Lynne Wong's PhD thesis
Lynne Wong's PhD thesis Lynne Wong's PhD thesis
Lionnet (1996) explained that for pol % cane, there was a slow decrease over the years until about 1987 when a strong recovery took place. This was unfortunately stopped by the droughts which lasted from 1992 to 1995. Fibre % cane shows a clear decrease from 1983 onwards due to harvesting of younger cane with the incidence of the Eldana borer, which tends to affect older or carry-over cane. Lionnet (1996) also noted that an improvement in mixed juice purity (see Fig 1.9) started in 1985, except for the drought years of 1992-1995. Compared to the trends of fibre % cane and sucrose % cane in Mauritius (see Fig 1.6), those in South Africa (refer to Fig 1.8) do not show great changes over the years, although a downward trend in fibre % cane and an upward trend in sucrose % cane are evident as from 1985 onwards (except for the drought years). It is worth pointing out that while the values of sucrose % cane and sucrose/fibre ratio in cane are comparable in the two countries, this is not the case with the fibre % cane data. In Mauritius, fibre % cane was stable at 13.2 up to 1975, and gradually increased to about 15.0, whereas in South Africa, it averages 15.3% over the years. Purity of mixed juice is higher in Mauritius; it averages 86.7%, whereas in South Africa it is 85.6%. Numerous literature exists on trends in cane quality. Clayton and Roberts (1971) stated that in Florida, the trash content of cane just before harvest is about 30%. Kampen (1974) had shown that extraneous matter in Louisiana cane was very much dependent on cane variety and the harvest method used, and it had gradually increased from less than 1% in 1945 to more than 13% in the early 1970s, with total mechanization of field operations since 1950. Legendre and Irvine (1974) reported that when hand cutting, stripping and loading were practised in Louisiana prior to 1942, the amounts of extraneous matter rarely exceeded 4%; by 1947, when mechanical harvesting had become predominant, the total extraneous matter level had nearly doubled. In Puerto Rico, Cabrer et al. (1965) estimated that as high as 25% of cane crushed consists of tops, trash, sand and other extraneous matter while in South Africa, according to Smits and Blunt (1976), the amount may be about 12% or more during rainy periods. Lamusse and Munsamy (1979) reported that after measuring tops and trash at five factories in South Africa during the whole season, the cane was found to contain on average 2.1% tops and 5.3% trash; de Beer et al. (1989) carried out an experiment with 800 tonnes of cane, and found that unburnt, untopped cane contained 22.2% extraneous matter whereas burnt, topped cane, contained only 3.2%. 17
In Australia (Cargill, 1976), cane quality was defined according to the content of extraneous matter in the cane: from 0 – 3% acceptable, 4 – 5% poor, and > 6% very poor. Cargill (1976) also reported that trials carried out in Cuba for five consecutive seasons showed that extraneous matter in green cane harvested and loaded manually amounted to 3%, and in green cane harvested manually and loaded mechanically, 4%. He also reported that in Louisiana, whole stalk green cane harvested mechanically contained 8% extraneous matter. In Mauritius, due to shortage of labour, when grab loading of manually harvested cane was resorted to in 1975, as much as 15% extraneous matter, including tops, trash, soil and rocks were reported (d’Espaignet, 1977). St Antoine (1977) first raised the alarm on the deteriorating quality of cane received at Mauritian factories. From these trends it can be seen that steps must be taken to improve the cane quality received at Mauritian mills. Cane quality has deteriorated worldwide, however, Mauritius is at the higher end and this poses a number of deleterious effects which are enumerated in Section 1.5. 1.5 THE DELETERIOUS EFFECTS OF EXTRANEOUS MATTER ON CANE PROCESSING The adverse effects of sand and trash on milling have been explicitly described by Graham and Gunn (1971), and by Kent et al. (1999), and on milling and boiling house performance by Smits and Blunt (1976). St Antoine (1977) discussed the effect of cane quality on the efficiency of sugar factories. Lamusse and Munsamy (1979) examined the effect of trash on mills and diffuser performance, and Clarke and Legendre (1996) described the impact of cane quality on the yield and quality of the sugar produced. Lionnet (1992a, 1996) reviewed some aspects of cane quality in South Africa and its effects on factory performance. 1.5.1 Effects of soil on cane processing Dirt or field soil is not desirable in cane, but some is inevitable, especially with mechanical harvesting and loading systems operating in wet conditions. A fair amount of soil finds its way into processing causing clarification and filtration problems. A number of process difficulties have been attributed to the detrimental effect of soil: higher turbidity of 18
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In Australia (Cargill, 1976), cane quality was defined according to the content of<br />
extraneous matter in the cane: from 0 – 3% acceptable, 4 – 5% poor, and > 6% very poor.<br />
Cargill (1976) also reported that trials carried out in Cuba for five consecutive seasons<br />
showed that extraneous matter in green cane harvested and loaded manually amounted to<br />
3%, and in green cane harvested manually and loaded mechanically, 4%. He also reported<br />
that in Louisiana, whole stalk green cane harvested mechanically contained 8% extraneous<br />
matter.<br />
In Mauritius, due to shortage of labour, when grab loading of manually harvested cane was<br />
resorted to in 1975, as much as 15% extraneous matter, including tops, trash, soil and rocks<br />
were reported (d’Espaignet, 1977). St Antoine (1977) first raised the alarm on the<br />
deteriorating quality of cane received at Mauritian factories.<br />
From these trends it can be seen that steps must be taken to improve the cane quality<br />
received at Mauritian mills. Cane quality has deteriorated worldwide, however, Mauritius<br />
is at the higher end and this poses a number of deleterious effects which are enumerated in<br />
Section 1.5.<br />
1.5 THE DELETERIOUS EFFECTS OF EXTRANEOUS MATTER ON CANE<br />
PROCESSING<br />
The adverse effects of sand and trash on milling have been explicitly described by Graham<br />
and Gunn (1971), and by Kent et al. (1999), and on milling and boiling house performance<br />
by Smits and Blunt (1976). St Antoine (1977) discussed the effect of cane quality on the<br />
efficiency of sugar factories. Lamusse and Munsamy (1979) examined the effect of trash<br />
on mills and diffuser performance, and Clarke and Legendre (1996) described the impact<br />
of cane quality on the yield and quality of the sugar produced. Lionnet (1992a, 1996)<br />
reviewed some aspects of cane quality in South Africa and its effects on factory<br />
performance.<br />
1.5.1 Effects of soil on cane processing<br />
Dirt or field soil is not desirable in cane, but some is inevitable, especially with mechanical<br />
harvesting and loading systems operating in wet conditions. A fair amount of soil finds its<br />
way into processing causing clarification and filtration problems. A number of process<br />
difficulties have been attributed to the detrimental effect of soil: higher turbidity of<br />
18
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