Fluidized Bed Research Articles

Representation of aggregates from their two-dimensional images for primary particles of different sizes

This study focused on representing the three-dimensional (3D) structure of individual aggregates based on their two-dimensional (2D) images. This starts with the determination of 2D box-counting fractal dimension (Df,BC,2D), uses a previously derived empirical correlation to obtain 3D power law fractal dimension (Df,PL), and then builds the aggregate on the basis of Df,PL by an existing algorithm. Validation of this procedure can be done in forward or backward manner. Forward validation requires the existence of tomographic measurements of Df,PL. It has been conducted on aggregates of large primary particles produced to this purpose in a spray fluidized bed and analyzed by X-ray micro-computed tomography (μ-CT). For the same agglomerates backward validation has also been exercised, starting the representation from 2D projections of the 3D objects and repeating the same procedure on the represented aggregates to see, how accurately the fractal dimensions of the original objects are reproduced. When the primary particles are too small in size to be resolved by X-ray μ-CT, only 2D imaging data by electron microscopy are usually available. Such images have been taken from literature for aggregates composed of submicron particles or nanoparticles and used for aggregate representation in 3D. Subsequently, backward validation of the procedure has been conducted. Both forward validation and backward validation results indicate a high level of consistency between the fractal characteristics and morphological structures of the represented aggregates and those of the original ones. Additionally, this study shows that the method is effective for aggregates of bidisperse and polydisperse particles.

Correlation for Maximum Heat Transfer Between Fluidized Bed and Its Wall and Application to Solar Power Plants

Abstract Heat transfer from and to fluidized beds is involved in many applications including chemical processes, power generation, solar collectors, etc. It is generally desired to operate in the range in which the heat transfer coefficient is maximum. Several good correlations have been developed for maximum heat transfer to objects immersed in fluidized beds. However, there is no correlation for maximum heat transfer between the fluidized bed and its enclosing wall. The present research was done to develop such a correlation. A correlation for maximum heat transfer to bed wall has been developed which is in satisfactory agreement with test data from published papers. The data include a wide variety of particles with diameters 70–900 µm, bed diameters 25–101 mm, particle density from 1800 to 3200 kg/m3, particle thermal conductivity 0.5–237 W/m/K, and bed temperature from 18 to 316 °C. A correlation for the optimum velocity was also developed based on the same data. The new heat transfer correlation was compared to published test data for fluidized beds made to flow into solar collector tubes by the application of pressure difference. A modification of it was developed which agrees well with available data.

Cogeneration processes based on giant reed gasification combined with ORC and district heating for heat recovery: Comparative energy and exergy analysis

This research work develops a comprehensive exergy and energy assessment of a cogeneration process using Giant Reed as feedstock, which consists of a biomass dryer, a fluidized bed gasifier, an internal combustion engine operating in a cogeneration mode (CHP), and two different users for the cogenerated heat. One process layout uses cogenerated heat in a district heating network (CHP + DH layout). In the second process layout, the cogenerated heat produces additional electricity through an Organic Rankine Cycle (CHP + ORC layout). In addition to the performance of reed gasification (cold gas efficiency about 0.6), the results showed that the highest rational efficiency was reached in the cogeneration unit, while the highest relative irreversibilities were found in the gasifier and the dryer. The overall energy efficiencies are 0.46 and 0.22 for the CHP + DH and CHP + ORC layouts, respectively, while the overall exergy efficiencies are 0.21 and 0.20. The difference in the sustainability index is just 2 %. The results and methods of this research work can be used to properly design Giant Reed (or similar biomass) gasification plants and bioenergy systems for combined heat and power production, and developing case-studies considering the sustainable use of this feedstock according to a thermodynamic approach based on the second principle.

Streamlined Clarification and Capture Process for Monoclonal Antibodies Using Fluidized Bed Centrifugation and Multi-Column Chromatography With Membrane Adsorbers.

