FIFTY-SEVENTH ANNUAL REVIEW OF THE MILLING SEASON IN SOUTHERN AFRICA ( )

Transcription

1 Proceedings of The South African Sugar Technologists' Association - June 1982 FIFTY-SEVENTH ANNUAL REVIEW OF THE MILLING SEASON IN SOUTHERN AFRICA ( ) By J P LAMUSSE Sugar Milling Research Institute Abstract Data for the season on cane quality, sugar production and performance of sugar factories,in South Africa, Swaziland, Zimbabwe and Malawi are listed and discussed The season started in the aftermath of a very severe drought, but good rains in winter gradually increased the size of the crop However the rains had an adverse effect on pol TO cane, and the cane to sugar ratio of 9,50 was the highest since 1934 Introduction This review covers laboratory data and factory performance of all the sugar mills in South Africa, Swaziland, Zimbabwe and Malawi The data listed in the tables have been calculated from figures reported by the mills except for sugar weights which were obtained from the South African Sugar Association and cane varieties and transport data which were supplied by the Central Board The paragraphs on Weather and Cane Varieties were written by contributors from the SASA Experiment Station Although the format of the tables and the parameters listed are almost identical to those of the previous season, the data for South African mills which are based on mixed juice or molasses analysis have been converted to a sucrose basis using pol to sucrose ratios determined by gas chromatography (GC) This does not apply to data from the mills in neighbouring countries (tables Bp, C, and D,) and it invalidates comparison of recoveries and losses between the two sets of tables A key to the symbols used to designate South African mills will be found in Table A The symbols for the mills in the neighbouring countries are listed below : MH Mhlume in Swaziland UR Ubombo Ranches in Swaziland SM Simunye in Swaziland NH Nchalo in Malawi DW Dwanga in Malawi HV Hippo Valley in Zimbabwe TR Triangle in Zimbabwe Highlights of the Season South Africa The season started late in the aftermath of a devastating drought and a severe attack of Eldana borer on the North Coast and in Zululand Good rains early in the season, and the decision d many North Coast and Zululand farmers to cut as much of their cane as possible to control the spread of Eldma, gradually altered the picture and most mills had a long season The last mill to shut down, DL, only stopped crushing on the 16th March, 1982, and we have to go back to 1971 for a season which ended as late ( ) An extreme case of the variation of the cane estimates as the season progressed was provided by EM This mill expected a very poor crop and therefore started at a low crushing rate, and had planned to stop for one or two months in mid-season It turned out that EM had a long season of 277 days and only stopped on the 24th January 1982 after crushing tons of cane Industrial average cane quality was very poor Table J shows that pol % cane (12,20) and sucrose % cane (12,30) were both the lowest ever recorded since 1945, while fibre % cane (16,13) was exceptionally high Fortunately mixed juice purity (85,67) was above the average for recent years The season was marked by unsettled labour conditions which resulted in a number of strikes by factory workers at various mills Industrial action contributed to a lowering of overall time efficiency to 77,45'?40 but average crushing rate increased to 233,87 tch The factory performance of the various mills covered a very wide range, but average extraction (97,02) was the best ever achieved by the South African mills Boiling house recovery (87,75) was, however, disappointingly low As a result of the combination of poor cane quality and low recovery, 950 tons of cane were required to produce a ton of sugar, the highestcane to sugar ratio recorded since 1934, even when changes in pol of sugar are taken into consideration Swaziland Pol % cane was lower than for the previous season at all three mills in Swaziland (MH: 12,65, UR: 12,89, SM: 11,80) The low value reported by SM is attributed to the high proportion of plant cane crushed by the mill Fibre % cane and mixed juice purities were about the same at the first two mills but were considerably lower at SM Total cane crushed in Swaziland was tons from which tons of sugar were produced at an average cane to sugar ratio of 9,23 The sugar production was 12,8% higher than last season SM reported a very good extraction (97,61), MH a high boiling house recovery (90,01), and the overall recovery of both MH (86,ll) and SM (85,62) was higher than for the previous season UR had a very good time efficiency (84,65) in contrast to the low value reported by SM (61,91) which suffered severely from lack of cane Zimb,gbwe The two mills in Zimbabwe processed tons of cane and would have produced about tons of sugar (assuming a cane to sugar ratio of, 8) if all the cane had been used to make sugar The theoretical production would have been 12,5% higher than for the previous season Triangle (TR) produced both sugar and anhydrous alcohol for mixing with petrol Their process is flexible but consists basically in fermenting the A molasses and part of the secondary juice into alcohol The ethanol plant was operated at higher than design capacity during the season without problems Hippo Valley's season was probably a world record or very near to one The mill produced tons of raw sugar at a cane to sugar ratio of 805 or 7,83 when converted to 96 pol sugar Overall time efficiency was 88,04

2 Proceedings of The South African Sugar Technologists' Association - June 1982 and total crushing rate 423,53 tch The two cane diffusers achieved an average extraction of 97,36 and the boiling house recovery was very high (90,37) Malawi Malawi's sugar production reached a record of tons The increase of 13,470 was due to a higher sugar production at DW (70426 tons) This factory is a good example of the remarkable flexibility in throughput which has been a traditional feature of sugar mills It was designed for 150 tch and in its second year in normal operation it averaged 182 tch Cane quality in Malawi was good by South African standards with a pol % cane d 13,47 at NH and 13,92 at DW Factory performance was relatively poor at both mills but their cane to sugar ratios (NH: 8,75, DW: 8,70) were still appreciably lower than the South African average The Weather* The period under review was yet again characterised by long spells of less than average rainfall, punctuated by widely spaced heavy falls of rain concentrated over a few days March and April, 1981 received only 38% and 50% respectively of their rainfall averages, and areas of moisture stress were showing on the shallower soils at this time Rainfall during May was 242% of the long term mean, rainfall in June was average while that in July was only 70% of the long term mean Heavy rains in the last few days of August turned this month into one of very high rainfall, and it seemed that winter and spring 1981 heralded a better season However, the next three months were again dry with 51%, 104% and 57% of the long term mean being recorded respectively By February 1982 increasing crop stress was again being reported from all parts of the industry, particularly from the North Coast and Midlands, and the rivers supplying the northern irrigated areas were not flowing strongly Although temperatures were normal during the summer months for the period under review, winter in 1981 was cooler than usual The Midlands region reported frequent frosts in June, but no serious damage was observed At the end of February 1982, comment from all parts of the industry concerning the past season was that growing conditions had not been optimum, but were a considerable improvement on the previous year Cane Varieties* The amount of NCo 376 in the annual cane crush has again increased slightly and this variety now accounts for 71,8% of all cane milled in Sodh Africa The increase * By the Extension Staff, SASA Experiment Station *By R S Bond, SASA Experiment Station in the quantity of NCo 376 was at least partly due to the replacement of NCo 310 by NCo 376 in the Umfolozi and Felixton mill areas NCo 310 rapidly declined in popularity in the northern irrigated areas during the early seventies, due to its susceptibility to smut Smut appeared to be less prevalent in the Umfolozi area at this time and NCo 310 persisted as the favoured variety However, during the last 5 or 6 years a serious smut problem has developed in the area and growers are finally turning away from NCo 310 NCo 293 continues to be the most popular variety grown in the two midland mill areas, where it is considered more drought and cold tolerant than NCo 376 Yield trials have failed to show any yield advantage for NCo 293 over NCo 376 in these areas, and it is acknowledged that NCo 293 ratoons poorly if cut in winter All the new varieties released since 1975 have shown a slight increase in the amount of cane crushed while more growers try them out under their own field conditions However, in Swaziland where the smut resistant variety N52/ 219 is the second most widely grown variety after NCo 376, there has been a slight decrease in the amount of N52/219 crushed The variety does not do well under poorly drained conditions and is not a strong ratooning variety Cane Quality When judged' by the traditional parameters of pol % cane, fibre % cane and mixed juice purity, the cane supplied to South African mills during the season was d very poor quality If extraneous matter in cane is also taken into consideration, Table l8 shows that there was a deterioration over the previous four seasons for which data are available Since cane quality is the most important factor affecting the performance of South African mills, seasonal changes in each of the quality parameters will be discussed below Pd 70 cane Table J shows that the average pol % cane and sucrose % cane for the season (12,20 and 12,30 respectively) were the lowest since 1945 The lowest pol values were reported by the North Coast and Zululand coastal mills and the highest by the South Coast where UK had a season average of 13,03 High pol values were also reported by EN and GD which both logged 12,94 GD attributes its good results to the successful use of ripeners at the beginning of the season (Figure 1) and to comparatively clean cane A noticeable feature of the season was that the sugar content of cane increased slowly during the beginning of the season but remained at a high level from August almost to the end of the season This was particularly noticeable on the North Coast and in Zululand (Figure 1) Fibre % cane and ash % cane These two parameters are considered together because fibre % cane includes not only the vegetable fibre in the 1 EM 1 TABLE 1 Extraneous matter in cane ( Season) Huletts Mills PX AX DL ME Group Average Trash % cane 7,3 5,02 4;69 5,16 Tops % cane Ash % cane

