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Spray drying: a process step in catalyst manufacturing
2001 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Spray drying is a unit operation to dry various suspensions containing insoluble particles. By definition, spray drying is the transfer of a fluid state feed into dried form by spraying it into a hot gaseous medium. It consists of four process stages: atomisation, contact between air-spray, drying of the spray and separation of the dried product. The most important of these stages is the atomisation, which has a big influence on the final product properties. The dryer used in my trials is a directly fired unit, operating continuously. The flow inside is mixed flow with a two fluid atomiser, where the two fluids (slurry and air) are mixed as they leave the nozzle. This unit operation is used to dry slurry in order to create solid particles. In this thesis, some of the important features such as altering slurry properties (adding additives and changing solid content), as well as various drying conditions have been tested. The objective of these tests was to find out the best way to produce particles that can be easily processed further, i.e. stronger, bigger and more evenly distributed in size, compared to other methods of drying. In order to characterise the particles produced, several measurements to analyse them were used: loss on drying (LOD), particle size distribution and density. The results of altering the slurry properties, via addition of chemical substances, vary. In fact, the addition of nitric acid shows very good results in lowering the viscosity of all tested slurries, whereas addition of ammonia only works for certain slurries. Addition of a surfactant, Hypermer KD6, had no effect. Varying the drying conditions, such as inlet temperature, atomisation pressure and airflow, affects the powder produced. The most efficient setting for the different parameters depends on the desired outcome. For example, if a higher density is desired, the inlet temperature should be as low as possible (i.e. low drying rate) in combination with a high atomisation pressure, within the limitation of the equipment. Another finding is that a lower atomisation pressure, at constant inlet temperature, gives bigger but more fragile particles. Finally, when the solid content of the slurry is increased (20-33%) by adding dry powder, the powder produced has about the same particle size and dry density. The big difference is that the particle strength decreases rather drastically with increasing solid content. Therefore, a compromise between each parameter setting must be adopted in order to achieve a good product having all the desired properties for a specific use.

Place, publisher, year, edition, pages
2001.
Keyword [en]
Technology, spray drying, atomizaton, atomisation, slurries
Keyword [sv]
Teknik
Identifiers
URN: urn:nbn:se:ltu:diva-57171ISRN: LTU-EX--01/294--SELocal ID: ddb77b22-335c-4d1b-b0d2-9d9898313a7dOAI: oai:DiVA.org:ltu-57171DiVA: diva2:1030558
Subject / course
Student thesis, at least 30 credits
Educational program
Chemical Engineering, master's level
Examiners
Note
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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