Liquid Agglomeration Research Articles

Liquid injection in a fluidised bed: Temperature uniformity

• Combination of Particle Image Velocity and Infra-Red Thermography. • Time-averaged temperature distribution for liquid injection in a fluidized bed. • Effect of droplet size distribution on the bed temperature uniformity. • Liquid agglomerates observed in the Infra-Red image as cold spots. • Solids motion affects the liquid distribution in the bed. Liquid injection in fluidized beds occurs in well-established industrial processes as fluid coking, spray fluidzed bed granulation and condensed mode gas-phase polymerisation. These processes still suffer performance issues due to their complex nature, where liquid injection adds even more complexity. In this work, the effect of liquid injection on the temperature uniformity in a pseudo-2D fluidized bed was studied using Infra-Red Thermography. The Infra-Red images were also studied to qualify the agglomeration behaviour. Injecting smaller droplets ( ∼ 90 μ m affects the uniformity of the bed more than injecting larger droplets ( ∼ 225 μ m. However, the formation of agglomerates increases with increasing droplet size. The injection velocity influences the average temperature of the bed more for the larger droplets. Additionally, increased solids motion was observed to reduce the agglomeration formation in the bed. Lastly, the particle temperature distribution does not reflect the presence of agglomerates and is thus unsuitable to quantify the agglomeration behaviour.

Controlling thermal-induced dewetting of As20Se80 thin films for integrated photonics applications

As the use of photonics circuits expands, the optical quality and performance of integrated components in the microscale become a major concern. Aiming to improve the performance while reducing the time processing, new microfabrication approaches are being investigated. The dewetting of glassy thin films have been recently proposed as an alternative for nano and microfabrication of chalcogenide optical components. Besides being the best materials for light transmission in the infrared region, chalcogenide glasses possess a flexible molecular structure that allows using a cheap and simple molding process. Here we investigate the thermal-induced dewetting of chalcogenide As20Se80 thin films, by studying the influence of temperature, atmosphere, and heating rate on the formation of self-assembled microstructures. We found that thin films between 150 and 700 nm dewet via structural relaxation, similarly to liquid agglomeration, and produce solid microstructures with the same composition and molecular structure as the initial film. By controlling the glass viscosity and the kinetics of the nucleation process it was possible to adjust the distribution and size of glassy microstructures. Additionally, we combine the dewetting process with standard photolithography and by avoiding the capillary instabilities, we are capable to obtain waveguides with the smooth and symmetric surfaces required for optical applications in the microscale size.

Automated Evaluation of Contact Angles in a Three-Phase System of Selective Agglomeration in Liquids

This study aims to an automated evaluation of contact angles in a three-phase system of selective agglomeration in liquids. Wetting properties, quantified by contact angles, are essential in many industries and their processes. Selective agglomeration as a three-phase system consists of a suspension liquid, a heterogeneous solid phase and an immiscible binding liquid. It offers the chance of establishing more efficient separation processes because of the shape-dependent wetting properties of fine particles (size ≤ 10 µm). In the present paper, an experimental setup for contact angle measurements of fine particles based on the Sessile Drop Method is described. Moreover, a new algorithm is discussed, which can be used to automatically compute contact angles from image data captured by a high-speed camera. The algorithm uses a marker-based watershed transform to segment the image data into regions representing the droplet, the carrier plate coated by fine particles, and the background. The main idea is a parametric modelling approach forthe time-dependent droplet’s contour by an ellipse.The results show that the development of the dynamic contact angles towards a static contact angle can be efficiently determined based on this novel technique. These findings are useful for a detailed discrimination of wetting properties of spherical and irregularly shaped particles as well as their wetting kinetics. Also, a better understanding of selective agglomeration processes will be promoted by this user-friendly method.

