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Composite biomass pellets (CBPs) are made from catkins, wood waste, and rice straw in China. This paper presents studies on the co-combustion of CBPs and coal by thermogravimetric analyzer and fluidized bed. The combustion parameters indicate that the co-combustion performance is improved gradually with the increase in CBP proportion. The interaction between coal and CBPs at high temperature is significant. The thermogravimetry and differential thermogravimetry (TG-DTG) curves shift toward a high temperature, and the decomposition process is delayed at high heating rates. The CBP blending ratio of 30% is considered the optimum ratio for coal and CBPs, in accordance with the minimum activation energy and slagging problem. The addition of CBPs can reduce the emission of polycyclic aromatic hydrocarbons (PAHs) and trace metals. The capture of trace metals is related to the alkali metals in ash, and the variation of PAHs is mainly attributed to combustion temperature and fuel properties. [ABSTRACT FROM AUTHOR]

In order to investigate heat transfer behaviour at an individual particle scale, the particle cooling process in a rectangular spouted bed is simulated by the Computational Fluid Dynamics-Discrete Element Method (CFD-DEM). As the inlet gas velocity increases, the gas-particle convective heat transfer in the jet region is intensified, while the convective heat transfer in the annular region is weakened. The inlet gas velocity also has an influence on the particle-particle conductive heat transfer. Particle-particle conductive heat transfer in the jet and fountain regions can both be enhanced by increasing inlet gas velocity, but this variation trend is opposite in the annular region. Additionally, the temperature distributions of particle and gas phases in the bed are also analyzed in detail. Compared with the infrared thermography experiment, the particle cooling process in the simulation results agrees closely with that in the experimental results. [ABSTRACT FROM AUTHOR]

Abstract: The characteristics of a fluidized bed electrode applied as a direct carbon fuel cell anode, which has an inner diameter of 35mm and height of 520mm and employed bamboo-based activated carbon (BB-AC) as a feedstock, are vigorously studied under various experimental conditions. The optimal performance of the fluidized bed electrode direct carbon fuel cell (FEBDCFC) anode with the BB-AC as a fuel is obtained under the following conditions with a limiting current density of 95.9mAcm−2: reaction temperature, 923K; N2 flow rate, 385mlmin−1; O2/CO2 flow rate, 10/20mlmin−1; nickel particle content, 30g; and a cylindrically curved nickel plate as a current collector. Under the same optimal conditions, the limiting current density of the FEBDCFC anode with oak wood-based activated carbon and activated carbon fiber as the fuel is determined to be 94.5 and 88.4mAcm−2, which is lower than that determined for BB-AC as the fuel. Comparatively, the limiting current density for graphite, which is utilized as the carbon fuel for this fuel cell system, could not be unequivocally determined because no plateau of the limiting current density against the overpotential is observed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A microwave-heated fluidized bed system was first built. • Further improving the efficiency of the CFP of biomass and bio-oil quality. • The pyrolysis characteristics of different catalysts and biomass ratios was studied. • Hierarchical micro-mesoporous catalyst has strong regeneration ability. To improve the efficiency of the catalyst fast pyrolysis (CFP) of rice husk and the quality of bio-oil, we integrate both microwave heating and fluidized bed reactor methods and build a microwave-heated fluidized bed system. In this study, the liquid yield from the CFP of rice husk in a microwave-heated fluidized bed (55.3 wt.%) is significantly higher than that obtained from a fixed bed (47.6 wt.%). Meanwhile, the relative content of hydrocarbons from microwave assisted catalytic fast pyrolysis (MACFP) of rice husk (RH) over a hierarchical micro-mesoporous composite molecular sieve (HM-2.0 T) is 67.6 % higher than that (51.6 %) of the organic base modified HZSM-5 (HT-2.0) and HZSM-5 (40.2 %) in the microwave-heated fluidized bed system. Furthermore, we focused on the ratio of biomass to catalyst in CFP processing and discover that the increased amount of catalyst promoted the decarbonylation and decarboxylation reactions, producing more hydrocarbon compounds, however, the excessive amount of catalyst does not contribution to higher monocyclic aromatic hydrocarbon selectivity. Besides, the hierarchical micro-mesoporous composite catalyst had strong regeneration ability and reusability. The selectivity of monocyclic aromatics remained high when the regeneration times increase from 1 to 4, which provided possibilities for applications of hierarchical micro-mesoporous composite catalyst in industrial production in the future. [ABSTRACT FROM AUTHOR]

The present paper studied the mixing characteristics of biomass and sands in a fluidized bed. A three dimensional model is calculated on the basis of computational fluid dynamics (CFD) and the discrete element method (DEM), while the lab-scale experiments under similar conditions are conducted. To investigate the mixing behavior of biomass and sands, particle distribution, particles time averaged kinetic motion and the Lacey index are analyzed and the effects of gas velocity and biomass size are discussed. Gas velocity provides the basic motion for particle movement and biomass particles gain a lot more kinetic motion than sands due to their large size. The biomass mixing process in a horizontal direction is more sensitive to gas velocity than in a vertical direction. Biomass size could slightly affect the mixing quality and a well mixing in fluidized bed could be reached if the size of biomass to sands is smaller than 4 times. [ABSTRACT FROM AUTHOR]

Based on the improved computational fluid dynamics and discrete element method (CFD-DEM), heat transfer and two-component flow of biomass and quartz sand have been studied from experiments and numerical simulation in this paper. During experiments, the particle temperature and moving images are respectively recorded by infrared thermal imager and high speed camera. With the increase of the velocity, the mixing index (MI) and the cooling rate of the particles are rising. Due to larger heat capacity and mass, the temperature of biomass drops slower than that of quartz sand. Fictitious element method is employed to solve the incompatibility of the traditional CFD-DEM where the cylindrical biomass are considered as an aggregation of numerous fictitious sphere particles arranged in certain sequence. By the comparison of data collected by infrared thermal imager and the simulated results, it can be concluded that experimental data is basically agreement with numerical simulation results. Directly affected by inflow air (25℃), the average temperature of particles in the bed height area (h >30 mm) is about 3 degrees lower than that of the other heights. When the superficial gas velocity is larger, the fluidization is good, and the gas temperature distribution is more uniform in the whole area. On the contrary, bubbles are not easy to produce and the fluidization is restricted at lower superficial gas velocity. Gas-solid heat transfer mainly exists under the bed height of 10 mm, and decreases rapidly on fluidized bed height. The mixing index (MI) is employed to quantitatively discuss the mixing effectiveness, which first rises accelerate, then rising speed decreases, finally tends to a upper limit. [ABSTRACT FROM AUTHOR]

Abstract: An experimental study on air gasification of polypropylene was conducted in a fluidized bed gasifier with an insider diameter (i.d.) of 100mm and a height of 4.2m. The effect of the equivalence ratio, bed height and fluidization velocity on various gasification results, including the product yield distribution, gas composition, gas heating value and gas yield were studied. The equivalence ratio appeared to have a significant effect on the reactor temperature and other gasification results. The increase of the equivalence ratio favored the formation of the fuel gas and decreased the formation of the tars and char. The decrease in the hydrocarbons content and, therefore, the gas heating value with an increase in the equivalence ratio were also observed. Both the bed height and the fluidization velocity seemed to have a small influence on the gasification results. The results obtained so far indicated that fluidized bed gasification of polypropylene with air could produce a fuel gas with a calorific value in the range of 5.2–11.4MJ/Nm3 and low tars content, which could be used in many end use applications. [Copyright &y& Elsevier]