Lynne Wong's PhD thesis

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5.6.4.2 Kelly’s type of two-equilibria isotherms When the ln of EMC results obtained in Tables 5.8 – 5.16 were plotted against ln of vapour pressure (Table 5.3), as previously described for Kelly’s work (1957) in Section 5.4.1, twoequilibria isotherms were obtained for all nine cane components of R 570 aged 52 weeks (Fig 5.6) and 36 weeks (Fig 5.7). The transition point of the primary and secondary equilibria occurred at ln (EMC/% db) = 2.5, i.e. at EMC/% db = 12.5, compared to the value of 14.5 found by Kelly. The regression coefficient R 2 and the Freundlich constants s and k are compiled for 52 weeks samples (Table 5.17) and for 36 weeks samples (Table 5.18). All the slopes s of the primary equilibria for 30, 45, 55 and 60 °C isotherms are different for all cane components, the same applied to the slopes of the secondary equilibria for 30, 45, 55 and 60 °C isotherms. Therefore, it was not possible to calculate the heat of adsorption involved in the primary and secondary equilibria as did Kelly, since his calculations were based on the identical slope of 1.14 for the primary equilibria of both 27.2 °C and 51 °C isotherms, and 5.55 for their secondary equilibria. When Kelly’s EMC data (1957) were plotted similarly, the gradients of the primary equilibria at 27.2 °C and 51 °C were found respectively: 0.854 and 1.137, and of the secondary equilibria at 27.2 °C and 51 °C were respectively 3.305 and 4.551. 5.6.4.3 Adsorption isotherms The adsorption isotherms for the nine sugar cane component parts aged 52 weeks are shown in Fig 5.8. Typical S-shape curves referred to as type II isotherms were found. According to Van den Berg and Bruin (1981), type II isotherms can be divided into three different regions: in the first region at low water activity, there is monolayer adsorption of water held by strong hydrophilic bonds on polar sites by Van der Waal forces. In the second region, called the multilayer region, water is more loosely held by hydrogen bonds and is under transition to the natural properties of free water. The least firmly bound water occurs when a w is above 0.6. In the third region, the isotherm rises steeply as practically free water becomes mechanically entrapped in the void spaces of the material, mainly as a result of capillary condensation. Water uptake in the first region is normally rapid, slows down in the second region and is accelerated in the third region. The adsorbed water can be classified as monolayer, multilayer or condensed capillary water. The enthalpy of 203
vaporisation generally decreases from the first to the third region. The nine sugar cane components aged 36 weeks also exhibit type II isotherms (Fig 5.9). Stalk fibre Stalk pith Rind fibre 4 4 4 ln(EMC/% db) 3 2 1 3 2 1 3 2 1 0 0 2 4 6 0 0 2 4 6 0 0 2 4 6 Rind fines Top fibre Dry leaf fibre 4 4 4 ln(EMC/% db) 3 2 1 3 2 1 3 2 1 0 0 2 4 6 0 0 2 4 6 0 0 2 4 6 Dry leaf fines Green leaf fibre Green leaf fines 4 4 4 ln(EMC/% db) 3 2 1 3 2 1 3 2 1 0 0 2 4 6 0 0 2 4 6 0 0 2 4 6 ln (water vapour pressure/mm Hg) 30°C 45°C 55°C 60°C Figure 5.6. Adsorption isotherms of nine cane components aged 52 weeks (as per Kelly’s method, 1957). Note the similar behaviour of all the nine cane components. 204
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THE BRIX-FREE WATER CAPACITY AND SO
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dissolved and hydrated waters, and
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ACKNOWLEDGEMENTS I am particularly
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Page 1.5 THE DELETERIOUS EFFECTS OF
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Page 2.2 THE PHENOMENON OF BRIX-FRE
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Page 3.4.3.3 Cane tops 83 3.4.4 Cha
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4.3.3 Temperature at which Brix-fre
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4.6.1 Materials 143 4.6.1.1 Samples
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CHAPTER 6. PROPERTIES OF THE SORBED
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APPENDIX 3. CALCULATIONS LEADING TO
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LIST OF FIGURES Page Figure 1.1. Fi
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Figure 3.1. Glucose and fructose an
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Figure 5.11. Residual plots for the
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total adsorbed water (m) and the pr
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Table 2.18. Moisture content in sug
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Page Table 4.4. Results of the dete
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Page Table 4.24. Analysis of varian
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Page Table 5.13. Table 5.14. Equili
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Table 6.3. Heat of sorption of the
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GLOSSARY OF TERMS Absorption is the
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Filterability of a raw sugar is mea
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Sorption is the generic term used w
