Alumina Beads Research Articles

Hybrid Radial‐Axial Flow for Enhanced Thermal Performance in Packed Bed Energy Storage

ABSTRACTIn this work, a hybrid radial‐axial (HRA) system is used to store thermal energy in a packed bed. The heat transfer fluid (HTF) is delivered via a perforated radial pipe placed at the center of the packed bed along the axial length. Hot fluid flows from the center toward the wall through the holes (like other radial systems), but then leaves via the traditional axial flow exit, creating the HRA flow configuration. A computational fluid dynamics (CFD) model is used to analyze the thermal performance of the packed bed during the charging process utilizing the new HRA system. Alumina beads of 6 mm were filler materials and air was HTF with inlet temperature of 75°C for proof of concept. The present paper focuses on two aims: (1) utilizing CFD models to analyze flow and temperature profiles in the packed bed; (2) comparing the model results to experimental results published in a previous HRA flow study and to traditional axial flow. Two HRA configurations were considered based on previous experimental designs, one with uniform holes in the central pipe (R1) and one with gradients in the hole sizes to promote even flow from the central pipe into the bed (R2). The numerical results agree with the experimental results in both cases. The HRA system performance depends on the flow profile created by the hole designs, and it can perform better than the axial flow depending on the design of the radial pipe. Design R2, which promotes even flow from the central pipe into the bed, has higher charging efficiency than standard axial flow methods. For HRA design R2 at 0.0048 m3/s (7 SCFM, standard cubic feet per minute), numerical results for charging efficiency were 75.5% versus 73.8% for traditional axial flow. For HRA design R2 at 0.0061 m3/s (9 SCFM), numerical charging efficiency was 80.5% versus 78.1% for traditional axial flow. These results are consistent with experimental data.

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

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

Hydraulic Transport of Large Solid Particles in Inclined Pipes Under Pulsating Flow Conditions

Abstract The pressure loss due to the hydraulic transport of large solid particles should be predicted for the design of subsea mining systems. The mixture flow in a flexible jumper is expected to be unsteady during lifting operations in an actual mining system. The authors develop a one-dimensional mathematical model that predicts such pressure loss under pulsating mixture flows in a static inclined pipe assuming that the flow in the jumper is fully developed. An experiment is performed on the hydraulic transport of solid particles to obtain data for model validation. In this experiment, several kinds of solid particles are used: alumina beads, glass beads, and gravel. The experimental parameters are mixture velocity, solid concentration, pulsation period and amplitude of water velocity, and pipe inclination angle. The proposed model is validated through a comparison with experimental data. The validation confirms that the model is applicable for the prediction of the pressure loss in inclined pipes under pulsating flow conditions. Furthermore, we calculate the pressure loss due to the hydraulic transport of polymetallic sulfide ores using the proposed model. The calculation results show that the time-averaged pressure loss drastically varies with the pipe inclination angle, reaching its maximum value between the pipe inclination angles of 30 deg and 60 deg, at which the flow is inclined upward. The results also show that the amplitude of pressure loss pulsation differs little between pipe inclination angles and that the pulsation component of pressure loss should be considered in designing lifting systems.

Activation of Periodate for Efficient Degradation of Organic Dyes with Manganese Oxide Supported on Activated Alumina Beads

Activation of Periodate for Efficient Degradation of Organic Dyes with Manganese Oxide Supported on Activated Alumina Beads

Tribological modifications of water flow at liquid–solid interface by nanobubbles

