Powder Flow Characteristics Research Articles

Experimental investigation of ZnO powder flow and feeding characterization for a solar thermochemical reactor

The past two decades have seen a surge in applications of concentrated solar power (CSP) technology. The generation of solar-fuels, such as hydrogen, via CSP-thermal receiver/reactor technology has progressed from large scale demonstration to preliminary commercial venture. Solar receiver/reactors vary widely, and one of the distinguishing characteristics between reactors is the way in which reactants are introduced into the high-temperature reaction environment. Here, we focus on gravity-driven feeding of solid-particle reactants via hoppers and metering splines which can be employed for solar-thermochemical dissociation of metal oxides during continuous or batch processing. This relatively simple method can provide consistent and uniform reactant flow with high durability and low maintenance. We present experiments and analysis of gravity feeding of solid particles for CSP applications, focusing on the case study of 1–5μm ZnO powder at mass flow rates of 0–2g/s. ZnO powder feeding is facilitated by adding vibration to the hopper followed by metering past a rotating spline, and delivered via gravity to an ultra-high temperature reaction cavity comprised of inclined alumina tile reaction surfaces. This paper will address hopper and spline design, feed rate characterization and modeling, particle residence time, and the effect of moisture and hopper vibration on the effective delivery of ZnO powder to the thermochemical reactor.

Galenic approaches in troubleshooting of glibenclamide tablet adhesion in compression machine punches

This study aimed to examine the adhesion of glibenclamide 5mg tablets to the tools of compression machines. This problem is not commonly reported in the literature, since it is considered as tacit knowledge. The starting point was the implementation of three technical alternatives: changing the parameters of compression, evaluating the humidity of the powder blend and the manufacturer of the lubricant magnesium stearate. The adhesion was directly related to the characteristics of magnesium stearate from different manufacturers, and the feasibility of evaluating powder flow characteristics by different techniques that are not routinely followed in various pharmaceutical companies. In vitro dissolution tests showed that the magnesium stearate manufacturer can influence on the dissolution profile of glibenclamide tablets. This study presented various aspects of tablet adhesion to compression machine punches. Troubleshooting approaches can be, most of times, conducted based on previous experience, or an experimental research needs to be implemented in order to have confident results.

Feasibility and characterization of gummy exudate of Cochlospermum religiosum as pharmaceutical excipient

Gums, resins, mucilages, latex are common constituents of plants secretions that are utilized in food, textile, and leather industries for their versatile applicability. Some of these also have their significant impact in food and pharmaceutical sector due to their biocompatibility, safety, low cost, biodegradability. The gummy exudates of Cochlospermum religiosum has also been applied as excipient in drug delivery devices and may have the potential of exploration in novel drug delivery development. In the present study, various physicochemical properties such as particle-size distribution, thermal behavior, powder flow characterization, acidic volatility estimation, moisture sorption, microbial load, accelerated stability study, hydration capacity were studied. The rheological behavior of the exudate was also studied in different strength by rheokinetics models. The acute and subacute toxicity study of gum was also performed in albino rats through oral administration. The Fourier transform infrared spectrogram showed the presence of polysaccharide structure in exudate and the thermal behavior was also completed in three stages of decomposition confirming the polysaccharide nature of exudate. The results of study revealed the safety and non-toxic nature of gum in terms of enzymological and hematological parameters. Increment in shear stress on increasing shear rate confirmed the pseudoplastic nature that may be a suitable characteristic for sustained release drug delivery devices. All other parameters studied also emphasized the applicability and suitability of gummy exudate of Cochlospermum religiosum as a multifunctional, versatile novel bio-excipient for formulation development.

Effects of powder flow properties on capsule filling weight uniformity

Filling capsules with the right amount of powder ingredients is an important quality parameter. The purpose of this study was to develop effective laboratory methods for characterizing flow properties of pharmaceutical powder blends and correlating such properties to weight variability in filled capsules. The methods used for powder flow characterization were bulk and tapped density, gravitational displacement rheometer (GDR) flow index, Freeman Technology V.4 (FT4) powder rheometer compressibility, FT4 basic flow energy (BFE), and cohesion parameters [cohesion, (C) and flow factor (ffc)] measured in a shear cell also using the FT4. Capsules were filled using an MG2-G140 continuous nozzle dosator capsule-filling machine. Powder flow properties were the most predominant factors affecting the weight and weight variability in the filled capsules. Results showed that the weight variability decreased with increasing bulk and tapped density, ffc and BFE, while the weight variability increased with increasing compressibility, cohesion and GDR flow index. Powder flow properties of the final blends were significantly correlated to the final capsule weight and weight variability of the filled capsules.