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LIST OF MAIN SYMBOLS Symbol Descrip
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s c s Slope of Caurie I isotherm pl
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number of 255, and cane land covere
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Nouvelle Mon In Trésor ustrie and
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Figure 1.3. Cane sampling by core s
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In Mauritius, most of the sugar fac
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are: cane tops, dry and green leave
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1.4 TRENDS IN CANE QUALITY RECEIVED
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campaign was launched to encourage
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The level of extraneous matter in c
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In Australia (Cargill, 1976), cane
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The effect of soil on factory perfo
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leaves increased the level of impur
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• From 1976 to 1980, when the pro
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Clerget purity of molasses 40 Clerg
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CHAPTER 2. IMPACT OF EXTRANEOUS MAT
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Since the extrapolated purity of mo
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Figure 2.1. Jeffco cutter grinder.
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2.1.4 Results The analytical result
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Table 2.3. Analytical results of re
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Table 2.5. Composition of dry trash
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Table 2.7. Predicted factory perfor
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Boiling house recovery 91.0 89.8 89
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0 5 10 15 20 % EM in cane y = 0.572
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% EM in cane 0 5 10 15 20 0 -2 -4 -
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1 y = 0.020 (% D) R 2 = 1.00 = 0.03
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% EM in cane 0 5 10 15 20 0 -2 y =
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esulting in 0.015 unit sucrose loss
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2.2.1 Experimental procedure Cane m
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filter paper, rejecting the first f
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Table 2.9. Effect of increased addi
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Table 2.11. Effect of increased add
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Table 2.13. Effect of increased add
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various components such as stalk fi
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in the presence of dry leaves, if c
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Table 2.17. Moisture content in sug
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CHAPTER 3. SEPARATION OF THE SUGAR
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Table 3.1. It can be seen that the
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Table 3.2. Fibrous physical composi
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R 579 R 570 M 1557/70 M 1400/86 74
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loosen the fibre. The woody core is
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agitate the mixture in the pot, and
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Figure 3.7. Custom-built fibre-pith
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The extraction of fibres starting f
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pre-treatment in a Jeffco cutter-gr
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Figure 3.19. Stalk cake washed free
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not have many dry leaves attached t
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Table 3.5. Masses of cane samples a
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Table 3.7. Masses of cane samples a
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Table 3.9. Masses of cane component
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3 57.6 126.3 23.7 97.2 31.1 53.8 11
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Table 3.12. Material loss (%) from
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3.5.3 Fibre/pith ratios in cane com
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Table 3.15. Effect of extraneous ma
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Snow (1974) investigated the season
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from Figure 2.9 that the change in
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Table 3.18. Fibre % cane results by
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110
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(a). Dry leaf (b). Green leaf (c).
