A gas-liquid external-loop airlift reactor with a riser 0.47m in diameter and 2.5m in height and two externalloop down-comers 0.08m in diameter and 2.5m in height were used to investigate the gas-liquid two-phase flow structure. Local phase holdups were measured simultaneously by a microconductivity probe with air as the gas phase and water as the liquid phase over a wide range of operation conditions. Liquid flow velocity measurements were performed using the electrolyte tracer measurement (ETM) technique. The hydrodynamics near the sparger zone, riser disengagement zone (zone 1), junction zone (zone 2), and down-comer disengagement zone (zone 3) were systematically examined using the CFDs at the local scale and at the riser scale, respectively. The simulation results showed that zones 1, 2, and 3 exhibit three different flow regimes, which were the secondary mixed flow regime, the mixed flow regime, and the homogeneous bubble regime, respectively. It was also indicated that turbulent kinetic energy and turbulent kinetic energy dissipation rate were influenced by a gas sparger. These results were necessary to explain these different regimes using computational fluid dynamics (CFD) to provide deeper insight at the local scale for reactor geometry, such as gas sparger, junction and disengagement zones as well as the gas-liquid phase flow microstructure. The simulation results at the local scale were difficult to obtain by experiment. The numerical simulating results of local gas holdup and local gas and liquid velocities agreed well with the experimental data at a low gas flow rate. However, large errors occurred in the simulations at a high gas flow rate, because of poor estimation of the influence of bubble-induced turbulence or the higher density of the tracer and the poor mesh refinement. The flow structure and turbulence parameters of the phases presented here were useful for designing gasliquid external-loop airlift reactors.

Activated carbon fiber was oxidized through nitrocellulose combustion below 300℃ to introduce oxygen-complex on its surface. The pore structure, elemental composition, chemical functional groups of activated carbon fiber before and after oxidized were investigated. The result showed that the oxygen-complex could be efficiently introduced after nitrocellulose combustion; especially for the imide; and the micropore diameter was slightly wider after oxidization. It provided a simple method to introduce oxygen-complex using nitrocellulose combustion. The activated carbon fiber oxidized by nitrocellulose combustion displayed higher adsorption capacities for ammonia and carbon disulfide than that of the original activated carbon fiber due to the introduced oxygen-complexes.

Pyrolysis of oil sludge first by thermogravimetry/mass spectroscopy (TG/MS) and then in a horizontal quartz reactor with an electrical laboratory furnace under different pyrolysis conditions was carried out. The influence of heating rate from 5 to 20 °Câmin-1, final pyrolysis temperature from 400 to 700℃, various interval holding stage, and catalyst on the products were investigated in detail. The TG/MS results show that pyrolysis reaction of oil sludge starts at a low temperature of about 200℃, and the maximum evolution rate is observed between the temperatures of 350-500℃. A higher final pyrolysis temperature, an interval holding stage, and adding catalyst can promote the pyrolysis conversion (in terms of less solid residue production). In all parameters, an interval holding stage for 20 min near the peak temperature of 400℃ can enhance the yield of oil and improve its quality. Three additives used in this work as catalysts do not improve oil product quality markedly in spite of increasing pyrolysis conversion greatly.

The fly ash (high carbon content and high unreacted CaO) recirculation in CFB is a typical method to improve the carbon burnout efficiency and the calcium utilization ratio. While the effectiveness of it is limited by the resident time and the reactivity of the re-injected fly ash particles. In the present research, an improved fly ash recirculation method is suggested in which the CFB fly ash is mixed with water or the mixtures of additives (such as waste water of paper mill, cement, sodium silicate, and carbide slag) and water in a blender. Then, this mixture is re-injected into the combustion chamber of CFB by a sludge pump. Because the temperature in CFB is higher, the fly ash was flash hydrated. At the same time, it was dehydrated and agglomerated. The size of agglomerates is bigger than that of original particle and their attrition rate is lower. Therefore the resident time of agglomerates is much longer than that of fine fly ash particles. The absorption of SO2 is higher than that of original particles, too. This results in high carbon burnout efficiency. The hydrated lime also improves the calcium utilization.

Three types of SiO2 ultrafine particles were used to investigate the fluidization behavior in a fluidized bed with sound excitation. It has been shown that agglomerate size tends to reduce with an increase in sound pressure level. At a given sound pressure level, there exists a critical sound frequency (fc). Agglomerate size is decreased with increasing sound frequency as sound frequency less than fc. Whereas, agglomerate size intends to grow with an increase in sound frequency as sound frequency exceeds fc. A mathematic model to predict the agglomerate size has been developed based on energy balance between the agglomerate collision energy, the energy arising from sound wave, and cohesive energy. The model can predict qualitatively the effects of sound frequency and sound pressure level on agglomerate size.