Spouted Bed Research Articles

Numerical and Experimental Study on the Particle Erosion and Gas-Particle Hydrodynamics in a Codirectional Swirling Spouted Bed

Numerical and Experimental Study on the Particle Erosion and Gas-Particle Hydrodynamics in a Codirectional Swirling Spouted Bed

From circular to square‐based section spouted beds: Scale‐up and design overview of a multistage thermal unit

AbstractThis work summarizes the results of several research projects to demonstrate the possibility of scaling‐up spouted beds by assembling a number of square‐based jet units. Cylindrical vessels with a bottom cone and parallelepiped ones with a frustum base do not differ to a large extent in terms of hydrodynamic features. The existing correlations can be used to predict these square‐based spouted beds. Spouted beds can be very reasonably described as well‐mixed reactors. By assembling several units, it is possible to approach a plug flow state for solids residence time distribution (RTD) in continuous processes. Spouting stability is fully reached when the modules do not interfere each other: this goal is obtained by positioning the downstream units at a certain lower level and having the solids move by overflow; placing internal vertical baffles between contiguous units is the solution. Two hydrodynamical models are proposed to describe single and multiple spouted beds; their predictions help in choosing the best geometrical configuration for the assemblage. A possible application of a multiple spouted bed reactor was envisaged for gasifying pelletized textile residues to generate syngas which can be directly used in situ as a co‐fuel. Two units were built: a single 0.2 m side square‐based spouted bed furnace and the consequent dual stage scale‐up apparatus suitable for an auto thermal process. In the bottom stage, four units work independently to run combustion/gasification of low‐quality solid residues, while the upper stage had a cascade of four modules to run pyrolysis/gasification of selected biomass and obtain valuable secondary products.

Impact of drying technique on umbu‐cajá pulp with the addition of probiotic culture: Optimization, cell viability, physicochemical, and functional properties

AbstractThis study aimed to assess the effects of spouted bed (SB) drying and freeze‐drying (FD) on the properties of probiotic umbu‐cajá pulp. The strain Bifidobacterium animalis ssp. lactis was employed to obtain this pulp. Initially, the study was conducted with two separate experimental designs, one for SB and another for FD, encompassing variables such as inlet temperature and concentrations of drying adjuvants (maltodextrin and inulin). This approach aimed to identify the most favorable conditions in terms of yield and cell viability. Both drying methods proved effective in preserving probiotic cells, with comparable viable cell counts (12 Log CFU g−1) and process yield of up to 30.68%. Additionally, FD exhibited advantages in preserving and increasing levels of bioactive compounds, including phenolics and carotenoids, in the final product. In contrast, SB drying stood out for retaining carotenoids and exhibiting lower degradation of ascorbic acid. In summary, this study demonstrated that both SB drying and FD are promising approaches in producing powders from probiotic umbu‐cajá pulp. However, the selection between the methods should be guided by specific production goals, considering the desired characteristics of the final product.

Mixing nanoparticles in a ProCell type spouted bed

Mixing nanoparticles is critical in various industries, including pharmaceuticals, solar, and nanotechnology. When different nanopowders are mixed, hetero-aggregates consisting of hetero-contacts are formed, facilitating the exchange of charge, mass and moments between particles of different materials. This research paper presents a novel approach for mixing nanoparticles using special spouted bed equipment to produce hetero-aggregates. The paper explores the potential of special spouted bed equipment for mixing nanoparticles. High-velocity opposed inlet air streams in this equipment result in high gas-solid contact efficiency and enhanced particle circulation, which contribute to the breakage of aggregates and promote the mixing process. The study investigates the aggregate breakage and mixing quality in produced hetero-aggregates. Experimental results demonstrate that the special spouted bed equipment enables efficient mixing of nanoparticles, leading to higher dispersion in hetero-aggregates with many hetero-contacts. The modified homogeneity of mixing method is utilized to quantify the mixing inside the single hetero-aggregates. Visual confirmation of the assessed values of mixing quality is provided by EDX spectral mapping.

