AU743560B2

AU743560B2 - Apparatus for dewatering a bagasse bed

Info

Publication number: AU743560B2
Application number: AU28044/99A
Authority: AU
Inventors: Werner Gruenewald
Original assignee: BMA Braunschweigische Maschinenbauanstalt AG
Current assignee: BMA Braunschweigische Maschinenbauanstalt AG
Priority date: 1998-06-20
Filing date: 1999-05-11
Publication date: 2002-01-31
Anticipated expiration: 2019-05-11
Also published as: GB2338430A; AU2804499A; GB2338430B; DE19827599C1; ZA993411B; GB9911093D0

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990 *r 4

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT 4* Invention Title: "APPARATUS FOR DEWATERING A BAGASSE BED" The following statement is a full description of this invention, including the best method of performing it known to us: Apparatus for dewatering a bagasse bed The invention relates to an apparatus for the bagasse bed at the end of a conveyor-like diffuser, having an expressing roll in the form of a screening roll which extends at right angles to the conveying direction over the entire width of the diffuser, presses with its dead weight from above upon the bagasse bed moving towards the diffuser end and takes up expressed liquid.

In the cane sugar industry diffusers are employed, which extract sucrose from chopped sugar cane using a counter- "current process. Said process is assisted by imbibition water heated to 750, which at the end of the conveyor-like diffuser ••co 15 is fed onto the bagasse (extracted, chopped sugar cane with a high fibre content) moving downstream, then percolates through the bagasse and in so doing extracts residual sucrose fractions from the bagasse. The imbibition liquid after passing out of the bagasse is collected in a trough, pumped 20 counter to bagasse-conveying direction into the downstream percolation stage and fed once more to the bagasse. Said operation is repeated a plurality of times until the percolation liquid, which in the meantime is increasingly enriched with sucrose, reaches the diffuser start and is e e pumped into the sugar factory for further processing.

In order to reduce the high liquid content of the bagasse prior to its leaving the diffuser, in previously known diffusers an expressing roll is provided, which covers the entire diffuser width, presses with its dead weight from above onto the bagasse bed moving towards the diffuser end and by virtue of the pressing effects an increased removal of liquid from the bagasse. By filling cavities provided in the expressing roll with water, sand or the like, the pressing force may be additionally increased. The expressed liquid flows off through a bottom screen, which is situated under the bagasse bed and through which the liquid of all further percolation stages also flows. As a result of the pressure exerted by the above-lying expressing roll, however, liquid also flows onto the surface of the bagasse bed and remains in the bagasse, thereby increasing the residual moisture of the bagasse upon its leaving the diffuser.

The initially described apparatus may be inferred from DE-OS 1 567 245. In said prior publication the possibility is indicated of designing the expressing roll as a screening roll from which surface liquid, which has flowed in, is then to be extracted or pumped.

S* Proceeding from the initially described apparatus, the object the invention is to reduce the residual moisture of the bagasse upon its leaving the diffuser.

S"According to the invention said object is achieved in that welded onto the cylindrical sleeve of the expressing roll are paraxial drainage channels which have a cross section tapering conically in a radially outward direction, are provided in their two longitudinal walls with perforations and with their, in each case, open channel ends rotate past perforated diffuser side walls, through which the liquid taken up by the drainage channels and flowing back out of their channel ends is removed into a liquid collecting trough.

In an alternative solution based on the same invention principle, said object is achieved in that the expressing roll is provided with a double-walled sleeve, wherein the outer sleeve is perforated and supported upon the closed inner sleeve via paraxial webs, between which is formed in each case a drainage channel, wherein the drainage channels rotate with their, in each case, open channel ends past perforated diffuser side walls, through which the liquid taken up by the drainage channels and flowing back out of their channel ends is removed into a liquid collecting trough.

