Single Pellet Research Articles

A Comparison Between the Reduction Behavior of DRI and BF Pellets in H2 and CO Atmospheres

AbstractThe reduction behavior of two different iron ore pellets that are used in blast furnace (BF) and direct reduction (DRI) was investigated in this research. Single pellets reduction experiments were conducted isothermally using pure CO and H2 as reducing agent in the temperature range 700 °C to 1100 °C. Reduction by H2 was significantly faster than reduction by CO for both pellets and reduction rate increased with increasing the temperature. When CO was used as the reducing agent, the BF pellet achieved a reduction degree of 32% at 700 °C and 67% at 800 °C, while the DRI pellet reached 28% and 59% at the same temperatures. This difference is due to the lower magnetite content in BF pellets (1.93%) compared to DRI pellets (9.11%). However, at 1000 °C and 1100 °C, the DRI pellet achieved 93% and 100% reduction, and the BF pellet 88% and 94%, respectively, due to the higher porosity in the DRI pellet (38%) compared to BF (32%). Kinetics controlling model for hydrogen reduction of both pellets suggested as D2 (2D Diffusion through the solid ash), however, A1 (1D Nucleation and growth) and R3 (3D Chemical reaction) were found as the most compatible models for CO reduction of DRI and BF pellets, respectively. Graphical Abstract

Toxicity of a management bait for grass carp (Ctenopharyngodon idella) incorporated with Antimycin A.

No current technology can specifically target grass carp (Ctenopharyngodon idella) for control within aquatic ecosystems. Rotenone and Carbon Dioxide-Carp are currently the only available registered pesticides for grass carp; they are nonselective and typically applied throughout the water, equally exposing target and native species. A more selective control tool or pesticide application could be used by resource managers to support mitigation efforts. Development of delivery systems that exploit carp feeding strategies could increase selectivity of pesticides and minimize effects on native fishes. A pesticide with selective delivery could be less labor intensive and used within an integrative pest management strategy. The present study examined Antimycin A toxicity in juvenile and sub-adult grass carp and rainbow trout (Oncorhynchus mykiss) across two routes of exposure. Water-based toxicity studies were used to calculate the concentration to cause lethality in 50% of treated fish (LC50) at 24-h, while oral gavage toxicity studies were used to calculate the dose to cause lethality in 50% of treated grass carp and rainbow trout (LD50) 24- to 96-h. Although rainbow trout were more sensitive than grass carp to Antimycin A through water-based exposure, oral toxicity was similar between species, even with inherent gastrointestinal morphological differences. Successful delivery of a lethal dose of Antimycin A to grass carp was achieved through an oral route of exposure using the rapeseed bait and shows promise for registration as a control tool and eventual use in pest management plans. Although a lethal dose of Antimycin A could be incorporated into a single bait pellet, more bait was required to achieve desired mortality when fed to fish under laboratory conditions.

Effect of the ash melting on heat and mass characteristics and reaction rate during corn stalk pellet gasification

In order to investigate the effect of ash melting on the gasification process of biomass pellet, a high-temperature visual gasification system was set up, meanwhile, a biomass melting gasification model for a single pellet was built. Considering that the fusion temperature range of ash is from 1418 K to 1558 K, 1396 K (below 1418 K), 1491 K (between 1418 K and 1558 K), 1591 K and 1677 K (above 1558 K) were chosen as the experimental temperatures. Results show that ash melting could absorb heat, thereby resisting the heat transfer inside pellet. When the gasification temperature is higher than 1558 K, as the larger spherical particles caused by ash melting and coalescing peels off from the pellet surface, the pellet covered by melting ash could be directly exposed to the environment, which is conducive to the heat and mass transfer.

Hematopoietic Endothelial Progenitor cells enhance motor function and cortical motor map integrity following cerebral ischemia.

