Flowability Behavior Research Articles

Formulation of weaning food from yellow maize (Zea mays L.) and red millet (Eleusine coracana L.), enriched with pretreated African locust beans (Parkia biglobosa Jacq.) flour

This work aimed to formulate adequate weaning food with acceptable protein and mineral contents from yellow maize and red millet enriched with pretreated Parkia biglobosa (PB). PB seeds were boiled to facilitate dehulling. The dehulled seeds were divided into different portions, which were respectively fermented (3 and 6 days), oven roasted (175 °C for 20 and 40 min), and microwaved (450 W for 15 and 30 min). Maize and millet flours used as control samples, were respectively mixed (1:1 w/w) with pretreated PB seed flours, to constitute fourteen formulations. These formulations were analyzed for their proximate, mineral compositions, physical and functional properties, total phenolic content and antioxidant activity. There was significant increase in protein, carbohydrate and lipid contents for formulations made with PB roasted in oven (175 °C, 40 min) and in microwave (450 W, 30 min). Protein content of all formulated infant flours was above 15 g/100 g DW recommended value for infant complementary foods. The highest energy value (485.09 kcal) was obtained with the formula maize and P. biglobosa oven roasted at 175 °C for 40 min. The formulated flours have the required values of K, P, Ca, Mg and Na as recommended by the WHO. Formulations made with pre-fermented PB exhibited the highest swelling capacity (173.43%), water holding capacity (230.85 %), total phenolic content (48.32 mg GAE/g) and antioxidant activity (95.78%). Their least gelation concentration values decreased compared to the sample added with untreated PB. With a maximum value of 10.25, titratable acidity increased with roasting time while the pH value decreased. Porosity decreased with processing time. The value of the Hausner ratio (HR < 1.4) revealed that the formulated flours have good flowability behavior. Based on the obtained result, pretreated dehulled PB seeds could be recommended in the enrichment of complementary food made from maize and millet.

Multiple-Instance Regression for Metal Powder Hall Flow Rate Prediction Using Augmented Particle Size and Shape Data

This study investigates the relationship between metallic powders and their flowability behavior (captured in terms of Hall flow rates using Hall flowmeters). Due to the many trait dependencies of powder flowability, which have made the formulation of a physical and mechanistic generalizable model difficult to resolve, this study seeks to develop an alternative data-driven framework based on powder size and shape characteristics for Hall-flow-rate predictions. A multiple-instance regression framework was both developed for processing multiple-instance powder data and compared with standard machine learning models. Data augmentation was found to improve the overall performance of the framework, although the limited dataset was a constraint. Still, the study contributes to ongoing efforts to identify traditional, associative, and generalizable patterns between powder properties and resultant flowability behaviors. The findings show promise for real-world applications with a larger dataset, such that this initial application of multiple instance regression frameworks for metal powder Hall-flow-rate predictions as a function of powder particle size and shape data can be scrutinized in full.

Multi-parametric flowability classification of self-compacting concrete containing sustainable raw materials: An approach to real applications

Adding sustainable raw materials to Self-Compacting Concrete (SCC) modifies its flowability behavior. Furthermore, the use of these raw materials may at the same time even improve one fresh property while worsening another. An accurate flowability description of SCC containing sustainable raw materials therefore requires a multi-parametric classification that simultaneously covers all fresh properties (slump flow, viscosity, and blocking ratio) for an accurate description of its potential applications. Existing classifications consider each fresh property independently. In this paper, a multi-parametric flowability classification of SCC containing sustainable raw materials is proposed. The effects of multiple sustainable raw materials on SCC flowability are compiled in a dataset serving as a knowledge base with information on 663 SCC mixes containing sustainable aggregates and binders. The statistical analysis of the dataset led to the definition of three types of flowability zones. Firstly, the overall-flowability zones, in which SCC flowability is described in absolute terms: the better the in-fresh properties, the better the overall-flowability zone. Secondly, the flowability-balance zones reflect the balance between free flow (slump flow and slump-flow viscosity) and flow around obstacles (V-funnel emptying time and L-box blocking ratio). Finally, SCC is classified within flowability-predominance zones, which define the main characteristic of SCC flowability, rate of flow (viscosity) or uniformity of flow (spreading). The variability of the effect of each sustainable raw material on the flowability of SCC makes this classification useful, in so far as it offers a complete picture of the fresh behavior of SCC in which all fresh properties are simultaneously considered. Furthermore, based on the description in the proposed classification of overall flowability and the balance between free flow and flow around obstacles, the application fields are defined for which the use of each SCC mix with sustainable raw materials is recommended.

