Lynne Wong's PhD thesis

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full, the crystals are all of the same desired size. The crystals and syrup form a dense mass called massecuite, and the strike (the contents of the pan) is then discharged into a mixer or a crystallizer, where the crystals continue to grow. In the three-boiling system, the first boiling of raw syrup yields raw sugar and A molasses, which is returned to the vacuum pan to be reboiled on a "footing" of first-grade massecuite to a second massecuite (B) that in turn yields a second crop of crystals (B sugar). This is usually mixed with the A sugar forming the commercial output of the factory. The second or B molasses is in turn reboiled on a footing of syrup crystals to form C massecuite. The C sugar is mingled with syrup and used for A and B massecuite "seed". The final cane molasses contains approximately one-third sucrose, one-fifth reducing sugars, and the remainder, ash, organic non-sugars and water. It is used as cattle feed, and in the manufacture of alcohol and yeast. 1.2.7 Centrifugation The crystals in the massecuite are separated from the surrounding mother liquor (molasses) by centrifugal force in a machine called a centrifuge. It consists of a perforated drum or basket so arranged that it may revolve on a vertical shaft or axis called the spindle. The perforated basket is lined with a metal screen containing 400 to 600 perforations per square inch. The basket revolves at 1000 to 1800 rpm. The perforated screen retains the sugar crystals which may be washed with water or steam while the molasses passes through the lining. The raw sugar obtained is then sent to a dryer and cooled. 1.3 MEASURE OF CANE QUALITY The amount of sugar recovered from cane is highly dependent on the raw material processed. The next section examines the quality of cane received at the mills. The quality of cane received at Mauritian sugar factories has deteriorated in recent years to such an extent that the raw material appears more like a few cane stalks buried in extraneous matter, i.e. non-cane, which contains little sucrose and inflates the mass of cane processed. Extraneous matter in cane is defined as any material that is delivered to a sugar factory as part of the cane but which does not contribute to increasing the amount of sugar produced, or has the tendency to lower the purity of the mixed juice. Included in this classification 9
are: cane tops, dry and green leaves, soil, rocks, cane roots, etc. Cane top is defined as the top part of the cane stalk above the actively growing apical internode with attached green leaves. Some authors use the word “trash” as a collective term for all extraneous matter, or more frequently, as the dry leaves associated with cane stalks. To avoid confusion, the term extraneous matter will be used in this <strong>thesis</strong> as the collective name and its individual components, by their specific names such as tops, green leaves, dry leaves, soil, etc. The term trash, if used, will refer to the dry leaves associated with cane stalks. 1.3.1 Direct measure of extraneous matter in cane A method exists to determine directly the amount of extraneous matter in a cane supply. This is carried out on a consignment of 5-6 tonnes of cane after the separation of all noncane materials, i.e. trash, green leaves, tops and young shoots to determine their respective masses. The number of samples handled in a day is limited and the results obtained are far from being representative of the total mass of cane crushed during the day. As this method is too time-consuming and costly to be practicable, factories do not systematically determine extraneous matter in cane, and its exact level is therefore unknown. A more common practice nowadays is to use a smaller sample size of about 400 kg taken by a loader from a cane consignment. Fig 1.5 shows such a test being carried out with the removed non-cane placed on both sides and cleaned cane in the middle. Results obtained on a single cane consignment over a fortnight showed mean extraneous matter of 8.3% ranging from 4.7% to 11.5% at one factory, and 24.0% with a range from 17.2% to 34.0% at another factory (Wong Sak Hoi et al., 1999). In South Africa, Cargill (1976) described sampling and analytical procedures involving a grab sampler positioned next to a main cane carrier for estimating the amount of tops and trash in a cane consignment. A sample size of 100 kg is recommended (Anon., 1985b). Wong Sak Hoi et al. (1999) devised a rapid and reliable method of estimating extraneous matter in a cane consignment, by using grab samples of cane bundles containing about 40 cane stalks. The method was found to yield reasonably accurate estimate of extraneous matter in cane. Results obtained at one factory on sample involving 40 cane stalks taken from a consignment of 400 kg, was compared with the true value of the whole consignment. Statistical analysis of ten such paired-comparisons showed a mean coefficient of variation of 11.6. 10
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THE BRIX-FREE WATER CAPACITY AND SO
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dissolved and hydrated waters, and
Page 5 and 6: ACKNOWLEDGEMENTS I am particularly
Page 7 and 8: Page 1.5 THE DELETERIOUS EFFECTS OF
Page 9 and 10: Page 2.2 THE PHENOMENON OF BRIX-FRE
Page 11 and 12: Page 3.4.3.3 Cane tops 83 3.4.4 Cha
Page 13 and 14: 4.3.3 Temperature at which Brix-fre
Page 15 and 16: 4.6.1 Materials 143 4.6.1.1 Samples
Page 17 and 18: CHAPTER 6. PROPERTIES OF THE SORBED
Page 19 and 20: APPENDIX 3. CALCULATIONS LEADING TO
Page 21 and 22: LIST OF FIGURES Page Figure 1.1. Fi
