Spray performance and steadiness of an effervescent atomizer and an air-core-liquid-ring atomizer for application in spray drying processes of highly concentrated feeds

Wittner, Marc O.; Karbstein, Heike P.; Gaukel, Volker

doi:10.1016/j.cep.2018.04.017

Cited by 20 publications

(30 citation statements)

References 19 publications

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“…The correction method for spray droplet size distributions, presented in Section 3, will be applied to published droplet size measurements, generated by an ACLR atomizer [14]. For clarity, the used model system, spray test rig, and atomizer are described in the following sections.…”

Section: Methodsmentioning

confidence: 99%

“…Values of µ, given in Table 1, are measured at a shear rate of 1000 s −1 . For further information on model system characterization please refer to Wittner et al [14]. Table 1.…”

Section: Model Systemmentioning

confidence: 99%

“…Table 1. Physical properties of test solutions at 25 • C: viscosity (µ), surface tension (σ), density ( ), and refractive index (RI), as well as the corresponding uncertainty values u r (x) [14]. Concentrations of total dry matter c total , Maltodextrin (c MD ), and WPC 80 (c WPC 80 ) are given as dry base values (d.b.)…”

Section: Model Systemmentioning

confidence: 99%

“…The mixing chamber length (l mixing chamber ) is 2.4 mm. This atomizer geometry was used previously by Stähle et al [15,16], Kleinhans et al [17,18], and Wittner et al [14]. A scheme of the used ACLR atomizer is given in Figure 1.…”

Section: Air-core-liquid-ring (Aclr) Atomizermentioning

confidence: 99%

“…With this approach, contributions of real and apparent droplets can clearly be separated and the characteristic value x 90,3 can be determined without a systematic overestimation of large droplets. The new method is applied to previously published laser diffraction measurements of spray droplets, generated by a continuously working Air-Core-Liquid-Ring (ACLR) atomizer [14], which have until now solely been analyzed using the resulting x 1,2 values. Results of the new correction method are compared to those corrected by detector deactivation and values of measurements without correction.…”

Section: Introductionmentioning

confidence: 99%

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Pneumatic Atomization: Beam-Steering Correction in Laser Diffraction Measurements of Spray Droplet Size Distributions

2018

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Laser diffraction is among the most widely used methods for spray droplet size measurements. However, the so-called beam-steering effect must be considered when pneumatic atomizers are used for droplet generation. The beam-steering effect is a systematic measurement error, leading to the detection of apparent large spray droplets due to gradients in the refractive index of the gas phase. The established correction method is based on the reduction of the laser diffraction system’s measurement range by deactivation of detectors, relevant for the detection of large droplets. As this method is only applicable when size ranges of real and apparent droplet sizes are clearly different, an alternative method for beam-steering correction is introduced in the presented study. It is based on a multimodal log-normal fit of measured spray droplet sizes. The modality representing the largest droplets is correlated to the beam-steering effect and therefore excluded from the measured size distribution. The new method was successfully applied to previously published droplet size distribution measurements of an internal mixing Air-Core-Liquid-Ring (ACLR) atomizer. In measurements where the method of detector deactivation is applicable, excellent accordance of droplet size distributions, gained by both correction methods, was found. In measurements with overlapping real and apparent parts of the distribution, the new correction method led to a significant reduction of overestimated large droplets. As a consequence, we conclude that the new method presented here for beam-steering correction should be applied in laser diffraction measurements of spray droplet sizes, generated by pneumatic atomizers.

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Section: Methodsmentioning

confidence: 99%

“…Values of µ, given in Table 1, are measured at a shear rate of 1000 s −1 . For further information on model system characterization please refer to Wittner et al [14]. Table 1.…”

Section: Model Systemmentioning

confidence: 99%

Section: Model Systemmentioning

confidence: 99%

Section: Air-core-liquid-ring (Aclr) Atomizermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Pneumatic Atomization: Beam-Steering Correction in Laser Diffraction Measurements of Spray Droplet Size Distributions

2018

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Spray drying encapsulation of essential oils: Insights on various factors affecting the physicochemical properties of the microcapsules

Phanse,

Chandra

2024

Flavour & Fragrance J

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Spray drying is a process that involves instantaneous conversion of a liquid or slurry into a free‐flowing powder in the presence of hot air or nitrogen gas current in a drying chamber. The technique is usually used to encapsulate active molecules like essential oils, plant extracts, fragrances, flavours and enzymes within a wall material. The encapsulation provides chemical and physical stability to the actives by converting them into free‐flowing powders which prevents their susceptibility to external atmospheric conditions like temperature, humidity, UV exposure and chemical oxidation. Spray drying encapsulation has an edge over other encapsulation techniques because it is fast, simple, efficient and economically feasible. The article focuses on encapsulating various essential oils within natural polymers and emulsifiers by spray drying methods to form stable microcapsules. The review also provides information on different types of spray drying equipment and process parameters like the type of atomiszer and nozzles, inlet–outlet temperature and type of cyclones. All the process parameters and materials are found to influence the physicochemical properties of the microencapsulates of essential oils. The review also discusses the effects of process parameters and materials on the encapsulation efficiency, moisture content, bulk and tapped density, agglomeration properties and thermal stability of the microencapsulates. Thus, the consolidated review will provide an overview of various optimization parameters and governing factors for obtaining microencapsulates of essential oils.

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Time-Averaged Analysis and Numerical Modelling of the Behavior of the Multiphase Flow and Liquid Lamella Thickness Inside an Internal-Mixing ACLR Nozzle

Martínez

Gaukel

2023

Flow Turbulence Combust

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The Air-Core-Liquid-Ring (ACLR) atomizer is an innovative internal-mixing pneumatic atomization technique, suitable for energy-efficient spray drying of highly viscous liquid feeds, with high solid contents. However, pneumatic atomizers such as the ACLR can suffer from unstable internal flow conditions, which may lead to a wide variation in the droplet diameter obtained. Therefore, the internal flow conditions of an ACLR-atomizer needs to be properly studied and comprehended. With that in mind, a computational fluid dynamic (CFD) model was implemented and tested with experimental data collected for different air pressures and liquid feed viscosities. The model used can predict average lamella thickness with a relative error of less than 10%, when compared to experimental results, although some degree of artificial dampening of the flow instabilities occurs at high viscosities and low pressures. These instabilities have to be investigated in more detail from both the numerical side, by further refining the CFD model to capture the moment-to-moment behavior of the flow, as well as on the experimental side, by studying the instability development at higher recording speeds.

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Spray performance and steadiness of an effervescent atomizer and an air-core-liquid-ring atomizer for application in spray drying processes of highly concentrated feeds

Cited by 20 publications

References 19 publications

Pneumatic Atomization: Beam-Steering Correction in Laser Diffraction Measurements of Spray Droplet Size Distributions

Pneumatic Atomization: Beam-Steering Correction in Laser Diffraction Measurements of Spray Droplet Size Distributions

Spray drying encapsulation of essential oils: Insights on various factors affecting the physicochemical properties of the microcapsules

Time-Averaged Analysis and Numerical Modelling of the Behavior of the Multiphase Flow and Liquid Lamella Thickness Inside an Internal-Mixing ACLR Nozzle

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