AU740383B2 - Apparatus for crushing cane - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT 0

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Name of Applicant: Actual Inventors: Address for Service: Invention Title: BUNDABERG FOUNDRY ENGINEERS LTD.

009 696 128) Druce Barry BATSTONE Raymond John HATT Beresford Dan EVANS Geoffrey Edmund MITCHELL CULLEN CO., Patent Trade Mark Attorneys, 240 Queen Street, Brisbane, Qld. 4000, Australia.

APPARATUS FOR CRUSHING CANE 1 Details of Associated Provisional Application: No. PP0295 filed 11 November 1997 The following statement is a full description of this invention, including the best method of performing it known to us: 2 The present invention relates to an apparatus and method for crushing sugar cane and in particular is related to a method for modifying an existing mill so as to improve the drainage of sugar juice from the cane.

Sugar juice is removed from sugar cane by crushing the cane in a series of mills. A known type of mill has three rolls in which two adjacent bottom rolls are located beneath a top roll. A blanket of sugar cane or bagasse passes through the rolls in a generally horizontal or slightly inclined manner. Sugar cane is crushed between the top and first bottom roll and the top Se.g. and second bottom roll. A trash or turn plate is S6 normally located between the two bottom rolls to redirect bagasse to the nip of the top and second roll. Another S. known type of sugar cane crushing mill has a pair of •0 vertically aligned rolls and the cane or bagasse moves horizontally therebetween. Juice which is extracted during crushing drains from the bottom roll and with difficulty by lateral flow above the bagasse feed.

•20 To improve the crushing efficiency, it is known to provide grooves in the top and bottom rolls to provide 0e 0 a meshing effect. It is also known to provide juice "*:grooves in the bottom rolls to facilitate juice drainage.

o. These juice grooves are typically formed by cutting a groove to a depth of about 25mm in every second or third groove.

Mills generally have one or more additional pairs of feed rolls in front of the crushing rolls. The feed rolls may be used to increase the rate at which sugar cane or bagasse is crushed between the top and bottom rolls. Juice may be extracted by squeezing cane or bagasse between pairs of feed rolls, as well as between the top and bottom rolls.

Regardless of the amount of juice removed at each successive squeeze, the total juice extracted is known to be a function of the volume reduction in the last squeeze modified by a measure of non-ideal flow of juice and bagasse called the reabsorption factor. Much 3 of the non-ideal flow can be attributed to trapping of juice on top of the bagasse blanket.

A feature common to each of the above known types of rollers is that the lower roll functions to drain most of the sugar juice from the crush. This is primarily because of gravity effects, which causes the extracted juice to flow towards the bottom roll.

However, juice is also extracted by crushing action of the top roll. Juice extracted by the top roll can accumulate on the horizontally moving blanket of cane or bagasse. Contact of extracted juice with the bagasse blanket results in a loss of extraction efficiency as 0 juice can be reabsorbed by the bagasse.

"One method of minimizing contact of extracted SO OS S 15 juice with the blanket is to provide the top roll with drainage holes which extend radially from the crushing ""grooves and connect with longitudinal channels in the roll. The juice enters the drainage holes and exits through the ends of the roll. Such rolls are expensive 20 to manufacture and maintain.

Another proposal which has been put forth to e 00 reduce contact between extracted juice and the moving bagasse blanket is to pass the bagasse blanket through a pair of horizontally aligned rolls. This arrangement is the subject of PCT application no. PCT/AU97/00291. Most often this arrangement necessitates a complete reconstruction of the crushing mill and is not practical for modification of existing mills. Some crushing mills of a conventional configuration that have a top roll and two adjacent bottom rolls may be converted to the more efficient horizontal arrangement if the frame has suitably sized and oriented openings to accommodate larger rolls. The bearing support surfaces of the lower rolls should be horizontal or nearly so.

It is therefore an object of the present invention to provide an apparatus and method for crushing sugar cane which may at least alleviate the above disadvantages or provide the public with a useful choice.

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@05055 It is also an object of the present invention to provide a method for modifying a conventional mill roll so as to improve the extraction of juice therefrom.

The present inventors have discovered that bagasse which has become highly compacted is substantially impermeable to reabsorption of juice. They have also discovered that juice channels in rolls can be configured such that during crushing, a plug of impermeable bagasse can be formed in an upper portion of the channel. This has been described in PCT application no. PCT/AU97/00291.

