Fluidized Bed Research Articles

A CFD and experimental study of hydrodynamic and heat transfer behavior in ribbed fluidized beds

Abstract The study focuses on enhancing the performance of fluidized bed systems, which are widely used in industrial processes requiring efficient heat and mass transfer. By integrating ribs at angles of 135, 150, and 165° on the riser wall, the research assesses their impact on hydrodynamic behavior and heat transfer using CFD simulations. The simulations, confirmed through experimental data, revealed that the 150° ribbed model outperforms others by improving particle mixing and achieving the highest heat transfer coefficient. The investigation also covered static pressure, solid volume fraction, and particle velocities at different bed heights (30, 60, 90, and 120 mm), showing that ribbed models significantly enhance turbulence and particle distribution, with the 150° ribs providing a balance between dynamic mixing and stable flow.

Acoustic emission and machine learning algorithms for particle size analysis in gas-solid fluidized bed reactors

In this work, a combination of an acoustic emission (AE) technique and a machine learning (ML) algorithm (Random Forest (RF) and Gradient Boosting Regressor (GBR)) is developed to characterize the particle size distribution in gas-solid fluidized bed reactors. A theoretical approach to explain the generation of acoustic emission signal in gas-solid flows is presented. An AE signal is generated in gas-solid fluidized beds due to the collision and friction between fluidized particles as well as between particles and the bed inner wall. The generated AE signal is in the form of an elastic wave with frequencies >100 KHz and it propagates through the gas-solid mixture. An inversion algorithm is used to extract the information about the particle size starting from the energy of the AE signal. The advantages of this AE technique are that it is a cheap, sensitive, non-intrusive, radiation-free, suitable for on-line measurements. Combining this AE technique with ML algorithms is beneficial for applications to industrial settings, reducing the cost of signal post-processing. Experiments were conducted in a pseudo-2D flat fluidized bed with four glass bead samples, with sizes ranging from 100 μm to 710 μm. AE signals were recorded with a sampling frequency of 5 MHz. The AE signal post-processing and data preparation for the ML process are explained. For the ML process, the AE frequency, AE energy and particle collision velocity data sets were divided into training (60%), cross-validation (20%) and test sets (20%). Two ensemble ML approaches, namely Random Forest and Gradient Boosting Regressor, are applied to predict particle sizes based on the AE signal features. The combination of these two models results in a coefficient of determination (R2) value greater than 0.9504.

Experimental Study of Agglomeration Formation during Co-Combustion of Coal and Palm Kernel Shell in Fluidized Bed

Abstract Co-combustion of biomass and coal in Indonesia power plants are a key element of the path towards achieving net-zero emissions. However, introducing biomass into a coal-boiler furnace may pose operational challenges. Therefore, this study aims to assess the potential of agglomeration when mixing biomass with a fluidized bed boiler. Complementation simulation tests were conducted by combining coal with various fractions of palm kernel shell (PKS) in a furnace capacity of 5kWth maintained at 850°C within an hour. The initial fuel was 100% coal, gradually increasing the biomass mixture by 5%, 10%, 15%, 20%, and 25%. The results indicated that de-fluidization occurred at 25% of the biomass mixture and to prevent agglomeration, the temperature of the bed was kept below 850°C. The agglomeration test of coal and PKS mixtures was successfully performed in a 5kW lab-scale facility, and the result will be useful for predicting agglomeration phenomena in power plants.

Performance Estimation of Self-Circulating Fluidized Bed Gasification with mixtures of Biomass

Performance Estimation of Self-Circulating Fluidized Bed Gasification with mixtures of Biomass

Numerical simulation of granular heat transfer within lifter rotating drum using smoothed particle hydrodynamics (SPH)

Abstract The rotating drums are typical industrial thermal processing equipment, which is widely used to heat or cool material particles in the circle fluid bed (CFB) systems. The traditional cylindrical rotating drum cannot significantly promote the heat transfer process of granules in operation, largely limiting further application. In this research, using smoothed particle hydrodynamics (SPH), two different types of lifters are employed to investigate the effects of shape, size, and number of lifters on the coefficient of heat transfer within the rotating drums by combining the flow and mixing characteristics of particles, the stress distribution, the transient velocity and temperature distribution, and the trend of the Peclet number.

