Dustiness Quantification of Powders by the Fractional Release Rate

The handling of dispersed solids may lead to undesirable release of dust particles. Size and quantity of the particles transferred into the gas with time depend on the binding and separating forces in the powder. These in turn are determined by characteristic parameters of the powder and of the process. Analogous to the well‐known “fractional collection efficiency” describing the dust separation, a newly defined “fractional release rate” to quantify the release of dust is introduced. The application is demonstrated by an example and the way to further development of this innovative approach is demonstrated.     

IN SITU AERODYNAMIC SIZE CLASSIFICATION OF AEROSOLS IN THE SIZE RANGE BETWEEN 0.1 AND 100 μm FOR DUSTINESS TESTS AND POWDER CHARACTERIZATION

Airborne particles can be released by mechanical processes such as resuspension, powder handling, break-up of solids due to mechanical energy input, i.e. crushing, comminution or accidental mechanical impact. In this study, we describe a new device that collects and classifies the dust generated under lab-scale simulation of these release processes. The release process takes place within a vertical elutriator where the airborne particles are separated from the non-airborne material. The airborne fraction is subsequently classified in situ in the size range between 0.1 and 100 μm by a combination of a centrifugal classifier and a conventional cascade impactor. The system was designed to overcome possible sampling errors due to spatial dust inhomogeneities caused by the release process and to minimize wall losses during the classification process. In this paper we describe the classifier, discuss procedures for data inversion, and present calibration and performance experiments.     

Polyaniline − carbon nanohorn composites as thermoelectric materials

Thermoelectric materials can convert heat into electricity when a temperature gradient is present. The investigation of conductive polymers such as polyaniline (PANI ) and poly(3,4‐ethylenedioxythiophene) as active materials for thermoelectric generators in the room temperature range is gaining interest because of several key advantages offered by these materials. The relative ease of solution processing, their mechanical stability and flexibility together with low density and low thermal conductivity make conductive polymers suitable for integration in a thermoelectric generator. Polymers offer remarkably low thermal conductivity values but modest Seebeck coefficient and electrical conductivity. In this work, polymer/inorganic nanocomposites of PANI with carbon particles such as single wall carbon nanohorns (SWCNHs ) were prepared via solution mixing of the precursors in order to increase the electrical conductivity by means of polymer matrix/nanohorn electronic junctions. The electrical conductivity and Seebeck coefficient were estimated on PANI /SWCNH films and pressed pellets and through‐plane thermal conductivity was determined on films. The thermal stability of PANI /SWCNH composites was evaluated by means of TGA /DSC coupled with residual gas analysis. It was found that a proper concentration of SWCNHs in PANI ?(+/?)‐camphor‐10‐sulfonic acid (CSA) film was effective in increasing the electrical conductivity without decreasing the Seebeck coefficient. © 2017 Society of Chemical Industry     

不同粒度谷壳糠粉的燃烧特性

为了探索谷壳糠粉的燃烧特性,基于粉尘层和粉尘云实验研究了粒径对其最低着火温度的影响,采用哈特曼管和锥形量热仪测试了不同粒径谷壳糠粉的爆炸下限和热释放性能,利用热重/差式扫描量热仪系统地研究其燃烧特性和燃烧动力学。结果表明：随着谷壳糠粉粒径的减小,其最低着火温度（MIT）和爆炸下限浓度（LEL）降低,但最大爆炸压力P和爆炸压力上升速率均增大。其中粒径为80～96μm样品的爆炸压力为0.9MPa,其粉尘层（5mm及10mm）和粉尘云最低着火温度分别为130℃和430℃,燃烧特性指数S_N达到3.82×10^-7,较粒径为180～1250μm样品提高了57.2%;在307s出现最大释热峰,且最大释热峰值强度增加至62kJ/m²,对应热解过程的反应活化能由35.35kJ/mol（180～1250μm样品）增大至51.15kJ/mol,表明其燃烧过程随粒径的减小由扩散控制转变为动力学控制过程。     

Generation of Submicron Arizona Test Dust Aerosol: Chemical and Hygroscopic Properties

