U N I U V N E I R V S E I T R Y S I O T F Y C O O F P C E O N P H E A N G H E A NG E N Drilske pulvere hvordan problemer med flydeevnen kan løses ved brug af shear test-karakterisering Søren V. Søgaard, ph.d.-studerende soren.sogaard@sund.ku.dk Section of Pharmaceutical Technology and Engineering Institut for Farmaci Det Sundhedsvidenskabelige Fakultet Københavns Universitet Slide 1
Agenda Introduction to powder flow and powder characterization techniques Shear and wall friction tests and their applications Time consolidation (caking) Future challenges Slide 2
Take home message Shear testing is an effective powder characterization tool Shear testing is useful during both development of new products and for process design/optimization It can help you to: - Development new and better products - Reduce segregation issues - Avoid caking - Avoid shut-down periods in production plants - Select proper processing equipments Slide 3
Introduction common flow problems Mass, funnel and mixed flow Cohesive and mechanical arch Uniform quality No flow = No production Slide 4 Illustrations: ref. 1 and 2
Introduction characterization techniques State-of-the-art in the pharmaceutical industry Hausner ratio/compressibility index Flow through an orifice Angle of repose Shear cell Empirical flow measurements www.assentoftsilo.dk 4.75L tablet press hopper (pilot scale) Slide 5
Introduction import parameters for powder properties Flow properties of bulk solids depend on many parameters, e.g.: Particle size distribution Particle shape Chemical composition of the particles Moisture Temperature Level of consolidation In addition, the flow properties and flow pattern of bulk solids also depend on: Equipment design/geometry Powder-wall friction Slide 6
D E P A R T M E Søborg, N T O F Oct P H A 21, R M 2013 A C Y Ring shear tester Shear cell Wall friction cell Slide 7 Illustration: ref. 1
Shear tests Shear testing Measures the internal friction of the powder at steady-state flow (cohesion), σ 1 0.5 85 kpa ff c : flowability = σ 1 /σ c ϕ e : Effective angle of internal friction Slide 8 Illustrations: ref. 1 and 3
Shear tests σ 1 ff c = σ 1 σ c σ c Slide 9 Illustrations: ref. 1
Wall friction tests Wall friction testing Measures the friction between the powder and wall material (adhesion), σ w 0.2 23 kpa φ x :wall friction angle Slide 10 Illustration: ref. 1
Determination of flow patterns Slide 11 Illustrations: ref. 1
Time consolidation (caking) Water content Temperature Consolidation Slide 12 Illustrations: ref. 1
Time consolidation (caking) Slide 13 Illustrations: ref. 1
Future challenges - flow pattern under low consolidation Discharge from a 4.75 L tablet press hopper, θ c = 22.6 Experimental conditions: 21 C and 40 %RH Fill height: 34 cm (2 cm from the top) Observations: Flow patterns during discharge Slide 14
Future challenges - flow patterns under low consolidation Videos Slide 15
Wall friction angle, φ x (Pa) U N I V E R S I T Y O F C O P E N H A G E N Future challenges - flow patterns under low consolidation 35 30 25 Funnel flow φ x = arctan φ x = arctan φ x = arctan τ w σ w 4.0 Pa 1000 Pa = 0.2 4.0 Pa 200 Pa = 1.1 20 15 d 50 = 72 µm d 50 = 122 µm 10 5 0 0 200 400 600 800 1000 1200 Wall normal stress, σ w (Pa) Slide 16 Mass flow d 50 = 230 µm
Future challenges arching under low consolidation d = 1 sin(φ e) 1 + sin(φ e ) σ 1 0.2 g ρ b σ 1 = 500 Pa g = 9.81 m/s 2 ρ b = 700 kg/m 3 ϕ e = 45 d = 6 cm σ 1 = 500 Pa g = 9.81 m/s 2 ρ b = 700 kg/m 3 ϕ e = 30 d = 12 cm σ 1 = 500 Pa g = 9.81 m/s 2 ρ b = 300 kg/m 3 ϕ e = 45 d = 15 cm Slide 17 Illustration: ref. 1
Future challenges accurate models for odd sized equipment Axi-symmetrical conical hopper MFI = v wall v center Eccentric conical hopper Slide 18 Illustrations: ref. 1 and 4
Take home message Shear testing is an effective powder characterization tool Shear testing is useful during both development of new products and for process design/optimization It can help you to: - Development new and better products - Reduce segregation issues - Avoid caking - Avoid shut-down periods in production plants - Select proper processing equipments Slide 19
Future perspectives for powder technology in DK Initiate a Danish bulk solids research center Focus area: Food, chemical and pharmaceutical applications, i.e. small and intermediate-scale productions Task 1: To improve the bulk solids characterization methods Task 2: To improve the theoretical models for predicting flow, flow patterns, discharge rates and segregation tendencies. Task 3: To educate the future bulk solids specialists for the Danish industry Annual national conference focusing on particle and bulk solids technology DTI? Slide 20
Acknowledgements Financial Support Drug Research Academy, University of Copenhagen H. Lundbeck A/S DFM A/S Collaborators Prof. Jukka Rantanen, PhD Morten Allesø, PhD Jørgen Garnæs, PhD Troels Pedersen, BSc Pharm Niels Erik Olesen, PhD student Scientific Advises Dr.-Ing. Dietmar Schulze Slide 21
Thank you for listening Questions? E-mail: soren.sogaard@sund.ku.dk References 1. Schulze D. Powders and Bulk Solids: Behavior, Characterization, Storage and Flow (2008) 2. Tomas J. Efficent Product Characterization and Processing of Pharmaceutical Particulate Solids (PhD course) (2013) 3. Ketterhagen WR et al. Predicting flow mode from hoppers using the discrete element method. Powder Technology 195 (2009) 1-10 4. Ketterhagen WR et al. Optimizing the design of eccentric feed hoppers for tablet presses using DEM. Computers and Chemical Engineering 34 (2010) 1072-1081 Slide 22