Bed Loading Research Articles

Fluidized bed drying of supported Catalysts: Effect of process parameters

Fluidized bed drying is an important unit operation in the manufacturing of supported catalysts. This unit operation remains a challenging step due to simultaneous heat and mass transfer, making it difficult to predict and scale up. This work focuses on applying a mathematical model to predict drying curves and drying rates in a fluidized bed dryer. The model was compared to experiments in a Glatt GPCG-1 fluidized bed dryer. Experiments were conducted by varying air flow rate, bed loading, inlet air temperature, and initial moisture content using water impregnated supports. Results from the model showed good agreement with experimentaldrying curves. The model predicted the drying time for cases that were not initially fluidized. The modelpredicts drying curves for changes in single process parameters when the experiments started in the same drying period. Lastly, the model prediction was extended to multiple changes in process parameters and showed good agreement.

Performance evaluation of H2S and NH3 removal by biological trickling filter reactors with various fillers under heterotrophic conditions

A pilot-scale biological trickling filter (BTF) reactor (13.5 L) packed with different fillers (Pine bark, Cinder, Straw, and MBBR (mobile bed biofilm reactor) filler was employed to evaluate their removal performance of H2S and NH3 after heterotrophic bacterium addition, and some parameters, including different packing heights, empty bed residence time (EBRT), inlet titers, loading ratios, and restart trial, were investigated in this study. According to the experimental results, BTF filled with pine bark exhibited better removal efficiency than other reactors under a variety of conditions. The removal efficiency of H2S and NH3 reached to as high as 81.31 % and 91.72 %, respectively, with the loading range of 3.29–67.70 g/m3·h. Moreover, due to the addition of heterotrophic bacterium, the removal efficiency was enhanced and capable to eliminate majority of H2S and NH3 even though the packing height was reduced to 400 mm. After 15 days of idle, the BTF reactor was able to resume rapidly and execute deodorization with high efficiency. The degradation mechanism was further explored by a thorough examination of microbial species which degraded contaminants, as well as by functional prediction and correlation analyses. In a word, these results laid a foundation for the application of heterotrophic microorganisms in BTF, which could improve the removal efficiency of biological deodorization.

Fixed-bed CO2 adsorption onto activated char from the pyrolysis of a non-recyclable plastic mixture from real urban residues

The potential use of activated char obtained from the pyrolysis of a mixture of non-recyclable plastics for the adsorption of CO2 in fixed-bed columns has been explored. The rejected fraction of plastics collected in a municipal solid treatment plant was pyrolyzed and the resulting char residue was activated to develop a porous carbonaceous material. The dynamic behavior of CO2 adsorption was assessed by the breakthrough curves obtained in continuous column tests. Among all the available models, the curves were successfully fitted to the dose-response model. The effect of adsorption temperature (15–45 ºC), the inlet CO2 concentration (10–40 %, vol.), and the adsorbent length of the bed (loadings, 1–2 g) on the efficiency of the process was evaluated by the surface response methodology applying an adaptative neural fuzzy inference system (ANFIS). A temperature rise exerted a negative effect on the adsorption capacity due to the physisorption properties of the process, the fed CO2 concentration displayed a positive effect and the fixed-bed length did not play a remarkable influence.

Spatial Distribution of Vegetation on Stream Bars and the Riparian Zone Reflects Successional Pattern Due to Fluid Dynamics of River

The river is a dynamic space where erosion, transportation, and sedimentation are constantly occurring due to running water. This study aims to reveal the change in geomorphology caused by the flow characteristics of water in rivers and the response of vegetation to that. This study was carried out by clarifying the spatially appearing successional trends in the vegetation established in the stream bars and the riparian zones, which are located on different topographic conditions based on the vegetation profile, ordination result, and species diversity. The spatial distribution of vegetation on the stream bars tended to appear in the order of annual plant-, perennial plant-, and tree-dominated stands from the upstream toward a downstream direction (a gravel bar and a sand bar in a mountain gravel-bed river and an estuary, respectively) or the reversed one (a sand bar in a lowland river). The spatial distribution of vegetation on the riparian zones tended to appear in the order of annual plant-, perennial plant-, and tree-dominated stands from the waterfront toward the bank direction. Changes in species composition also differed depending on the spatial location, showing a similar trend to the spatial distribution of vegetation. Species diversity became higher in proportion to the longevity of the dominant species of each vegetation type. In conclusion, the longitudinal distribution pattern of vegetation on the stream bars resembles the lateral distribution of riparian vegetation, and the successional trends follow the spatial distribution pattern. These results suggest that the dynamics of bed loading, an allogenic process, may be an important determinant of the spatial distribution and succession of plant communities in dynamic riverine environments.