Previous studies investigated on friction reduction at the solid–liquid interface due to the presence of metal nanoparticles and fine bubbles such as microbubbles. This paper experimentally investigated how nanobubbles (ultrafine bubbles) change the tribological nature of water flow at the solid–liquid interface. We flowed air nanobubbles-containing water into a cylindrical cell filled with soda-lime glass, alumina, and high-carbon chromium-bearing steel beads. We then estimated the changes in the ratio of Darcy's friction factor of nanobubbles-containing water flow (fnb) to that of water flow before injecting nanobubbles (fref) with the time of injecting nanobubbles. We found that nanobubbles are capable of reducing the friction in water flow running through the soda glass beads, accounting for up to 6.1% reduction in terms of Darcy's friction factor ratio (fnb/fref) in our experiment. The magnitude of friction reduction by nanobubbles can be greater with a larger total surface area where surface nanobubbles are present. In contrast, nanobubbles encouraged enhancement of the friction of water flow within the high-carbon chromium-bearing steel beads, showing 3.8% enhancement in the friction factor ratio (fnb/fref). The results indicate that nanobubbles play a role in the friction reduction of water flow when the surface of the bead material is rougher than the size of nanobubbles, while nanobubbles enhance the friction of water flow when the bead surface is smooth enough. Therefore, nanobubbles can be a green nanoscopic additive for modifying the friction and lubrication performance of water flow depending on the surface roughness of the flow material.

Phosphorus removal from agricultural tile drainage effluent with activated alumina in novel adsorption reactors.

Subsurface tile drains under agricultural field crops are a major source of phosphorus (P) discharge to aquatic ecosystems, contributing to the eutrophication of surface waters. Adsorption reactors for P removal from drainage water (P-reactors) could reduce P outflow from agricultural land but were rarely studied in cold, temperate climates. In our study, four low-cost P-reactors were installed in agricultural fields in south-central Québec, Canada. Activated alumina (AA) beads were used as P-adsorptive material, and the reactors were connected to tile drain outlets. Paired water samples (39 events) from reactor inlets and outlets were analyzed for P species and other physicochemical parameters during one calendar year to assess the P removal from tile drain effluent in the P-reactors. Collectively, the P-reactors retained approximately half (48%) of the total mass of P flowing through the tile drains, mostly (92%) as particulate P. The mass of AA beads adsorbed 11% of the dissolved-P fractions. Results are interpreted in the context of the field drainage area and will require adjustments to the P-reactor design to accommodate larger fields. The P-reactors remained structurally intact throughout all four seasons in a cold temperate climate, showing the potential of simple, inexpensive P-reactors to reduce P concentration in tile drain effluent.

Axial gas mixing in conical spouted beds with high density particles

Conical spouted beds operating with high-density particles (ρp > 2500 kg/m3) have recently gained attention because of their potential use as nuclear fuel coaters for next-generation nuclear reactors. In the literature, the number of axial gas mixing studies in conical and conical-cylindrical spouted beds is very limited and all axial mixing studies were carried out with relatively light particles (ρp ≤ 2500 kg/m3). Therefore, the objective of this study was to generate experimental data that can be used to explain the gas axial mixing behavior in conical spouted beds operating with both low- and high-density particles. Experiments were conducted in two (γ = 30°, 60°) conical spouted beds with three different types of particles: zirconia (ρp = 6050 kg/m3), zirconia toughened alumina (ρp = 3700 kg/m3) and glass beads (ρp = 2460 kg/m3). In order to be able to compare experimental data obtained at different conditions, a 1-D convection-diffusion gas mixing model originally developed by San José et al. (1995) was implemented to determine the axial dispersion coefficients. The results show that the axial dispersion coefficients range between 1.75×10−2 m2/s and 9.35×10−2 m2/s, increase with superficial gas velocity and are higher than the corresponding dispersion coefficients of fixed beds, lower than the dispersion coefficients of fluidized beds and in the same range with the cylindrical spouted beds reported in the literature. The corresponding Peclet numbers were in the range of 0.6–7.8 for all operating conditions and slightly higher Peclet numbers were obtained with glass beads indicating the relative importance gas convective transport over gas dispersion for light particles compared to heavy particles.