This article describes a submicron dust aerosol generation system based on a commercially available dust disperser intended for use in laboratory studies of heterogeneous gas–aerosol interactions. Mineral dust particles are resuspended from Arizona Test Dust (ATD) powder as a case study. The system output in terms of number and surface area is adjustable and stable enough for aerosol flow reactor studies. Particles produced are in the 30–1000 nm size range with a lognormal shape of the number size distribution. The particles are characterized with respect to morphology, electrical properties, hygroscopic properties, and chemical composition. Submicron particle elemental composition is found to be similar for the particle surface and bulk as revealed by X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma optical emission spectroscopy (ICP-OES), respectively. A significant difference in chemical composition is found between the submicron aerosol and the ATD bulk powder from which it was generated. The anionic composition of the water-soluble fraction of this dust sample is dominated by sulfate. Resuspended dust particles show, as expected, nonhygroscopic behavior in a humid environment. Small hygroscopic growth of about 1% (relative change in mobility diameter) was observed for 100 nm particles when the relative humidity (RH) was changed from 12 to 94%. Particles larger than 100–200 nm shrank about 1% once exposed to RH > 90%. This was interpreted as a restructuring of the larger agglomerates of dust to particles of smaller mobility diameter, under the influence of water vapor.     

Characteristics and pozzolanic reactivity of glass powders

This paper deals with the morphology, fineness and pozzolanic activity of four glass powders: one (GP-fine) from the screening of crushed waste glasses, one (GP-dust) from a dust collector for the glass crushing process and two (GP-4000 and GP-6000) from further grinding of the powder from the dust collector in a ball mill. GP-fine and GP-dust consist mainly of large flaky particles, while GP-4000 and GP-6000 consist mainly of small angular particles. The finenesses of these glass powders are measured by particle size distribution and Blaine fineness method. For a similar particle size distribution, ground glass powder has a higher Blaine specific surface area than Portland cement due to the angular morphology of glass particles. Finely ground glass powders exhibited very high pozzolanic activity. The finer the glass powder is, the higher its pozzolanic reactivity is. An increase in curing temperature accelerates the activation of pozzolanic reactivity of both glass powder and coal fly ash in terms of strength development rate. Mortar cube strength results (ASTM C109) indicated that curing temperature has a greater influence on the glass powder than on fly ash. The rapid mortar bar expansion test (ASTM C1260) results indicate that the replacement of Portland cement with ground glass powder also reduces the expansion due to alkali-aggregate reactions, although it is not as effective as coal fly ash.     

Nanoencapsulation mechanism of fragrant oil: effect of formaldehyde − melamine molar ratio

Encapsulation of essential oils by in situ polymerization is commonly used to contain the oil and thus ensure its controlled release. Melamine resin formaldehyde is one of the most widely used shell materials due to its thermal and chemical stability. One of the factors that influences the properties of the capsules is the molar relationship between monomers. The effect of formaldehyde ? melamine (F/M) molar ratios 3, 4 and 6 on the nanoencapsulation, morphology and properties of nanocapsules was investigated. The morphology and particle size were investigated by the scanning electron microscopy and atomic force microscopy techniques. The composition of the formaldehyde ? melamine resins was determined by Fourier transform infrared spectroscopy, and the thermal stability of the nanocapsules was analysed by differential scanning calorimetry and thermogravimetric analysis. Increasing the formaldehyde content reduced the nanocapsules' chemical stability. The capsule sizes obtained were nanometric at all melamine ? formaldehyde ratios studied, with a non‐significant variation in particle size and shape. © 2017 Society of Chemical Industry     

Staubarme Pulver durch Sprühtrocknen – Erfahrungen mit neueren Techniken

Dustless powders by spray drying – Experience with new techniques . Old drying plant with rotary- or nozzle-atomizer of conventional construction produce more or less fine, dusty powder. Increasingly, there is a demand for dustless powders. A knowledge of the parameters which influence the size of the particles and the experience gained in the drying of various products was the basis for the evolution of a new spray dryer capable of producing even dustless powder. Many trials in this new spray dryer, called the FSD (Fluidized Spray Dryer) show that the powder meets all requirements. Moreover, this spray dryer will save energy and is more gently to the product by working at lower outlet temperatures.     