Ambient and Cryogenic Grinding of Fenugreek and Flow Characterization of Its Powder

AbstractComparative study on ambient and cryogenic grinding based on determination of flow behavior of their powders has been discussed extensively in the present study. Cryogenic grinding helps in retention of aroma, volatile oil and protein structure of fenugreek (Trigonella foenum‐graecum). Angle of slide, volume, density of powder, Hausner ratio, Carr index, angles of repose and particle size distribution were determined at different moisture content ranging from 11 to 20% on dry basis for ambient and cryogenic grinding. Angle of slide for different planes was found to be increasing in the range of 39–60°. Dynamic and drained angle of repose were found to be increasing for ambient and cryogenic grinding. Mean, mode, median, variances, deviations, skewness, kurtosis and uniformity of powder were also evaluated. It may be concluded that ambient and cryogenically ground fenugreek powder affects its flow behavior, in turn resulted in direct influences on handling, transportation and processing practices.Practical ApplicationsThe flow characteristics of fenugreek powder will be useful to have control over processing parameters and will lead to improved quality and output of the fenugreek powder. The present work on flow characteristics of fenugreek powder provides reliable information for design of equipments for handling, processing, packaging and transportation of ground powder, which will in turn be economically helpful for powder processing industries. Sticking and agglomeration of powder also cause loss of economy that can be overcome with the help of present studies.

Halogen Bonding and Pharmaceutical Cocrystals: The Case of a Widely Used Preservative

3-Iodo-2-propynyl-N-butylcarbamate (IPBC) is an iodinated antimicrobial product used globally as a preservative, fungicide, and algaecide. IPBC is difficult to obtain in pure form as well as to handle in industrial products because it tends to be sticky and clumpy. Here, we describe the preparation of four pharmaceutical cocrystals involving IPBC. The obtained cocrystals have been characterized by X-ray diffraction, solution and solid-state NMR, IR, and DSC analyses. In all the described cases the halogen bond (XB) is the key interaction responsible for the self-assembly of the pharmaceutical cocrystals thanks to the involvement of the 1-iodoalkyne moiety of IPBC, which functions as a very reliable XB-donor, with both neutral and anionic XB-acceptors. Most of the obtained cocrystals have improved properties with respect to the source API, in terms, e.g., of thermal stability. The cocrystal involving the GRAS excipient CaCl2 has superior powder flow characteristics compared to the pure IPBC, representing a promising solution to the handling issues related to the manufacturing of products containing IPBC.

Role of consolidation state in the measurement of bulk density and cohesion

Characterization of powder consolidation and flow is important to a large number of industries that process solids. A variety of powder testers exist today, however most are application specific and results they provide are mainly qualitative. Comparison studies have been attempted previously; their main focus was whether various methods correlate, while the reasons for disagreement in the results have seldom been investigated. Among the different methods used to characterize powder flow behavior, density-based methods are some of the simplest and most popular. They are also some of the least sensitive and least reproducible. A method comparison study was performed to characterize the variability in bulk density as measured by various powder flow characterization methods. It was found that the density of the powders tested in most unconsolidated methods had a near-perfect linear correlation with one another, suggesting that there exists a critical “dilated” density value that is independent of the measurement method and can be considered a material property. The densities of the powders in consolidated states correlated poorly, especially for the methods where consolidation mechanisms were not tightly controlled (i.e. tapping). In addition, the effect of the consolidation state of the powder bed during testing on cohesion measurements was studied. The cohesion measured by shear cells at differing consolidation states and by an avalanching method, during which the powder bed is dilated, were compared. It was found that the differences in cohesion results from the shear cells tested can be attributed to differences in the powder consolidation state. Cohesion results acquired from a dilated powder bed correlate more linearly with the shear cell cohesion results at low consolidation stresses than at high consolidation stresses; further supporting the impact of the powder bed packing state on the measurement of cohesion.