Harmonizing unit operations in the downstream process of monoclonal antibodies (mAbs) has a high potential to overcome throughput limitations and reduce manufacturing costs. This study proposes a streamlined clarification and capture (S-CC) process concept for the continuous processing of cell broth harvested from a connected bioreactor. The process was realized with a fluidized bed centrifuge connected to depth and sterile filters, a surge tank, and a multi-column chromatography (MCC) unit. The MCC unit was operated in the rapid cycling simulated moving bed (RC-BioSMB) mode with five convective diffusive membrane adsorbers (MAs). A control strategy and the surge tank were used to adjust the loading flow rate of the MCC unit. The mAb was recovered with a total process yield of 90%, with high removal of the process-related impurities HCP (2.1 LRV) and DNA (2.9 LRV). Moreover, the S-CC process productivity of 4.2 g h- 1 was up to 5.3 times higher than for comparable, hypothetical batch MA processes. In addition, the buffer consumption of the capture step could be reduced from 2.0 L g- 1 in batch mode to 1.2 L g- 1 in the RC-BioSMB mode. These results demonstrate the high potential of streamlined interconnected unit operations to improve the overall mAb downstream process performance.

Influence of oxygen carrier on NOx and N2O emissions in biomass combustion within fluidized beds

The Oxygen Carrier Aided Combustion (OCAC) technology has the potential to enhance the combustion efficiency and stability of biomass, while simultaneously facilitating the conversion of NO to N2. However, current research lacks sufficient investigation into the impact of oxygen carriers on the conventional fuel nitrogen (fuel-N) conversion pathway, particularly in relation to N2O. This study comprehensively examines the key operating parameters, including ilmenite ore (OC) ratio, O2 concentration, fluidization velocity, and bed temperature, on NO and N2O emissions during the OCAC of rice husk in a bubbling fluidized bed reactor. The findings suggest that when OC is used as bed material, the conversion of fuel-N to NO decreases by 8.84 % under a 3 % O2 concentration at 750 °C, compared to the sand case. This beneficial effect is further enhanced as the temperature increases. Conversely, the conversion of fuel-N to NO increases by 12.15 % and 7.70 % under 6 % and 9 % O2 concentrations, respectively, compared to the sand case. This suggests a distinct influence mechanism between OCAC and traditional combustion conditions, potentially due to the chemical phases of OC during the redox process. The OCAC operations can lead to an increase in the emission of HCN and N2O under all tested conditions. The potential conversion pathway of fuel-N under OCAC conditions is summarized.

Immobilization of Heavy Metals in Biochar Derived from Biosolids: Effect of Temperature and Carrier Gas

Slow pyrolysis was carried out in biosolids under three different temperatures (400, 500 and 600 °C) and two different carrier gases (CO2 and N2) on a fluidized bed reactor. The total concentration, chemical fractionation, and plant availability of the heavy metals in biochar were assessed by standard methods. The total concentration of Fe, Zn, Cu, Mn, Cr, Ni and Pb increased with the conversion of biosolids to biochar and with increasing pyrolysis temperature. The community’s Bureau of Reference (BCR) sequential extraction identified the migration of metals from toxic and bioavailable to potentially stable available or non-available forms at higher pyrolysis temperatures. Diethylenetriamine penta-acetic acid (DTPA)-extractable metals (Cu, Zn, Cd, Cu, Fe and Pb) were significantly lower in biochar compared to biosolids. By replacing N2 with CO2, the total metal concentration of heavy metals was significantly different for Mn, Ni, Cd, Pb and As. There were larger amounts of metals in the residual and oxidizable fractions compared to when N2 was used as a carrier gas. Consequently, the biochar produced at higher temperatures (500 and 600 °C) in the N2 environment exhibited lower potential ecological risks than in CO2 environments (69.94 and 52.16, respectively, compared to values from 75.95 to 151.38 for biochars prepared in N2). Overall, the results suggest that the higher temperature biochar can support obtaining environmentally safe biochar and can be effective in attenuating the ecological risks of biosolids.

