Simultaneous particulate design of primary and agglomerated crystals of steroid by spherical agglomeration in liquid for dry powder inhalation

Spherical agglomerates of steroid KSR-592, consisting of fine primary drug crystals suitable for dry powder inhalation (DPI), were prepared by the spherical agglomeration method in liquid with a bridging liquid. It was found that the particle size of primary crystals increased until the dispersing medium was saturated with the bridging liquid, whereas the spherical agglomeration of primary crystals was continued even after the saturation of medium with the bridging liquid. The growth rates of primary crystals and agglomerates increased with an increase in the temperature and/or a reduction in the agitation speed of the system. The agglomerates were easily disintegrated into the primary crystals depositing ideally on carrier lactose particles for DPI by mixing. The in vitro efficiency of the mixed system of lactose and disintegrated primary crystals of drug was 2 to 3 times higher than that of crystals prepared conventionally. Furthermore, the soft agglomerates disintegrated easily into respirable particles in air stream when emitted from the inhalation device were prepared by reducing the agitation speed after the dispersing medium was saturated with the bridging liquid.     

碱洗氧化工艺中杂质对硫酸钠结晶粒度的影响

针对碱洗氧化工艺脱硫废水中硫酸钠的蒸发结晶,设计开发了硫酸钠蒸发结晶放大实验装置,重点研究了废水中碳酸钠、铁离子和亚硫酸钠杂质对硫酸钠蒸发结晶晶体粒度的影响。结果表明：1.0%（质量分数）的碳酸钠对硫酸钠晶体的粒径影响可忽略;铁以沉淀物形式存在时,易引起硫酸钠晶体结块且粒径变小; 铁以溶解形式存在时,对硫酸钠晶体的粒径影响较小;亚硫酸钠的存在易引起硫酸钠晶体的粒径变小,氧化消除溶液中的亚硫酸钠后,结晶得到的硫酸钠晶体粒径变大。工业装置经过改造后,无水Na₂SO₄产品的平均粒径由106.71 μm提高至129.99 μm。     

Experimental study and modeling of fluidized bed coating and agglomeration

This work deals with the fluidized bed coating and agglomeration of solid particles. The effect of particle size on coating criteria was investigated using sand particles as the coating support and aqueous solutions containing NaCl as coating liquid. The results showed that both growth rate and efficiency increase with decreasing the particle size. The growth was mainly governed by layering for particles larger than 200 μm, whereas for finer particles it occurred by agglomeration. As the particle size became less than 90 μm, the coating operation led to uncontrolled growth and bed quenching. However, the coating of the same particles was successfully achieved by adding some coarser particles. In addition, a mathematical model based on the population balance concept, taking into account the simultaneous growth by layering and agglomeration, was established to predict the time evolution of the particle size distribution. The comparison between experimental and calculated data permitted the establishment of a law for the size dependency of the agglomeration kernel.     

Dielectric and pyroelectric properties of triglycine sulphate-polystyrene composites

A composite of Triglycine sulphate (TGS) and polystyrene has been fabricated by mixing different particle size TGS powders (75 μm to 400 μm) and polystyrene solution. The dielectric constant has been measured in the frequency range 0.1 to 100 KHz, and the pyroelectric current measurements were made by the Byer and Roundy direct method. Specific heat of the composite was determined by the differential them analysis (DTA) technique.

Particle size dependance of dielectric constant, pyroelectric coefficient and responsivity have been studied. Anomalies in ε' and P_y were observed even in the composite with the lowest particle size of TGS (75 μm). The surface effects have much greater influence on electrical properties but thermal properties are, not affected. This is indicated by a decrease in ε' and P^y with decreasing particle size of TGS, while specific heat of composite is almost independent of particle size.     

Mechanisms of aerosol deposition in a nasal model

Total and regional aerosol deposition were investigated in a model of a normal human nasal airway. Contributions of fluid turbulence and particle inertia were evaluated using monodisperse aerosols. At fixed turbulent flow conditions, deposition percentage increased with particle size greater than 1 μm, suggesting that turbulent inertial deposition is a primary mechanism.