Effects of storage conditions, formulation, and particle size on moisture sorption and flowability of powders: A study of deliquescent ingredient blends

Powder flow characteristics are important for the manufacturability and use of powders. Sticking and agglomeration resulting from exposure to relative humidity (RH) reduce flowability and may be influenced by powder composition and particle size and shape. Deliquescence is an important trait of water-soluble crystalline ingredients; however, few studies address the physical stability of powders relative to their deliquescence behavior. The objective of this study was to determine the impact of formulation, particle size, and storage conditions on the flowability and caking of deliquescent ingredient blends. Sucrose, fructose, sodium chloride, and citric acid were used. Treatment effects of formulation (single ingredient and binary blends at select ratios), particle size (50, 150, ~500μm), and storage time (0–28days) on powder flow after storage at 10% and 30% RH below the deliquescence point were examined, and moisture sorption was monitored. Scanning electron microscopy imaging investigated the influence of particle size on the physical state of the solid following RH treatment. Glass spheres were studied to show the effects of particle size and RH on powder flow and moisture sorption isotherms of an insoluble solid with a hydrophilic surface. All treatment conditions affected the flowability of the powders. Interactions between treatments were also present, indicating that there are multiple factors associated with powder flowability and treatments may have synergistic effects. For a given formulation, particle size and the distance between the storage RH and deliquescence RH are particularly important to control in order to maintain powder flowability.

Characterization of Powder Flowability for Die Filling

Inter-tablet variations in composition and weight depend on the flowability of pharmaceutical formulations. In this study, the concept of critical filling speed, which was proposed to characterize the flowability with special application to die filling, is evaluated and compared with other powder flow characterization techniques. It has been found that the critical filling speed provides a consistent gauge of the powder flowability with the poured angle of repose, Carr index, Hausner ratio, and flow functions from shear cell testing. However, the mass flow rate and the time to discharge a certain amount of powder through flowmeters showed a different trend, indicating that different powder flow behaviors are involved in these tests. This implies it is necessary to employ a powder flowability measurement technique that mimics the powder flow behavior in the actual application.

Production of amorphous starch powders by solution spray drying

AbstractThe spray drying of starch/maltodextrin formulations was evaluated as a potential technology for the manufacturing of amorphous thermoplastic starches. Mixtures of starches with high to low amylose (Am)–amylopectin (Ap) ratios were spray‐dried from water‐based solutions and granular dispersions. The effects of the feed composition on the morphology and physical properties of the end product were investigated with the spray‐drying conditions kept constant. Powders obtained from the starch solutions were totally amorphous, and the particle size characteristics were not affected by the applied variations in composition. The particles obtained from the solution‐dried formulations were small, highly irregular, and shriveled, and the bulk densities were low. Independent of the Am/Ap ratio, the particles could easily be redissolved and showed low viscosities. The spray‐dried powders obtained from the starch–water dispersions very much retained the granular structure present in the native components. All showed viscosities, crystallinity patterns, gelatinization, and powder flow characteristics in line with expectations for Am/Ap‐based granular mixtures. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Compactibility and compressibility studies of Assam Bora rice starch

A comparison study was made on the powder flow characteristics, tableting properties of experimental Assam Bora rice starch, obtained from the variety Aghuni Bora of Oryza sativa and the mechanical properties of tablets made up of it with those of official Starch 1500®. The influences of physical and geometrical properties of both the starch were evaluated with regards to their compression properties. It has been found that Assam Bora rice starch reflects better physical characteristics such as higher bulk and tap densities, less porosity, better powder packing ability, minimum lubricant sensitivity, large surface area and improved flowability. Apart from that the mechanical properties, such as toughness and Young's modulus of Assam Bora rice starch were also compared with that of Starch 1500®. It has been also brought into result that compactibility of Assam Bora rice starch was not affected by the blending time. Further compaction properties of the experimental starch were evaluated by using Kawakita and Heckel equations and compared well with those of Starch 1500®. The result obtained shows that it mainly deforms by plastic deformation. Their onset of plastic deformation and strain rate sensitivity as compared to that of Starch 1500® demonstrates its potential use as a direct compression filler-binders.

Parametric study on a coaxial multi-material powder flow in laser-based powder deposition process

The manner with which the composite powder particles injected into the laser formed molten pool decides the deposition quality in a typical laser-based powder deposition of composite material. Since, the morphology and physical properties of nickel (Ni) and tungsten carbide (WC) are different their powder flow characteristics such as the powder particles stream structure, maximum concentration at the converging spot, and the powder particles velocity are noticeably different. In the current study, a computational fluid dynamics (CFD) based powder flow model is established to characterize the coaxial powder flow behavior of Ni–WC composite powders. The key powder flow characteristics such as the stand-off distance, the diameter of the powder stream at the stand-off distance, and the velocity of the powder particles are measured using three different vision based techniques. Both the numerical and experimental results reveal the exact stand-off distance where the substrate needs to be placed, the diameter of the concentration spot of powder at the stand-off distance, and a combination of suitable nozzle angle, diameter, and carrier gas flow rate to obtain a maximum powder concentration at the stand-off distance with a stable composite powder flow.