3 Proceedings of The South African Sugar Technologists' Association - June i - - 'GD,---- DL - lnd Ave 4 Extraneous matter in cane The high sand content of cane has already been commented on under fibre O/o cane, but Table I shows that the percentage of both tops and trash has increased for the Huletts mills from 1980 to 1981, when it averaged 5,1670 for trash and 2,25% for tops for the group At DL the tops and trash added up to 9,5% which represented tons of extraneous matter for the season DL was the last mill to finish the season in mid-march, and during its last four weeks it crushed a tonnage of cane roughly equivalent to the weight of extraneous matter supplied to the mill during the season 101 MAY JULY SEPT NOV JAY Month FIGURE 1 Changes in monthly sucrose % cane during the season plant but also all other insoluble matter such as sand and soil Reference to table J will show that the fibre $6 cane (16,13) was the highest reported since 1953 (16,3 1) The drought during the early part of 1981 and Eldana damage are probably responsible for desiccation of the cane, which was specially noticeable on the North Coast where TS and GH reported season average values of over 17 It is suprising however that the fibre content of cane was higher than the season average (15,95) when the effect of both the drought and of Eldanh damage were much more noticeable One can only postulate that this may be due to an increase in the sand and soil content of cane supplied to the mills There is no direct measure of soil in cane, but ash % cane is a good reflection of its concentration Table 1 shows that, for the Huletts mills, ash OJo cane was at its highest during the past season (1,69), an increase of 0,29 over the value for 1980/81 while the industrial average increase was also 0,29 The comparative increase in industrial average fibre % cane between the two seasons (0,18) can therefore be explained by the increase in its inorganic constituents EM (2,33) and UC (2,36) reported the highest ash % cane values in South Africa and the lakter mill, which had a weekly average of 5,28 for the last week of November, estimates the damage done by sand in cane to conveyors, piping, boiler tubes etc at about R for the season 3 Mixed juice purity Industrial average apparent mixed juice purity (84,94) was relatively high, being 0,14 points higher than for the previous season The corresponding sucrose purity was 8567 and the pol-to-sucrose ratio in mixed juice averaged 0,9915 with values ranging from 0,9862 at ML to 0,9945 at GH Sugar Production and Quality The South African sugar production' (Table A) totalled tons, an increase d tons over the season but still tons short of the record AK had the highest sugar production with tons and two other factories (TS and SZ) also made more than tons of sugar, while only 6 factories produced less than tons The six backend refineries (ML, PG, UF, EN, GH and SZ) produced a total of tons of refined sugar, which was roughly half the total refined sugar production of the country, the other half having been made by Huletts Refinery in Durban There has been a distinct deterioration in fines content of raw sugar Figure 2 shows the increase in fines percent sugar supplied to the Terminal during the past eleven years According to specifications, the percentage of fines should not be above 25%; last season they averaged 29% These figures, together with the increase in fines in C-sugar which is discussed under boiling house, indicate a deterioration in pan work in most factories n YEAR FIGURE 2 Fines % raw sugar supplied to sugar terminal Ti Efficiency and Crushing Rate In spi,te of the fact' that some mills started the season at reduced throughput in anticipation of a small crop, the average hourly crushing rate of tons of cane and 3596 tons of fibre were the highest ever recorded in South Africa Timeefficiency % scheduled stops %lack of cane stops %otherstops TABLE 2 Percent stops to ,67 8,92 3,41 9, ,45 10, ,54 79, ,30 7,11 79,24 8,92 3,84 8,00 75, ,08 10,49

4 14 Proceedings of The South African Sugar Technologists' Association - June 1982 Unfortunately, time efficiency which had been rising steadily for the past five years, fell from 79,02 in to 77,45 in Table 2 shows a breakdown of lost time for the past five seasons There was a noticeable increase in scheduied stops (10,46%) and in stops for lack of cane (4,5570) In the first case, the increase was due mainly to the inclusion in scheduled stops of time lost due to industrial disputes; 1981 was the first year during which strikes by factory workers had an appreciable influence on time efficiency The increase in stops for lack of cane was due mainly to unseasonal winter rains during the first months of the season An exceptionally high value (11,57) was reported by ML Other stops, which include both mechanical and operational stops, averaged 7,54 compared with 7,11 in 1980 and 8,00 in 1979 The range of values reported by the different mills is surprisingly large with extreme values of 2,26 and 13,71 for EM and EN respectively UC deserves special mention for having been able to complete the season with an average time efficiency of 74% and a lost time percent available of 13,24 in spite of having had to replace most of its factory work force by untrained workers less than a month before the stafi of the season as a result of an industrial dispute Cane Preparation and Extraction was another exceptional season for extraction It was the first time that the industrial average extraction broke the 97 barrier to establish a new record at 97,02 The performance of individual extraction plants are listed in Table 3 The results at DL have been outstanding with a season average extraction of 98,24 which is probably a world record and a maximum weekly average extraction of 98,58 This exceptional performance is attributed by the factory management to a combination of good mechanical efficiency, good roller arcing, reasonably good cane and a high imbibition level (342% fibre) Inspection of Table 3 shows that fifteen extraction plants reported extraction levels of over 97, nine were between 97 and 96, and eight below 96 Moisture content of bagasse for the first group of fifteen ranged from a low of 47,39 for HV (B) to 55,91 for TS (A) and the influence of bagasse moisture on extraction is illustrated by the figures listed for the two extraction plants at HV Both tandems have identical cane diffusers with the same preparation index (93) and almost identical imbibition rates Pol TO bagasse was 1,21 for the A tandem and 1,29 for the B tandem and the main difference between the two was 1,12 points in moisture content which contributed to a difference of 0,27 points in extraation Once again EM (bagasse diffuser) with an imbibition % fibre of 296 and ME (mills) with 239, have shown that a high level of extraction (97,16 and 97,49 respectively) can be obtained at relatively low imbibition rates, while FX improved its average extraction from 95,75 in 1980 to 96,43 in 1981 in spite of a reduction in imbibition 70 fibre from 314 to 308 The commissioning of a cane diffuser in mid-season at IL brought the number of diffusion plants in South Africa to ten with a larger cane tonnage now being processed by diffusers than by mills Initial problems caused by intercarriers and difficulties in maintaining operating temperatures in the diffuser were gradually soaed out, but the change in process had a noticeable effect on juice and sugar colour when processing poor quality cane A new cane preparation plant with a rubber belt feeding knives counter rotating against an anvil bar, was successfully wmmissioned'at SZ It forms part of a completely Factory DL SM TS(B) HV(B) ML ME EN GH(B) TS(A) HV(A) GH(A) PG EM UC NB UK MH(A) SZ(B) AK UF FX(A) Fx(B) NH(B) NH(A) 1 TR(A) TR(B) IL DW MH(B) UR GD TABLE 3 Extraction Plant Performance Season 1 Extr 98,24 97,61 97,s 97,50 97,50 97,49 97,49 97,42 97,33 97,28 97,22 97,16 97,16 P7,16 97,Ol 96,96 96,91 96,77 96,65 96,59 96,53 96,45 96,40 96,08 95,92 95,87 95,55 95,12 94,96 94,79 94,60 94,20 Pol % Bagasse -- 0,64 1,12 0,93 0,81 1,21 1,02 0, ,97 0,81 1,29 0,95 1,16 0,92 1,09 1,27 1,40 1,35 1,26 1,22 1,28 1,28 1,28 1,68 1,64 1,66 1,72 1,79 2,04 2,18 2,28 2,47 Moist % Bagasse 51,111 52,80 50,27 53,02 47,39 52,115 49,70 50,47 49,82 55,91 48,51 49,18 50, ,24 51,41 48,84 50,96 51,82 51,35 55,112 50,53 49,41 49,27 52,54 51,88 52,37 53,96 49,92 51,36 50,07 52,Ol Imb % Fibre new extraction plant which will be in operation during the 1982 season EN also reported improved preparation following the increase in knives' tip thickness from 20 to 32 mm and the installation of a new turbine drive on the cane knives Interesting developments in milling were the conversion of mill grooving from 50 to 60 mm with tooth angles reduced to 30' on all top rollers at UR which was reported to have improved mill capacity At NB a reduction in moisture was obtained by cutting 4 mm Meeschaert grooves in the discharge roller of the last mill, while SM reports favourably on their intercarriers which are hinged in the centre and can be swivelled vertically for easy access to the back rollers Clarifi&tion and Filtration Unseasonal rain in May hterfered with clarification and several mills on the North Coast and Zululand reported that clarified juice was clear but ink black in colour Fortunately this occurred only over a very limited period After the occurrence of rain early in the season, GH on the North Coast and NH in Malawi experienced very high gum content in clarified juice At GH this was limited to only a few cane consignments but it was very widespread at NH and several thousand tons of cane had to be rejected These gums are known to be of microbiological origin and, in Malawi, have been found to occur when delay between cane cutting and milling occurs because of rain No satisfactory method for the reduction of the gum level in factory products has been found so far The problems discussed above, and the gradual deterioration in clarified juice quality as a result of having to process dirtier cane, have led to more attention being paid to PI

