Fluidized Bed Research Articles

Development of funnel-type fluidized bed reactor system using microcarriers for cultures of adherent cells

Development of funnel-type fluidized bed reactor system using microcarriers for cultures of adherent cells

Characterization of Particle Fluidization in a New Type of Fluidized Bed Flotation Unit

ABSTRACTUnderstanding the hydrodynamics of the bed layer in a fluidized bed is essential for optimizing and improving fluidized bed flotation units. This study proposes a fluidized bed flotation column that incorporates auxiliary particles into the gas–liquid two‐phase system to address the shortcomings of traditional flotation units. Stainless steel particles (glass beads), tap water, and compressed air were used as the solid, liquid, and gas phases, respectively. Key factors affecting the bed hydrodynamics (such as bed fluctuation, minimum fluidization velocity, bed expansion, and porosity) in the fluidized column include gas and liquid flow rates as well as the initial bed height. Experimental results show that selecting appropriate filling particles can effectively enhance the fluidization performance of the bed, while appropriately increasing the gas flow rate can achieve fluidization at lower liquid velocities, thus reducing energy consumption during the flotation mineralization process. Theoretical analysis combined with extensive data reveals that the expansion characteristics of the fluidized bed and the use of high‐density filling particles can effectively mitigate bed layer fluctuations and stabilize the flow field environment. Additionally, based on a wide range of data, this study employs model factor analysis, dimensionless analysis, and multiple linear regression analysis to propose a standard dimensionless parameter model for the fluidized bed flotation column, which can effectively predict bed layer fluctuations and expansion characteristics.

Study on the reaction mechanism and kinetics of limestone hydrogenation by micro fluidized bed: Effect of H2 concentration and natural limestone

Limestone decomposition is the first step in cement production, which produces a significant amount of CO2 and poses a significant challenge to achieve carbon neutrality. Hydrogenation of limestone can produce CO or CH4 instead of CO2, which can be considered as a new way of carbon capture, making it a promising method for carbon emission reduction. In this work, pure CaCO3 and several natural limestone samples were hydrolyzed under varying H2 concentration using a micro fluidized bed (MFB) reactor combined with online mass spectrometry to reveal the mechanism and kinetics of limestone hydrogenation.The main gases produced by hydrogenation at 1 atm are CO and CO2. The CO2 comes from the calcination of CaCO3. The CO comes from 2 steps: the first step is the in-situ hydrogenation of CaCO3 and the second step is the Reverse Water Gas Shift (RWGS) reaction. The activation energy (Ea) of CO2 formation in H2 atmosphere is lower than in Ar atmosphere. However, there is no obvious effect of different H2 concentrations on the Ea of CO2 formation. The Ea of CO in situ formation is 72.70 KJ/mol, 54.53 KJ/mol, 71.34 KJ/mol and 60.29 KJ/mol in 10%, 30%, 50% and 70% H2 atmosphere, respectively. The H2 concentration also has no significant effect on the in-situ CO evolution. However, the H2 concentration can affect the Ea of CO produced by RWGS. The Ea is 75.67 KJ/mol, 167.59 KJ/mol and 221.47 KJ/mol in 10%, 30% and 50% H2 atmosphere, and this reaction doesn't occur in 70% H2 atmosphere. Compared with the pure CaCO3, the hydrogenation of limestone can produce more CO and less CO2. In limestone, impurity elements are the main factor affecting the reaction kinetics. Transition metals can increase the rate of CO2 production, but have no apparent effect on CO. The CO2 yield of high impurity limestone is higher than that of limestone with low impurities. Transition metals can also reduce the Ea of CO2 formation and the RWGS reaction. In the 50% H2 atmosphere, the Ea of CO2 formation is 88.87 KJ/mol and the Ea of CO from RWGS is 137.60 KJ/mol. However, under the same conditions, the Ea of pure CaCO3 is 126.91 KJ/mol and 221.47 KJ/mol.

