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Copyright of Packaging & Food Machinery is the property of Packaging & Food Machinery Magazine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• The effects of various factors on fluidization characteristic were investigated. • The mean and standard deviation of pressure drop is affected by various factors. • The pressure fluctuation is attributed to bubble behavior. • The response surface method based on BBD is used to analyze the data. • The mathematical model of correlation coefficient is established. Fluidized bed flotation involves three phases of gas, liquid and solid, which can be used for the separation of coarse minerals. In this study, a two-dimensional gas–liquid-solid fluidized bed was developed to explore the fluidization characteristics of fluidized bed flotation. The effects of water velocity, air velocity, frother dosage and particle size (Q l , Q g , ρ n , D p) on the average pressure drop (–ΔP) and standard deviation (σ ΔP) were investigated. As the water velocity increases, the pressure drop initially increases, subsequently decreases and eventually remains constant. Increasing the air velocity will enhance the resistance of the bed to the water flow, resulting in a reduction in the water velocity required by peak pressure drop. Furthermore, the pressure drop is observed to decrease due to an increase in air velocity after reaching complete fluidization. Increasing the particle size has the opposite effect, while variations in frother dosage only influence the peak pressure drop. According to the bubble behavior, the influence of different conditions on the pressure drop fluctuation was analyzed. Increasing the water velocity, the frother dosage and the particle size contribute to a reduction in pressure drop fluctuation, whereas an increase in air velocity has the opposite effect. When the water velocity exceeds 1.2 L/min and the frother dosage exceeds 80 g/t, the pressure drop fluctuation is basically unchanged. Finally, the response surface methodology was used to analyze the interaction among the variables, and a mathematical model of the correlation coefficient was established to predict effects. [ABSTRACT FROM AUTHOR]

The pseudo-fluid characteristics of the gas–solid separation fluidized bed provide a set of feasible methods for the dry separation of coal. The equipment used in the development of dry separation technology is receiving increasing attention around the world, because it generates no pollution during the separation process. However, the industrial application of related technologies using multi-component, complex fluidization equipment has met with considerable resistance. In recent years, a series of advances and achievements has been made in the study of the structural design, fluidization characteristics, and coal separation performance of the gas–solid separation fluidized bed. With respect to the historical development of gas–solid separation fluidized equipment and related progress in basic theoretical research, this paper summarizes the recent developments of the common gas–solid fluidized bed, vibratory fluidized bed, and magnetically stable fluidized bed. We comprehensively investigate the factors influencing the fluidized bed, and identify some problems that must be addressed to further advance the large-scale industrialization of the gas–solid separation fluidized bed. [ABSTRACT FROM AUTHOR]

Triboelectric separation is an efficiency and promising method to recycle waste plastics. Fluidized bed has been proved an optimal tribocharger with excellent bipolar charging performance for binary granules. In this work, the tribo-charging characteristics of PE, PP, PET and PVC granules during fluidization were investigated using a bench-scale fluidized bed. The results showed that the triboelectric series obtained by fluidization charging was: (−)-PVC–PET–PP–PE-(+). The study of fluidization tribo-charge rate of plastics showed that the fluidization charge rate of five binary granule combinations was PE–PVC > PP–PVC > PE–PET > PP–PET > PET–PVC. And the saturated charge-to-mass ratio of five combinations shared the same trend with the tribo-charging rate. In addition, the tribo-charging and the separation characteristics of the ternary granules, namely PP, PET, and PVC were analyzed, and the results showed that PP plastics were mainly distributed near the negative plate, while PET and PVC were close to the positive one. [ABSTRACT FROM AUTHOR]

