Metal Packing Research Articles

Pressure drop analysis for potential heat transfer applications using metallic foam packing in rotating packed bed

Pressure drop analysis for potential heat transfer applications using metallic foam packing in rotating packed bed

Controlling the Crystal Packing and Morphology of Metal–Organic Macrocycles through Side-Chain Modification

Controlling the Crystal Packing and Morphology of Metal–Organic Macrocycles through Side-Chain Modification

Experimental investigation and modeling of the impact of random packings on mass transfer in fluidized beds

This study investigates the impact of two novel settings of bubbling fluidized beds equipped with random metal packings on the mass transfer. To do this, a comprehensive approach is applied that integrates experiments and modeling and explores the relevance of the different underlying mechanisms involved in interphase mass transfer in fluidized beds. Firstly, the mass transfer of water from moisturized silica gel particles to dry air is studied in both a packed-fluidized bed and a freely bubbling bed with no packing. The experimental set-up consists of a cylindrical bubbling fluidized-bed column with an inner diameter of 22 cm. Silica-gel particles with a mean particle diameter of 797 μm are used as bed material. The total bed amount ranges from 4 to 8 kg, while the fluidization number (F) varies between 1.7 and 2.3. Two types of packing, RMSR (stainless steel thread saddle rings) and Hiflow (stainless steel pall rings) are examined and compared to the reference case of a bubbling bed with no packing. The height of the packed section is maintained at 60 cm. The results show that, at all operating conditions, the use of packings enhances the amount of desorbed water in the fluidized bed. The increase is up to 17%, as compared to the bed without packing. The effect is believed to be inhibition of bubble growth in the packed-fluidized bed. To study this further, a mass-transfer model is introduced to analyze the different mass-transfer steps (intra-particle, particle surface to emulsion gas, and emulsion gas to bubble gas) in packed-fluidized beds compared to beds with no packing. TGA experiments are applied to describe the intra-particle mass transfer through a desorption kinetic model. Model analysis shows that the main resistance for mass transfer occurs across the bubble-emulsion boundary. The calculated value of the mass transfer coefficient for this, Kb, at reference conditions (6 kg of silica gel and F = 2.3) is 7.6e-5 s−1 with packings (in average) and 6.2e-5 s−1 without packings, i.e. a 23% improvement in the governing mass-transfer coefficient.

Limitations of Liquid Electrolyte RDE Experiments for the Determination of OER Catalyst Activity: The Effect of the Catalyst Layer Thickness

Developing novel oxygen evolution reaction (OER) noble metal catalysts with a low metal packing density is key for the wider large-scale implementation of polymer electrolyte membrane water electrolysis (PEMWE). OER activities of these new catalysts are commonly measured in liquid electrolytes using half-cell configurations, such as rotating-ring-disk electrodes (RDE). Recent studies in liquid electrolyte cells showed that the accumulation of microscopic oxygen bubbles within the OER catalyst layer causes shielding of active catalyst sites. In this study, three different OER catalysts were screened for their activity at different loadings in a liquid electrolyte RDE setup. Potential sweeps using bare Ir black, a commercially available IrO2/TiO2 and a homemade Ir/ATO (antimony doped tin oxide) catalyst with different loadings were performed. It was demonstrated that the mass activity of the Ir/ATO catalyst decreases by more than 50% with a catalyst loading increase, which is attributed to the accumulation of microscopic oxygen bubbles within the catalyst layer and was correlated to the coating thickness of the catalyst layer. We suggest screening the OER catalyst activity of low packing catalyst materials in a loading analysis by testing minimum three different loadings within the kinetic Tafel slope region to avoid underestimation of the catalyst activity.

Thiacalix[4]arene Etching of an Anisotropic Cu70H22 Intermediate for Accessing Robust Modularly Assembled Copper Nanoclusters.

