MXPA97001125A - Method for extraction of juice from cane of azu - Google Patents

Abstract

A continuous countercurrent process is provided for extracting juice from a bed of fibrous material such as cane sugar, the process comprising a plurality of stages, preferably 3, with each step including air separation, the displacement of juice by a process of flow stopper, real, and discharge of displaced juice and means of displacement

Description

METHOD FOR EXTRACTION OF JUICE FROM DB SUGAR CANE FIELD OF THE INVENTION This invention relates to a method for extracting juice from sugarcane, for use in the manufacture of sugar. BACKGROUND OF THE INVENTION In cane, the juice rich in sugar that is required to be extracted, is stored in storage cells that are broken ^ easily. The methods of cane preparation such as by l > shredded, they are able to open up to 94% of these cells containing juice, resulting in a mixture of juice rich in sugar and fibers that contains a large percentage of material of low purity that is not easily damaged in the decomposition of storage cells . 15 Traditionally, methods for juice extraction such as extraction, dry compression, leachate and diffusion have been unable to take advantage of the structure of the prepared cane, and despite the technical progress are still characterized by low efficiency. 0 Theoretically, the isolation of juice from the fibers can be achieved by physically displacing the juice with water. This was recognized as early as 1889 by Matthey who obtained United Kingdom Patent No. 21021 for its simple process.

According to a literature, displacement is best achieved by a countercurrent flow of water and juice-fibers, where the water advances as a front (plug flow) that operates similar to pistons pushing through the broken cells and replacing the juice. To achieve an efficient plug flow displacement system, there should be no breaks or interruptions in the fiber and juice bed, as this would direct the water to derive the material. In addition, the mixing in the system reduces the countercurrent flow and consequently the ejection of juice by pressing and compressing is undesirable. Consequently, the ideal system constitutes an undisturbed bed of fibers and juice and a flow of juice and water type stopper. This ideal situation is difficult to achieve on a commercial scale but can be approximated by keeping the undisturbed bed in a horizontal position and breaking the liquid displacement of the plug flow in stages. The Silver ring diffuser operates according to this principle, but involves an 18-stage process where water is added from above a continuous bed, circulates through the moving bed and dropped into a juice compartment below. The reason for the length of the process is that it is carried out mixing avoiding ideal plug flow shift.

Another factor that is considered to impede efficiency is the presence of a large volume of air in the bed. Separation of air in batch diffusion in the beet sugar industry was considered essential. A process known as meichage was used commercially in 1930 in the Naudet process of batch distribution of bagasse. This involves the removal of air by the addition of water from below, the water advance front transports the air to the upper part of the bed from where it is released. This, however, has only been possible in a batch process. The construction of an efficient plant should be based on a consideration of the structure and volumetric composition of the raw material, which in the prepared cane is characterized by a low volumetric density and a high volume of voids (ie it is filled with air). In order to achieve an efficient extraction process, bed compaction should be avoided to avoid low percolation rates as well as juice ejection.

Additional hollows in the cane bed should be filled to facilitate a mixture of free flow of cane and juice. Therefore, it is an object of this invention to provide a method and apparatus for the continuous extraction of juice from sugarcane, which takes advantage of the prepared cane structure, resulting in dramatically improved extraction efficiency.

THE INVENTION According to the invention, a process for extracting juice from a bed of fibrous material, comprising a countercurrent, continuous process, in a plurality of stages, each step includes the step of separating air, displacing the juice by a real plug flow process, and discharging the displacement medium and displaced juice. In the preferred form of the invention, the fibrous material prepared is sugar cane and the process comprises three stages, the means of displacement for stage 1 of stage 2, is the juice discharged from stage 2 and stage 3 respectively, while water constitutes the means of displacement for stage 3. Separation of air is achieved by meichage as described above. The three-stage displacement process of the invention is preferably carried out on a conventional horizontal drag-type conveyor, the conveyor speed is adjusted according to the flow of cane, such that a depth of the bed in the range from 0.3 to 0.5 meters is maintained. This facilitates the maintenance of a high rate of percolation which, with the help of an increased hydrostatic head, is typically 0.1 meter per second. This is a significant improvement of 0.1 meter per minute typically obtained in prior art processes.

In order to exhibit efficient extraction, the juice content of the bagasse must be in the order of 20 times the fiber content of the cane (ie the fiber content of the bagasse must be less than 5%). Under these conditions, (cane and juice fibers) behave like a liquid. This ensures that no mechanical handling of the bagasse is required during meichage and displacement. MPDA IPAPfiS PS LA INVENCIÓ Modalities of the invention are described below with reference to the accompanying drawings in which: Figure 1 is a side view of a drag-type conveyor that operates according to the process of the invention; Figure 2 is a similar view of an alternate type of equipment; and Figure 3 is an end view of the perforated drum (5) of Figure 2. In Figure 1, the shredder 10 provides the shredded shank to the conveyor. The conveyor moves at a set speed according to the cane flow such that a layer of approximate depth 0.3 moves on the perforated bottom 11 of the conveyor.

Meichage juice is pumped from tank 18 by a variable speed pump 13 at controlled expense and pressure.