Effect of different roasting methods on the proximate by composition, flow properties, amino acid compositions, colour, texture, and sensory profile of the chickpeas

SummaryRoasting is a common process for chickpeas to improve their texture, palatability, appearance, shelf‐life, physical, and functional properties. This study aimed to determine the effect of different roasting methods (conventional, microwave, and microwave + conventional) on the proximate and amino acid compositions, powder properties, texture, and sensorial properties of the chickpeas. For this purpose three different roasting times (3, 5, and 7 min), microwave powers (100, 300, and 600 W), and microwave roasting + conventional roasting treatment (100 W + 250 °C, 300 W + 250 °C, and 600 W + 250 °C) were applied to raw chickpea samples. The moisture content and water activity values of roasted chickpeas were found to be lower than 7% (w.b.) and 0.50, respectively. The lower ash and protein contents, hygroscopicity value, wettability time and higher fat content and L* value were observed for control compared to roasted samples. The flowability behaviour of the samples was found at a fair level. Roasting methods significantly affected the amount of amino acids in chickpeas but do not reduce the nutritional quality of their proteins. The hardness value of chickpea samples from the suture and cheek angle was decreased parallel to the increase in the roasting temperature and time. The highest sensory scores in terms of general appeal were obtained from the combined group (300 W–250 °C) for 3 min.

Flow behaviour of zeolite powders at high process temperatures

Zeolite powders are an active ingredient for various applications and processing condition could affect powder flow behaviour. One of the important process conditions that changes during the manufacturing process is temperature. Temperature can change the particle properties affecting the powder flow properties and, therefore, the latter need to be tested at the process conditions. The flow properties of two types of zeolite powders, Z302 and T804, were evaluated at temperatures of 150, 300, and 500 °C in the range of 1–8 KPa of normal consolidation stresses by an Anton Paar shear cell. The two materials show a very different flowability behaviour, even at the lowest temperature tested. The temperature appears much more significant effect on the T804 zeolite at 500 °C and the flow function falls into the cohesive range while the Z302 zeolite flow function changes only for large values of consolidation stresses, by showing a flow function falling entirely within the very cohesive range. To find an explanation for understanding such a different behaviour of these two materials at changing temperature and consolidation stress, a theoretical framework was developed to take into account the different particle size distributions of the two powders. The resulting analysis, which is specific to the system taken into account, supports the goodness of the general approach that an adequate estimate of the average material fabric provides averaged estimates of contact forces that are able to explain the different behaviours of temperature and consolidation changes shown by powders. An original analysis of flowability based on the calculation of a structural length is also introduced to account for different powder bulk densities. • The higher temperatures decrease the flowability of Zeolite powders. • A theoretical framework was developed for the effect of particle size distribution. • A characteristic structural length was calculated on the changing density.

Flowability of spray‐dried sapodilla pulp powder

AbstractThis study aimed to evaluate the influence of maltodextrin, Arabic gum, and dextrin on phenolic compounds, morphology, and flowability of sapodilla pulp powder obtained in a spray dryer. Sapodilla pulp was characterized by its moisture and total polyphenols. The carriers were individually added to the pulp at a concentration of 20% (m/m), and the samples were dried in a spray dryer. The powders were analyzed for moisture, hygroscopicity, total polyphenols, and particle morphology, and their flowability was evaluated using the Powder Flow Tester (PFT). Total polyphenols of sapodilla pulp (average of 1055.30 mg GAE in 100 g of pulp solids) were more significant than in the powders (457.06 to 635.55 mg GAE in 100 g of pulp solids). The lowest moisture (1.16%) was obtained for maltodextrin. All carriers generated nonhygroscopic powders. The particles showed a rounded shape with greater roughness in samples containing Arabic gum. The powder with dextrin resulted in better flowability characteristics, with a higher flow index and lower compressibility index, Hausner ratio, and wall friction angle. Sapodilla pulp powder was classified as cohesive, with flow indices &lt; 3, compressibility index from 53.2 to 59.9, and Hausner ratio between 2.14 and 2.50. The carriers used influenced the characteristics of sapodilla pulp powders, the Arabic gum promoting greater protection of total polyphenols and dextrin resulting in better flowability characteristics.Practical ApplicationsThe consumption of tropical fruits has increased in recent years, especially fruits considered exotic. The sapodilla fruit has many health benefits potential, but it has a short shelf life and seasonal crop. This research provides information on the spray‐dried sapodilla pulp powder containing different drying carriers, in order to evaluate the powder flowability behavior. This evaluation was based on particle morphology, wall friction angle, and bulk and tapped densities. It is important to determine the influence of carriers on the powder in order to produce a good quality product.