Atom-precise metal nanoclusters (NCs) with large bulk (nuclearity >60) are important species for insight into the embryonic phase of metal nanoparticles and their top-down etching synthesis. Herein, we report a metastable rod-shaped 70-nuclei copper-hydride NC, [Cl@Cu70H22(PhC≡C)29(CF3COO)16]2+ (Cu70), with Cl- as the template, in which the Cl@Cu59 kernel adopts a distinctive metal packing mode along the bipolar direction, and the protective ligand shell exhibits corresponding site differentiation. In terms of metal nuclearity, Cu70 is the largest alkynyl-stabilized Cu-hydride cluster to date. As a typical highly active intermediate, Cu70 could undergo a transformation into a series of robust modularly assembled Cu clusters (B-type Cu8, A-A-type Cu22, A-B-type Cu23, and A-B-A-type Cu38) upon etching by p-tert-butylthiacalix[4]arene (H4TC4A), which could not be achieved by "one-pot" synthetic methods. Notably, the patterns of A and B blocks in the Cu NCs could be effectively modulated by employing appropriate counterions and blockers, and the modular assembly mechanism was illustrated through comprehensive solution chemistry analysis using HR-ESI-MS. Furthermore, catalytic investigations reveal that Cu38 could serve as a highly efficient catalyst for the cycloaddition of propargylic amines with CO2 under mild conditions. This work not only enriched the family of high-nuclear copper-hydride NCs but also provided new insights into the growth mechanism of metal NCs.

Disc‐Like Silver Nanocluster Ag93 Built with Bicapped Hexagonal Prismatic Ag15 and Ino Decahedral Ag13 Units

AbstractThe reduction of alkynyl‐silver and phosphine‐silver precursors with a weak reducing reagent Ph2SiH2 led to the formation of a novel silver nanocluster [Ag93(PPh3)6(C≡CR)50]3+ (R=4‐CH3OC6H4), which is the largest structurally characterized cluster of clusters. This disc‐shaped cluster has a Ag69 kernel consisting of a bicapped hexagonal prismatic Ag15 unit wrapped by six Ino decahedra through edge‐sharing. This is the first time that Ino decahedra are used as a building block to assemble a cluster of clusters. Moreover, the central silver atom has a coordination number of 14, which is the highest in metal nanoclusters. This work provides a diverse metal packing pattern in metal nanoclusters, which is helpful for understanding metal cluster assembling mechanisms.

Disc-Like Silver Nanocluster Ag93 Built with Bicapped Hexagonal Prismatic Ag15 and Ino Decahedral Ag13 Units.

The reduction of alkynyl-silver and phosphine-silver precursors with a weak reducing reagent Ph2 SiH2 led to the formation of a novel silver nanocluster [Ag93 (PPh3 )6 (C≡CR)50 ]3+ (R=4-CH3 OC6 H4 ), which is the largest structurally characterized cluster of clusters. This disc-shaped cluster has a Ag69 kernel consisting of a bicapped hexagonal prismatic Ag15 unit wrapped by six Ino decahedra through edge-sharing. This is the first time that Ino decahedra are used as a building block to assemble a cluster of clusters. Moreover, the central silver atom has a coordination number of 14, which is the highest in metal nanoclusters. This work provides a diverse metal packing pattern in metal nanoclusters, which is helpful for understanding metal cluster assembling mechanisms.

The manufacture and reliability analysis of the all-rigid Fabry–Perot resonator for fiber-optic acoustic sensors

By the continuous development of aerospace, petroleum exploration, and other industrial fields, the fiber-optic acoustic sensor (FOAS) with high reliability is a desideration sensor, which can be used for noise monitoring in the extremely harsh environment. The FOAS based on the all-rigid Fabry–Perot resonator (FPR) relies on the new acoustic sensitive principle, where the change in the air refractive index is induced by sound waves and gets rid of the distortion caused by the mechanical characteristics of the acoustic sensor based on the movable parts. So, the FPR-based FOAS is very suitable for acoustic sensing in the harsh environment. In this paper, the reliability of this kind of FOASs is simulated and analyzed. The modal and anti-vibration simulation results of FPR with different sizes show that the FPR has a high natural frequency, and the external vibration environment does not affect the acoustic sensitivity of the FPR. The micro and small-batch all-rigid FPR can be manufactured by the optical contact. Moreover, the FPR can withstand the high temperature of 500°C that is verified by rapid heat treatment equipment. In order to improve the reliability of the FOAS, the metal packing shell is designed and fabricated. Moreover, the vibration and high-temperature tests of the packaged sensor are carried out. The two groups of tests show that the sensor can work normally under 10 g of acceleration vibration and 200°C high temperature, respectively. Therefore, the FOAS based on the FPR has high reliability and is very suitable for noise monitoring in the extreme harsh environment of various industrial fields. Furthermore, the research results of this paper will enhance the competitiveness and influence of the commercialized FOAS.