The expenses maintained are sufficient to ensure that the level of juice just above the surface of the layer of the cane that leaves the meichage part (A) of the conveyor. In the displacement section (B), the displacement cube is fed from the upper channel 15 in a rain trough pattern. This avoids mixing and improves the displacement efficiency and is achieved by supplying the juice on the upper platform of the conveyor. The level of the juice is maintained by automatic valves 16 in the discharge pipes 17. The juice of the displacement (B) and discharge (C) sections is discharged through the pipe 17 to the tank 18. It should be noted that in order to ensure enough hydrostatic head for the process of flow displacement stopper and for quick discharge of the bagasse left by each stage, the level of juice in the receiving tank 18 in each stage must be at least two meters and preferably between three and four meters lower than the level of juice in the conveyor (upper part of the cane bed). This process is repeated in stages 2 and 3, the only variations are in the sugar content of the displacement and bagasse juices. The displacement juice for stage 2 is the discharge (displaced) juice from stage 3, while in stage 3, the displacement juice is in fact water from the dehydrating mill. The molasses (fiber and cane juice) is discharged from the conveyor through the channel 19 to the pre-extractor 20, which is an inclined three-roll mill, designed to remove half the juice content of the molasses. The bagasse emerging from the pre-extractor is transported by a closed channel 22 (Meinecke channel) to the base of the conventional bagasse elevator 23 that feeds the channel (Donelly) of the final dehydrating mill 24. This mill is a conventional four-roll mill . Turning now to Figure 2, a cross flow displacement system is illustrated, which is useful for plants with high load capacities. In this system, a portion of the meichage juice is added from the upper tank 5 and incorporated into the solid feed (shredded cane) while thickened by the steel l. The resulting sludge is thrown down from the curved plate 2 into the open channel 4. At this point, a second portion of the meichage juice is added, this time from below the perforated bottom 3 of the open channel 4. The sludge then circulates low the influence of gravity on the displacement section B.

The displacement section comprises a bent perforated bottom through which the displaced juice circulates. To avoid clogging, the bottom is scraped by the perforated drum which also helps in moving the molasses once it becomes more solid in the discharge section. For this purpose, the drum is coupled with tines 6 which are joined by welding to the drum in twelve generation lines. The scraping action is facilitated by the scraper plates 7 joined by welding to the tips of each row of tines. The displacement juice is admitted into the perforated drum on the displacement section. For this purpose, the perforated drum is open at each end. A thick steel disc is joined by welding inside the drilled drum, halfway between the ends. This disc is joined by welding to a cube, coined to the arrow. The drum is driven by a hydraulic or electric variable speed motor at a speed of one to two RPM. The displacement juice can be admitted into the perforated drum (in a distribution box 8 from each end) (Figure 3), through the flanges from an outer box in which the juice level can be controlled in such a way that it is not admits air In this way, the displacement juice, evenly distributed over the molasses in the displacement section, can circulate through and collect in the double bottom, from which it is discharged to the lower receiving tank. The displaced fluid flow is controlled by an automatic valve in the discharge pipe verified by the level in the juice box 9. In the discharge section C, air is admitted in the upper part of the bed molasses, allowing the remaining juice is extracted by the hydrostatic head between the upper part of the cane bed and the juice level in the lower receiving tank, by the pipe 10. The discharged molasses is then discharged by gravity action, aided by the tines Drum perforated by a 60 ° slope. To supplement the flow properties of the molasses to the next stage of the extraction, the meichage juice of that stage is admitted in the distribution box 11 in the drum through the flanges located on both sides. The molasses is then subjected to the same process twice more in the same sequence. The importance of the hydrostatic head should be emphasized. In commercial diffusers, the juice of the perforated bottom is discharged in open tanks, in such a way that the hydrostatic head can not be more than the thickness of the cane bed (one or two meters). In fact it is much less due to the presence of air in the bed.

In the present process, the juice is collected in a closed bottom. Whenever the pipe discharges the juice in the lower receiving tank, it is kept full (by the control valve), the hydrostatic head can be increased to two or four meters (or more) since it is equal to the difference in level between the juice in the cane bed and the juice in the reception tank. The discharge pipe acts as a barometric branch, removing the juice with the same impulse force as if the level of juice on the surface of the cane bed was two or four meters high.

Claims (10)

1. CLAIMS 1.- Procedure for extracting juice from a bed of fibrous material, characterized in that it comprises a continuous countercurrent process of a plurality of stages, each stage includes the steps of: a) air separation, b) displacement of the juice through a process of plug flow, real, and c) discharge of displaced juice and means of displacement.
2. 2. Method according to claim 1, characterized in that the fibrous material prepared is sugar cane and the process comprises three stages, the displacement medium for stage 1 and stage 2 which is the juice discharged from stage 2 and stage 3 respectively, while water is the means of displacement for stage 3.
3. 3. Method according to claim 2, characterized in that the separation is carried out by meichage.
4. 4. Method according to claim 2 or 3, characterized in that it is carried out in a conveyor of conventional horizontal type, the speed of the conveyor is adjusted according to the flow of cane, in such a way that a bed is maintained of depth in the range of 0.3 to 0.5 meter.
5. 5. - Method according to any of the preceding claims, characterized in that the juice content of the molasses is in the order of 20 times the. fiber content of the cane.
6. 6. Apparatus for extracting juice from fibrous material according to any of the preceding claims, characterized in that it includes a plurality of stages, each stage includes means to remove air from the material, means to move the juice through a process of flow stopper real and means to discharge the displaced juice and means of displacement.
7. 7. - Apparatus according to claim 6, characterized in that it includes three stages, the first two stages receive the juice discharged from stage 3 as a means of displacement and a source of water as the means of displacement for stage 3.
8. 8. - Apparatus according to the claims 6 or 7, characterized in that it includes a conventional horizontal drag-type conveyor, its speed is adjusted according to the flow of cane so that a bed of thickness in the order of 0.3 to 0.5 meter is maintained.
9. 9. Apparatus according to claim 6 or 7, characterized in that the molasses flows by gravity in the section of meichage and displacement, and mechanical means are provided to drag the dry molasses in the discharge section.
10. 10. Apparatus according to any of claims 6 or 9, characterized in that valves are provided in the discharge pipes to maintain a hydrostatic head of at least two meters in each stage.