Study On Hydrogen Production By Steam Gasification Of Fe_xO_y/CaO In-situ Catalytic Biochar Counterflow Reactor Bed

Biomass gasification hydrogen production technology is one of the important research directions in the high value conversion of biomass energy.Biochar produced by pyrolysis of biomass is a good raw material for gasification.High quality hydrogen-rich gas can be obtained by the steam gasification reaction of biochar.However,the slow reaction rate of the steam gasification of biochar limits the hydrogen production capacity of the gasification.Considering that Fe_xO_y/CaO have certain in-situ catalytic activity for biochar steam gasification reaction.Combining the reaction characteristics in the gasification reaction bed,this paper proposes the idea of in situ Fe_xO_y/CaO catalytic biochar reaction bed counterflow steam gasification to enhance hydrogen production.Focusing on the key scientific issues of high-efficiency hydrogen production by biochar steam gasification,biochar prepared from poplar wood pellets is used as a raw material to conduct steam gasification reaction characteristics in a counterflow reaction bed.Choose the low cost and abundant Fe₂O₃and CaO as additives,and the steam gasification reaction characteristics are studied in a counterflow reaction bed.Analyze the gasification intensity,gas production rules,kinetic reaction characteristics of biochar under different gas chemical conditions,and simulate and evaluate the characteristics of gasification products.The characteristics of different biochar steam gasification products and the action mechanism of additives on biochar steam gasification are obtained.The specific content is as follows:（1）Based on the counterflow gasification reaction bed,the reaction characteristics of biochar steam gasification under the action of additives were studied.The study found that the additive Fe₂O₃can be reduced to low valent iron oxides in the steam gasification reaction,which helps to enhance the catalytic reforming ability of biochar.Under the temperature of 800°C and the steam flow rate of 1.25ml/min,biochar-Fe₂O₃improves the gasification intensity most significantly.Additive CaO can increase the reactive sites on the surface of biochar and increase the rate of hydrogen production per unit time.Under the temperature of 850°C and the steam flow rate of 3.75ml/min,biochar-CaO improves the gasification intensity most significantly.Compared with the updraft and downdraft reaction beds,the counterflow reaction bed has higher gasification intensity,and the gas phase product contains higher CO and CH₄content.The H₂content can reach 62.74%.The upper suction section and the lower suction section of the counterflow reaction are mainly the gasification reaction process between the char steam and the gas reforming reaction process.（2）The thermogravimetric analysis method is used to conduct kinetic experimental research on biochar,biochar-Fe₂O₃and biochar-CaO.The"model matching method"is used to solve the kinetic parameters of biochar in a constant temperature process.The study found that the addition of Fe₂O₃/CaO changed the physical and chemical properties of biochar,thereby changing the reaction mechanism function.The reaction mechanism functions of biochar and biochar-Fe₂O₃/CaO were 1-（1-α）^1/2and 1-（1-α）^1/3,it is concluded from the change law of conversion rate and time that the addition of Fe₂O₃will inhibit the progress of the gasification reaction,while the addition of CaO will increase the conversion rate of carbon,thereby promoting the progress of the gasification reaction.（3）Using the simulation software to establish a thermodynamic equilibrium model based on the principle of Gibbs free energy minimization,which is used to evaluate the biochar carbon steam gasification process and capacity research.The study found that the influence of the kinetic reaction on the steam gasification of biochar is greater than the influence of thermodynamic reaction on it.The increase of S/B can significantly increase the hydrogen production rate of biochar.Under the action of the additive CaO,which can effectively increase the hydrogen production rate of biochar.The maximum hydrogen production rate can reach1.75Nm³/kg-biochar.At the same time,CaO has a certain degree of selective catalysis in the actual reaction.The energy produced by the biochar steam gasification reaction contains two parts:chemical energy and thermal energy.Effective energy utilization can further promote the development of biomass energy.