Fluidized Bed Reactor Research Articles

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.

A Systematic Approach to Determining the Kinetics of the Combustion of Biomass Char in a Fluidised Bed Reactor

A Systematic Approach to Determining the Kinetics of the Combustion of Biomass Char in a Fluidised Bed Reactor

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.

Dual approach in textile wastewater treatment: optimisation and comparison of fluidised-bed and conventional Fenton processes

ABSTRACT This study optimises secondary textile dyeing wastewater removal using fluidised-bed Fenton (FBR-Fenton) and standard Fenton processes for chemical oxygen demand (COD) and colour removal efficiency. The Box–Behnken response surface approach optimised pH, iron ion concentration, and hydrogen peroxide concentration. At pH 3.3, [Fe2+] = 2.6 mm, [H2O2] = 6.4 mm in the fluidised bed reactor with 67 g/L quartz sand, with a 50% bed expansion after 40 min, the FBR-Fenton process removed 75.8% COD and 98.0% colour. The standard Fenton method was tuned to pH 3.2, [Fe2+] = 3.1 mm, [H2O2] = 6.6 mm, and COD and colour removal effectiveness of 69.7% and 97.5%, respectively. FBR-Fenton enhanced COD and total iron removal efficiency, reduced chemicals, and reduced sludge by 28.0% compared to conventional Fenton. This study also showed quartz sand reusability in FBR-Fenton treatment cycles. Experimental results matched response surface model predictions, proving regression equation correctness.

Heat transfer efficiency in gas–solid fluidized beds with flat and corrugated walls

Abstract Gas–solid fluidized bed reactors exhibit improved heat and mass transfer performance as compared to packed beds. Corrugated walls installed in narrow gas–solid bubbling fluidized bed (CWBFB) enclosures have been observed to decrease minimum bubbling velocity, reduce bubble size, improve gas distribution, provide stable operation, and minimize particle carryover or loss. Thorough analyses of the wall-to-bed heat transfer coefficient in flat- (FWBFB) and corrugated- (CWBFB) wall bubbling fluidized beds have been performed for a variety of operating conditions and geometric parameters. Fast-response self-adhesive heat flux probes and thermocouples were used to simultaneously measure the wall-to-bed heat flux, surface and bed temperatures, and were used to determine the heat transfer coefficient (HTC) at various axial and lateral locations. For a given set of parameters, a significant increase in HTC was observed at lower gas flow rates in CWBFB as compared to FWBFB. It was shown that CWBFB inventory required lower U mb (gas flow rate) as compared to FWBFB. Full 3-D transient Euler–Euler CFD simulations using the kinetic theory of granular flow were also performed, which confirmed the experimental results.

Fluidized-bed OCM reaction: A promising Mn2O3-Na2WO4/TiO2 catalyst and a numerical study

The fluidized-bed reactor with excellent heat and mass transfer features has great appeal for application in the oxidative coupling of methane (FB-OCM), whereas qualified fluid catalysts represent a grand challenge. Herein, we report a high-performance Mn2O3-Na2WO4/TiO2 fluid catalyst (5.4 wt% Mn2O3 and 2 wt% Na2WO4), which was obtained by the incipient-wetness impregnation method and examined in the OCM reaction in an electric-heating quartz fluidized-bed reactor (i.d., 2 cm). The standard normalization method on the basis of carbon atom was used for calculating the CH4 conversion and C2-C3 selectivity. This catalyst achieves 35.5 % CH4 conversion, 66 % C2-C3 selectivity and particularly 15.1 % single-pass yield of C2H4 for a feed of CH4/O2/H2O=3/1/1 with a catalyst dosage of 20 mL at 700 °C and a total GHSV of 7200 h−1. Such catalyst is stable for at least 50 h without signs of deactivation and agglomeration/defluidization. The catalyst particle size is crucial for the FB-OCM reaction with respect to the reaction light-off and catalyst fluidization. The catalyst with preferable particle size of 450–600 μm can not only trigger the OCM reaction at a relatively low temperature of 630 °C but also warrant active bubbling fluidization. Furthermore, thanks to the low amount of Na2WO4 and interpenetrating structure of TiO2-nanorod, such catalyst achieves good anti-aggregation and robust mechanical strength (with a low attrition index of 1.9 %). The effects of water-adding amount in feedstock and catalyst particle size distribution on the hydrodynamics behaviour were investigated in a laboratory-scale fluidized-bed OCM reactor by using numerical simulation method.

Material Engineering Solutions toward Selective Redox Catalysts for Chemical-Looping-Based Olefin Production Schemes: A Review.

