Process and apparatus of implementation of a method for purifying fibrous vegetable matters.

The present invention relates to a method and an apparatus for cleaning a fibrous plant material for use in the preparation of the pulp, to remove undesirable components without value, such as sand, stones, rocks, metal particles, chips, dirt and other pollutants. The present invention is especially suitable for use in cleaning fibers of sugar cane bagasse, but is also suitable for use in cleaning fibers of other plant materials, such as straw, flax, rice husks, bamboo, alfa, hemp and waste jute.

The prior art has suggested several methods and devices for cleaning the pulps and the wood fibers for paper-making. Representative examples of these known methods include those that are described in the patents no. 1.988.416 Americans (1935); 3.367.495 (I968) and 3.279.597 (1966). U.S. Patent no. 3.690, 358 (1972) described waste processor forced air for the cane stalks.

The present invention will now be described by re against of the accompanying drawings, on which:

Figure 1 is a plan view representing an arrangement generally possible of the device according to the present invention.

Figure 2 is a view in front elevation of the apparatus shown in fig. 1.

Figure 3 is a view in end elevation, taken from the right side of Figure 1.

Figure 4 is an elevation view, with partial cut, taken along the line 4 - 4 of Figure 1.

Figure 5 is an elevation view, with partial cut along line 5 - 5 engagement of Figure 1.

Referring to Figures, see that the cleaning device represented, designated as a whole by 10, has a washing tank, or trough, 11, U-shaped, having an outer wall 12, an inner wall 13, a bottom wall 14 and a communication open top. The inner wall 13 has openings 13&and 13b (as shown in Figures 4 and 5) to the outlet end 16 and to the inlet end 15, respectively, of the device, to allow recirculation of the cleaning fluid. The device may be arranged in line, in which case special features will be needed for recirculation. The arrangement U-shaped represented gives a more compact unit and recirculation simplified. At the end of the legs of the vessel 11 is an inlet chute 15 for supplying fibrous material to clean the roller 21; and at the end of the other leg, there is an exit chute 16 for the cleaned fibers. Transversely across the vessel, there is a set of feeding rollers. In the device shown, there are eight of these rollers, designated 21, 22, 23, 24, 25, 26, 27 and 28.

The feeding rollers 21, 22 and 23 include plural arcuate fingers of uniform length, secured on their outer circumference, such that the fingers 20 represented on the roller 22. The rollers 24 and 25 have fingers bent like, except that the fingers on said rollers are d ^ varying lengths. All fingers 20 on the rollers 20 to 25 are curved in the direction opposite to the direction of rotation of the rollers (see for example fig. 4). When the rollers 21 to 25 rotate, the fingers cause the fibrous material fed into the inlet chute 15 to be positively displaced from the inlet end towards the outlet end of the vessel. At the same time, the fingers cause the fibrous material to be dipped or immersed repeatedly in the cleaning fluid held in the vessel. As a result of these dips and re-immercions repeated in the cleaning fluid, foreign materials such as sand, dirt, stones and chips (nodes) are separated from the bulk of the fibrous material.

Due to their higher density, they begin to settle in the cleaning fluid.

In the curved portion of the washing tub U-shaped, the fingers or prongs are arranged in a tapered configuration on the rollers 24 and 25. This configuration, on the roller 25 on the outlet side of the curved portion, to a base diameter wider than the configuration of the roller 24. The diameter to supply configuration smaller roller 24 near the central portion of the vessel (the medium) reduces the linear speed of the fibers so that they may move properly around the bend in the U-shaped trough the roller 25 supply configuration has a larger diameter in the middle to accelerate the fibers after they have passed the curve.

As can be seen best in Figures 2 and 3, the bottom of the washing tub has a section 17 in cone reversed slope which is also located in the curve of the generally U-shaped at the top of this conical section, there is a device 18 discharge waste. The device includes a cylindrical chamber 30 and upper and lower valve 31, 32. The upper valve 31 is normally open, for collecting foreign materials deposited in the chamber 30. Periodically, the valve is closed and the lower valve 32 is open, discharging the collected waste.

