Powder Bulk Density Research Articles

Assessment of Pharmaceutical Powder Flowability using Shear Cell-Based Methods and Application of Jenike’s Methodology

Jenike's approach to hopper design for a large-scale (3150 L) conical hopper was applied to pharmaceutical powders to evaluate flow issues, such as funnel flow or cohesive arching. Seven grades of microcrystalline cellulose (MCC) and six powder blends were tested. A Schulze Ring Shear Tester measured the flow function, wall friction (using stainless steel coupons with a #2B or #8 finish) and compressibility. Hopper Index (HI, maximum hopper angle required for mass flow) and Arching Index (AI, minimum hopper outlet size to prevent cohesive arch formation) were computed using Mathcad(©) . For MCC, a linear relationship was observed between median particle size and the Jenike flow function coefficient. A curvilinear relationship was observed for powder blends indicating more complex flow behavior than based on median particle size alone. Powder bulk density had a minimal effect on AI for MCC grades. Overestimation of AI can occur with this method for pharmaceutical powders because the true shape of the flow function is not defined at very low consolidation pressures and linear extrapolation becomes unrepresentative. This instrumental limitation underscores the need for a precise and accurate test method to determine powder flow functions at very low levels of consolidation stress for pharmaceutical applications.

Increasing flowability and bulk density of PE-HD powders by a dry particle coating process and impact on LBM processes

Purpose – The purpose of this paper is to demonstrate the processability of cohesive PE-HD particles in laser beam melting processes (LBM) of polymers. Furthermore, we present a characterization method for polymer particles, which can predict the quality of the powder deposition via LBM processes. Design/methodology/approach – This study focuses on the application of dry particle coating processes to increase flowability and bulk density of PE-HD particles. Both has been measured and afterwards validated via powder deposition of PE-HD particles in a LBM machine. Findings – For efficient coating in a dry particle coating process, the PE-HD particles and the attached nanoparticles need to show similar surface chemistry, i.e. both need to behave either hydrophobic or hydrophilic. It is demonstrated that dry particle coating is appropriate to enhance flowability and bulk density of PE-HD particles and hence considerably improves LBM processes and the resulting product quality. Originality/value – At present, in LBM processes mainly polyamide (PA), 12 particles are used, which are so far quite expensive in comparison to, for example, PE-HD particles. This work provides a unique and versatile method for nanoparticulate surface modification which may be applied to a wide variety of materials. After the coating, the particles are applicable for the LBM process. Our results provide a correlation between flowability and bulk density and the resulting product quality.

Real time monitoring of powder blend bulk density for coupled feed-forward/feed-back control of a continuous direct compaction tablet manufacturing process

The pharmaceutical industry is strictly regulated, where precise and accurate control of the end product quality is necessary to ensure the effectiveness of the drug products. For such control, the process and raw materials variability ideally need to be fed-forward in real time into an automatic control system so that a proactive action can be taken before it can affect the end product quality. Variations in raw material properties (e.g., particle size), feeder hopper level, amount of lubrication, milling and blending action, applied shear in different processing stages can affect the blend density significantly and thereby tablet weight, hardness and dissolution. Therefore, real time monitoring of powder bulk density variability and its incorporation into the automatic control system so that its effect can be mitigated proactively and efficiently is highly desired. However, real time monitoring of powder bulk density is still a challenging task because of different level of complexities. In this work, powder bulk density which has a significant effect on the critical quality attributes (CQA’s) has been monitored in real time in a pilot-plant facility, using a NIR sensor. The sensitivity of the powder bulk density on critical process parameters (CPP’s) and CQA’s has been analyzed and thereby feed-forward controller has been designed. The measured signal can be used for feed-forward control so that the corrective actions on the density variations can be taken before they can influence the product quality. The coupled feed-forward/feed-back control system demonstrates improved control performance and improvements in the final product quality in the presence of process and raw material variations.

Comparison of three rotational shear cell testers: Powder flowability and bulk density

Developed to aid in the design of hoppers and silos, the shear cell is now frequently used to rank the flowability of powders relative to one another. While standards, such as ASTM D6773 and D6128, exist for shear cell tests, there are still differences between commercially available shear cell testers, such as cell geometry and size. In this work, we used two materials, a free-flowing alumina and a cohesive alumina, to compare measurements from three commercially available rotational shear cells. Results were collected and compared for cohesion, unconfined yield stress, major principal stress, pre-shear stress, flow function coefficient, bulk density, effective angle of internal friction, and the angle of internal friction. ANOVA methods were used to determine the statistical significance and relative size of each of these effects. This work has found that while, as expected, the material type has the largest effect on the shear cell results, the consolidation at which the material was tested and the tester type are also statistically significant effects. These results indicate that care should be taken when comparing the results between different shear cells.