Assessment of powder flow characteristics in incoherent soup concentrates

Soup mixtures represent specific flow characteristics while particles of different sizes and properties form a homogeneous mixture. In such mixtures, particle–particle interactions differ with addition of different fat types. This study was done to present a characterization and comparison of the cohesion index, powder flow speed dependency and caking properties of four different aggregates of fat particles with three different moisture contents, used in various compositions of powdered soup concentrates. ESEM micrographs have shown that different fat types bind particles differently. The moisture content of cream soup concentrates has a significant influence on cake height ratio of all cycles – more moisture causes higher cake height ratios (from rs=0.86 to rs=0.76; p<0.05). Cream soup concentrates cake strength values are also significantly influenced by the mixtures moisture content – higher moisture content samples showed higher cake strength values (rs=0.73, p<0.05). There is a significant correlation between compaction coefficients of all speeds and cake height ratios of all cycles for the cream soup concentrates. Combination of measuring techniques (Powder Flow Analyzer, ESEM and Mastersizer) together with Spearman’s Rank Order Correlation, as a method of non-parametric statistics, provides parturient results in characterization of extremely non-homogenous powder mixtures.

Investigation of the extent of surface coating via mechanofusion with varying additive levels and the influences on bulk powder flow properties

The objective of this study was to investigate if the coating extent created by a mechanofusion process corresponded with observed changes in bulk powder properties. A fine lactose powder (approximate median diameter 20 μm) was dry coated with magnesium stearate using from 0.1 to 5% (w/w) content. An ultra-thin coating layer of magnesium stearate was anticipated, but previous attempts to determine such thin layers on these fine particles have had limited success, with poor resolution. In this study, the surface coating was examined using the state-of-the-art XPS and ToF-SIMS systems. The powder flow was characterized by Carr index and shear cell testing. XPS was successfully applied to demonstrate variations in surface coverage, as a function of additive levels, and indicated near complete coating coverage at additive levels of 1% (w/w) and above. ToF-SIMS results supported such coating coverage assessment, and indicated coating uniformly across the fine particle surfaces. The flow metrics employed could then be related to the coating coverage metrics. The mechanofusion process also modified the apparent surface roughness observed by SEM and BET. It was suggested that the changes in the surface chemical composition exerted a more evident and direct impact on the powder cohesion and flow characteristics than the changes in the surface morphological properties after the mechanofusion in this study.

An integrated study of die powder fill, transfer and compaction process using digital image correlation method

A major advantage of the powder metallurgical (P/M) manufacturing process is its ability to shape powder directly into a final component with a primary goal of a high quality, homogeneity of density and mechanical properties and productivity. In this research, powder die filling, powder transfer and powder compaction process have been studied in succession using a novel experimental set-up that utilizes a high strength transparent wall section to observe and record the particle movement and powder compaction during the entire sequence leading up to the formation of a green part. The natural powder pattern itself, as observed from the transparent wall section, is utilized for obtaining full-field displacement and strain measurement. The test set-up and the strain measurement technique offer a means of quickly obtaining density distribution data in select cases. In addition to the above, several powder flow characteristics during die filling, powder transfer and powder compaction under a range of test conditions have been noted through a series of high-speed photographic recordings. The observations reveal increased porosity in the die wall region due to friction and formation of shear bridges during powder transfer stages during suction filling. Spatial density data from optical strain measurements in the top, middle and bottom regions of the die are consistent with similar bulk density measurements from mass and volume of the 3 regions.

Effecting Factors Study for Powder Flow Characteristics

To understand the influence of external factors on powder flow process from the hopper, and to get the prerequisite to control the flow rate, by doing a lot of experiments. In this paper, the size distribution regulation was acquired by SCIROCCO 2000 (dry method) laser granulometry, and then the affection on flow rate from many external factors were separate considerations. As resluts, when the semi-vertical angle was smaller, the flow type was whole flow; the relation between way dimension of feed opening and flow is nonlinearity; the rate between hopper weight and way dimension of feed opening could affect the flow when it was smaller than 5; the flow was stable when the ratio between the powder depth and way dimension of feed opening is bigger than 1.5. At the same time, it would be one effective indirect measurement method by measuring the way dimension of feed opening under special condition.