Changes in flavor profile of vegetable seasonings by innovative drying technologies: A review.

Seasonings like garlic, ginger, and scallion provide spicy and masking flavor or aroma in vegetables. However, the method or technique used for drying these spices can affect the flavor profile. Therefore, this review focuses on vegetable seasonings like ginger, garlic, and scallion, the characteristic flavor of fresh and dehydrated vegetable seasoning, and how drying methods (freeze-drying [FD], convective hot air drying [HAD], infrared drying, microwave drying [MW]), and other recent dryers (swirling fluidized bed [SFB], pulsed-vacuum dryer, relative humidity-convective dryer, etc.) affect the flavor profile of the common vegetable seasonings. HAD increases α-zingiberene, reduces gingerol, and forms β-citral and citral in fresh ginger. FD increased sesquiterpenes, retained terpenoids, sulfides, and other volatiles in fresh ginger, and did not produce new volatile compounds (VOCs) in garlic. SFB drying better preserves 6-gingerol than FD and HAD. MW increases trisulfides and cyclic sulfur compounds in garlic. In general, drying, especially thermal drying reduces the VOCs in fresh garlic, ginger, and scallion and causes the formation of new VOCs.

Steady-state and dynamic simulation of gas phase polyethylene process

Gas-phase polyethylene (PE) processes are among the most important methods for PE production. A deeper understanding of the process characteristics and dynamic behavior, such as properties of PE and reactor stability, holds substantial interest for both academic researchers and industries. In this study, both steady-state and dynamic models for a gas-phase polyethylene process are established as a simulation platform, which can be used to study a variety of operation tasks for commercial solution polyethylene processes, such as new product development, process control and real-time optimization. The copolymerization kinetic parameters are fitted by industrial data. Additionally, a multi-reactor series model is developed to characterize the temperature distribution within the fluidized bed reactor. The accuracy in predicting melt index and density of the polymer, and the dynamic behavior of the developed models are verified by real plant data. Moreover, the dynamic simulation platform is applied to compare four practical control schemes for reactor temperature by a series of simulation experiments, since temperature control is important in industrial production. The results reveal that all four schemes effectively track the setpoint temperature. However, only the demineralized water temperature cascade control demonstrates excellent performance in handling disturbances from both the recycle gas subsystem and the heat exchange subsystem.

Magnetic reduction of gas back-mixing in bubbling fluidized beds with Geldart-B magnetizable particles

This study investigated the performance of magnetic fields in reducing gas back-mixing in bubbling fluidized beds with Geldart-B magnetizable particles. The Peclet number (Pe) and axial dispersion coefficient (Da,g) were determined using the one-dimensional dispersion model. A weak magnetic field reduced gas back-mixing to a certain extent, while a moderate field resulted in minimal decrease. The performance of a strong magnetic field varied significantly depending on the operation mode. Under the magnetization-FIRST operation mode, gas back-mixing was significantly reduced. The corresponding Pe and Da,g were calculated as ∼76 and ∼3.6 × 10−4 m2/s, indicating that the gas flow approached the ideal plug-flow manner. However, when the magnetization-LAST operation mode was used, the strong magnetic field failed to mitigate gas back-mixing. Therefore, the performance of magnetic fields in reducing gas back-mixing depended not only on their intensity but also on their application sequence to the gas flow field.