Migration of inert materials during coking of molded coal

Since the maldistribution of substances with poor melting and expansion properties decreases the strength of coke, we investigated whether these substances gather or disperse during coking process. Coal briquettes (before coking) and cokes (after coking) containing a predetermined amount of alumina beads were prepared. These beads constituted 2–15 vol% of the samples. A three-dimensional analytical object was constructed by X-ray CT images of coal briquette or coke with alumina beads, and isolated alumina beads were extracted from analytical objects by image processing. The number of isolated alumina beads increased after coking in any mixing ratios. Therefore, it was shown that the alumina beads dispersed each other during coking. The observed result could be attributed to the expansion of pores near the contact points between agglomerated alumina beads, resulting in the expulsion of the beads. At the lower part of the sample, where the effect of expansion was small, the same ash before and after carbonization can be found. Focusing on the area near the ash, alumina beads with the same distance from the same ash are observed before and after the coking. This indicates that there are alumina beads that have not moved during coking. The reason why the alumina beads did not move may be using low fluidity coal and high-density coal briquette as the raw material of coke. This suggests that the high-density coal briquette may prevent the coke strength from decreasing due to the suppression of insoluble matter agglomeration.

Batch and Continuous Flow Treatment Studies of Trichloroethylene Contaminated in Water by Silver and Cerium Doped Zinc Oxide Adsorption and Photocatalysis

The development of photocatalytic treatment in continuous flow systems to be more practical is challenging. This research aimed to study batch and continuous flow treatment of trichloroethylene (TCE) contaminated in water by silver and cerium doped zinc oxide (0.005Ag-0.005Ce-ZnO) visible light driven photocatalyst. This catalyst was selected to represent the green route synthesis with simplicity and ease of upscaling. The 0.005Ag-0.005Ce-ZnO powder was synthesized using sticky rice flour as a template. Mechanical coating of the 0.005Ag-0.005Ce-ZnO powder on activated alumina (Al2O3) beads was done to improve the appropriate packing in the fixed bed columns. Characterization of 0.005Ag-0.005Ce-ZnO showed a higher response to visible light and smaller crystallite size compared to zinc oxide synthesized with the same method. Using sticky rice starch as a template increased the uniform distribution of the elements. The photocatalytic batch test over 0.005Ag-0.005Ce-ZnO powder, 0.30 g/100 mL, could remove TCE up to 80% in 180 min. The decrease of TCE via photocatalysis compared to volatilization, adsorption, and photolysis presented the predominance of photocatalysis. Langmuir-Hinshelwood kinetics described that the decrease of TCE more depended on the reaction than adsorption. In addition, the TCE degradation steadily remained at 80-90% along the run of 0.005Ag-0.005Ce-ZnO@Al2O3 photocatalysis under visible light from both warm white lamps and sunlight in the continuous flow system. Besides photocatalysis, TCE adsorption on 0.005Ag-0.005Ce-ZnO@Al2O3 packed in the columns showed significant results. Our findings presented the possibility of applying the photocatalytic continuous flow system to remove TCE in industrial wastewater.

Hydrothermal acid etching of alumina beads and its effect on isobutane dehydrogenation performance over Pt/γ-Al2O3 catalyst

Millimeter-scale spherical alumina used as the support of Pt catalyst for isobutane dehydrogenation was prepared by alginate assisted sol-gel method, and then hydrothermal treated in 0.5 M HNO3 to improve its porous structure and surface properties. The effects of acid etching time on the composition, structure, surface acidity, redox property, catalytic dehydrogenation performance and carbon deposition of catalyst were investigated by ICP-OES, SEM, TEM, XRD, N2 adsorption-desorption, 27Al MAS NMR spectra, NH3-TPD, H2-TPR, isobutene transient response experiment and TGA. The results show that the acid treatment can effectively remove zinc species and partial aluminum from the surface of alumina beads, which can create defect sites and increase the specific surface area of alumina, thus improving the dispersion of Pt particles. In addition, acid etching significantly increases the acidity of alumina and enhances the interaction between Pt particles and alumina through the formation of defect sites. The Pt/Al2O3-NA-3 possesses the smallest size of Pt particles, the strongest Pt-alumina interaction, maximum number of acid sites and the highest isobutene yield of 33% even after 270 min reaction.

Construction of 3D-sized Mn (II)-doped MoS2@activated alumina beads as PMS activator for tetracycline degradation under light irradiation

In this work, Mn (II) was doped into MoS2 structure and then anchored on activated alumina beads to construct 3D-sized composites (Mn-MoS2@AABs). This component material was used as PMS activator for tetracycline (TC) degradation under light irradiation. According to experiment results, Mn-MoS2@AABs exhibited well degradation performance to TC, which ascribed to excellent photo-response property of Mn-MoS2 and activation of Mn. Importantly, the 3D-sized structure made it facilely be recycled from solution, which catered to the demand for the practical application. Therefore, the novel strategy of designing Mn-MoS2@AABs had great significance for environmental restoration.

