SUGAR INDUSTRY
prepared by Giuseppe De Vincenzo
SUGAR INDUSTRY
Revision GDV.1.0
RAW SUGAR PROCESS
After sugar cane has been harvested it must be processed within less than 24 hours to avoid sugar loss by inversion to glucose and fructose. Preparation and Extraction When the cane trucks arrive at the sugar mill the sugar cane is weighed and then washed to remove mud and debris. The cane is tipped into a cane carrier which conveys the sugar cane billets to the shredder. The shredder reduces and shreds the cane into fibrous material and ruptures the juice cells. The shredded can is fed into the crushing mill which consists of three large rollers arranged in a triangular formation so that the cane fibre is crushed twice in the mill. After the mill the cane fibre is immersed in a bath of hot dilute juice recycled from a subsequent mill. The process is repeated through a variable number of sets of crushing mills until the last mill is reached. Hot water and weak juice from the last mill is added to help to macerate the cane and to aid in the extraction. About 93% of the juice is extracted. The final mill dewaters the residual cane fibre (Bagasse) which is then conveyed to the bagasse bin and the boiler station for use as fuel, as raw material for paper or hardboard, or as insulating material.
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Heating The juice is sent to multiple heaters where the sugar content is increased to 16-17 Brix.
Sulphitation and Clarification Juice extracted from the crushing mills contains impurities which are removed by adding lime and heating the limed juice. Sulphur dioxide is firstly added to the juice to remove impurities and for decolourisation. After that lime is added to precipitate impurities and to help to remove colouring matter, organic acids and other suspended material. The limed juice is sent to clarification. The process coagulates the impurities into flocks of mud which are settled in a large clarifier vessel. In the clarifier the mud settles to the bottom while the clarified juice overflows from the top of the vessel. The clear sugar juice is run off from the top of each clarifier and goes to the evaporation plant. Muddy juice extracted from the bottom of the clarifiers is mixed with fine bagasse and then filtered using cylindrical rotating vacuum filters (rotary filters) to recover the sugar. The mud and bagasse mix (filter mud) extracted by the filters is used as a fertiliser on cane farms and in gardens. This recycles much of the phosphorous taken up from the soil by the cane plant. Evaporation and Crystallisation The clear juice from the clarifiers is concentrated by boiling it under vacuum in a series of connected vessels called evaporators to a thick pale-yellow juice of about 60-70 Brix. The concentrated juice is called syrup. This thick juice goes to the vacuum pans where it is evaporated to supersaturation. When the predetermined degree of supersaturation is reached, seeding takes place and the crystals are grown to the required size in a process called crystallisation. The sugar crystals are grown to the required size by adding more syrup while boiling continues. When the crystals reach the required size (approximately 1.0mm) the mixture of syrup of crystals, called massecuite, is discharged from the pan. The massecuite goes to a crystallizer where the crystallization is completed.
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Centrifuging and Drying Syrup is separated from the raw sugar crystals in centrifugals which contain perforated baskets which spin at high speed in a casing (similar to a household washing machine). The dark syrup surrounding the crystal is “thrown off� and passes through the perforations and the crystals are washed with hot clean water. The spun-off syrup is repeatedly boiled again and more raw sugar crystals are recovered. This procedure is repeated until the amount of sugar obtained is too small to make further extractions economical. Molasses is the syrup left over from the final centrifuging and is often used for cattle feed, or citric acid, and fermentation products. The raw sugar from the centrifugals is dried by tumbling through a steam of air in a rotating drum. After drying of the crystals, the brown raw sugar is ready for shipping to a refinery or for sale.
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REFINING SUGAR PROCESS
The raw sugar received by a refinery contains 96,5 to 98,5% sucrose and therefore 1,5 to 3,5% impurities which comprise organic matter, inorganic compounds, water and microorganisms. The raw sugar is also highly coloured (brown). Affination The first step in refining is called affination, wherein the raw sugar crystals (color about 1400) are firstly mingled with heavy syrup (typically 60-80 Brix). This softens the external layer of dried syrup on the raw sugar crystals (in order to remove the film of adhering molasses). The softened layer of this mixture, called magma (color about 800), is removed by spinning in centrifuges and washed with hot water leaving a clean raw sugar crystal or affined sugar. The affined sugar is then dissolved in a stirred steam-heated melter to produce an amber coloured liquor (about 54 Brix). Clarification During carbonation the amber coloured melt liquor is mixed and clarified by adding milk of lime and reacted with carbon dioxide (or phosphoric acid) to produce a precipitate of calcium carbonate (chalk or scum) that floats to the top.