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dry fibre, or a factor, is used in
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Steuerwald (1912) applied sucrose s
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solution/fibre ratio was lowered fr
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leave some residual moisture on the
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instead of 150 g of 10° Brix sucro
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Table 4.2. Determination of Brix-fr
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Table 4.3. Comparison of Brix-free
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Table 4.4. Results of the determina
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In order to test for homogeneity of
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Table 4.7. Results of the repeat de
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The experiment was repeated with th
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e any residual moisture in the samp
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By means of the same technique, Won
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was still hot. Since the filter was
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value determined could be corrected
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Qin and White’s finding was confi
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A sample size of 3.5 g with 75 g co
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Figure 4.4. Fibre samples drying in
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- One large fibre sample (rind) of
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Table 4.18. Brix-free water values/
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Table 4.20. Brix-free water values/
Page 205 and 206: 4.7.3 Statistical analysis It is es
Page 207 and 208: Table 4.23. Analysis of variance (B
Page 209 and 210: pointing out that at 52 weeks old,
Page 211 and 212: The crop of R 570 sampled in 2001 w
Page 213 and 214: 4.7.4. Estimated Brix-free water co
Page 215 and 216: The main difference in the two sets
Page 217 and 218: Table 4.27. Predicted Brix-free wat
Page 219 and 220: 4.8 SUMMARY AND CONCLUSIONS An anal
Page 221 and 222: component parts, and verify the Bri
Page 223 and 224: 3) Thermodynamic, water in equilibr
Page 225 and 226: Langmuir (1916, 1917, 1918) propose
Page 227 and 228: to determine the moisture sorption
Page 229 and 230: Table 5.1. Some commonly used isoth
Page 231 and 232: Lomauro et al. (1985) found that wi
Page 233 and 234: and on agricultural products such a
Page 235 and 236: Bruijn (1963) studied the mass incr
Page 237 and 238: After measuring the EMC of dry corn
Page 239 and 240: approached, that is, either by adso
Page 241 and 242: Table 5.4. Water activity (a w ) of
Page 243 and 244: 5.6.3 Procedure to determine equili
Page 245 and 246: 5.6.4 Results and discussion An exa
Page 247 and 248: Table 5.8. Equilibrium moisture con
Page 249 and 250: Table 5.10. Equilibrium moisture co
Page 251 and 252: Table 5.12. Equilibrium moisture co
Page 253 and 254: 30 o C 45 o C 55 o C 60 o C Water w
Page 255: m/m of 96% activity, a w (g/100g dr
Page 259 and 260: 30 o C isotherm 45 o C isotherm 55
Page 261 and 262: 4 0 Stalk fibre 5 0 Stalk pith 5 0
Page 263 and 264: 5.6.4.4 Fitting of sorption models
Page 265 and 266: Table 5.19. Parameters of the sorpt
Page 275 and 276: Modified GAB Kuhn Iglesias - Chirif
Page 277 and 278: Table 5.28. Classification of resid
Page 279 and 280: Stalk fibre Stalk pith Rind fibre 4
Page 281 and 282: 5.6.4.5 Calculated EMC values of re
Page 283 and 284: Table 5.30. Calculated equilibrium
Page 285 and 286: m/m of 96% Table 5.32. Calculated e
Page 287 and 288: Table 5.33. Parameters of the Hailw
Page 289 and 290: CHAPTER 6. PROPERTIES OF THE SORBED
Page 291 and 292: where m is the equilibrium moisture
Page 297 and 298: 6.2 THE NUMBER OF ADSORBED MONOLAYE
Page 299 and 300: 6.3 TOTAL SOLID SURFACE AREA AVAILA
Page 301 and 302: Thus, for each cane component of ea
Page 303 and 304: abscissa. For each moisture level (
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A similar procedure was followed to
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10 0 Stalk fibre Stalk pith Rind fi
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Moreover, if T β > T hm the proces
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Table 6.5. Characteristic parameter
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Binding energy/kJ (kg mol) -1 2 0 0
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6.8 CALCULATION OF BOUND WATER AND
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The values of K 1 , K 2 and W were
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Table 6.7. Separation of the total
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Table 6.7. (Contd.) Sample 30 o C 4
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3 0 S talk fibre 4 0 Stalk pith 3 0
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3 0 Reconstituted cane at 30 o C 3
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when water is added to dry wood, wh
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It is evident that in some cases ma
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The number of adsorbed monolayers,
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Data in Tables 2.9 and 2.11 show th
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particular fibre is systematically
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Anon. (1985b). Laboratory manual fo
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Blanchi R.H. and A.G. Keller (1952)
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Day D.L. and G.L. Nelson (1965). De
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Heyrovsky J. (1970). Determination
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Kuhn I.J. (1964). A new theoretical
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Madamba P.S., R.H. Driscoll and K.A
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Prinsen Geerligs, H.C. (1897). Stud
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Sing K.S.W., D.H. Everett, R.A.W. H
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Van der Pol C., C.M. Young and K. D
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Lynne Wong's PhD thesis

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