With same size aerosol, deposition increased with increasing fluid turbulence but its contribution was less with larger size aerosol. Turbulent diffusion was the dominant transport mechanism for particles less than 1 μm, where deposition decreased with particle size. Two major deposition sites were visualized with radio-aerosol in the anterior region of the nasal airway. One is close to the ostium internum where turbulent eddies are well developed, and the other is the anterior region of the middle turbinate where direction of airflow changes from upward to horizontal.     

Oil agglomeration of a lignite treated with microwave energy: Effect of particle size and bridging oil

Oil agglomeration of Sivas–Divriği (S–D) Uluçayır lignite fines was carried out using kerosene and kerosene–extract oil (which was obtained from lignite treated with microwave energy) mixture as a bridging oil. The effects of parameters such as the amount and type of bridging oil, microwave time and particle size on the agglomeration performance were investigated. The amount of kerosene was varied from 5 to 30 wt.% of the initial lignite loading. The values of the grade and recovery increased with an increase in the amount of kerosene added. Extract oil fraction of the lignite extract at various ratios in kerosene increased the agglomeration recovery from 95.88% to 98.55%. The effect of microwave time was investigated and it was found that the grade was also increased with increasing microwave time (4, 8 and 10 min). The grade of char (microwave time: 8 min) was increased in comparison with the original lignite while decreasing its recovery. Dense medium separations of the lignite were conducted and the results of their grade recovery performances were compared with those of agglomeration of the particles. During the inspection of particle size effect on the dense medium separation, the recovery was increased remarkably (from 12.07% to 89.50%) with increasing particle size, while decreasing the grade (from 0.732 to 0.697). In the oil agglomeration of lignite the recovery values were increased with increasing particle size.     

Oil agglomeration of a lignite treated with microwave energy: Effect of particle size and bridging oil

Oil agglomeration of Sivas–Divriği (S–D) Uluçayır lignite fines was carried out using kerosene and kerosene–extract oil (which was obtained from lignite treated with microwave energy) mixture as a bridging oil. The effects of parameters such as the amount and type of bridging oil, microwave time and particle size on the agglomeration performance were investigated. The amount of kerosene was varied from 5 to 30 wt.% of the initial lignite loading. The values of the grade and recovery increased with an increase in the amount of kerosene added. Extract oil fraction of the lignite extract at various ratios in kerosene increased the agglomeration recovery from 95.88% to 98.55%. The effect of microwave time was investigated and it was found that the grade was also increased with increasing microwave time (4, 8 and 10 min). The grade of char (microwave time: 8 min) was increased in comparison with the original lignite while decreasing its recovery. Dense medium separations of the lignite were conducted and the results of their grade recovery performances were compared with those of agglomeration of the particles. During the inspection of particle size effect on the dense medium separation, the recovery was increased remarkably (from 12.07% to 89.50%) with increasing particle size, while decreasing the grade (from 0.732 to 0.697). In the oil agglomeration of lignite the recovery values were increased with increasing particle size.     

Measurements of the total and regional deposition of inhaled particles in the human respiratory tract

The total and regional deposition of monodisperse aerosols in the human respiratory tract has been measured in 12 healthy subjects breathing through the mouth. Radioactively labelled polystyrene particles in the aerodynamic diameter range 3.5–10.0 μm were employed. The total deposition results are similar to those reported by Stahlhofen et al. (1980), showing only a slight progressive increase with particle size, from a mean fraction of 0.79 of the inhaled aerosol at 3.5 μm, to 0.88 for 10 μm particles. The extrathoracic airways show a very marked deposition at all sizes, predominantly in the throat. The throat values rise rapidly from a mean of 0.09 at 3.5 μm to 0.36 at 10 μm particle diameter. Two intrathoracic fractions were also obtained by the widely accepted method of measuring the relative amounts of activity cleared from the thorax as a function of time. Alveolar deposition was apparently still some 0.06 of the inhaled aerosol at 10 μm particle diameter. Tracheo-bronchial deposition showed little change at any particle size except at 3.5 μm, when it was 0.24 of the inhaled aerosol.     

