Size Reduction

Work in this area covers both comminution and undesirable particle breakage, commonly referred to as attrition, although the term attrition milling is also used in literature to describe deliberate size reduction of ‘difficult to mill’ particulate solids. In many particle processing operations in various industries, such as agricultural, food, detergent, and pharmaceutical attrition leads to deviation from desired product specification, formation of debris and dust and potential explosion hazards.

We have developed models of impact breakage accounting for material mechanical properties and have also analysed particle breakage under bulk shear straining of particles. Due to the inherent distribution of strength, size and shape within an assemblage of particles, and the difficulty in calculating local stresses therein, no mechanistic models of bulk particle breakage exist. Consequently, empirical approaches are commonly used to establish the breakage rate. Our work has recently shown that by analysing the prevailing stresses in an item of process equipment using DEM and incorporating an experimentally-determined breakage function, particle breakage within the bed can be reliably predicted.

Our research group has a number of devices for measuring particle breakage:

• Bridgwater attrition shear cell
• Single particle impact tester
• Instron mechanical tester – for measuring single or bulk crushing
• Single ball mill – for analysis of bulk milling
• Micromaterials NanoTest – for determining hardness, Young’s modulus and fracture toughness by nanoindentation
• Micromaterial Nano-Crush for strength testing of fine particles at tribological testing

Our research on milling addresses various loading mechanisms, such as impact, shearing, crushing, attrition or a combination of them, and the prevailing particle dynamics in a number of mill types. We have the following mill types in our facility:

• Planetary ball mill
• Vibrating ball and disc mills
• Spiral jet mill
• Stirred media mill

Current research topics include the grindability of crystalline and amorphous solids, associated structural changes and physical, chemical and mechanical transformation, energy utilisation, and particle-fluid interactions in spiral jet mills, using numerical simulations by combined DEM and CFD method.

• Attrition of Spray-Dried Powders
• Attrition and Phase Changes during Agitated Drying
• Attrition in circulating fluidised beds

• Particle Breakage in Dryers and Agitated Beds
• Development of a Device to Test the Strength of Enzyme Granules
• Analysis of Enzyme Dust Formation in Detergent Manufacturing Plants
• Breakage of Catalyst Carrier Particles
• Mitigation of Attrition in Fluid Catalytic Cracking Units
• Analysis of ISO Fluidised Bed Jet Test
• Attrition of Particulate Solids in Fluidised Bed Jets
• Formation, Processing and Characterisation of Pharmaceutical Powders
• Attrition of Particulate Solids
• Distinct Element Simulation of Attrition in an Annular Shear Cell
• Disintegration of Weak Agglomerates.

Hare, C., Ghadiri, M., "Influence of Measurement Cell Size on Predicted Attrition by the Distinct Element Method", Powder Technology, Available online 5 May 2012, ISSN 0032-5910, 10.1016/j.powtec.2012.04.061.

Hare, C., Ghadiri, M., Dennehy, R. 2011, "Prediction of Attrition in Agitated Particle Beds", Chemical Engineering Science, 66(20), 4757-4770.

Ahmadian, H., Hassanpour, A., Ghadiri, M. 2011, "Analysis of Granule Breakage in a Rotary Mixing Drum: Experimental Study and Distinct Element Analysis", Powder Technology, 210(2), 175-180.

Olusanmi, D., Roberts, K., Ghadiri, M., Ding, Y. 2011. "The breakage of Aspirin under Quasi-Static Indentation and Single Particle Loading: Effect of Crystallographic Anisotropy", International Journal of Pharmaceutics, 411(1-2), 49-63.

Olusanmi, D., Wang, C., Ghadiri, M., Ding, Y. and Roberts, K.J., 2010, "Effect of Temperature and Humidity on the Breakage Behaviour of Aspirin and Sucrose Particles", Powder Technology, 201(3), 248-252.

Ahmadian, H. and Ghadiri, M. 2010, "Attrition Shearing of Granules using Rotating Rollers: Experimental Study and DEM Simulation", World Congress of Particle Technology 6, Nuremberg.

Hassanpour, A., Antony , S.J. and Ghadiri, M., "Influence of Interface Energy of Primary Particles on the Deformation and Breakage Behaviour of Agglomerates Sheared in a Powder Bed", Chemical Engineering Science, 63(23), 5593-5599, 2008.

Ahmadian, H., Ghadiri, M. , 2007, "Analysis of Enzyme Dust Formation in Detergent Manufacturing Plants", Advanced Powder Technology, 18, pp. 53-67.

Hassanpour, A., Antony , S.J., Ghadiri, M. , 2007, "Effect of Size Ratio on the Behaviour of Agglomerates Embedded in a Bed of Particles Subjected to Shearing: DEM Analysis", Chemical Engineering Science, 62(4), pp 935-942.

Yang, W., Kwan, C.C., Ding, Y.L., Ghadiri, M., Roberts, K.J. , 2007, "Milling of Sucrose", Powder Technology, 174, 14-17.