Page 23 and 24: Figure 3.1. Glucose and fructose an
Page 25 and 26: Figure 5.11. Residual plots for the
Page 27 and 28: total adsorbed water (m) and the pr
Page 29 and 30: Table 2.18. Moisture content in sug
Page 31 and 32: Page Table 4.4. Results of the dete
Page 33 and 34: Page Table 4.24. Analysis of varian
Page 35 and 36: Page Table 5.13. Table 5.14. Equili
Page 37 and 38: Table 6.3. Heat of sorption of the
Page 39 and 40: GLOSSARY OF TERMS Absorption is the
Page 41 and 42: Filterability of a raw sugar is mea
Page 43 and 44: Sorption is the generic term used w
Page 45 and 46: LIST OF MAIN SYMBOLS Symbol Descrip
Page 47 and 48: s c s Slope of Caurie I isotherm pl
Page 49 and 50: number of 255, and cane land covere
Page 51 and 52: Nouvelle Mon In Trésor ustrie and
Page 53 and 54: Figure 1.3. Cane sampling by core s
Page 55: In Mauritius, most of the sugar fac
Page 59 and 60: 1.4 TRENDS IN CANE QUALITY RECEIVED
Page 61 and 62: campaign was launched to encourage
Page 63 and 64: The level of extraneous matter in c
Page 65 and 66: In Australia (Cargill, 1976), cane
Page 67 and 68: The effect of soil on factory perfo
Page 69 and 70: leaves increased the level of impur
Page 71 and 72: • From 1976 to 1980, when the pro
Page 73 and 74: Clerget purity of molasses 40 Clerg
Page 75 and 76: CHAPTER 2. IMPACT OF EXTRANEOUS MAT
Page 77 and 78: Since the extrapolated purity of mo
Page 79 and 80: Figure 2.1. Jeffco cutter grinder.
Page 81 and 82: 2.1.4 Results The analytical result
Page 83 and 84: Table 2.3. Analytical results of re
Page 85 and 86: Table 2.5. Composition of dry trash
Page 87 and 88: Table 2.7. Predicted factory perfor
Page 89 and 90: Boiling house recovery 91.0 89.8 89
Page 91 and 92: 0 5 10 15 20 % EM in cane y = 0.572
Page 93 and 94: % EM in cane 0 5 10 15 20 0 -2 -4 -
Page 95 and 96: 1 y = 0.020 (% D) R 2 = 1.00 = 0.03
Page 97 and 98: % EM in cane 0 5 10 15 20 0 -2 y =
Page 99 and 100: esulting in 0.015 unit sucrose loss
Page 101 and 102: 2.2.1 Experimental procedure Cane m
Page 103 and 104: filter paper, rejecting the first f
Page 105 and 106: 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/
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4.7.3 Statistical analysis It is es
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Table 4.23. Analysis of variance (B
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pointing out that at 52 weeks old,
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The crop of R 570 sampled in 2001 w
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4.7.4. Estimated Brix-free water co
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The main difference in the two sets
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Table 4.27. Predicted Brix-free wat
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4.8 SUMMARY AND CONCLUSIONS An anal
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component parts, and verify the Bri
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3) Thermodynamic, water in equilibr
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Langmuir (1916, 1917, 1918) propose
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to determine the moisture sorption
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Table 5.1. Some commonly used isoth
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Lomauro et al. (1985) found that wi
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and on agricultural products such a
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Bruijn (1963) studied the mass incr
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After measuring the EMC of dry corn
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approached, that is, either by adso
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Table 5.4. Water activity (a w ) of
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5.6.3 Procedure to determine equili
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5.6.4 Results and discussion An exa
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Table 5.8. Equilibrium moisture con
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Table 5.10. Equilibrium moisture co
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Table 5.12. Equilibrium moisture co
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30 o C 45 o C 55 o C 60 o C Water w
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m/m of 96% activity, a w (g/100g dr
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vaporisation generally decreases fr
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30 o C isotherm 45 o C isotherm 55
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4 0 Stalk fibre 5 0 Stalk pith 5 0
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5.6.4.4 Fitting of sorption models
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Table 5.19. Parameters of the sorpt
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Modified GAB Kuhn Iglesias - Chirif
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Table 5.28. Classification of resid
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Stalk fibre Stalk pith Rind fibre 4
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5.6.4.5 Calculated EMC values of re
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Table 5.30. Calculated equilibrium
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m/m of 96% Table 5.32. Calculated e
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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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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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