Parametric study to determine the effect of temperature on oil solidifier performance and the development of a new empirical correlation for predicting effectiveness

Temperature can play a significant role in the efficacy of solidifiers in removing oil slicks on water. We studied and quantified the effect of temperature on the performance of several solidifiers using 5 different types of oils under a newly developed testing protocol by conducting experiments in constant temperature rooms set at 22°C and 5°C. The results indicated that solidifier efficiency decreased substantially at the lower temperature, especially at lower application rates. The removal efficiency of the solidifier was in general directly proportional to temperature, except for the heavier oils, where removal by attachment was observed. Solidifier products with lower powder bulk density exhibited the best removal effectiveness. Analysis of experimental data yielded empirical correlations involving certain operational variables such as application rate, temperature, solidifier property (bulk density), and oil property (viscosity). Regression analysis was used to fit a mathematical model to the experimental solidifier effectiveness data.

Impacts of spray-drying conditions on the physicochemical properties of soy sauce powders using maltodextrin as auxiliary drying carrier

Naturally brewed soy sauce was spray-dried using a pilot-scale spray-dryer with two-fluid atomization nozzle. Maltodextrin (DE 10) was incorporated into liquid soy sauce as a drying aid, to form a uniform liquid of 40% w/v. The influence of spray-drying parameters including inlet drying air temperature, feed flow rate, and atomization air flow was examined. The product yield, bulk density, cohesiveness and particle size of the spray-dried powders were found to be influenced by the spray-drying conditions.Extremely cohesive soy sauce powders were obtained when the air-drying temperature reached 180°C and above. Moreover, surface NaCl concentration of the soy sauce powders was shown to have insufficient expression in comparison with that in bulk. Surface NaCl content was also found to increase with increasing drying temperature.

Experimental investigations of tin cementation in dispersion form

The results of experimental investigations related to cementation extraction of tin in the dispersion form from sulfate solutions are described. The dependence of stationary aluminum potential on chlorine ion concentration in sulfate solution of divalent tin is shown. The polarization measurements of electrode processes of the Al–Sn galvanic cell have been carried out. The cementation conditions dependence of the dispersivity and bulk density of tin powder is established

Investigation of copper powder cementation deposition process

Copper cementation in dispersed form from sulphate solutions has been carried out by metallographic, polarization, weight, and volumetric methods. The mass balance of the cementation process is determined. The effect of chloride ions on the copper deposit shape is shown. Polarization measure- ments of the electrode processes of the aluminum-copper couple are performed. The full two-factor experiment has been carried out, which results in regression equations showing average particle size, bulk density, and deposition rate of copper powder depending on the cementation reaction conditions.

Ohmic heating-assisted extraction of anthocyanins from black rice bran to prepare a natural food colourant

Abstract Black glutinous rice bran (Oryza sativa L.) is a potential source of the dark purple anthocyanin pigments. This study investigated some quality aspects and bioactive compounds of the colourant powder obtained from rice bran extracted by ohmic heating (OHM) assisted solvent extraction. The moisture content (MC) of the bran was adjusted to 30% and 40%. Four different levels of electric field strengths (E) of 50, 100, 150, and 200 V cm– 1 were applied. The results showed that OHM assisted solvent extraction was a promising method offering both high yield and high concentration of bioactive compounds. The solubility, aw, bulk density, and color values (L*, C*, and h°) of the colorant powder of all treatments were comparable. The colourant powder obtained from the bran extracted using OHM with 30% MC (E=100, 150, and 200 V cm– 1) and 40% MC (E = 50, 100, 150, and V cm– 1) had the highest level of bioactive compounds. Industrial relevance The ohmic heating was a promising technique to assist solvent extraction of anthocyanin pigment from black rice bran. The colourant powder prepared by ohmic heating assisted (CP-OHM) had higher colourant yield, anthocyanin pigments, and bioactive compounds than conventional methods. The present study suggested that ohmic heating could be applied to develop industrial production scale of natural colourants.