Hematopoietic stem cells (HSC) are recruited to ischemic areas in the brain and contribute to improved functional outcome in animals. However, little is known regarding the mechanisms of improvement following HSC administration post cerebral ischemia. To better understand how HSC effect post-stroke improvement, we examined the effect of HSC in ameliorating motor impairment and cortical dysfunction following cerebral ischemia. Baseline motor performance of male adult rats was established on validated motor tests. Animals were assigned to one of three experimental cohorts: control, stroke, stroke + HSC. One, three and five weeks following a unilateral stroke all animals were tested on motor skills after which intracortical microstimulation was used to derive maps of forelimb movement representations within the motor cortex ipsilateral to the ischemic injury. Stroke + HSC animals significantly outperformed stroke animals on single pellet reaching at weeks 3 and 5 (28±3% and 33±3% versus 11±4% and 17±3%, respectively, p < 0.05 at both time points). Control animals scored 44±1% and 47±1%, respectively. Sunflower seed opening task was significantly improved in the stroke + HSC cohort versus the stroke cohort at week five-post stroke (79±4 and 48±5, respectively, p < 0.05). Furthermore, Stroke + HSC animals had significantly larger forelimb motor maps than animals in the stroke cohort. Overall infarct size did not significantly differ between the two stroked cohorts. These data suggest that post stroke treatment of HSC enhances the functional integrity of residual cortical tissue, which in turn supports improved behavioral outcome, despite no observed reduction in infarct size.

Particle-resolved computational modeling of hydrogen-based direct reduction of iron ore pellets in a fixed bed. Part I: Methodology and validation

In the pursuit of more sustainable steelmaking, stakeholders are engaging in a transformative exploration of hydrogen-based direct reduction as an alternative to conventional blast furnaces. As a bridging step between single iron ore pellets and industrial shaft furnaces, direct reduction modeling in a fixed bed configuration can play a central role for subsequent process optimization. However, this task involves numerous challenging steps: generation of a realistic packed bed structure along with a good quality mesh and, foremost, reliable transport and kinetic processes for the individual pellets. Therefore, the present work formulates a sound methodology to progress from single particle considerations to 3D-CFD simulations of iron ore reduction using hydrogen in fixed beds, further supported by validations regarding the bed structure and the overall reduction against experimental data from the literature of a 500 g iron ore bed. The current results offer new insights into the direct reduction process, revealing, for instance, the non-uniform reduction of pellets within the bed, the presence of gas pockets, or the importance of the temperature deviation due to the endothermic reduction of iron oxides with hydrogen.

Effects of biomass feedstock and applied pressure on the binding mechanism and pellet qualities

To expand the sources of feedstocks for pelleting and enhance the applicability of the pelleting device, 7 types of feedstocks with representative chemical component contents from different resources were densified. The pressure-time (P-T) curves and energy consumption were used to analyze the densification process and binding mechanism. Specific energy density and densification effects were evaluated pellet qualities and classified feedstock types. Results showed that the densification process was first affected by the feedstock types and then applied pressure. Biomass chemical component contents significantly influence the densification process, the required time, and the final pellet length. Energy consumption in the compression stage is much more than in the extrusion stage. The exponential stage consumes more than 90 % of the total energy. Energy conversion efficiency varies from 62.19 % to 95.06 % with the feedstock types and applied pressures. Single pellet density, densification effects, and specific energy densities increased with the rising applied pressure. BB, SD, PN, CS, and SB can be used as primary feedstocks. SR and ROC act as secondary feedstocks or lubricants. Cellulose, hemicellulose, and lignin of plant cell walls are solid bridges. Extractives, fat, and protein in the plant cells are binders and lubricants to make the pellet surface smooth. This paper could provide further insight into various biomass feedstock densification and general design for pelleting devices.

Parametric studies on energy utilization of the Chinese medicine residues: Preparation and properties of densified pellet

The depletion of fossil fuels has fueled an increased interest in biomass resources usage for heat and electricity generation. As an important biomass resource, Chinese medicine residues have great potential in substituting fossil fuels. However, that is basically limited by its poor properties, including low bulk density, high moisture content, and inhomogeneous structure. Herein, a safe and sustainable strategy was reported to prepare a high-quality densified pellet derived from Chinese medicine residues to address these worries. In this process, mixed and simple size materials were densified under various moisture content and pressure using a laboratory electronic tablet press machine equipped a single pellet mold. Results showed that higher pressure, ideal moisture content (∼6.5 %), and mixed particle size could densify better quality pellets. These findings pave the way for the safely and efficient resource utilization of Chinese medicine residues, as well as providing theoretical guidance and technical support for the household heating.