5 Proceedings of The South African Sugar Technologists' Associarion - June the clarification and filtration stations The following developments took place during the season (a) Pilot plant attempts at filtrate clarification by flotation at NB which yielded encouraging results, and will probably be continued in another of the Smith group mills during the next season (b) A new saccharate liming ins~tallation at GH which proved helpful in dealing with the clarification difficulties mentioned above (c) The complete automation of the filters and of DSM screen washing at DL (d) The successful use of a plate heat exchanger for mixed juice and clear juice heating at UC (e) Succesful factory scale trials in the use of a smuts and bagacillo mixture as filter aid for mud filtration at SZ (f) Chemical cleaning of juice heaters using caustic soda at UF The heaters were not brushed during the season (g) The commissioning of an automatic lime slaker and a new SRI clarifier at IL A't this last mill, the change over from straight milling to cane diffusion, in the middle of the season, provided a good measure of the effect of the two extraction processes on clarification and filtration Filter cake % cane was 5 for the month of August when the factory was still on straight milling, and it dropped to 0,5 for December with cane diffusion Boiling House As mentioned earlier in this report, this is the first season since 1971 that boiling house recovery data are based on sucrose and not on pol The season's values are thereforenot comparable to those of previous years It should also be noted that the recoveries of mills in neighbouring countries are still based on pol The industrial average sucrose-based boiling house recovery was 87,75 The highest value in South Africa was reported by GD with 89,06 On a pol basis, GD's boiling house recovery was 89,93 which compares well with MH (90,Ol) and HV (90,37) There is no doubt that the high juice purity at GD (8788) has influenced its good boiling house performance, and the old parameter "Reduced Boiling House Recovery", (RBHR) which, in spite of its limitations, recalculates recovery to 85 mixed juice purity, has been used to compare all South African factories in Table 4 On the basis of RBHR, GD drops from first to fourteenth position while UC and AK move into first and second place respectively Target purity differences have been listed in the same Table It is well known that a low final molasses purity, like a high mixed juice purity, will increase the boiling house recovery but Table 4 presents a disturbing picture Some of the mills with the best boiling house recoveries (typically UC, SZ, TS) report relatively high target purity differences (TPD) Statistical studies carried out during the season have shown that the SMRI target purity formula which is based upon the Lane and Eynon method has a built in error and it will be replaced as from the next season by a new GC sucrose based reference purity formula (RPD), developed by Huletts, which is more accurate Unfortunately the 'observation made above about TPD boiling house recovery also applies to RPD and fears have been expressed that an over-emphasis on target purity may have a detrimental effect on recovery A reliable reduced boiling house recovery is needed as the 'main target for boiling house work In spite of considerable investment in boiling house equipment there has been a disappointing lack of progress in boiling house recovery during the past years, which is generally blamed on cane quality It is becoming evident that with the present process only marginal improvements in boiling house performance can be expected An attempt has been made to break through the barrier by clarification of boiling house products At EM, syrup was clarified by flotation during part of the season and, although an improvement in sugar quality was noted, the process had no apparent effect on boiling house recovery B-molasses clarification by phosphatation, followed by flotation, was tried at NB It reduced B-molasses viscosity by about thirty percent but it has still not been proved that this benefit can be transformed into a higher boiling house recovery with existing boiling techniques, Factory UC AK SZ TS NB FX ME ML UK EM GH DL EN GD UF IL PG TABLE 4 Boiling House Work - South African Mills 1981/82 Season Reduced BHR 89,8 88,3 88,2 88,l 87,7 87,7 87,s 87,4 86,7 86,6 86,s 86,3 86,l 86,O 86,O 84,7 84,4 Boiling House Recovery 88,7 88,l 88,7 88,5 88,O 88,3 87,9 87,4 88,4 85,8 87,9 87,9 87,2 89,O 87,l 86,8 85,l Target Purity Differences (TPD) 2,4 0,9 1,6 ],8 0, ,3 2,3 2,7 1,1 1,3 2,s 28 1,o %I 1,8 Reference Purity Differences (RPD) ,6 3,3 4,2 43 2,3 3,4 4,4 3,4 4,8 5,4 3,6 3,9 5,6 58 3,7 7,2 4,o Investigations carried out in a number of factories in connection with the optimisation of continuous centrifugal operations, have revealed very high physical loss of crystals into final molasses which, on average, caused an increase in final molasses purity of about four points, and which are bound to have had an adverse effect on boiling house recovery The small crystals which pass through the screen can be traced back to the C-pans where there appears to have been a deterioration in the quality of massecuite, which is probably due to the boiling of smaller-size crystals At GD a successful attempt was made to reverse this trend during the season by modifying the graining procedure An immediate improvement in boiling house recovery was noted The season has seen a confirmation of the trend to continuous pans with two new units commissioned at IL, one on B-massecuite'and the other on C massecuite, and the conversion of a batch A-pan at AK to continuous operation with limited success With several more units on order, there is no doubt that continuous pans are here to stay, and they have proved very reliable in operation There is however considerable speculation in the industry on the optimum design of these pans to improve massecuite circulation and heat transfer and to reduce massecuite scaling of heating surfaces

