APV Dryer Handbook - Umbc

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60 inwards towards the centerline of the spray. This is caused by the exchange of momentum between the liquid droplets and the air in the drying chamber – the pressure within the spray tends to become lower than the pressure outside the spray, causing it to contract (Figure 28). SWIRL CHAMBER Feed liquid passes from the nozzle body, tangentially into the swirl chamber, where it is forced to rotate. The faster the rotational speed, the wider the spray angle becomes. The volume of the swirl chamber controls the rotational speed for a given flow rate. The thinnest swirl chamber is designated by the letter “A” – subsequent letters denote thicker, and hence larger, swirl chambers. As a general rule, use a thinner swirl chamber to get a wider spray or a thicker swirl chamber for a narrower angle or longer spray. ORIFICE SIZE The choice of orifice size is dependent on the liquid flow rate and the powder particle size desired. The swirling liquid leaves the orifice plate as a hollow spinning tube formed on the inner edge 15 m/s (4.6 ft/s) of the orifice hole. 30 m/s (9 ft/s) To get finer particles, a higher nozzle 40 m/s(12.2 ft/s) pressure is required. 100 m/s (30.4 ft/s) For a given flow rate, this means that a smaller orifice is needed. For larger particles, NOMINAL use a bigger orifice SPRAY to get a lower nozzle pressure. Figure 28. Nominal spray
FLOW RATE The flow rate of liquid into the spray dryer is used to control the dryer outlet temperature and hold it at a given value to keep a controlled powder moisture. If a certain product can be dried at a higher inlet temperature, then the flow rate will be higher to keep 0 100 200 300 mm the outlet temperature Figure 29. “Hollow Cone” spray actually fills further from down. This higher flow the nozzle rate will require a larger orifice or you can expect an increase in nozzle pressure to get a finer powder particle. Feed solids content is another factor that impacts flow rate. The dryer is only evaporating water. Powder is just the “left-over” portion. Diluting the feed means less powder for each pound of water, or put another way, less powder will be produced from the dryer, even though it is running at the same operating temperatures. NOZZLE PRESSURE Nozzle pressure has a large influence on the final powder particle size. If you want larger particles or a coarser powder, you need to use a lower nozzle pressure. For finer particles, use a higher nozzle pressure. Nozzle pressure, for a given orifice size, varies as the square of the flow rate – a higher flow gives a much higher pressure. CENTRIFUGAL ATOMIZER In a centrifugal atomizer shown in Figure 30, the feed liquid is accelerated to 61
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Improving Process Profitability...C
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I N T R O D U C T I O N The drying
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8 POWDER TYPE D R Y E R S Fine Free
Page 10 and 11: 10 Direct heating is used extensive
Page 12 and 13: 12 corresponding number of conventi
Page 14 and 15: 14 Two particular types are the dou
Page 16 and 17: 16 particular application and the m
Page 18 and 19: 18 whether there is any need to re-
Page 20 and 21: 20 material comes into contact with
Page 22 and 23: 22 together since both share simila
Page 24 and 25: 24 circulation. Alternatively, and
Page 26 and 27: 26 Each of the types available are
Page 28 and 29: 28 At this time Pulse Drying techno
Page 30 and 31: 30 E F F I C I E N T E N E R G Y U
Page 32 and 33: 32 DRYER FEED MOISTURE CONTENT (% W
Page 34 and 35: 34 DRYING COLUMN SCREW FEEDER PARAM
Page 36 and 37: 36 way a dryer can be turned down i
Page 38 and 39: 38 3. The wetted particles sink int
Page 40 and 41: 40 TEMPERATURE (°C) 150 100 50 0 4
Page 42 and 43: 42 flow patterns, residence time di
Page 44 and 45: 44 As indicated by this partial lis
Page 46 and 47: 46 FEED HP PUMP COMPRESSED AIR AGGL
Page 48 and 49: 48 S P I N F L A S H D R Y E R S fo
Page 50 and 51: 50 PROCESS DESCRIPTION The Spin Fla
Page 52 and 53: 52 Figure 24 illustrates the very r
Page 54 and 55: 54 The drying chamber would be main
Page 56 and 57: 56 COST BENEFITS In comparison to a
Page 58 and 59: 58 S P R A Y D R Y E R S SPRAY DRYE
Page 62 and 63: 62 a high speed by a spinning disc.
Page 64 and 65: 64 internal bowl diameter, radial d
Page 66 and 67: 66 variations, some plants utilize
Page 68 and 69: 68 Condensation deposits can freque
Page 70 and 71: 70 HIGH FAT PRODUCTS If the powder
Page 72 and 73: 72 INLET TEMPERATURE The powder coo
Page 74 and 75: 74 POWDER DENSITY The density of sp
Page 76 and 77: 76 chamber wall, tending to scour a
Page 80: Local Office APV Separations Produc
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APV Dryer Handbook - Umbc

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