Homogeneous Crystallization of Nickel as Ni₃S₄ in a Fluidized Bed Reactor with Supersaturation Control

This study investigates the recovery of nickel sulfide (NiS) using fluidized bed homogeneous crystallization (FBHC), emphasizing the process from nucleation to crystallization. Sludge production in conventional chemical precipitation becomes a drawback in treating wastewater economically and efficiently. FBHC offers a promising alternative by minimizing sludge generation. The study examines various operational parameters, including hydraulic retention times (HRT), reflux ratio (R), initial nickel concentration, and static bed height (SBH), to optimize NiS recovery. Results show that FBHC achieves high total removal efficiency (TR) and crystallization ratio (CR), under the optimum condition of HRT = 15min, R = 8.3, initial nickel concentration = 147mg/L, and SBH = 35cm. The agglomeration of Ni(OH)2 was found to be crucial for the crystal growth during the surface oxidation of Ni3S4. This technological approach to wastewater treatment offers highly efficient heavy metal removal from wastewater.

Methanol and thiosulphate from pulp mill waste streams support denitrification under salinity stress

Methanol and thiosulphate are two common compounds found in pulp mill environment. In this study, for the first time, methanol driven, and thiosulphate driven denitrification under salinity stress were studied in fluidized bed bioreactors (FBBR) in a comparative manner. Concentration of salinity, due to Cl-, Na+, SO42- and K+ that are present in saline industrial wastewaters, and nitrate loading rate were gradually increased up to 8.1 % and 4.67 ± 0.30 gNO3--N/L/d to determine the reactors’ resistance and denitrification rate capacity. Moreover, the suitability of real pulp mill methanol-rich foul condensate as alternative electron donor was revealed in the heterotrophic reactor. With foul condensate, heterotrophic denitrification maintained > 97 % nitrate removal at a rate of 2.40 ± 0.10 gNO3--N/L/d under 6.8 % salinity, also decreasing nitrite accumulation as compared to pure methanol. Thiosulphate driven autotrophic denitrification showed lower salinity and nitrate loading tolerance than the methanol driven, removing nitrate > 97 % at salinity up to 5.6 % and rate of 1.27 ± 0.10 gNO3--N/L/d. Microbial community composition in the heterotrophic reactor remained stable at different salinities, with denitrifying genera Methylovorus, Paracoccus and Pseudomonas playing the major roles. On the other hand, in the thiosulphate driven reactor, inoculated with a pure culture of Thiobacillus denitrificans, many other microorganisms, including Moheibacter, became enriched. However, nitrate removal was mainly linked with T. denitrificans abundance as indicated by decreasing share of the community co-occurring with the decrease of the reactors’ performance. In summary, this study showed that thiosulphate and foul condensate supported denitrification under salinity stress, indicating potential for high-rate fluidized bed pre-treatment for nitrate removal from pulp mill NOx-SO2 scrubber wastewater prior to direction to subsequent activated sludge process.

Experiment investigation and multiscale modeling of biomass oxidative fast pyrolysis in a fluidized bed reactor

Experiments were conducted in a fluidized bed reactor to study the oxidative fast pyrolysis of biomass. The pressure drops along the bed height were measured, and the yield and composition of gas, liquid, and solid products were analyzed at various O2 concentrations. It was found that with the increase in oxygen concentration, the yield of biogas increased, especially CO2 and CO, while yields of bio-oil and biochar decreased. Under oxidative conditions, the fraction of tar in bio-oil was significantly reduced. A multiscale model was developed in the open-source code MFiX by integrating the reactor model based on the coarse-grained DEM-CFD, the intraparticle model, and the biomass oxidative fast pyrolysis kinetics. The model was verified by comparison with experimental data. As the oxygen concentration increases, the mixing and separation of biomass particles decreases, the residence time increases, the axial distribution moves upward, and the Lacey mixing index decreases. This study established experimental and theoretical foundations for designing and scaling up oxidative fast pyrolysis of biomass in fluidized beds.