6 16 Proceedings of The South African Sugar Techno1og;ists: Association -June 1982 Centrifugals have been the subject of a lot of attention in 1981 and improvements which were carried out include: (a) The successful use of a programmable controller to replace conventional logic relays and sequence controlling on five automatic batch A-centrifugals at UR (b) The use of a continuous A-ldentrifugal for processing all the A-sugar going to remelt for refining at PG (c) The fitting of a 3 m wide monitor casing round a conventional continuous centrifugal at DL to reduce B- sugar breakage (d) The commissioning of a new A-centrifugal station at UK Thermal Efficiency, Fuels and Steam Generation The drive for higher thermal efficiency and reduced use of additional fuels, which was commented on in the previous season's review, gathered momentum during 1981 and has led to some interesting developments At ML a systematic and very comprehensive fuel and energy control has been instituted with daily, weekly and seasonal reports and daily targets for factors affecting thermal efficiency such as : moisture % bagasse, pan movement water etc Some typical data from a weekly fuel report have been summarised in Table 5 The apparent discrepancy between steam produced per ton of cane (0,669 for the week) and steam to evaporators per ton of cane (0,554) can be explained by the occasional use of a condensing turbo-alternator and by the fact that steam produced by the boilers is metered while evaporation steam is calcuiated from a brix-balance TABLE 5 ML - Fuel Control Data - Week No 33 Tons steam produced per ma HS/ firing hour MJ taken up by steam Tons bagasse burnt in boilers MJ in burnt bagasse MJ in coal burnt MJ electric power imported' ' MJ electric power exported MJ in fuel used for factory per ton cane MJ in steam to process per ton brix mixed juice Steam produced per ton cane Steam to evaporators per ton cane Overall time efficiency Kg water used per ton of'cane Wash water on filters Raw house pan movement water Water to refinery evaporator B & C-centrifugal wash water Refinery pan movement water Refinery centrifugal wash water Week 1 To Date 0, x lo , x los x lo8 226,3 x lo3 1317,O x lo ,669 0,554 76,9 13,l 34,7 3,s 3,4 37,8 6,6 99,l 0, x lo ,s x lo x lo3,9816,9 x lo ,2 x lo ,730 0,586 71,s 12,6 30,4 2,3 4,o 46, ,6 Abuse of water during processing has been recognised as being one of the principal causes of poor thermal efficiency, because most of the water has to be evaporated in single effeot in the vacuum pans At ML, process water totalled about 100 kg per ton of cane with pan circulation water accounting for about 70% of this Other mills have also started energy balances and EM and FX report good results from their preliminary work in this direction Figure 3, which shows the cumulative total coal consumption of ML during the past three seasons, shows that these efforts can lead to important cost savings (a difference of about tons in total coal requirements between and ) SEASON /80 I FIGURE 3 SEASON -- 80/81 SEASON - 81/82 MAY, JUNE, JULY I AUG SEPT OCT, NOV, New boilers were commissioned at PG and IL during the season but the most interesting development in the steam generation and utilisation field was the commissioning of a mechanical vapour compressor at PG This unit compresses vapour from the first effect of the evaporator and reinjects it into the calandria of the same effect Because of difficulties in maintaining a continuous level of evaporation, first vapour compression requires fairly sophisticated controls, which did not come up to expectation at PG The compressor did however run for long enough periods to assess its output at the equivalent of about 30 tons of steam per hour A lesson may be drawn from an accidental explosion w,hich damaged a boiler furnace at AK during the season The explosion is thought to have been caused by accumulation of carbon monoxide generated in a pile of smouldering bagasse during a schedulled stop when all fans had been stopped When the fans were started, the gases exploded at the top of the furnace, and it is suggested that in boilers in which there is no natural draft, the induced draft fan should be kept running at low speed during stops Smuts recovery plants were commissioned at IL and at TS Both involve settling in clarifiers followed by-filtration At IL a low retention time clarifier (about 12 minutes) is followed by a top-fed rotary vacuum filter, while TS has opted for a longer retention clarifier which does not require the use of flocculants and which is followed by a multiroller press for dewatering The TS installation has worked successfully during the past season The sand content of-bagasse, which can be expected to increase proportionately to the increase in ash content of cane, was a major cause of concern to boiler engineers at most mills At IL a spot sample was analysed at 36% ash in bagasse Difficulties in ash disposal, and boiler tube and fan blade erosion were reported by most mills and ML has recommissioned its diffuser press water clarifier to eliminate some of the sand in cane and reduce its concentration in bagasse Chemical Control The season saw a major change in the basis of chemical control of sugar mills, with the adoption of GC analysis of mixed juice and final molasses to convert monthly and final chemical control data for all South African mills from a pol to a sucrose basis

7 Proceedings of The South African Sugar Technologists' Association - June The procedure used for sampling and analysing the products by GC had been tested over the previous two seasons before its industrial application in 1981 Briefly, it involved compositing of weekly mixed juice and final molasses samples at each of the mills, the preservation by freezing of the mixed juice samples, and the transport of the samples by special vehicles to a central laboratory at Mount Edgecombe, where they were analysed for pol and brix and for GC sucrose, fructose and glucose Pol-to-sucrose ratios were calculated weekly for both mixed juice and molasses for each mill and applied to the respective tonnage of pol for the week to convert these to sucrose The sucrose weights then obtained were used to recalculate the weekly recoveries and factory balances retrospectively with a delay of about a week The system is costly but has operated very smoothly It is complementary to the normal pol analyses and balances which are still carried out by each mill for daily and weekly operational control The immediate results have been disappointing in that the vexing occurrence of unpredictable undetermined losses, which were previously thought to be due to shortcomings of the pol analysis, has not been explained and these losses have in fact proved to be larger than when calculated from a pol balance The GC results have however shown that some of the differences in pol, boiling house recovery and losses between mills were due to inter-mill variations in pol-to-sucrose ratios in mixed juice and final molasses, rather than to equipment or operational differences Undetermined sucrose losses averaged 2,04 for the season, with a maximum of 359 at PG, where weekly values proved to be unpredictable and sometimes very high (up to 7) A loss control system involving the accurate monitoring of sugar in all product and effluent streams, which was introduced in most of the Smith group mills during the season, codd only account for a small proportion of these losses (6% at PG) and undetermined losses are still there to remind us of the relative inaccuracy of our factory control and to challenge us to greater efforts Refining and By-Products The SZ backend refinery, which produced tons of refined sugar during the past season, closed down in December after 24 years in operation The: closing was mainly motivated by the necessity of savingbagasse for use as raw material in the production of furfural A new refinery will be commissioned at NB next season to fill the gap in production caused by the closure of the SZ plant SZ was a carbonatation refinery, but NB will use phosphoflotation followed by ion exchange with the possibility of also making use of the Talofloc process when clarifying poor quality me1 t The furfural plant at SZ was expanded to produce furfury1 alcohol During the season the following by-product plants, adjacent to sugar mills, were in operation in South Africa :- ML - Particle board from bagasse FX Paper from bagasse EN - Cattle feed from bagasse and final molasses GH - Paper from bagasse TS - Cattle feed from bagasse and final molasses SZ - Furfural and furfuryl alcohol from bagasse In addition, a fermentation industry based on final molasses turned out a w,ide range of products which included : ethanol, butanol, acetone and yeast The fermentation plants are situated in the main industrial centres and not next to sugar factories Acknowledgements The assistance received from Messrs M Vanis, S Munsamy and A Williamson in the calculation of data published in this review is gratefully acknowledged Thanks are allso due to the SA Sugar Association, the Central Board, Huletts and the Sugar Terminal for the data which they provided and to the Experiment Station for comments on Cane Varieties and the Weather

8 Proceedings of The South African Sugar Technologists' Association June 1982 TABLE A SOUTH AFRICAN SUGAR ASSOCIATION FINAL SUGAR PRODUCTION (Season ) (Metric tons) Mill White Local Market Refinery Raws Brown Export Raws Total Malelane Pongola Umfolosi, Entumeni, Empangeni Felixton (ML) (PC), (UF) Amatikulu Darnall Mount Edgecombe Glendale Gledhow Noodsberg Union Co-op (EN) (EM) (FX) (AK) (DL) (ME) (GD) (GH) (NB) (UC) Tongaat (TS) Illovo (IL) Sezela (SZ) Umzimkulu (UK) (3 712) TOTAL

9 Proceedings of The South African Sugar Technologists' Association -June 1982 TABLE BI CANE CRUSHED AND SUGAR MADE CANE COMPOSITION SOIUTH AFRICAN MILLS SYMBOLS OF FACTORlES ML* PGt UFe ENt EMt FX AK* DL ME A B Average Tons sugar made Moisture raw sugar 0, 31 0, Pol raw sugar Tons of cane crushed total Tons of cane crushed ~er tandem Refined % total sugar 99, Season started on Season completed on Number of crushing days Time account Overall time efficiency % Scheduled stops % gross avaiiable time Lack of cane stops % gross available time Other stops % gross available time Lost time % available crushing time Throughputs per hour actual crushing Tonsofcanecrushed Tons of fibre milled Tonsofbrixprocessed Tons of sugar produced Tons sucrose in mixed juice Tons non sucrose in mixed juice Composition of cane crushed Suc %cane Pol %cane Fibre%cane Brix % cane Ash % cane ERC %cane ERC % suc in cane Extraction Extraction Corrected reduced extraction Imbition%cane Imbibit~on % fibre Preparation index Pol factor Brix factor Recoveries Boilinghouserecovery Overall recovery Tons cane per ton sugar Tons cane per ton 96 sugar Balances Suc lost % suc in cane - in bagasse (a) in filter cake (b) infinalmolasses(c) undetermined (d) Boiling house losses (b + c + d) Sum of all losses (a + b + c + d) Non suc ratlo Pol lost % pol in cane in bagasse in filter cake " infinalmolasses undetermined Fructose ratio FM/MJ Glucose ratio FMIMJ * Cane diffuser t Bagasse diffuser

10 Proceedings of The South African Sugar Technologists' Association -June 1982 THROUGHPUTS AND TIME ACCOUNTS, PERFORMANCES AND LOSSES (Season ) GD GH NB UC* TS IL* SZ UK Totals and A* B Average A* B Average At B Average Averages