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The chalk precipitate entraps organic nonsucrose and inorganic impurities. This process removes impurities and some of the colour compounds. The clarified liquor is taken off from the bottom of the vessel. Scum is discarded from the process at this point. Pressure filters are used to remove the chalk precipitates (returned then to farmers as fertilisers). The clarified light brown syrup (color about 450) is then pumped through specially designed deep bed filters to produce a sparkling, clean liquor. Decolourisation The Clarified liquor is pumped through a series of acrylic and styrene ion exchange resin columns and granular activated carbon columns. This resin has the ability to ‘hold’ the colour particles while allowing the clean sugar syrup to pass through. The resulting low coloured syrup (fine liquor), about 1/10th the original colour, is used for crystallisation of white sugar (color about 100) or for the production of bulk liquid sugar. Evaporation and Crystallisation The fine liquor, after reduction of its water content by multiple effect evaporation, is fed to vacuum boiling pans. The liquor is boiled under vacuum in the pans until supersaturation and sugar is able to crystallise. Rather than allowing the crystals to simply grow randomly, a large number of very small nucleus crystals (slurry)are introduced and a controlled number of crystals are allowed to grow using tight control of the process. The process is continued until the crystals reach the desired size. The resultant mixture of crystals and mother liquor (massecuite) is fed in centrifugals and the sugar crystals are washed with hot water to remove any adhering syrup. Drying The wet refined sugar from the centrifuge is dried and cooled in a rotary drier and then the sugar is sent for packaging or bulk distribution in a food grade container system.
ABOUT BRIX SCALE Brix is the name of a density scale for measuring sugar content in water base solutions. Each degree is equivalent to 1 percent of sugar in the juice. For example, grape juice which measures 15.5 degrees on the Brix scale contains about 15.5% sugar.
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GBOX APPLICATION MAPS RAW SUGAR PROCESS (for a full detailed process diagram see appendix)
PREPARATION AND EXTRACTION Cane Carrier Cane Elevator Cane Leveller Intermediate Cane Elevator Cane Feeder Washing Table Knifed Cane Conveyor Prepared Cane Conveyor Rotating Grid
Pressure Feeder Shredder Feeder Mill Diffuser Kick Drive Diffuser lifting screw
POWER /BOILER PLANT Bagasse Elevator Bagasse Transfer Conv. Horizontal Bagasse Bagasse Bin Stacker
AND CRYSTALLISERS
Sugar Dryer Juice Clarifier – Scraper
JUICE TREATMENT
Pan Circulator Crystallisers Magma Screw Conveyor Magma receiver/ agitator Seed receiver/agitator B/C Remelt Tank Wet Sugar Conveyor Massecuite Agitator
SUGAR MAKING
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GBOX APPLICATION MAPS REFINING PROCESS (for a full detailed process diagram see appendix)
White Seed Receiver/Agitator Wet Sugar Screw Conveyor Pan Circulator
Sugar Conveyor
Phosphatation Clarifier Feed Mixer Phosphatation Clarifier Scraper Raw Sugar Melter – Agitator Melter Liquor Tank Agitator Scum Holding Tank Agitator Quicklime Slaker Milk of Lime Storage Tank Polyelectrolyte Prep. Tank White Polyelectrolyte Prep. Tank Saccharate Preparation Tank Clarifier Drive
Sugar Dryer
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CANE PREPARATION A good cane preparation assists in getting good extraction result. If high extractions are to be achieved it is essential that the cane is prepared in a heavy duty shredder so that most of the sugar containing cells of the cane stalk are ruptured. Not only it is important to rupture a large proportion of the juice contatining cells, but the way in which the cane is prepared is also important. Ideally the type of preparation should result in material where all the cells are ruptured but where long fibres are still evident, which will result in a cane bed which is stable, homogeneous and open enough to facilitate extraction.
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CANE FEEDER and WASHING TABLE Output speed about 8 rpm Male Output Shaft
MAIN CANE CARRIER Output speed about 4 -5 rpm Shaft Mounted
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INTERCARRIER DRIVES Output speed about 5 – 7 rpm Shaft Mounted Power 22kW
CANE CARRIER DRIVE Output speed about 4 – 5 rpm Shaft Mounted
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CANE CRUSHING (EXTRACTION) MILLING The cane juice extraction for the sugar production can be done by mills or diffusers. Extraction by milling has always been the conventional method of processing cane. The milling train is composed generally of 4 to 7 mill units.
Each unit is a set of 3 rolls (superior, input and output) plus a fourth roll that executes the forced feeding (pressure feeder or pressure roll). Basically the extra rolls (underfeed & pressure feed) are included to maintain a steady and constant feed to the 3 roll mill, and reduce spikes in the torque demand. The Mill works most efficiently with a steady feed and constant torque, with the conrol system varying the speed to maintain the constant torque. The three rolls have a synchronized movement that squeeze the sugar cane to produce a kind of Broth. The transmission between them is made by the external pinions. Its actioning is provided by steam turbines, electric motors or hydraulic devices.