Hydrodynamic and reaction kinetic responses of CaO/CaCO3 carbonation in bubbling fluidized bed reactors for thermochemical energy storage: Influence of CO2 mole fraction, grain size, and reactor dimensions

The CaO/CaCO3 thermochemical energy storage system offers a promising method for the efficient utilization of solar energy. However, the reactor design remains underdeveloped. In this study, the Eulerian-Eulerian two-fluid model is employed to systematically investigate the effects of CO2 mole fraction, particle size, and reactor dimensions on the carbonation process in a bubbling fluidized bed reactor. Increasing the CO2 mole fraction from 50 % to 80 % reduces the duration of the chemical-reaction-kinetics controlled stage from 118.5 s to 65.3 s, and the transition stage from 64.6 s to 36.7 s, with minimal impact on the final conversion rate. High CO2 concentrations cause insufficient bed fluidization and uneven local conversion rate distribution within the bed. As the grain size increases from 150 nm to 300 nm and 600 nm, the duration of the chemical-reaction-kinetics controlled stage decreases from 118.5 s to 104.0 s and 76.2 s, respectively. This causes the reaction to enter the transition phase earlier, ultimately leading to a reduction in the maximum conversion rate. Altering the height and width of the reactor does not significantly impact the conversion processes within the reactor. These findings provide valuable insights for the optimization and practical industrial application of efficient reactors.

Quantification of Amlodipine Maleate Content in Amorphous Solid Dispersions Produced by Fluidized Bed Granulation Using Process Analytical Technology Tools

Background: Active pharmaceutical ingredient (API) content is a critical quality attribute (CQA) of amorphous solid dispersions (ASDs) prepared by spraying a solution of APIs and polymers onto the excipients in fluid bed granulator. This study presents four methods for quantifying API content during ASD preparation. Methods: Raman and three near-infrared (NIR) process analysers were utilized to develop methods for API quantification. Four partial least squares (PLS) models were developed using measurements from three granulation batches, with an additional batch used to evaluate model predictability. Models performance was assessed using metrics such as root mean square error of prediction (RMSEP), root mean square error of cross-validation (RMSECV), residual prediction deviation (RPD), and others. Results: Off-line and at-line NIR models were identified as suitable for process control applications. Additionally, at-line Raman measurements effectively predicted the endpoint of the spraying phase. Conclusions: To the best of authors’ knowledge, this is the first study focused on monitoring API content during fluidized bed granulation (FBG) used for ASD preparation. The findings provide novel insights into the application of Raman and NIR process analysers with PLS modelling for monitoring and controlling ASD preparation processes.

Design and operation of a demonstration plant for fluidized bed low-temperature gasification of alternative fuels applied to cement production

A fluidized bed low-temperature gasification technology for solid waste treatment is proposed, which provides an effective solution for energy saving and carbon reduction in the cement industry. A demonstration plant was designed and constructed, which is a fluidized bed low-temperature gasifier coupled to the calciner, capable of treating more than 4,000 kg/h of solid waste. The project involved detailed equipment configuration to ensure stable operation. Commissioning tests for rice husk and textile waste gasification assessed system reliability and gasification performance, with a thermal substitution rate (TSR) of 53.10 % for the calciner. At the same time, targeting a clinker production capacity of 2500 t/d, the gasification plant could achieve an annual net profit of at least 753,100 USD. The fluidized bed low-temperature gasification technology not only has a good economic and environmental value for the use of alternative fuels in the cement production process, but also is important for the design and operation of industrial-scale gasifiers and for numerical modeling.

Influence of oxygen transfer performance on nitrogen metabolism and microbial community structure in an aerobic fluidized bed biofilm reactor under different aeration aperture

Influence of oxygen transfer performance on nitrogen metabolism and microbial community structure in an aerobic fluidized bed biofilm reactor under different aeration aperture

Preliminary CFD simulations of a lab-scale novel design of a particle receiver for CSP applications

In the present work, a preliminary CFD analysis of a novel design of particle receiver for CSP applications was performed. The particle receiver is a new lab-scale prototype consisting in a thin fluidized bed in which the walls are made of glass to permit thermal radiation to pass through. The working fluid is air and the thermal performance has been studied for the case in which i) only gas flows through the receiver (no particles) and ii) particles are placed in the receiver. The addition of the particles enhances the heating process by increasing the heat transfer coefficient from the heated wall to both the bed of particles and the gas resulting in an increase of more than 55% in the air temperature at the outlet of the receiver. Then, the bed dynamics have been studied in detailed as a function of the superficial gas velocity and the static bed height of the system. The analysis comprises the time evolution of the temperature of the gas and solid phases, the position of the centre of mass (that can be increased by more than 25% during the heating process) and the bubble characteristics. It has been found that when the gas velocity is increased by 66% the average temperature of the solids is only decreased 10%; while, for the static bed height, when the number of particles is increased 3 times the average temperature of the particles is increased by 18%.