11 Proceedings of The South African Sugar ~echnolo~ists' Association -June I982 TABLE CI ANALYSIS OF BAGASSE, JUICES, FILTER SOUTH AFRICAN MILLS SYMBOLS OF FACTORIES ML* FX PGt UF ENt EM? AK* DL ME GD A B Average Final bagasse Pol % bagasse 1,02 Moisture % bagasse 52,15 Fibre %bagasse 46,04 Bagassexcane 31,19 Ash % bagasse 4,33 LCV in ICJ per kg bagassdtt Residualjuiceapparentpurity 56,14 60,75 60,31 51,97 47,42 51,39 51,38 51,39 48,28 45,30 50,61 62,86 Mixed Juice Mixed juice :/, cane 117,7'8 125,42 116,36 127,30 115,36 114,36 115,82 114,86 123,87 121,Ol 104,99 118,71 Brix, 12,30 11,35 11,85 11,58 11,34 11,53 11,44 11,50 11,Ol 11,50 13,36 11,79 Sucrosepurity 84,98 85,62 86,Ol 86,OO 84,18 85,85 85,16 85,61 84,79 86,50 85,34 87,88 Apparent purity 83,81 84,71 8'5,17 85,48 83,63 85,06 84,38 84,82 84,25 85,69 84,44 87,03 Purity difference (MJ-DAC) 0,14 0,33 0,46 0,68 0,47 0,46 0,21 0,37 0,66 0,76 1,06 1,06 Pol/sucratio 0,9862 0,9894 0,9902 0,9940 0,9935 0,9908 0,9908 0,9908 0,9936 0,9906 0,9895 0,9903 Reducing sugars/pol ratio 7,83 5,82 4,41 4,lO 4, ,86 4,42 5,54 5,46 5,65 Suspended solids % mixed juice 0,61 0,44 1,16, 0,67 0,73 1,02 0,77 0,93 0,40 0,69 0,67 0,51 Clarified Juice Brix 12,22 11,36 12,12 11,80 11, ,87 10,68 10,70 13,09 11,37 Apparent purity 83,45 84,50 86,06 84,62 83,Ol - 84,82 83,51 86,35 84,ll 87,27 Purity difference (CJ-MJ) -0,36-0,21 0,89-0,86-0,62-0,OO -0,74 0,48-0,33 0,24 Reducing sugarslpol ratio 8,34 5,89 4,41 4,11 $ ,77 4,57 $28 5,32 6,13 Average ph 7,l 7,l 7,O 72 7,O ,4 72 Filter Cake Pol % filter cake 2,38 1,34 0,62 0,93 0, ,78 0,73 0,71 0,74 0,88 Filter cake %cane 2,31 2,83 5,71 3,71 3, ,68 2,65 5,41 7,43 2,98 Filterwashindex 100,7 99,9 97,8 98,l 100,s ,8 103,l 107,8 102,l 103,7 Purity difference (CJ-filtratej 4,67 3,55 2,45 2,78 4, ,66 3,94 1,99 2,05 1,45 Syrup Brix 62,63 68,74 65,86 67,55 66,02 67,39 64,44 67,40 66,52 69,OO Apparent purity 83,48 84,76 86,56 85,51 83, ,90 84,lO 86,89 84,95 87,75 Purity diff (Syrup-MJ) -0,33 0,05 1,39 0,03 0, ,08-0,15 1,Ol 0,51 0,72 Reducir?g sugarslpol ratlo 8,53 5,84 4,42 3,84 4, ,65 4,58 5,06 5,20 6,20 Average ph 6, ,s 62 6,6 Final Molasses Refractobrix 87,56 82,87 81,31 80,97 81,75-81,51 81,60 82,80 80,62 81,68 Pol/refracto brix purity 30,70 33,88 39,24 40,08 38,52-35,89 35,14 35,33 34,77 37,58 Sucroselrefracto brix purity 33,94 37,31 39,81 40,06 39,51 37,32 36,38 36,19 36,09 39,12 Pol/sucratio 0,9046 0,9083 0,9857 1,0006 0, ,9615 0, ,9635 0,9589 Purity difference (true--target) 1,3 13 1,o 2,s 2, , ,o 15,2 16,3 14,l 15,4 15,l Reducing sugars % 21,9 16,l 13,O 11,5 13,4 Sulphated ash % 14,23 14,74 16,22 15,13 14,32-14,93 14,23 14,42 13,73 15,40 Reducing sugarslash ratio 1,54 1,09 0,80 0,76 0,94 1,02 1,13 0,98 1,12 0,98 Fructose % 9,s 7,3 5,7 4,9 5,9 67 7,l 6, Glucose % 7,9 4,6 3,7 32 4,O ,4 5,O 4,8 * Cane diffuser t Bagasse diffuser tt LCV = ,14 Brix % bagasse - 207,63 moisture % bagasse - 196,05 ash % bagasse

12 Proceedings of The South African Sugar Techrzologists' Association - June 1982 CAKE, SYRUP AND FINAL MOLASSES (Season ) GH TS SZ NB UC* IL* UK Averages A* B Average A* B Average At B Average

13 TABLE Dl MASSECUITES, EXHAUSTIONS, CLARIFYING AGENTS AND ADDITIONAL FUELS SOUTH AFRICAN MILLS (Season ) SYMBOLS OF FACTORIES ML PG UF EN EM FX AK DL ME GD GH NB UC TS IL SZ UK Averages - Brix in mixed juice % cane 14,49 14,24 13,79 14,74 13,08 13,23 13,63 13,92 14,03 14,OO 13,61 14,35 14,15 13,45 14,03 14,35 14,69 13,93 A-massecuite m3per ton brixinmixedjuice 1, ,18 1,28 1,06 1,04 0,99 0,95 1,08 1,04 1,20 0,98 0, ,03 1,10 0,98 1,07 Refbrixofmassecuite 92,71 92,17 92,51 91,45 92,53-92,89 91,43 93,11 91,14 93,23 92,09 92,79 92,90 93,ll 92,88 92,90 92,93 92,50 Purity of massecuite 84,04 85,88 86,71 84,99 84,22 86,10 84,71 87,36 85,07 87,66 87,90 85,03 84,19 85,94 85,88 86,48 85,53 85,82 PurityofA-molasses 68,09 70,40 72,86 71,58 69,58 69,90 68,61 67,74 70,08 69,99 70,16 65, ,40 66,05 69,21 67,90 69,14 Puritydrop 15,95 15,48 13,85 13,41 14,64 16,20 16,lO 19,62 14,99 17,67 17,74 19,50 19,32 15,54 19,83 17,27 17,63 16,68 Exhaustion 59,48 60,90 58, ,14 62,51 60,55 69,62 58,89 67,17 67,63 66,53 65, ,Ol 64,86 64,21 62,99 PurityA-massecuite-puritysyrup 056 1,12 0,15-0,52 0,56 0,20 0,61 0,66 0,16-0,09 2,25-0,16-0,12 1,38 0,67 0,61-0,31 0,54 Purity of remelt 84,98 85, ,05 88,25 85,69 88,48 85,59 85,74 86,95 84,50 83, ,lO 85,99 85,05 80,74 Bmassecuite m3per ton brixinrnixedjuice 0,50 0,46 0,48 0,54 0,43 0,38 0,37 0,36 0,41 0,41 0,47 0, ,29 0,41 0,38 0,42 Refbrixofmassecuite 94,91 93,87 94,41 94, , ,80 92,22 94,73 94,14 95,01 96,04 92,76 94,Ol 93,80 93,94 94,04 Purityofmassecuite 68,50 70,80 71,44 70, ,20 69,80 68,00 69,71 70,53 70,56 65,33 65,Ol 70,52 67,70 69,51 67,93 69,48 PurityofB-molasses 42,37 46,04 51,49 51,97 49,34 50,40 46,95 46,15 48,98 46,28 48,91 42,43 48,18 50,36 42, ,19 47,29 Puritydrop 26,13 24,76 19,95 18,99 21,07 20,80 22,85 21,85 20,73 24,25 21,65 22,90 16,83 20,16 25,49 22,07 22,74 22,20 Exhaustion 66,19 64, ,72 59,07 58,90 61,71 59,67 58,29 64,W 60,06 60,89 49,96 57,59 65,15 60,41 61,08* 60,61 C-massecuite m3 per ton brix in mixed juice 0,29 0,27 0,26 0,24 0,28 0,30 0,27 0,27 0,21 0,21 0,25 0,22 0,25-0,24 0,24 0,25 0,26 " Refbrixofmassecuite 98, ,57 97,49 97,41 96,74 97, , ,61 96,19 97, $ Purityofmassecuite 52,07 53,68 54,31 53,87 55,06 55, ,59 55,64 51,83 52,25 47,44 50,93 53,70 54,31 51,90 52, Q ApparentpurityofC-molasses30,70 33,88 39,24 40,08 38,52 35,89 35,14 35, ,58 36,93 33, ,89 38, ,36 35,91 9 Puritydrop 21,37 19,80 15,07 13,79 16,54 19,88 20,06 18,26 20,87 14,25 15,32 14,26 13,65 16,81 16,04 14,31 16,07 17,40 2 Crystal content 30,32 28,35 23,72 22,22 26,23 30,21 29,92 27,41 30,93 21, ,68 21,17 22,80 25,lO 22,05 24,53 26,24 Exhaustion 59,23 55,78 45,66 42,71 48,86 55,61 56,03 52,68 57,51 44,05 46,49 44, ,93 9 Total volume all raw massecuites m3 per ton brix in mixed juice 1,89 1,92 1,92 2,06 1,77 1,72 1,63 1,57 1,70 1,66 1,92 1,60 1,64-1,56 1,76 1,61 1,75 White sugar massecuites kg sugar per m3 white massecuites Clarifying agents and chemicals Tons limestone per 1000 tons white sugar - 55, , ,O - - Tons coke per ton; white sugar Tons phos acid per 1'000 tons white sugar ,35 TQDS sulphur per 1'000 t0ns white sugar 0,1 0,1 5,6 - Phos acid ppm mixed juice Flocculant ppm mixed juice 0,8 2,7 4,l 2,3 Tons lime per tc 2,0* 0,9* 1,1* 1,3* Enzymes ppm sugar - 47,7 103,3 Additional fuels ner tc Tonsofcoal 19, ,70 30,67 2,07 46,81 3,96-0,47 11,60-1,80 12,25 6,Ol 6,30-0,17 - Tons of wood ,58 2, ,89 0,21 0,33-0,60-0,02 0, Converted into bagassei : 77, ,48 38,80 131,82 11,44 187,25t 15,85 1,07 2,14 46,79-7,95 49,08 24,08t 25,40-0,91 - * Includes lime used in refinery t Part of bagasse used for by-products 3 1 ton coal equivalent to 4 tons of bagasse; 1 ton firewood equivalent to 1,2 tons of bagasse a