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A steam turbine plus a turbo gearbox and a helical gear unit, compose the traditional mill drive but. A combination of planetary and bevel helical gear unit can be either used for mill drive depending by the power requirement. Usual mill size and required characteristics are : Mill Unit size (inches)
Crushing capacity (TCH)
18 x 24" 40 18 x 30" 50 20 x 36" 60 26 x 42" 100 26 x 48" 130 30 x 54" 300 32 x 60" 400 34 x 66" 470 37 x 78" 615 42 x 84" 720 44 x 90" 930 53 x 96" 1.030 (TCH: Tons sugar cane per
Fibre
13% 13% 13% 13% 13% 13% 13% 13% 13% 13% 13% 13% hour )
Total Installed Power (HP)
# of Drives
Single drive Power (HP)
Output speed
Output torque (Nm)
160 200 240 400 500 1.200 1.600 1.800 2.400 2.800 3.600 4.000
4 4 4 4 4 4 4 4 4 4 4 4
40 50 60 100 125 300 400 450 600 700 900 1000
6,50 6,50 6,50 6,50 6,50 6,50 6,50 6,50 6,50 6,50 6,50 6,50
43.200 54.000 64.800 108.000 135.000 324.000 432.000 486.000 648.000 756.000 972.000 1.080.000
Let’s see some applications.
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MILL DRIVES Output speed about 5 – 8 rpm Shaft Mounted Total Required Power : from 120Kw to 3000Kw Hi-Power Unit
Additional Info : Output speed may vary depending by conuntry : - Brasil - 6,5rpm - India - 4rpm - South Africa - 2rpm Consumed power is based on the quantity of fibre per hour that the mill crushes. Base value for consumed power is of 25 HP per TFH (fibre ton hour). For gearbox selection we must consider a constant output torque value.
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PRESSURE ROLL Output speed about 5 – 7 rpm Power 15Kw Shaft Mounted
PRESSURE FEEDER Output speed about 5 rpm Power 150 Kw Shaft Mounted
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ASSIST DRIVE Due to the steam turbine power limitation and the costs involved to change it for a bigger capacity, the solution to increase the production capacity is to apply an assist drive. The assist drive is an electro-mechanical drive for sugar mill applications, when additional power is required in a mill due to either obsolescence of the existing transmission or increase in the mill throughput. The main characteristic of this application (high torques and low speeds) points to the planetary gearbox technology. A planetary gearbox with high nominal torque, driven by an A.C. electric motor with variable speed drive, composes the assist drive. A mill can be equipped with more than one assist drive (up to four units), each one shaft-mounted on each mill roll. The number of units, their power and the configuration adopted is determined for each customer needs in terms of power requirement, operation flexibility, drive efficiency and costs. The use of assist drives mounted individually on all the rolls permits having different speeds on each of the rolls resulting in a better efficiency. For instance, changing the speed of the input roll you can obtain improvement of the crushing/grinding and changing the output roll speed you can obtain a better extraction efficiency. Tests with Rolls using different speeds between them are showing better results. IMPORTANT: the assist drive is only applied in sugar cane plants that have excessive demand of electrical energy.
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CANE DIFFUSION Cane diffusion was pioneered in Hawaii (1968) but its adoption has been steady in South Africa starting from 1974 (today 80% of extraction is made by diffusers). The main types of cane diffuser can be categorised as follow : true counter-current diffusers moving bed diffusers Over time, the moving bed diffusers are providing to be most succesful. Most of the other types are being phased out, either because they are more complicated or because they are not able to handle large cane rates economically. Moving bed diffusers are counter current extraction devices, but operate on a staged basis.
Juice is pumped (with a high percentage of recycle) onto a moving bed of prepared cane between 1.5 and 1.8 meters deep contained in a vessel approximately 60 meters long and divided into 10 to 18 stages. Typically the diffuser would have a working width between 6 and 12 meters.
The prepared cane entering the diffuser is heated by juice which has been raised to a high temperature in juice heaters giving an average temperature in the diffuser of 85째C. The cane bed is moved across the top of a fixed screen by a series of chains with slats between them. The bed is prevented from blinding with fines and overcompaction by sets of patented lifting screws which break up the bed at two points in the diffuser. The bagasse is dewatered by one or two dewatering mills after exiting the diffuser.
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Each diffuser is individually designed to suit the conditions and process specifications that the customer has supplied. Extraction can be as high as 98.5% if high imbibition rates are used with well prepared cane, but if a lower figure is all that is required then the diffuser size and imbibition rates can be reduced accordingly.
