Optimization of prismatic spouted bed apparatuses using novel experimental setup and discrete particle modelling

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Investigations on the spouting stability in a prismatic spouted bed and apparatus optimization

This paper deals especially with spouting stability in a slot-rectangular (prismatic) spouted bed. The flow stability was characterized by the pressure drop evaluation (the uniformity and amplitude of the fluctuations) and visual observations (the flow symmetry). The effect of several geometrical conditions, such as the inlet design, prismatic angle and draft plates on the bed behaviour was investigated for different particles and bed inventories exposed to different air flow rates. The prismatic angle was found to have a strong impact on the spouting characteristics. A method to improve significantly the spouting quality and to make the spouting stability independent on the gas inflow velocity is presented. Compared to the reference geometry the prismatic angle was changed to a higher value and the apparatus was equipped with draft plates. Whereas, to achieve a stable spouting in a wide range of the air flow rates the design of draft plates should be customized to the bed inventory. Dependent on the static bed height full or open-sided draft plates should be used. In the proposed apparatus implementation, the maximum spouting velocity was almost eliminated for large particles (Geldart D), i.e. a highly coherent dense spouting can pass continuously into the dilute-like stable regime, without stability loss at intermediate gas velocities. The spouting of Geldart B particles is also improved

Spout fluidized beds : recent advances in experimental and numerical studies

In the past few decades, the applicability of spout fluidized beds has been argumented immensely. This is not only due to the fact that these systems combine characteristics of spouted and fluidized beds but also to their efficacy to handle chemical transformations involving simultaneous heat and mass transfer in combination with varying particles size. This is important in applications such as granulation, coating, drying, pyrolysis and combustion etc. The present work aims at critically analyzing the recent advances in experimental and numerical studies of spout fluidized beds. Initially, the discussion will concentrate on experimental studies emphasizing variation of minimum spouting and spout-fluidizing velocity, operating pressure, mixing and jet-penetration length. Furthermore, flow regime maps will be discussed. Subsequently, the application of various numerical modeling strategies is highlighted. Also, recommendations are given for future work required in experimental and modeling studies

A study of heat transfer in fluidized beds using an integrated DIA/PIV/IR technique

A new measuring technique for studying heat transfer in gas–solid fluidized beds is proposed using infrared (IR) thermography. An infrared camera is coupled with a visual camera to simultaneously record images to give instantaneous thermal and hydrodynamic data of a pseudo 2D fluidized bed. The established techniques: digital image analysis (DIA) and particle image velocimetry (PIV) are combined with IR thermography to obtain combined quantitative (i.e. hydrodynamic and thermal) data sets. In this work, the calibration procedure and the methods that are used to combine the data obtained by the different techniques are discussed. The combined technique provides insightful information on the heat transfer in a fluidized bed for varying particle size, aspect ratio and background (or fluidization) gas velocity

A study of heat transfer in fluidized beds using an integrated DIA/PIV/IR technique

A new measuring technique for studying heat transfer in gas–solid fluidized beds is proposed using infrared (IR) thermography. An infrared camera is coupled with a visual camera to simultaneously record images to give instantaneous thermal and hydrodynamic data of a pseudo 2D fluidized bed. The established techniques: digital image analysis (DIA) and particle image velocimetry (PIV) are combined with IR thermography to obtain combined quantitative (i.e. hydrodynamic and thermal) data sets. In this work, the calibration procedure and the methods that are used to combine the data obtained by the different techniques are discussed. The combined technique provides insightful information on the heat transfer in a fluidized bed for varying particle size, aspect ratio and background (or fluidization) gas velocity

Characterization and CFD-DEM modelling of a prismatic spouted bed

In this study a prismatic spouted bed was characterized experimentally and modelled by means of 3D CFD-DEM simulations. The main focus was on the investigation of the influence of the gas flow rate on the bed dynamics and spouting stability. Pressure drop time series obtained at different gas velocities were used for the identification of flow regimes by means of the frequency domain and of chaotic properties such as the correlation dimension and Kolmogorov entropy. The gas and particle dynamics were investigated through simulations of different operational regimes: the spouting onset, as well as stable and instable regimes. A 3-D bed behaviour, typical for slot-rectangular beds, was found. A good agreement between simulations and experiments in the particle flow patterns, bed expansion and dynamics of characteristic gas pressure fluctuations was achieved. The particle dynamics as a function of the gas velocity was investigated for the entire bed. For one of the stable regimes, the bed regions showing different particle dynamics (spout, fountain and annulus) were characterized in detail. A regime map showing the stable operational window in dependence on an inlet-to-bed size ratio and gas velocity is also provided