14 TABLE B2 CANE CRUSHED AND SUGAR MADE, CANE COMPOSITION, THROUGHPUTS AND TIME ACCOUNTS, PERFORMANCE AND LOSSES SWAZILAND, MALAWI AND ZIMBABWE MILLS (Season ) MH NH HV TR SYMBOLS OF FACTORIES UR SM DW* A* B Average At B Average A* B* Average A B Average Tons raw sugar Tons white sugar : ' ' Total sugar, tons White % total sugar - 9, ,74 38,98 - Pol raw sugar 98,62 98,67 98,64 98,29 98,82-98,62 - Moisture raw sugar n 7n - - Tons of cane crushed - total Tons of cane crushed -per tandem Season started on Season completed on ,,, Number of crushing days Time Account Overalltimeefficiency % Scheduled stops %gross available time Lack of cane stops % grpss available time Other stops % gross ava~lable time Lost time % available crushing time Throughputs per hour actual crushing Tons of cane crushed Tons of fibre milled Tons of brix processed Tons of sugar produced Tons pol in cane Tons non pol in cane Composition of cane crushed Pol%cane 12,72 12,59 12,65 12,89 11,80 13,49 13,46 13,47 13,92 13,84 14,Ol 13,93 13,41 13,05 13,31 Fibre %cane 14,48 14,37 14,42 14,40 12,18 15,20 15,20 15,20 16,13 15,24 15,21 15,22 15,50 15,40 15,47 Brixzcane 14,93 14,91 14,92 15,61 14, ERCXcane 11,06 10,88 10,96 10,97 10,Ol 11,66 11,60 11;62 ll;80 12;13 12; j39 ERC %pol in cane 86,94 86,41 86,64 85,lO 84,83 86,43 86,18 86,29 84,77 87,64 87,72 87,68 85,61 85,51 85,58 Extraction Extraction 96,77 94,79 95,66 94,60 97,61 95,92 96,08 96,02 94,96 97,22 97,50 97,36 95, ,78 Correctedreducedextraction 96,48 94,13 95,17 93,83 96,79 95,73 95,91 95,84 94,99 96,95 97,23 97,09 95,67 95, Imbibition % cane 43,43 32,08 37,08 29,83 41,58 42, ,33 50,18 49,64 49,09 49,36 40,88 35,45 39,4 1 Imbibition O/ fibre Preparation %dex Recoveries Boilinghouserecovery ,Ol 89,31 87, ,21 86, , Overall recovery ,ll 84,49 85, ,74 81, , Tons cane per ton sugar - - 9,06 9,07 9, ,75 8, , Tons cane per ton 96" sugar - - 8,82 8,80 9, ,51 8, , Pol balance Lost in bagasse (a) Lost in filter cake (b) Lost in final molasses (c) Undetermined losses (d) Boiling house losses (b + c +'d) Sum of all losses (a + b + c + d) Red sugars in FM % RS in MJ Non DO] ratio * Cane diffuser t Bagasse diffuser Nore:-All extraction and recovery figures listed in this table are based on pol

15 TABLE Cz ANALYSIS OF BAGASSE, JUICES, FILTER CAKE, SYRUP AND FINAL MOLASSES SWAZILAND, MALAWI AND ZIMBABWE MILLS (Season ) MH NH HV TR SYMBOLS OF FACI'ORIES UR SM DW* A* B Average At B Average A* B* Average A B Average Final bagasse Pol % bigasse 1,35 2,18 1,81 2,28 1,12 1, a 1,68 1,66 2,04 1,29 1,21 1, ,72 1,68 Moisture % bagasse 50,96 51,36 51,12 50,07 52,80 52,54 49,27 50,61 49,92 48,51 47,39 47,95 51,88 52,37 52,01 Fibre%bagasse - 46,86 45,33 46,00 44,83 44, ,20 48,40 47,09 46,77 49,36 50,61 49, ,41 44,88 Ash "/, bagasse , Bagassexcane 30,33 30,13 30,22 30,50 25,22 33,64 31,41 32,32 34,48 29,81 28,99 29,40 33,44 33, LCV in kj per kg bagasse Residual juice Apparent purity 61,93 65,86 64,12 44,90 47,46 56,11 55,28 55, Mixed juice Mixed juice %cane 113,lO 101,96 107,16 99,33 116,36 108, ,06 115,70 119,83 120,lO 119,96 107,45 101,66 105,94 Brix 12,61 13,65 13,16 14,15 11,87 14,04 14,38 14,24 13,62 12,90 13,06 12,98 13,99 14,33 14,08 Apparentpurity 86,30' 85,79 86,Ol 86,74 83,43 85,Ol 84,72 84, ,08 87, ,61 85,53 Reducing sugarslpol ratio - - 4,27 3, ,47 6, ,51 Suspended solids % mixed juice 0,24 0,70 0,48 0,73 0, ,44 0,45 0,45 0,40 0, Clarified juice Brix ,33 14,02 11, ,72 13, , Apparent purity - 85,30 86,39 82,39 87,61 84, ,08 Purity difference (cj -' M:J) - -0,71-0,35-1,M - - 2,78 0, Reducing sugarslpol ratio 4,30 3,53 6,49-3,75 6,72-3,96 - Average ph ,0 7,l , Filter cake and filtrate Pol %filtercake - - 2,27 0,82 1, ,27 1, , Filter cake %cane 2,36 '5,03 3,21 4,28 1,93 0,65 - Filter wash index 98,70 101,00 102,OO - 103,80 103,20-101,70 - Purity difference (c;-'filtiatej ,39 4, ,71 3, , syrup 64,26 66,44-67,09 - Apparent purity - 84,43 86, ,95 84, ,32 Purity difference (syrup- MJ) ,60 0,11-0,43-3,12 0,67-0,24 Reducing sugarslpol ratio - 4,92 3,58 6,28-3,86 6,45 4,17 Average ph ,s ,9 Brix ,83 63,39 62, Fial molasses Refracto brix ,54 84,07 85, ,67 84, , Pollrefracto brix purity ,25 36,15 36,39 41,91 39, ,84 Sucroselrefracto brix purity ,98 N,69 40,lO 44,81 41,65 42,37 Purity difference (true- target) - - 2,Y 22 1, ,7 2,6 Percentage reducing sugars - 17,66 17,70 13, ,85 17,74 12,86 Percentage sulphated ash 14,22 15,25 17, ,30 13,72-15,63 - Reducing sugarslash ratio 1,24 1,16 0,75-0,59 1,29 0,82 - Mol at 85 refracto brix % cane - - 3,39 3,19 4, ,77 4, * Cane diffuser t Bagasse diffuser ,88 86,94 1,41 4, ,08 101,a 64,41 87,lO 1,57 4,69