Eco-optimized experimental and computational analysis of coarse wood chips fluidization aerodynamics in bed reactors

In this study, computational particle fluid dynamics (CPFD) simulations optimized the aerodynamic properties of wood chips which are a key biomass fuel for sustainable power generation by the addressing of challenges in fluidization. Using both fixed and bubbling fluidized beds, the study focused on particle adhesion and agglomeration, which cause channeling and voids, thus reducing gas-particle contact. Additionally, solid bridges or agglomerates from uneven bed distribution were shown to decrease fluidization efficiency and heat transfer. Coarse particles (2–2.5 mm) were selected to establish the optimal operational range for effective fluidization. Reducing particle aggregation and adhesion through collisions promoted a uniform distribution, enhanced thermal energy storage and stabilizing bed temperature, and benefited in combustion control in green chemical engineering applications. The commercial CPFD software Barracuda was used for simulations at an inlet pressure of 300 Pa above atmospheric and an atmospheric outlet pressure. These simulations provided good insight into wood chip fluidization behavior by the establishment of operating parameters for fluidized bed reactors and were validated using a lab-scale model with consistent parameters. This study concludes that wood chip fluidization can be represented in distinct operating zones and clarifies optimal design considerations for reactors suited to biomass combustion. These findings significantly advance the understanding of wood chip aerodynamics by giving a sustainable fuel option for efficient thermal energy production.

Nanoporous microparticles of cellulose nanofibrils: The effect of fluid bed atmospheric spray freeze drying

Cellulose nanofibers are abundant, low-cost, biodegradable and non-toxic materials that are a technological alternative for products in pharmaceutical field. The aim of this study was to investigate the effect of fluid bed atmospheric spray freeze drying on cellulose nanofibers characteristics, and compare to conventional spray and freeze drying methods. The atmospheric spray freeze dried nanofibers had moisture content of 2.3 %, mean size 4.0 μm, circularity of 0.86 and angle of repose of 27.3°. Also, solid state evaluation of atmospheric spray freeze dried cellulose nanofibers and other samples showed very similar chemical and thermal characteristics, but a relative crystallinity of 45.3 %, similar to spray dried powders. Furthermore, the most important feature of atmospheric-spray-freeze-dried cellulose nanofibers is their morphology, since unlike the other methods those resulted in highly nanoporous structures. The atmospheric-spray-freeze-drying of cellulose nanofibers may become a new and attractive alternative for the preparation of microsponges for pharmaceutical applications.

Study on Drying Characteristics of combined microwave-hot air drying of Paddy

Combining microwave drying with traditional hot-air drying can significantly enhance drying efficiency and uniformity owing to its unique internal heating characteristics, making it suitable for drying fresh paddy susceptible to mold. In this study, a fresh paddy was dried using a microwave fluidized-bed dryer to investigate the drying characteristics and assess the influence of microwave power, microwave duration, hot-air temperature, air velocity, and tempering time ratio. Key parameters, including drying rate, moisture diffusion coefficient, moisture transfer coefficient, activation energy, thermal efficiency, and specific energy consumption, were calculated. The results indicated that increasing microwave power and hot-air temperature significantly reduced drying time, achieving a maximum thermal efficiency of 54.26% and a moisture diffusion coefficient of 10.995 × 10-9 m2/s at a hot-air temperature of 55 °C. This confirmed the high efficiency of the combined drying method. A tempering time ratio of 1:4 optimized energy utilization and maintained paddy quality. Additionally, the Verma model accurately predicted moisture content in this new drying system. The results provide valuable insights for applying combined microwave-hot air drying in the paddy drying industry.