Metal-organic framework-derived NaMxOy adsorbents for low-temperature SO2 removal

This work reported the fabrication of NaMxOy-type adsorbents from air calcination of (Na, M)-trimesate metal-organic frameworks. NaMnxOy (NMO) crystallized as disc-shaped microsheets, whereas NaCoxOy (NCO) crystallized as smooth microsheets with surface deposition of polyhedral nanoparticles. The oxides have a surface area of 1.90–2.56 m2 g−1. The synthesized adsorbents were studied for low-temperature SO2 removal in breakthrough studies. The maximum adsorption capacity of 46.8 mg g−1 was recorded for NMO at 70 °C. The adsorption capacity increased with the increasing temperature due to the chemisorptive nature of the adsorption process. The capacity increased with the increasing bed loading and decreasing flow rate due to the improved SO2 retention time. The elemental mapping confirmed the uniform distribution of sulfur species over the oxide surface. X-ray diffraction showed the absence of metal sulfate nanoparticles in the SO2-exposed samples. The X-ray photoelectron analysis confirmed the formation of surface sulfate and bisulfate. The formation of oxidized sulfur species was mediated by hydroxyl groups over NMO and lattice oxygen over NCO. Thus, the work demonstrated here is the first such report on the use of NaMxOy-type materials for SO2 mineralization.

Cross-scale quality assessment of a mechanistic cation exchange chromatography model.

Cation exchange chromatography (CEX) is an essential part of most monoclonal antibody (mAb) purification platforms. Process characterization and root cause investigation of chromatographic unit operations are performed using scale down models (SDM). SDM chromatography columns typically have the identical bed height as the respective manufacturing-scale, but a significantly reduced inner diameter. While SDMs enable process development demanding less material and time, their comparability to manufacturing-scale can be affected by variability in feed composition, mobile phase and resin properties, or dispersion effects depending on the chromatography system at hand. Mechanistic models can help to close gaps between scales and reduce experimental efforts compared to experimental SDM applications. In this study, a multicomponent steric mass-action (SMA) adsorption model was applied to the scale-up of a CEX polishing step. Based on chromatograms and elution pool data ranging from laboratory- to manufacturing-scale, the proposed modeling workflow enabled early identification of differences between scales, for example, system dispersion effects or ionic capacity variability. A multistage model qualification approach was introduced to measure the model quality and to understand the model's limitations across scales. The experimental SDM and the in silico model were qualified against large-scale data using the identical state of the art equivalence testing procedure. The mechanistic chromatography model avoided limitations of the SDM by capturing effects of bed height, loading density, feed composition, and mobile phase properties. The results demonstrate the applicability of mechanistic chromatography models as a possible alternative to conventional SDM approaches.

Miniaturisation of the toroidal fluidisation concept using 3D printing

We used the stereolithography printing technique to fabricate a toroidal fluidised bed (TORBED) at the smallest scale ever achieved (50mm diameter with 10mm annular width). In toroidal fluidisation, most of the kinetic energy of the fluidising gas is used to induce swirling of the particle bed meaning higher gas velocities can be used without entrainment. The end-goal of this research is to use this ‘mesoscale-TORBED’ for screening adsorbents for CO2 capture, where the intensified heat/mass transfer rates can potentially minimise the troublesome scalability issues encountered in standard packed beds, a consequence of gradient effects. Here, we have performed a comprehensive parametric study to understand the influence of bed loading, gas volumetric flow rate, gas temperature and gas humidity on the swirling bed formations of activated carbon pellets in order to identify appropriate conditions for sorbent screening. We show that desirable ‘uniform packing’ occurs across a broad range of operating conditions and identify the lower bed loading limit as 1200mg. Other observed bed formations included collapsed, maldistributed and entrained states that caused gas bypassing of the particle bed. At the lowest air flow rate studied (27L/min), the bed was either in the collapsed state or not swirling at all, whilst swirling was readily observed at the intermediate and high air flow rates (35.5L/min and 44L/min respectively). Humidity and air temperature had minimal influence over the flow patterns.