Axial gas mixing in conical spouted beds with high density particles

Conical spouted beds operating with high-density particles (ρp > 2500 kg/m3) have recently gained attention because of their potential use as nuclear fuel coaters for next-generation nuclear reactors. In the literature, the number of axial gas mixing studies in conical and conical-cylindrical spouted beds is very limited and all axial mixing studies were carried out with relatively light particles (ρp ≤ 2500 kg/m3). Therefore, the objective of this study was to generate experimental data that can be used to explain the gas axial mixing behavior in conical spouted beds operating with both low- and high-density particles. Experiments were conducted in two (γ = 30°, 60°) conical spouted beds with three different types of particles: zirconia (ρp = 6050 kg/m3), zirconia toughened alumina (ρp = 3700 kg/m3) and glass beads (ρp = 2460 kg/m3). In order to be able to compare experimental data obtained at different conditions, a 1-D convection-diffusion gas mixing model originally developed by San José et al. (1995) was implemented to determine the axial dispersion coefficients. The results show that the axial dispersion coefficients range between 1.75×10−2 m2/s and 9.35×10−2 m2/s, increase with superficial gas velocity and are higher than the corresponding dispersion coefficients of fixed beds, lower than the dispersion coefficients of fluidized beds and in the same range with the cylindrical spouted beds reported in the literature. The corresponding Peclet numbers were in the range of 0.6–7.8 for all operating conditions and slightly higher Peclet numbers were obtained with glass beads indicating the relative importance gas convective transport over gas dispersion for light particles compared to heavy particles.

Mixing sub-micron particles in a ProCell type spouted bed

Mixing sub-micron particles of two different materials produce hetero-aggregates, which can exhibit innovative and superior properties over homo-aggregates of a single material. The present study investigates the hetero-aggregate formation from sub-micron particles in ProCell type spouted bed equipment. Sub-micron particles can exist in the form of homo-aggregates, clusters of particles of the same material that are held together by cohesive forces such as van der Waals forces. In the special spouted bed used, the inlet air velocities are significantly higher than in conventional fluidized beds and can be expected to exert an influence that promotes aggregate breakage and rearrangement. Indeed, by use of scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), it is shown that mixing is achieved at sub-agglomerate level. Region of interest with a size of 2.5 μm (which is more than double the size of the bigger primary particle) is found to be a reasonable scale to investigate the mixing of sub-micron sized particles in compressed wafers and also in single agglomerates (by a new method of quantification).

Health and Carcinogenic Risk Assessment of Exposure to by-Products of Photocatalytic Degradation of Toluene in a Spouted Bed Reactor with Porous and Non-Porous Draft Tube.

This study was performed to assessment the health and carcinogenic risk of exposure to by-products of photocatalytic degradation of toluene in a spouted bed reactor Equipped with porous and non-porous draft tube. For this purpose, titanium dioxide nanoparticles were used as photocatalysts and UV lamps as radiation sources. Degradation efficiency and CO2 selectivity were compared. By-products were also detected in three spouted bed reactors with and without a porous and non-porous draft tube. The results revealed that the degradation efficiency of toluene in the spouted bed reactor without a draft tube was 30.75%. The insertion of porous and non-porous draft tubes in the spouted bed reactor increased the degradation efficiency up to 54.88% and 47.63%, respectively. Meantime, CO2 selectivity decreased from 100% to 50.8% within 180 min irradiation time in the spouted bed reactor without draft tube, while in the spouted bed reactors with porous and non-porous draft tube maintained at 89.85% and 84.35%, respectively. Toluene and four by-products with carcinogenic and non-carcinogenic risk of 0.002176 and 182.2, respectively, were detected in the spouted bed reactors without draft tube. However, no by-products with carcinogenic risk were found in the spouted bed reactor with porous and non-porous draft tube. photocatalytic degradation of toluene in a spouted bed reactor without a draft tube produces by-products with health and carcinogenic risks. The insertion of a porous and non-porous draft tube in spouted bed reactors provided mineralization more complete than spouted bed reactor without a draft tube by reducing the dead zone and providing appropriate contact between the toluene, photocatalyst, and UV. Therefore, prevent the formation of dangerous and carcinogenic by-products.