煅烧白云石粉制备微纳米级圆片状氢氧化镁

以白云石为原料,通过氨法制备出高纯度（99.30%）圆片状的阻燃型微纳米级氢氧化镁。探究了反应温度、通氨速率、氨镁物质的量比对氢氧化镁分散性和形貌的影响,确定最佳工艺条件：反应温度为80 ℃、通氨速率为150 mL/min、氨镁物质的量比为23∶1。用扫描电镜、透射电子显微镜、X射线衍射仪、激光粒度分析仪、热重分析仪和白度仪表征产品的形貌、结构、粒度及稳定性。结果表明制得的圆片状微纳米级氢氧化镁的分散性好、晶型完整、粒度均匀,D₅₀为2.493 μm、D₉₀为6.132 μm、直径约为5.7 μm、厚度约为0.7 μm、长厚比约为8∶1。稳定性好、灼烧失量为31.03%、白度为97.4,高于工业氢氧化镁行业标准。     

Breakage of wet flexible fiber agglomerates impacting a plane

The breakage of an agglomerate of wet flexible fibers impacting a plane is computationally investigated in this work using the discrete element method. In the agglomerate, the fibers stick together due to cohesive liquid bridge forces. Agglomerate breakage with various impact conditions, initial configurations, fiber properties, and liquid bridge properties is systematically investigated. The degree of breakage is governed by the impact energy, the cohesion energy due to liquid bridges, the energy dissipation/absorption through fiber–fiber contacts and fiber deformation, and the efficiency of force transmission within the agglomerate. More specifically, breakage is promoted by increasing impact velocity, decreasing agglomerate size, increasing initial compaction, increasing fiber bending modulus, decreasing liquid surface tension, and decreasing liquid-to-solid volume ratio. Breakage is strongly dependent on the modified Weber number, that is, the ratio of the Weber number to a dimensionless rupture distance, which is a measure of the impact energy relative to the cohesion energy.     

BACK MIXING AND LIQUID HOLD-UP IN A COCURRENT UP-FLOW PACKED BED BIOREACTOR

The hydrodynamics of an up-flow three phase packed bed bioreactor were investigated experimentally using tracer techniques. The effects of the liquid and gas velocities, and the particle size on the Peclet number (Pe) and on the liquid hold-up (ε_L) were determined. While the range of gas and liquid flow rate were chosen according to biotic conditions. It was found that the Pe was not influenced from liquid flow rate, however decreased with increasing gas flow rate and particle/reactor diameter ratio (d_p/D_c). Also, it was found that liquid hold-up was not influenced from gas flow rate, however increased with increasing liquid flow rate and decreased with increasing d_p/D_c ratio. The correlation which connected the Bodenstein number to gas phase particle Reynolds number and d_p/D_c ratio and the correlation which connected the liquid hold-up, liquid phase particle Reynolds number and d_p/D_c ratio were found using Marquardt-Levenberg approach.     

Experimental filtration efficiencies for large pore nuclepore filters

Experimental filtration data were collected in an effort to validate an impaction model previously developed and presented. Using a sampler with a 9.5 μm pore diameter Nuclepore filter, collection efficiencies were measured for both liquid and solid aerosols over a size range of 2–9 μm. Data for the liquid aerosol showed good agreement with the impaction model; however, data for the solid aerosol indicated an appreciably lower collection efficiency than predicted by the model. The liquid aerosol data validate the impaction model. The solid aerosol data indicate particle bounce or reintrainment subsequent to impact and underscore particle capture as a problem to be dealt with if the Nuclepore surface is to be used as a size selective filter.     

Rheological propertis of coal—oil mixture fuels

The rheological properties of coal—oil mixtures (COM) of a bituminous coal in four types of oil, grade 2, grade 4, light grade 6 and heavy grade 6, have been studied. Variables investigated were the coal concentration (0 – 60 wt.%), coal particle size (10 < d₅₀ < 40 μm), temperature (25 – 90 °C) and time effects (0 – 6 days).