16 Proceedings of The South African Sugar Technologists' Association - June 1981 TABLE Dz MASSECUITES, EXHAUSTIONS, CLARIFYING AGENTS AND ADDITIONAL FUELS SWAZILAND, MALAWI AND ZIMBABWE MILLS (Season a ) SYMBOLS OF FACTORIES MH UR SM NH DW HV TR Brix in mixed juice % cane 14,07 14,06 13,81 15,25 15,76 15,57 14,90 A-massecuite m3 per ton brix in mixed juice 0,90 0,97 0,92 0,83 1,14 1,03 - Ref brix of massecuite 93,93 90,58 93,02 90,98 91,93 93,lO - Purity of massecuite 85,99 87,42 83,07 85,51 86,07 84,26 - Purity of A-molasses $7 64,68 71,81 71,02 63,60 - Purity drop 18, ,39 13,70 15,05 20,66 - Exhaustion 66,15 63,23 62,68 56,83 60,34 67,36 - Purity A-massecuite - purity syrup 1,56 0,57 0,07-2,44 1,53-3,06 - B-massecuite m3 per ton brix in mixed juice 0,35 0,39 Ref brix of massecuite 94,85 93,42 Purity of massecuite 69,48 71,35 Purity of B-molasses 46,81 46,56 Purity drop 22,67 24,79 Exhaustion 61,34 65,02 C-massecuite m3 per ton brix in mixed juice Ref brix of massecuite Purity of massecuite Purity of C-molasses Purity drop Crystal content Exhaustion Total volume all raw massecuites m3 per ton brix in mixed juice 1,47 1,57 1,46 1, ,60 - White sugar massecuites Kg sugar per m3 white massecuite Clarifying agents and chemicals Tons lime per tc 0,48 0,75* 0,66 0,82* 133 0,79 0,48 Tons,sulphur per tons white sugar - 0, , Tons phosporic acid per tons white sugar , Flocculant ppm mixed juice 3,70 4,30 0,30 1,30 2,M 1,60 - Enzyme pprn sugar 10, Additional fuels per tc Tons of coal 2,83 1,37 8,47-2,59 12,14 Tons of wood ,Ol Converted into bagasse 11,31 5,37 33,93 1,21-10,36 48,59 * Includes lime used in refinery

17 Proceedings of The South African Sugar Technologists' Association June 1982 TABLE E COMPARATIVE MANUFACTURING DATA OF RECENT YEARIS (South ~frican Mills) SEASON Throughput and Time Efficiency Tons cane per hour Tons fibre per hour Time efficiency Cane Pol %cane Fibre % cane Juice Apparent purity of mixed juice Reducing sugars/pol ratio (mixed juice) $67 Milling Imbibition % fibre Extraction Pol % bagasse Moisture % bagasse Bagasse % cane LCV bagasse kj/kg 7 050* 6 985* 7 003* Available kj in bagassejkg'brik in rnkedjuice ' * * Recoveries Boiling house recovery 87 75t Overall recovery 85 14t Tons cane per ton of sugar Filter cake Pol % filter cake Filter cake :/, cane Final molasses Brix Gravity purity Weight at 85 Bx % cane Average sugar polarisation Pol Balance Lost in bagasse Lost in filter cake Lost in final molasses Undetermined losses Lost in boiling house Total losses m3 massecuite per ton brix in mixed juice A-massecuite B-massecuite C-massecuite Total Exhaustion of massecuites A-massecuite 62, B-massecuite C-qassecuite Brix of syrup Calculated from new LCV formula (see table C ) t Sucrose basis

18 TABLE F AVERAGE MANUFACTURING RESULTS BY MONTHLY PERIODS FOR SOUTH AFRICAN MILLS (Season ) END OF MONTHLY May 2 May 30 June 27 August 2 August 29 Sept 26 October 31 Nov 28 January 2 January 30 Mar 15 PERIOD Tons of sugar made and esti- Month mated To-date Tons cane crushed Month To-date Tons cane crushed per,hour Month 263,24 230,32 229,88 233,92 228, ,46 228, ,Ol 234,56 247,24 270,29 actual crushing To-date ,32 231,94 232,73 231, , , ,46 232,56 233,87 Sucrose % cane Month 10,13 10,99 11,80 12,35 12,99 12,234 12,87 12,67 12,48 11,64 1 1,45 To-date ,90 11,38 1 1,77 12,06 12,21 12,33 12,37 12,39 12,33 12,30 Fibrexcane Month 16,53 15, ,63 15,63 16,16 16,16 16,50 16,87 17,OO 16,77 To-date 16,53 15,81 15,69 15,67 15,66 15,75 15,83 15,91 16,03 16,lO 16,13 Tons cane pet ton sugar Month 12,21 10,88 9,90 To-date ,40 Extraction Month 95,90 96,76 96,89 97,12 97,22 97,12 97,13 97,02 96,94 96, To-date 95,90 96,68 96, ,OO 97,03 97, ,03 97,02 97,02 Imbibition %fibre Month To-date Pol %bagasse Month 1,18 1,06 1,13 1,lO 1,13 1,12 1,13 1,12 1,lO 1,02 0,98 To-date 1,18 1,08 1,11 1,lO 111 1,11 1,12 1,12 1,11 1,11 1,lO Moisture%bagasse Month 52,15 52,63 52,41 51,70 5 1,25 51,14 50,75 51,23 51,51 51,29 52,26 To-date ,22 51,99 51,83 51,63 51,57 51,57 51,54 51,57 Boiling house recovery Month 83,49 85,98 87,W 88,26 88,50 88,27 88,34 87,80 87,84 86,90 85,36 To-date 83,49 85,75 86,239 87,47 87,74 87,234 87,93 87,92 87,91 87,83 87,74 Overall recovery Month 80,07 83,20 85,16, 85,72 86,03 85,73 85,80 85,19 85,15 84,24 82,77 To-date ,90 84,ll 84,79 85,ll 85,23 85,34 85,32 85,30 85,21 85,13 Mixed juice sucrose purity Month 79,76 83,43 85,34 85,823 86,42 86,79 86,56 86,14 85,62 84,87 83,33 To-date 79,76 83,07 84,29 84,96 85,34 85,62 85,80 85,84 85,232 85,76 85,67 AS/pol ratio in mixed juice Month 8, ,56 5,14 4,79 4,55 4,58 4,62 5,08 5,46 7,49 To-date 8,14 7,60 6,49 5,91 5,62 5,41 5,25 5,17 5,16 5,18 5,27 Pol/sucrose ratio in mixed juice Month 0,9786 0,9852 0,9891 0,9905 0, ,9939 0,9951 0,9940 0,9934 0, ,9884 To-date 0,9786 0,9845 0,9869 0,9884 0,9892 0,9900 0, ;9914 0, ,9916 0,991 5 Purity final molasses Month , ,71 36,45 37,56 37,37 37,29 36,232 36,98 34,83 To-date ,22 33,90 34,21 34,74 35,05 35,47 35,73 35,86 35,96 35,91 Sucrose lost in final molasses % Month - 11,16 9,65 9,08 8,84 8,91 8,91 9,36 9,39 10,29 10,75 sucrose in cane To-date - 11,33 10,42 9,85 S, ,33-9,34 9,35 9,42 9,47 Undetermined lost sucrose % Month - 1,93 1,69 2,oo 2,Ol 209 2,03 2,11 2,02 2,Ol 2,61 sucrose in cane To-date - 1,96 1,84 1,91 1,94 1, ,Ol 2,Ol 2,02 2,04 Pol/sucroseratioFM Month 0,6774 0,9123 0,9526 0,9526 0,9687 0,9821 0,9937 0,9861 0,9907 0,9749 0,9550 To-date 0,6774 0,9140 0,9333 0,9406 0, ,9594 0,9629 0,9663 0,9670 0,9665

