Particle size reduction

Kausar AhmadKulliyyah of PharmacyPHM3133 Dosage Design 1 2011/121Particle SizeReduction & Separationhttp://staff.iium.edu.my/akausar

1ContentsPHM3133 Dosage Design 1 2011/122Particle size reductionFluid energy mill or jet millAir classifier millOthersCrusherGrinder

Particle size separationCycloneOthersSieves ClassifiersMembrane filtration

2Equipment & mechanismPHM3133 Dosage Design 1 2011/123Crusher compressionE.g. crushing rolls (5 mm)Grinder impact and attritionE.g. hammer/ball millls, bowl grinder (100 m)Ultra-fine grinder attritionE.g. fluid-energy mills (5 m)Knife - cuttingE.g. carrot slicer ( 5 mm)3Choosing the equipmentPHM3133 Dosage Design 1 2011/1244Step-by-step size reductionPHM3133 Dosage Design 1 2011/125Feed material 10 cmCrusher : 10xFeed 1 cmGrinder: 100xFeed 100 mFluid energy mill: 20xProduct ca. 5 m

HOW MANY TIMES REDUCTION?5Attrition mills - principlePHM3133 Dosage Design 1 2011/126attrition - the act of wearing or grinding down by frictionhit the particles with high velocity air to fracture themincreasing the impact velocity or the energy (increase temperature), produces smaller particlesgenerate a greater amount of fines

What types of materials can be processed using the attrition methods?

.and what types. cannot?

6Types of attrition millsPHM3133 Dosage Design 1 2011/127Fluid energy millHigh pressure steam, high TCompressed air, high TAir classifier millAir FEED into slightly negative pressure compartment!Q. But why?

7ClassifierPHM3133 Dosage Design 1 2011/128Equipment that is used to narrow down the size distribution of productNormally built-in design i.e. comes together with the mill

Classifying ability depends onDesign and operation condition Feed throughputAir velocity

8Air classifier millPHM3133 Dosage Design 1 2011/129Consists of:Hammer millHammer mill reduces the sizeClassifierClassifier determines the size distribution

Size and distribution depends onDesign of mill and classifierOperation conditionsTheir speed of rotationFeed throughput9PHM3133 Dosage Design 1 2011/12Air classifier mill (ACM)CLASSIFIERFEEDATMOSPHERIC AIRROTATEROTATEPRODUCT ca. 100 m(to Fluid Energy Mill)10If the particle is TOO BIG when it enters the classifier compartment, the particle will fall down into the millFurther size reduction occurs until the particle can escape the classifierThus the maximum size that goes out of classifier is controlled Minimum size depends on mill design e.g. height of pin

10Fluid Energy Mill (FEM)PHM3133 Dosage Design 1 2011/1211

Superheated compressedAir/steamFEED (from ACM)

Area enlarged11FEM: Design & OperationPHM3133 Dosage Design 1 2011/1212Size and distribution depends onDesign Air nozzlesFeed inletsGrinding chamber

Operation conditionsAir/steam at high pressure and temperature is introduced into the chamber and reduces the size of particlesFeed throughput

12FEMPHM3133 Dosage Design 1 2011/1213

After size reductionAir/steam at high P, T13PHM3133 Dosage Design 1 2011/1214FEEDinto FEM injectorSize reduction & separationFEMCYCLONECYCLONEPRODUCTPRODUCTHIGH VELOCITYHOT AIR/STEAM?14CyclonePHM3133 Dosage Design 1 2011/1215Equipment for separationTo separate product from air and/or fines

Based on centrifugal forceHeavy particles settle downFine particles escape

15CyclonePHM3133 Dosage Design 1 2011/1216INLETOUTLETPRODUCTFINESFROMFEM16Factors affecting extent of separationPHM3133 Dosage Design 1 2011/1217Design of cycloneDiameterHeight

Operation of cycloneFeed throughputVelocity at inlet

17Feed propertiesPHM3133 Dosage Design 1 2011/1218Need to know size distribution of the feed stream. may lead to significant cost-reduction methods such as pre-classifying the material to remove fines before milling. Thus, use air classifier mill first, followed by fluid energy mill.18Controlling feed/throughputPHM3133 Dosage Design 1 2011/1219feeding the material into a mill, and handling the product discharging from it, can pose a significant problem e.g. FEM back-flow

feed at a controlled rate is critical to optimizing the performance of mills.

19Problems with poor feed-controlPHM3133 Dosage Design 1 2011/122020Example of equipment wearPHM3133 Dosage Design 1 2011/1221

FEM milling area

CONSTRUCTION MATERIAL + FEED

Internal piping21Problems with FINE productsPHM3133 Dosage Design 1 2011/1222Highly charged, staticMay produce sparksPossible explosionNeed to earth equipmentVery cohesiveStick to silosForm agglomeratesPoor flowAdd (pyrogenic) silica to allow free flowHealth hazard..

De-duster22Dust Filter

PHM3133 Dosage Design 1 2011/1223

http://www.pharmaceuticalonline.com/nl/347748/1849996

23ExercisePHM3133 Dosage Design 1 2011/1224What do you do with so much air/steam in your milled products?

What is the difference between a fluid energy mill and a fluidised bed dryer?Function?Operating principle?

24ReferencesPHM3133 Dosage Design 1 2011/1225Levin, M. (2002). Pharmaceutical process scale-up. New York: Marcel Dekker. p 71, 120, 205, 224, 322, 417, 501, 503

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