Electrical resistance through the metallic granular packings

The resistance drop with time in metallic granular materials has been the subject of research since the 19th century, but it is still not fully clarified. The wider application of granular materials in the industry has contributed to the increased interest in this phenomenon. The key parameters that are mainly examined are as follows: the influence of different packings, dimensions, and shapes of the granules, as well as the influence of the pressure, exerted on them. However, there is a limited number of papers that examine the temporal evolution of the resistance in these materials. In this report, we investigate how different packings of two-dimensional stainless steel beads (inox) as well as different currents injected into them affect the temporal evolution of resistance. We also examine the effect of the breaks in the current flow for the current varied between 0.2 and 8 mA for both inox beads as well as low-carbon steel cylinders. The results show the drop of resistance over time for all current values, which is more pronounced in earlier stages of the time evolution. Interruptions in current flow cause an immediate decrease of resistance in both materials.

Inside Back Cover: Directing the Morphology, Packing, and Properties of Chiral Metal–Organic Frameworks by Cation Exchange (Angew. Chem. Int. Ed. 34/2022)

Predicting crystal morphologies is challenging because of the many factors influencing their growth. Dan Oron, Michal Lahav, Milko E. van der Boom, and co-workers demonstrate in their Research Article (e202205238) how metal cation exchange in metal–organic frameworks (MOFs) results in a series of chiral crystals having a similar morphology, packing, and a rare space group (P622). The fact that the crystals maintain their morphology facilitates a quantitative comparison of their optical and magnetic properties. The metal cation exchange is likely to be mediated by differently sized nanochannels.

Innenrücktitelbild: Directing the Morphology, Packing, and Properties of Chiral Metal–Organic Frameworks by Cation Exchange (Angew. Chem. 34/2022)

Innenrücktitelbild: Directing the Morphology, Packing, and Properties of Chiral Metal–Organic Frameworks by Cation Exchange (Angew. Chem. 34/2022)

Determination of volumetric mass transfer coefficients of structured packings at two different column diameters

Considerable work has been done on method standardization for experimental characterization of column packings used in absorption processes. A detailed framework for determination of packing hydraulics as well as gas- and liquid-side volumetric mass transfer coefficients (kGa and kLa) has been established. Packing characterization experiments in large diameter columns result in high equipment and operating costs. Accurate extrapolation of packing properties from experiments in smaller diameter columns would therefore be highly desirable. However, diameter influence is currently not completely understood, making further work necessary. In this work, experiments for the determination of kGa and kLa values were carried out and evaluated independently in two plants (inner diameters 422 and 150 mm). Results from measurements conducted with three metal packings RSP 250Y, RMP N 250X and RMP N 250Y are in good agreement with existing literature data. kGa was found to be dependent on column diameter with larger diameters leading to increased kGa values. The overall effect (approx. 15 %) is consistent with previous works, suggesting the possibility of deriving appropriate scaling factors once the findings are validated by a larger sample size. No clear dependence of kLa values on diameter was found with deviations significantly smaller than for kGa measurements.

Prediction of separation efficiency of structured and stacked packings under low and normal pressure

This work presents a model for the prediction of the separation efficiency of packed columns filled with structured metal sheet packings and stacked packings of different materials and types for distillation and absorption processes. For model validation, packings of sheet metal, ceramic and plastic of various shapes and sizes such as Mellapak, Montz-Pack, Gempak, Ralu-Pak, metal and ceramic Impulse packing IP50 and IP100 and various other types of regularly arranged packings such as 50 mm ceramic Pall rings, 25 and 50 mm metallic Białecki rings, 50 mm PSL rings made of metal and 50 mm plastic Hiflow were investigated using absorption and distillation test systems under low pressure and atmospheric conditions in columns with diameters ranging between 0.15 and 0.60 m. The model was validated in the operating range below the flooding line for FV 0.90 FV,Fl and for turbulent liquid flow ReL ≥ 2. The comparison of the predicted values with measured data presented in this work has confirmed that the presented model is suitable for determining the separation efficiency not only for sheet metal structured packing, but also for regularly arranged stacked packings filled with packing commonly used as random packing for absorption and distillation systems under vacuum and normal pressure. The calculation example shows also the application of the presented model for predicting the separation efficiency nt/H of sheet metal packings and stacked packings with a specific packing area a from 60 up to 500 (750) m²/m³ for distillation processes under low and normal pressure.

