Experimental Study Of Hydrogen Production From Model Bio-syngas Via Water Gas Shift Reaction

With the fossil fuels in the world gradually exhausted, the demand of sustainable and clean energy receives a great deal of attention. Besides, pollutants and green-house gases emissions have caused serious environmental problems. For long-term considerations, research for clean and renewable energy is an imperative task of now and future. Biomass is one of the most promising energy resources, and hydrogen is the carrier of clean energy. Consequently, hydrogen production from biomass is globally becoming a promising technology for transformation of energy ultilization.Hydrogen production from bio-syngas via high-low temperature water gas shift reactionis a new process of hydrogen production. In this study, a fix bed reactor suitable for water gas shift reaction was set up. Simulate the bio-syngas by mixing CO, CO2, H2, CH4 and N2. Considering that bio-syngas contains higher CO2 content, model bio-syngas under the presence of(0 vol. % to 30 vol. %) and 37 vol. % CO2 were used, and the Fe-Cr and Cu-Zn commercial catalysts were testedwith model bio-syngas for shift reaction. Chemical equilibrium calculation based on the minimization of Gibbs free energy was employed to compare the equilibrium with the experintal data. The impacts of space velocity, reaction temperature, and H2O/CO ratio on hydrogen yield were investigated.The high temperature shift experimental results show thatchangingCO2 concentration has less influence on the activity of Fe-Cr catalyst, the optimal WGSR temperature occurs at 450℃. No Methanation and deactivation was observed even at low H2O/CO ratio due to the good selectivity to model bio-syngas. The optimal WGSR H2O/CO ratio is 3, and the relatively improving efficiency(RIE) suggests that reactant gas with CO2 higher than 20 vol. % favors space velocity lower than 2500 h-1.Thelow temperature shift experimental results show that high CO2content(37 vol. %) can make the optimal reaction temperature of Cu-Zn catalyst increased from 200 ℃ to250 ℃. Within the scope of experimental conditions, the highest CO conversion 90.7% and H2 increase 4.23 vol. % were achieved. The optimal low temperature shift reaction parameters of hydrogen production from bio-syngas are temperature at 250℃, H2O/CO ratio 5, and space velocity lower than 2750h-1.Comparing the experimental data with the thermodynamic equilibrium, it was observed that large difference from experimental data and equilibrium when the reaction temperatures are lower than 450 ℃(Fe-Cr catalyst) and 250 ℃(Cu-Zn catalyst) respectively, and this indicatesthe excitement of activity of catalyst depends critically on temperature. Higher reaction temperature, within the safe temperature region, leads to better performance, and makes the experimental data closer to equilibrium.After high temperature WGSR with model bio-syngas containing highest CO230 vol. %, the CO2 concentration of product gas increase to 37 vol. %.Sequently, use the product gas containing CO2 37 vol. % to process low temperature WGSR, it will produce totally 12.36 vol. %of H2 increase. High temperature WGSR accounts for most of the contribution 79.2 %, however, low temperature WGSR only accounts for 20.8 %.The achievements of this research can be used for reference in the development of hydrogen production from biomass.