Einfluss von Mahlhilfsmitteln auf die Staubungsneigung

Depending on the way respective materials are handled in different processes, particles can be released from bulk materials. Being mostly undesirable, this release of particles can represent a health risk to humans and a hazard to the environment. Therefore, dust formation tendency represents an important material property and depends on the respective type of stress. Using the rotating‐drum method and the single‐drop method, the dust formation tendency and the influence by grinding aids is examined. The obtained results show that the dust formation tendency of bulk materials can be considerably increased by the addition of grinding aids.     

Zur Produktgestaltung kohäsiver Pulver – Mechanische Eigenschaften,Kompressions‐ und Fließverhalten

Product Design of Cohesive Powders – Mechanical Properties, Compression and Flow Behavior The three yield conditions of a powder continuum (incipient yield, stationary flow, consolidation) are formulated on basis of particle mechanics by the model ?stiff particles with soft contacts“. So that the direct influence of contact behaviour on flow behaviour is analytically shown. The powder compression behaviour is characterised by a compressibility index. Additionally the compression rate and the specific compression work are explained. So that the correlation between contact compliance, adhesion force intensification and powder flowability can be physically consistent evaluated. The response functions of extreme stressing and flow conditions at material conversion processes, storage and transport can be sufficiently described by these models. Obviously, suitable conclusions may be also drawn to design marketable products of processing industries.     

Dust Generator for Inhalation Studies with Limited Amounts of Archived Particulate Matter

A novel design for a dry-aerosol generator that efficiently produces a well-dispersed dust suspension using small quantities of a PM_2.5-enriched powder sample is described. The motivation to develop a highly efficient dry-aerosol particle generator was to facilitate collaborative projects that combine in vitro cell culture experiments and multiday inhalation exposures using a single batch of well-characterized particles. Premixing of the test particles with larger diameter glass beads permits delivery of aerosol concentrations from 100–1000 μ g/m³ to an exposure chamber using only milligram quantities of the test powder per hour. Examination of exposure chamber filter samples by scanning electron microscopy showed well-dispersed particles of the test powder free of glass spheres or fragments. Data are presented from experiments using coal fly ash as the test powder to illustrate the system performance.     

焦粉成型造气技术应用

介绍了焦粉成型技术及其在造气工艺生产中的应用情况,实践证明,将焦化厂的廉价焦粉成型,用于掺烧制气,其焦粉成型率为95.18%,半水煤气成分满足工艺指标,1.18t成型焦粉可替代1t焦粒,炉底及上行集尘器下灰量增多,且经济上年可降成本158万元。     

Sintering of caustic magnesite dust over the length of a rotary kiln

Conclusions The intensive formation of the pellets (granules) of caustic magnesite dust commences from the moment of completion of the decarbonization of the particles of raw magnesite. The development of pellets is established at a distance of 29 m from the charging end of the kiln.The formation of grains and their densification and reinforcement occur in the section 29–45 m of the length of the kiln as a result of the compaction of the particles of caustic dust.The recrystallization of the periclase, sintering, and agglomeration of the powder occur mainly in the section 45–75 m of the furnace length in the presence of melt.During the burning in a 90-m rotary kiln of unground caustic magnesite dust, the apparent porosity of the powder resulting from its grains diminishes from 50–60 to 24%.Translated from Ogneupory, No. 8, pp. 52–55, August, 1971.     

Thermal analysis of high‐performance mortar containing burnt clay shale as a partial portland cement replacement in the temperature range up to 1000 °C

Clay shale is a specific type of material that contains a large amount of kaolinite. Burnt clay shale belongs to a large group of pozzolans, and its pozzolanic properties are activated after burning at temperatures similar to those when kaolinite is transformed into metakaolin. In this study, fine powder of burnt clay shale was used for the design of a high‐performance mortar as a partial replacement for portland cement up to 60 wt.%. The prepared specimens were subjected to a thermal analysis by using differential scanning calorimetry, thermogravimetry, and thermodilatometry. The investigation was performed in the temperature range 25–1000 °C. The basic physical and mechanical properties were studied as well. It was demonstrated that it is possible to design and produce a high‐performance mortar containing fine burnt clay shale powder and that an appropriate amount of this replacement is up to 20 wt.%. Copyright © 2016 John Wiley & Sons, Ltd.     