Multiscale Approaches Including ANN and M5P-Tree with SI and OBJ Assessment Tools to Predict the Shear Thinning of Bentonite Drilling Muds Modified with Clay Nanosize at Various Elevated Temperatures

Improving the flowability behavior of the water-based drilling mud (WBM) using bentonite under high-temperature conditions is significant in the drilling borehole operations. In this study, the influence of bentonite and clay nanoparticle (CNP) contents on the non-Newtonian fluid (rheology) properties such as initial shear stress and fluid’s resistance to flow (viscosity) under high-temperature conditions were tested and quantified. The shear stress and shear strain rate relationships of WBM were simulated using two new rheological models of the vapor pressure and modified Hoerl models, and the modeling outcomes were validated with the Herschel–Bulkley (HB) model. This study also analyzed and formulated more than 268 data sets, including observational data and data obtained from previously published studies ranging with bentonite in the drilling muds from 2% to 8% (%wt. of water), 0% to 1% of CNP (%wt. of bentonite), and heating temperatures were ranging from 25°C to 100°C. The HB rheological model predicted initial shear stress better than the other two rheological models depending on several statistical assessments. The initial shear stress of drilling muds can be predicted well based on bentonite, CNP contents, and temperature using various simulation techniques. According to several statistical tests, the nonlinear regression and artificial neural network (ANN) performed stronger than other model techniques to predict the yield stress of WBM as a function of bentonite, CNP contents, and temperature.

Physical-chemical properties and microstructural characterization of traditional mexican chili (Capsicum annuum L.) powders

Objective: Evaluate the physical-chemical properties and characterize the microstructure of four varieties of traditional Mexican chili (Capsicum annuum L.) powders: “Arbol”, “Guajillo”, “Piquin” and “Mole ranchero” (Ancho chili).&#x0D; Design/methodology/approach: Physical-chemical properties of chili powders were evaluated by means of moisture content, particle size, aerated and tapped bulk density, Carr index, Hausner ratio, angle of repose (flow properties), capsaicin, and carotenoids content. Microstructure of samples was characterized by Confocal Laser Scanning Microscopy and Scanning Electron Microscopy. ANOVA analysis and Tukey test were performed to evaluate the significant statistical difference between samples at 95% of confidence level.&#x0D; Results: “Arbol”, “Guajillo”, “Piquin” and “Mole Ranchero” chili powders presented a cohesive behavior respect to its flow properties related to aerated and tapped bulk density, angle of repose, Carr Index, and Hausner ratio values under moisture content between 6.59-14.48 gH2O/100g d.s. “Arbol” and “Piquin” chili powders presented the higher capsaicin content, while “Guajillo” and “Mole ranchero” showed the higher carotenoids content. FTIR spectra confirmed the presence of secondary amide, phenolic groups, alkanes, and aliphatic chains that belong to capsaicin structure at specific absorption bands. Microstructure of chili powders presented particles with surface imperfections as cracks and dents, and smooth surface that influence physical-chemical and flowability properties.&#x0D; Limitations on study/implications: Hight moisture content affect the physical-chemical properties, flowability and microstructure of traditional Mexican chili powders.&#x0D; Findings/conclusions: Moisture content between 6.59 and 14.48 gH2O/100g d.s. influences the physical-chemical properties, flowability and microstructure of traditional Mexican chili powders. To improve physical-chemical properties and flowability behavior of chili powders is required that moisture content be lower than 6.59 H2O/100g d.s.

Impacts of Ethanol Production and Drying Conditions on the Chemical, Physical, and Flowability Properties of Distillers Dried Grains With Solubles.

The production of corn-based ethanol in the U.S. has dramatically increasied in recent years, and consequently so has the quantity of coproduct feed ingredients generated from this segment of the grain processing industry. These streams are almost exclusively utilized as livestock feed, which partially offsets the need for corn in feed rations, but other value-added applications do exist. Because of its use as an animal feed, considerable research has been conducted into the nutritional properties, but to a lesser extent the physical and flowability properties of commercially-produced distillers dried grains with solubles (DDGS). There can be occasions when the quality of coproducts is not consistent. Thus questions regarding the influence of processing operations on the resulting coproduct characteristics must be examined. The objective of this research was to conduct extensive physical and flowability property analyses on DDGS samples which were produced under varying conditions in a pilot plant-scale ethanol plant, in order to investigate the effects of various manufacturing operations (specifically ethanol production and drying conditions) on the resulting properties of the DDGS. Using various laboratory methods, a variety of properties, including bulk density and angle of repose, were determined. DDGS fat content was highly correlated with aerated and packed bulk densities, which indicates that fat level plays a key role in flowability behavior. Future studies should examine this potential relationship in more depth, especially as the industry has moved to fat reduction via oil separation processes.

