WO2014036597A1

WO2014036597A1 - Processing of sugarcane

Info

Publication number: WO2014036597A1
Application number: PCT/AU2013/000998
Authority: WO
Inventors: Alan Lewis Fitzmaurice
Original assignee: Alan Lewis Fitzmaurice
Priority date: 2012-09-05
Filing date: 2013-09-05
Publication date: 2014-03-13
Also published as: AU2013204686B2; AU2013204686A1

Abstract

In processing sugar cane juice from mill (33) is delivered to the shredder (26) at (44), The shredder (26) has shredded cane leaving the shredder at a velocity of over 40 m/s and typically 70 m/s at (45) against the chute (27). The arrows (46) serve to illustrate the kinetic energy with which this shredded cane is driven into the receiver (28). The release of this kinetic energy causes juice to be expelled through the bottom section of perforated drain (47) into the collector (48) and then to outlet (49). As the shredded cane in the receiver region (28) is swept up by the rake tines (31) it carries with it remaining juice which is substantially concentrated in a lower region of the shredded cane mat in the conveyor (29). The addition of maceration liquid by the maceration liquid delivery means (40) and (41) serves to displace this remaining juice from the shredded cane mat. The first stage of juice extraction arises from the physical impact of the shredded cane with the chute in the receiver. The next stage of juice extraction involves maceration of the cane mat as it is conveyed by the conveyor. In order for this to be as efficient as possible it is important that the cane mat be relatively uniform and free of voids and be relatively level.

Description

PROCESSING OF SUGARCANE

FIELD OF THE INVENTION

[0001] THIS INVENTION relates to the processing of sugarcane to remove juice from the cane.

BACKGROUND TO THE INVENTION

[0002] In a sugar mill tandem, cane is shredded and fed through the milling tandem comprising a number of mills in series. In order to improve juice extraction, water is added to bagasse (cane fibre plus brix) in front of the last mill in the tandem and after extraction by this mill is then pumped forward to in front of the next previous mill and then on through previous mills, until in front of the second mill where along with the juice extracted in the first mill this mixture is then sent on to further processing via heaters, clarifier(s), evaporator(s) and a crystallising process.

[0003] Most of the juice is extracted in the first mill so the present invention has as its object to improve the efficiency of the extraction at or just before the first mil) by managing the addition of the mill liquid from the first and second mills as applied to the shredded cane at or adjacent the first mill.

OUTLINE OF THE INVENTION

[0004] In one aspect therefore, the present invention resides in a method of applying relatively low concentration liquid generated in a following mill to shredded cane upstream of Ihe following mill by applying the liquid over a surface of the shredded cane at a rate determined to displace relatively high sugar concentration liquid from the shredded cane.

[0005] In one example to be described in detail below the present invention resides in a method of applying a very large volume of juice from the first mill (ideally) pressure feeder to provide sufficient volume of juice in the shredded cane to create drainage through the shredded cane equal to the imbibition rate, (added water in front of the last mill in the tandem) then to add relatively low concentration liquid extracted by the second mill to the shredded cane downstream of the juice added from the first mill by applying the liquid over a surface of the shredded cane to displace relatively high sugar concentration liquid from the shredded cane.

[0006] In another aspect there is provided a sugarcane processing plant including a sugarcane comminution means upstream of a conveyor, the comminution means delivering comminuted cane and juice entrained therein to the conveyor in a direction of travel, a cane receiver upstream of the conveyor receiving the comminuted cane and juice entrained therein at a velocity adapted to cause juice to separate from the comminuted cane upon reaching the receiver, the comminuted cane and the remaining juice entrained therein being conveyed by the conveyor in a downstream direction, the remaining juice being of a relatively high sugar concentration, applying a relatively low sugar concentration liquid to the comminuted cane with the remaining juice entrained therein as it is being conveyed, the rate of application of the relatively low sugar concentration liquid and the volume of conveyed cane and the rate of travel of the conveyor being so selected that the relatively low sugar concentration liquid displaces the relatively high concentration liquid from the conveyed cane while retaining all or a major portion of the relatively low sugar concentration liquid in the conveyed cane.