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PRESSURE FEEDER Output speed about 10 rpm Power 90 Kw Shaft Mounted
LIFTING SCREW Output speed about 35 rpm Power 11 Kw Keyed male shaft
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CANE DIFFUSION vs MILLING No dramatic difference can be found between milling train and diffuser factories in overall recovery, despite the extraction advantage of diffuser factrories (0,5 to 1% higher) which is worth 5.000 to 10.000 tons/season additional sugar. Operating and maintentance labor requirement are roughly halved with diffusers. Installed power (excluding cane preparation) is typically 90-110 kW/tfh for a milling tandem and 45-50 kW/tfh for a diffucsion plant, i.e. roughly half of the power required in milling. Due to this diffuser factory requires far less prime mover steam, so that lower pressure boiler can be used. No maximum or minimum imbibition rate for diffusion. Since high imbibition rates will eanble a smaller diffuser to be utilized to achieve a given extraction, the reduction in the cost of diffuser would have to be balanced against the cost of additional evaporator capacity and cost of steam. The optimum imbibition rate for any mill depend on local factors. Final bagasse from diffuser has lower calorific value than what is obtainable from milling. Two most marked effects on juice quality is higher colour and much clearer juice from diffuser (with lower rsuspended solids). Because of the lpong residence time of the cane in the diffuser, start up and liquidation operation are rather more prolonged with a diffuser. Likewise on shutting down, liquidation of diffuser takes a much longer time and the clarifiers generally have to handle a reducing brix juice during liquidation. In conclusion the comparison shows the major advantages of diffusion to be lower capital and operating cost, and the ability to achieve a very high sucrose extraction. Disadvantages are lower quality bagasse, higher juice colour and longer start up / shutdown procedure because of the larger cane holdup in the system. Most diffusers have been installed as a aresult of a required increase in crushing capacity. Small increases can be obtained from a milling tandem by fitting pressure feeders or by replacing critical millin units, say the first and the last mill with larger units, but the increase obtainable by this means is limited (see also assist drive). A cost effective method of expansion involves installing a diffuserand utilising some of the existing milling units as a dewatering mills for a diffuser.
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CRYSTALLISERS Energy conservation is a vital aspect in Sugar Industry with co-generation plants. Like in any other process industry, there exists a large potential for energy conservation in Sugar Industry. A detailed study of many installations for more than two years coupled with the detailed analysis of the conventional double worm drive arrangement has resulted in replacement with higher efficiency planetary drive for crystalliser. Brevini drives are in operation in various Sugar Mills and have resulted in reduction in installed power up to 65% in comparison with the conventional worm drive arrangement. Conventional drive arrangement :
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Open worm wheel mounted on Crystalliser Worm shaft supported on pair of bearings Worm reducer gear box Foot mounted motor 2 sets of Flexible couplings Bed plate & supporting structure
Motors are generally rated for 10HP to 20HP for horizontal Crystallisers and 15HP to 30HP for vertical Crystallisers. The drive system operates the Crystalliser shaft in the range of 0.3 to 1 rpm.
Major disadvantages of worm drive system : Combined efficiency of closed worm gearbox and open worm gearing can be as low as 40 %. Transmission efficiency further reduces as a result of : - Bending of crystalliser main shaft - Wearing of bush bearings - Misalignment between worm wheel & worm shaft - Inadequate or contaminated lubrication Very high running & maintenance cost Frequent oil filling ( a rough estimate of oil consumption could be as high as 200 liters per crystalliser per crushing season) Surroundings highly unclean due to oil spillage Very difficult to rotate by hand in case of supply failure Short life span due to higher frictional losses, improper gear meshing, contamination in lubricants etc
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Enormous power saving can be achieved by replacing conventional worm gear system with high efficiency planetary gear drive arrangement (over 90%). More advantages are : Light-weight easier to install Shaft-mounted construction with torque arm; no misalignment related problems Long gear life due to totally enclosed construction and uniform lubrication Oil filling - once a season Low running & maintenance cost Surroundings remain clean and free of oil spillage Easy manual operation during supply failure
HORIZONTAL CRYSTALLISER Output speed about 1,5 rpm Power 11Kw Sprocket chain
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HORIZONTAL CRYSTALLISER Output speed about 1,5 rpm Generally Shaft Mounted
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VERTICAL CRYSTALLISER Output speed about 0,3 - 0,4 rpm Solid output shaft Power 15Kw
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CLARIFICATION Clarifiers are designed to operate on high viscosity syrups, such as final effect evaporator, and recycle melt streams. Conventional round tank and rectangular vessel designs can be supplied. Flotation clarifiers are installed in factories practising sulphitation as well as factories that do not. TYPCIAL SYRUP CLARIFICATION PROCESS