Response Surface Methodology Optimized Eriochrome Black T Dye Removal Using Alumina Beads: Isotherms and Kinetics Studies

Numerous approaches have been investigated for the development of cheaper and more effective technologies to improve the quality of industrial effluent. However, adsorption has been one of the most simplest and economical remediation technology in the treatment of wastewaters. In this study, commercial alumina beads (Al-beads) were utilized for the adsorption of Eriochrome Black T dye. The adsorption process was optimized using the RSM model by Box-Behnken Design (BBD). From the optimization result, the most influential variables are; the initial dye concentration, the interaction between adsorbent dosage with itself, and that of adsorbent dosage with initial dye concentration. The R2 value of 0.7743 implies that 77.43% on the percent dye removal could be due to the variation in the independent variable. Whereas the Adeq. precision of 6.493, and lack of fit (0.92) implies the model can be used to navigate the design space. Up to 98.28%, dye removal was attained using the Al-beads under the conditions; pH of 12.39, adsorbent dosage (1.25 g), and initial dye concentration (175 ppm). The sorption data indicated that the adsorption process was fitted to Freundlich and Temkin isotherm models, while for the kinetics study, the pseudo-second-order model was the best fit. Furthermore, the adsorption mechanism was found to be governed majorly by intra-particle diffusion with some contribution from external mass transfer diffusion.

Construction of MoS2@Activated Alumina Beads as Catalysts for Rapid Gold Recovery from Au(S2O3)23– Solution

Gold recovery from thiosulfate leaching solution Au(S2O3)23- is regarded as a tough task because of the low efficiency and complex procedure in current technology, which hindered the industrial application of this eco-friendly technique. In this work, a MoS2@activated alumina bead composite (MoS2@AA) was constructed through a simple hydrothermal anchoring method and served as a catalyst to recover gold from Au(S2O3)23- solution for the first time. The microstructure and chemical component of MoS2@AA were systematically analyzed. In addition, batch experiments were carried out to explore the recovery behavior of Au(S2O3)23- (concentration: 10 to 200 ppm). Ascribing to the extraordinary optical property of MoS2@AA, Au(S2O3)23- could be directly reduced to Au0 by photogenerated electrons and then form a two-phase interface of gold/MoS2@AA. As a result, the recovery of Au(S2O3)23- can reach up to 98% on MoS2@AA, which was much higher than traditional methods. More importantly, the reduced Au0 could be desorbed from MoS2@AA through a supersonic method, achieving one-step Au0 recovery from Au(S2O3)23-. This novel strategy used in this research has great significance to the development of Au(S2O3)23- recovery in the future.

Functionalization of Diamine-Appended MOF-Based Adsorbents by Ring Opening of Epoxide: Long-Term Stability and CO2 Recyclability under Humid Conditions.

Although diamine-appended metal-organic framework (MOF) adsorbents exhibit excellent CO2 adsorption performance, a continuous decrease in long-term capacity during repeated wet cycles remains a formidable challenge for practical applications. Herein, we present the fabrication of diamine-appended Mg2(dobpdc)-alumina beads (een-MOF/Al-Si-Cx; een = N-ethylethylenediamine; x = number of carbon atoms attached to epoxide) coated with hydrophobic silanes and alkyl epoxides. The reaction of epoxides with diamines in the portal of the pore afforded sufficient hydrophobicity, hindered the penetration of water vapor into the pores, and rendered the modified diamines less volatile. een-MOF/Al-Si-C17-200 (een-MOF/Al-Si-C17-y; y = 50, 100, and 200, denoting wt % of C17 with respect to the bead, respectively), with substantial hydrophobicity, showed a significant uptake of 2.82 mmol g-1 at 40 °C and 15% CO2, relevant to flue gas concentration, and a reduced water adsorption. The modified beads maintained a high CO2 capacity for over 100 temperature-swing adsorption cycles in the presence of 5% H2O and retained CO2 separation performance in breakthrough tests under humid conditions. This result demonstrates that the epoxide coating provides a facile and effective method for developing promising adsorbents with high CO2 adsorption capacity and long-term durability, which is a required property for postcombustion applications.