Relating alkali release from a wood pellet with combustion progress: A modified random pore model supportive study

This paper concerns a miniature gasifier fed with a constant ambient-pressure flow of air to study the pyrolysis and subsequent combustion stage of a single wood pellet at T = 800 ℃. The alkali release and the concentration of simple gases were recorded simultaneously using an improved alkali surface ionisation detector and a mass spectrometer in time steps of 1 s and 1.2 s, respectively. It showed alkali release during both stages. During combustion, the MS data showed almost complete oxidation of the charred pellet to CO2. The derived alkali release, “O2 consumed”, and “CO2 produced” conversion rates all indicated very similar temporal growth and coalescence features with respect to the varying char pore surface area underlying the original random pore model of Bhatia and Perlmutter. But, also large, rapid signal accelerations near the end and marked peak-tails with O2 and CO2 after that, but not with the alkali release data. The latter features appear indicative of alkali–deprived char attributable to the preceding pyrolysis with flowing air. Except for the peak-tails, all other features were reproduced well with the modified model equations of Struis et al. and the parameter values resembled closely those reported for fir charcoal gasified with CO2 at T = 800 ℃.

Multi-scale thermal degradation of wood pellets under low heating rates: Experiments and modeling

Pyrolysis and combustion experiments were carried out on a single wood pellet in a drop tube furnace, under a heating rate of 5 °C/min. Kinetic modeling was done using the Extended Independent Parallel Reaction model. Three reactions were considered in the pyrolysis case and only one in the combustion case. In the pyrolysis case, a thermal model was proposed which is coupled with the kinetic model to correct the temperature inside the pellet. In the combustion case, the mass rate curve was compared to that of the main gaseous emissions. The mass and mass rate curves between the combustions of a pellet in the drop tube furnace and of pellet sawdust in a thermobalance under the same heating rate were compared.

Effect of SiO2 content in magnesia flux pellets on softening-melting and dripping behavior of comprehensive burden structure

High-proportion pellet smelting is the current development direction of blast furnace burden structures in China. And that is an inevitable trend for the future steel industry to achieve pollution reduction and carbon reduction. This study focuses on the mixed burden of magnesia flux pellets with different SiO2 contents, sinter, and lump ore. The influence of SiO2 content on the softening-melting behavior of comprehensive burden and the high-temperature interaction between magnesia flux pellets and sinter were studied through droplet experiments and visual experiments. The results show that with increasing SiO2 content, the T10 of magnesia flux pellets gradually decreases, while the T10 of the comprehensive burden shows no significant change. The TS of both shows a gradually decreasing trend with increasing SiO2 content. However, due to the good matching of the melting range between sinter and magnesia flux pellets in the comprehensive burden, the trend of TS change in the comprehensive burden is relatively slow. The air permeability of the comprehensive burden has significantly improved compared with the single magnesia flux pellets; The interaction between magnesia flux pellets and sinter occurs through the liquid phase. The fayalite phase in the pellets reacts with the main high melting point substance Ca2SiO4 in the sinter to generate a new low melting point kirschsteinite. With the increase of SiO2 content, the content of kirschsteinite in the comprehensive burden increases. That is also the reason for the decrease in TS of the high silicon comprehensive burden; With the increase of SiO2 content, the maximum pressure difference and characteristic values of magnesia flux pellets and comprehensive burden gradually increase. When the SiO2 content exceeds 6%, the maximum pressure difference and characteristic value of a single pellet sharply increase, while the trend of the maximum pressure difference and characteristic value change of comprehensive burden is relatively gentle. Its characteristic values are below 980 kPa·°C. At this time, the air permeability of the comprehensive burden is significantly improved compared to the single magnesia flux pellets. In the case of SiO2 content exceeding 6%, the addition of a sinter can effectively address the soft melting performance of high-silica magnesia flux pellets and enhance column air permeability. In addition, the high drop temperature of the high-silica comprehensive burden is due to the presence of a large amount of MgO in the magnesia wustite during the later stage of reduction, which increases the melting point. And the MgO content in the slag is relatively low. That causes a sharp increase in slag viscosity and makes it difficult to separate the slag from iron.

