July 12/13 2005 Flash-drying: a suitable technology for bulk solids processing Ricard Fenollosa– Sales Manager Riera Nadeu S.A 1 HOTorNOT Seminar SOME BASIC CONCEPTS Thermal separation: to form homogeneous groups of substances whichever mixed with other ones, applying heating energy. Mix: Combination of 2 or more substances where all ingredients are keeping its own physical identity. In a mix substances con be combined in any proportion. The properties of the mix are the combined properties of all ingredients and these component can be recovered with no alteration from de mix without a chemical reaction. Drying operation is a contact mass transference (solid/liquid), where moisture mix will be transferred by means evaporation to the gaseous phase, based to the vapour pressure coming from the mix and the partial vapour pressure of the gas flow. 2
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July 12/13 2005
Flash-drying: a suitabletechnology for bulksolids processing
Ricard Fenollosa– Sales Manager Riera Nadeu S.A
1
HOTorNOT Seminar
SOME BASIC CONCEPTS
Thermal separation: to form homogeneous groups of substanceswhichever mixed with other ones, applying heating energy.
Mix: Combination of 2 or more substances where all ingredientsare keeping its own physical identity. In a mix substances con be combined in any proportion. The properties of the mix are thecombined properties of all ingredients and these component can be recovered with no alteration from de mix without a chemicalreaction.
Drying operation is a contact mass transference (solid/liquid), where moisture mix will be transferred by means evaporation to thegaseous phase, based to the vapour pressure coming from the mixand the partial vapour pressure of the gas flow.
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More CONCEPTS
Vaporization: Runing of molecules from liquid phase to gas.
The molecules which run off are the more close to the hot surface.
So, evaporation is fastest; at same pressure level, when thetemperature is higher, due a large fraction of molecules haveenough energy to run off.
Effect of pressure:
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17910,0991,0
1586,0860,6
1202,0600,2
1708,0930,8
1434,0750,4
°C bar °C bar
Temp.PresiónTemp.Presión
Boiling temeperatures of H2O at different
pressures:
CONCEPT
Heat transfer: process where there is energy interchangeamong several parts or among different element of onebody whose are at same temperature.
The heat is transferred by means convection, radiationor conduction. These three processes can be carried out simultaneously, but it can occur that one of themechanisms will be predominant on the other ones.
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When is used a thermal solid-liquid separation process?
When the specs. for separation of final products are no possible toreach by means mechanical methods: centrifugation, decanting, filtration, …
When product value permits it.
Potential Secondary Effects of Drying
Tension and shrinkage (constriction) of dried material) (i.e. ceramicmaterials)
Chemical changes (pirolisis, oxidations, ….)
Bio-chemical changes (food, proteins, …)
Estrcuctural changes (modification on crystalline phase, shape, particlesize,…)