Integration of Biochar Filtration into Aquaponics: Effects on Particle Size Distribution and Turbidity Removal

Small- and large-scale biochar-based filtrations were conducted to investigate the potential of biochar as a low-cost renewable filtration medium in aquaponics. The small-scale experimental design investigated the effects of 2 biochar media sizes (1 – 3 mm [referred to as fine biochar] and 3 – 5 mm [referred to as coarse biochar]), 3 biochar bed heights (2.5, 5.0 and 10.0 cm) and 3 loading rates (5, 10 and 15 m3/m2/d) on particle size distribution as well as turbidity removal efficiency. Both biochar sizes (fine and coarse) were able to clarify fish effluent. However, fine biochar led to better filtration characteristics compared to coarse biochar. Results indicated that biochar filter bed heights and loading rates affected the filtration performances. Using deeper filters combined with lower loading rates led to greater removal of suspended particles and turbidity compared to shallower filters and/or higher loading rates. Results from the large-scale filtration, using a mixture of fine and coarse biochar media (size of 1 – 5 mm), revealed that the ideal loading rate for maximizing the removal of turbidity from fish effluent in high-intensity aquaponic system for production of Nile tilapia and greenhouse plants (with 80 m3 total volume of water, 40 kg/m3 average stocking density and 15 kg/d feeding rate) was 10 m3/m2/d. This study suggests that biochar-based filtration could be incorporated into aquaponics as a polishing step before sending the water to plant growth systems.

Mapping the operating performance of a novel internally circulating fluidized bed reactor applied to chemical looping combustion

Chemical looping combustion is a promising technology for minimizing the energy penalty of CO2 capture. To accelerate the scale-up and commercialization of this technology for pressurized operation, the internally circulating reactor (ICR) was recently proposed. ICR integrates the two reactors, cyclones, loop seals and solids transport lines of the conventional chemical looping configuration into a single unit that simplifies design and operation. This work reports the ICR operating performance over a range of operating parameters applied to chemical looping combustion (CLC). The concept proved relatively simple to operate, allowing the oxygen-carrier circulation rate to be controlled over a wide range by varying the bed loading and the air reactor feed rate. Fully autothermal CLC operation was demonstrated as an illustration of the ease of ICR operation. Gas leakage between the two reactor chambers decreased strongly with decreasing solids loading, resulting in CO2 capture and purity up to 94% for the lowest bed loading. The data showed that significant room for further optimization of the solids transport ports in the reactor exists, which will further increase the CO2 separation performance. These results demonstrate the promise of ICR concept and provide valuable insights for the design of larger-scale units in future work.

Impact of Particulate Size During Deep Loading on DPF Management

Wall-flow particulate filters are a required emission control device to abate diesel emission in order to comply with current regulations. DPFs (diesel particulate filters) are characterized by high filtration efficiency—but in order to avoid deterioration of power and performance, they are required to cause low values of backpressure. The periodical oxidation of collected particle allows for the reestablishment of the ideal flow conditions. Studies highlighted that the regeneration event has an important impact on engine emission, since it is responsible for the emission of a large number of smaller particles. From these considerations, the importance of optimizing the DPF management for what concerns both filtration and regeneration mechanisms arises. The present paper focuses on the loading process of the filter. A filtration model was implemented, based on the ‘unit-collector’ and fluid-dynamic approaches, known as valid modelling techniques. The model was used to predict trapped mass and filter backpressure evolution with time during loading processes, in which soot particle sizes varied, with the aim to analyze how particulate size affects the filter pressure drop rise. A wall-flow filter was investigated, and the behavior of clean material was evaluated by a parametric analysis in which particle diameter varies in the filed 20–1000 nm, that is the typical range of soot sizes in diesel engine exhaust. The results demonstrate that soot size has a great influence on the initial deep bed loading process. Moreover, it defines the value from which the linear pressure drop shape during cake filtration starts, not only when the initial loaded is completed, but also each time the regeneration event is concluded. This outcome provides an important guideline to define the most appropriate strategy for the initial DPF loading in order to establish the regeneration event based on the estimation of trapped mass accounting for the filter backpressure and on the time interval between two successive regeneration.