[0007] Typically, the comminution means comprises a shredder and the output of the shredder is shredded cane delivered at a speed to generate enough kinetic energy so that upon impact with the receiver, juice is expelled from the shredded cane. The receiver typically comprises a chute or passage aligned with a tangential exit to the shredder and providing an impact surface against which the shredded cane is driven and thereafter collected in a collection region, where it automatically collects, accumulates and compacts before being engaged by rake tines on the conveyor.

[0008] Preferably, the collection region is effectively choke fed and the rate of travel of the conveyor is matched to the volume flow rate of cane from the shredder so that the desired cane density on the conveyor is matched for optimum efficiency.

Typically, the conveyor speed is proportional to the measured load on the shredder so that the desired uniformity of the shredded cane on the conveyor is achieved. [0009] The conveyor is typically inclined to the horizontal in order to enhance maceration and displacement of the relatively high sugar concentration juice.

Typically the inclination is less than about 30°.

[0010] The conveyor typically has closely spaced rake tines and levelling tines in order to create a uniform bed of conveyed cane.

[0011] In one example to be described below there is provided a sugarcane processing plant including a sugarcane shredding operation upstream of a conveyor. For all lypes of juice extraction systems, the higher the percentage of cane juice cells opened by the shredding operation, the greater the potential juice extraction percentage relative to the total pol (sugar) in the cane entering the tandem.

[0012] After the shredding operation the shredded cane enters a conveyor that delivers the shredded cane to the first mill in the tandem.

[0013] This conveyor needs to allow for drainage of liquid from the shredded cane, collect the drained juice and add it to the juice from the No 1 mill that is pumped to process, ideally have a constant height of shredded cane without gaps in the shredded cane and deliver the shredded cane upward for delivery into the vertical hopper feeding the first mill. Ideally the longer this conveyor is the greater the drainage of juice from the shredded cane mat in the conveyor, and the lower the angle of the conveyor.

[0014] Ideally, a cane shredder should be used to open the highest percentage of juice cells possible. And ideally this shredder should be mounted above the entrance point of the conveyor.

[0015] Ideally, the velocity of the shredded cane leaving the shredder (typically 50 meters per second to 80 meters per second) should cause a high impact velocity against the curved entrance end of the conveyor floor. This high impact velocity of the shredded cane will cause much of the cane juice (now freed from juice cells in the cane) to penetrate through much of the shredded cane mat in the conveyor to the bottom region of the shredded cane mat in the conveyor.

[0016] Ideally, extracted juice from a feeding system on the first mill, example, a pressure feeder, is collected and delivered to the top surface of the shredded cane mat just after the entrance point of the shredded cane from the shredder. Ideally this juice flow should be delivered onto the surface of the shredded cane mat in the conveyor and not be forcefully applied to the surface.

[0017] This added juice then flows downward through the bagasse mat at the mat moves along the bottom of the conveyor, until it sits over the freed cane juice and forces this cane juice through the porous bottom of the conveyor. The added juice will also mix with the cane juice in the higher section of the shredded cane mat and take this cane juice down through the shredded cane mat.

[0018] What juice does not drain out of the shredded cane mat enters the No. 1 mill feeding system and after extraction by the feeding system is delivered to the shredded cane mat as described above. The volume of No. 1 mill feeder juice therefore builds up until the quantity of drained juice from the bottom of the conveyor almost equals the volume of added water prior to the last mill.

[0019] Instead of having the juice extracted by the No 2 mill added to the juice extracted by the No 1 mill prior to delivery to the process side of the factory, as is typical for a milling tandem, the juice from the No 2 mill flows onto the surface of the cane mat in the conveyor just after the entry point of the juice from the No 1 mill feeder.

[0020] Typically, juice in the shredded cane has a brix (dissolved solids) reading of about 18 brix.