CFB air-blown flash pyrolysis. Part I: Engineering design and cold model performance

Abstract The objective of this work was to design, construct and test a novel circulating fluid bed fast pyrolysis reactor system for production of liquids from biomass. The novelty lies in incorporating an integral char combustor to provide autothermal operation of the reactor. A reactor design methodology was devised which correlated input parameters to process variables, namely temperature, heat transfer and gas/vapor residence time, for both the char combustor and biomass pyrolyser. From this methodology, a CFB reactor was designed with integral char combustion for 10 kg/h biomass throughput. A full-scale cold model of the CFB unit was developed and tested to derive suitable hydrodynamic relationships and performance constraints. The hot CFB reactor was constructed, its operability was tested and appropriate modifications were accomplished prior to the commissioning. A major requirement for the desired dual-mode operation of the reactor system conceived was the close coupling of the two reactor subsystems, namely the pyrolysis riser (medium temperature) and char combustor (high temperature). The basic CFB reactor design was proven effective in providing the high heat transfer rates – expressed as low voidage values in the riser and high solid circulation rates – to biomass particles in the very short vapor residence times (VRTs) required. The understanding of the complicated aspects related to two-phase gas–solids flow in the standpipe resulted in a smooth, stable transfer of solids over a wide range of operating parameters during cold CFB reactor operation. In the hot CFB unit testing, the use of two and three cyclones in series was proved insufficient to capture char and unconverted wood particles, especially during the reactor start-up phase. These problems were partially faced by adopting a configuration of a primary cyclone and inertia impinger in series, but further development is still required. A variety of configurations for the product collection system were built and tested, the most efficient being a combination of a shell-and-tube heat exchanger (condenser) and a cotton wool filter. However, the liquid recovery configuration gave rise to a number of problems, the most important being gradual plugging of the heat exchanger due to the formation of sticky solid–liquid agglomerates.

循環型社会形成に向けて分離精製技術の果たす役割

Industrial systems and daily life in Japan are shifting to a society based on recycling to reduce energy and resource consumption. To establish a society based on recycling urban resource recovery centers (mines) are important as places to reduce waste volumes, reusing and recycling valuable materials with application of mineral processing technology. The authors have reviewed applications of mineral processing in urban mines, and recent developments in common separation methods, magnetic separation, gravity separation, flotation, and agglomeration in liquid.

Reaction-bonded silicon carbide tube fabricated by continuous sintering of double-walled preform

A reaction-bonded silicon carbide radiant tube has been successfully fabricated by the continuous sintering of a double-walled preform which was composed of inner Si/C and outer SiC/C layers. Sequential centrifugal casting was employed to develop double-walled preform and process shrinkages were minimized by adjusting the particle packing characteristics with multimodal particle size distribution. Debinding behavior was optimized in a two-step process consisting of the capillary migration/surface evaporation of the thermoplastic resin and subsequent thermal pyrolysis of the thermosetting resin. Reactive infiltration of liquid silicon was carried out in vacuum, during which liquid agglomeration of the liquid silicon by surface tension was prevented by in-situ formed porous silicon carbide network structure. Uniform and rapid infiltration was achieved with double-walled preform method due to reduced infiltration distance and increased area of infiltration front.

A new spherically agglomerated drug composite system with lactose for dry powder inhalation

Abstract In order to prepare a dry powder inhalation (DPI) formulation for steroids, we designed crystal agglomerates consisting of fine drug crystals suitable for DPI that disintegrated into primary crystals in the inhalation device at emission. Using these agglomerates, we developed a new spherically agglomerated drug composite system with lactose for DPI of steroids with a Jethaler®. The drug agglomerates were prepared by the method of spherical agglomeration in liquid with control of the particle size of the primary drug crystal, agglomerates and mechanical strength of agglomerates by changing the agitation speed of the agglomeration system before (5°C-1000 r.p.m.) and after (5°C-300 r.p.m.) the dispersing medium was saturated with bridging liquid. The agglomerates in the DPI formulation disintegrated into respirable primary crystals by collision with coformulated lactose particles in the milling chamber of the device when inhaled. The DPI formulation with these agglomerates exhibited a higher fine particle (= respirable) fraction (FPF: 24.5%) than the formulation with fine drug particles (FPF: 16.1%) as evaluated in vitro with a cascade impactor. The inhalation property of the present DPI formulationwas determined by the particle size of coformulated lactose particles. It was found that 325M lactose (approximately 60 μm mean diameter) was most suitable to improve the inhalation properties of the present system.

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.

Primary crystal growth during spherical agglomeration in liquid: designing an ideal dry powder inhalation system

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 introduced to the system, whereas the spherical agglomeration of primary crystals continued even after the saturation. 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 growth of primary crystals in the spherical agglomerates was explained by a crystallization and fusion mechanism proposed by us. The primary crystals were mechanically stronger than their agglomerates so that the agglomerates were disintegrated easily into the primary crystals, which retained their original size, under the shear force generated on being mixed with carrier particles for DPI.