Chemical looping (CL) has emerged as a promising approach in the oxidative dehydrogenation (ODH) of light alkanes, offering an opportunity for significant reductions in emissions and energy consumption in the ethylene and propylene production industry. While high olefin yields are achievable via CL, the material requirements (e.g., electronic and geometric structures) that prevent the total conversion of alkanes to CO x are not clearly understood. This review aims to give a concise understanding of the nucleophilic oxygen species involved in the selective reaction pathways for olefin production as well as of the electrophilic oxygen species that promote an overoxidation to CO x products. It further introduces advanced characterization techniques such as X-ray photoelectron spectroscopy, Raman spectroscopy, electron paramagnetic resonance spectroscopy, and resonant inelastic X-ray scattering, which have been employed successfully in identifying such reactive oxygen species. To mitigate CO x formation and enhance olefin selectivity, material engineering solutions are discussed. Common techniques include doping of the bulk or surface and the deposition of functional coatings. In the context of energy consumption and CO2 intensity, techno-economic assessments of CL-ODH systems have predicted energy savings of up to 80% compared to established olefin production processes such as steam cracking or dehydrogenation. Finally, although their practical application has been limited to date, the potential advantages of the use of fluidized bed reactors in CL-ODH are presented.

Addressing small-scale temperature swing adsorption challenges using intensified fluidised bed technology for carbon capture process development

Polyethylenimine (PEI)-based adsorbents exhibit high CO2 capacities, making them potential candidates for mitigating unavoidable industrial CO2 emissions. However, desorption of CO2 from PEI, and from adsorbents in general, has received far less attention in the literature than adsorption. Whilst Temperature Swing Adsorption (TSA) is simple to conceptualise, it is difficult to implement in small-scale experiments in practice. Here we study the desorption characteristics of a commercial branched PEI adsorbent in a small-scale swirling fluidised bed reactor (TORBED) to improve the small-scale heat transfer rates. Our experimental results show that higher desorption temperatures, higher gas flow rates, and higher CO2 concentrations during adsorption can improve the desorption efficiency (defined as the amount of CO2 removed as a fraction of the initial amount adsorbed). In terms of kinetics, we found that the fractional order kinetic model provided the best fit to the PEI adsorbent, implying that this adsorbent involves multiple simultaneous molecular interactions, physisorption processes, and chemisorption processes, that cannot be described by simpler pseudo 1st or 2nd order models. Desorption rates in the TORBED in this study were 1 order of magnitude faster than fluidised beds, and 2–3 orders of magnitude faster than packed beds.

How torrefaction impacts minimal fluidization velocity from different biomasses and their mixtures

Torrefaction has emerged as a promising technology for optimizing the efficiency of thermochemical processes. However, many challenges still need to be addressed regarding its integration with other processes, such as gasification. This work investigates the potential of torrefaction to transform the properties of biomass mixtures, improving operations in fluidized bed reactors. Experimentally, hazelnut shells and olive pit mixtures were torrefied at 280 °C for 45 min to analyze how torrefaction affected the minimum fluidization velocity as a bulk density function. The results were compared to other biomasses from the literature. Our findings show that torrefaction can stabilize minimum fluidization velocity at 0,45 m/s for mixtures of biomasses with bulk densities below 700 kg/m3 and particle size range (T) of 1,7 < T < 2,36 × 10−3 m. These findings collectively emphasize the potential of torrefaction as an effective technology for utilizing agro-industrial residues in energy generation processes not only for the improvement of conversion efficiency but also for operation stability.

Three-dimensional computational fluid-dynamic simulation of polypropylene steam gasification

Among the recycling techniques, gasification allows to obtain a hydrogen-rich gas from polypropylene (PP), a widely used thermoplastic material. In this work, devolatilization and steam gasification tests of PP were conducted in fluidized bed reactors. The results show a gas yield of 1.3 and 3.0 Nm3/kgPP, and a tar content of 117.3 and 20.9 g/Nm3 from devolatilization and gasification, respectively. Experimental results provide an overall overview of this process, able to produce a syngas with an H2-content of 50 vol%dry.Experimental data coupled with kinetic analysis were used to develop a computational fluid dynamic model (CFD) capable of describing both thermal degradation and subsequent gasification reactions. Although some discrepancies on water conversion and H2/CO ratio probably related to the influence of steam in radical chain-scission the model allows to describe gas production and hydrocarbons evolution providing important support for modeling and sizing of fluidized bed reactors on an industrial scale.

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.