Mechanical agitation was usually applied to improve the fluidization quality of the fluidized bed. This study aimed to explore the effect of agitation on the fluidization characteristics and separation effect of a gas–solid separation fluidized bed. On the basis of the multiple reference frame model, the fluidized bed under mechanical agitation was simulated, where the symmetrical motion pattern of the bed particles was identified. Furthermore, when the agitation speed w was below 75 rpm, the fluidization quality was improved gradually with the lower density fluctuation variance of 0.06 g/cm3. Finally, under the appropriate operating conditions (fluidization number of 1.2, w = 75 rpm), raw coal was separated in a fluidized bed, and the yield of cleaned coal was 41.30% with an ash content of 14.27%. Moreover, the probable error was as low as 0.105 g/cm3, indicating the strong separation performance of the gas–solid separation fluidized bed with an agitator. [Display omitted] • Gas–solid separation fluidized bed with blade stirrer studied via CFD and experiments. • 3D model of a fluidized bed was established through CFD simulation. • Mechanical agitation effect on fluidization and separation verified experimentally. • Theoretical basis to promote gas–solid separation fluidized beds' industrial use. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Petrochemical Universities / Shiyou Huagong Gaodeng Xuexiao Xuebao is the property of Journal Editorial Department Of Liaoning Shihua University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The fluidization characteristics of binary Geldart D type particles in a vibrated gas-fluidized bed (VGFB) were studied deploying the collaborative measurement by impact force sensor and high-speed image analysis system. The synergistic effects of the operational parameters including vibration amplitude, vibration frequency and fluidizing air velocity on the fluidization characteristics of a VGFB were studied. The changing laws of bed pressure drop and particulate impact force were analyzed and confirmed macroscopically by the high-speed dynamic images. The results showed that the fluctuation range of the signals of pressure drop and particulate impact force decreases with the increase of fluidizing air velocity and bed height due to the energy dissipation of vibration and the increase of bed expansion ratio. Furthermore, the effects of bubbling behavior on the pressure drop and particulate impact force were revealed by the combination of the frequency domain analysis of signals and the high-speed dynamic image analysis. Image 1 • Impact force sensor was introduced to study the mechanical properties in the bed. • The effects of operational factors on fluidization characteristics were studied. • A comparative analysis of macro-image and frequency-domain image was introduced. • The law of bubble and slugging formation were verified by macro-analysis. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A continuous gas-solid fluidized bed with dynamic scrapers. • Inhibition mechanism of gas bubble generation by dynamic scrapers. • Effects of scraper distance and velocity on fluidization characteristics • Boundary effect of dynamic scrapers. Abstract Scrapers are important inner components in continuous fluidized beds in the state where they are most commonly used industry. Dynamic scrapers have significant effects on fluidization characteristics. A lab-scale continuous air dense medium fluidized bed (CADMFB) was designed, and the influences of operational parameters were studied. Moving scrapers lead to velocity gradients in the horizontal direction among magnetite particles in different bed heights, which assisted in loosening of the dense medium bed. Hence, bed pressure drop and minimum fluidization airflow rate were lower than those in beds with static scrapers. If the scraper velocity is kept constant, minimum fluidization airflow rate increases with increasing scraper distance. But the ratio of standard deviation to average bed pressure drop increases with the increase in the scraper distance, which indicates a decrease in bed stability. Minimum fluidization airflow rates also increased with increasing scraper velocities, but a fast scraper speed may also cause bed pressure fluctuations. Dynamic scrapers can inhibit the generation of big gas bubbles. Optimum scraper velocities for various scraper distances can be calculated by v > L g 0.6 π 0.2 1.43 Q 0.2 . Results indicate that 50 mm was the ideal scraper distance, and the optimum scraper velocity was about 0.35 m/s. Results also show that fluidization in boundary zones between dynamic scrapers and static sidewalls was worse than that of middle zones of CADMFB. [ABSTRACT FROM AUTHOR]

In recent years, the mild-hot gas-solid fluidized bed had a crucial influence on wet-in-feed sorting when it comes to moist feed (e.g., lignite) because of its expanding sorting range. To explain the favorable sorting effect of the mild-hot gas-solid fluidized bed, the fluidization characteristics (e.g., the pressure drop, density, etc.) was studied under different work conditions. In addition, a high-speed dynamic camera was used in this study to compare the slumping behavior of the magnetite slag at different temperatures. The optimum conditions for coal separation was also studied by Design-Expert software. It was shown that the bed temperature of the fluidized bed has a particular effect on its stability when the bed temperature was below 120 °C, which had a great influence on the separation. Finally, the probable deviation E of the mild-hot gas-solid fluidized bed under optimum operation conditions could be as low as 0.09 g/cm3 which showed the good separation ability. [ABSTRACT FROM AUTHOR]

Experimental and simulation approaches were combined to investigate the fluidization characteristics of a dense-medium gas–solid fluidized bed (DMGFB) for coal cleaning. Results indicated that the static bed height should be adjusted by maintaining a stable height of 150–300 mm to avoid its harmful effect on fluidization stability. Bed pressure drops presented favorable stability with slight fluctuations at a superficial gas velocity of 11.68 cm/s (1.6 U mf ). The uniform density distributions with slight variations throughout the whole bed were verified by comparing the experimental, simulated and calculated results. A fluidization index, U mb / U mf , was used to conduct stability-region analysis for DMGFB. On the basis of fluidization stability, a successive beneficiation flowsheet via a DMGFB separator was used to perform density-based separation of 6–50 mm sized run-of-mine coal. Results demonstrated that the low-ash clean coal with a yield of 61.36% was efficiently obtained with the ash content reduced from 39.64% to 10.18% and sulfur content rejected from 1.36% to 0.85%. Probable error E values were 0.06 and 0.075 g/cm 3 in high- and low-density separation stages, indicating efficient separation performance. The dry coal beneficiation technique has great potential for utilization in arid and water-deficient areas and countries. [ABSTRACT FROM AUTHOR]