Then, the lower valve is closed again, the chamber 30 is filled with water from a separate source 52 (fig. 3), and finally the upper valve is re-opened and foreign materials that settles in the section 17 to be noticed Supper collected in the chamber 30. The chamber 30 may also be provided with a vent tube 53, as shown in Figure 3. The operation of the dumping of waste can be easily automated, if desired, and erosion for periodically without foreign materials collected without interrupting the operation of the vessel 11 for cleaning.

If desired, or when it is required to clean and effective separation of the fibrous material of associated with foreign materials, the device may comprise means for introducing air bubbles so as to aid the reflottage fibrous material cleaned to the top of the mass of the cleaning fluid. Such means may include for example an air line 50 and a diffuser 51, as shown in Figure 2, located in the inverted conical section 17 of the vessel 11 just above the discharge device 18.

The fibrous materials cleaned are now forced continue their movement toward the outlet end of the vessel 11, by the rollers β 2, 27, 28. These rollers have a plurality of curved fingers (e.g. the fingers 19 on the roller 26) as those rollers 21 to 23, of uniform length and are bent against the direction of rotation. On the rollers 27 and 2 β, smooth metal plates are attached to the ends 19a, transversely, respective rows of fingers 19 and serve as vanes to advance positively the cleaned fibers towards the discharge chute. On the roller 28, the plates 19a are further provided with flaps that extend rubber 19b slightly beyond finger-tip 19 for a function as a scraping or the like.

As may best see on Figure 2, the rollers 26, 27, 28 in the jamb of the vessel outlet U-shaped are positioned for axial rotation in a plane above that of the rollers 21, 22, 23, 24 of the inlet leg. As shown in fig. 5 * this has the effect that the fibrous materials cleaned forced onto the slope 35 at the end of which, the fibrous mat may drip through the plate and may be compressed if desired to reduce the level of cleaning liquid (usually water) at desired level. After passing the roller 28, the fibrous material cleaned descends by sliding along the inclined discharge chute 16 on for further processing. The drained water back into the vat and recirculates to the inlet side of the vessel through the openings 13^has and 13b.

The apparatus includes an energy source suitable, as a motor 40, for driving the individual rollers 21 to 28, by for example to a writer to gear 41 and drive chains (such as the chain 42) cooperating with chain wheels at one end of each roller (e.g. the pinion 43 on the roller 24). The particular means chosen to drive the rollers is not critical and the transmission shown is to be considered as one example among many possible means.

The entire device is suitably supported in frame means such that the beam 44 and the spacers 45, with the axial drive shafts of each roller 21 has 28 suitably journaled in bearings on the beams to sole of conventional construction.

In operation, the fibrous material to be cleaned, such as sugar cane bagasse peeled, dry or moist (see e.g. U.S. Patent N.^I 3.537.142 of 3 November 1970) is introduced through the chute 15 into the vessel 11, which has previously been filled to a suitable level with water or other desired liquid medium in which the fibrous material will tend to float. For obvious reasons, water is the preferred liquid medium. The fluid level is usually held automatically by the use of an automatic valve and a suitable overflow. It has been found that the coated better performance is usually made when the level of water in the apparatus represented is maintained at about 15 cm below the line

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axial centers of the rollers 21 to 25.

The fibrous mat so introduced into the vessel is moved by the rollers 21 to 25 over the entire U-shaped path of the vessel, and during this movement is dipped repeatedly under water by the fingers carried by the rollers. As a result of this repeated dipping that any extraneous material densely present in the fibrous material entering the bowl sink toward the bottom of the vessel, and optionally will be brought up to the section 17 of the conical bottom steep (minimal 350) in the curve of the Û and Y descend by sliding. This foreign material is collected in the chamber 30 it is discharged periodically as described above, without disturbing or interrupting the washing tub. On the other hand, the fibrous material into washing has a natural tendency to reflotter to the liquid surface in the tank, which can be promoted phenomenon, if desired or if necessary, by the introduction of small air bubbles in the liquid.

The moving speed of the mat along the inlet leg of the U-shaped trough and the length of the inlet leg is chosen appropriately to enable separation of the fibers and foreign materials associated therewith. If the fibrous material dirty is transported too quickly, the foreign material will not file properly, while the conveyance speed is too slow, there is a tendency for some of the most dense fibrous materials to be deposited along with the waste. A few routine experiments, are sufficient to an operator clever to determine speed appropriate to the intended application.