炭粒床高效工业除尘装置的设计与开发

The new dust removal technical route using the carbon-granular bed filter, packed of carbon particles with appropriate grade derive from an online-process vibration sieve, to replace the traditional baggy filter had been developed successfully for capturing the micro-carbon dusts produced from pulverization of petroleum coke,and the green close loop of carbon materials is thus completed in the combined pulverizing and classifying system and pulverized carbon dust removal process. The high dust removal efficiency greater than 99%, low outlet dust concentration less than 100 mg-m-S, low pressure drop through dust filtration chamber less than 980 Pa, simple and easy design, and flexible and stable operation were achieved also with the carbon-granular bed filter in both bench and industrial scale operations.     

Influence of Aggregates in α‐Al2O3 Slurry on Orientation Degree of Powder Compact Fabricated by Magnetic Forming Method

The crystallographic orientation of α‐Al₂O₃ powder compact under a magnetic field is affected by the presence of aggregates. In this work, the influence of aggregates on the orientation degree was studied from the experimental and theoretical viewpoints. The optical parameter of birefringence was used as an evaluation index for the crystallographic orientation of α‐Al₂O₃ compact samples. The effect of aggregates on the orientation degree was estimated from the simulation of the distribution of the relative angles between the crystal axes of primary particles for any constituting number of aggregates. The orientation of an aggregate depends on the apparent crystal axes calculated from the vector summation of the crystal axes for all constituting particles. The measured degree of orientation of the powder compact was consistent with the theoretical values for all powder compact samples containing various concentrations and constituting numbers of aggregates. The elimination of aggregates is the key for good particle alignment under a magnetic field.     

Release of highly hydrophilic drugs from poly(ϵ‐caprolactone) matrices

We examine the release of two highly hydrophilic drugs, nicotine and caffeine, from poly(ε‐caprolactone) (PCL) matrices. We find that the dominant mechanism for drug release is drug diffusion through the PCL matrices. As a result, the rate of drug release (defined by the amount of drug released per unit time) decreases exponentially with time. Coating the drug‐carrying particles with a drug‐free PCL layer significantly changes the release profile: instead of exponential decay, the release rate exhibits a peak whose location (time) and magnitude vary with the diffusion coefficient of the drug in the polymer and the thickness of the coating. As a result, coating may be used to control the release rate andobtain a relatively constant rate over a period of time. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Adsorption and drug release based on β‐cyclodextrin‐grafted hydroxyapatite composite

In this study, β‐cyclodextrin (β‐CD) was covalently grafted on hydroxyapatite (HA) using a coupling agent to improve the drug loading capacity and prolong the drug release. The binding of β‐CD on the HA surface was confirmed by Fourier transformation infrared spectroscopy, thermal gravimetric analysis, and X‐ray powder diffraction. The adsorption capacity of ofloxacin on β‐CD‐grafted hydroxyapatite (β‐CD‐g‐HA) composite was found to be 30 mg g^?1 at 37°C and 24 h. The adsorption process is spontaneous, given the negative values of free energy change. Compared with the release of ofloxacin loaded on HA, the release of ofloxacin loaded on β‐CD‐g‐HA was slowed down 28% and 21% in pH 2.0 and pH 7.4 buffer media at 2 h, respectively. Biocompatibility of β‐CD‐g‐HA was assessed by MTT assay, and the result showed that it had no cytotoxicity. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Application of taylor dispersion technique to measure mutual diffusion coefficient in hexane + bitumen system

A novel approach with fewer technical and analytic limitations in liquid solvent‐bitumen diffusion studies is used in this article. The Taylor dispersion technique was selected for its convenient short run time experiments and reliable data analysis to find mutual diffusion coefficients in a hexane + bitumen mixture. For the first time, the infinite‐dilution molecular diffusion coefficients of bitumen in hexane were measured in both the presence and relative absence of asphaltene particles in the solution at atmospheric pressure and temperatures of 303.15, 310.15, and 317.15 K. The polydisperse nature of bitumen was clearly revealed. Results were compared with common predictive tools. Also, the asphaltene surface charge in the hexane precipitating solvent was demonstrated. Through concentration dependency investigations at atmospheric pressure and 303.15 K, it was determined that the mutual diffusion coefficients monotonically decrease as the viscosity of mixture increases within the studied 0–34% volumetric concentration of bitumen. The Taylor dispersion technique shows great potential for diffusion studies of liquid solvent‐bitumen systems. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2670–2682, 2014