Modeling strategies for sensible heat thermal energy recovery through packed beds

A considerable amount of industrial heat is wasted to the atmosphere. This valuable energy could be recovered through fixed bed systems by sensible or latent heat. Mathematical modeling and experimental study of a fixed bed thermal energy recovery system by sensible heat are presented in this paper. An experimental setup was constructed in which air and water were utilized as the charging and discharging process heat transfer fluids, respectively. Three different materials including silica-ceramic, alumina-ceramic, and metal with different sizes were used as the energy storage material. Mathematical modeling was performed at three different levels to analyze the system behavior. The difference among the various modeling levels was in their simplifying assumptions. The resulting equations in each level of modeling were numerically solved. Validation of the modeling results against the experimental data was performed to evaluate the capability of the developed models in prediction of the system actual behavior. Level I model with an average error of 24 % in the charging process and 11 % in discharging process showed unsuitable results, while level II and level III models showed approximately the same and acceptable results with 5 % and 9 % average errors in charging and discharging processes, respectively. Then level II model was selected for prediction of the system performance due to its less complexity compared to level III model. Finally, the influence of the packings material, packing size, and inlet air velocity and temperature on the system performance was predicted using level II model. The system yield had the highest value for all packings at the entering air highest temperature and lowest superficial velocity examined. Metal packings showed better performance and had an experimental system yield of 54 % and 67 % at the entering air highest temperature and lowest superficial velocity, respectively. It was also observed that metal packings outperformed other packings and had the highest experimental yield of 58 % at the same operating conditions. Besides, the highest experimental yield of 61 % was achieved by packings with the smallest size (13 mm) at the highest entering air temperature (140 °C). Based on the findings of this study it can be concluded that lower inlet air velocity and higher inlet air temperature enhanced the recovery efficiency. Besides, the smaller metal packings size showed higher recovery efficiency.

Directing the Morphology, Packing, and Properties of Chiral Metal–Organic Frameworks by Cation Exchange**

AbstractWe show that metal–organic frameworks, based on tetrahedral pyridyl ligands, can be used as a morphological and structural template to form a series of isostructural crystals having different metal ions and properties. An iterative crystal‐to‐crystal conversion has been demonstrated by consecutive cation exchanges. The primary manganese‐based crystals are characterized by an uncommon space group (P622). The packing includes chiral channels that can mediate the cation exchange, as indicated by energy‐dispersive X‐ray spectroscopy on microtome‐sectioned crystals. The observed cation exchange is in excellent agreement with the Irving–Williams series (Mn<Fe<Co<Ni< Cu>Zn) associated with the relative stability of the resulting coordination nodes. Furthermore, we demonstrate how the metal cation controls the optical and magnetic properties. The crystals maintain their morphology, allowing a quantitative comparison of their properties at both the ensemble and single‐crystal level.

Chemical Looping Combustion in a Packed Fluidized Bed Reactor─Fundamental Modeling and Batch Experiments with Random Metal Packings

The conversion of gaseous fuels during chemical looping combustion (CLC) was investigated in a packed fluidized reactor. The experimental setup consisted of a cylindrical laboratory-scale bubbling fluidized bed reactor with an inner diameter of 78 mm and a height of 1.27 m. Two types of fuel, syngas (50:50% H2/CO) and carbon monoxide (100% CO), were used. Two different types of packings were assessed and compared to the reference case, which was a bubbling bed with no packings. The investigated packings were 25 mm stainless-steel thread saddle rings (RMSR) with a bulk density of 195 kg/m3 and 25 mm stainless-steel pall rings (Hiflow) with a bulk density of 271 kg/m3. The height of the packed reactor section was kept constant at 1 m. Ilmenite concentrate particles in the size range of 90–212 μm was used as an oxygen carrier. The unfluidized bed height was varied between 10 and 60 cm. The results show that the fuel conversion increases as the bed height increases and that the use of packings have a positive effect on fuel conversion. For RMSR packings, the syngas conversion at 840 °C improves from 0.84 (for 10 cm bed height) to 1.00 (for 60 cm bed height). This should be compared to the bed with no packings, for which the corresponding improvement was from 0.69 to 0.98. The general pattern is consistent for all fuels, packings, and bed heights. The results are interpreted as an improvement in gas–solid mass transfer when packings are used, mainly as a result of the reduced bubble size. A fundamental analysis of the variance in the pressure drop over the bed to estimate the bubble diameter supports this interpretation. It is also shown that the mass-based first-order effective reaction contact factor kf improves up to 109% in the bed with RMSR packings compared to the bed without packings.