[0021] Typically, juice from the No 2 mill has a brix of about 8 units.

[0022] So part of the design of this extraction system is to have much of the shredded cane juice in the lower part of the shredded cane mat, the recirculated No 1 mill feeder juice flowing down through the cane mat, and the lower brix juice from the No 2 mill applied after the addition point of the No 1 mill feeder juice, so as to reduce mixing of the three listed streams of juices and have the flows through the bottom of the conveyor, shredded cane juice, followed by No 1 mill feeder juice, followed by No 2 mill juice.

[0023] Ideally, much of No 2 mill juice should remain in the shredded cane mat that enters the No. 1 mill feeder, and most of the freed shredded cane juice should flow through the perforated bottom of the conveyor.

[0024] To Improve the pol extraction performance of this pre mill juice extraction system, a weighted roller can be installed to sit on the shredded cane mat in the conveyor, between the entry point of the No 1 mill feeder juice supply and the No 2 mill juice supply to squeeze out some of the No 1 mill feeder juice plus shredded cane juice, before the No 2 mill juice is added.

[0025] This same maceration system can also be used in the conveyors between the various mills in the tandem.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order that the present invention may be more readily understood and be put into practical effect reference will now be made to the accompanying drawings and wherein :-

Figure 1 is a schematic drawing used to illustrate the prior art;

Figure 2 is a schematic drawing serving to illustrate one embodiment of the present invention before cane is introduced;

Figure 3 is the drawing of Figure 2 with cane;

Figure 4 is a drawing illustrating part of Figure 3 and the mills downstream of Figure

³;

Figure 5 is a drawing illustrating a device for applying the relatively low sugar concentration juice to the conveyed cane; Figure 6 is a drawing illustrating the uniform mat of cane on the conveyor;

Figure 7 is a close-up drawing schematic illustrating the principle employed by the present invention whereby the relatively low concentration juice displaces the relatively high concentration juice rather than mixing with it; and

Figure 8 is a further illustration of the juice displacement principle whereby efficiency is improved.

METHOD OF PERFORMANCE

[0027] Referring to the drawings and initially to Figure 1 there is illustrated a hypothetical milling tandem 10 comprising four mills 1 1 , 12, 13 and 14. The first and fourth mills are six roll mills, the second a four roll mill and the third a three roll mill. Typical milling tandems comprise tandems of six, four or three roll mills or any combination of these.

[0028] A cane conveyor 15 delivers washed cane to 16 where it is shredded in a shredder 17 then conveyed by conveyor 18 to be crushed in the first mill 1 1. It is to be noted that juice is extracted at 19 to be delivered to the next stage in the process from the first and second mills only. In this case imbibition water is added to the third mill at 20 and this imbibitions liquid is used to mix with juice in the bagasse leaving the mill and results in a low sugar concentration solution collected at 21 and delivered to the first mill at 22. Similarly, liquid from mill 14 at 23 is applied to mill 12 at 24.

[0029] The present invention is preferably employed in the area of the conveyor 18 upstream of the first mill. This will be described in greater detail below.

[0030] Referring to Figure 2 there is illustrated a sugarcane processing unit 25 comprising a comminution means in the form of a shredder 26, a chute 27 and a shredded cane collection region 28 leading to a conveyor 29. The conveyor 29 is an endless chain conveyor and has endless chains 30 carrying spaced rake tines 31 adapted to sweep shredded cane from the region 28 and convey cane to the first mill chute 32 where it is delivered to the first mill. In this case the first mill is a six roll mill 33, mill 33 is the first mill in a milling tandem, the following mills being shown in Figure 4. The conveyor 29 has a driven sprocket assembly at 34 and an idler at 35.

[0031 ] Similar to Figure 1 , maceration liquid from the following mills is introduced along the line 36 and juice from mill 33 is introduced along line 37.

[0032] Rubber belt curtains 38 and 39 are used to seal the conveyor against windage from the shredding process. Maceration liquid delivery means 40 and 41 , to be described in greater detail below, are used to deliver maceration liquid to the conveyed shredded cane at 42 and 43 respectively.

