Lynne Wong's PhD thesis

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Figure 5.3. The McBain spring adsorption balance (McBain and Bakr, 1926). The most commonly used modern methods for determining the equilibrium moisture content can be classified into three categories: gravimetric, either static or dynamic; manometric and hygrometric (Gal, 1981). 5.5.1 Gravimetric method The gravimetric method involves the measurement of mass changes, which can be determined either continuously or discontinuously in static or dynamic systems. Continuous methods employ the use of electro-balances or quartz spring balances. In the discontinuous systems, salt or sulfuric acid solutions are placed in vacuum or atmospheric systems with the test sample, to give a measure of the equilibrium relative humidity. A simple static procedure is to place a number of pre-dried samples in ordinary laboratory desiccators containing saturated salt solutions or sulfuric acid solutions of known concentrations which produce atmospheres of known relative humidity. The desiccators are maintained at constant temperature. The sample in each desiccator is weighed periodically until a constant mass is reached. The moisture content at this constant mass represents the EMC under those particular conditions of relative humidity and temperature. The EMC value of many materials depends on the direction in which the equilibrium is 185
approached, that is, either by adsorption to constant mass or desorption of the moisture at 105 °C after adsorption. A higher value is obtained when a wet material loses moisture by desorption than when a dry material gains it by adsorption (McMinn and Magee, 2003; Al- Muhtaseb et al., 2004b; Arslan and Toğrul, 2005), in which case, the material is said to exhibit hysteresis. In the dynamic method, air is moved mechanically and is often moistened by air conditioning units (Brooker et al., 1992; Viswanathan et al., 2003). The pre-dried sample may be placed in a U-tube through which is drawn a continuous flow of controlledhumidity air. The equipment is maintained at constant temperature. Again the sample is weighed periodically until a constant mass is reached. 5.5.2 Manometric method The manometric method measures the vapour pressure of water in the vapour space surrounding the test sample. The whole system is maintained at constant temperature and the test sample will lose water to equilibrate with the vapour space. This will be indicated by the difference in height on the manometer (Gal, 1981). 5.5.3 Hygrometric method The hygrometric method measures the equilibrium relative humidity of air in contact with the test sample, at a given moisture content. Dew-point hygrometers detect the condensation of cooling water vapour. Electric hygrometers measure the change in conductance or capacitance of hygrosensors. Most hygrosensors are coated with a hygrocopic salt, such as lithium chloride, which absorbs moisture from the test sample (Gal, 1981). 5.6 DETERMINATION OF ADSORPTION ISOTHERMS FOR COMPONENT PARTS OF CANE VARIETY R 570 The aims of the work described in this chapter were (i) to determine the water adsorption for the fibres of nine component parts of variety R 570 of two ages (52 and 36 weeks) at four temperatures (30, 45, 55 and 60 °C) by means of a static method (ii) to model the sorption behaviour by testing the goodness of fit of 17 commonly used models and (iii) to evaluate the constants of the isotherm models. 186
Page 1 and 2:
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
Page 187 and 188: By means of the same technique, Won
Page 189 and 190: was still hot. Since the filter was
Page 191 and 192: value determined could be corrected
Page 193 and 194: Qin and White’s finding was confi
Page 195 and 196: A sample size of 3.5 g with 75 g co
Page 197 and 198: Figure 4.4. Fibre samples drying in
Page 199 and 200: - One large fibre sample (rind) of
Page 201 and 202: Table 4.18. Brix-free water values/
Page 203 and 204: 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: After measuring the EMC of dry corn
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 and 256: m/m of 96% activity, a w (g/100g dr
Page 257 and 258: vaporisation generally decreases fr
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
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CHAPTER 6. PROPERTIES OF THE SORBED
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where m is the equilibrium moisture
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Stalk fibre Stalk pith Rind fibre 8
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6.2 THE NUMBER OF ADSORBED MONOLAYE
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6.3 TOTAL SOLID SURFACE AREA AVAILA
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Thus, for each cane component of ea
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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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