Rheograms were obtained using the Ferranti-Shirley cone and plate viscometer. The COM was classified as a Newtonian fluid at coal concentrations up to 30 wt.% and as a Bingham plastic at higher values. The relative viscosity was found to increase rapidly with coal concentration, reaching 100 for a 60 wt.% of COM.

Both COM viscosity and yield stress decrease with increasing median particle size and decreasing slope of the particle size distribution. This effect is stronger at high solids concentrations.

The COM viscosity is much less sensitive to temperature than the base oil. The COM yield stress increases up to 350 Pa with increasing coal concentration, decreasing temperature and ageing.     

Hydrodynamic behavior of a liquid-solid fluidized-bed reactor for the bioconversion of coal particles to liquid products

A predictive mathematical model based on particle convection and dispersion is presented for a liquid fluidized bed of coal particles. The numerical representation can follow transient behavior of liquid fluidized beds that contain a defined particle-size distribution. The calculations exhibited excellent agreement when compared to experimental transient pressure-drop data from a column containing particles of Illinois No. 6 bituminous coal in the size range of 20–120 μm. In addition, the model was used to simulate the effect of periodic (hourly) liquid velocity step changes on elutriation of small particles from a given particle-size distribution of 34.5–75.5 μm. For the situation tested, the calculations indicate that (a) the column does not reach a steady state between velocity changes and (b) that higher initial particle elutriation rates decay to lower values until no more particles elutriate from the column.     

Drop properties and pressure fluctuations in liquid–liquid–solid fluidized-bed reactors

Characteristics of size, rising velocity and distribution of liquid drops were investigated in an immiscible liquid–liquid–solid fluidized-bed reactor whose diameter was 0.102 and 2.5 m in height. In addition, pressure fluctuations were measured and analyzed by adopting the theory of chaos, to discuss the relation between the properties of liquid drops and the resultant flow behavior of three (liquid–liquid–solid) phase in the reactor. Effects of velocities of dispersed (0–0.04 m s⁻¹) and continuous (0.02–0.14 m s⁻¹) liquid phases and fluidized particle size (1, 2.1, 3 or 6 mm) on the liquid drop properties and pressure fluctuations in the reactor were determined. The resultant flow behavior of liquid drops became more irregular and complicated with increasing the velocity of dispersed or continuous liquid phase, but less complicated with increasing fluidized particle size, in the beds of 1.0 or 2.1 mm glass beads. In the beds of 3.0 or 6.0 mm glass beads, the effects of continuous phase velocity was marginal. The resultant flow behavior of liquid drops was dependent strongly upon the drop size and its distribution. The drop size increased with increasing dispersed phase velocity, but decreased with increasing particle size. The drop size tended to increase with approaching to the center or increasing the height from the distributor. The size and rising velocity of liquid drops and correlation dimension of pressure fluctuations have been well correlated in terms of operating variables.     

THE EFFECT OF TIME, TEMPERATURE AND PARTICLE SIZE ON SUBMICRON PARTICLE REMOVAL USING ULTRASONIC CLEANING

Ultrasonic cleaning is an established method for removing micron-size particles or larger from hard substrates. This paper presents the effect of the ultrasonic frequency and time functions on submicron particle removal effectiveness. The effect of the particle size, concentration and the cleaning liquid temperature is also investigated. The removal efficiency is shown to be dependent on the ultrasonic time and frequency functions. The liquid temperature is shown to have a major effect on the ultrasonic cleaning process. The removal efficiency is shown to decrease with decreasing particle diameter. The results show that the ultrasonic cleaning technique can effectively remove particles of sizes 0.3 μm and larger.     

Cleaning of fine coals by dense-medium hydrocyclone

The efficiency of separation for fine coal in a 150 mm dia. dense-medium hydrocyclone has been determined. The partition curves have been measured for particles in the size ranges −500 μm +425 μm, −300 μm +250 μm, −150 μm +125 μm and −90 μm +75 μm. The cut point for separation increases with a decrease in particle size and the efficiency of separation decreases as particle size decreases. The cut point of separation varies with medium specific gravity but the efficiency of separation does not. Neither the cut point of separation nor the efficiency of separation is greatly influenced by the cyclone feed rate, provided that overloading does not occur.