Metal-organic framework on porous TiO2 thin film-coated alumina beads for fractional distillation of plant essential oils.

Fractionation of essential oils is technically challenging due to enormous scaffold diversities and structural complexities as well as difficulties in the implementation of the fractionation in the gas phase. Packing beads with multi-dimensional hierarchical nanostructures have been developed herein to pack fractional columns for atmospheric distillations. Activated alumina beads were coated with a porous TiO2 thin film. Growth of Cu-BTC (benzene-1,3,5-tricarboxylate) crystals in resultant porous surfaces leads to the generation of new nanopores and increased metal centers for differential coordination with diverse components of essential oils. The TiO2 thin film is not only an integral part of the composites but also induces the oriented growth of Cu-BTC metal organic framework (MOF) crystals through coordinative interactions. These Al2O3@TiO2@Cu-BTC MOF beads show very strong absorptive capability for major components of essential oils, except for a single cyclic ether eucalyptol with steric hindrances. The eucalyptol was fractionated by using the column packed with those modified alumina beads from raw materials of Artemisia argyi, and Rosmarinus officinalis with high purities up to 96% and 93%, respectively.

Optimization of operating conditions on ultra-fine coal grinding through kinetic stirred milling and numerical modeling

This study investigated ultra-fine coal grinding performance of four low- to moderate-cost grinding media in a laboratory stirred mill. Kinetic grinding tests showed that silica beads generated the finest product size with a P80 of 5.9 μm from a feed size of 24.4 μm while having a specific energy (SE) input of 309 kWh/ton. Nonetheless, the least energy consumption of 109 kWh/ton was achieved by alumina beads; however, yielding a coarser product size of 15.5 μm. In addition, test results indicate that optimizing media sizes, solids concentration, and using viscosity modifiers enhance coal ultra-fine grinding performance. Under the optimized testing conditions, a P80 of 2.7 μm was produced with a corresponding SE input of 270 kWh/ton using silica beads ranging from 420 to 850 μm and a dispersant dosage of 14 kg/ton. Moreover, the mathematical models generated based on population balance modeling provided an accurate forecast of the particle-size distribution.

Alumina beads decorated copper-based coordination polymer particle filter for commercial indoor air cleaner

This paper provided an insight into the dual functionalities of air filter for the removal of multiple volatile organic compounds (VOCs) and Escherichia coli (E. coli) pathogen pollutants. In this regard, a cost-effective and eco-friendly method was developed to grow copper coordination polymer particles (Cu-CPP) onto porous alumina (Al2O3) support, resulting in the formation of Cu-CPP /Al2O3 composite beads. The use of coordination polymer particles can allow more control of the physical and chemical properties of the adsorptive materials at a molecular level through rational selection of metal nodes and organic ligands. Notably, excellent toluene adsorption capacities (256.97 mg g−1) and breakthrough behaviors were observed in Cu-CPP/Al2O3 beads. For the first time, the Cu-CPP/Al2O3 beads air filter was successfully scaled up and installed on a commercial air cleaner with 1 m3 test chamber for various VOCs adsorption. The Cu-CPP/Al2O3 beads air filter exhibited removal efficiency for formaldehyde (99.5%), toluene (99.5%), acetic acid (100%) and ammonia (100%), which are superior to conventional activated carbon. The E. coli was chosen as a model for testing the inactivation performance. The Cu-CPP/Al2O3 beads showed an efficiency of 97.02%, which was substantially higher than that of activated carbon (43.78%) after 120 min of exposure. This research paves the way for the development of multifunctional air filters based on copper coordination polymer particles, which would be excellent for commercial indoor air cleaner applications.