Aluminum Oxide–Supported Manganese Oxide Catalyst for a 98% Hydrogen Peroxide Thruster

Silica-doped alumina–supported catalyst, containing manganese oxides, doped with cobalt oxide, was prepared in situ by wet impregnation, vacuum drying, and calcination at 700°C. Potassium permanganate and cobalt nitrate were used as precursors and thermally decomposed. The active phase content was determined by simple mass measurement. Subsequently, scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction, and physical adsorption by Brunauer-Emmet-Teller tests have been carried out to determine the morphology, chemical and phase composition, and specific surface area. The catalyst was subjected to the real-environment testing in a packed catalyst bed of a small rocket engine; 98% hydrogen peroxide was applied as propellant. At the design stage of a packed catalyst, it was assumed that a bed loading varied from 24.5 to . The total propellant throughput was 5.43 kg. After the test campaign, the microscopic observation of the structure and physisorption were repeated to describe changes in the structure of the active phase. Test parameters and their change in time were analyzed. The influence of structural and chemical changes between fresh and tested catalysts was taken into consideration. The quality of pure carrier and manganese oxides catalyst, for decomposition of 98% hydrogen peroxide, was investigated. A comparison of performance with alumina-supported platinum catalyst was presented and discussed.

Simulation of elevated temperature solid sorbent CO2 capture for pre-combustion applications using computational fluid dynamics

CO2 adsorption is one of the warm gas cleanup technologies under development for integrated gasification combined cycle (IGCC) applications. Computational Fluid Dynamics (CFD) can be a practical and powerful tool for reactor design for and optimization of the CO2 adsorption process. In this present work, CFD simulation was developed in commercially available ANSYS Fluent software and validated for solid sorbent CO2 capture to investigate pressure swing adsorption (PSA) for CO2 separation from syngas with all the auxiliary operating steps. The adsorption equilibrium and kinetics were incorporated into ANSYS by user defined functions (UDFs) for source terms in Navier–Stokes equations. The CFD model well predicted the CO2 breakthrough curve and temperature change. It was shown that in demo reactor operation, at the end of adsorption step, only half of the sorbent was loaded with CO2, while most of the loaded CO2 was released during the desorption step. Further optimization of sorbent packing and cycle operation can be done with assistance of this CFD model to maximize bed loading, and used to design the commercial size reactors.

Modeling the effect of shrinkage on fluidized bed drying of orthodox broken type tea

Fermented tea particles (dhool) are a polydisperse system subject to shrinkage during fluidized bed drying, which is an important process in the production of orthodox broken type tea. The effect of shrinkage on the physical properties and the minimum fluidization velocity were studied. Five different moisture contents of dhool particles were chosen in the range of 3-106 mass% (dry basis) and the changes in particle diameters and particle densities were measured. For each of the moisture contents, the minimum fluidization velocity was found for three different bed loadings using ambient air at 25?C in a fluidized bed with an area of 351?345 mm2. Since the conventional industrial type fluidized bed dryers operate at 124?C, the new correlations among the Archimedes number, Reynolds number at minimum fluidization and dimensionless moisture content were developed using air properties at 124?C. The results were validated for orthodox broken type tea, drying at 124?C, in a fluidized bed dryer with bed loadings in the range of 44.5 to 50.5 kg/m2. The predicted fluidization velocity was found to be in good agreement with the experimental data and the difference was below 10% for most cases.