[0033] In Figure 3 the juice from mill 33 is delivered to the shredder 26 at 44. The shredder 26 has shredded cane leaving the shredder at a velocity of between about

40 m/s to about 100 m/s with over 40m/s or 50 m/s and typically 70 m/s at 45 against the chute 27. The arrows 46 serve to illustrate the kinetic energy with which this shredded cane is driven into the receiver 28. The release of this kinetic energy causes juice to be expelled through the bottom section of the shredded cane mat where it can be washed through the perforated bottom or drain 47 of the conveyor into the collector 48 and then to outlet 49. As the shredded cane in the receiver region 28 is swept up by the rake tines 31 it carries with it remaining juice which is substantially concentrated in a lower region of the shredded cane mat in the conveyor 29. The addition of maceration liquid by the maceration liquid delivery means 40 and

41 serves to displace much of this remaining juice from the shredded cane mat.

[0034] The first stage of juice extraction arises from the physical impact of the shredded cane with the chute in the receiver. The next stage of juice extraction involves maceration of the cane mat as it is conveyed by the conveyor. In order for this to be as efficient as possible it is important that the cane mat be relatively uniform and free of voids and be relatively level. This will be described in great detail below.

[0035] In the meantime in order to complete description of the overall tandem, in general terms Figure 4 illustrates the milling tandem downstream of the arrangement of Figures 2 and 3. Imbibition water is introduced at 50 and progressively cycled back to previous mills until it reaches 36 in Figures 2 and 3.

[0036] Referring to Figure 5 there is illustrated the general arrangement of the maceration liquid delivery means 40 and 41 whereby line 36 and 37 feed maceration liquid 51 onto a curved metal plate 52 so that it flows evenly onto the mat of shredded cane on the conveyor 29. The plate 52 is pivotally mounted to the tank 53 in order to accommodate slight variations in the upper surface of the shredded cane mat being conveyed by the conveyor 29. The underside of this plate may include levelling means to aid flattening of any bumps in the sugarcane mat on the conveyor 29. Alternatively the plate 52 may be controlled in accordance with a drive means adapted to apply a controlled force to the plate in accordance with variables which may be measured from time to time including load on the shredder. Other ^y arrangements may be used in conjunction with the operation of the conveyor {speed control of the conveyor) in order to ensure a uniform and level conveyed shredded sugarcane mat 54.

[0037]lt will be appreciated that the curved end of the conveyor directs the fast moving shredded cane against the back side of the rakes 31 in the conveyor to make it easier to fill the section between the rakes and have a level to on the shredded cane mat 54 in the conveyor.

[0038] As depicted in Figure 6 the shredded cane mat 54 is fairly uniform and fills the space between each of the rake tines 31 in uniform fashion above the perforated plate 47 above drainage plate 48, as can be seen the relatively high sugar concentration liquid is shown at 55 being displaced from the lower region 56 of the mat 54 as the cane mat progresses up the conveyor 29. The effect of the maceration liquid entering the shredded cane mat 54 is illustrated schematically in Figure 7 whereby the relatively low sugar concentration liquid is shown flowing across plate 52 onto the relatively uniform shredded cane mat 54 and rather than "striking through" the mat and mixing with the relatively high sugar concentration liquid already in the mat, it forms a layer which displaces the relatively high concentration liquid. The liquid represented by the arrows 55 occupies an upper layer 56 and progressively displaces the relatively high sugar concentration liquid from the mat 54.

[0039] In turn the conveyed cane reaches the next curved plate 52 at delivery means 43 and this adds a further layer of liquid to the mat which in turn serves to displace the two layers below it. This is shown diagrammatically and schematically in Figure 8. Thus as will be appreciated in Figure 8, a small section of the length of the conveyor is shown, and by selection of the angle of the inclination of the conveyor 29, the depth of the sugarcane mat 54, the speed of the conveyor and the rate of flow of liquid onto plates 52, that it is possible to displace the high concentration liquid in the mat, from the mat, while retaining the lower concentration maceration liquid in the mat as it reaches the top conveyor.

