Wenjun Duan

Hydrogen production via steam reforming of bio-oil model compounds over supported nickel catalysts

Abstract The steam reforming of four bio-oil model compounds (acetic acid, ethanol, acetone and phenol) was investigated over Ni-based catalysts supported on Al 2 O 3 modified by Mg, Ce or Co in this paper. The activation process can improve the catalytic activity with the change of high-valence Ni (Ni 2 O 3 , NiO) to low-valence Ni (Ni, NiO). Among these catalysts after activation, the Ce-Ni/Co catalyst showed the best catalytic activity for the steam reforming of all the four model compounds. After long-term experiment at 700 °C and the S/C ratio of 9, the Ce-Ni/Co catalyst still maintained excellent stability for the steam reforming of the simulated bio-oil (mixed by the four compounds with the equal masses). With CaO calcinated from calcium acetate as CO 2 sorbent, the catalytic steam reforming experiment combined with continuous in situ CO 2 adsorption was performed. With the comparison of the case without the adding of CO 2 sorbent, the hydrogen concentration was dramatically improved from 74.8% to 92.3%, with the CO 2 concentration obviously decreased from 19.90% to 1.88%.

Pyrolysis characteristics and kinetics of lignin derived from three agricultural wastes

With thermogravimetric analyzer, the pyrolysis characteristics of three kinds of lignin from agricultural wastes were studied under three heating rates (10, 20, and 40 K/min). The increase of heating rate could advance the final pyrolysis degree and the pyrolysis reaction rate. In the main pyrolysis region, the lignin samples of corn cob (CC) and peanut shell (PS) showed two peaks of reaction rate curves, yet three peaks for the pine cone (PC) lignin. With the model-free Starink methods, it was found in the previous sections of all the lignin samples, the E values changed widely, and yet in the last sections, the E values were fairly stable. With the model-fitting methods, the kinetic parameters of CC and PS showed a good consistency: both of the lignin pyrolysis processes fitted F1 model for Coats-Redfern method and F1.5 model for Horowitz-Metzger method, and the E values of the two lignin pyrolysis were fairly close; yet, the parameters of the pyrolysis process of the PC lignin obtained were different f...

Thermogravimetric analysis of the biomass pyrolysis with copper slag as heat carrier

Thermo gravimetric analysis experiments were carried out on pyrolysis of three kinds of biomasses by temperature programming method. Employed by thermogravimetric analyzer, the effects of the type of biomass and the ratio of copper slag addition on pyrolysis were studied. Biomass pyrolysis process can be divided into four stages, dehydration, pre-pyrolysis, pyrolysis and carbonization. The experimental yields in this paper were modeled by CH4, C2H6, C3H8, C2H4 and C3H6, considering first-order primary reaction and reactions of alkanes and alkenes. Copper slag is beneficial for biomass pyrolysis. With Coats–Redfern method, nonlinear regression of biomass catalytic pyrolysis showed that reaction mechanism of pyrolysis process confirms well with shrinking core model (A3). The kinetic parameters and equations were also calculated. Copper slag promotes both the primary reactions of biomass pyrolysis and the Cracking reactions of alkanes and alkenes, but it cannot decrease the activation energy effectively.

Syngas production through biomass/CO2 gasification using granulated blast furnace slag as heat carrier

The emerging technology of biomass/CO2 gasification to recover waste heat from granulated blast furnace (BF) slag for solving the energy crisis and relieving the greenhouse effect was proposed. The gasification performances of biomass/CO2 in granulated BF slag under different reaction temperatures and mole ratios of CO2 to fixed carbon in the biomass (CO2/C) were investigated, and the effects of granulated BF slag on the biomass/CO2 gasification reaction were illuminated. The results showed that with higher gas content, gas yield, and lower heating value (LHV) were obtained with higher reaction temperature. When CO2/C was up to 1, the maximum concentrations of CO and H2 were obtained, and the LHV was near maximum value. Granulated BF slag could promote biomass/CO2 gasification reactions to some degree and also could act as a catalyst in the reaction. Under the optimum conditions, a reaction temperature reaching 1000 °C, CO2/C of 1 and using granulated BF slag as a heat carrier, the maximum syngas concentr...

Particles Flow Behavior Around Tubes in Moving Bed

Moving bed has been widely used in the field of heat and mass transfer and reaction between solid particles and gas. In order to enhance the heat exchange coefficient, there will be tube banks inserted in the moving bed. In the process of drying ammoniates particles or heat recovery from high-temperature particles with moving bed, the particles flow behavior around the tube banks is significant. In this paper, the particles flow behavior around the tube banks is investigated, and all the results can provide guidance for the design and operation of a moving bed.