Experimental investigation of methane hydrate formation in the presence of metallic packing

Clathrate hydrates gained significant attention as a viable option for large-scale storage of natural gas, primarily methane (CH4). Unlike employing the nanoconfinement for enhancing the nucleation sites and hydrate growth as in the porous materials, whose synthesis is often associated with high costs and poor batch reproducibility, a new approach for promoting CH4 hydrates using pure water (H2O) in an unstirred reactor packed with stainless steel beads (SSB) was proposed in this fundamental work, where the interstitial space between the beads was exploited for enhanced hydrate growth. SSB of two diameters, 5 mm and 2 mm, were used as.a packed bed to investigate their effects on CH4 hydrate formation at 273.65 K, 275.65 K, and 277.65 K with an initial pressure of 6 MPa. The thermal conductivity of SSB packing potentially aided hydrate growth by expelling the hydration heat, while, the results also revealed that driving force has a substantial impact on the rate of CH4 hydrate formation and gas uptake. The experiments conducted in both 5 mm and 2 mm SSB packed bed reactors showed a maximum gas uptake of 0.147 mol CH4/mol H2O at 273.65 K with water to hydrate conversion of 84.42% with no significant variation. The results established the promotion effect on the kinetics of CH4 hydrate formation in the unstirred reactor packed with 2 mm SSB due to the availability of more interstitial space offering multiple nucleation sites for CH4 hydrate by providing a larger specific surface area for H2O-CH4 reaction. Experiments with varying H2O content were also performed and the results showed that the water to hydrate conversion and rate of hydrate formation could be enhanced at a lower H2O content in a packed bed reactor. This study demonstrates that the use of costly or intricate porous materials can be made redundant, by exploiting the interstitial voids in packing of cheap and widely available SSB as a promising alternative material for enhancing the kinetics of artificial CH4 hydrate synthesis.

Experimental Characterization of 3D Printed Structured Metal Packing with an Enclosed Column Wall

AbstractAdditive manufacturing is a promising tool for tailored solutions in chemical engineering. This applies in particular to the design of lab‐scale packed bed columns. We present experimental results to characterize a lab‐scale 3D printed structured metal packing and compare it to a conventional counterpart. The results indicate that necessary adjustments for the manufacturing process of the metal material have an influence on important operating parameters, resulting in higher specific pressure drop, slightly higher liquid holdup and lower mass transfer efficiency.

Experimental Investigation of Methane Hydrate Formation in the Presence of Metallic Packing

Experimental Investigation of Methane Hydrate Formation in the Presence of Metallic Packing

Performance analysis of humidifier packing for humidification dehumidification desalination system

The Humidification Dehumidification (HDH) desalination system is a promising method for production of potable water in isolated locations. Among different component constituting the HDH desalination system, humidifier and its packing are paramount factors in determining system productivity. Several experimental investigations were conducted to study the influence of packing on humidifier performance. However, numerical analysis dealing with performance of humidifier packing is still not available. Such an investigation will be useful to select the optimized packing for a humidifier. In the present work, performance analysis of 15 different types of random packing have been carried out using Scilab software. From this study, it is concluded that metal packing with highest surface area to volume ratio, lowest packing factor and smallest packing diameter functions as the best humidifier packing. Experimental study was also conducted in a pilot plant of open air open water HDH cycle using pall ring 25 mm diameter metal packing, which has shown the highest performance index in the numerical study. Experimental results obtained were found to be in agreement with the numerical results. Present work is a useful tool in designing new packing material of desired properties since the packing performance is a strong function of its geometrical properties.