Hydrodynamics study on drying of pepper in swirling fluidized bed dryer (SFBD)

Malaysia is one of the pepper producer with exports quantity reaching more than 90000 tonnes between 2010 until 2016. Drying of pepper is mandatory before their export and at present, pepper was dried by sun drying to reduce cost. This conventional drying method was time consuming and may take four days during rainy season, which retards the production of pepper. This paper proposes the swirling fluidized bed drying (SFBD) method, which was known to have high mixing ability and improved solid-gas contact to shorten the drying time of products. A lab scale SFBD system was constructed to carry out this study. Hydrodynamic study was conducted for three beds loadings of 1.0 kg, 1.4 kg at a drying temperature of 90°C. The SFBD has shown excellent potential to dry the pepper with a relatively short drying time compared to the conventional method. Batch drying for the bed loads studied only took 3 hours of drying time only. It was found that bed higher bed loading of wet pepper requires longer drying time due to higher amount of moisture content in the bed. Four distinct regimes of operation were found during drying in the SFBD and these regimes offer flexibility of operation. The total bed pressure drop was relatively low during drying.

Elimination of persistent emerging micropollutants in a suspended-bed photocatalytic reactor: influence of operating conditions and combination with aerobic biological treatment.

A larger, lab-scale photocatalytic suspended-bed reactor using TiO2 sol-gel-coated expanded clay granules as a bed material was evaluated for oxidative removal of the persistent pharmaceuticals doxycycline, prednisolone, amoxicillin, and sulfamethizole, as well as their mixture, in ppm concentrations. The photocatalytic degradation potential of drug molecules increases as their adsorption affinity increases towards TiO2-containing coatings. The performance of the photocatalytic reactor in the removal of drugs was improved by optimizing the fluidization process parameters. The reactor operation at high bed loadings is determined by the abrasion resistance of the catalyst coating. The long-term stability of the coated bed was enhanced by optimal loading, achieving a higher removal rate while placing moderate mechanical stress on the coated granules. The photocatalytic pretreatment decreased the toxicity of doxycycline solutions to several bacterial strains, including the environmental bacterium Pseudomonas putida and bacterial strains freshly isolated from the activated sludge. The treatment of doxycycline-containing water with a combination of photocatalytic treatment and bio-oxidation resulted in 98% removal of the target in the bioreactor outlet, with no deterioration in the operation of the biological process.

Coal particle and bed physical transformational behaviour after thermochemical conversion in a fixed bed

This paper examines the physical transformational behaviour that coal particles and the bed structure undergo in a fixed bed reactor. The transient overfeed configuration is used with feed gas entering from the bottom of the 1.2m reactor with an inner diameter of 104mm. The fuel bed loading, of 3.3kg on average, consisted of non-devolatilized seam two coal of 4, 6 and 8mm particles from the Highveld region in South Africa and was inertinite-rich. Transient exit gas composition and temperature profile inside the fixed bed of particles, is presented along with a full chemical and physical characterisation of the feed coal and the partially converted bed contents consisting of coal, char and ash particles. The bed dissection method implemented was designed to limit mechanical fragmentation by minimizing particle handling and bed structural disturbance during sampling. Particle size distribution and the particle size distribution width showed a significant variation in the oxidation zone and the ash bed which was not previously quantified on industrial scale experiments. The bulk, true as well as the apparent (measured by hydrostatically weighing in mercury) densities are reported for the different reaction zones of pyrolysis, reduction, oxidation and the ash bed, and showed significant variation in each zone. The particles and the fixed bed structural change were established by the measured particle porosity and the fixed bed voidage. The extensive role of particle agglomeration in the lower sections of the fixed bed was demonstrated in the bed voidage data and is evidently tracked as the reaction front moves up through the fixed bed of particles. The mode of operation simulated the transient start-up procedure and subsequent particle and bed transformational behaviour during industrial fixed bed combustion and gasification.