Assessment of scale-up designs for a diameter-transformed fluidized bed reactor with MP-PIC simulation

Scale-up has always been the bottleneck to the development of new industrial processes. This study aims to assess the scale-up effects of a diameter-transformed fluidized bed (DTFB) reactor through three-dimensional, multi-phase particle-in-cell (MP-PIC) simulation with the Energy-Minimization Multi-Scale (EMMS) drag and solid stress model. Four 3.5 Mt/a DTFB reactors are designed by scaling up a 1.2 Mt/a one with different scale-up schemes and simulated after validation. It is found the Glicksman’s rule shows the most similarity in solid concentration distribution to the benchmark case while the FixedOperation rule under-predicts the solid concentration, meaning that only keeping constant Ug and Gs cannot guarantee the same distribution of solid concentration when scaling up the fast fluidized bed. In addition, all four scale-up designs ensure the same gas velocity, yet they exhibit varying solid velocities throughout the scale-up process. A more rational scale-up rule is required for the elaborate reactor scale-up.

The Toxicity Leaching and the Cement Admixtures Properties with Incineration Fly Ash of Different Furnace Types.

Incineration of fly ash is a hazardous solid waste, and there are two types of furnaces used for production. The impact of furnace types on the properties and toxicity of incineration fly ash was studied. The resource utilization of incineration fly ash has been tested. The results showed that circulated fluidized bed (CFB) ash and grate (GF) ash were alkaline materials, dioxin content ranged between 98 and 359 ng-TEQ/kg, and heavy metals exceeded 7700 ppm. The leaching of Zn in CFB ash was 110.474 ppm, and that in the GF ash was 5.985 ppm. The chlorine content in GF ash was 27.07%, 2.7 times that of CFB ash. When the content was 5%, GF ash promoted cement grinding and improved the 3-day compressive strength of cement, which was 35.55% higher than the control sample. CFB ash generates hydrogen gas during the hydration process, causing volume cracking. When 20% GF ash was added, the hydration heat release peak appeared 10.5 h ahead of time. According to the Chinese standard GB 175-2023, the maximum dosages of CFB ash and GF ash in cement were 0.22 and 0.57%. There was no risk of excessive leaching of heavy metals. During cement production with CFB and GF ash, attention should be paid to the issues of chlorine and dioxins.

Comprehensive performance investigation of inexpensive oxygen carrier in chemical looping gasification of coal

Coal chemical looping gasification (CLG) using inexpensive oxygen carrier (OC) is a promising technology to obtain H2-rich syngas, and the OCs of copper/iron ore composite with an autothermal capability and red mud have been screened as the potential candidates in our previous investigation. However, the detailed synergetic effect between copper ore and iron ore, and the effect of reaction conditions on syngas production at different reactor scales are still unclear. In this work, the synergetic effect between copper ore and iron ore in composite OCs with different mixing ratios are detailedly investigated through H2 temperature-programmed reduction (TPR) tests. The results indicate that the copper ore addition can contribute the reduction of iron ore and form a new phase of CuFe2O4 between CuO in the copper ore and Fe2O3 in the iron ore, meanwhile observing the composite OC of Cu20Fe80@C generating a stronger synergetic effect in comparison to adjencent OCs. Moreover, the optimization of reaction conditions are conducted in a batch fluidized bed reactor (BFBR) by regulating the temperature, oxygen to fuel (O/F) ratio, and steam concentration for the Cu20Fe80@C and red mud OCs. It is found that a higher temperature is conducive to improving the coal conversion and syngas yield on the whole, but not the H2-rich syngas production. While a lower O/F ratio favors the preparation of H2-rich syngas, and the optimal steam concentration is determined as 50 vol% for both OCs under comprehensive consideration of gasification time, syngas yield and heating cost. Additionally, the copper/iron ore composite OC with excellent CLG performance and bed stability is further confirmed in a semi-continuous fluidized bed reactor (SFBR), which shows the effects of temperature and O/F ratio on syngas production similar to those in BFBR. In summary, the promising copper/iron ore composite OC exhibits good adjustability and adaptability for CLG process in terms of reaction conditions and reactor scales, respectively.

