Development of Effective Voidage Correlations in Pilot-Scale Liquid–Solid Fluidized Bed Based on Data-Driven Modeling

Rates of mass transfer between a liquid and a surface which is axially immersed in fluidized beds are measured. Liquid-solid and gas-liquid-solid beds of both inert and active conducting particles are considered. Variables used in the experiments are liquid superficial velocity, particle size, and gas superficial velocity. The wall-to-liquid mass transfer coefficients in liquid-solid fluidized beds are increased with the liquid superficial velocity and particle size. The liquid holdup at which the maximum mass transfer occurs, is decreased with particle size. The mass transfer coefficients in gas-liquid-solid fluidized beds are slightly decreased with the gas superficial velocity. The mass transfer coefficients in terms of Chilton-Colburn factor can be well correlated with the modified Reynolds number.

Simulations of flow behavior of particles in a liquid-solid fluidized bed using a second-order moments model

A population model of quartzite particles in a lab-scale fluidized bed due to the thermal fragmentation

This paper presents a comprehensive study results on scale-up and biomass hold-up characteristics of biological fluidized bed reactors (BFBR). The overall objective of this study was to establish and test some basic design criteria for the scaling-up or scaling-down of anaerobic fluidized bed reactors. A 12.5 1 laboratory-scale fluidized bed was designed and constructed based on a geometrically similar 70 1 pilot scale fluidized bed and the process performances were compared. Biomass hold up characteristics of the BFBRs were also investigated during the experimental studies. A general expression was developed for predicting the biological fludized bed porosities. Using this expression, both the local and overall fluidized bed porosities could be predicted depending on biofilm thickness, expansion coefficient, media diameter and density. The validity of this expression was tested with the data from this study.

Mass transfer in fluidized beds is an important operation for separation processes. Two effects can be achieved by using fluidized beds in mass transfer processes increasing interface area and relative movement between the phases. These effects are both desirable because they lead to greater process rates. This paper presents an experimental investigation regarding mass transfer from the wall of a column to the fluid in a fluidized bed of inert spherical particles. The experiments were conducted in column 40 mm in diameter with spherical particles 0,8-3 mm in diameter and water as one fluidizing fluid. The method of dissolution of benzoic acid was used to provide very low mass flux. The average wall-to-fluid mass transfer coefficients were determined for two systems: single-phase fluid flow and a fluidized bed of inert particles The measurements encompassed a Reynolds number range from 100-4000 for single-phase flow and 600-4000 in fluidized beds. The mass transfer coefficients for both systems were calculated from weight loss of benzoic acid. The effects of superficial liquid velocity and particle diameter on the mass transfer coefficient were investigated. It was found that mass transfer was more intensive in the fluidized bed in comparison with single phase flow. The best conditions for mass transfer were reached at a minimum fluidization velocity, when the mass transfer coefficient had the greatest value. The experimental data were correlated in the form: jd = f(Re), where jd is the dimensionless mass transfer factor and Re the Reynolds number.

The overall objectives of this project are to develop experimental techniques for measuring the forces of fluidized particles, and to predict the solid-gas performance in fluidized beds by using data analysis system, and by elucidating the intrinsic mechanism of erosion and attrition phenomena in fluidized beds. The reduction of erosion and attrition rates is one of the critical engineering problems for the design and operation of fluidized bed combustors. Specifically, the objectives are to: (1) develop the experimental techniques to measure the forces of solid particles prevailing in fluidized beds: (2) measure and characterize the forces of solid particles in various types of fluidized beds with various configurations (conventional and spouted fluidized beds) and with different scales (10, 20, and 30cm) under various fluidization conditions (particle size, bed aspect ratio and gas velocity); (3) find and verify the mechanism of erosion rates of in-bed tubes and attrition rates of fluidized particles by forces of solid particles in fluidized beds. We developed three different kinds of measurement methods, i.e., fracture sensitive sensor, piezoelectric sensor and gas pressure fluctuation method. By using these methods the exact forces of solid particles, including the transient corporate in fluidized beds, were systematically measured. Simultaneously, the erosion rates of in-bed tubes and attrition rates of fluidized particles were measured. 69 figs., 9 tabs.