Evaluation of the drying methods influences on the flowability of multi-components formulation

Powder flowability is an important aspect to have effectual and productive manufacturing of pharmaceutical tablets. Therefore, this study compared the flowability behaviour in terms of Carr index (C I ) and Hausner ratio (Hr) of multi-components formulation of naproxen sodium which dried using different drying techniques. A wet formulation of naproxen sodium, microcrystalline cellulose, and polyvinylpyrrolidone was prepared and subjected to microwave drying and three conventional drying techniques - freeze drying, convective drying and vacuum drying. This study revealed that microwave and freeze drying granules were of the highest C I and Hr with possible flowability, while a vacuum and convective drying had the lower C I and Hr with fair flowability. Modelling the correlation between flowability factors and dried samples were presented. The variability in the particle size and the specific surface area of the dried granules showed significant effects on C I and Hr thereby powder flowability. Although the influences of the drying process on the drug powder flowability were indirect, drying method can improve or degrade the textural properties of resultant dried granules such as particle size, specific surface area, moisture content, friability and degree of amorphous/crystallinity and consequently change their flowability.

The antioxidant and physicochemical properties of microencapsulated bioactive compounds in Securigera securidaca (L.) seed extract by co-crystallization

Abstract Securigera securidaca seed is a good source of phenolic compounds with high antioxidant properties. Preservation and maintenance of natural antioxidants have always been a challenge and microencapsulation is a suitable method for this purpose. In this study, the chemical compounds of the plant seed extract were identified by GC/MS device. Bioactive compounds from the seed ethanolic extract were microencapsulated in the sucrose matrix during the co-crystallization process. The evaluations included total phenolic compounds, radical scavenging ability, production efficiency, moisture content, and flowability characteristics of the produced powders, such as compressibility index, Hausner ratio, and angle of repose. The results showed significant differences in the phenolic compounds and the radical scavenging ability between the control sample and the co-crystallized powder (P &amp;lt; 0.05). The production efficiency and the moisture content of extract-containing co-crystallized powder were 84% and 0.14%, respectively. The particle size difference of the microencapsulated powder could significantly affect the powder flowability characteristics (P &amp;lt; 0.05), and particles with a size of 1 mm showed better flowability behaviour. FT-IR charts for samples revealed chemical bonds specific to saccharose molecule indicating no changes in covalent bonds present in saccharose molecule structure after the process. Scanning electron microscope images showed the presence of vacant spaces and porosity in the structure of saccharose crystals formed during the process of crystallization. As a result, the co-crystallized powder obtained from the plant extract can be used as an appropriate antioxidant in the food and pharmaceutical formulations.

Wood pulp as a potential raw material source for manufacturing bio-based building materials

The application of bio-based material such as cellulose fibres derived from renewable source to cement mortars was investigated and the properties of fresh mixtures and hardened mortars were characterized. The mixtures composition consisted of combined addition of the selected kind of cellulose fibres (bleached wood pulp) and superplasticizer (polycarboxylate ester). The aim was to produce a cement mortar with the improved properties for indoor application. The 0.5 wt.% fibre addition (from weight of filler and binder) and superplasticizer dosage of 1% in the mixtures were used. Reference cement mortar did not contain cellulose fibre and superplasticizer. The comparative study of the fresh fibre cement mixture properties has been showed worse flowability behaviour of mixture with plasticizer, as expected. The the beneficial effect of the superplasticizer was not proven even on the compressive and flexural strength of fibre cement mortars after 7, 28 and 90 days of hardening. The performances of the mortars were dependent not only on fibres and superplasticizer nature but also on the organic/inorganic interface.