The present inventors have now also discovered that juice extraction from mills having top and bottom rolls can be improved by providing the top roll with 15 juice channels configured such that a sealing plug of bagasse can form in a first portion of the channel whilst allowing juice to flow in the secondary portion of the channel.

According to a first broad form of the 20 invention there is provided an apparatus for extracting juice from sugar cane, the apparatus having at least two rolls arranged such that in use, a first roll locates above the second roll, and the first roll has at least one peripheral juice channel extending about the roll and 25 into which sugar cane juice can flow, the channel being configured such that a sealing plug of bagasse can form in a first portion of the channel when said bagasse is crushed and the secondary portion of the channel is left free to allow juice to flow, and bagasse plug removing means to remove the plug of bagasse to allow the juice in the channel to drain from the channel at a location where the juice does not contact crushed bagasse.

According to a second broad form of the present invention there is provided a method of extracting juice from sugar cane, the method comprising providing at least two spaced apart rolls in which a first roll is located above a second roll with a crushing zone therebetween, the first roll having at least one peripheral juice channel extending about the roll, passing extracted juice into said at least one juice channel, sealing the channel with a layer of compacted bagasse in the crushing zone of the rollers, rotating the roller to move the sealed channel away from the crushing zone and into a juice collecting zone and removing the bagasse to allow juice to drain from the channel.

The present invention is applicable to any mill arrangement in which cane is crushed between top and bottom rollers. It will be appreciated that the invention is not limited to mills having a pair of rolls and includes mills having two or more rolls. The present invention is also applicable to feed rolls. Providing the top feed roll with juice channels configured to allow 15 a sealing plug of bagasse to form on the upper portion allows additional drainage of juice from the feed roll.

Gutters may be placed over the closed chute to direct S. S juice to a collection pan.

The rolls may be of any suitable size or 20 diameter and the rolls can be made from various materials, a typical material being cast iron.

o• S The top roll is provided with at least one peripheral juice channel. Preferably both the top and bottom rolls have juice channels. It is preferred that the juice channel extends about the full circumference of the roll to facilitate entry of juice into the channel.

The juice channels may be configured in any

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suitable manner which will permit a sealing plug of bagasse to form in an upper part of the channel during crushing. The juice channel may have a narrow necked upper portion. Alternatively the channel may be a U shaped channel having a depth larger than the grooves in conventional rolls. The juice channels are configured such that when a plug of bagasse seals the channels, juice is able to flow in the secondary part of the channel. This means that juice which has been extracted by the top roll and would normally be trapped on the top of the bagasse feeding into the nip between the rolls is able to flow freely within the secondary part of the channel. The juice is able to flow in the same direction as the movement of the roll. The juice may then be removed from the roll at a location away from the crushing zone by removal of the bagasse plug.

The present inventors have also discovered that when juice drains in the same direction as roll movement, the speed of the roll and co-acting rolls may be increased without significant detriment to juice drainage. The crushing capacity may thereby be increased. In conventional rolls, speed is limited as juice flows backward against the flow. The frictional resistance of the roll surface in contact with the juice Sretards the flow of juice. As roll surface speed 0@ SO increases, the retardation effect increases and may overcome gravity so that the juice is carried forward with the roll and contacts the bagasse blanket.

0 In a further form of the invention, conventional mills may be modified to improve juice 20 extraction by replacing the conventional top roll with a roll having juice channels as described above.

S. S Alternatively the existing top roll may be machined to introduce the juice channels and then replaced in the mill.

The apparatus of the present invention also includes bagasse removing means. Typically the bagasse removing means includes a scraper having blades which penetrate the juice channel deeper than the bagasse plug.

Such scrapers and blades having been described in PCT application no. PCT/AU97/00291.

According to a third broad form of the invention, there is provided a method of modifying an apparatus for extracting juice from sugar cane which crushes the cane between top and bottom rolls, the method comprising modifying the top roll to provide at least one peripheral juice channel configured such that a sealing plug of bagasse can form in an upper portion of the channel when said cane is crushed and the lower portion of the channel is free to allow juice to flow and providing a bagasse plug removing means for removing the sealing plug of bagasse so as to allow the juice in the channel to drain from the channel at a location where the juice does not contact the bagasse.