Influence of Hot Bed Spray Dryer Parameters on Physical Properties of Peppermint (Mentha piperita L.) Tea Powder

Abstract In this study, the effects of some processing parameters on moisture content, drying yield, bulk density, solubility and particle size of peppermint tea powders obtained from a hot bed spray dryer were investigated. In this method of drying, a heated bed is used instead of heated air to simplify spouted bed drying method and lower the cost of drying. A wheel rotary atomizer was employed for spraying of material and a frustum-shaped bed heated by thermal elements was applied around the atomizer. Independent variables were bed temperature (130, 140 and 150°C), feed flow rate (10, 20 and 30 L/h) and rotary speed of atomizer (7,000, 12,000 and 16,000 rpm). The moisture content of dried tea powders ranged from 3.13 to 4.87%. The highest drying yield (87.23%) and solubility (89.6%) were obtained at the bed temperature of 130°C and feed flow rate of 10 L/h.

Antisolvent precipitation of novel xylitol-additive crystals to engineer tablets with improved pharmaceutical performance

The purpose of this work was to develop stable xylitol particles with modified physical properties, improved compactibility and enhanced pharmaceutical performance without altering polymorphic form of xylitol. Xylitol was crystallized using antisolvent crystallization technique in the presence of various hydrophilic polymer additives, i.e., polyethylene glycol (PEG), polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA) at a range of concentrations. The crystallization process did not influence the stable polymorphic form or true density of xylitol. However, botryoidal-shaped crystallized xylitols demonstrated different particle morphologies and lower powder bulk and tap densities in comparison to subangular-shaped commercial xylitol. Xylitol crystallized without additive and xylitol crystallized in the presence of PVP or PVA demonstrated significant improvement in hardness of directly compressed tablets; however, such improvement was observed to lesser extent for xylitol crystallized in the presence of PEG. Crystallized xylitols produced enhanced dissolution profiles for indomethacin in comparison to original xylitol. The influence of additive concentration on tablet hardness was dependent on the type of additive, whereas an increased concentration of all additives provided an improvement in the dissolution behavior of indomethacin. Antisolvent crystallization using judiciously selected type and concentration of additive can be a potential approach to prepare xylitol powders with promising physicomechanical and pharmaceutical properties.

Influence of Mechanical Activation of Powder on SLS Process

The paper presents the results of the experiment, describing the effect of mechanical activation of powder Cu and Ni on the nature of their SLS-sintering method. The changes in structure and bulk density of powders after mechanical activation are revealed, which generally has a positive effect on the synthesis process of a product.Intorduction

On the interaction between alumina batch and cryolite-alumina melt

The influence produced by the bulk density of alumina powder on the rate of its dissolution in a cryolite-alumina melt of the composition, wt %, 5.5 CaF2, 1.5 MgF2, 0.3 Al2O3, 2.28 CR is studied. The melt temperature is 950°C; the dissolution rate is determined visually and by changes in the concentration of aluminum oxide in the melt. It is discovered that the dissolution rate of alumina increases in proportion to its bulk density.

Influence of Operating Parameters on Physicochemical Properties of Fruit Juice Powders Produced by Spray Drying

This paper investigated the influence of operating parameters such as inlet air temperature, compressed air flow rate, concentration of carrier agent and type of carrier on the physicochemical properties of fruit juice powders produced by spray drying.The results indicated that increasing inlet air temperature resulted in the larger size particles with smoothly spherical appearance, and to lower bulk density and moisture content. The bulk density of powders also decreased with increasing carrier agent concentration, decreasing compressed air flow rate. The higher feed flow rate negatively affected process yield and positively influenced moisture content, and occurring the wall deposition easily. Additionally, the anthocyanin retention mainly depends on the inlet air temperature and type of carrier. Moreover, the novel methods and ideas to this problem in the next studies were presented.

Influence of protein concentration on the physical characteristics and flow properties of milk protein concentrate powders

This study investigated the physical characteristics and flow properties of seven milk protein concentrate (MPC) powders, ranging from 36.6 (MPC35) to 89.6 (MPC90) % (w/w) protein in dry-matter. MPC80, MPC85 and MPC90 had the smallest particle sizes (P<0.05) and significantly higher (P<0.05) specific surface areas, as measured using nitrogen adsorption. The bulk density of MPC powders decreased with increasing protein content, due to increased (P<0.05) levels of interstitial and occluded air. Flow testing indicated that high protein MPC powders were more compressible (P<0.05), had lower flow index values (P<0.05) and required larger (P<0.05) outlet diameters for optimal flow in mass-flow hoppers compared to lower protein MPC powders.