Flow Characteristic of Two-Phase Bubble Reactor for Slag Waste Heat Recovery

In order to recover the waste heat of molten blast furnace slag, a reactor with top-submerged lance was established. The numerical simulation and experiment study of the flow characteristic in the reactor were conducted. The mathematical model of reactor was established and the Euler-Euler model was employed to simulate the gas-liquid flow in molten slag bath. Meanwhile, the experiment results were obtained and compared with the simulation to testify the accuracy of the established model. According to the bubble behavior in bath, there were four stages: initial expansion stage, bubble detachment stage, freedom lift up stage and bubble broken stage. When the flow field in bath fully developed, the gas fraction decreased with the increasing of bath depth. During injection process, the area near the nozzle and lower the bath would first generate two symmetric heliciform flow regime, and then the flow regime in whole bath would become irregular because of bubble lifting up and rupturing. The gas fraction in bath, the average velocity and turbulence energy of slag would decrease before it increased to maximum and then it would keep fluctuate in a range.

Numerical Simulation and Optimization of Slag Bath Coal Gasification Reaction

Molten blast furnace slag(BFS) is a huge waste energy in iron and steel industry, the waste heat recovery of the molten BFS has attracted more and more attentions in recent years. A new process for generating hydrogen-enriched syngas by the coal gasification using molten BFS as heat carrier is built, based on this, numerical simulation of coal gasification reaction in the gasifier is carried out with finite rate/eddy dissipation model using ANSYS FLUENT, the distribution of gas components in the molten pool is analyzed and the effect of steam coal ratio(S/C) on the composition of syngas is investigated. At the same time, the coal gasification reaction process is optimized by using matrix analysis method based on orthogonal experiment. Results show that the main gas components in the molten pool are steam, H2, CO and CO2. The steam and CO in the molten pool are mainly distributed outside of the bubble, while H2 and CO2 are mainly distributed in the center of the bubble. Meanwhile, the high S/C ratio will reduce the content of CO in the syngas, which is not conducive to the process of coal gasification. After optimization, the gas holdup in the molten pool increases to 9.429%, the turbulent kinetic energy of molten BFS rises to 12.88x10-3m2/s2, and the splashing rate of molten BFS drops to 2.024. The flow of molten BFS and the mixing degree of gas-liquid phase in the molten pool are enhanced, and the effective composition and calorific value of outlet syngas are also improved.

Manganese-based catalyst for NO removal at low temperatures: thermodynamics analysis and experimental validation

Abstract Selective catalytic reduction of nitrogen oxides with loaded urea is a novel method for removing NO under excess oxygen and low temperature conditions. In present work, a comprehensive thermodynamic study for NO removal is executed based on the Gibbs free energy change. This research mainly includes the detailed analyses of NO removal mechanism, the feasibility analyses for manganese as the active element and the experimental study for synthesized manganese-based catalyst (preparation, characterization and performance test). The catalyst in present study can reach 82% NO conversion and near 98% N2 selectivity at 50 °C, which validates the correctness of the thermodynamic calculations.

Energy and exergy assessments of dehydrogenation of propane for propene production

ABSTRACT The energy and exergy assessments of the dehydrogenation of propane for propene production process were performed. The results show that when the reaction temperature rises from 400°C to 1000°C, the range of inlet and outlet exergy is 2268∼2376 and 2265∼2341 kJ/mol C3H6, respectively, and the range of exergy destruction is 6.31∼33.24, 9.93∼35.15 and 3.59∼31.99 kJ/mol C3H6 at 5, 25 and 45°C reference environment temperature, respectively. The range of exergy efficiency at discussed reference environment and reaction temperature is 98.52∼99.84%, and decreases with the increasing of reaction temperature and increases with the decreasing of reference environment.

Research on characteristics and modelling estimation of molten BF slag viscosity in the process of slag waste heat recovery

The object of this study was to explore the effects of basicity (CaO/SiO2 ratio), MgO and Al2O3 on viscosity and melting temperature of molten slag in the process of coal gasification with blast furnace (BF) slag as heat carrier to recover the waste heat. The results showed that the viscosity and melting temperature of BF slag decreased first and then increased with CaO/SiO2 ratio increasing, and the suitable CaO/SiO2 ratio was 1.10–1.20. Both viscosity and melting temperature increased with the increasing of MgO and Al2O3 in the slag, which should be lower than 8.22 and 11.00%, respectively. What is more, the viscosity estimation model for molten BF slag was established according to the Urbain model and experimental data of slag viscosity. In the model, the activation energy was calculated using slag compositions based on the redefine of material types in the slag, and the temperature was described by the Weymann–Frenkel equation. The viscosity of BF slag system estimated by proposed viscosity estimation model (modified Urbain model) fitted well with the experimental data and the mean deviation was about 17.98%.