Development of a circulating fluidized bed for a 100 kg/day waste plastic pyrolysis-combustion system

The aim of this study was to develop a 100 kg/day plastic waste pyrolysis-combustion circulating fluidized bed (CFB) system. The CFB was designed to provide heat from the combustor (semi-riser type) to the pyrolyzer (bubbling fluidized bed (BFB)) through heat carriers in high efficiency. A 100 kg/day scale system, including an oil condensation facility, was constructed and operated continuously for 34.5 hrs. Pelletized polypropylene was supplied to the pyrolyzer as plastic waste. The temperature in the pyrolyzer and plastic feeding rate were experimental variables. The weight percentage of low (C1–C12) and middle (C13–C22) carbon number components of the produced oil in CFB operated at 512-551 °C was 65.3 and 23.2 %, respectively. These were significantly higher than 34.6 and 28.4 % of the BFBs with similar temperatures previously, implying that the heat transfer in the CFB was more intense than that in the BFB. Compared to the BFB, only subtle differences in the pyrolysis gas yield was observed for CFB, which signified that the gas mixing between two reactors was minimized during the operation. Although no blockage was found in the CFB, clogging of condensers and pipelines occurred during low-temperature operation owing to the relatively low pour point of the product oil. The results in this study provide detailed and practical information on the temperature, pressure, product gas, oil, and clogging issues to better understand plastic pyrolysis in CFB.

Harnessing the Energy Potential and Value-Added Products from the Treatment of Sugarcane Vinasse: Maximizing Methane Production Through Co-Digestion with Sugarcane Molasses and Enhanced Organic Loading.

This study assessed the impact of organic loading rate (OLR) on methane (CH4) production in the anaerobic co-digestion (AcoD) of sugarcane vinasse and molasses (SVM) (1:1 ratio) within a thermophilic fluidized bed reactor (AFBR). The OLR ranged from 5 to 27.5kg COD.m-3.d-1, with a fixed hydraulic retention time (HRT) of 24h. Organic matter removal varied from 56 to 84%, peaking at an OLR of 5kg COD.m-3.d-1. Maximum CH4 yield (MY) (272.6 mL CH4.g-1CODrem) occurred at an OLR of 7.5kg COD.m-3.d-1, while the highest CH4 production rate (MPR) (4.0L CH4.L-1.d-1) and energy potential (E.P.) (250.5 kJ.d-1) were observed at an OLR of 20kg COD.m-3.d-1. The AFBR exhibited stability across all OLR. At 22.5kg COD.m-3.d-1, a decrease in MY indicated methanogenesis imbalance and inhibitory organic compound accumulation. OLR influenced microbial populations, with Firmicutes and Thermotogota constituting 43.9% at 7.5kg COD.m-3.d-1, and Firmicutes dominating (52.7%) at 27.5kg COD.m-3.d-1. Methanosarcina (38.9%) and hydrogenotrophic Methanothermobacter (37.6%) were the prevalent archaea at 7.5kg COD.m-3.d-1 and 27.5kg COD.m-3.d-1, respectively. Therefore, this study demonstrates that the organic loading rate significantly influences the efficiency of methane production and the stability of microbial communities during the anaerobic co-digestion of sugarcane vinasse and molasses, indicating that optimized conditions can maximize energy yield and maintain methanogenic balance.

DEVELOPMENT OF INNOVATIVE TECHNOLOGY AND HARDENING EQUIPMENT FOR THE IMPLEMENTATION OF HARDENING HEAT TREATMENT OF METAL PRODUCTS USING FLUIDIZED BULK MATERIALS (PART 1)

Statement of the problem. One of the main problems faced by a modern enterprise is the search for ways to improve the efficiency of its activities. For the effective functioning of the thermal units of toolmaking industries, the simultaneous availability of heating and quenching devices with different heating and cooling media is required. This explains the desire of manufacturers and scientists to find technological, cheap, environmentally friendly heating and cooling media that can provide the required heat treatment parameters and high quality of the processed parts. The purpose of the article is to analyze the state-of-the-art of hardening thermal (combined) treatment methods using bulk materials as media for volumetric heating and forced cooling of metal products and the design and technological features of hardening devices that can ensure a rational structural state of metal parts of complex geometric shapes with a minimum level of their warping and deformation on the example of using vibro-fluidized bulk materials (in the technical literature, the term vibro-gravity particles of heat is used). Research results. To analyze the results of tests of bulk materials as quenching media for high-alloy steel grades and their effect on the structure and properties of the metal in comparison with the traditional oil quenching regime. To consider the features of quenching devices that use mechanical vibration to produce vibro-s bulk material and the possibility of their use in the implementation of quenching modes (including isothermal) of steel products of complex geometric shapes. Conclusion. The use of fluidized bulk materials in industry as media for volumetric heating and hardening of metal products and the design of devices for their use has been investigated. The advantages of the fluidized bed cooling method for the effective implementation of hardening heat treatment regimes are determined. It is shown that this method of forced volumetric cooling of toolmaking products is rational in terms of various indicators. The structural and technological parameters of devices for its implementation are analyzed, which can consistently provide the required level of properties of alloyed and high-alloy tool steels with a minimum level of warping and deformation.