Axial mixing of fine particles in fluidized beds

Biomass energy has attracted considerable attention as a renewable and clean energy source that can be stored and transported effectively. A critical component in this context is the fluidized bed, which plays a vital role in biomass energy utilization. An in-depth understanding of the flow characteristics of non-spherical biomass particles within the fluidized bed is essential for improving energy efficiency. This study utilizes a combination of numerical simulations and experimental analysis to explore the flow patterns of biomass particles under eight distinct drag correlations. The investigation covers various flow regimes in the fluidized bed, concentrating on critical parameters such as flow evolution, gas-phase pressure distribution, particle phase velocity vectors, bed pressure drop, particle mixing characteristics, bed expansion height, and the energy-dynamic behavior of the particles. The results indicate that the Ergun resistance model closely matches the experimental data, particularly regarding the flow evolution of the particles. This model shows a more uniform mixing of the particles and greater stability in the magnitude and frequency of pressure fluctuations at the bed surface. This stability is reflected in the average pressure drop, highlighting the enhanced performance of the fluidized bed. Overall, this research sheds light on the intricate dynamics of non-spherical biomass particles in fluidized beds and provides valuable insights for optimizing particle design. By focusing on design enhancements, it is possible to achieve higher combustion efficiency, supporting the broader objective of sustainable energy utilization. In summary, this study emphasizes the significance of precise modeling and understanding of flow characteristics in the fluidized bed, which is crucial for advancing biomass energy technologies.

Collison of sand particles in fluidized bed plays a very important role in determining hydrodynamics of fluidized bed. Effect of coefficient of restitution on hydrodynamics on 300 µm particles in gas-solid fluidized bed was investigated. Eulerian-Eulerian model was used for simulating hydrodynamics of fluidized bed. For investigation, different values of coefficient of restitution which correspond to different values of elasticity of particles were used. No bubbles were found for perfectly elastic collisions. With decrease in the value of coefficient of restitution from 1 to 0.8, bubble formation shows a positive effect.

Gas–solid fluidized beds are complex particle systems, and the electrostatic behavior of particles in fluidized beds is even more complex, which is influenced by numerous factors such as particle properties and operating conditions. Current studies focus on the effect of a certain factor on particle charging without a global picture. Furthermore, there is no mathematical model that can describe the interaction of multiple factors on particle charging because it is difficult to build a model for such a complex system. Therefore, a new approach is needed. In this study, a model capable of accurately predicting the surface charge density of particles in monodispersed gas–solid fluidized beds within a certain range was developed based on the literature and experimental data through several machine learning methods including kernel ridge regression (KRR), support vector machine regression (SVR), and multilayer perceptron (MLP). SVR and MLP models gave the best results with R2 equal to 0.980 and 0.979, respectively. However, the sensitivity analysis showed that the MLP model was more reliable than the SVR model. In conclusion, the feasibility of using machine learning to analyze the charging behavior of particles in fluidized beds is demonstrated, and the proposed MLP model can serve as an accurate correlative tool for fast and effective estimation of particle surface charge density in gas–solid fluidized beds.

A technique has been developed to give a quantitative measure of the contacting efficiency of liquid feed onto particles in a hot fluidized bed for petroleum applications. Copper naphthenate was used as a tracer to measure the coating of atomized bitumen feed onto solid coke particles in a fluid coking pilot plant. The pilot plant consisted of a reactor vessel, where bitumen was injected into the reactor as feed, and a regeneration vessel, where coke particles were heated and circulated back to the reactor. Atomized bitumen droplets were injected through a feed nozzle into the reactor section. A small concentration of copper naphthenate tracer, pre-diluted with bitumen, was injected upstream of the nozzle, following a step function with time. As the bitumen reacted, the copper formed solid deposits on the surface of the particles, effectively labeling the particles that had been contacted by the bitumen droplets. Frequent coke samples from the solids exiting and entering the reactor were taken during and after the injection of the tracer.Two types of measurements were conducted on the coke samples; bulk copper concentration in the samples, using Inductively Coupled Plasma (ICP), and copper concentration on individual coke particles using energy-dispersive X-ray (EDX) analysis. The data for bulk copper concentration confirmed that the solids were mixed rapidly in the reactor, approximating a Continuous Stirred Tank Reactor (CSTR). The EDX analysis of individual coke particles demonstrated, however, that a significant fraction of the coke particles within the samples were not labeled with copper. This result indicated that many of the particles in the fluidized bed were not contacted by bitumen in the reactor. Consequently, the tracer technique was used to compare the coating efficiency of bitumen on coke particles by operation of different nozzle designs.

Pulsating flow effect on the segregation of binary particles in a gas–solid fluidized bed

Comparison of hydrodynamics and operational characteristics of a multistage fluidized bed with high-density and low-density powders

A technique for determining devolatilization rates of large coal particles in a fluidized bed combustor

Evaluating solids dispersion in fluidized beds of fine particles by gas backmixing experiments