Physico-chemical and rheological properties of Lebanese kishk powder, a dried fermented milk-cereal mixture

Kishk is a traditional fermented milk-cereal mixture, widely consumed in Lebanon. Twenty Lebanese kishk powder samples were collected from artisanal producers in four Lebanese regions, in order to assess the effect of milk base and cereals on their physicochemical properties, functional and rheological properties. Milk type affected the fat content and color parameters of kishk samples. Multi-scale exploration of kishk microstructure revealed a complex network of macroconstituents (milk protein and wheat starch) embedded in a thick layer of fat. The mechanism of kishk rehydration was then exploited by analyzing the water sorption isotherms and observing the morphometric changes in the particles of this powder subjected to different relative humidities. From powder rheology measurements, kishk showed an intermediate flowability behavior and cohesiveness, associated to its high fat content as a binder between the particles.

Measurement and Comparison of Glass Transition and Sticky Point Temperatures of Distillers Dried Grains with Solubles (DDGS) with Varying Condensed Distillers Solubles (CDS) and Drying Temperature Levels

ABSTRACTDistillers dried grains with solubles (DDGS) is the main coproduct of the U.S. fuel ethanol industry and has significantly impacted the livestock feed markets in recent years. Particle agglomeration and subsequent flowability problems during storage and transport are often a hindrance, a nuisance, and expensive. This paper aims at characterizing the glass transition (Tg) and sticky point (Ts) temperatures of DDGS samples prepared with varying condensed distillers solubles (CDS) levels (10, 15, and 20%, wb), drying temperatures (100, 200, and 300°C), and moisture contents (0, 10, and 20%, db), and it discusses implications on DDGS flowability behavior. Distillers wet grains were combined with specified levels of CDS and dried in a convection‐style laboratory oven to produce DDGS. Subsequently, predetermined amounts of water were added to the DDGS to achieve desired moisture content levels. To determine Tg (°C), a differential scanning calorimeter was used, whereas Ts (°C) was determined through a novel technique with a rheometer. Results indicated high correlations between observed Ts and observed Tg (R2 = 0.87) data for DDGS samples. Also, the empirical model for predicted Tg = f (drying temperature, CDS level, and moisture content) based on the Gordon–Taylor model showed favorable R2 (0.74). Stickiness of DDGS increased with an increase in moisture content, indicating flow problems resulting from moisture. It was found that drying temperatures and CDS levels each had significant effects on Tg and Ts as well.

To study physical compatibility between dibasic calcium phosphate and cohesive actives using powder rheometer and thermal methods

Aim: An attempt is made to provide better understanding of the compatibility aspect of excipients with different properties of active pharmaceutical ingredient (API) using various rheological, thermal and morphological studies conducted on binary mixtures of Dibasic Calcium Phosphate anhydrous (DCP-A) and Dibasic Calcium Phosphate dihydrate (DCP-D) forms with cohesive API’s (Acetaminophen and Aspirin).Method: Binary mixtures of DCP’s were prepared by addition of 0% w/w to 50% w/w of the API in each powder blend. Powder rheological analysis were conducted using FT4 powder rheometer, rotational shear cell and empirical approaches such as angle of repose (AOR), Hausner ratio (HR) and Carr’s index (CI). Thermal analysis was conducted using differential scanning calorimetry (DSC) and thermal effusivity. Morphological studies were conducted using Scanning Electron Microscopy (SEM) to determine the fundamental differences between powder materials.Result/Conclusions: Powder rheometer showed distinctive understanding in the flowability behavior of binary mixtures with addition of increasing proportion of API’s than empirical approaches. Thermal approaches revealed the potential interaction of water of crystallization DCP-D while such interaction was absent in DCP-A. Binary mixtures prepared using DCP-D were better flowable while blends containing DCP-A were better in stability (physical), compressibility and permeability. This study allows the scientist to understand the powder packing of different blends with their flowability and compressibility parameter and helps selection of appropriate form of hydrate for relevant API.

Thermal nanoimprint resist for the fabrication of high-aspect-ratio patterns

Graphical abstractDisplay Omitted Highlights? We present a new thermal NIL resist for high-aspect-ratio patterns via a bilayer approach. ? The resist properties are tailored by free radical polymerization of specific comonomers. ? The resist shows excellent flowability and demoulding characteristics. ? A high oxygen RIE resistance demonstrates the suitability of the resist as a masking layer. We report a newly developed thermal nanoimprint (T-NIL) resist specifically engineered for the implementation in a bilayer system rendering the fabrication of high-aspect-ratio patterns. The synthesis of the T-NIL resist was accomplished by applying a free radical copolymerization of adequate comonomers. Due to the modular architecture of the terpolymer, the rather different material properties are directly adjusted by varying the amount of the comonomers and also by tuning the polymerization conditions like temperature and the amount of initiator. Following this synthetic strategy, the Si content for a sufficient oxygen plasma resistance as well as an excellent flowability behavior for a significant reduction of the overall processing cycle time could be easily achieved. Moreover, the already good mould release properties of the pure T-NIL resist can be further improved by the addition of a small amount of a fluorinated additive leading to a very low defect rate of the imprinted structures.