Multiple field synergy mechanism of the desulfurization process in the intensified spouted beds

The semi-dry flue gas desulfurization process in the conventional spouted bed (CSB), integral multi-jet spouted bed (IMJSFB), spouted bed with longitudinal vortex generator (SB with LVG) and swirl blade nozzle (SB with SBN) was simulated using the multi fluid model. Meanwhile, the multiphase reaction system of intensified spouted beds was explored based on the field synergy theory. The analysis of the synergy angle among three fields of the gas phase velocity, temperature, and pressure in the spouted bed shows that adding intensification structures can effectively enhance the gas heat transfer and reduce the gas drag and pressure drop. The intensified spouted beds also had better synergy among the multiphase field of velocity, velocity gradient, and temperature gradient. The desulfurization efficiencies in the CSB, SB with LVG, IMJSFB, and SB with SBN were 77.75 %, 80.85 %, 87.97 %, and 88.81 %, respectively, and the promotion effects in descending order of SBN > multi-jets > LVG.

Effect of the novel combined internal devices on gas−solid flow behavior in spouted beds

To reduce the flow dead zone in spouted beds (SBs), a novel multi-jet–axial swirl blade spouted bed (MJ-ASB SB) is proposed. Experimental verification and simulation analyses of the MJ-ASB SB, a conventional SB (CSB), and an integral multi-jet spout-fluidized bed (IMJSFB) were carried out. The simulation results showed that the combined structure resulted in more powerful turbulence, better radial mixing of particles in the spouting and annulus regions, and improved the flow−field uniformity. The intensification factor of the MJ-ASB SB was more than 20%, which was better than that of the IMJSFB, and the enhancement factors of the gas and particle velocities were four and five times those of the IMJSFB, respectively. Optimal structural parameters were obtained by analyzing the different structural parameters of the novel internal devices, and it was found that particle fluidization in the MJ-ASB SB was best when the height ratio ξ was 3, the width ratio was 1.3 and the rotation was clockwise.

OPTIMIZING THE STRUCTURAL CHARACTERISTICS OF DRAFT TUBE IN A SPOUTED BED REACTOR FOR BEST PHOTOCATALYTIC DEGRADATION OF TOLUENE AND CO2 SELECTIVITY USING RESPONSE SURFACE METHODOLOGY

In this study, toluene degradation efficiency and carbon dioxide (CO2) selectivity in a spouted bed reactor with a porous draft tube were optimized using the response surface methodology. For this purpose, titanium dioxide (TiO2) was used as a catalyst for photocatalytic degradation of gaseous toluene in a dynamic mode under ultraviolet (UV) irradiation. The influence of draft tube parameters' (including height, diameter, gap, and porosity) on toluene degradation efficiency and CO2 selectivity (as the response variables) was investigated by central composite design. Analysis of variance (ANOVA) was applied to evaluate the significance of the variables' effects and the interaction between them. Results showed that maximum toluene degradation efficiency of 78.1 % and maximum CO2 selectivity of 88.7 % were obtained at 1.99 cm draft tube height, 1.3 cm draft tube diameter, 1.3 cm gap, and 60 % draft tube porosity. The highest F-values indicated that the gap is the most important variable affecting the toluene degradation efficiency and CO2 selectivity, while the draft tube diameter is the second important variable. The results of experiments at optimal levels of parameters with three replications showed a maximum toluene degradation efficiency of 78.8% (SD= 0.62) and maximum CO2 selectivity of 89.1 % (SD= 0.46). The study revealed that the spouted bed reactor with a porous draft tube has a good stability for volatile organic compounds (VOCs) degradation and mineralization.