Flue gas desulfurization by natural recyclable manganese ore in packed bed reactor and its performance prediction by random pore model

Various grades of manganese dioxide ores, as a natural recyclable sorbent, can be used in dry flue gas desulfurization (FGD) at moderate temperatures (350–450 °C). This research provided low- and high-grade manganese dioxide ores to examine SO2 removal in a packed bed reactor. To obtain characteristic parameters of mineral sorbents, XRD, XRF, BET, and mercury porosimetry were employed. Then, kinetic parameters of desulfurization reaction were determined using thermogravimeter analyzer (TGA) and random pore model (RPM) for a single pellet. In desulfurization experiments of simulated flue gas in a packed bed reactor and mass spectrometer (MS) apparatus, the breakthrough times were measured under various operating conditions. The onset of these breakthrough times or life-time of MnO2 reactor for the SO2 removal was predicted successfully by RPM for a packed bed reactor using related kinetic constants from TGA. In addition, reacted sorbets were recycled multiple times after washing with water. Not only does this simple method separate MnSO4 from unreacted sorbents as a valuable byproduct to reduce the FGD cost, but it also improves pore size distribution (PSD) of mineral MnO2 by creating large pores. Modified PSD of this recycled sorbent caused increased breakthrough time.

Transmittance estimation of translucent polymeric pellets

AbstractPlastics are commonly produced and sold in pellet form due to their superior handling characteristics. However, due to their small size, it is often impractical, if not unfeasible, to determine the transmittance of a single pellet instrumentally. Moreover, such measurements may be highly variable. Therefore, translucent films of certain thickness, known as plaques, are commonly molded to enable instrumental determination of their transmittance. These plaques, however, are not needed beyond the quality control process while they add a costly step to the production process. In this study, we test a method, based on the layer theory, that enables the estimation of the transmittance spectra of nearly transparent plastic plaques from the reflectance measurements of their pellet counterparts. The comparison of the estimated transmittance spectra of pellets versus measured transmittance of plaques shows the RMSE ranging from 0.37%–1.80%, with a color difference, CIEDE2000(1:1:1), of 0.07–0.48, thus validating the applicability of the method.

Cholecystokinin facilitates motor skill learning by modulating neuroplasticity in the motor cortex.

Cholecystokinin (CCK) is an essential modulator for neuroplasticity in sensory and emotional domains. Here, we investigated the role of CCK in motor learning using a single pellet reaching task in mice. Mice with a knockout of Cck gene (Cck-/-) or blockade of CCK-B receptor (CCKBR) showed defective motor learning ability; the success rate of retrieving reward remained at the baseline level compared to the wildtype mice with significantly increased success rate. We observed no long-term potentiation upon high-frequency stimulation in the motor cortex of Cck-/- mice, indicating a possible association between motor learning deficiency and neuroplasticity in the motor cortex. In vivo calcium imaging demonstrated that the deficiency of CCK signaling disrupted the refinement of population neuronal activity in the motor cortex during motor skill training. Anatomical tracing revealed direct projections from CCK-expressing neurons in the rhinal cortex to the motor cortex. Inactivation of the CCK neurons in the rhinal cortex that project to the motor cortex bilaterally using chemogenetic methods significantly suppressed motor learning, and intraperitoneal application of CCK4, a tetrapeptide CCK agonist, rescued the motor learning deficits of Cck-/- mice. In summary, our results suggest that CCK, which could be provided from the rhinal cortex, may surpport motor skill learning by modulating neuroplasticity in the motor cortex.

Multi-pellet injection into the NBI-heated phase of TJ-II plasmas

A pellet-induced enhanced confinement (PiEC) phase, with general characteristics similar to those reported for the stellarator W7-X, is observed after single pellet injection (>1019 H atoms) into the neutral beam injection heated phase of plasmas in the mid-sized heliac-type stellarator TJ-II. In addition to a step-like increase in density, plasma diamagnetic energy content rises significantly with respect to that of reference discharges, energy confinement time is similarly enhanced when compared to International Stellarator Scaling law predictions (Yamada et al 2005 Nucl. Fusion 45 1684) renormalized for TJ-II, and the triple product, n e · T i · τ E, exhibits a clear bifurcation towards an improved confinement branch when compared to the branch product predicted by the same law. In this work, multiple pellets are injected in series into NBI-heated plasmas in the TJ-II and post-injection plasma performance is reported and discussed. For instance, a charge-exchange recombination spectroscopy diagnostic reveals significantly increased core ion temperatures after pellet injection compared to temperatures achieved in comparable reference plasmas, this pointing to increased ion energy content and improved ion energy confinement during a PiEC phase. It is also found that enhanced performance is independent of whether co- or counter-NBI heating beam is employed. Finally, record stored diamagnetic energy content and plasma beta values are achieved when the largest available pellets are employed. The results indicate that pellet injections extend the operational regime well beyond limits previously achieved in TJ-II without pellets.

