Study On The Reaction Pathways Of Steam Methane Reforming For H₂ Production With Different Reaction Conditions

H₂ is regarded as one of the most promising clean energy with high energy efficiency,large heat value,no greenhouse effect and zero pollution emissions.Natural gas is an important raw material for H₂ production.The main component of natural gas is methane.There are many processes to produce H₂ from methane.Steam methane reforming method is a common commercial technology and is used widely for industrial H₂ production.In this paper,the steam methane reforming process is numerically studied in Ansys Fluent based on Latham’s reforming tube.The numerical model is validated by the experimental data.The yield of H₂ and reaction pathways are studied,and the effect mechanisms of temperature,pressure and the ratio of steam to carbon on the reaction pathways for H₂ production are investigated in detail.The reaction pathways analyses for H₂ production are carried out under Latham’sexperimental condition.The results are as follows:in the steam methane reforming process,CH₃ is mainly decomposed from CH₄;C₂H₆ and CH₃OH are primarily produced from CH₃;H2 is mainly generated from successive dehydrogenation of C₂H₆ and CH₃OH.When the temperature increases from 600℃to 1000℃,mole fraction of H₂ at outlet rises from 44.91%to 50.21%.High temperature is not conducive to the formation of C₂H₆,causing reduction in rates of C₂H₆successive dehydrogenation pathways such as CH₄→CH₃→C₂H₆→C₂H₅→C₂H₄→H₂.More CH₃OH is produced and the pathway of CH₄→CH₃→CH₃OH→H₂is enhanced.Mole fraction of H₂ at outlet varies from 40.79%to 44.91%with the pressure rising from2MPa to 3MPa.The reactions pathways such as CH₄→H₂,CH₄→CH₃→C₂H₆→C₂H₅→H₂,CH₄→CH₃→CH₃OH→H₂ and CH₄→CH₃→CH₃OH→CH₂OH→CH₂O→H₂ are significantly strengthened.When the ratio of steam to carbon rises from 3 to 6,dry mole fraction of H₂ at outlet changes from 71.52%to 75.85%.A higher steam to carbon ratio results in decease of C₂H₆.Thus the C₂H₆successive dehydrogenation pathways such as CH₄→CH₃→C₂H₆→C₂H₅→H₂,CH₄→CH₃→C₂H₆→C₂H₅→C₂H₄→H₂and CH₄→CH₃→C₂H₆→C₂H₅→C₂H₄→C₂H₃→H₂are weakened.More CH₃OH is formed and the pathways of CH₃OH→H₂,CH₃OH→CH₂OH→CH₂O→H₂ and CH₃OH→CH₂OH→CH₂O→HCO→H₂ make more contributions to the yield of H₂.