Lynne Wong's PhD thesis
Lynne Wong's PhD thesis Lynne Wong's PhD thesis
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 thesis 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
- 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
are: cane tops, dry and green leaves, soil, rocks, cane roots, etc. Cane top is defined as the<br />
top part of the cane stalk above the actively growing apical internode with attached green<br />
leaves. Some authors use the word “trash” as a collective term for all extraneous matter, or<br />
more frequently, as the dry leaves associated with cane stalks. To avoid confusion, the<br />
term extraneous matter will be used in this <strong>thesis</strong> as the collective name and its individual<br />
components, by their specific names such as tops, green leaves, dry leaves, soil, etc. The<br />
term trash, if used, will refer to the dry leaves associated with cane stalks.<br />
1.3.1 Direct measure of extraneous matter in cane<br />
A method exists to determine directly the amount of extraneous matter in a cane supply.<br />
This is carried out on a consignment of 5-6 tonnes of cane after the separation of all noncane<br />
materials, i.e. trash, green leaves, tops and young shoots to determine their respective<br />
masses. The number of samples handled in a day is limited and the results obtained are far<br />
from being representative of the total mass of cane crushed during the day. As this method<br />
is too time-consuming and costly to be practicable, factories do not systematically<br />
determine extraneous matter in cane, and its exact level is therefore unknown. A more<br />
common practice nowadays is to use a smaller sample size of about 400 kg taken by a<br />
loader from a cane consignment. Fig 1.5 shows such a test being carried out with the<br />
removed non-cane placed on both sides and cleaned cane in the middle. Results obtained<br />
on a single cane consignment over a fortnight showed mean extraneous matter of 8.3%<br />
ranging from 4.7% to 11.5% at one factory, and 24.0% with a range from 17.2% to 34.0%<br />
at another factory (Wong Sak Hoi et al., 1999).<br />
In South Africa, Cargill (1976) described sampling and analytical procedures involving a<br />
grab sampler positioned next to a main cane carrier for estimating the amount of tops and<br />
trash in a cane consignment. A sample size of 100 kg is recommended (Anon., 1985b).<br />
Wong Sak Hoi et al. (1999) devised a rapid and reliable method of estimating extraneous<br />
matter in a cane consignment, by using grab samples of cane bundles containing about 40<br />
cane stalks. The method was found to yield reasonably accurate estimate of extraneous<br />
matter in cane. Results obtained at one factory on sample involving 40 cane stalks taken<br />
from a consignment of 400 kg, was compared with the true value of the whole<br />
consignment. Statistical analysis of ten such paired-comparisons showed a mean<br />
coefficient of variation of 11.6.<br />
10
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