Fine coal (3-1 mm) is between pulverized coal and particles that is suitable for traditional air dense medium fluidized bed. The addition of fine coal can thus affect bed fluidization and separation characteristics. To elucidate the bubble-driven mechanism, the fluidization characteristics, pressure fluctuation, separation/mixing efficiency of fine coal and fluidized bed density at different heights were investigated by varying number in an air dense medium fluidized bed using high-speed dynamic camera. Results show that bed density decreases while fluidization quality changed slightly with the addition of fine coal. With the increase of gas velocity, coal particles separate initially, then change into mixed state. Meanwhile, bed density changes at different heights. When fluidization number is in the range of 1.8 to 2.0, coal particles achieve a maximum separation efficiency. However, with the gas velocity further increases, the influence of air flow increases, and coal particles could not be separated according to fluidized bed density strictly. [ABSTRACT FROM AUTHOR]

This study numerically investigated the effects of water content and contact angle on the fluidization characteristics of wet particles in a spouted bed via the combination of computational fluid dynamics (CFD) and the discrete element method (DEM). As the water content increased from 0.01 to 1.00%, particle agglomeration occurred. Moreover, as the water content increased and the contact angle decreased, the particle velocity initially increased before decreasing. The results showed that when the contact angle was 30°, the particle flow improved. Furthermore, the larger the contact angle (within 15–60°), the closer the central temperature region was to the outlet of the spout region, and the greater the particle velocity fluctuation. Particle agglomeration occurred at the outlet of the spouted region, resulting in the particles in the spouted channel not being completely fluidized, hence reducing the granulation efficiency. The simulation results provide theoretical guidance for future reactor design. [Display omitted] • Spouted bed flow is simpler and more regular compared to standard fluidized bed. • Better grasp of particle agglomeration and flow characteristics is required. • Water content and contact angle influence the fluidization characteristics. • Computational fluid dynamics and discrete element method simulations were executed. • Simulation results provide theoretical guidance for future reactor designs. [ABSTRACT FROM AUTHOR]

The fluidization properties of binary particles in a supercritical water fluidized bed reactor (SCWFBR) are numerically investigated based on coupled Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) simulations. The accuracy and effectiveness of the CFD-DEM model is firstly validated via previously published experimental data. Then, the model is adopted to study the effect of flow velocities and sinusoidal pulse on the mixing of the binary particles. Numerical results show that it is effective to promote mixing of binary particles in SCWFBR by introducing external energy pulses, which cannot be achieved by simply increasing the flow velocities without pulses. Compared to high frequency pulses, low frequency pulses are more effective in promoting mixing. Within the parameters considered here, it is also found that the pulse amplitude is almost positively correlated with the effect on the promotion of particle mixing when it is smaller than the fixed flow velocity. In addition, an efficient and economical method based on Fast Fourier Transform (FFT) on the bed pressure drop is given to determine the optimal pulse frequency, which can prevent the waste of manpower and the physical resources from happening. This study can provide technical guidance to achieve optimal mixing of binary particles in SCWFBR and offer theoretical support for the design and optimization. [Display omitted] • Binary particle mixing in a SCWFBR can be promoted by introducing pulses is numerically confirmed. • Effects and mechanisms of pulse frequency and amplitude on promoting mixing are investigated. • A method based on FFT to find the optimal pulse frequency fast and economically is proposed. [ABSTRACT FROM AUTHOR]

Fluidization characteristics of the mixed magnetite and paigeite powder were studied by the combination approach of numerical simulation and experimental verification to optimize the design of the medium solids used in the dense gas-solid fluidized bed separator (DGSFBS). The experimental results showed that the favorable fluidization performance could be achieved with the weight proportion of paigeite powder in the mixture 25% ≤ α ≤ 35%, while the relative deviation in the bed density should be Δρ ≤ 0.025 g/cm3. The corresponding simulation results were obtained by selecting suitable mathematical models and parameters. It also indicated that the fluidized bed with mixed solids could provide a good fluidization performance and stable density distribution. The laboratory-scale DGSFBS was used to conduct the separation experiments on raw coal with size range of 13–6 mm and ash content of 33.43%. With the parameterα = 30%, the experiment resulted in the coal ash content being reduced from 33.43% to 11.63% with a probable error,EPof 0.07 and a recovery efficiency of 98.59%. Utilization of either magnetite or paigeite powder alone was not effective; however, fluidization performance and separation efficiency of DGSFBS improved with the utilization of mixed solids. [ABSTRACT FROM AUTHOR]