Ahmadian, H. and Ghadiri, M. 2010, "Attrition Shearing of Granules using Rotating Rollers: Experimental Study and DEM Simulation", World Congress of Particle Technology 6, Nuremberg.

Hassanpour, A., Antony , S.J. and Ghadiri, M., "Influence of Interface Energy of Primary Particles on the Deformation and Breakage Behaviour of Agglomerates Sheared in a Powder Bed", Chemical Engineering Science, 63(23), 5593-5599, 2008.

Ahmadian, H., Ghadiri, M. , 2007, "Analysis of Enzyme Dust Formation in Detergent Manufacturing Plants", Advanced Powder Technology, 18, pp. 53-67.

Hassanpour, A., Antony , S.J., Ghadiri, M. , 2007, "Effect of Size Ratio on the Behaviour of Agglomerates Embedded in a Bed of Particles Subjected to Shearing: DEM Analysis", Chemical Engineering Science, 62(4), pp 935-942.

Yang, W., Kwan, C.C., Ding, Y.L., Ghadiri, M., Roberts, K.J. , 2007, "Milling of Sucrose", Powder Technology, 174, 14-17.

Moreno-Atanasio, R., Ghadiri, M. , 2006, "Mechanistic Analysis and Computer Simulation of Impact Breakage of Agglomerates: Effect of Surface Energy", Chemical Engineering Science, 61(8), pp 2476-2481.

Ning, Z., Ghadiri, M. , 2006, "Distinct Element Analysis of Attrition of Granular Solids under Shear Deformation", Chemical Engineering Science, 61(18), 5991-6001.

Kwan, C.C., Mio, H., Chen, Y.Q., Ding, Y.L., Saito, F., Papadopoulos, D.G., Bentham, A.C., Ghadiri, M. , 2005, "Analysis of the Milling Rate of Pharmaceutical Powders using the Distinct Element Method (DEM)", Chemical Engineering Science, 60, pp. 1441-1448.

Samimi, A., Hassanpour, A. and Ghadiri, M. , 2005, "Single and Bulk Compressions of Soft Granules: Experimental Study and DEM Evaluation", Chemical Engineering Science, 60, pp. 3993-4004.

Subero-Couroyer, C., Ghadiri, M., Brunard, N., Kolenda, F. , 2005, "Analysis of Catalyst Particle Strength by Impact Testing: The Effect of Manufacturing Process Parameters on the Particle Strength", Powder Technology, 160(2), 67-80.

Bentham, A.C., Kwan, C.C., Ghadiri, M., Boerefijn, R. , 2004, "Fluidised Bed Jet Milling of Pharmaceutical Powders", Powder Technology, 141, pp. 233-238

Hassanpour, A., Ghadiri, M., Bentham, A.C., Papadopoulos, D.G. , 2004, "Effect of Temperature on Energy Utilisation of Bulk Crushing of α-Lactose Monohydrate", Powder Technology , 141, pp. 239-243.

Golchert, D. J., Moreno, R., Ghadiri, M., Litster, J. D. , 2004, "Effect of Granule Morphology on Breakage Behaviour During Compression", Powder Technology, 143-4, pp. 84-96.

Chen, Y.Q., Ding, Y.L., Papadopoulos, D.G., Ghadiri M. , 2004, "Energy Base Analysis of Milling α-Lactose Monohydrate", Journal of Pharmaceutical Science, 93, pp. 886-895.

Kwan, C.C., Chen, Y.Q., Ding, Y.L., Papadopoulos, D.G., Bentham, A. C., Ghadiri, M. , "Development of a Novel Approach Towards Predicting the Milling Behaviour of Pharmaceutical Powders", European Journal of Pharmaceutical Sciences, 23, pp. 327-336.

Samimi, A., Moreno, R., Ghadiri, M. , 2004, "Impact Damage Analysis of Agglomerates: Effect of Impact Angle", Powder Technology, 143-4, pp. 97-109.

Hassanpour, A., Ghadiri, M., Bentham, A.C., Papadopoulos, D.G. , 2003, "Distinct Element Analysis of the Effect of Temperature on the Bulk Crushing of ��-Lactose Monohydrate", Advanced Powder Technology, 14, pp. 427-434.

Kwan, C.C., Ghadiri, M., Papadopoulos, D.G., Bentham, A.C. , 2003, "The Effects of Operating Conditions on the Milling of Microcrystalline Cellulose", Chemical Engineering and Technology, 26, pp. 185-190.

Moreno, R., Antony, S.J., Ghadiri, M., 2003, "Effect of the Impact Angle on the Breakage of Agglomerates: a Numerical Study using DEM", Powder Technology, 130, pp. 132-137.

Samimi A., Ghadiri, M., Boerefijn, R., Groot, A., Kohlus, R. , 2003, "Effect of Structural Characteristics on Impact Breakage of Agglomerates", Powder Technology, 130, pp. 428-435.