When a mill having one top roll and two bottom rolls is modified as described above, removal of the extracted juice and its continued separation from the discharging bagasse is preferably effected by removal of the second bottom roll and the trash or turn plate and their replacement by a closed discharge chute formed from 00. top and bottom scraper plates that engage with the top 04and first bottom roll. Juice gutters may then be located S0. above the top scraper plate to direct juice to the pan :0000" 15 which normally collects juice draining from the original 0 bottom two rolls.

6:8. The Figure illustrates a three roll mill which 00 has been modified in accordance with the present invention.

S. 20 The Figure illustrates a mill 11 which has two 0pairs 12, 13 of counter rotating rolls. Each roll pair 0 00 0 12, 13 consists of an upper 14, 15 and lower 16, 17 roll.

Each roll includes deep juice channels. The second 0.0. bottom rolls and the associated trash or turn plates have 0 been removed and replaced by a closed discharge chute 18, 19 formed from top and bottom scraper plates 20, 21, 23, 0 000 24 which engage with the top and bottom rolls. Juice 0 gutters are located above the top scraper plates to direct juice draining to the pan that normally collects juice draining from the original bottom rolls. The closed discharge chute may be shaped to approximate the original path of bagasse across the turn plate and through the nip of the top and second bottom roll. By this means the discharging bagasse may be located in approximately the same place in relation to the outline of the crusher as the original.

The setting between the first feed roll and the top roll is made approximately the same as the original U UI 8 setting between the top roll and the second bottom roll such that the volume reduction will be the same and extraction will increase due to the lower reabsorption factor.

In use, crushed or shredded cane is fed into the first set of rolls 12 by conventional means. The blanket of cane or bagasse is crushed between the opposing pairs of rollers. Extracted juice flows into the juice channels, which are then blocked by a plug of bagasse. The juice is then able to flow in the same direction as the rotation of the roll. When the juice 0 has passed the crushing zone, the scrapers remove the SC bagasse plug, which allows the extracted juice to flow from the juice channels and into collection trays.

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S 15 The modifications to the top roll enables improved drainage of juice which improves the .0CC. reabsorption factor. Replacement of the second roll and trash or turn bar with a closed discharge chute brings about the benefits of higher extraction due to improved 20 drainage, a higher crushing rate due to a higher speed and lower maintenance due to removal of one roll and the trash or turn bar.

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Claims (5)

1. 3. The apparatus of claim 1 or claim 2, wherein the juice channel is substantially U-shaped having a 20 depth larger than the-groves in conventional rolls.
2. 4. The apparatus of any one of claims 1 to 3, .0 0 wherein the juice channel has a narrow necked upper *°*portion. A method of extracting juice from sugar cane, the method comprising providing at least two spaced apart rolls in which a first roll is located above a second roll with a crushing zone therebetween, the first roll having at least one peripheral juice channel extending about the roll, passing extracted juice into at least one juice channel, sealing the channel with a layer of compacted bagasse in the crushing zone of the rollers, rotating the roller to move the sealed channel away from the crushing zone and into a juice collecting zone and removing the bagasse to allow juice to drain from the channel.
3. 6. A method of modifying an apparatus for extracting juice from sugar cane which crushes the cane between top and bottom rolls, the method comprising modifying the top roll to provide at least one peripheral juice channel configured such that a sealing plug of bagasse can form in an upper portion of the channel when said cane is crushed and the lower portion of the channel is free to allow juice to flow and providing a bagasse plug removing means for removing the sealing plug of bagasse so as to allow the juice in the channel to drain from the channel at a location where the juice does not contact the bagasse.
4. 7. The method of claim 6, wherein the bottom roll is also modified to provide at least one peripheral juice S. ,channel in and said bagasse plug removing means. S. 8. The method of claim 7, wherein the apparatus to S"be modified has one top roll and first and second bottom S 15 rolls and the apparatus is further modified by removal of aO the second bottom roll and replacing the bottom roll with the bagasse plug removing means for both the top and bottom rolls.
5. 9. An apparatus for extracting juice from sugar S. 20 cane, substantially as hereinbefore described with 9 reference to the Figures. DATED this 11th day of November 1998 BUNDABERG FOUNDRY ENGINEERS LTD. By their Patent Attorneys CULLEN CO. OOSOU