Entrained-flow gasification characteristics of plastic waste pyrolysis oil

Plastic waste (PW) pyrolysis is a promising method in chemical recycling technology; however, PW pyrolysis oil cannot be used directly because of its high contaminant content. Entrained-flow gasification (EFG) is a suitable method for removing contaminants from pyrolysis oil and enhancing the conversion compared with fixed bed or fluidized bed gasification. We examined the basic characteristics of PW pyrolysis oil through EFG with the variation of O2/fuel ratios from 0.6 to 1.4 and steam/fuel ratio from 0.4 to 0.7 at 600–900°C in a lab-scale reactor. The H2 composition and Cold Gas Efficiency (CGE) showed the highest when the O2/fuel ratio was 0.8. The Carbon Conversion Efficiency (CCE) showed the highest values when the ratio was 1.4. C2-C3 gases tended to decrease at higher temperatures because of the thermal cracking of hydrocarbons. In the experiments with the variation of steam/fuel ratio, CO2 concentration decreased with increasing temperature from 600 to 800°C because of the reverse water-gas-shift reaction. The residence time was calculated to review the reaction conditions and was found to be 4.2–7.3 seconds. The experimental data from a lab-scale EFG can serve as fundamental data for the scale-up of integrated pyrolysis and gasification systems.

Design of a Bubbling Fluidized Bed Reactor for Bio-oil Production from Sawdust

Due to the ever increase in energy demand, it becomes imperative to design appropriate reactor for the conversion of available raw materials to energy source such as bio oil. A fluidized bed reactor is one the most promising reactor for the conversion of biomass to bio-oil via pyrolysis. This work take into consideration the design of fluidized bed reactor and its subsidiaries (cyclone, filter, condenser and feed hopper) to be used for bio-oil production using sawdust as the feedstock. The operating conditions were temperature between 400-6000C, pressure 9.9atm and flow rate 1.86m/s. From the design calculations, it was found that the volume of the reactor, area, height, diameter and minimum fluidized velocity were 15.0796mm3, 5026mm2, 300mm, 80mm and 1.86m/s respectively. The material for construction for the reactor is stainless steel because of its high thermal conductivity and resistance to corrosion.

Study of the Influence of the Mean Particle Diameter Choice and the Fractions Number on the Quality of Fluidized Bed Numerical Simulation

We investigate the choosing of the fractions number for numerical simulation of a polydisperse bubbling fluidized bed using the Sauter mean diameter. The results were verified using experiments from a glass tube with a diameter of 2.2 cm and a height of 50 cm. As a fluidizing agent, air with a velocity of 0.0716 m/s to 0.1213 m/s was used. Polydispersed aluminum oxide particles with a diameter size of 20–140 µm were used as a solid phase. We propose a simple method for choosing the fractions number for the polydispersed granular phase in order to improve the quality of the numerical simulation results. In this study, we consider the Sauter mean diameter D32 for each selected group of particles for the solid phase. By increasing the number of solid phase fractions, it is possible to obtain a mean boundary of the bubbling fluidized bed close to the observed experimental results. In our study, the division of polydispersed powder into four distinct solid-phase fractions enabled us to attain satisfactory agreement with experiments regarding the average value of the bed boundary.

Design and fabrication of a prototype fluidized bed dryer for species

Design and fabrication of a prototype fluidized bed dryer for species

Optimization of bitter orange (Citrus aurantium L.) essential oil microencapsulation through spout fluidized bed drying

Optimization of bitter orange (Citrus aurantium L.) essential oil microencapsulation through spout fluidized bed drying

Mechanistic model advancements for optimal calcium removal in water treatment: Integral operation improvements and reactor design strategies

