The Chinese Journal of Process Engineering

An Experimental Study of Particle Flow Patterns in a Gas-Solid Separator with Cambered Surface for Cocurrent Downflow Reactors by PDPA

DU Lin;YAO-Jian-zhong;LIN Wei-gang

. 2003, 3(6): 481-485.

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The particle flow patterns in a gas-solid separator for cocurrent downflow reactors have been studied with a phase Doppler particle analyzer (PDPA), which allows the measurement of particle size and velocity simultaneously. Volumetric flux, particle size distribution and particle velocity vectors are obtained. It is found that the internal components including the rectangular nozzle, circular arc camber and baffles play important roles in the gas-solid separation process. Particles are separated from gas phase due to the gas-solid inertia difference and the collision between the particles and the internal components. Although volumetric flux has a wide distribution in the cross direction, particles are mainly concentrated near the camber surface. Due to turbulent dispersion and drag force in the cross direction, small particles gradually move away from the cambered surface, leading to double-peak distributions of particle size, which influences the collection efficiency of particles. By reducing nozzle width, separation efficiency can be improved.

Jet Regime and Double Jet Interaction in Gas-Solid Fluidized Beds

HONG Ruo-yu;GUO Qing-jie;ZHANG Ji-yu

. 2003, 3(6): 486-492.

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Experimental investigation and numerical simulation were conducted for a gas-solid fluidized bed with a single jet or double jets. The jet penetration heights in a 300 mm′51 mm two-dimensional fluidized bed were measured with pressure transducers. Numerical modeling and simulation was based on a two-fluid model with K-ε model for gas turbulence. Jet formation and detachment above jet nozzle, bubble ascending and coalescence in bed, and bubble burst on bed surface were visualized by computer simulation. It was found that the behavior of the double jet system could be classified into three categories: isolated jets, transitional jets, and interacting jets. The criterions of jet separation for those categories were proposed. Jet penetration correlations were also recommended for those categories.

Instability Analysis on Gas-Solid Two-phase Flow in the Standpipe under Negative Pressure Gradient

WEI Yao-dong;LIU Ren-huan;SUN Guo-gang;SHI Ming-xian

. 2003, 3(6): 493-497.

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The paper presents an experimental study on the instability behaviors of gas-solid two-phase flow in a f150 mm′11500 mm standpipe under negative pressure gradient. The gas-solid two-phase flow in the standpipe is characteristic of the flowing against negative pressure and slip velocity upward, which made flow instability of the gas-solid two-phase flow. There are two kinds of instability, one is the flowrate shift resulting from non-fluidization, the other is flowrate fluctuation resulting from compressed gas. Flowrate shift happened at the entrance or the exit of standpipe and the flowrate fluctuation occurred in any part of standpipe. The instability of gas-solid two-phase flow in the standpipe has potential harm to the operation of circulating fluidized beds.

Pressure Drop of Foaming Fluid Flow in Trickle Bed Reactors

LIU Guo-zhu;REN Yong-li;WANG Li;WANG Ya-quan;MI Zhen-tao

. 2003, 3(6): 498-504.

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Anthraquinone working solutions used in hydrogen peroxide manufacture were selected as the test system to investigate the properties of foaming fluid flow in the trickle bed reactor (TBR). By the analysis of the instantaneous pressure drop fluctuation a method was established to identify the flow patterns in TBR for foaming systems and used to investigate the effects of the factors such as gas and liquid flow rate, and packing particle size on the bed pressure gradient. The experimental data were correlated based on the empirical relationship reported by Specchia et al. Comparison between experimental data and estimation show that the regressed relationship of Specchia et al. can be used to predict the pressure gradient of foaming fluid flow in TBR with an accuracy of 5%.

A New Method for the Measurement of Solids Time-averaged Velocity in Gas-Solids Two Phase Flow

E Cheng-lin;LU Chun-xi;GAO Jin-sen;XU Chun-ming;SHI Ming-xian

. 2003, 3(6): 505-511.

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A new method for calculating time-averaged particle velocity was presented based on the cross- correlation technique. Compared with the other two calculating methods presented by Aguillon and Nieuwland, the new method considers not only the differences between the upward and downward particle element velocities and numbers, but also the differences of particle element concentrations. The measurement of particle time-averaged velocity was completed by using a PV4A optical fiber probe in a cold model set-up of circulating fluidized bed for the sake of ascertaining the differences between the new one and the others. The results show that the differences between them were negligible under higher superficial gas velocity and lower cross-sectional average particle concentration, while the differences were remarkable under lower superficial gas velocity and higher cross-sectional average particle concentration.

