Study On Hydrogen Production By Hexadecane Steam Reforming In Cylindrical Honeycomb Ceramic Reactor

As a representative clean energy,hydrogen energy has the advantages of high energy density and low greenhouse gas emissions that are not available in traditional energy sources.Fuel cell is one of the most efficient ways to use hydrogen energy.Solid oxide fuel cell（SOFC）,as a relatively mature type of fuel cell technology,has good application prospects on movable vehicles such as heavy vehicles,trucks and ships.An important problem that restricts its application is the storage of hydrogen.In order to avoid the use of expensive hydrogen storage tanks,it is an effective solution to use diesel fuel carried by the vehicle to produce hydrogen on site.In this subject,experiments and numerical simulations were carried out on cylindrical hydrogen production reactors using honeycomb ceramic catalyst.A numerical simulation model of steam reforming reaction in honeycomb ceramics was established,and the multi-physics coupling numerical calculation of material transfer,flow,chemical reaction and heat transfer in honeycomb ceramics was performed on the commercial CFD software COMSOL.After verification of grid independence,the influence of the number of grids on the calculation results was excluded.In order to improve the atomization and mixing of water and diesel,a preheating pipeline was designed so that the reactants can be vaporized before entering the reactor.After that,vapor and fuel were injected into the reactor by nozzle and tubes separately.La and K promoted Ni/γ-Al₂O₃ catalysts were prepared by wet impregnation method on cordierite monoliths.The fuel and water supply system and gas production analysis system were designed,and the hydrogen production experiment platform was completed.N-hexadecane was used as the surrogate of diesel to carry out experimental research on the test bench.The effects of water-to-carbon ratio,n-hexadecane liquid space velocity,reaction temperature and catalyst composition on the hydrogen production performance parameters such as n-hexadecane conversion rate,gas production composition and gas production were studied respectively.Analyzed the experimental data and found the most suitable working conditions and catalyst components of the system.The catalyst composition is Ni O_0.13/（La₂O₃）_0.1/K₂O_0.03/（γ-Al₂O₃）_0.15,the water-to-carbon ratio is 3.5,n-hexadecane liquid space velocity is 156.3 h^-1,and the reaction temperature is 800°C.The stability test of the hydrogen production system was carried out under this working condition.The results showed that the conversion rate of n-hexadecane was maintained at about 100%within 190 min,and the hydrogen production was above 7500 m L/min;The conversion rate was maintained above 90%,and the hydrogen output is above 7000m L/min within 460 min.The feasibility of the reforming hydrogen production-SOFC integrated system was verified.The calculation results based on the established simulation model were compared with experimental data to verify the correctness of the model.The distribution of the concentration field,reaction rate field and temperature field of the honeycomb ceramics was analyzed,which lays the foundation for the study of the mechanism of diesel steam reforming reaction,and provides a theoretical basis for the optimization of the hydrogen production system.The experiments and numerical simulations in this dissertation revealed the characteristics and principles of the diesel steam reforming reaction in honeycomb ceramics,and provided reasonable suggestions for the determination of operating conditions in the hydrogen production system and the optimization of the reactor.It has practical engineering significance.