Effects of CDS and Drying Temperature Levels on the Flowability Behavior of DDGS

Due to increasing demand for alternative fuels and theneed to reduce dependence on fossil fuels, the growth of bioethanol production has been rising. One of the problems facing this industry is transportation of the coproduct dried distillers grains with solubles (DDGS) over long distances, because caking and agglomeration between particles can lead to bulk flow problems. In this study, DDGS was prepared by combining condensed distillers solubles (CDS) and distillers wet grains (DWG) and then oven drying to achieve 8% (db) moisture content. The effects of drying temperature (100, 200, and 300°C) and CDS (10, 15, and 20%wb ) level on the resulting flowability behavior of the DDGS particles were investigated. Statistical analyses indicated significant differences (α = 0.05, 95% confidence level) due to drying temperature and CDS main effects and significant interaction effects between CDS level and drying temperature for many of the flow parameters. Surface regression analysis of the ratio of total flow index/Jenike flow function as a function of CDS and drying temperature resulted in an R 2 value of 0.94. Partial least squares (PLS) regression yielded an R 2 of 0.90 for the Jenike flow function index as a function of all flow and physical properties using only two multivariate components. Understanding the effects of varying drying temperatures and CDS levels can help guide efforts to overcome DDGS flowability problems.

Artificial Neural Network Modeling of Distillers Dried Grains with Solubles (DDGS) Flowability with Varying Process and Storage Parameters

ABSTRACTNeural network (NN) modeling techniques were used to predict flowability behavior of distillers dried grains with solubles (DDGS) prepared with varying levels of condensed distillers solubles (10, 15, and 20%, wb), drying temperatures (100, 200, and 300°C), cooling temperatures (–12, 25, and 35°C), and storage times (0 and 1 month). Response variables were selected based on our previous research results and included aerated bulk density, Hausner ratio, angle of repose, total flowability index, and Jenike flow index. Various NN models were developed using multiple input variables in order to predict single‐response and multiple‐response variables simultaneously. The NN models were compared based on R2, mean square error, and coefficient of variation obtained. In order to achieve results with higher R2 and lower error, the number of neurons in each hidden layer, the step size, the momentum learning rate, and the number of hidden layers were varied. Results indicate that for all the response variables, R2 &gt; 0.83 was obtained from NN modeling. Compared with our previous studies, NN modeling provided better results than either partial least squares modeling or regression modeling, indicating greater robustness in the NN models. Surface plots based on the predicted values from the NN models yielded process and storage conditions for favorable versus cohesive flow behavior for DDGS. Modeling of DDGS flowability using NN has not been done before, so this work will be a step toward the application of intelligent modeling procedures to this industrial challenge.

Influence of Surface Area on the Flowability Behaviour of Self-Flow Refractory Castables

Alumina, with high melting point (2050°C), high hardness and mechanical strength, and excellent abrasion resistance, is one of the most common raw materials used in self-flow refractory castables (SFRC) for monolithic linings and is commercially available in various fine to coarse size classes. However, the performance of the refractory lining depends not only on the properties of its ingredients but also on its easy installation (good flowability). The aim of this work was to evaluate the relationship between the flowability index (FI) of fresh castable and the specific surface area (SSA) of its particles, which is mostly determined by the finer particles content. The results obtained showed that, by controlling the proportion between matrix and aggregate, it is possible to control the SSA of the refractory castable and find a mathematical relationship between the specific surface area and the minimum flowability index required to obtain a self-flow refractory castable. It is, thus, possible to optimize the refractory castable size composition and obtain an estimate for FI as a function of SSA. Using a minimum 45 wt.% matrix content in the castable mixture, a SSA value above 2.215 m2/g is obtained, which leads to FI ≥ 80%, the recommended value for self-flow.

Influence of behaviour of alumina slurry on quality of alumina powder prepared by jet wheel impact atomization

Alumina slurries prepared in pilot plant scale have been characterized in terms of slurry rheology and stability and processed in a spray drier based on jet wheel impactor for atomization. Spheroidal alumina granules have been produced and their density, particle size and flowability behaviour are determined. Microstructure of the spheroidal granules has been observed under SEM and results are reported. The powders find application in plasma spray coatings, production of dense ceramic parts, components and tiles.