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.

Sound-assisted fluidization of two kinds of SiO2 nanoparticles (having primary sizes of 5-10 nm) is investigated in this study. The two kinds of nanoparticles are SiO2 without any surface modification (NSM-SiO2) and SiO2 modified with an organic compound (SM-SiO2). The introduction of a 99.8-103.4 dB and 50 Hz acoustic field reduces the superficial minimum fluidization gas velocity, Umf,super, significantly for the two kinds of nanoparticles, and when the sound pressure level increases, the values of Umf,super decrease gradually. With the agitation of a 100 dB acoustic field, the SM-SiO2 nanoparticles could fluidize smoothly similar to Geldart-A particles over the frequency range of 40-60 Hz. NSM-SiO2 failed to fluidize so smoothly, but significant improvement was observed over such a frequency range. Different fluidization behavior, different bed expansion, and agglomerating behavior were also observed for the two kinds of nanoparticles, which indicate that the surface properties of nanoparticles have significant influences on their fluidization behaviors.

The pore size and volume of activated carbon fiber were increased by steam activation in the presence of iron or magnesium oxide; then, copper, cobalt and silver nitrate was loaded on it, respectively. The pore structures of activated carbon fibers were characterized by nitrogen adsorption (77.4 K); the morphologies and crystal styles of metal particles on surface of activated carbon fibers were observed by SEM and determined by XRD. The result showed that the pore diameter was widened after catalytic activation and the metal oxides were reduced during heat treatment. The adsorption capacity of dichloroethylene was increased with the pore size in 1-10nm; also, the loaded metal particles could markedly improve the adsorption property of dichloroethylene due to the chemical reaction between metal and chlorine atom.

A dry coating method via fine powder is used to improve the fluidization quality for cornstarch particles, belonging to the Geldart C group, which cannot fluidize normally. Two kinds of SiO2 fine powder are used to coat cornstarch particles. Both a conventional fluidized bed and a magnetic fluidized bed (MFB) are employed for the coating of cornstarch particles. The coating time ranges from 10 to 15 min in this study. The coated particles are observed via the scanning electron microscope (SEM) images. Furthermore, the fluidization behaviors of the coated particles are investigated. The results show that coating with fine SiO2 powder is an effective method to improve the fluidization quality of cohesive cornstarch particles. However, no significant difference in fluidization quality is observed between particles coated in a conventional fluidized bed and those coated in a MFB.

The fluidization behaviors of ultrafine particles were investigated in an acoustic fluidized bed with one type of micron particles and two types of nanoparticles. With the assistance of sound wave having low sound frequency and high sound pressure level, the micron and nanoparticles can be fluidized smoothly with fluidization behaviors similar to those of Geldart Group A particles. It has been found that increasing sound frequency leads to a reduction in minimum fluidization velocity, and then to an increase in minimum fluidization velocity. At the same sound frequency, the fluidization quality of nanoparticles improves significantly with increasing sound pressure level (100-103.4dB). In addition, a thorough investigation indicates that sound wave configuration have an influence on fluidization process of ultarfine particles. Experiments show that both Sine wave and Triangle wave can enhance fluidization quality of ultarfine particles.

The starch and cyclodextrin were selected as the precursors and the mixture of surfactant and tetraethyl orthosilicate (TEOS) as template to prepare mesoporous carbon. The result showed that a bimodal pore size distribution in mesoporous carbon derived from starch appeared; one was around 3.4nm and the other ranged from 3.8 to 16.2nm. However, there existed a concentrated pore size distribution from 3.2 to 4.2nm in mesoporous carbon derived from cyclodextrin. The different molecular structure of starch and cyclodextrin and their polymerization process in the presence of sulfur acid were responsible for the resulted mesoporous carbon structure; the starch could polymerize by head to head or side by side, but the cycleodextrin was only polymerized by head to head.