Penetration of Outer Layered Particles of Agglomerate into Inner Intersticies of Agglomerate during Spherical Agglomeration in Liquid.

Layering agglomeration of aluminum lake particles, i.e. a fine reddish pigment, was conducted by depositing them on a cored agglomerate of lactose prepared by the wet spherical agglomeration technique with a bridging liquid, i.e. water, in a dispersing medium, i.e. chloroform, under agitation. The layered agglomerates were spheronized and compacted during agglomeration. The processes of layering agglomeration and compaction are as described by the selective coalescence mechanism proposed by Kapur and a modified Kawakita's equation. It was newly found that the aluminium lake particles layered on the surface of a core agglomerate penetrated gradually into the inside of core agglomerates during agglomeration. The penetration behaviors of aluminum lake particles were represented by their relative movement coefficients, found by measuring their distributions in the agglomerate with a color measuring system. The mechanism of penetration of aluminum lake particles was discussed by referring to the tapping processes of aluminum lake and lactose powders in liquid and air.

液中造粒とその応用

Agglomeration in liquid is a promising method for mineral and material processing, fuel beneficiation and waste treatment. In this process, fine particles suspended in a liquid are agglomerated by addition of a second immiscible liquid (bridging liquid) which preferentially wets the particles under appropriate agitation conditions. The authors reviewed recent progress in fundamental studies of agglomeration and its application; especially, the main factors affecting the agglomeration, on-line monitoring systems and topics in industrial fields were described.

Production of Zirconia Microspheres Using a Newly Developed Semi-Continuous System of Agglomeration in Liquid.

The production of zirconia microspheres in a newly developed semi-continuous system of agglomeration in liquid was investigated. Semi-continuous agglomeration experiments were carried out using zirconia powder containing 2.6 mol% of Y2O3 (surface area=6.76m2/g, mean particle diameter=0.45μm), a paraffin type organic liquid as suspending media and four levels of bridging liquid additions, i. e. 0.095, 0.105, 0.115 and 0.125ml/g. Several runs were performed for each bridging liquid dosage. A decrease in the amount of bridging liquid prolongs agglomeration time and decreases the diameter of agglomerates. The sintered agglomerates produced by using different dosages of bridging liquid have sphericity, i. e. the ratio of the maximum length and breath diameter, ‹1.14, density› 5.93g/cm3, mean diameter of 282-701μm and narrow size distribution. The agglomeration time and properties of agglomerates obtained from several runs of the semi-continuous agglomerator exhibited good reproducibility. However, the semi-continuous agglomerator can be sensitive to even minor changes in bridging liquid dosage which affect the agglomeration time and the properties of agglomerates. Consequently, there is a great need to develop a reliable instrumentation method for on-line monitoring of the agglomeration process. Cognizant to this need, the possibility of using power consumption, temperature, pressure, laser attenuation and noise relative energy for on-line monitoring was investigated. It was concluded that on-line monitoring of the agglomerate growth during the process of agglomeration in liquid was possible by measuring the laser attenuation and noise relative energy.

The Role of Compaction in Agglomeration in Liquid and Formulation of Scale-up Equation.

The effects of agitation intensity and amount of bridging liquid on agglomerate formation in agglomeration in liquid were experimentally investigated. An increase in agitation intensity advanced the compaction of agglomerates, reduced the porosity and changed the saturation degree which is the ratio by volume of the bridging liquid to the pores of an agglomerate. It was observed that the process of agglomerate growth depended on the changes in porosity. Based on this observation, the effects of agitation intensity on the process of compaction and changes in porosity were quantitatively elucidated and a scale-up equation was formulated. In addition, model agglomerates of the zirconia powder were cold isostatically pressed to investigate the influence of green agglomerate porosity on the density of sintered agglomerates. The results showed that the agglomerates produced by agglomeration in liquid must have porosities less than 0.51 in order to achieve high density and strength after sintering. To achieve this objective, the formulated scale-up equation was utilized to design a batch-type horizontal agglomerator that can provide the agitation energy required to produce agglomerates with porosities below 0.51. The newly designed agglomerator was successfully tested in the production of highly dense microspherical agglomerates of zirconia.