Response characteristics of H2O2 monopropellant thrusters with MnO2-mixed PbO catalyst

As environmental concerns increase, rocket-grade hydrogen peroxide has been considered as one of the candidates for replacing toxic propellants. Various components for the development of monopropellant thrusters using hydrogen peroxide have been studied, including catalysts, catalytic supports, and design parameters in monopropellant thrusters. As a part of these efforts, an experimental investigation, including design parameters, for a catalyst bed is performed with MnO2-mixed PbO catalysts in a hydrogen peroxide monopropellant thruster. In addition to basic performance of the monopropellant thruster, the response characteristics of rising time and tail-off time are compared with respect to two different catalysts. From the experimental results, it is found that a catalyst with high reactivity is much more preferable for reducing not only rising time but also tail-off time. Tail-off time in case of MnO2-mixed PbO is considerably shortened compared to that of MnO2. Moreover, design parameters, such as catalyst capacity and catalyst bed loading, for designing a catalyst bed in a monopropellant thruster can be suggested from an analysis of all experimental results.

Innovative Internally Circulating Reactor Concept for Chemical Looping‐Based CO2 Capture Processes: Hydrodynamic Investigation

AbstractAn experimental hydrodynamic investigation has been carried out for a novel internally circulating chemical looping (ICCL) reactor concept proposed to reduce the technical complexities encountered in conventional chemical looping combustion (CLC) and reforming (CLR) technologies. The concept consists of a single reactor with internal physical separations dividing it into two sections, i.e., the fuel and air sections. The trade‐off for this reduction in process complexity is increased gas leakage between the two reactor sections, so a pseudo‐2D cold‐flow experimental unit was designed. The ICCL concept remains highly efficient in terms of CO2 separation while ensuring significant process simplifications. The solids circulation rate also proved easy to control by adjusting the fluidization velocity ratio and the bed loading. In the light of the excellent hydrodynamic performance, the ICCL concept appears to be well‐suited for further development as a CLC/CLR reactor model.

Chemical filtration of Cr (VI) with electrospun chitosan nanofiber membranes

Chitosan nanofibers (average diameter of 75nm) were electrospun on polyester (PET) scrim to form composite nanofiber membranes with controlled pore size. The membranes were then stacked as a membrane bed for chemical filtration of Cr (VI) of 1–5mg/L. The performance of the bed with respect to loading capacity at breakthrough, bed saturation and utilization efficiency were carefully investigated. The results showed that while these three parameters were dependent on pH, flow rate, flow distribution and packed pattern of the membrane, the latter two were less affected by feed Cr (VI) concentration and bed length. The maximum bed loading capacity for 1mg/L Cr (VI) filtration at breakthrough was found to be 16.5mg-chromium/g-chitosan, higher than the static adsorption capacity of 11.0mg-chromium/g-chitosan using nanofiber mats, indicating the membranes’ better potential for dynamic adsorption. The minimum bed length required to avoid breakthrough was determined to be three layers of stacked membranes with nanofiber deposition density of 1g/m2 by applying bed depth service time (BDST) model.

Feasibility study on pliant media drying using fluidized bed dryer

The usage of pliant media for blasting in surface preparation has gained substantial interest in various industries, particularly oil and gas. Being a clean technology, this relatively new method of surface preparation has become an alternative to conventional abrasive blasting technique which lowers fugitive emissions from blasting process and hence lowering risk to workers in the industry. Despite proven to be effective and cost efficient, the usage of pliant media in tropical climate poses a new challenge due to the torrential rain in the monsoon season. During rainy and wet conditions, the pliant media was literally soaked and the recovery rate of the pliant media for a continuous blasting becomes retarded. A viable technique for drying of this pliant media has then become imperative. The present study proposes to dry water laden pliant media in a Swirling Fluidized Bed Dryer (SFBD). In this preliminary study, three bed loadings of 1.7, 2.0 and 2.3 kg of pliant media was dried in the SfBd at 80°C, 90°C and 100°C. The experimental works revealed that the SFBD has shown excellent potential to dry the pliant media with a relatively short drying time. The behaviour of moisture ratio and drying rate against time are discussed. The findings conclude that the SFBD is a feasible technique for wet pliant media drying and can be extended for continuous processing system.