Hydrogen-rich Gas Production From Steam Gasification Of Biomass Using CaO And A Fe-Cr Water Gas Shift Catalyst

With the rapid development of human society,the exhaustion of the fossil energy poses a major threat to the sustainable development of human society and seeking new clean sustainable energy has become the key to the sustainable development of human society. The hydrogen is hoped to be an important carrier of energy in the future continuable energy system as it is regarded as the ultimate clean energy. Biomass energy is a promising cheap hydrogen source. It is a significant research topic to realize the conversion of biomass energy to hydrogen energy through biomass steam gasification technology.In this paper, a kind of typical forestry processing residues-pine sawdust is used for the object of study. Pyrolysis characteristics of the pine samples under N2 atmosphere are studied separately with the method of non-isothermal thermogravimetric analysis. Pyrolysis dynamic characteristics of pine under different heating rates and calcium oxide(Ca O) addition are also studied with the purpose of providing data to support the biomass gasification process design. The experimental results indicates that: The pyrolysis trends of pine sawdust are basically the same under different heating rates. The increase of heating rate contributes to speed up the pyrolysis reaction rate. The fast pyrolysis of cellulose and hemicellulose mainly occurs within 200~550℃ and the slow pyrolysis and carbonization of lignin mainly occurs within 550~850℃. The experimental samples shows different degradation stages within 200~425℃,425~550℃ and 600~800℃ after adding calcium oxide.The steam gasification experiment of pine samples in a fixed bed gasification reactor is carried out to study the influence produced by different particle sizes of raw material, gasifying reaction temperature, steam to biomass mass ratio(S/B), Ca O to biomass molar ratio(Ca O/C), and Fe2O3-Cr2O3 water-gas shift(WGS) reaction catalyst to biomass mass ratio(Fe2O3-Cr2O3/B) on the content of each gas component within 250~550℃. The experimental results indicates that: 60 mesh raw material is more suitable for steam gasification reaction. The content of H2 shows increasing trend with the increase of gasifying reaction temperature. The content of H2 firstly increases and then decreases with the increase of steam addition, and the H2 concentration exhibits a maximum value with S/B being 2. CO2 is fully absorbed by calcium oxide which also played a catalytic role to steam gasification. With the Ca O/C being 1.5, the CO2 concentration demonstrates a minimum value of 1.28%, and the H2 concentration exhibits a maximum value of 51.08%. The addition of Fe2O3-Cr2O3 WGS catalyst makes significant effects on the content of each gas component within 350~550℃, especially in the presence of calcium oxide absorber. The WGS reaction rate is speeded up by the catalyst because the CO concentration increased greatly as the CO2 being absorbed fully by calcium oxide. A catalyst to biomass mass ratio of 1 results in the maximum value of H2 concentration which reaches 61.27% with Ca O/C being 1.5.