The arrangement and design of the drainage channels lead to an increased dewatering of the bagasse bed at the end of the diffuser, wherein said effect may be further intensified by virtue of the radial height of each drainage channel uniformly increasing axially from a minimum value in the middle of the roll to a maximum value in each case at the channel end. By virtue of the gradient thus created in the drainage channels, the liquid taken up by said channels is totally removed from the drainage system.

The increased amount of liquid removed collects in the last collecting trough of the diffuser, is then pumped to the "'upstream extraction or percolation stage and reaches a higher "'"degree of extraction through increased imbibition in the 15 treated bagasse. The bagasse leaves the diffuser with a reduced liquid content. The reduction according to the S"invention of the residual moisture of the bagasse reduces the load upon the subsequent multi-roll mills for residual 20dewatering of the bagasse and increases the gross calorific value of the bagasse, which is to be subsequently burnt in steam boilers, so that more steam per bagasse unit may be produced then before. Furthermore, the lower residual moisture of the bagasse results in increased extraction of residual sucrose in the dewatering mill. Finally, the steam oooo• consumption for maintaining the diffusion temperature of e.g.

750 C is, according to the invention, lower than in the previously known apparatuses.

The conically tapering cross section of the drainage channels provided according to the invention prevents dead corners and cavities or regions of inadequately compressed bagasse, where liquid might otherwise be retained.

Further features of the invention are the subject matter of the sub-claims and are, together with further advantages of the invention, described in detail with reference to embodiments.

4 Several forms of construction of the invention serving as examples are illustrated in the drawings. The drawings show: Figure 1 Figure 2 Figure 3 o ooo oo o ee Figure 4 Figure 5 in side view, a pivotally mounted expressing roll; a longitudinal section through a left end portion of a diffuser and through the left end of the expressing roll according to Figure 1; to an enlarged scale compared to Figure 1, a cross section through a triangular drainage channel; in a view according to Figure 3, a trapezoidal drainage channel dipping into a bagasse bed; to a reduced scale compared to Figure 4, a diagrammatic longitudinal section through an expressing roll equipped with the drainage channels according to Figure 4; a side view of the expressing roll according to Figure in a modified form of construction, an expressing roll in a view according to Figure 5, and a cross section through the expressing roll according to Figure 7.

Figure 6 Figure 7 Figure 8 Figures 1 and 2 show an apparatus for dewatering the bagasse bed 1 at the end of a conveyor-like diffuser 2, having an expressing roll 3 which extends at right angles to the conveying direction over the entire width of the diffuser and presses with its dead weight from above onto the bagasse bed 1 moving towards the diffuser end.

Welded onto the cylindrical sleeve of the expressing roll 3 are paraxial drainage channels 4, which are peripherally spaced apart from one another and according to Figure 3 have a triangular cross section with a rounded apex 4a. The two triangle sides of each drainage channel 4 are provided with perforations 5, while the said apex 4a is free of perforations. The drainage channels 4 pressing into the bagasse bed 1 take up surface liquid of the bagasse bed 1 and convey said expressed liquid 6 (see also Figure 4) through their, in each case, open channel ends 7 to perforated diffuser side walls 8, past which the open channel ends 7 rotate. The liquid flowing off from the drainage channels 4 through said lateral screens passes into a liquid collecting trough 9 and is removed from there e.g. to a tank.

It is further evident from Figure 3 that the perforations or their flow area increases from the outside in the direction of the interior of the drainage channel 4.

e 99 9 Figure 4 shows a drainage channel 10 with a trapezoidal cross section, wherein the two longitudinal walls starting from the roll sleeve are perforated only to 2/3 of their height.

The channel base 10a is closed.

oo9*99 It is evident from Figure 5 that the radial height h of each drainage channel 10 uniformly increases axially from a minimum value in the middle of the roll to a maximum value in each case atthe channel end 7. Said construction applies also to the drainage channels 4 shown in Figures 1 to 3, which are formed in each case by a 90 angle section.

Figures 7 and 8 show a further modified form of construction.