Generalized Linear Driving Force Formulas for Diffusion and Reaction in Porous Catalysts

Approximate models are a fast and most often precise tool for determining the effectiveness factor for heterogeneous catalysis processes that are realized in the real world. They are also frequently applied as robust transient models describing the work of a single catalyst pellet or as a part of a more complex model, for example, a reactor model, where mass balances for the gas phase and solid phase are necessary. So far, approximate models for diffusion and reaction processes have been presented for processes described by a single balance equation. In the present work, approximate models without the mentioned limitation are presented and discussed. In addition, simple rules are shown for the development of other complex approximate models without tedious derivation in the complex domain. The formulas considered in this work are typical long-time approximations of the transient process. The accuracy is good, especially in the range of small and intermediate Thiele modulus values.

Long-Term Alterations in Motor Skills, Neurogenesis and Astrocyte Numbers following Transient Cerebral Ischemia in Mice.

Background and Objectives. Neurogenesis is an integral process in post-stroke recovery, involving the recruitment of proliferating neuroblasts from neurogenic niches of the mammal brain. However, the role of neurogenesis in the long-term restoration following ischemic stroke is fragmented. Post-stroke motor dysfunction includes challenges in the proper, coordinated use of hands and is present in roughly two-thirds of human patients. In this study, we investigated chronic behavioral and biochemical alterations after transient cerebral ischemia in adult male mice. Materials and Methods: Twelve-week-old C57BL/6N male mice were used, and fMCAo lasting 60 min was induced. At multiple timepoints after fMCAo induction, a single pellet reaching task was performed. Six months after the procedure, we immunohistochemically determined the number of proliferating neuroblasts (BrdU and DCX-positive) and the number of differentiated astrocytes (GFAP-positive) in both brain hemispheres. Results: The reaching ability of fMCAo mice was impaired from one month to six months after the induction of ischemia. Neuroblast proliferation was increased in the ipsilateral SVZ, whereas GFAP+ cell count was elevated in the hippocampal DG of both hemispheres of the fMCAo group mice. Conclusions: Our current report demonstrates the long-term effects of transient cerebral ischemia on mice functional parameters and neurogenesis progression. Our data demonstrate that transient cerebral ischemia promotes a long-lasting regenerative response in the ipsilateral brain hemisphere, specifically in the neurogenic SVZ and DG regions.

Study on heat transport analysis and improvement method in a single CaCO3 pellet for thermochemical energy storage

CaCO3/CaO thermochemical energy storage (TCES) pellets have significant advantages in bulk energy storage density, transport, and utilization. However, severe heat transport limitations within the milli-sized CaCO3 significantly affect the TCES efficiency and economy. Currently, investigations on the effect of initial porosity, bulk gas flow velocity, and reaction rate on heat transport and methods of enhancing the heat transport inside the pellet are lacking. In this paper, we developed a mathematical model coupling calcination reaction, mass transfer, and heat transfer to reveal the effects of pellet parameters and operating conditions on heat transport and reaction conversion rate within a CaCO3 pellet. The results show that the size of the CaCO3 pellet, bulk gas temperature, and reaction rate generate the most pronounced impacts on heat transport in a single CaCO3 particle during the TCES process. Furthermore, the heat transport inside the CaCO3 pellet can be improved by appropriately increasing the bulk gas flow velocity. Finally, this paper first numerically investigates the addition of SiC as a thermal conductivity enhancer to improve the heat transport performance inside a CaCO3 pellet. This study can guide the design of high-performance CaCO3 composite pellets and inform the selection of operating conditions for subsequent reactor applications.