19 TABLE G CANE VARIETIES AND RAINFALL (Season ) SYMBOLS OF FACTORIES CANE VARIETIES CRUSHED (Percentage by weight) Rainfall Unknown During NCo NCo NCo NCo NCo NCo N CB N N N N N J N Mixed and other Season / Varieties Varieties (rnrn) ML 76,4 0, ,4 22 2,l PG 83,4 2,5-1, ,6-02 2,7 1,o 5,2 427 UF ,9-2,8 0,l 11,l 0,9 2, EN 84,5 O,1 12, ,6 1, EM 38,6 9, ,1 0,3 42 0,4 0,4 0,l 02 44, FX 58,l 14,4 0,9 0,l 7,3 0,1 0,1 5,O 02 0,4 12,7 911 AK 87,4 2,8 5,7 03 0,l 1,3 1, DL 86,O 0, ,0 0,3 3,s 0, ME 60,4 1,8 12,3 0,5 0,5 13,7 0,s - 8,7 1,O 799 GD GH 85,l 0,4 0,2-0, , ,o 3s 756 NB 19,8 49,s 77 1,4 2,2 2,O 0,2 0,3 15,9 297 UC ,8 4,7-0,9 0,3 0,3 0,1-0, TS 84,7 0,8 0,2 0, , ,1-0, IL ,s 0,2 02 1,l, 6,8 0,6-0, , SZ 89,O 1, ,O 0,3 0,l - 0,2 0,4 3,1 920 UK 83,4 1,2 5,O ,2 4,7 0,4 0, ,1 697 Average SA Mills 718 4,8 5,6 07-0,4 0,l 0,2 6,O 0,l 12-0,6 0,2 0,4 13 5,4 - MH 89,6 83 1,s 0,l UR 88,8 0,3 9,0-0,9 0,9 0,l 449 SM 83,4-0,9 12, NH ,3 03-2,9 IS DW 70,O 6,6-23,4 174 HV 96, ,6 277 TR 100,O TABLE H TRANSPORT SUMMARY SOUTH AFRICAN MILLS (Season ) Percent of Cane Transported MILLS ML PG UF EN EM FX AK DL ME GD GH NB UC TS IL SZ UK Average South African Railways 12, ,9 53,3 0,2 28,O 13,4 6,3 5,6 02 9,6 Chopped Cane Bins 5,8 19,l 1,o 1,s Tram 99,9 51,5 26,7 46,6 11,s Hilo 77,4 15,2 79,3 78,5 51,2 66,l 43,4 16,8 90, ,O 41,O 47,9 Lorry and Trailer 8,8 4,4 1,3 5,6 70,9 22,6 2,3 30,5 57,7 1,3 85,7 56,5 19,l Tractor 4,2 2,7 91,l 20,6 18,9 15,7 1,O 26,O 17,9 19,5 19,5 7,1 0,l 0,l 2,3 10,2

20 TABLE J COMPARATIVE DATA OF REPORTING SA MILLS FROM 1925 ONWARDS PERIOD (SEASON) Percent Cane Sucrose Fibre Cane/Sugar Ratio Tel Quel 96 Pol Sugar Extraction Pol % Fibre in Bagasse Pol Percent Bagasse Moisture Imbibition Percent Cane Fibre Purity Mixed Juice Reducing Sugar Ratio Final Molasses Purity Boiling House Recovery Overall Recovery Average Average Average Average Average ,19,13,53 14,28 14,21 13,32 13,89 13,52 14,19 13,33 13,87 13,93 13,34 13,79 13,87 13,35 13,ll 13,12 13,66 13,69 13,75 13,29 13,55 13,90 13,53 12,99 13;72 12,92 13,ll 12,88 13,61 12,97 13,26 13,08 13, ,60 12,43 12,83 12,64 12,96 13,34 12,30 15,78 15,30 15,99 16,21 15,80 15,90 16,19 15,80 16,29 16,lO 16,31 16,03 16,06 15,74 15,81 15,38 15,92 15,92 15,22 14,52 15,49 15, ,49 15,57 15,09 15,Ol 15,32 15,03 15, ,82 15,64 15,59 15,22 15,67 15,52 15,79 15,22 15,49 15,95 16,13 9, ,29 8,36 8,84 8,55 8, , ,55 8,87 8,60 8, ,93 9,09 8,74 8,70 8,51 8,97 8,66 8,42 8,75 9,20 8,63 9,28 9, ,64 8,93 8,77 8,93 8,97 8,95 9,33 9,41 9,12 9,07 8,85 8, ,64 8,73 8,08 8,14 8,60 8,31 8,52 8,09 8,73 8,27 8,32 8,65 8,36 8,28 8,62 8,67 8,82 8,44 8,41 8,26 8,73 8,42 8,20-8,49 8,97 8,40 9,06 8,83 8,86 8,34 8,63 8,47 8,62 8,65 8,68 9,00 9,08 8,80 8,77 8,54 8, ,83 92,05 93,28 93,07 93,94 93,32 92,94 93,33 92,98 93,00 92,67 92,40 93,04 92,32 92,93 93,36 92,87 92,86 93,35 94,21 94,15 94,08 94,16 93,43 93,99 94,22 94,15 94,74 94,98 95,41 95, ,49 95,00 95,323 95,48 95,87 96,63 96,92 96,89 97,02 Note-From 836 7,05 6,Ol 6, ,81 5,82 6,02 5,74 6,02 6,25 6,32 5,95 6,76 5,98 5,66 5,89 6,16 5,98 5,50 5,02 5,16 5,23 5,73 5,00 5,24 5,04 4,s 1 4,30 4,06' 3,58 3,98 3,87 3,94 4,35 3,87 3,79 3,51 2,95 2,70 2,73 2,38 3,88 3,11 2,77 2,79 2,54 2,67 2,66 2, ,65 2,75 2,75 2, ,60 2,47 2,55 2,66 2,60 2,43 2,24 2, ,51 2,20 2,29 2,19 1,98 1,89 1,80 1,61 1,75 1,69 1,73 1,91 1,68 1,66 1,56 1,35 1,23 1,24 1,lO 50,57 51,60 50,19 50,32 50,46 50,53 50,84 51,22 51,71 52,53 52,47 52,92 51,32 53,18 53,12 53,06 52,38 53,26 53,Ol 52,54 52,17 52,46 52,64 52,78 52,98 53,52 53,47 53,32 53,30 53,07 52,66 52,85 53,19 53,lO 53,15 53,52 53,20 52,55 51,59 52,04 52,lO 51, to 1980 all data based on pol 27,6 32,6 35,O 35,2 34,4 34,l 33,7 32,8 35,O 34,9 32,7 30,7 33,8 32,l 35, ,9 34,6 36,2 36,7 41,2 39,8 39,4 36,3 40,6 39,9 39,2 41,l 41,2 43,2 41,l 41,3 45,O 44,6 41,7 43,7 41,7 45,6 45,4 49, , ,09 86,Ol 86,23 85,86 86,24 85,92 86,22 86,40 84,92 86,25 85,61 85,86 85,95 85,96 85,49 85,lO 84,46 85,52 85,63 86,04 83,36 85,30 85,52 85,24 84,22 85,06 83,41 83,60 84,25 84, ,66 85,66 85,Ol 84,80 84,70 84,47 84,39 85,36 85,40 84,80 85,67 3,65 3,22 3,38 3,30 2,95 3,67 3,11 3,12 3,52 2,92 3,66 3,28 3,29 3,40 3,32 3,69 4,30 3,51 3,31 3,31 5, ,32 3,67 3,73 3,63 3,81 4,23 4,17 3,80 4,20 4, ,05 4,15 5,31 5,58 5,67 5,27 5,11 5,25 5,27 45,3 43,3 42,O 41,8 41,l 41,5 41,4 40,s 40,3 39,3 39,s 39,3 40,7 39,6 39,9 38,5 39,l 40,3 40,3 39,s 39,6 39,4 39,9 39,6 39,9 40,6 38,8 39,4 38,3 38,9 39,4 40,O 39,2 38,4 39,3 38,8 38,2 38,3 38,O 38,3 38,7 37,l 83,67 88,36 89,29 89,12 89,61 89,14 89,68 89,63 88,72 89,96 89,36 90,W 89,46 90,51 89,79 90,43 89,49 89,42 89,40 89,72 87,81 89,60 89,65 89, ,38 87,52 87,40 88,58 88,57 89,41 89,48 89,13 88,76 88, ,99 88,62 89,58 89,48 88,17 87,75 75,12 81,34 83,30 82,94 83,73 83,19 83,35 83,65 82,50 83,66 82,81 83,20 83,23 83,56 83,44 34,42 83,ll 83,W 83,45 84,53 82,67 84,30 84,42 83,69 82,40 83,27 82,33 82,72 84,13 84,51 85,76 85,50 85,17 84,76 84,06 84,58 84,97 84,96 86,55 86,73 85,