Colon-Specific Delivery of Naproxen Pellets for Rheumatoid Arthritis: Development, Optimization, and Evaluation Using a 3-Level Randomized Full Factorial Design

Rheumatoid arthritis (RA) is characterized by increased joint pain and stiffness, particularly in the morning, which requires medication for treatment. Our research described here was aimed to develop, evaluate, and optimize coated naproxen pellets for colon-specific delivery using the carboxymethyl Leucaena leucocephala gum for the chronotherapy of RA. The extrusion-spheronization process was used for the preparation of the pellets followed by coating in a fluidized bed processor with materials such as Eudragit® S 100 and L 100. An 11-run, 2-factor, 3-level, randomized full factorial design was used to analyze the impact on the responses by varying the levels of independent factors to obtain the optimized formulation. The drug release of all the formulation batches at the 4th hour varied from 1.24 to 17.22% in the upper gastrointestinal (GI) tract; while the release of the drug at the 10th hour varied from 76.87 to 98.39% at the colonic pH. Furthermore, it was observed that the optimized formulation exhibited an increased release of naproxen in the presence of cecal matter collected from rats. We suggest that the prepared optimized formulation of the coated pellets of naproxen shows promise for the chronotherapeutic treatment of early morning symptoms associated with RA.

Innovative high-performance and energy-positive Co-treatment of organic kitchen waste and domestic wastewater using a fluidized bed ceramic membrane bioreactor

The aim of the study was to efficiently treat organic kitchen waste (FW) and domestic wastewater (DWW) together in an anaerobic fluidized bed bioreactor equipped with a ceramic membrane (AnFCMBR) through a sustainable approach considering energy recovery. The system operated continuously for 519 days at room temperature, and different filtration fluxes (1.7 and 5 L/m2/h), hydraulic retention times (HRTs) (22 h and 7 h), and organic loading rate (OLRs) (0.46, 1.52, 3.42, 6.08 kg/m3.d) were tested. The amount of organic matter in DWW may be insufficient for feasible gas production, but this challenge can be resolved through the addition of food waste. Influent chemical oxygen demand (COD) of 500 ± 143 mg/L gradually increased to 2000 ± 196 mg/L by increasing the portion of FW. The COD removal ranged from 92 to 98% throughout the study, with the membrane and the cake layer contributing 5–8% to the performance. Average supernatant SMP and EPS concentrations increased from 5 ± 1 to 45 ± 5 mg COD/L and from 54 ± 7 to 254 ± 26 mg COD/g VSS, respectively, when the highest amount of FW was added to the synthetic wastewater. This significant increase in SMP and EPS concentrations due to the addition of FW negatively impacted the filtration performance. SRF and CST values also increased with rising OLR, especially with the supplementation of synthetic wastewater with FW.After FW started to be mixed with DWW, the methane production increased approximately 5.5 times. With the use of AnFCMBR for the co-treatment of FW and DWW, it is possible to achieve energy-positive treatment with high-quality effluent that can be reused for various applications, such as irrigation. The methane produced provided 12 times more energy than was needed to operate the bioreactor.This is the first study evaluating the co-treatment of FW and DWW in AnFCMBR under varying operational parameters.