Drinking water softening has primarily prioritized public health, environmental benefits, social costs and enhanced client comfort. Annually, over 35 billion cubic meters of water is softened worldwide, often utilizing three main techniques: nanofiltration, ion exchange and seeded crystallization by pellet softening. However, recent modifications in pellet softening, including changes in seeding materials and acid conditioning used post-softening, have not fully achieved desired flexibility and optimization. This highlights the need of an integral approach, as drinking water softening is just one step in the drinking water treatment chain, which includes ozonation, softening, biological active carbon filtration (BACF) and sand filtration among others. In addition, pellet softening is often practiced based on operator knowledge, lacking practical key reactor performance indicators (KPIs) for efficient control. For that reason, we propose a newly and improved integral mechanistic model designed to accurately predict (1) calcite removal rates in drinking water through seeded crystallization in pellet softening reactors, (2) the saturation of the filter bed in the subsequent treatment step, (3) values for the KPIs steering the softening efficiency. Our new mechanistic model integrates insights from hydrodynamics, thermodynamics, mass transfer kinetics, nucleation and reactor engineering, focussing on critical variables such as temperature, linear velocity, pellet particle size and saturation index with respect to calcite. Our model was validated with data from the Waternet Weesperkarspel drinking water treatment plant in Amsterdam, The Netherlands, but implies universal applicability for addressing industrial challenges beyond drinking water softening. The implementation of our model proposes five effective KPIs to optimize the softening process, chemical usage, and reactor design. The advantage of this model is that it eliminates the application of numerical methods and fills a significant gap in the field by providing predictions of the carry-over (i.e., the produced CaCO3 fines leaving the fluidized bed) from water softening practices. With our model, the calcium removal rate is predicted with an average standard deviation (SD) of 40 % and the consequential clogging prediction of the BACF bed with an average SD of 130 %. Ultimately, our model provides crucial insights for operational management and decision-making in drinking water treatment plants, steering towards a more circular and environmentally sustainable process.

Combing mobile electrical capacitance tomography with Fourier neural operator for 3D fluidized beds measurement

AbstractDespite the practical importance, 3D measurements of gas–solid distribution in fluidized beds calls for further breakthroughs. Here an approach combing a recently developed mobile electrical capacitance tomography (ECT) sensor with Fourier Neural Operator (FNO) is developed, in which the fluidized bed is divided into a series of cross‐sectional slices along axial direction. At any given instant, the gas–solid distribution in one slice is measured by mobile ECT and the others, meantime, are predicted by FNO pre‐trained using experimental data. We verified this approach via computational fluid dynamics (CFD) simulations and experimental measurement of static object (i.e., cone, cylinder, and sphere) in fluidized bed. Following we applied this approach to direct measure 3D gas–solid distribution in a bubbling fluidized bed, and found that satisfactory image correlation coefficients and solid concentration average absolute deviation could be obtained, which indicates the proposed approach is promising for 3D fluidized bed measurements.

Computational Fluid Dynamics–Discrete Element Method Numerical Investigation of Binary Particle Mixing in Gas–Solid Fluidized Bed with Different Drag Models

The fluidized bed is a critical reactor in the energy and chemical industries, where the mixing and agglomeration behaviors of binary particles significantly influence both the efficiency of reaction processes and the uniformity of final products. However, the selection of appropriate drag force models remains a subject of debate due to the variability in particle properties and operating conditions. In this study, we investigated the fluidization behavior of binary mixtures composed of two different sizes of Geldart-D particles within a fluidized bed, evaluating nine distinct drag force models, including Wen and Yu; Schiller and Naumann; Ergun; Gidaspow, Bezburuah, and Ding; Huilin and Gidaspow; De Felice; Syamlal and O’Brien; and Hill, Koch, and Ladd. We focused on four key parameters: particle mixing degree, migration characteristics, temperature variation, and mean pressure drop. Simulation results revealed that the choice of drag model markedly affected mixing behavior, migration dynamics, and temperature distribution. Notably, the Ergun; Gidaspow, Bezburuah, and Ding; and Hill, Koch, and Ladd models exhibited superior particle mixing uniformity. While the drag model had a relatively minor impact on particle temperature changes, its selection became critical in simulations requiring high-temperature precision. Regarding pressure drop, the Huilin and Gidaspow and Gidaspow, Bezburuah, and Ding models demonstrated smaller and more stable pressure drop fluctuations. These findings offer valuable theoretical insights into gas–solid two-phase flow under binary particle mixing and provide practical guidance for the design and operation of fluidized bed reactors.