Before being discharged from the vessel, the fibrous material cleaned is forcibly pushed, by the inclined plane 35, on the perforated plate 35a through which excess water or other washing liquid medium may drain into the tank. A correct interpretation of the inclined plane of the perforated plate 35# 35^has " cooperating rollers 26 and 28 to yield the desired liquid content in the fibers discharged from the chute l6. If so required, pressure rollers may be provided at the discharge end of the tank, to assist the extraction of the liquid out of the fibrous material. If desired, there may be a section 35s with valve circuiting or "bypass in" (fig. 5) in the plate 35, operated for example by a piston mechanism 35p (fig. 5) when it is desirable or necessary to recirculate the fibrous material if there is a jam at the outlet end of the tank, or if it can be observed that the product then still employs a washing treatment.

A device of the type shown is tried for cleaning fragments dry bagasse peeled, prepared by the use of the apparatus and method described in U.S. Patent no. 3.537.142 before a secondary wet peel according to the method shown schematically in Figure 2 3.688.342 n-® American related Patent ; it is to say that the material supplied to the washing tub is the fibrous fraction dry peeled raw bagasse, and the cleaned fibers are discharged from the tank 11 directly to the secondary wet peeling apparatus. The overall dimensions of the vessel were about 6.7 m long on 3 m wide with an internal width of the leg portions of the U-shaped vessel of about 1.2 meters. Inverted frustoconical section 17 had a base diameter of about 2.7 meters, a wall inclined at an angle of 35 degrees toward an output of 30 cm at the top of the truncated c8ne. Soaking the rollers 21, 22, 23, 24 and 25 were provided with fingers or prongs 20 slightly bent so that they do not catch the fibers on emerging from water. On the rollers 21 to 23, the fingers had approximately 45 cm in length, mounted on rollers of about 30 cm diameter. There were six rows of pins around the circumference of the rollers, with the pins spaced about 25 cm in the row and staggered relative to the pins of the adjacent row. The rollers driven at about 18 rpm, giving an average linear speed of about 12 m per minute fibers conveyed through the vessel. The fibers were fed to the vessel at a rate of approximately 5.8 tons per hour and were a floating mattress about 30 cm of thickness to the surface of the water in the tank. This feed rate, related to the average linear velocity above rollers to fatigue and an average residence time of about one minute between the inlet chute 15 and the output chute 16, divided approximately equally between the inlet leg and the jamb of the vessel outlet U-shaped.

The rollers 2 β, 27, 28 were equal with 30 cm in diameter, and also similar to the rollers 21, 22, 23 except that they had smooth metal plates welded to the arcuate fingers 19a 19 on the rollers 26 to 28, and extending over the entire width of the roller. The additional flaps of rubber 19b attached to metal plates 19a on the roller 28 rubbed against the perforated plate 35^has the holes and kept clean.

There were six plates of metal on the rollers 26 and 27 and twelve metal plates with associated rubber flaps on the roller 28.

This test has given excellent results. There was an almost complete removal of all waste, including rocks, gravel, coarse sand, metals, rubber, plastics, bark burned and packets dense fiber, poor quality, such as seamed from cane. A portion of the coated fine sand in the fibers is not deposited in the vessel, the detachment of the sand in the tank helps to its complete removal from bagasse fibers in the next stage the wet peel. It showed more complete removal of the sugar and other soluble bodies in the fiber, than was previously possible with peeling wet only. The soaking improved bagasse into the washing tub and the fiber skin resulted in a more detachable wet in the coat. The soaking also increases the flexibility of the strands and thus leads to less breakage of fibers and/or loss through wet peeling apparatus. Thus, the fiber bundles were more readily opened, so that during pulping fibers after the last wet peel, the cooking liquor penetrate through the packets more easily than was previously possible. This made it more uniform cooking, chemical requirements weaker and less buttons.

The present invention is not limited to the exemplary embodiments just described, it is rather likely variations and modifications apparent to those skilled in the relevant arts.