Basic Application Research On The Hydrogen Production From Biomass In Tandem Fluidized Beds And From Crude Bio-oil In Dual Fixed Beds

Energy is an important material basis for the survival and continuable development of the human beings. With the rapid increases in the energy demand and the pressure from the environment protection, the application of renewable bio-energy is receiving great attention globally. Hydrogen is recognized as a clean fuel and energy carrier with very high heating value and will play an important role in the future global economy. Biomass is rich and friendly environmentally renewable resource, hydrogen production from biomass is one of the most promising options and it is still in development. The improvement of hydrogen yield and energy efficiency as well as the decrease in hydrogen production cost and the catalyst deactivation, etc., are the key problems existing in the investigation of hydrogen production from biomass. In view of these problems, novel approaches for hydrogen production from biomass and biomas pyrolysis oil (i.e., bio-oil) were proposed in our research. The main content of present thesis was focused on the items as follows.1. Hydrogen Production from Biomass through the Integrative Tandem Fluidized Beds Reaction SystemBasing on the previous work, an integrative tandem fluidized beds reaction system for hydrogen production from biomas was firstly designed and manufactured. This reaction system was mainly made of four main units, i.e., the unit of the biomass pyrolysis, the unit of the intermediate products'collection and sampling, the unit of the steam reforming of bio-oil vapor, and the unit of final product purification and measuring. In this work, hydrogen was produced from biomass by a three stepwise process. In the first step, the biomass was converted into the oxygenated organic compounds vapor (i.e., the bio-oil vapor) by the fast pyrolysis of biomass in the pyrolysis reactor with a capacity of 2-20 kg moisture-free biomass/h. In the second step, the bio-oil vapor without cooling was then fed into the reforming rector and converted the oxygenated organic compounds into the rich-hydrogen mixture gas (i.e, H2, CO2, CO, etc.) via the catalytic steam reforming of the bio-oil vapor. Finally, the mixture gas was purified to produce pure hydrogen with a lower impurity by removing ash and CO2, etc. The most important parameters, such as biomass pyrolysis temperature (Tp), vapor residence time (Ï„) in the pyrolysis reactor and reforming temperature (Tr) in the reforming reactor, steam/bio-oil carbon molar ratio (S/C) was investigated. The results indicated that, in the pyrolysis temperature range of 430 ~ 630 oC, the bio-oil yield initially increased with temperature and then decreased. The yield of pyrolysis gas increased with temperature, accompanied by the opposite trend of the char yield. The effect of vapor residence time on the products'yields was not so obvious. Meanwhile, in the reforming reactor, the final hydrogen yield increased with incresing the reforming temperature and S/C. A hydrogen yield of 79.1 gH2/kg moisture-free biomass was obtained under the conditions of Tp = 480 oC,Ï„= 0.62 s and Tr =700 oC, S/C= 4.8, GHSV= 47,000 h-1 with the product gas's composition of H2 (68.4%),CO2 (25.8%), CO (7.2%) and CH4 (0.1%). The hydrogen yield can be further improved through the steam gasification of the biomass char.2. Hydrogen Production from Crude Bio-oil through the Integrative Dual Fixed Beds Reaction SystemHigh efficient production of hydrogen from the crude bio-oil was performed in the gasification-reforming dual beds. A recently developed electrochemical catalytic reforming method was applied in the downstream reforming bed using NiCuZnAl catalyst. Production of hydrogen from the crude bio-oil through both the single gasification and integrative gasification-reforming processes was investigated. Results showed that the hydrogen yield in the single gasification was very low (< 30 %).The maximum hydrogen yield of 81.4 % with carbon conversion of 87.6 % was obtained through the integrative process under the conditions of Tg = 800 oC, f (bio-oil fed rate) = 14.4 g/h, S/C = 10.6, GHSV = 7810 h-1 and Tr = 700 oC. Hydrogen is a major product (~ 73 vol%) together with by-products of CO2 (~ 26 vol%) as well as very low content of CO (< 1 %) and a trace amount of CH4 through the integrative route. In particular, the deactivation of the catalyst was significantly depressed by using the integrative gasification-reforming method, comparing to the direct reforming of the crude bio-oil. XRD, XPS and TGA, etc., were employed to characterize the catalysts before and after reaction.