Fecal genotyping to estimate small mammal population size, with a comparison to live mark-recapture estimates

Live capture-recapture is often considered the gold standard for estimating wildlife population size or density, but the approach can be limited by permitting requirements, required labor, welfare concerns, and biased estimates resulting from heterogeneity in individual behavior. Noninvasive genetic sampling (e.g., from fecal pellets) offers a powerful alternative approach, but this method’s success varies among taxa, with little research available on its use in rodents. Here, we addressed a series of questions to develop a noninvasive genetic sampling approach for the endangered giant kangaroo rat (Dipodomys ingens): (1) how quickly does DNA degrade in natural conditions, (2) how many pellets are required to recover a genotype, (3) how often do multiple individuals contaminate a pooled sample from a single sampling location, and (4) how do variable and parameter estimates from noninvasive genetic sampling compare to live-trapping mark-recapture estimates? We found that fecal pellets were successfully genotyped up to 9 days (estimated probability of recovery = 0.78) after exposure to hot, arid conditions, but that rate fell precipitously soon after. Although giant kangaroo rats are territorial, multiple individuals deposited fecal pellets at the same sampling locations; however, single pellets contained sufficient DNA to recover genotypes and to identify individuals, so contamination was not a problem for this approach. Capture probabilities were lower using noninvasive genetic sampling ( = 0.26, SE = 0.01) than live trapping ( = 0.40, SE = 0.06). Population estimates were generally similar using noninvasive genetic sampling, although they were quite a bit higher ( = 64 , = 38) on one grid. Noninvasive genetic sampling can overcome many of the limitations of live-trapping for small mammals, but the approach should be tested in additional taxa and systems to provide more generalizable recommendations for sampling schemes.

Low-Dose LPS Modulates Microglia/Macrophages Phenotypic Transformation to Amplify Rehabilitation Effects in Chronic Spinal Cord Injured (CSCI) Mice.

Spinal cord injury (SCI) results in stalled motor function recovery under the chronic phase. One of the reasons due to the presence of ongoing inflammation. Therefore, regulating the status of immune cells may help reopen the window for neural repair, which represents a potential therapeutic target. In this study, we aimed to investigate whether this could be achieved in mice with cervical 5 crush CSCI (4W) by utilizing a concentration of 0.5mg/kg of lipopolysaccharide (LPS) to stimulate microglia/macrophages. Additionally, the mice underwent rehabilitation training for another 6 weeks. Our results showed that systemic injection of LPS enhanced the effects of forelimb rehabilitation training, as evaluated through single pellet grasping (SPG). Electrophysiological studies revealed the restoration of cortical drive to the injured side's forelimb muscles in the training combined with LPS group. Tract tracing studies demonstrated the reconstruction of cortical innervation to the cervical spinal cord. Furthermore, the levels of pro-inflammatory phenotype markers, such as inducible nitric oxide synthase (INOS) and CD68, decreased, while the expression of anti-inflammatory phenotype markers, including arginase 1 (ARG-1) and CD206, increased. Importantly, this phenotypic switch in microglia/macrophages was accompanied by an increase in phagocytic activity markers as indicated by BODIPY + IBA1 + staining. Collectively, our data suggests that low-dose LPS improves the effects of rehabilitation training by regulating the phenotypic transformation of microglia/macrophages in CSCI.This study provides a fresh perspective and intervention direction for the clinical treatment of chronic spinal cord injuries.

Direct Reduction of Iron Ore Pellets by Using CO/CO2 and CO Gases

Gas‐based direct reduction in a shaft furnace is the dominant process in the world for production of direct reduced iron. As fresh reducing gas passes through the iron ore burden, it is diluted by the gas emitted from the reacted iron ores which decreases the reduction potential of the reducing gas. Previous reduction experiments mostly used single pellet which could not examine this phenomenon. In this study, hematite pellets arranged in multiple layers inside a molybdenum basket are reduced isothermally at 1173–1273 K using 50% CO + 50% CO2% and 100% CO gases under flow rates of 0.2–5.0 NL min−1 to simulate the dilution of CO by CO2 in the shaft. It is discovered that the reduction of pellets in the basket is highly uneven even in pure CO atmosphere. Pellets in the middle layer are reduced ≈2 times less than the pellets in the top and bottom layers. The top side of a pellet is also less reduced than the bottom side facing the gas inlet. During melting of incompletely reduced pellets at 1873 K, intensive interaction between the unreduced iron oxides and the alumina crucible was observed. Thus, smelting of incompletely reduced iron could potentially shorten the refractory lifetime.