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CLARIFIER DRIVES Output speed : 0,05 – 0,1 rpm Keyed output shaft
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DRYING PROCESS
DRYER DRIVES Output speed : 75 rpm Power 75Kw
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BAGASSE HANDLING BAGASSE DISTRIBUTION Output speed about 10 rpm Keyed output shaft + flex coupling Power 37,5Kw
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BAGASSE DISTRIBUTION Output speed about 30-35 rpm Keyed output shaft + flex coupling Power 2,2Kw
BAGASSE INFEED CONVEYOR Output speed about 10 rpm Male output shaft Power 15Kw
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BAGASSE BIN STACKER CONVEYOR DRIVE Output speed 16 rpm Power 30Kw
BAGASSE BIN STACKER SLEW SRIVE Output speed : 2,5 rpm Power 4KW
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BAGASSE BIN STACKER SLEW SRIVE Output speed : 40 rpm Power 0,75KW
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OTHER DRIVES RECEIVER DRIVE Output speed 1,5 rpm Power 11kW
PUMP DRIVE Output speed 25 rpm Power 55kW
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SUGAR CANE INDUSTRY INTERNATIONAL REFERENCES
ZIMBAWE Triangle Sugar Vertical Crystallisers: Diffuser Lifting Screws Intercarrier Slat Conveyors
3 off PDL705/FE/3000 5 off PDL144S/FE/800 12 off ED2065/MR1/45 8 off ET3065/FS/63
MAURITIUS Illovo Sugar Group Vertical Crystallisers
2 off PDL725/FE/3000
THAILAND E-Saan Sugar Horizontal Crystallisers Vertical Crystallisers
8 off EQ4600/FS/1000 3 off EQ4400/FS/710 1 off PDL144S/FS/900
Mitrphol Sugar Group - Mitrpho Wieng Mill Vertical Crystallisers Horizontal Crystallisers Clarifier Drives
1 off PDL644N/FS/470 12 off EQ4400/FS/1000/S45CR1 1 off PD144S/FS/878
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VIETNAM Tate & Lye Group / Mitrphol Sugar Group – Nghe An Mill Intercarrier Drives Clarifier Drives Vertical Crystallizer
3 off ET3600/FS/90/S46C1-RL 1 off PDL144S/FS/900 1 off SL2005/FAR/3766,8/PAM160
Kieng Giang Cane Table A Cane Carrier Knifed Cane Conveyor Prepared Cane Conveyor Juice Clarifier – Scraper ‘C’ Seed Receiver – Agitator Wet Sugar Conveyor ‘B’ ‘C’ Magma Screw Conveyor ‘A’ ‘B’ Massecuite Dist. Agitator ‘B’ Magma Receiver ‘C’ Massecuite Crystalliser ‘C’ Magma Receiver – Agitator ‘B/C’ Magma Remelt Tank Bagasse Bin Reclaim Screw Conv. Phosphatation Clarifier Feed Mixer Phosphatation Clarifier Scraper Raw Sugar Melter – Agitator Melter Liquor Buffer Tank Agitator Scum Holding Tank Agitator White Seed Receiver Agitator Wet Sugar Screw Conveyor White Massecuite Dist. Agitator Quicklime Slaker Polyelectrolyte Prep. Tank Milk of Lime Storage tank White Polyelectrolyte P/Tank
PDL666N/FS/8554/00 PDL144N/FS/604 ET3150/FS/121/00 ET3150/FS/121/00 ES6150/FS/20875/00 ET3030/FS/249/00 ED2010/FS/26,64/00 ED2010/FS/30,47/00 ET3010/FS/140,74/00 ET3030/FS/249/00 PDL706N/FS/4895,69/00 ET3030/FS/249/00 EM1010/FS/6,94/00 ED3010/FS/23,46/00 ED2010/FS/36/00 ET3010/FS/334,26/00 PD3020/MR1/35,88/00 ED2010/FS/19,27/00 ED2010/FS/19,27/00 ET3020/FS/220,2/00 ED2010/FS/46,1/00 ET3010/FS/133,75/00 ET3020/FS/141,97/00 ED2010/FS/72,87/00 ED2010/FS/20,28/00 ED2010/FS/72,87/00
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Tay Ninh Mill 2 Roll Mill Drives Primary Pressure Feeder Drives Main Pressure Feeder Drives Cane Table Drives
10 off PDL204S/FS/436 2 off PDC144N /FS/600 8 off PDL143N/FS/220 2 off PDL665N/FS/71/00
Other mills supplied in Vietnam • •
Thoi Bin Quang Nam (same equipment like Kieng Giang)
BRASIL
Cane feeder and washing table Main cane carrier Bagasse conveyor Feeding Boiler Conveyor Feeding Boiler conveyor Boiler conveyor Reclaim conveyor Crystallizer capacity Clarifier
2 units ET3805/MN1/224/S46-C1 EQ4520/MN/250/ME180 ET3250/MN/180/PAM180 ET3800/MN1/125/S65-CR1 ET3250/MN/180/PAM180 ES6400/FS/42.142/00/PAM80 ES6600/FS/36.723/00/PAM80 EQ4250/MN/250/PAM160 PDA5400/MN1/2.055/PAM100-112 ES6150/MN1-E/12.176/PAM90
MEXICO Xicontincatl Mill Pressure Feeder Drives
4 off PDL703/FS/196/S-150 CR1
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AUSTRALIA Invicta Sugar Mill (CSR) Intercarrier Drives Diffuser Lifting Screws Diffuser Kicker Drive Bagasse Bin Stacker Slew Drives Bagasse Bin Stacker Winch Drive Bagasse Bin Stacker Conveyor Drive Clarifier Drive Horizontal Crystallisers Receiver Drive Forrester Pump Drives Sugar Dryer Drive
12 off ED2090 / MN1/ 40 ET3600 / FS / 180 PDL144N / FS / 265 / S65C1 1 off PDL123/FS/150 2 off EQ4250 / MN1 / 500 1 off EC3600 / FS / 90 1 off ET3600/FS/90/48x82 ES6600 / MN1 / 21000 2 off ES5800 / MN1 / 1000 / S46 C1 1 off EQ4255 / MN1 / 728 2 off ED2600 / MN1 / 45 / S46 C1 1 off ED2600 / MN1 / 31.5 / S65 CR1
Other mills supplied in Australia • • • • • •
Proserpine Mill - (Queensland) Tully Sugar Mill - (Queensland) Pleystowe Mill - (Queensland) Racecourse Mill - (Queensland) Tableland Mill - (Queensland) Harwood Island Mill - (New South Wales)
