The motion mechanism and characteristic of bubble in a pseudo-2D tapered fluidized bed

The different carbon nanotube(CNT)particles(^(@)A and^(@)V)were bed materials in the pseudo-2D tapered fluidized bed(TFB)with/without a distributor.A detailed investigation of the motion mechanism of bubbles was carried out.The high-speed photography and image analysis techniques were used to study bubble characteristic and mixing behavior in the tapered angle of TFB without a distributor.The fractal analysis method was used to analyze the degree of particles movement.Results showed that an S-shaped motion trajectory of bubbles was captured in the bed of^(@)V particles.The population of observational bubbles in the bed of^(@)V particles was more than that of^(@)A particles,and the bubble size was smaller in the bed of^(@)V particles than that of^(@)A particles.The motion mechanism of bubbles had been shown to be related to bed materials and initial bed height in terms of analysis and comparison of bubble diameter,bubble aspect ratio and bubble shape factor.Importantly,compared to the TFB with a distributor,the TFB without a distributor had been proved to be beneficial to the CNT fluidization according to the study of bubble characteristic and the degree of the particle movement.Additionally,it was found that the mixing behavior of^(@)V particles was better than^(@)A particles in the tapered angle of TFB without a distributor.

The Ejffect of Vertical Internal Baffles on Fluidization Hydrodynamics and Grain Drying Characteristics

The effect of vertical internal baffles on the particle mixing and graindrying characteristics in a batch fluidized bed column is investigated. Experimental work wascarried out in a 3m high rectangular fluidized bed dryer of cross sectional area of 0.15 m x 0.61 mat different operating conditions using paddy, a group D particle, as the fluidizing material. Theresults of the study showed that the fluidized bed dryer system with vertical internal baffles gavebetter particle mixing effect in the bed of particles than that without vertical internal baffles.This is due to the fact that the vertical internal baffle act as gas bubble breakers by breaking upthe large gas bubbles into smaller ones. The smaller bubbles cause a more vigorous mixing in the bedof particles before finally erupting at the bed surface. This improves the contacting efficiencyand enhanced the heat and mass transfer of the fluidized bed system. Thus a higher drying rate wasobtained in the falling rate period because the higher contacting efficiency increases theevaporation rate at the particle surface. However, the drying rate in the diffusion region showslittle improvement because the moisture diffusivity does not depend on the contacting efficiency.The fluidized bed dryer with vertical internal baffles could therefore be used in the initial rapiddrying stage in a two stage drying strategy for paddy. The insertion of vertical internal bafflesinto a fluidized bed system improves the processing of Group D particles in a fluidized bed systemespecially if the system is large in scale.

Study on flow characteristics and phase holdup in a slurry bubble column coupled with mild agitation Author links open overlay panel

A pilot-scale experimental setup was constructed to investigate the effect of mild agitation on the bubble characteristics and phase holdup in a slurry bubble column.Mild agitation positively impacts the axial uniform distribution of solid holdup,though it shows insignificant influence on the radial distribution.In homogenous regime,mild agitation promotes the coalescence of bubbles,and the effect becomes stronger with increasing agitator speed.The mild agitation contributes to a decrease in bubble size in heterogeneous flow regime.Mild agitation presents a significant effect on the gas holdup by adjusting the bubble size and bubble motion trajectory.The modification was introduced to predict the gas holdup considering the effects of mild agitation,a necessary consideration for applications requiring mild agitation.This adapted model predicts gas holdup with a maximum error of 12.9%.

Size and Characteristic of Housing Bubbles in China's Major cities:1999-2010

There is some disagreement in the published literature regarding the definition and the measurement of housing bubbles in China. Extending the analytical framework of Black et al. （2006）, the present paper measures the housing bubbles of China＇s 35 major cities from the second quarter of 1999 to the second quarter of 2010. The results indicate that the housing bubbles in China＇s 35 major cities were relatively small in the sample interval, but the bubbles in eastern metropolises, such as Beijing, Shanghai, Shenzhen, Hangzhou and Ningbo, have been relatively big since 2005. The changing tendency of housing bubbles in most cities highly corresponds with the changes in real estate policies. This paper decomposes the housing bubbles of the 35 cities, and finds a great proportion of irrational bubbles rather than rational intrinsic bubbles generated by price speculation. Based on empirical analysis, this paper proposes policy recommendations for preventing the generation and expansion of housing bubbles.

Bubble behavior characteristics based on virtual binocular stereo vision

The three-dimensional(3D) behavior characteristics of bubble rising in gas-liquid two-phase flow are of great importance to study bubbly flow mechanism and guide engineering practice. Based on the dual-perspective imaging of virtual binocular stereo vision, the 3D behavior characteristics of bubbles in gas-liquid two-phase flow are studied in detail, which effectively increases the projection information of bubbles to acquire more accurate behavior features. In this paper, the variations of bubble equivalent diameter, volume, velocity and trajectory in the rising process are estimated, and the factors affecting bubble behavior characteristics are analyzed. It is shown that the method is real-time and valid, the equivalent diameter of the rising bubble in the stagnant water is periodically changed, and the crests and troughs in the equivalent diameter curve appear alternately. The bubble behavior characteristics as well as the spiral amplitude are affected by the orifice diameter and the gas volume flow.

Synergistic promotion of particulate matter reduction and production performance via adjusting electrochemical reactions in the zinc electrolysis industry

Heavy particulate matter (PM) pollution and high energy consumption are the bottlenecks of hydrometallurgy, especially in the electrolysis process. Therefore, an urgent need is to explore PM reduction methods with production performance co-benefits. This study presents three PM reduction methods based on controlling operating parameters, i.e., lowering electrolyte temperature, H2SO4 concentration, and current density of the cathode. The optimized conditions were also investigated using the response surface methodology to balance the PM reduction effect and Zn production. The results showed that lowering electrolyte temperature is the most efficient, with an 89.0% reduction in the PM generation flux (GFPM). Reducing H2SO4 concentration led to the minimum side effects on the current efficiency of Zn deposition (CEZn) or power consumption (PC). With the premise of non-deteriorating CEZn and PC, GFPM can be reduced by 86.3% at the optimal condition (electrolyte temperature = 295 K, H2SO4 = 110 g/L, current density = 373 A/m^(2)). In addition, the reduction mechanism was elucidated by comprehensively analyzing bubble characteristics, electrochemical reactions, and surface tension. Results showed that lower electrolyte temperature inhibited the oxygen evolution reaction (OER) and compressed gas volume. Lower H2SO4 concentration inhibited the hydrogen evolution reaction (HER) and reduced electrolyte surface tension. Lower current density inhibited both OER and HER by decreasing the reaction current. The inhibited gas evolutions reduced the microbubbles’ number and size, thereby reducing GFPM. These results may provide energy-efficient PM reduction methods and theoretical hints of exploring cleaner PM reduction approaches for industrial electrolysis.