Differential surface partitioning for an ultrasensitive solid-state SERS sensor and its application to food colorant analysis

Solid-state SERS sensors are desirable point-of-care tools due to their portability. However, the level of SERS sensitivity achieved in liquid phase is rarely duplicated in the solid phase. We report herein the fabrication of a SERS sensor using alumina beads as the solid support and demonstrate its high SERS sensitivity with the model analyte 4-aminophenyl disulfide (4-APDS). The key to sensitivity is a hydrophilic-hydrophobic surface gradient constructed by sequentially coating with the surfactant cetyltrimethylammonium bromide and fluorous 1H,1H,2H,2H-perfluorooctyltriethoxysilane. The surface gradient, together with chloride etching, allows the detection of 4-APDS at the low concentration of 10−15 M. The practicality of the sensor beads is evidenced by successfully tracking the SERS fingerprints of five food colorant standards in the SERS spectra of a popular candy product. These SERS sensor beads are easy to prepare, convenient to use, and highly responsive as a SERS platform for the analysis of colorants.

Formation and occurrence characteristics of methane hydrate in the complex system of sodium dodecyl sulfate and porous media

ABSTRACT In recent years, porous media have attracted a lot of attention due to the enhanced kinetics of hydrate formation. However, how porous media promote hydrate formation is still an open topic. In this study, two different porous media, activated alumina and glass beads (average particle size 1, 3, 5 mm), were mixed with sodium dodecyl sulfate (SDS) to promote methane hydrate formation (275.15 K, 6 MPa). The smaller the particle size is, the better the promoting effect of porous media is, corresponding to faster formation kinetics and higher gas consumption. The average hydrate formation rate (2.3 mmol/min) and T90 (136 min) in the 1 mm activated alumina system was 2.6 and 0.4 times higher than the average hydrate formation rate (0.9 mmol/min) and T90 (349 min) in the 3 mm activated alumina system, respectively. Better performance of activated alumina particles than that of glass beads because of its rich micropores and unique electric double layer distribution in solution. The gas storage density of hydrate in the 1 mm alumina system can reach 129.13 Vg/Vh, while the highest gas storage density of hydrate in the 1 mm glass bead system was 122.35 Vg/Vh, which was similar to that of hydrate in the 3 mm activated alumina system (123.63 Vg/Vh). The gas consumption of the system was not affected by mass transfer but was controlled by particle size and solution volume with the presence of SDS. Under supersaturated and saturated conditions, it is found that the porous media bed and hydrate layer moved upward under the action of capillary force and methane gas driving force. This work provides a reference for the formation and occurrence of hydrates with the presence of porous media and surfactants.

Experimental study on packed-bed thermal energy storage using recycled ceramic as filler materials

Thermal energy storage (TES) is used in renewable energy systems such as concentrated solar power (CSP) or electric thermal energy storage (ETES) plants to provide heat for dispatchable power production. This paper presents the experimental results of a new 100% recycled ceramic material, ReThink Seramic - Flora, for used in sensible heat packed-bed thermal energy storage. Results are compared to conventional α-alumina (alumina) materials. The study focuses on a full charge-discharge cycle and multiple repeated partial charge-discharge cycles. Air was used as the heat transfer fluid (HTF) with an inlet temperature of 150 °C. Three flow rates were considered in the study, 0.0034 m3/s, 0.0048 m3/s, and 0.0061 m3/s (5–9 SCFM). The thermal performance of ReThink Seramic - Flora was analyzed and compared to alumina in terms of energy stored/recovered, temperature distribution, thermal exergy efficiency, pressure drop, and net exergy efficiency (combined thermal and pressure drop losses). The results showed that alumina beads have higher performance in terms of thermal exergy efficiency than ReThink Seramic - Flora. The exergy efficiency increased from 46.8% to 55.4% for alumina and from 44.6% to 51.6% during full charge/discharge process at three flow rates. Pressure drop results indicate exergy losses over the flow rates from 3.6% to 7.9% for alumina and 2.5% to 5.1% for ReThink Seramic - Flora. This results in net exergy efficiencies at the three flow rates of 43.2%, 47.1%, and 47.5% for alumina compared to 42.1%, 45.4%, and 46.5% for ReThink Seramic - Flora.