[0040] Thus the concentration of sugar in the juice sent to process will be higher than otherwise would be the case and the milling process more efficient. It will be appreciated that the delineation between the layers illustrated in Figure 8 is for the purposes of illustration only but it will be appreciated that there are a number of variables set out above in relation to the conveying of the shredded cane along a conveyor of the type illustrated, and that by suitable and reasonable trial an experiment these variables may be optimised to ensure that the efficiency is maximised.

[0041] Applicant has found the following important features and aspects arising from the present invention.

• [0042] Depending on the shredder drive power, some or all of the No. 1 mill pressure feeder juice can be added to the cane entering the shredder to improve mixing of the pressure feeder juice and the displaced cane juice. This added juice will increase the kinetic energy of the mixed juice leaving the shredder at high speed so after impacting onto the floor of the conveyor under the shredder with the cane fibre, (shredded cane) the mixed juice will be forced through much of the cane fibre to the lower part of the shredded cane mat in the conveyor. The high velocity of the shredded cane leaving the shredder (over 50 meters per second) impacts on the floor of the shredded cane conveyor causing the >90% of high brix (typically about 18 brix) freed juice to penetrate through much of the shredded cane mat towards the bottom layer of this shredded cane mat.

[0043] The high velocity shredded cane leaving the shredder should, preferably flow into the shredded cane conveyor between the idler rake and chain shaft and sprockets, and the end wall of this conveyor. The shredded cane will then impact on the curved bottom of the conveyor and be turned to fill any voids behind the conveyor rakes. This set-up would not be necessary for a belt conveyor or a chain and slat type conveyor.

[0044] It is important to have a continuous feed in the conveyor with a constant shredded cane mat height. To assist with controlling this constant height of shredded cane in the conveyor, the cane rate can be controlled by the load on the shredder drive rather than by chute height control at the first mill .

[0045] The load on a shredder drive is proportional to the tonnes of material passing through the machine. So by controlling the .speed of the cane supply conveyor feeding the shredder to give a constant load on the shredder the flow of shredded cane from the shredder will be much more even than that from a rate control from the No 1 mill chute height control. An adjustable set point on this control can then provide the required cane rate for the factory.

[0046] The speed of the shredded cane conveyor would then be variable, but controlled by a sensor to give a constant height of shredded cane in this conveyor. The No 1 mill speed would be controlled by chute height level of shredded cane. Higher level causes the mill to run faster while low level causes the mill to operate at a slower speed. [0047] A large volume of recirculating first mill pressure feeder juice (this juice is preferred) flows onto the top of the shredded cane mat just after the position of the idler sprocket shaft and flows downward through the mat of prepared cane to drainage slots in the floor of this conveyor. This downward flow of pressure feeder juice forces much of the freed cane juice to also flow through these drainage slots in the conveyor floor, creating an extraction process.

[0048] Low brix juice from the No 2 mill flows onto the top of the shredded cane mat after the entry position of the pressure feeder juice. This low brix juice flows downward through the mat forcing much of the pressure feeder juice to flow downward in front of the low brix juice and through the drainage slots in the conveyor.

[0049] A drainage tray under the shredded cane conveyor floor, collects the juice that flows through the slots in the floor. This juice is then added to the juice extracted by the No 1 mill and is pumped away to process.

[0050] The rake tines should be short to allow a type of leveller to be used to level the surface of the shredded bagasse in the conveyor.

[0051 ] A low grade stainless steel floor in the conveyor will be smoother and reduce the packing of shredded cane against the front of the rakes due to rubbing friction on the floor of the conveyor.

[0052] Aim to have minimum variation in the surface height of the shredded cane (bagasse) in the conveyor between the shredder and the first mill, or for the bagasse mat in the conveyors between mills.