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GLOSSARY Sugar Factory Definitions Bagasse The residue obtained after crushing cane in a mill is known as bagasse. Depending on the number of the mill it is referred to as first mill bagasse, second mill bagasse, etc. After a diffuser the residue is called diffuser bagasse. The final residue from a milling train or from the dewatering mills of a diffusion plant is called final bagasse or simply, bagasse. Bagasse Extract The liquid fraction decanted from the bagasse after blending with water in the cold digester. Brix Refractometer brix The term used when a refractometer equipped with a scale, based on the relationship between refractive indices at 20째C and the percentage by mass of total soluble solids of a pure aqueous sucrose solution, is used instead of a hydrometer to test the solids concentration of a sucrose containing solution. The South African sugar industry is now standardised on refractometer brix. The change from hydrometer brix was completed in the 1972/1973 season. Brix-Free Water The water associated with the fibre in cane and bagasse. In some respects this sorpfion water behaves in a manner similar to water of hydration and it is not available for dissolving sucrose. It is driven off at elevated temperatures. The amount of brix-free water is assumed to be 25% on dry fibre. DAC Extract The liquid fraction decanted from the cane after blending with water in the cold digester. DAC Factors Brix Factor: The percentage ratio of the total brix in mixed juice, final bagasse and where applicable, diffuser press water mud, to total brix in cane as determined by direct analysis. Pol Factor The percentage ratio of the total pol in mixed juice, final bagasse and where applicable, diffuser press water mud, to total pol in cane as determined by direct analysis. Fibre The water insoluble matter of cane and bagasse from which the brix-free water has been removed by drying. Where associated with brix-free water, fibre is often called natural fibre. DAC fibre Fibre % cane derived from direct cane analysis and applying the formula Fibre % cane = (100-M-3b)/(1-0.0125b) in which M= moisture % cane b= brix % extract Insoluble Solids Insoluble material in mixed juice or press water mud, determined gravimetrically by filtration according to a prescribed method.
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Intermixed Cane That portion of cane on a cane carrier originating from the overlapping of different consignments. Its composition is unlikely to be representative of anyone consignment and it is therefore excluded from consignment sampling. Juice Mixed juice The mixture of juices from the extraction plant delivered into the juice scales. Press water The juice expressed in dewatering diffuser bagasse. Mud The material removed from the bottom part of the subsiders. The mud contains the settled insoluble solids. Normal Mass The mass of sample equal to the normal mass of sucrose. That mass of pure dry sucrose which, when dissolved in water to a total volume of 100 cm3 at 20°C and read at the same temperature in a tube 200 mm long, gives a reading of 100 degrees on a saccharimeter scale. According to the International Sugar Scale the normal mass of sucrose is 26,000 g. Pol The apparent sucrose content of any substance expressed as a percentage by mass and determined by the single or direct polarisation method. The term is used as if it were a real substance. Purity The percentage ratio of sucrose (or pol) to the total soluble solids (or brix) in a sugar product. The following terms are in general use: Refractive apparent purity: The percentage ratio of pol to refractometer brix. G.C. sucrose refractometer brix purity: The percentage ratio of GC sucrose to refractometer brix. Sucrose The pure disaccharide α-D-glucopyranosyl-β-D-fructofuranoside, known commonly as sugar. In the South African Sugar Industry sucrose is determined by GC. Sugar Cane Botanically a tall grass of the genus Saccharum and agriculturally the crop produced from hybrids which are the progeny of a number of Saccharum species commonly referred to as cane. Specifically for the determination and distribution of sucrose in cane it is the raw material accepted at the mill for processing.
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Definitions as applied to the Methods for Factory Control Ash Carbonated ash: The residue remaining after incineration at 650°C. Conductivity ash: The conductivity ash of a product is the figure arrived at by correlating the specific conductance of the solution of that product with its sulphated ash. Sulphated ash: The residue remaining after incineration at 650°C of a sample which was pretreated with sulphuric acid. Attenuation Index The absorbance of a solution obtained at a specified wavelength expressed per unit cell length and unit concentration, e.g. a*c420 = OD/b·c·10 where a*c420= attenuation index at 420 nm wavelength of light OD = absorbance b= cell length (mm) c= concentration (g/cm3) Bagacillo Very small particles of bagasse separated either from pre-clarification juices or from the final bagasse for filtration or other purposes. Boiling House That part of the factory in which the processes of manufacture from mixed juice to sugar are carried out. Boiling House Recovery The percentage ratio of pol actually recovered in sugar to sucrose in mixed juice. If based on pol in mixed juice it is referred to as Boiling House Pol Recovery. Brix (Degrees) Unit divisions of the scale of a hydrometer, which, when placed in a pure aqueous sucrose solution at 20°C, indicates the percentage by mass of dissolved solids in the solution. The reading obtained in an impure sucrose solution is usually accepted as an approximation of its percentage by mass of total soluble solids. The term brix is used in calculations as a measure of substance, e.g. tons brix. Bulk Density The mass of material per unit of total volume occupied. Some useful values are: Product
Density [kg/m3]
Shredded cane on the carrier Cut whole stick cane loosely piled Chopped cane from harvesters piled bagasse piled raw sugar
280 200 350 200 880
Cane to Sugar Ratio Tons cane required to produce one ton of tel quel sugar. Crystal Content The percentage by mass of crystalline sugar present in a massecuite, magma or similar material.