Here, the expressing roll 3 is provided with a double-walled sleeve, wherein the outer sleeve 11 is perforated and supported on the closed inner sleeve 14 via paraxial webs 13, between which is formed in each case a drainage channel 12.

Here too, the drainage channels 12 rotate with their, in each case, open channel ends 7 past the perforated diffuser side walls 8 indicated in Figure 2, through which the expressed liquid taken up by the drainage channels 12 is removed.

Further welded onto the outer sleeve 11 are paraxial driver profiles 15, which are disposed in each case in the radial planes of the webs 13 forming the drainage channels 12. In said case, at least some of said driver profiles 15 may take the form of perforated drainage channels, which may in principle correspond to the form of construction according to Figure 3.

The expressing roll 3 does not have a individual rotary drive, being instead rotated about its roll longitudinal axis 16 by oo 15 the forward-moving bagasse bed 1.

o ooooo r

Claims

1. An apparatus for dewatering the bagasse bed at the end of a conveyor-like diffuser, having an expressing roll in the form of a screening roll which extends at right angles to the conveying direction over the entire width of the diffuser, presses with its dead weight from above upon the bagasse bed moving towards the diffuser end and takes up expressed liquid, characterised in that welded onto the cylindrical sleeve of the expressing roll are paraxial drainage channels which have a cross section tapering conically in a radially outward direction, are provided in their two longitudinal walls with perforations and rotate with their, in each case, open channel ends past perforated diffuser side walls, through which the liquid is taken up by the drainage °o channels and flowing back out of their channel ends is removed 15 into a liquid collecting trough.

2. Apparatus according to Claim 1, characterised in that each drainage channel has a trapezoidal cross section. 20

3. Apparatus according to Claim 2, characterised in that the two longitudinal walls starting from the roll sleeve are perforated only to approximately 2/3 of their height.

4. Apparatus according to Claim 2 or 3, characterised in that the channel base is closed.

Apparatus according to Claim 1, characterised in that each drainage channel has a triangular cross section with a rounded apex which is free of perforations. 8

6. Apparatus according to Claim 5, characterised in that each drainage channel is formed by a 90 0 angle section.

7. Apparatus for dewatering the bagasse bed at the end of a conveyor-like diffusers, having an expressing roll in the form of a screening roll which extends at right angles to the conveying direction over the entire width of the diffuser, presses with its dead weight from above upon the bagasse bed moving towards the diffuser end and takes up expressed liquid characterised in that the expressing roll is provided with a double-walled sleeve, wherein the outer sleeve is perforated and supported upon the ~closed inner sleeve via paraxial webs, between which is formed in each case a drainage channel, wherein the drainage channels rotate with their, in each case, open channel ends past is perforated diffuser side walls, through which the liquid taken up by the drainage channels and flowing back out of their channel ends is removed into a liquid collecting trough. .:o.li

8. Apparatus according to Claim 7, characterised in that paraxial S 20 driver profiles are welded on the outer sleeve. *o

9. Apparatus according to Claim 8, characterised in that the driver profiles are disposed in each case in the radial planes of the webs forming the drainage channels.

Apparatus according to Claim 9, characterised in that at least some of the driver profiles take the form of perforated drainage channels. 9

11. Apparatus according to any one of the preceding claims, characterised in that the radial height of each drainage channel uniformly increases axially from a minimum value in the middle of the roll to a maximum value in each case at the channel end.

12. Apparatus according to one of the preceding claims, characterised in that the expressing roll is rotated about its roll longitudinal axis by the forward-moving bagasse bed.

13. Apparatus according to one of the preceding claims, characterised in that the flow area of the perforations increases :from the outside in the direction of the interior of the drainage channels. o* oi DATED this twenty-ninth day of November 2001. MASCHINENBAUANSTALT AG By its Patent Attorneys FISHER ADAMS KELLY DATED this twenty-ninth day of November 2001. By its Patent Attorneys FISHER ADAMS KELLY