Improvement of g-ray Attenuation Technology in Measuring Density of Multiphase Flow

WEI Wei-sheng;ZHAO Zhi-xue;BAO Xiao-jun

. 2003, 3(6): 512-517.

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Several methods of improving measurement precision, other than traditional methods such as adopting a high activity ray source and prolonging sampling time, are presented. The attenuation law of the ray was discussed, and an amended mass absorption coefficient (m￠m) was suggested to make convenient use of this law. m￠m was almost independent of the ray intensity when the ray intensity was more than 100 Bq, but decreased evidently when the response frequency of the measurement system was low and the ray intensity was high, especially when the ray intensity was less than 100 Bq. Therefore, the response frequency and the ray intensity should be as high as possible to improve the measurement precision. It was found that m￠m did not depend on the object's thickness but on the location where the object was placed between the ray source and the detector. It can be concluded that in any cases, the closer the object to the detector, the less the m￠m. It was also found that the effect of object's location on m￠m was related to the area through which rays are entered to the detector, and this effect increased with the increase of the detector area. This is more evident when the object is near the detector or the ray source. The GTS-2000 measurement system was developed and used to measure not only ray intensity but also ray spectrum. By the aid of the ray spectrum obtained by GTS-2000, the gain of the measurement system could be easily adjusted to an optimum value and the up-threshold and down-threshold values of the single-energy rays could be easily selected before ray intensity was measured.

Kinetics of Seperating Magnesium Ions from Demagging Liquor of Phosphate Ore by Ion Exchange

WEN Yan-xuan;WANG Li-sheng;JIN Zuo-mei

. 2003, 3(6): 523-527.

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An integrating equation of moving boundary model was used to describe the kinetics with changing bulk concentration of removing Mg2+ from demagging waste solution of phosphate ore by 001′7 resins. The general kinetical equation was obtained. The ion exchange process of Mg2+ is controlled by ion diffusion through particles. The apparent activation energy is calculated to be 24.11 kJ/mol, and the apparent reaction order of Mg2+ is 1.0.

Compound Reflection Insulation Layer for Ladle

JIN Ke;SHEN Yun-wen;MENG Zhi-quan;LIANG Zhi-gang;MIU Xin-de;LI Feng;GAO De-man

. 2003, 3(6): 549-554.

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With regard to insulation layer and shell anti-corrosion insulation coating for ladle, oxyacetylene flame hot spraying nanometer Al2O3 coating (1), compound reflection insulation plate (2), spreading/putting insulation protecting coating (3) for the inner surface of ladle shell were studied and developed based on microscale heat transfer. Temperature drop of over 78~140℃ for outer wall of ladle, reduction of molten steel temperature drop and improvement of inner coating temperature were achieved.

Treatment of Acid Red A Wastewater in an Electrolytic-bioreactor

CAO Hong-bin;LI Yu-ping;CHEN Yan-li;ZHANG-yi

. 2003, 3(6): 570-575.

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An electrolytic bioreactor was devised to treat the wastewater containing Acid Red A (AR-A, 74 mg/L), and the effects of current density, anode materials, methanol concentration and chloride concentration were investigated. The results showed that AR-A could be simultaneously removed by electrochemical oxidization and microbial degradation with methanol as a co-substrate. When a current of 300 mA was applied across the electrolytic bioreactor and the influent CODCr was 740 mg/L, the removal of AR-A and CODCr was 79% and 84%, higher than those without DC current application (59% and 74%, respectively). The amounts of the AR-A and CODCr biodegraded by bacteria increased with the increase in the methanol concentration, due to the increase in the biodegradation rate and better tolerance of the bacteria in the biofilm to the electric field. The increase in chloride concentration and current density increased the observed AR-A removal rate, despite of the inhibition of the metabolism of bacteria in the biofilm by the hypochlorite ions produced from chloride by anodic oxidation. Fe anode was more efficient in treatment of the wastewater of AR-A compared with the graphite anode. However, more sediments were produced in the reactor.

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