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Cush-Cush The material removed from mill juice by straining. Dextran A polysaccharide consisting of glucose units linked predominantly in α-(1→6) mode. It is sometimes present in appreciable concentrations in sugar cane and mill products due to microbial activity. Dry Substance The material remaining after drying a product to constant mass, or for a specified period. The mass of dry substance can also be found by deducting from the mass of the product, the mass of moisture, as determined in a specified manner. See also Total Solids Escribed Volume The volume escribed by a pair of mill rolls in a given time. It is equal to the roller length (in m) multiplied by the work opening (in m) multiplied by the surface speed of the rolls measured at the mean circumference (in m/sec) and is expressed in m3/sec. Extraction The percentage ratio of sucrose in mixed juice to sucrose in cane. If based on pol it is referred to as Pol Extraction. Corrected reduced extraction (CRE): Sometimes used to correct for the influence of sucrose and fibre on extraction and is calculated by the following formula: CRE = 100 - (0.03936×(100 - E)×(100-Fc)×Pc0.6)/Fbc Where E= Extraction Pc= Sucrose % cane Fc= Fibre % cane (including insoluble solids in mixed juice) Fbc= Fibre in bagasse % cane (excluding insoluble solids in mixed juice) If based on pol it is referred to as Corrected Reduced Pol Extraction Estimated Recoverable Crystal (ERC) The formula for ERC is ERC=aS-bN-cF where S=sucrose%cane N=non-sucrose%cane F=fibre%cane a = (polbagasse + polsugar + sucrosemolasses) / sucrosecane b = sucrosemolasses / non-sucrosecane c = polbagasse / fibrecane Factors a, b, and c may vary slightly from year to year. Hence values are calculated at the end of every season using weighted averages and assuming that ERC is equal to the total crystal production of the industry. Filter Cake The residue removed from process by filtration including any added filter aid. Gums The precipitate, corrected for ash, consisting mainly of polysaccharides, which is obtained by treating sugar liquors with acidified ethyl alcohol. Imbibition The process in which water or juice is put on bagasse to mix with and dilute the juice present in the latter. The water so used is termed imbibition water. General terms in use are: single imbibition, double imbibition, compound imbibition, depending on the manner in which the water and / or juice is added. Pag. 41 of 47
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Invert Sugar A mixture of fifty percent glucose and fifty percent fructose obtained by the hydrolysis of sucrose. Java Ratio The percentage ratio of pol % cane to pol % first expressed juice. Note: In calculating an average pol % first expressed juice the weighting given to the individual analyses is on the basis of the tons cane from which the respective first expressed juice samples were taken. Juice • • • • • • • • • • •
Absolute juice: A hypothetical juice, the mass of which is equal to the mass of cane minus the mass of fibre. It comprises all the dissolved solids in the cane plus the total water in cane. Clarified juice: The juice obtained as a result of the clarification process. Diffuser juice, also called draught juice: The juice which is withdrawn from a cane or bagasse diffuser. First expressed juice: The juice expressed by the first two rollers of a tandem. First mill juice: The juice expressed by the first mill of a tandem. Last expressed juice: The juice expressed by the last two rollers of a tandem. Last mill juice: The juice expressed by the last mill of a tandem. Primary juice: All the juice expressed before dilution begins. Residual juice: The juice left in intermediate or final bagasse. Secondary juice: The diluted juice which, together with the primary juice, forms the mixed juice. Undiluted juice: All the juice existing as such in the cane. Its mass is equal to the mass of cane minus the combined mass of fibre and brix-free water.