Changes in microbial communities during high-rate microbial selenate reduction in an up-flow anaerobic fluidized bed reactor

Biological fluidized bed reactor (FBR) is a promising treatment option for removing selenium oxyanions from wastewater by converting them into elemental selenium. The process can achieve high rates and be efficiently operated at low hydraulic retention times (HRT). However, the effects of HRT on the changes in microbial community in the FBR process have not been previously explored. In this study, dynamic changes of microbial communities both on biofilm carrier and in suspension of a selenate-reducing FBR were explored at various HRTs (0.3–120 h). Based on partial 16S rRNA gene sequencing of the microbial communities, alpha diversity of microbial communities in suspension rather than in the biofilm were impacted by low HRTs (0.3 h–3 h). Members from genera Geobacter, Geoalkalibacter, and Geovibrio were the main selenate-reducing bacteria on carrier throughout the FBR process. Genus Geobacter was dominant in FBR carrier at HRT of 24 h–120 h, whereas Geoalkalibacter and Geovibrio dominated at low HRT of 0.3 h–6 h. Suspended microbial communities detected in the FBR effluent were more sensitive to HRT changes than that in biofilm. “Shock loading” at HRT of 0.3 h had a great impact on microbial community compositions both in the biofilm and effluent. Reactor operation in batch mode and long HRT of 24 h helped recover the community from “shock loading” and improved selenite reduction and ethanol oxidation. Redundancy analysis revealed that HRT, influent pH and selenate loading were key operational parameters impacting both the FBR performance and the composition of microbial communities associated with both the FBR carrier and effluent. Overall, the microbial communities in FBR biofilm flexibly responded to the changes of HRT and showed resilience to the temporary shock loading, enabling efficient selenate removal.

New Modeling Approaches for Ethylene Oxychlorination in Fluidized Bed Reactors: Industrial and Low Flow Rate Conditions

A simple model (Continuous Stirred-Tank Reactor) has been developed to predict the behavior of industrial ethylene oxychlorination fluidized beds operating in a turbulent regime. The approach showed good agreement both with results from industrial reactors and with those corresponding to the (Simple two phases-Plug bubble-Mixed flow emulsion approach) validated in the literature. For low flow rates, the use of the (Simple two phases - Plug bubble - Plug emulsion model) adapted to these conditions enabled us to highlight the location and extent of undesirable thermal hot spots for the process, and to propose actions to control them by acting on the temperature and/or on the feed gas flows. By comparing this model with the plug approach, the significant slowdown in ethylene conversion caused by resistance to mass transfer when feed flow rates are low is highlighted. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Study of the co-pyrolysis behavior and bio-oil characterization of walnut shell and polyethylene by thermogravimetric analyzer and bubbling fluidized bed

In the present work, co-pyrolysis experiments of walnut shell (WS), polyethylene (PE) and their blends were performed in the thermogravimetric analyzer and lab-scale bubbling fluidized bed reactor, to clarify co-pyrolysis behaviors, synergy interactions and pyrolysis oil properties. Besides, the HZSM-5 zeolite was used as the catalyst and its catalytic characteristics were studied. Results indicated that as PE mass ratio rose from 0 to 100 %, the initial temperature monotonically increased from 265.4 to 417.3 °C, while its terminal temperature progressively decreased from 668.3 to 527.5 °C, suggesting that the addition of PE was able to accelerate the pyrolysis of samples. The co-pyrolysis of blends was distinguished into three stages, with a negative interaction observed in the first stage and positive interactions found in second and third stages. Besides, in the bubbling fluidized bed experiments, the liquid phase product yield first elevated and then reduced with rising temperature, and a high temperature promoted the degradation of oxygen-containing compounds and enhanced aromatics generation. The synergistic interaction in the co-pyrolysis of WS and PE declined the liquid phase product yield while elevating the gas phase product yield. On the other hand, blending with PE facilitated the generation of alkanes and olefins, while inhibiting the contents of oxygen-containing components and aromatics, and simultaneously, the heavy oil fraction was increased. Finally, the carbon deposited on the surface of catalysts was amorphous carbons, and could be removed by oxidation process, whereas its catalytic properties progressively declined with rising cycle number, leading to a downtrend of aromatics and olefins and an opposite trend for oxygen-containing components.

Origin of biogeographically distinct ecotypes during laboratory evolution

Resource partitioning is central to the incredible productivity of microbial communities, including gigatons in annual methane emissions through syntrophic interactions. Previous work revealed how a sulfate reducer (Desulfovibrio vulgaris, Dv) and a methanogen (Methanococcus maripaludis, Mm) underwent evolutionary diversification in a planktonic context, improving stability, cooperativity, and productivity within 300–1000 generations. Here, we show that mutations in just 15 Dv and 7 Mm genes within a minimal assemblage of this evolved community gave rise to co-existing ecotypes that were spatially enriched within a few days of culturing in a fluidized bed reactor. The spatially segregated communities partitioned resources in the simulated subsurface environment, with greater lactate utilization by attached Dv but partial utilization of resulting H2 by low affinity hydrogenases of Mm in the same phase. The unutilized H2 was scavenged by high affinity hydrogenases of planktonic Mm, producing copious amounts of methane. Our findings show how a few mutations can drive resource partitioning amongst niche-differentiated ecotypes, whose interplay synergistically improves productivity of the entire mutualistic community.