Akışkan Yatak Kurutma Prosesi İçin Isı Pompalı Ön Isıtmanın Termoekonomik Analizi

Enerji verimliliği, küresel ısınma ve iklim değişikliği günümüzde üzerinde durulan en önemli konuların başında gelmektedir. Tüketilen enerjinin etkin ve verimli kullanımına ilişkin yeni tasarımlar yaparken de tasarımlarda kullanılacak yenilikçi ve verimli teknolojiler ekonomi ve çevresel olumsuz etkilerin azaltılmasına katkı sağlayacaktır. Bu çalışmada; tamamen gaz yakıcı bir cihazla çalışan döküm sektöründe kullanılan akışkan yataklı bir kum kurutma sistemine ısı pompası entegre edilerek doğalgaz tüketimi azaltılmaya ve bu sayede sistem kullanıcılarına doğrudan ve dolaylı kazanımlar yaratılmaya çalışılmıştır. Sudan suya çalışan ve çevre dostu R32 soğutucu akışkanı kullanılarak 20°C’deki ortam havasını 45°C’ye ön ısıtma yapacak şekilde tasarımı yapılan ısı pompası sisteminin performans katsayısı (COPIP) 3,88 olarak hesaplanmıştır. Isı pompası entegrasyonu sayesinde sistem yıllık 36.839,1 Nm3 doğalgaz tasarrufu gerçekleştirilecektir. Bu entegrasyon ile sistemin yıllık çalışma süresi, elektrik ve doğalgaz birim maliyetleri baz alınarak, işletmecisine 193.501,25 ₺/yıl mali tasarruf sağlayacağı öngörülmektedir. Sisteme entegre edilen ısı pompasının; ekipman ve kurulum fiyatı, güncel kur değeri ile yıllık mali tasarruf miktarı parametreleri dahilinde, sistemin amortisman süresi 1,50 yıl olarak hesaplanmıştır. Ayrıca sistemde kurulacak fotovoltaik paneller ile enerji üretilerek karbon emisyonunun azaltılabileceği ve yine fotovoltaik panellerin marifetiyle işletmeci firmaya ek bir gelir kalemi oluşturulabileceği de öngörülmektedir.

CFD modeling of gas–solid flow in a two‐stage jetting fluidized bed with an overflow standpipe

AbstractThe two‐fluid model–kinetic theory of granular flow (TFM–KTGF) model and the sub‐grid‐scale (SGS) model are used to conduct a three‐dimensional numerical simulation study on the hydrodynamic characteristics of a two‐stage fluidized bed with an integrated overflow pipe. Using various drag models, the gas–solid flows, bed expansions, pressure drop distributions, and equilibrium conditions in the two‐stage bed are compared, and the conditions for the formation of a stable overflow in the two‐stage bed are thoroughly investigated. In addition, during the simulation of the secondary distribution in the bed, the porous media model simulates the momentum loss caused by the redistribution plate to avoid the direct simulation of the redistribution plate, which requires extensive grid division work and calculation costs. This work can provide technical direction for the industrialization of one‐step coal to multistage fluidized bed natural gas technology.

A new approach to evaluate the overall heat transfer coefficient of a fluidized bed biomass pyrolyzer

The heat transfer characteristics of non-pretreated rice husk pyrolysis in a fluidized bed with alumina beads (500 μm - 590 μm) as bed material are studied. Assuming instantaneous heating of biomass to the reaction temperature, the effective overall heat transfer coefficient of the system (UA) is initially calculated based on the compositions of the collected products and reaction temperature. UA ranges from 0.82 to 2.95 W/K. This heat transfer coefficient study allows ad hoc product distributions to be predicted from theoretical bases. The effects of the biomass feeding rate (F) and the bed height (H/D) on UA values are also analyzed. Highest UA and specific heat of the pyrolysis reaction of −3.35 MJ/kg are found at F = 5 g/min and H/D = 1.0, where H/D is the largest and F is the lowest in the range studied. Upon feeding of the low thermal conductivity biomass, UA typically decreases. However, if the bed materials are limited, the fed biomass and its produced char act as an auxiliary heating medium to improve the effective heat transfer coefficient. High UA improves the efficiency of the pyrolysis reaction, but it decreases the bio-oil fraction in the product due to secondary decomposition.