Variation in the height of the shredded cane or bagasse mat varies the percolation rate of juice through the mat. And if there are gaps in the mat the maceration liquid will flow through the bottom of the conveyor with no beneficial effect. If possible, have a long conveyor between the shredder and the first mill or between mills, to increase the drainage time. The angle of this conveyor should be less than 30 degrees if possible. • [0053] The pressure feeder juice should flow onto the shredded cane mat immediately after the leveling device so it is above the free cane juice in the shredded cane mat below. It is better not to mix the lower brix maceration juice from the second mill with the higher brix first mill pressure feeder juice which is below, or mix the pressure feeder juice with the higher brix cane juice which is below the pressure feeder juice. Hydraulic head and the large juice volumes which are much greater the quantity from where free flow occurs, creates a drainage volume equal to the volume of maceration from the second mill. This drainage includes much of the cane juice due to it being the bottom layer of the three different juice supplies. The rakes in this conveyor should be as close as possible. Preferably no more than 600mm centres to reduce the wave shaped top of shredded cane or bagasse in a conveyor. The shredded cane or bagasse tends to slide back against the trailing rake and leave a hollow or bare space behind the forward rake pile. An even height on the surface of the prepared cane will give a more even flow rate of the pressure feeder juice or No 2 mill juice (maceration) through the shredded cane mat with less juice passing through uncovered sections of conveyor floor behind each rake.

• [0054] An even flow of No 2 mill juice onto the reasonably level shredded cane mat will provide an even hydraulic head pressure to help force the lower level cane juice plus the higher level pressure feeder juice through the drainage slots in the bottom of the conveyor. It is important to remove the higher brix juices and leave as much of the low brix No 2 mill juice in the mat feeding into the first mill pressure feeder, or any other mill pressure feeder. The flat surface on the shredded cane mat in the conveyor plus the even flow of No 2 mill juice through the shredded cane mat will improve the macerationefficiency, and therefore the pol extraction of this extractor located before thefirst mill. The inventor uses the impact of the high output velocity (>80 meters / second) of the shredded cane onto the conveyor floor to force, via the juice inertia, the high brix cane juice through the fibre mat to closer to the bottom of the conveyor. The recirculated lower brix pressure feeder juiceflows on top of the shredded cane mat and flows downward, due to the volume being much greater than the volume shredded cane can hold withoutfree draining. This rapid downward flow has a hydraulic effect that forces much of the free cane juice plus pressure feeder juice to pass through the drainage slots in the bottom of the conveyor where it is collected on a drainage tray then

pumped away to process with the juice extracted by the first mill.

• [0055] Use low level rakes with a high number of rake tines, to reduce the amount of "sloppy" shredded cane that may bypass the rakes tines, and not to have open air pockets for juice to flow freely through the bagasse mat. The low level of the rakes allows a leveling device to operate without interference with the tops of the rakes.

[0056] To get an even flat surface on the bagasse mat moving up the conveyor the following procedures is used:

1 . [0057] The flow of shredded cane from the shredder should enter the

conveyor at an angle to the bottom surface of the conveyor in the direction of travel of the conveyor, so the impacting flow fills the void behind each rake.

2. [0058] Use a leveler (rotary, fixed or floating rake type, or hopper) to flatten and level any hills on the bagasse mat after the flow from the shredder, and to fill any voids behind the rakes.

4. [0059] Have a control system that controls the speed of the conveyor to

keep the set height of shredded cane in the conveyor, and a higher level of shredded cane before the leveling device.

5. [0060] Have a control system from the mill top roller to vary the speed of the following bagasse conveyor to vary the flow of bagasse into the conveyor dependent on the fibre rate passing through the mill.

6. [0061 ] Preferably, use the load on the shredder drive, (it will give a more even milling rate with much faster response compared to that of the first mill chute height control) as this load is directly proportional to cane rate to control the cane rate into the factory. The speed of the conveyor between the shredder and the first mill should be tied to the speed of the cane conveyor before the shredder to control the level of cane in the shredded cane conveyor. The speed of this conveyor should be varied automatically if the pile of shredded cane in front of the leveler is too high or too low.

