Abstract
Vortex chambers introduce process gas via tangential inlet slots over the entire length of the cylindrical vortex chamber and evacuate the gas via a chimney in one of the end plates of the vortex chamber. A strong rotational flow is generated, allowing high-G operation. The latter intensifies interfacial mass, heat and momentum transfer by easily one order of magnitude and also facilitates the use of fine particles [1]. In previous studies, application to particle drying [2,3] and fine particle coating [4] was demonstrated. Applications taking advantage of the very short gas-solids contact time and combining high-G intensified gas-solids contact, gas-solids separation and solids segregation were also studied [5].
In the present work, a specific design called the radial multi-zone dryer (RMD) [6] is experimentally and numerically studied. Application to spray drying is focused on, characterized by dilute operation and very strong rotational flows. Two distinct temperature zones are created without physical barrier, a radially central zone where hot air with a temperature up to 350°C is injected and a peripheral zone where air at a temperature of around 100°C is injected through the vortex chambers (Figure 1). The proposed multi-zone operation allows significant process intensification while preventing degradation of the product. Liquid droplets are injected in the hot central zone, co- or counter-current with the hot air. Fast initial drying is achieved in this zone while burning the product is prevented by rapid evacuation of the produced particles to the colder periphery under the action of the centrifugal force generated by the vortex chamber(s). Typical residence time of the particles in the hot zone can be limited to a few milliseconds. Drying is continued in the colder periphery where high-G operation intensifies interfacial mass, heat and momentum transfer and ensures efficient gas-solids separation.
In the present work, a specific design called the radial multi-zone dryer (RMD) [6] is experimentally and numerically studied. Application to spray drying is focused on, characterized by dilute operation and very strong rotational flows. Two distinct temperature zones are created without physical barrier, a radially central zone where hot air with a temperature up to 350°C is injected and a peripheral zone where air at a temperature of around 100°C is injected through the vortex chambers (Figure 1). The proposed multi-zone operation allows significant process intensification while preventing degradation of the product. Liquid droplets are injected in the hot central zone, co- or counter-current with the hot air. Fast initial drying is achieved in this zone while burning the product is prevented by rapid evacuation of the produced particles to the colder periphery under the action of the centrifugal force generated by the vortex chamber(s). Typical residence time of the particles in the hot zone can be limited to a few milliseconds. Drying is continued in the colder periphery where high-G operation intensifies interfacial mass, heat and momentum transfer and ensures efficient gas-solids separation.
| Original language | English |
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| Pages | 1 |
| Number of pages | 3 |
| Publication status | Published - 19 Sep 2019 |
| Event | 12th European Congress of Chemical Engineering 2019 - Florence, Italy Duration: 15 Sep 2019 → 19 Sep 2019 Conference number: 12 http://www.ecce12-ecab5.org/ |
Conference
| Conference | 12th European Congress of Chemical Engineering 2019 |
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| Abbreviated title | ECCE 2019 |
| Country | Italy |
| City | Florence |
| Period | 15/09/19 → 19/09/19 |
| Internet address |