Continuous separation tests of fine coal particles of 6.0-0.5 mm were done by a crossflow air-solid magnetically stabilized fluidized bed (MSFB), which used 0.074-0.045 mm magnetite powder and magnetite beads as medium of high and low density separation respectively. The results show that the range of steadily operational air velocity in air-solid magnetically fluidized beds is broader than that in standard air-solid fluidized beds when they are at stable fluidization. External magnetic field compels the magnetic grains to form parallel magnetic chains following the magnetic induction lines, which enlarge the bed voidage and form the uniform air channels. Air bubbles cannot be produced when the air flows through the channels, thus stable and particulate air-solid magnetically fluidized beds coming into being. The possible deviation of high and low density separation are 0. 085 and 0. 075 g/cm³ respectively. [ABSTRACT FROM AUTHOR]

Abstract: Experimental measurements were conducted of the minimum fluidization velocities and the entrainment (terminal) velocities for beds of dry, digested wastewater sludge particles. With the use of air, experiments were performed in an 80 mm i.d. glass column with carefully sieved, very narrow fractions of particles in a wide range of 0.65–5.3 mm. Physical examinations of the dried sludge particles revealed their irregular, mostly isometric shapes, their porous character, and their fibrous nature. New correlations, which cover the transitional flow region, have been developed to estimate the conditions of incipient fluidization and those of entrainment for such peculiar materials. Their explicit forms also enable the direct computation of the particle size corresponding to a chosen terminal velocity and the straightforward calculation of the terminal velocity of a given, irregularly shaped particle. [Copyright &y& Elsevier]

The bed pressure drop, minimum fluidized gas velocity, bed density, and bed expansion rate are important parameters characterizing the fluidization characteristics of gas-solid fluidized beds. By analyzing these parameters, the advantages and disadvantages of the fluidization state can be known. In this study, experiments were conducted to study the fluidization characteristics of a gas-solid magnetically fluidized bed for microfine particles by changing the magnetic field strength, magnetic field addition sequence, and static bed height. The experimental results show that when the magnetic field strength increased from 0 KA/m to 5 KA/m, the minimum fluidized gas velocity of particles increased from 4.42 cm/s to 10.32 cm/s, while the bed pressure drop first increased and then decreased. When the magnetic field strength is less than 3.4 KA/m, the microfine particles in the bed are mainly acted on by the airflow; while when the magnetic field strength is greater than 3.4 KA/m, the microfine particles are mainly dominated by the magnetic field. The magnetic field addition sequence affects the fluidization quality of microfine particles. The fluidized bed with 'adding magnetic field first' shows a more stable fluidization state than 'adding magnetic field later'. Increasing of the static bed height reduces the bed expansion rate. The bed expansion rate is up to 112.5% at a static bed height of h0 = 40 mm and H = 5 KA/m. This will broaden the range of density regulation of a single magnetic particle and lay the advantage of gas-solid magnetically fluidized bed for microfine particles in the field of separation of fine coal. [ABSTRACT FROM AUTHOR]

• Fluidization characteristics of LC-GSFBR have been studied by CFD–DEM. • Compared with V*, Bo g increase is more likely to enhance agglomerate formation. • Stagnation zone is reflected from particle velocity increase in annulus region. • The variation of region distribution due to Bo g increase is complicated. The fluidization process within gas–solid fluidized bed reactor can be intensified by adding liquid, as it can enhance mass and heat transfer between gas phase and solid phase. With the help of computational fluid dynamics(CFD) and discrete element methods(DEM), fluidization characteristics are investigated at different liquid contents(V ^) and surface tension(Bo g). To be specific, the bed expansion ratio, particle concentration and particle velocity profiles are compared and analyzed. Numerical simulations show that Bo g should be less than 5 at V ^ = 0.013. At this recommended range, liquid addition makes interparticle force increase and has little effect on fluidization performance. From transient particle agglomeration behavior, the Bo g increase is more likely to enhance interparticle force, resulting in obvious particle agglomerations during fluidization process. The variation of stagnation zone height can be reflected from the abrupt increase of particle velocity in annulus region. It can be found that V ^ increase reduces particle velocity at critical height but Bo g increase is more likely to cause larger stagnation region. By analyzing the distribution of spout, annulus and fountain regions at different V ^ and Bo g , the annulus region expands with V ^ increase below the initial bed height while the spout region expands with Bo g increase. [ABSTRACT FROM AUTHOR]