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98 obtained the max<strong>im</strong>um deviation of the strength 1 c not higher than ± 0,13 kPa, not dependent on the level of consolidation pressure. These authors have reported good repeatability of results with deviation not higher than 5%. According to the authors, the reproducibility of the tester, together with operator independence and fairly rapid test procedure make the equipment a suitable tool for quality control of powders. Accuracy of the method allows for flow property deviations from batch to batch in batch production operations. The equipment may be also used for investigations of the compaction properties of slightly compacted samples, determination of the modulus of elasticity, or examinations of stress relaxation and creep phenomena of powders. 3LVWRQ 0ROG (ODVWLF PHPEUDQH 6DPSOH %DVH SODWH D8QLD[LDOFRPSUHVVLRQ E)DLOXUH Fig. 13.4. POSTEC uniaxial tester [102] 13.2. Carr Indices Chemical industry and, particularly, pharmaceutical industry need characterization of fine powders. Flowability determines operations of transport, mixing, dosing, storage granulation or forming tablets. Carr Indices are willingly used by practitioners of those industries, and were standardized by the American Society for Testing Materials [7]. The method can be applied to free flowing and moderately cohesive powders and granular materials up to 2 mm in size. Materials must be able to pour through a 7.0 ± 1.0 mm diameter funnel outlet when in aerated state. The method consists of eight measurements and two calculations to provide ten tests for Carr Indices. These ten tests are as follows:
99 A. Measurement of Carr Angle of Repose B. Measurement of Carr Angle of Fall C. Calculation of Carr Angle of Difference D. Measurement of Carr Loose Bulk Density E. Measurement of Carr Packed Bulk Density F. Calculation of Carr Compressibility G. Measurement of Carr Cohesion H. Measurement of Carr Uniformity I. Measurement of Carr Angle of Spatula J. Measurement of Carr Dispersibility. In practice the Carr Index CI is also popular, that is defined [8] as: 100 × (! t − ! l) CI(%) = , (13.2) ! where: ! t – tapped bulk density, ! b – loose bulk density. This parameter is determined, after compaction of material by tapping, in a cylindrical container of a volume from 10 to 1000 ml, with user-defined number of taps (from 10 to 500). Out of the same measurement another popular parameter, the Hausner Ratio, may be calculated as: ! t t R h = . (13.3) ! l In industrial practice it is assumed that the powder is easy flowing having CI in range from 5 to 15%, while durable tablets may produced of powder having R h not higher than 1.6. 13.3. In-line control of structure of granular products For contemporary highly automated mass production in-line methods of characterization of materials are in the highest demand. In the first approach inline methods of measurement of particle size distribution were elaborated. Knowledge of particle size distribution allows for efficient process control and control of product quality. Process output continuously increases and delay between laboratory measurement and process correction may be unacceptable. Currently pneumatic conveying is extensively used in industry because it enables
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EC Centre of Excellence AGROPHYSICS
Page 4 and 5:
4 9.3. Factors influencing the coef
Page 6 and 7:
6 BASIC NOTATION c - cohesion [kPa]
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8 Numerous granular materials when
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10 the tensor of plastic strain inc
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12 Fig. 2.1. Yield curves with comp
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14 Stable or unstable behaviour of
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16 In turn, the model of Lade, also
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18 same porosity need not have iden
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20 where: A = ∫ E( β) sin βdβ
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22 (β = 0 o ), positioning the out
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24 grain was poured into the mould
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26 axes of the ellipse characterizi
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28 [176] for the determination of p
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30 A different approach to the desc
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32 where: I - moment of inertia, k
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34 a) b) f s f s m M f n f n Contac
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36 The micropolar model yields resu
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38 Fig. 3.17. Model of shear band f
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40 In the case of agricultural mate
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42 5.2. Density of consolidated mat
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44 (cereal grain, sand, soil), the
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46 Multiple wetting and drying of g
Page 48 and 49: 48 vertical pressure within the ran
Page 50 and 51: 50 of the curve defined by A, where
Page 52 and 53: 52 6. Vertical consolidation refere
Page 54 and 55: 54 poured into the box without vibr
Page 56 and 57: 56 7.2.2. Bulk density Stress-strai
Page 58 and 59: 58 near the box wall and lifted alo
Page 60 and 61: 60 and the upper boundary was 18.5
Page 62 and 63: 62 A -1 5 -1 0 -5 1 0 5 -5 5 1 0 1
Page 64 and 65: 64 Fig. 8.2. Yield locus and effect
Page 66 and 67: 66 in such a way that friction woul
Page 68 and 69: 68 a) b) µ = tg ϕw ϕ w c) d) e)
Page 70 and 71: 70 9.3. Factors influencing the coe
Page 72 and 73: 72 galvanized steel received from d
Page 74 and 75: 74 9.3.4. Velocity of sliding Becau
Page 76 and 77: 76 1+ sinϕ k = . 1 − sinϕ (10.3
Page 78 and 79: 78 N ϕ VLQϕ 3UHVVXUHUDWLRN
Page 80 and 81: 80 10.4.1. Friction force mobilizat
Page 82 and 83: 82 10.4.3. Moisture content With in
Page 84 and 85: 84 Table 10.1. Measured (k s ) and
Page 86 and 87: 86 conventional engineering analyse
Page 88 and 89: 88 a, b - product-dependent coeffic
Page 90 and 91: 90 also be performed as a function
Page 92 and 93: 92 reliable processing and stable v
Page 94 and 95: 94 unconfined yield strength to pow
Page 96 and 97: 96 The Chute Index (CI) is recommen
Page 100 and 101: 100 efficient flow control using op
Page 102 and 103: 102 In the field of experimental in
Page 104 and 105: 104 22. Britton M.G., Moysey E.B.:
Page 106 and 107: 106 69. Horabik J., Rusinek R.: Pre
Page 108 and 109: 108 114. Morland L.W., Sawicki A.,
Page 110 and 111: 110 158. 6WSQLHZVNL$ Influence of m
Page 112 and 113: 112 16. APPENDIX - Physical Propert
Page 114 and 115: 114 16.2. Density and porosity Tabl
Page 116 and 117: 116 Table 16.7. Mean values (±St.
Page 126 and 127: 126 Table 16.16. Cont. 1 2 3 4 Icin
Page 136 and 137: 136 Table 16.25. Cont. 1 2 3 4 Icin
Page 140 and 141: 140 Table 16.29. Cont. Table sugar
Page 144 and 145: 144 Table 16.35. Mean values (± St
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