Optimization of spray drying process in cheese powder production

In this study, white cheese powder was produced using a pilot scale spray drier and response surface methodology was used to optimize the operating conditions of spray drying. The independent variables were inlet drying temperature, atomization pressure and outlet drying temperature, while drying experiments were carried out with an inlet drying air temperature range of 160–230°C, an outlet drying air temperature range of 60–100°C and an atomization pressure range of 294–588kPa. The responses were nonenzymatic browning index, free fat content, solubility index, bulk density of cheese powder and exergy efficiency of the spray drying process. Optimum operating conditions were found to be an inlet drying temperature of 174°C, atomization pressure of 354kPa, and an outlet drying temperature of 68°C. At this optimum condition, nonenzymatic browning index, free fat content, solubility index, bulk density and exergy efficiency were found to be 0.123OD/gdm, 40.7%, 82.7%, 252kg/m3 and 4.81%, respectively.

Experimental Study on Fires Extinguishing Properties of Melamine Phosphate Powders

A new type of multipurpose dry powders (MP dry powders) with melamine phosphate as extinguishing component was prepared by using the ball-milling method. The main physical properties of MP dry powders were tested, and the extinguishing experiments including wood crib fire tests and pool fire tests were conducted to study the extinguishing properties of MP dry powders comparing with commercial ordinary ammonium phosphate dry powders. The thermal decomposition properties of melamine phosphate were studied through thermogravimetric (TG) and differential scanning calorimetry (DSC). The results show that the bulk density of MP dry powders is lower than the required value, and the other main physical properties accord with the demands of Chinese Standards. MP dry powders have higher extinguishing effectiveness on wood crib fire tests and pool fire tests than that of commercial ordinary ammonium phosphate dry powders. Finally, the extinguishing mechanisms were discussed on the base of thermal decomposition properties of melamine phosphate.

Piezoelectric Ignition of Nanocomposite Energetic Materials

Piezoelectric initiators are a unique form of ignition for energetic material because the current and voltage are tied together by impact loading on the crystal. This study examines the ignition response of an energetic composite composed of aluminum and molybdenum trioxide nanopowders to the arc generated from a lead zirconate and lead titanate piezocrystal. The mechanical stimuli used to activate the piezocrystal varied to assess ignition voltage, power, and delay time of aluminum–molybdenum trioxide for a range of bulk powder densities. Results show a high dielectric strength leads to faster ignition times because of the higher voltage delivered to the energetic. Ignition delay is under 0.4 ms, which is faster than observed with thermal or shock ignition. Electric ignition of composite energetic materials is a strong function of interparticle connectivity, and thus the role of bulk density on electrostatic discharge ignition sensitivity is a focus of this study. Results show that the ignition delay times are dependent on the powder bulk density with an optimum bulk density of 50%. Packing fractions and electrical conductivity were analyzed and aid in explaining the resulting ignition behavior as a function of bulk density.

Physical characteristics of spray-dried dairy powders containing different vegetable oils

The objective of this study was to investigate the physical characteristics of spray-dried dairy powders formulated with different oil types, spray-dried at different outlet temperatures. A model fat-filled dairy formulation (target 40% w/w total solids, comprising protein, oil and lactose) containing lactose (23.9%), sodium caseinate (5.11%) and sunflower (SO) or palm (PO) oil or a 50:50 mixture of SO/PO (in all cases 11.5% total oil) were heat-treated, homogenised and spray-dried at an outlet temperature of 80 or 90°C. Increasing outlet temperature reduced water content, water activity and tapped bulk density, irrespective of oil type, and increased solvent-extractable free fat for all oil types. Onset of glass transition (Tg) and crystallisation (Tcr) decreased at the lower outlet temperature. Oil type had no effect on powder moisture, water activity (aw), powder bulk density, particle size, fat globule size of emulsion or fat globule size of reconstituted fat-filled dairy powders.

Spray drying of ACE‐inhibitory enzyme‐modified white cheese

SummaryAn angiotensin‐I converting enzyme (ACE)‐inhibitory enzyme‐modified cheese (EMC) was spray‐dried at different inlet drying air temperatures, feeding pump rates and spraying air flow rates. Powder moisture content, bulk density, porosity, production yield and particles size were responses of interest measured. Response surface optimisation determined that if the cheese paste is pumped at feeding pump rate of 5%, sprayed with the compressed air at rate of 400 L h−1 and dried by an air at temperature of 154 °C, minimum moisture content is achieved for the produced powder. Spray drying decreased the ACE‐inhibitory of EMC significantly, but the powder was still extremely bioactive. Scanning electron microscopy (SEM) images revealed that inlet drying air temperature of 150 °C yielded a powder with relatively well‐separated particles. Higher drying air temperatures resulted in lower browning indices for the EMC powder.