Investigations into the flow dynamics of mixed biomass particles in a fluidized bed through Hilbert-Huang transformation and data-driven modelling

Flow dynamics of binary particles are investigated to realize the monitoring and optimization of fluidized beds. It is a challenge to accurately classify the mass fraction of mixed biomass, considering the limitations of existing techniques. The data collected from an electrostatic sensor array is analyzed. Cross correlation, empirical mode decomposition (EMD), Hilbert-Huang transform (HHT) are applied to process the signals. Under a higher mass fraction of the wood sawdust, the segregation behavior occurs, and the high energy region of HHT spectrum increases. Furthermore, two data-driven models are trained based on a hybrid wavelet scattering transform and bidirectional long short-term memory (ST-BiLSTM) network and a EMD and BiLSTM (EMD-BiLSTM) network to identify the mass fractions of the mixed biomass, with accuracies of 92% and 99%. The electrostatic sensing combined with the EMD-BiLSTM model is effective to classify the mass fraction of the mixed biomass.

Development of a CFD-DEM Model for a 1 MWth Chemical Looping Gasification Pilot Plant Using Biogenic Residues as Feedstock.

Chemical looping gasification (CLG) is a novel dual fluidized bed gasification process that enables the conversion of solid feedstocks to a nitrogen-free syngas through in situ air separation, avoiding a costly air separation unit. While there have been recent advances in experimental studies, modeling of CLG is almost exclusively restricted to lab-scale units or 1D models. In this study, a 3D CFD-DEM model of a 1 MWth fuel reactor for the conversion of solid biomass was developed. Due to the high computational demand of the DEM method, a coarse-grained approach was used in combination with a simplified reaction network. The hydrodynamics were modeled with an EMMS drag model. Simulations were conducted for two woody biomasses and wheat straw based on experimental data of a 1 MWth CLG reactor. The model was able to predict the pressure profile over the reactor accurately, with a mean error below 10%. Carbon conversion and oxygen carrier oxidation were in good agreement with the experimental data with mean deviations below 5%, while reasonable values below 8 mol % mean error were achieved for the gas composition. Discrepancies in the gas composition as well as temperature profile indicate that further work is needed in the pyrolysis step of the model.

Employing a multi-resonance microwave sensor for in-line moisture monitoring of fluidized bed agglomeration

Amorphous substances are relatively common in food industry and their characteristics depend highly on the moisture content. Process parameters are adjusted based on online measurements to control the product quality of the agglomerates. This leads to two major challenges: precise moisture content measurements of amorphous particles at (i) different temperatures and for (ii) a wide moisture content range.In this study two workflows (inline fluidized bed and conditioned fixed bed) calibration of microwave sensors are compared and it is shown that for fluidized beds inline calibration is necessary to achieve accurate moisture measurements. The application of the novel microwave sensor MW 4200 working at resonance frequencies of 2.3 and 5.6 GHz is described. The temperature influence on the measurement is investigated with measurements of a fixed particle bed. Rapid, reliable in-process moisture control at a wide range of moisture contents and temperatures for agglomeration in fluidized beds, with a mean relative accuracy of 82 %, is achieved. This technology improves productivity and precision in industrial operations, minimizes waste and optimizes energy usage.

Fluidization behavior of stirred gas–solid fluidized beds: A combined X-ray and CFD–DEM–IBM study

Stirred gas–solid fluidized bed reactors are commercially employed in polyolefin manufacturing, but the complex gas–solid contacting dynamics pose challenges in design, scale-up, and operation. In this study, the influence of agitation on the fluidization performance of Geldart B particles was investigated experimentally by X-ray imaging and pressure drop measurements and numerically by Computational Fluid Dynamics (CFD) - Discrete Element Method (DEM) - Immersed Boundary Method (IBM). The experimentally obtained minimum fluidization curve and time-averaged pressure drop show good qualitative agreement with the simulation results. Visual observations underscore that an increase in the angular velocity of the agitator results in reduced bubble size and improved bed homogeneity, as further evidenced by reduced pressure fluctuations. Furthermore, the simulations reveal that while the impeller enhances solids agitation, a proper design study is imperative, considering that static immersed bodies, such as the stirrer shaft, can adversely impact solids motion.