Cationic surfactants-modified natural zeolites: improvement of the excipients functionality

Context: In this study an investigation of cationic surfactants-modified natural zeolites as drug formulation excipient was performed. Objective: The aim of this work was to carry out a study of the purified natural zeolitic tuff with high amount of clinoptilolite as a potential carrier for molecules of pharmaceutical interest. Materials and methods: Two cationic surfactants (benzalkonium chloride and hexadecyltrimethylammonium bromide) were used for modification of the zeolitic surface in two levels (equal to and twice as external cation-exchange capacity of the zeolitic tuff). Prepared samples were characterized by Fourier transform infrared spectroscopy, thermogravimetric, high-performance liquid chromatography analysis, and powder flow determination. Different surfactant/zeolite composites were used for additional investigation of three model drugs: diclofenac diethylamine, diclofenac sodium, and ibuprofen by means of adsorption isotherm measurements in aqueous solutions. Results: The modified zeolites with two levels of surfactant coverage within the short activation time were prepared. Determination of flow properties showed that modification of zeolitic surface reflected on powder flow characteristics. Investigation of the model drugs adsorption on the obtained composites revealed that a variation between adsorption levels was influenced by the surfactant type and the amount present at the surface of the composites. Discussion and conclusion: In vitro release profiles of the drugs from the zeolite-surfactant-drug composites revealed that sustained drug release could be attained over a period of 8 hours. The presented results for drug uptake by surfactant-zeolite composites and the afterward drug release demonstrated the potential use of investigated modified natural zeolite as excipients for advanced excipients in drug formulations.

Development of a New Method to Get a Reliable Powder Flow Characteristics Using Only 1 to 2 g of Powder

In powder technology, it is often important to directly measure real powder flow rate from a small amount of powder. For example, in pharmaceutical industry, a frequent problem is to determine powder flow properties of new active pharmaceutical ingredient (API) in an early stage of the development when the amount of API is limited. The purpose of this paper is to introduce a new direct method to measure powder flow when the material is poorly flowing (cohesive) and the amount of material is about 1 to 2 g. The measuring system was simple, consisting of a flow chamber and electronic balance and an automated optical detection system, and for each measurement, only 1 to 2 g of sample was required. Based on the results obtained with this testing method, three selected sugar excipients, three grades of microcrystalline cellulose, and APIs (caffeine, carbamazepine, and paracetamol) can be classified as freely flowing, intermediate flowing, and poorly flowing powders, respectively. The average relative standard deviation for the flow time determinations was not more than 2-10%. The present novel flowability testing method provides a new tool for a rapid determination of flowing characteristics of powders (e.g., inhalation powders) and granules at a small scale.

G0600-3-4 熱流動化木粉の押出成形時における成形性及び流動特性(熱工学部門一般講演(3):伝熱(3))

Woody biomass has come to attract attention as renewable resources because of the issue of global warming and air pollution. Plastics substitution is one of the most promising utility form of woody biomass, and many studies have been made on the molding method of wood. But that has been no study on the injection molding of thermal fluid wood powder. To clarity viscous property of thermal fluid wood powder, experimental studies on the flow characteristics of thermal fluid wood powder are conducted. It is confirmed that thermal fluid wood powder has non-Newtonian flow property, and the empirical equation to predict the viscosity is developed.

Development of green composite consists of woodchips, bamboo fibers and biodegradable adhesive

From the viewpoint of the effective utilization of waste wood, the green composite which is produced by solidifying woodchips has been developed [Miki M, Takakura N, Kanayama K, Yamaguchi K, Iizuka T. Effects of forming conditions on compaction characteristics of wood powders. Trans Jpn Soc Mech Eng C 2003;69(678):502–8 [in Japanese]; Miki M, Takakura N, Kanayama K, Yamaguchi K, Iizuka T. Effects of forming conditions on flow characteristics of wood powders. Trans Jpn Soc Mech Eng C 2003;69(679):766–72 [in Japanese]; Miki M, Takakura N, Iizuka T, Yamaguchi K, Kanayama K. Possibility and problems in injection moulding of wood powders. Trans Jpn Soc Mech Eng C 2004;70(698):2966–72 [in Japanese]]. Since the composite was solidified by the compressive load without the binder, it did not have the high strength and was very brittle, and it had no water resistance [Kinoshita H, Kaizu K, Koga K, Tokunaga H, Ikeda K. In: Proceeding of the Japan Society of Mechanical Engineers M& M2007; 2007. CD [in Japanese]]. In this study, to improve these defects, it was proposed that a biodegradable resin as an adhesive and bamboo fibers as reinforced fibers were applied to the woodchip composite. By using woodchips with two kinds of the particle size, bamboo fibers with three kinds of the length and the biodegradable adhesive, several kinds of specimens changed mixing ratio of those materials were produced by compression molding at the appropriate temperature. By examining the bending strength and impact strength of the composites, it was found that the high bending strength was obtained in the case where woodchips with the small particle size and long bamboo fibers were used, and the high impact strength was obtained in the case where woodchips with the large particle size and long bamboo fibers were used.