[0062] As an example of the typical operation of the system the performance of the illustrated embodiment depends on a number of variables including the particular type of cane, (fibre %, Juice %, sucrose % and molasses %) as well as the percentage of cane juice separated from fibre cells in the shredder and the quantity of water added before the last mill. Alter any of these inputs and the results will be different.

[0063] The aim of this apparatus is to force the high pol cane juice towards the bottom of the mat of shredded cane in the conveyor due to inertia, recirculate a large quantity of liquid from the first mill's pressure feeder in a way that it flows through the bagasse mat from the top surface to the bottom in a quantity large enough that it forces as much of the cane juice through the slots in the bottom of the conveyor as possible. Then add the low pol juice from the second mill to the top of the bagasse mat and have it force some, by displacement, of the pressure feeder juice through the bottom of the conveyor.

[0064] In a normal milling tandem the juice from the No 2 mill goes away for process with the juice from the No 1 mill.

[0065] The volume of juice the pressure feeder adds to the conveyor builds up, with recirculation, in the conveyor until it is sufficient to create drainage through the conveyor. Therefore it is certain that this flow through the conveyor will carry much of the cane juice through as well, thus improving the pol extraction performance of the milling tandem.

[0066] When referring to "the volume of juice in the conveyor builds up until drainage occurs", this mean that the embodiment described in general above, is operated so that the shredded cane mat contains about 13% fibre, and the rest is a mixture of liquid sugar (typically about 12%), molasses (typically about 3%) and water (typically about 72%), or 87% liquid. In order to achieve the desired drainage there is about 5 times the quantity of liquid as fibre. So the juice from the No 1 mill pressure feeder gradually increases the liquid content until drainage occurs. Note, the pressure feeder extracts much of this juice and returns it back to the conveyor thereby building up the juice volume in the conveyor.

[0067] When the drainage equals the volume of juice from the No 2 mill the flows will then remain constant. The juice flow from the No 2 mill is about equal to the quantity of water added to the bagasse (mixture of fibre and low pol juice in the fibre mat passing through the milling tandem). This quantity is typically about 220% by weight to fibre, about 29 tonnes per hour for a cane rate of 100 tonnes per hour.

[0068] So the flow through the extraction system based on 100 tonnes of cane entering the conveyor per hour, through the bottom of the conveyor would be about 77 tonnes per hour, based on removing about 40% of the cane juice.

[0069] Whilst the above has been given by way of illustrative example of the present invention many variations and modifications thereto will be apparent to those skilled in the art without departing from the broad ambit and scope of the invention as set out in the appended claims. In addition in the present specification words" comprised", "comprising", "including" and similar words used herein are non-limiting and are used in the non-exhaustive inclusive sense, that is to say they do not mean "made up of but rather "include".

Claims

1 . A sugarcane processing plant including a sugarcane comminution means upstream of a conveyor, the comminution means delivering comminuted cane and juice entrained therein to the conveyor in a direction of travel, a cane receiver upstream of the conveyor receiving the comminuted cane and juice entrained therein at a velocity adapted to cause juice to separate from the comminuted cane upon reaching the receiver, the comminuted cane and the remaining juice entrained therein being conveyed by the conveyor in a downstream direction, the remaining juice being of a relatively high sugar concentration, applying a relatively low sugar concentration liquid to the comminuted cane with the remaining juice entrained therein as it is being conveyed, the rate of application of the relatively low sugar concentration liquid and the volume of conveyed cane and the rate of travel of the conveyor being so selected that the relatively low sugar concentration liquid displaces the relatively high concentration liquid from the conveyed cane while retaining all or a major portion of the relatively low sugar concentration liquid in the conveyed cane.

2. A sugarcane processing plant according to claim 1 wherein the comminution means comprises a shredder and the output of the shredder is shredded cane delivered at a speed to generate enough kinetic energy so that upon impact with the receiver, juice is expelled from the shredded cane.