CREC Optical-Fibre Sensors for Hydrodynamic Studies in Gas−Solid Fluidized Beds

Optical probes can be employed in dense and dilute fluidized beds. Their application is useful to determine particle volume fraction, bubble velocity, bubble size, and solid segregation in dense-phase fluidized-bed reactors, as well as particle-cluster velocity, size, and shape, in downer/riser units. The CREC-UWO team has developed a unique and miniaturized CREC Optiprobes System (CREC-GS-OPS) equipped with a GRIN (graded refraction index) lens. The GRIN lens creates a small volume of high light irradiation by focusing a laser a few millimetres away from the front of the probe tip. This design minimizes sensor intrusiveness and, as a result, provides trustworthy measurements of hydrodynamic parameters. Through the application of the CREC-GS-OPS, advances have been achieved, leading to (a) the development of a “Y-back” unit with graphite ferrules that protects the optiprobes from fibre-optic stresses and prevents the loss of sensor calibration and (b) the establishment of statistically-based data analysis. It is envisioned that through the introduction of a few design changes, the CREC Optiprobes will be made suitable for high-temperature applications. This will allow the measurement of catalyst flow recirculation (among other measurements), in industrial-scale fluidized-bed catalytic cracking units involving fluidized riser crackers and catalyst regenerators.

Integrated attrition model of mechanical-thermal-reaction for CaCO3/CaO thermochemical energy storage

Fluidized bed reactors have become a pivotal trend in the future development of thermochemical energy storage. However, high temperatures and chemical reactions exacerbate particle attrition in fluidized bed reactors, affecting particle cyclic stability and reducing energy storage efficiency. This study conducted experiments under three different temperature conditions to compare and investigate the attrition mechanisms of CaCO3/CaO particles. The contributions of mechanical forces from collisions, thermal stress due to uneven cooling and heating, and chemical stress from cyclic reactions to particle attrition are analyzed. The edge effects caused by sphericity dominate the attrition behavior during the initial period of fluidization. High-temperature thermal stress significantly weakens the attrition resistance of the particles, while repeated chemical cycling degrades the internal skeletal structure of the particles, lowering the fracture threshold. Based on fitting experimental data, a comprehensive numerical model for predicting particle attrition has been developed and improved by incorporating factors such as edge effects from sphericity, thermally induced stress, and chemically driven fragmentation. Through validation, the model effectively predicts particle attrition behavior in thermochemical storage process, providing a simulation tool for in-depth research on particle stability in thermochemical energy storage field.

Experimental and CFD studies on collection efficiency of separator with arc settlers of fluidized bed catalytic reactor

Separation of catalyst dust from gas in a fluidized bed reactor is an important process. A new solid-gas separator with arc settlers was developed, in which a stable wave flow pattern of the dusty gas flow is formed. The model was based on the RANS approach using the Reynolds Stress Model for the turbulence closure and the Discrete Phase Model. Validating the simulation results with the test data showed good convergence, no more than 6% in the pressure drop and less than 15.5% in collection efficiency at different inlet gas velocities. The CFD study revealed that with a dusty gas inlet velocity of no more than 1 m/s and a catalyst particle larger than 20 μm, efficiency close to 100% is achieved with a pressure drop of less than 60 Pa. Maximum efficiency is achieved when the number of rows of the arc settlers with 40 mm diameter is 8.

Noncalcined Manganese Ores as Oxygen Carriers for Chemical Looping Combustion with Oxygen Uncoupling in a Circulating Fluidized Bed Reactor System

Noncalcined Manganese Ores as Oxygen Carriers for Chemical Looping Combustion with Oxygen Uncoupling in a Circulating Fluidized Bed Reactor System

Computational simulation of SE-SR of methane in a bench-scale circulating fluidised bed reactor: Insights into the effects of bed geometry design and catalyst-sorbent ratios

Operating sorbent-enhanced steam reforming (SE-SR) of methane in fluidised bed reactors presents a promising pathway for industrial low-carbon hydrogen production. However, further understanding of its complex multi-phase behaviours under certain operating conditions is still needed to guide reactor design and scale-up. This study developed a computational particle fluid dynamic (CPFD) reactor model to study cyclic SE-SR performance. The model was used to simulate scenarios representing potential reductions in catalyst activity and sorbent inventory levels over time by varying catalyst-sorbent ratios. Additionally, the effects of two different bed geometry designs were examined.Results indicate that varying solids ratios influenced reaction progress, with optimised methane conversion and CO2 capture observed at moderate ratios. Higher sorbent loadings enhanced thermal neutrality but risked increased calciner energy penalties. Bed geometry also influenced localised hydrodynamics. Detailed solids and gas concentration contours provided insight into segregation and spatial product distribution in the two designs.