Dynamic changes of non-volatile compounds and evaluation on umami during infrared assisted spouted bed drying of shiitake mushrooms

The present study was carried out to report the dynamic changes of non-volatile components and the evaluation on umami of shiitake mushrooms during infrared assisted spouted bed drying (IRSBD) under different temperatures (45, 50, 55, and 60 °C) and airflow speeds (7.0, 7.5, 8.0, and 8.5 m/s). In addition, the drying characteristics and dried product rehydration ratio of shiitake mushrooms were also analyzed. Results demonstrated that compared with airflow speeds, drying temperature has a more significant effect on the drying characteristics of shiitake mushroom during IRSBD. Of all the drying process, the contents of flavor nucleotides, organic acids (tartaric acid, malic acid, succinic acid and citric acid), free amino acids (Asp, Glu and Ser) and equivalent umami concentration (EUC) value of Shiitake mushrooms are constantly increasing. The contents of soluble sugar and free amino acids such as polyol, acetic acid and fumaric acid increased significantly in the early and middle stage of drying, while decreased in the late stage of drying. The increase of temperature and airflow speed have a positive effect on retaining the flavor components of dried products. The condition of IRSBD with 55 °C and 8.0–8.5 m/s airflow speed is suitable for the dehydration process of Shiitake mushrooms to maintain better dried samples structure and yield high quality dried products with rich flavor in industry. • IRSBD was used to improve dried Shiitake mushrooms product quality. • Non-volatile compounds of Shiitake mushrooms were dynamic changed during IRSBD. • 55 °C and 8.0–8.5 m/s airflow speed is suitable for yielding rich flavor product.

Experimental validation of the mechanistic scale-up methodology of gas–solid spouted beds using radioactive particle tracking (RPT)

The very high-temperature reactors (VHTRs) are highly ranked among candidates of Generation IV of nuclear reactors due to their high efficiency, safety, the resistance to proliferation, and reliability. The VHTRs are preferentially fuelled by Tristructural-isometric (TRISO) coated fuel particles which has fuel kernels of fissile material coated by four coating layers: a porous buffer pyrolysis carbon layer (buffer PyC), an inner dense pyrolysis carbon layer (IPyC), a silicon carbide layer (SiC) and an outer dense pyrolysis carbon layer (OPyC). The heart of the operation and safety of the VHTRs significantly depends on the reliability of the coating layers of TRISO particles to retain metallic and gaseous fission products within the particles. The technique used for coating TRISO particles are gas-solids spouted beds via chemical vapor deposition (CVD). Fabrication of high-quality low-defect TRISO fuel particles fuel at larger scale spouted beds is required to support the commercialization of the VHTRs. In this work, our new developed mechanistic scale-up methodology of gas-solids spouted beds based on matching the radial profile of gas-holdup has been demonstrated and validated using radioactive particle tracking (RPT). Two spouted beds of small and larger scales were used in the study. Three sets of conditions were carried out which include the conditions of the reference case in the large scale, conditions that provide similar gas holdup radial profile to that of the reference case and conditions that provided dissimilar gas holdup radial in the small-scale spouted beds. The results confirm the validation of the scale-up methodology in terms of the dimensionless values of the spout diameter, cumulative probability distribution of the solids particles penetration into the spout, fraction of cycle time in each region of the bed, the radial profiles of the dimensionless values of the root-mean-square particle velocities and solids eddy diffusivity. The results further advance the knowledge and understanding of the gas-solids spouted beds provide deeper insight into their solids dynamics and presenting important benchmarking data for validating computational fluid dynamics codes and models. At last, procedures are established for the implementation of the new scale-up methodology.