Recent development on neem (azadirachta indica) biomass absorbent: Surface modifications and its applications in water remediation

This review paper discusses the latest advances in transfiguring Azadirachta indica (neem) biomass into an adsorbent and how it can be used to clean the environment. As an economical and environmentally favorable adsorbent material, neem biomass has become increasingly popular due to its bioactive properties and abundance. The review breaks down modification techniques into chemical and physical processes. Important physical changes covered include preactivation, carbonization, and using fluidized bed technologies and rotary kilns. It has been shown that these methods greatly improve the surface properties of neem biomass, which makes it better at absorbing things and holding more. The changes that were made also have an effect on the adsorption kinetics and isotherms, which helps us understand the adsorption rates and equilibrium behaviors of the changed adsorbents better. Neem biomass adsorbents are illustrated through their versatility and efficacy in the removal of organic pollutants, dyes, and heavy metals from effluent. This is illustrated through specific applications. Additionally, computational studies and artificial intelligence are looked into to see if they can help us understand how adsorption works at the molecular level, improve the efficiency of modification processes, and guess how adsorption will behave. The review also talks about the research gaps and suggests areas for future research. The review emphasizes the crucial importance of integrating experimental and computational methods to enhance the performance of the modified neem biomass and increase its environmental cleaning potential.

Investigation of biomass gasification and fluidization behaviour for pilot double tapered bubbling fluidized bed reactor.

The present investigation discusses syngas production through gasification from six different bamboo biomass species available in India's northeast region (Mizoram). The thermochemical conversion of biomass to syngas is accomplished in a novel double-tapered reactor. The pre-processing stage of biomasses includes various shredding, drying, and sieving methods. In the processing stage, the biomass (20g) is fed to the reactor regularly. The heating element in the interior of the reactor supplies the heat required (600-1000°C) for the combustion and gasification of biomass samples. The influence of various particle sizes on bed voidage, pressure drop, bed height, suspension density, gas yield, heat transfer, and carbon conversion efficiency is studied. The tapered reactor enhanced the bed hydrodynamics. It is observed that the H2 and CO2 composition increases with the temperature (> 900°C), whereas the CO composition is reduced as a result of the shift reaction. However, the CH4 yield is enhanced at a temperature (< 800°C) but lessened at higher temperatures due to a reduction in moisture content. The carbon conversion efficiency (CCE) and the dry gas yield (YG) values obtained are better for the particle size of 1.18mm than the other particle sizes. The energy from biomass resources is promising regarding sustainability, availability, and efficacy. The current approach discusses the syngas generation from bamboo biomass through gasification under varied temperature ranges (600-1000°C), equivalence ratio (0.2), particle sizes (380µm, 600µm, and 1.18mm), superficial velocity (0-2m/s) in a pilot 5kg/h DTBFBR of height 1.2m and maximum inner diameter of 16.5cm.

Adsorption-absorption technique for effective CO2 capture

ABSTRACT This paper presents a study on the removal of CO2 gas from gas mixture (CO2/N2) of 14% CO2 using adsorption onto zeolite 13X in a fluidized bed at 298 K and 1 atm pressure. The effects of static bed height (5–25 cm) and rate of flow of the gas mixture (6–14 L/min) on the breakthrough time were studied. The desorption of CO2 was performed by absorbing the adsorbed CO2 molecules using NaOH solution (0.1 M). The absorption process which was accompanied with chemical reaction achieved two objectives. The first was converting CO2 gas into a valuable substance (Na2CO3) which could be used in many industries. The second was the storage of CO2 gas in what was called a chemical carrier which could emit the gas when it was needed. The effect of static bed height (5–25 cm) on the absorption process in the fluidized bed was also studied. For the adsorption process, the results showed that the breakthrough time increased with decreasing the flow rate but with increasing the static bed height. In the desorption process, the total amount of absorbed CO2 molecules was 396 mg, achieving a recovery of 90.8% at 5 cm static bed height.