3. A sugarcane processing plant according to any one of the preceding claims wherein the conveyor has an endless chain Or belt carrying rake tines and receiver comprises a chute or passage aligned with a tangential exit to the shredder and providing an impact surface against which the shredded cane is driven and thereafter collected in a collection region, where it automatically collects, accumulates and compacts before being engaged by the rake tines on the conveyor.

4. A sugarcane processing plant according to any one of the preceding claims wherein the collection region is effectively choke fed and the rate of travel of the

conveyor is matched to the volume flow rate of cane from the shredder so that the desired cane density on the conveyor is matched for optimum efficiency.

5. A sugarcane processing plant according to any one of the preceding claims wherein the conveyor speed is proportional to the measured load on the shredder so that the desired uniformity of the shredded cane on the conveyor is achieved.

6. A sugarcane processing plant according to any one of the preceding claims wherein the conveyor is typically inclined to the horizontal in order to enhance maceration and displacement of the relatively high sugar concentration juice.

7. A sugarcane processing plant according to any one of the preceding claims wherein the conveyor is typically inclined to the horizontal in order to enhance maceration and displacement of the relatively high sugar concentration juice the inclination being less 1han about 30°.

8. A sugarcane processing plant according to any one of the preceding claims wherein the conveyor typically has closely spaced rake tines and levelling tines in order to create a uniform bed of conveyed cane.

9. A sugarcane processing plant according to any one of the preceding claims wherein comprising a comminution means in the form of a shredder, a chute and a shredded cane collection region leading to a conveyor, the conveyor being an endless chain conveyor carrying spaced rake adapted to sweep shredded cane from the collection region and convey cane to a first mill chute where it is delivered to a first mill, the conveyor have a drive and being set to travel at a predetermined speed, maceration liquid pipe means delivering maceration liquid from a following mills is introduced along the pipe and juice from the following mill introduced along to the cane on the conveyor.

10. A sugarcane processing plant according to any one of the preceding claims wherein maceration liquid from a following mill is introduced along a pipe and juice from the following mill introduced along to the cane on the conveyor via a delivery means spreading the liquid evenly over the cane on the conveyor.

11 . A sugarcane processing plant according to any one of the preceding claims wherein maceration liquid from a following mill is introduced along a pipe and juice from the following mill introduced along to the cane on the conveyor via maceration liquid delivery means whereby pipes feed maceration liquid onto a curved metal plate so that it flows evenly onto the mat of shredded cane on the conveyor.

12. A sugarcane processing plant according to any one of the preceding claims wherein maceration liquid from a following mill is introduced along a pipe and juice from the following mill introduced along to the cane on the conveyor via maceration liquid delivery means whereby pipes feed maceration liquid onto a curved plate so that it flows evenly onto the mat of shredded cane on the conveyor, the plate being pivotally mounted to a tank in order to accommodate slight variations in the upper surface of the shredded cane mat being conveyed by the conveyor.

13. A sugarcane processing plant according to any one of the preceding claims wherein maceration liquid from a following mill is introduced along a pipe and juice from the following mill introduced along to the cane on the conveyor via maceration liquid delivery means whereby pipes feed maceration liquid onto a curved plate so that it flows evenly onto the mat of shredded cane on the conveyor, the plate being pivotally mounted to a tank in order to accommodate slight variations in the upper surface of the shredded cane mat being conveyed by the conveyor, the plate having an underside including levelling means to aid flattening of any bumps in the sugarcane on the conveyor.

14. In a sugar cane milling tandem a method of applying relatively low

concentration liquid generated in a following mill to shredded cane upstream of the following mill by applying the liquid over a surface of the shredded cane as the cane travels up a conveyor, the liquid being applied at a rate determined to displace relatively high sugar concentration liquid from the shredded cane.

15.The method of claim 14 using a processing plant according to any one of claims 1 -13.