Experiment and CFD study on the hydrodynamics in novel internal-intensified spouted beds

To overcome the limitations of traditional spouted beds, two novel internal-intensified spouted beds were proposed: swirl-nozzle anticlockwise-axial-swirler (SNAAS) and swirl-nozzle clockwise-axial-swirler (SNCAS) spouted beds. The hydrodynamics of the novel internal-intensified, conventional, and swirl-nozzle spouted beds (SBs) were experimentally and numerically investigated. Adding internal-intensified structures could reduce the minimum spouting velocity and accelerate particle fluidization. The gas radial velocity in novel spouted beds with ξ = 3 is the largest, which is the optimal height ratio. Compared with conventional and swirl-nozzle SBs, adding novel internal-intensified structures can effectively promote the radial velocity of gas and particle, reduce the flow-dead zone in the bed, obtaining larger gas turbulent kinetic energy. The flow field uniformity of gas and particle within beds in descending order as SNCAS SB > SNAAS SB > swirl-nozzle SB > conventional SB. The enhancement factor I of flow field uniformity in novel internal-intensified SBs is 2 to 3 times that in the swirl-nozzle SB. Mesh of (a) Conventional SB, (b) Swirl-nozzle SB and (c) Swirl-nozzle axial-swirler SB. • Internal-intensified spouted beds were proposed by introducing axial swirler and swirl nozzle. • The minimum spouting velocity can be reduced by novel internal-intensified structures. • Internal-intensified improves gas-solid contact throughout the spouted bed. • The enhancement factor I in novel internal-intensified SBs is 2 to 3 times that in the swirl-nozzle SB.

Simulations of water vaporization in novel internal-intensified spouted beds: Multiphase-flow, heat and mass transfer

Novel internal-intensified spouted beds (SBs) with swirl-nozzle anticlockwise-axial-swirler (SNAAS) and swirl-nozzle clockwise-axial-swirler (SNCAS) were proposed to improve the shortcomings of conventional SBs. The water vaporization in novel internal-intensified, conventional and swirl-nozzle SBs was simulated and the multiphase flow behavior and interphase heat and mass transfer in process were analyzed. Simulation results show the co-swirling action of novel combined internal-intensified makes gas drive particles move helically upward around the axial-swirler. Therefore, compared with conventional and swirler-nozzle SBs, the radial slip velocity of gas–solid and gas–liquid in two novel SBs are larger, and the contact between gas–liquid-solid phases is more sufficient. The gas–liquid-solid three-phase temperature, water vaporization rate, and gas moisture content of two novel internal-intensified all reached the highest, indicating that novel combined internal-intensified structures are beneficial to promoting the interphase heat and mass transfer during the water vaporization process. The mass transfer enhancement factors of SNAAS and SNCAS structures are 1.91 and 1.36 times that of conventional SB, respectively.

Computational Fluid Dynamics–Discrete Element Method Studies on Dynamics and Segregation in Spouted Bed with Polydispersed Particles

Computational Fluid Dynamics–Discrete Element Method Studies on Dynamics and Segregation in Spouted Bed with Polydispersed Particles

CFD–DEM simulation of wet granular-fluid flows and heat transfer in an integral multi-jet spout-fluidized bed

The hydrodynamic and heat transfer characteristics of dry and wet particles in quasi-two-dimensional integral multi-jet spout-fluidized bed (IMJSFB) and conventional spouted bed (CSB) were numerically studied using Computational Fluid Dynamics-Discrete Element Method (CFD-DEM), where the effect of wet content of particles is realized by introducing the liquid bridge force. In addition, the agglomeration, particle mixing, circulation, collision and heat transfer of IMJSFB and CSB under different moisture content were quantitatively studied. It is found that with the increase of gas velocity, the circulation capacity of particles in both spouted beds increases first and then decreases, and particle circulation characteristics of IMJSFB are obviously better than those of CSB. The appropriate moisture content of particles is beneficial to enhance the heat transfer effect, and compared with CSB, IMJSSFB has more obvious advantages in dealing with wet particles. This study has important significance for the mixing and heat transfer of class D wet particles, which is less studied in fluidization technology, and provides theoretical and technical reference for the actual design and operation of spouted bed.