Maceration In the South African sugar industry the term is synonymous with imbibition. The latter is the preferred terminology. Magma A mixture of crystals and sugar liquor produced by mechanical means. Massecuite The mixture of crystals and mother liquor discharged from a vacuum pan. Massecuites are classified in order of descending purity as first, second, etc., or A, B, etc . Mill Settings Mean circumference: mean diameter × π. Mill ratio: The ratio of feed to discharge work openings. Set opening: The distance between the circumferences escribed by the mean diameters of the top roller and feed or discharge roller with the mill running empty. This definition applies pari passu for the openings between underfeed and top roller and between pressure feeder rollers. The mean diameter of a grooved roller is equal to the diameter of the equivalent (same volume and length) solid roller. In practice the arithmetic mean of the diameters over the tips of the teeth and at the roots of the grooves (neglecting any Messchaert grooves) affords a sufficiently close approximation. Work opening: The work opening is equal to the set opening plus the increase in distance between the rollers resulting from the lift during milling operations. Milling Loss The percentage ratio of pol in bagasse to fibre in bagasse. Molasses The mother liquor separated from a massecuite by mechanical means. It is distinguished by the same prefixes as the massecuites from which it is separated. Final molasses: The mother liquor separated from the final massecuite by mechanical means. Pag. 42 of 47
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Non-Pol Brix minus pol. Non-Pol Ratio The ratio between non-pol in sugar plus non-pol in final molasses and non-pol in mixed juice. Non-Sucrose Dry substance minus sucrose. Nutsch Sample Any sample of molasses which is separated from a massecuite at any time prior to curing the massecuite in the factory centrifugals. Overall Recovery* The percentage ratio of pol actually recovered in sugar to sucrose in cane. If based on pol in cane it is referred to as overall Pol Recovery. Polysaccharides Polymers of medium to high molecular mass in which the units are mainly pentoses and/or hexoses. Preparation Index The percentage ratio of brix in the ruptured cells to total brix in cane. Purity The percentage of sucrose in total solids in a sugar product. The following purity terms are in general use: Purityapparent = pol / brix · 100 Puritygravity = sucrose / brix · 100 Puritytrue = sucrose / total solids · 100 In order to specify purity without ambiguity it is necessary to indicate the methods used to determine both the numerator and denominator in obtaining the result. Target purity: A reference purity of final molasses taking into account the effect of the non-sucrose present on its exhaustion. In South Africa the formula reads: Puritytarget = 33.9 - 13.9·log[(f + g)/a] Where f = fructose % molasses (determined by GC) g = glucose % molasses (determined by GC) a = sulphated ash % molasses Target purity difference: The difference between the true purity as determined from GC sucrose and Karl Fischer solids and the target purity as calculated above. Reducing Sugars The reducing substances in cane and its products determined as described in Chapter 8 and calculated as invert sugar. Major reducing sugars are glucose and fructose. Reducing Sugar/Ash Ratio The ratio of reducing sugars to sulphated ash. Reducing Sugar/Pol Ratio The percentage ratio of reducing sugars to pol and often referred to as reducing sugar ratio. Safety Factor A number designed to indicate the probable keeping quality of a fresh raw sugar having a pol of less than 99,0°S. It is calculated by dividing the percentage moisture in the sugar by 100 minus the pol of the sugar. For satisfactory keeping quality the safety factor should have a value less than 0,23.
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Saturated Solution A saturated solution is one which would neither dissolve nor crystallise solute in the presence of undissolved solute. Soil In Cane And Bagasse Inorganic material determined by ashing a sample and correcting for the ash % clean sample. Solubility The concentration of a solute in a solvent in a saturated solution. It is dependent on temperature, the nature and concentration of impurities and in the case of gases, on pressure. Solubility Coefficient Of Sucrose The ratio of the solubility of sucrose in the sample to that in pure water at the same temperature (both expressed as g sucrose/g water). Sugar The main product of a sugar factory consisting of crystals of sucrose as removed from a massecuite and containing more or less impurities, depending on the type of sugar. • Refined sugar: A white sugar as specified in Table 15. • Very high pol sugar (VHP): Raw sugar with a pol of not less than 99,3°S. • High pol sugar (HP): Raw sugar with a pol between 98,0 and 99,3°S. • Low pol sugar (LP): Raw sugar with a pol below 98,0°S. • Brown sugar: A direct consumption raw sugar. • Tel quel sugar: The bulk product without reference to its quality. Sugar Cane Botanically a tall grass of the genus Saccharum and agriculturally the crop produced from hybrids which are the progeny of a number of Saccharum species commonly referred to as cane. Specifically for the determination and distribution of sucrose in cane it is the raw material accepted at the mill for processing. • Clean cane stalk: Cane which has been cut above the highest subterranean roots; has been topped below the level of the growing point; has no leaves or adhering foreign matter and has not died and dried out. • Cane tops: The portion of the stalk above the natural breaking point, plus all green leaves and sheaths attached to that part of the stalk. • Extraneous matter: Any solid material delivered with clean cane stalk, including dead and dried out stalks. • Trash: Leaves and sheaths delivered with the clean cane stalk. Supersaturation Coefficient Of Sucrose The ratio of the concentration of sucrose in the sample to the solubility of sucrose in the sample at the same temperature (both expressed as g sucrose/ g water). Syrup Concentrated clear juice having a brix of between 60° and 70°. Total Solids The solids concentration of an aqueous solution determined either by drying or by analysing for the water content using the Karl Fischer method. See also Dry Substance Wash The diluted liquor thrown off by the centrifugals during washing and/or steaming of massecuites or the total liquor separated from a magma.
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APPENDIX
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