Subero-Couroyer, C., Ghadiri, M., Brunard, N., Kolenda F. , 2003, "Weibull Analysis of Quasi-Static Crushing Strength of Catalyst Particles", Chemical Engineering Research and Design, 81, pp. 953-962.

Ghadiri, M., Zhang, Z. , 2002, "Impact Attrition of Particulate Solids. Part 1: A Theoretical Model of Chipping", Chemical Engineering Science, 57, pp. 3659-3669.

Zhang, Z., Ghadiri, M. , 2002, "Impact Attrition of Particulate Solids. Part 2: Experimental Work", Chemical Engineering Science, 57, pp. 3671-3686.

Ghadiri M., Moreno, R., Matsusaka, S. , 2002, "Impact Damage Analysis of Agglomerates Using Distinct Element Method", Journal of the Society of Powder Technology Japan, 39, pp. 885-892 (in Japanese)

Subero, J., Ghadiri, M. , 2001, "Breakage Pattern of Agglomerates", Powder Technology, 120, pp. 232-243.

Boerefijn, R., Gudde, N.J., Ghadiri, M. , 2000, "A Review of Attrition of Fluid Cracking Catalyst Particles", Advanced Powder Technology, 11, pp. 145-174.

Couroyer, C., Ning, Z., Ghadiri, M. , 2000, "Distinct Element Analysis of Bulk Crushing: Effect of Particle Properties and Loading Rate", Powder Technology, 109, pp. 241-254.

Couroyer, C., Ghadiri, M., Laval, P., Brunard, N., Kolenda, F. , 2000, "Methodology for Investigating the Mechanical Strength of Reforming Catalyst Beads", Oil and Gas Science and Technology - Revue de l'Institut FranÁais du PÈtrole, 55, pp. 67-85.

Ghadiri, M., Ning. Z., Kenter, S.J., Puik, E. , 2000, "Attrition of Granular Solids in a Shear Cell", Chemical Engineering Science, 55, pp. 5445-5456.

Scala, F., Salatino, P., Boerefijn, R., Ghadiri, M. 2000, "Attrition of Sorbents During Fluidized Bed Calcination and Sulphation", Powder Technology, 107, pp. 153-167.

Couroyer, C., Ning, Z., Ghadiri, M., Brunard, N., Kolenda, F., Bortzmeyer, D., Laval, P. , 1999, "Breakage of Macroporous Alumina Beads under Compressive Loading: Simulation and Experimental Validation", Powder Technology, 105, pp. 57-65 (correction: ibid, 111, pp. 252-253, 2000).

Subero, J., Ning, Z., Ghadiri, M., Thornton, C. , 1999, "Effect of Interface Energy on the Impact Strength of Agglomerates", Powder Technology, 105, pp. 66-73.

Ning, Z., Boerefijn, R., Ghadiri, M., and Thornton, Thornton, C. , 1997, "Distinct Element Simulation of Impact Breakage of Lactose Agglomerates", Advanced Powder Technology, 8, pp. 15-37.

Papadopoulos, D.G., Ghadiri, M. , 1996, "Impact Breakage of Poly-methylmethacrylate (PMMA) Extrudates: I. Chipping Mechanism", Advanced Powder Technology, 7, pp. 183-197.

Ghadiri, M., Boerefijn, R. "A Model of Attrition in the Jetting Region of Fluidised Beds", KONA Powder and Particle, No. 14, pp. 5-15.

Ning, Z., Ghadiri, M. , "Attrition of Bulk Particulate Solids in a Shear Cell: An Investigation by Computer Simulation", Materials Review, Vol. 10, pp. 72-77 (in Chinese).

Ghadiri, M., Cleaver, J.A.S., Tuponogov, V.G., Werther, J. , 1994, "Attrition of FCC Powder in the Jetting Region of a Fluidised Bed", Powder Technology, 80, pp. 175-178.

Arteaga, P.A., Ghadiri, M., Lawson, N.S., Pollock, H.M. , 1993, "Use of Nanoindentation to Assess Potential Attrition of Particulate Solids", Tribology International, 26, pp. 305-310.

Cleaver, J.A.S., Ghadiri, M., Rolfe, N. , 1993, "Impact Attrition of Sodium Carbonate Monohydrate Crystals", Powder Technology, 76, pp. 15-22.

Ghadiri, M., Yuregir, K.R., Pollock, H.M., Ross, J.D.J., Rolfe, N.J. , 1991, "Influence of Processing Conditions on Attrition of NaCl-Crystals", Powder Technology, 65, pp. 311-320.

Yuregir, K.R., Ghadiri, M., Clift, R. , 1987, "Impact Attrition of Sodium-Chloride Crystals", Chemical Engineering Science, 42, pp. 843-853.

Yuregir, K.R., Ghadiri, M., Clift, R. , 1986, "Observations on Impact Attrition of Antigranulocytes Sliods", Powder Technology, 49, pp.53-57.