The results lead to an accurate predictive model for the calculation of the partition curve as a function of coal particle size and medium specific gravity. The model allows the prediction of the performance of a dense-medium hydrocyclone for the washing of fine coal having arbitrary washability characteristics and particle size distribution. The model is used to demonstrate that a two-stage dense-medium hydrocyclone configuration can significantly improve the cleaning performance for a coal that has good ash-liberation characteristics. However, multi-stage dense-medium hydrocyclones do not offer any real performance advantages for coal that has poor ash-liberation characteristics.     

Influence of solid loading and particle size distribution on the porosity development of green alumina ceramic mouldings

Alumina ceramic mouldings with different solid contents ranging from 55 to 70 vol% and different ratios of coarse/fine powders, i.e. 0.4 μm (fine) and 3 μm (coarse), respectively, were prepared by compression moulding at 75 °C under a compressive stress of 10 MPa. The porous parameters, such as porosity, pore size and pore size distribution, of the green compacts were evaluated after removal of organic vehicles. Experimental evidence showed that the green density, as well as the sintered density, of the moulded alumina increased linearly with increased solid loading to an optimum of 65 vol% and decreased roughly linearly with increased coarse/fine ratio. Further increase in solid loading reduced particle packing efficiency, resulting in lower green and fired densities. No considerable improvement in green and sintered density of the moulded alumina was achieved by adjusting the coarse/fine ratio, which is due to the fact that coarse particles suppress the driving force of densification. The green compacts generally showed a bimodal pore size distribution character which may be the most important factor in dominating the densification of the powder compacts. The peak frequency at larger pore region is approximately 20–35 μm in diameter and at the smaller pore region is ˜50–95 nm in diameter. The larger pores are believed to be due to the presence of internal voids originating from entrapped gas and are probably caused by the removal of organic vehicles.     

A data processing system for the Royco aerosol particle counter 225 and determination of the properties of the modified system

A data processing system, consisting of a peak detector, an AD-converter and a minicomputer was developed, which enables the simultaneous counting of particles with different diameters. A computer program was written to handle the output of data in groups of 1, 2, …, 1024 channels. The maximum number of particles that can be counted in a single channel (1024 mode) is 16777215. The resolving time of the system was determined from oscilloscope photographs of pulses generated by monodisperse PSL and DOP particles and amounts to about 15 μsec. The optical counter was calibrated for the size range 0.3–9 μm with monodisperse PSL and DOP aerosols. The response curve is non-singular in between 0.8 and 1.4 μm. The ratio between the standard deviation (σ_K) and the median (K_g) of the channel number distribution for monodisperse aerosols decreases continuously with increasing K_g from 0.7 (at 8) to 0.04 (at 922). Count losses due to coincidence and pulse processing were calculated. Completely ambiguous results have to be expected for concentrations higher than about 450 particle cm⁻³.     

Preparation of spherical wax matrices of sulfamethoxazole by wet spherical agglomeration technique using a CMSMPR agglomerator

Spherical wax matrices of sulfamethoxazole were prepared by a wet spherical agglomeration technique using a model continuous mixed suspension mixed product removal (CMSMPR) agglomerator to develop a practical continuous operation system. The average diameter of products increased at the initial stage of operation until reaching a maximum at 5 to 7 minutes elapsed after starting. This maximum point roughly corresponded to a half of average retention time. Thereafter the particle size decreased gradually and reached the equilibrium state. The average size of products obtained at steady state decreased on decreasing the feeding rate of bridging liquid, but increased on decreasing the agitation speed and the feeding rate of aqueous suspension. The rate of agglomeration was analysed using the concept of population balance proposed by Randolph and Sikdar. The agglomeration rate increased with increase of particle size for sizes above 200 – 300 μm. For sizes below 200 μm, the agglomeration rate was almost independent of particle size.