APV Dryer Handbook - Umbc

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70 HIGH FAT PRODUCTS If the powder contains fat, however, the higher pressure drop has an overall dis-advantage. The higher velocity causes the fatty powder to smear around the lower part of the conical cyclone body. This smearing results in a firm layer building up on the inside surface, which can ultimately cause the cyclone to block and cease to discharge any powder. With this type of powder, it is necessary to reduce the cyclone pressure drop to also reduce the swirl velocity as well as the chance of bridging the cyclone. If two inner cone inserts are available, install the larger diameter cone insert for high fat powders. It may also be necessary to adjust the main airflow to trim the cyclone pressure drop, understanding that this will reduce the instantaneous production rate. The actual pressure drop that will allow the system to operate successfully may depend on the fat content, but could be as low as 4 inches (100 mm) w.c. This low pressure drop is not really detrimental to collection efficiency, since higher fat products tend to be easier to collect than low fat powders. LEAKING SEALS One frequent cause of reduced airflow is leaking seals around access doors and clean-out ports. These seals should be checked visually when the plant is being washed, but they can also be checked by ear while the plant is in operation. If a whistling noise can be heard coming from a flange or door seal, it probably indicates a leak. The source of the noise should be found and the area marked for checking at the next opportunity. Powder deposits can be another indication of a leak, which should be corrected. Leaking seals in the chamber or powder carrying ducts usually cause a localized deposit to occur. These deposits are due to condensation on the cold surfaces adjacent to the leak and can be seen immediately prior to cleaning the plant after a production run. DETECTION AND CORRECTION The simplest method of accurately locating the leaking part of a door seal is to
coat the metallic part of the seal face with “prussian blue” or similar marking compound, then close the door. When the door is closed, the blue will transfer to the seal face wherever the seal is mating correctly, but will leave the white silicone uncolored at the places where a seal is not made. To correct the seal, the metal face must be bent towards the silicone seal. Around the main chamber door, this can be accomplished using a large wrench and an extension pipe. On the smaller inspection doors, a special tool can be procured from <strong>APV</strong>. If the rubber seal has been damaged, replacement tubular seal material is also available from <strong>APV</strong>. POWDER COOLING SYSTEM Hygroscopic or thermoplastic powders need to be cooled prior to final packaging to avoid the formation of lumps in the box. This cooling is accomplished by transferring the powder from the main cyclone into a secondary air stream, which is dehumidified and re-heated to reduce the relative humidity. Figure 34. Powder cooling system 71
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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
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10 Direct heating is used extensive
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12 corresponding number of conventi
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14 Two particular types are the dou
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16 particular application and the m
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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 60 and 61: 60 inwards towards the centerline o
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 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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