An improved method to process the data of optical Fiber signals for identifying the instantaneous flow structure in a gas-solid fluidized bed

The instantaneous signals recorded with the optical fiber probe (OFP) directly reflect the hydrodynamic behaviors in fluidized beds. A new data-processing method is put forward to calculate the threshold voltage that is used to discern the bubble phase and emulsion phase. It is found that the threshold voltage is not only related to the flow pattern but also to the color of the used particles. Then the data-processing programs including the Fast Fourier filter have been developed for determining the flow characteristics such as the bubble/particle velocity, bubble/agglomerations chord length, etc. By comparing them with other different methods, the suitability of the proposed method for quantifying the hydrodynamic behaviors in bubble/turbulent fluidized beds is verified. Finally, this method is employed to analyze the characteristics of bubbles, agglomerations and particles in a gas-solid fluidized bed. It is found that the hydrodynamic behaviors of bubbling beds and turbulent beds have significant differences.

Processing of low-grade Indian coking coal using air fluidized dense medium bed separator and flotation technique

ABSTRACT A dry coal beneficiation process was developed on a batch scale using a gas-solid fluidized bed separator to upgrade the low-grade coking coal from the Jharia Coalfield. Coal collected from Ena open cast mines of Kusunda area, Dhanbad was crushed to 50 mm and 25 mm sizes for dry processing using the dense medium fluidized bed separator followed by froth flotation for particles below 500 microns. Coal with a + 6 mm size fraction was processed via the dry route, while coal with a −6 mm size fraction and pre-concentrate from the dry route was further crushed to 0.5 mm for the froth flotation process using various reagents. The effect of various process parameters of the dry separator such as bed height, dense medium size, air flow rate were studied using CFD software in a simple 2D plane. The study revealed that the dry process for the −50 + 6 mm fraction achieves higher organic efficiency (90%) compared to −25 + 6 mm (81%) due to better washing characteristics. Dry deshaling of high-ash coking coal (−50 + 6 mm) can reduce the ash content from 35.3% to 29.6% with a yield of 75.4%. The flotation process using NALCO synthetic reagents is highly effective, reducing the feed ash content from 27.3% to 17.5% with a notable yield of 85.0%.

Oxidation of magnesium particles in a fluidized bed reactor

Magnesium is a promising fuel for the metal-enabled cycle of renewable energy and for space power systems. However, the existing methods for combustion of magnesium powders have difficulties with maintaining flame stability. Further, the kinetics and mechanisms of high-temperature oxidation of magnesium powders, needed for combustion modeling, are still not well understood. In the present work, a fluidized bed reactor was used to study the oxidation of spherical magnesium particles in an oxygen/helium environment at temperatures of 530, 550, and 570 °C. The extent of conversion was determined based on the measured oxygen concentration in the exhaust gas. The obtained curves of the extent of conversion and of the conversion rate were analyzed using the Avrami-Erofeev equation and the Mampel-Delmon model. The activation energy obtained with the Avrami-Erofeev equation was 191 or 198 kJ∙mol−1, depending on the dimension (3 or 2, respectively). The Mampel-Delmon approach has shown that the activation energies of nucleation and growth are equal to 189 and 120 kJ∙mol−1, respectively, i.e., the former is virtually the same as the apparent activation energy obtained with the Avrami-Erofeev model at a dimension of 3. With increasing temperature, the rate of nucleation rises faster than the rate of growth. The results obtained with the Mampel-Delmon approach help understand the oxidation mechanism, while the Avrami-Erofeev equation and the obtained apparent activation energy can be used in combustion modeling for simplicity.

A Multi-Objective Optimization Framework That Incorporates Interpretable CatBoost and Modified Slime Mould Algorithm to Resolve Boiler Combustion Optimization Problem