Non-conventional techniques for the extraction of antioxidant compounds and lycopene from industrial tomato pomace (Solanum lycopersicum L.) using spouted bed drying as a pre-treatment

This study aimed to use the non-conventional microwave-assisted extraction (MAE) and pressurized liquid extraction (PLE) techniques for recovering bioactive compounds from tomato pomace, a valuable agro-industrial waste. The raw material was previously dried using a spouted bed dryer and then submitted to extraction with green solvents. A response surface methodology (RSM) performed the optimization of MAE and PLE. Next, the yield and the antioxidant activity results were maximized, and the lycopene content of the optimum MAE and PLE extracts was assessed by high-performance liquid chromatography (HPLC). Additionally, a fraction of raw material was oven dried as a comparison. The PLE extract exhibited the highest antioxidant activity, whereas the MAE extract showed the highest lycopene content (59.66 µg lycopene/g extract), which represents a 66.93% lycopene recovery compared to a standard technique with acetone. The remarkable results show that the non-conventional drying and extraction techniques were effective in valorizing this neglected material.

CFD-DEM study of a spouted bed operating in dense-phase, transition, and jet-spouting regimes

Spouted beds have been extensively studied for various applications due to their cyclic solid motion and intimate gas-solid contact. However, there are some applications that need more vigorous contact and shorter residence time than those observed in conventional spouted beds, and in some cases a high accumulation of sticky materials can even cause bed blockage. An option to overcome these problems related to fluid dynamics is to operate in a dilute phase regime, known as jet spouted bed. However, fluid dynamics in this non-conventional regime is different in relation to the conventional one. In this work, the dynamics of glass spheres in a spouted bed operating in the conventional, transition and jet spouting regimes was investigated using the CFDDEM coupling approach. Simulated results of particle velocities and local bed voidages were compared to the experimental data under the same conditions. In addition, the effect of fluid dynamics regimes on the number of contacts, number of collisions, and intensity of collisions inside the equipment was also evaluated. The simulated results were found to be satisfactory to predict the experimental behavior of all regimes investigated. A higher particle collision/contact ratio was observed in the dilute phase regime, which makes it interesting to study jet spouted bed in operations in which the collisions between particles are more important than the slip.

Efficient Production of Dried Whole Peanut Fruits Based on Infrared Assisted Spouted Bed Drying.

The present study is designed to evaluate the effect of infrared assisted spouted bed drying (IR-SBD) on the product quality and energy consumption of whole peanut fruits (including peanut kernels and shells). The dehydration of whole peanuts by means of hot-air drying (HD) and infrared drying (ID) were used as the control groups, and the drying characteristics, energy consumption, microstructure, porosity, hardness and fatty acid content were compared. The results showed that, compared to HD and ID, IR-SBD could reduce the drying time by 40% and 33%, respectively, and reduced energy consumption by 66% and 32%, respectively. During the drying process, the structures of both the peanut shells and peanut kernels underwent significant deformation; specifically, the porosity gradually increased gradually. The maximum porosity value was obtained by the samples dried by means of IR-SBD. Under the three drying conditions, the hardness of the peanut shells first decreased and then increased, while the hardness of the peanut kernels showed a trend of first increasing, then decreasing and finally increasing. Compared to the fresh whole peanuts, the IR-SBD dried samples exhibited a 4.07% decrease in fatty acid. This study shows that IR-SBD is a suitable application for the dehydration process of whole peanuts for the purposes of achieving high-efficiency and -quality production in the industrial sector.

Spray coating of cellulose aerogel particles in a miniaturized spouted bed

Aim of this work is to apply protective and homogeneous shellac coating layers on the surface of hydrophilic open-pore cellulose aerogel particles with low densities ≤ 0.1 g/cm3 and high specific surface areas in the range of ~ 400–450 m2/g while keeping the aerogels’ microstructure intact during processing. For this purpose, an innovative miniaturized spouted bed setup was used. Successful process settings for application of enclosed films on aerogel surfaces without intrusion of coating material into the pores were determined. Precise control of coating layer thickness in the range of 10–50 µm was achieved due to variation of coating solution amount without agglomeration and clogging events occurring during processing. Comparison of bulk densities and specific surface areas before and after coating proved the intactness of the porous structure. Coating of particles loaded with vanillin led to controlled release, enhancing release half-life times from 20 to 1600 min. Overall, a successful strategy for coating of organic low-density aerogels was developed.