable energy, its utilization to produce hydrogen draws wide attention. Glycerin is a by-product in biodiesel industry. With the rapid development of biodiesel, how to deal with the increasing glycerin production is an important issue for researchers. Under the support of National Natural Science Foundation of China (Grant No. 20590367) and International S&T cooperation program of MOST (Grant No. 2006DFA62370), a detail research was carried out to understand the co-gasification of biomass and glycerin for hydrogen production.The gasification kinetic study of biomass, biomass/glycerin, biomass/crude glycerin has been investigated by non-isothermal thermogravimetry. In this paper, the kinetics parameters such as apparent activation energy and pre-exponential factor of different combinations in different heating rates were calculated by using the Coats-Redfern method. Experiment results showed that the gasification process of corn cob in the low temperature segment can be described by first-order model and three-order model in the high temperature segment: when mixed with glycerin(or crude glycerin) the order of gasification is still first-order in low temperature but reduced to 1.5-order in high temperature. Based on the analysis of DSC curve, it can be concluded that the presence of glycerin can reduce the gasification temperature of the mixture, as well as change the gasification route.Referenced to traditional down draft fixed bed gasifier for biomass gasification, we designed and manufactured a co-gasification fixed-bed gasifier. In order to save energy and to control pressure easily, we put the gasifier and reformer in one bed in this system. With the basic properties calculation of raw material, the basic design parameters of each part in the entire rig were determined.We conducted a series of experiments in the fixed-bed gasifier for corn cob, corn/glycerin, corn cob/crude glycerin. The influence of operating parameters, such as temperature, pressure, steam, CaO, catalyst and glycerin/biomass, on gas products distribution was investigated and the optimum operating parameters for hydrogen production was determined. The results showed that in the presence of catalyst, increase of temperature reduced the hydrogen yield gradually, which indicated that the two catalysts favor to produce hydrogen in lower temperature. The influence of steam on the hydrogen production is not obvious at the presence of CaO. The mechanism of co-gasification is different from that of biomass or glycerin. With pressure increasing, hydrogen production was increased for co-gasification; while it was reduced for either biomass or glycerin gasification. There has an optimum amount of catalyst used for hydrogen production. If the catalyst was too high, it produces opposite results in the experiment.With the simulation software Aspen Plus11.1, we built a co-gasification model for biomass and glycerin co-gasification. Comparing the simulated value with the experimental value, we confirmed that this model can simulate co-gasification process.