The combustion optimization problem of the circulation fluidized bed boiler is regarded as a difficult multi-objective optimization problem that requires simultaneously improving the boiler thermal efficiency and reducing the NOx emissions concentration. In order to solve the above-mentioned problem, a new multi-objective optimization framework that incorporates an interpretable CatBoost model and modified slime mould algorithm is proposed. Firstly, the interpretable CatBoost model combined with TreeSHAP is applied to model the boiler thermal efficiency and NOx emissions concentration. Simultaneously, data correlation analysis is conducted based on the established models. Finally, a kind of modified slime mould algorithm is proposed and used to optimize the adjustable operation parameters of one 330 MW circulation fluidized bed boiler. The experimental results show that the proposed framework can effectively improve the boiler thermal efficiency and reduce the NOx emissions concentration, where the average optimization ratio for thermal efficiency reaches +0.68%, the average optimization ratio for NOx emission concentration reaches −37.55%, and the average optimization time is 6.40 s. In addition, the superiority of the proposed method is demonstrated by ten benchmark testing functions and two constrained optimization problems. Therefore, the proposed framework is an effective artificial intelligence approach for the modeling and optimization of complex systems.

Feasibility of successive hydrogen and methane production: Effects of temperature and organic loads on energy potential and microbial dynamics

This study aims to assess the co-digestion of Cassava Wastewater (CW) and glycerol in a two-stage process using fluidized bed reactors (AFBR), verifying the effect of organic loading rate (OLR) and temperature (mesophilic [SMR] and thermophilic [STR]) in sequential reactors on CH4 production. The OLR ranged from 1.2 to 15 g COD.L−1.d−1 and the hydraulic retention time (HRT) was set at 20 h. The mesophilic sequential reactor (MSR) (average temperature of 30 °C) showed greater tolerance to high OLR and its best MPR was 101.12 mL of CH4.d−1.L−1 h−1, obtained at a OLR of 15 g COD.L−1.d−1). The maximum yield was 341.10 mL of CH4.g−1CODcons, found at the OLR of 1.2 g COD.L−1.d−1. The sequential thermophilic reactor (STR) showed the maximum yield and MPR of 333.03 mL of CH4.g−1CODcons (1.2 g COD.L−1.d−1) and 58.84 mL of CH4.d− 1.L−1 h−1 (12 g COD.L−1.d−1), respectively. Through the massive sequencing analysis of the 16S rRNA gene, it was possible to observe a greater diversity of microorganisms in the TSR than in the MSR. A predominance of acetoclastic microorganisms was observed, with the genera Methanobacterium, Methanosarcina and Methanobrevibacter being the most abundant in both reactors. The two-stage system composed of mesophilic acidogenic reactor + MSR was more suitable for the co-digestion of CW and glycerol than the acidogenic reactor + TSR. These results support the notion of standard operating conditions at the industrial plant, where the cassava processing process is carried out at room temperature (25–30 °C).

Performance Evaluation of a 40-kWth Prototype Counterflow Particle-sCO2 Fluidized Bed Heat Exchanger

Particle-sCO2 heat exchangers (HXs) can couple particle-based thermal energy storage for concentrating solar power (CSP) plants with recompression closed Brayton power cycles (RCBC) to enable continuous dispatchable renewable electricity. RCBC firing temperatures >700°C require HXs with expensive Ni-based alloys, requiring HX designs to reduce mass with high overall heat transfer coefficients UHX to meet CSP primary HX cost. To enhance UHX, mild bubbling fluidization with downward particle flows and upward fluidizing gas flows can achieve particle-wall heat transfer coefficients hT,w >800 W m-2 K-1 with CARBOBEAD HSP 40/70. To assess how high hT,w with mild particle fluidization impacts UHX, a 40-kWth particle-sCO2 HX with 12-parallel narrow-channel fluidized beds was assembled and tested to particle inlet temperatures up to 530 °C. Tests show reliable steady-state HX operation by maintaining fluidized particles in a freeboard zone above the parallel channels, but axial dispersion mixes partially cooled particles up from the fluidized channels with particles fed into the freeboard zone from the feed hopper. This mixing lowers the effective bed temperatures and the driving force for heat transfer to counterflowing sCO2 in microchannelled walls. Measured UHX based on particle inlet temperature never exceeded 205 W m-2 K-1. The trade-off between increased hT,w, and increased vertical dispersion with gas flows resulted in only small improvements in UHX after the onset of fluidization. Dispersion was incorporated into HX design and performance models that used hT,w correlations fitted to single-channel heat transfer tests. Model results show that reducing dispersion leads to higher particle wall heat transfer.