Apparatus for processing compacted biomass

Abstract: The apparatus for processing compacted biomass comprises a conveying system (1) forwarding compacted biomass in a controlled manner in a mainly horizontal direction, a first (2) and second (3) rotatable roller positioned downstream of the conveying system (1) with their axes of rotation generally horizontal and parallel, the first roller (2) being positioned horizontally closer to the conveying system (1) than the second roller (3), said first (2) and second (3) roller being rotated in opposite directions with different peripheral speeds and the rollers (2, 3) being provided with teeth-like elements (7, 9) projecting from the outer surfaces to engage the compacted biomass material and passing it through a gap (8) formed between the two rollers (2, 3). The peripheral speed of the second roller (3) is higher than the peripheral speed of the first roller (2), whereby the material to be processed is fed into the gap (8) in a controlled manner and subjected to a stretching and loosening action in the gap with low energy consumption and high reliability.

Description: TECHNICAL FIELD The present invention relates to an apparatus for processing compacted biomass, such as bales of hay, straw or other similar material, into a form which is suitable to be used to fire a furnace. The material may be fed to the furnace from a chute positioned downstream of the processing apparatus by means of a stoker-type feeding mechanism. The compacted biomass is forwarded in the processing apparatus in a controlled manner by a mainly horizontal conveying system and are opened by cutting the strings or other holding means keeping the bales in a compacted state. BACKGROUND ART From AU-663,791, on which the preamble of claim 1 is based, it is known to provide an apparatus for processing bales of hay and straw. This apparatus comprises a conveying system of rollers forwarding the bales towards a shredding roller rotated in the same direction but with a relatively high speed compared to the speed of the conveying rollers, and positioned downstream of the conveying rollers. A further roller is positioned downstream of the shredding roller to feed material into the gap between this further roller and the shredding roller, the further roller being rotated in opposite direction compared to the shredding roller, with a lower peripheral speed. The relatively high speed of the shredding roller has a tendency to throw material over and past the further roller in an uncontrolled manner, and the shredding roller has, due to the higher peripheral speed, a tendency to grip more material from the bale than can be transported down between the counter-rotating rollers. DISCLOSURE OF THE INVENTION Based on this prior art, it is the object of the present invention to provide an apparatus of this kind which is able to process compacted biomass in an efficient way, reducing the required energy for the processing and yet delivering a processed material sufficiently loosened e.g. to be fed into a furnace by means of a stoker-type feeding system with a screw conveyor or a reciprocating piston. This is achieved by an apparatus in accordance with claim 1. The two rollers provide a positive feeding of the material through the gap between the rollers, the first roller controls the speed of feeding into the gap and the faster rotating second roller secures that all material fed into the gap is quickly removed. The different peripheral speed of the two rollers provides a stretching and thereby loosening of the material with a low energy consumption and with a high reliability. Preferred embodiments are revealed in the subordinate claims. BRIEF DESCRIPTION OF THE DRAWING In the following detailed part of the description, the invention will be explained with reference-to an exemplary preferred embodiment thereof shown in the drawings, in which: Figure 1 shows a schematic side view of the essential parts of an apparatus in accordance with the invention. DESCRIPTION OF THE PREFERRED EMBODIMENT The apparatus shown in Figure 1 comprises a conveying system 1 forwarding the bales of compacted biomass in a controlled manner towards the first 2 and second 3 rotatable roller positioned downstream of the conveying system 1. Below the two rollers 2, 3 is a chute 4 for receiving the processed material, said chute being provided with a screw conveyor 5 positioned at the bottom of the chute to feed the processed biomass material into a furnace (not shown). In the shown embodiment, the chute is provided with a sliding gate 6 providing a possibility of closing off the connection between the furnace and the processing apparatus in order to prevent a fire from propagating into the processing system from the furnace. The apparatus shown in Figure 1 functions in the following way: Compacted biomass, e.g. bales of hay or straw, is fed into the apparatus and forwarded in a controlled manner in a horizontal direction by the conveying system 1. The strings or similar holding means keeping the bales in a compacted state are cut up in the conveying system 1, whereby the bales are opened. At the front end of a bale forwarded on the conveying system 1, the first roller 2 engages the bottom part of the bale with its teeth 7 and feeds the gripped material into the gap 8 between the two rollers 2, 3. In the gap 8 between the two rollers 2, 3, the material is engaged by the teeth-like elements 9 on the second roller 3 and due to the higher peripheral speed of the second roller 3 the material is stretched and loosened in the gap 8 between the two rollers 2, 3. When leaving the gap 8, the material is dropped into the chute 4 and falls down to the screw conveyor 5 feeding the furnace. In the embodiment shown in Figure 1, the first roller 2 has a smaller diameter than the second roller 3 and accordingly, the different peripheral speed of the two rollers can be provided by rotating the two rollers 2, 3 with the same rotational speed, i.e. same number of revolutions per minute. In Figure 1, the first roller 2 is shown positioned with its teeth-like elements 7 protruding upwardly above the bale supporting surface of the conveying system 1 so that the teeth-like elements 7 can grip the bottom part of the bale material. In this respect the surface supporting the bale material in the conveying system 1 may be provided with slits for the teeth-like elements 7 in order to support the bale material at the point where the teeth-like elements 7 grip the material. The teeth-like elements 7, 9 on the two rollers 2, 3 are positioned in a staggered manner in the axial direction of the two rollers in order to be able to pass through the gap 8 between the two rollers without interference between the teeth-like elements 7, 9. It may be advantageous to be able to adjust the relative vertical position of the roller 2 and the supporting surface of the conveying system 1, in order to control the gripping of the bale material by the teeth-like elements 7 on the roller 2. Furthermore, the distance between the two rollers 2, 3 may advantageously be adjustable, in order to control the processing of the material in the gap 8 between the two rollers 2, 3. Furthermore, the two rollers 2, 3 may be supported in their positions in such a way that if a stone or similar material is contained in the bale material, the rollers may move away from each other against the force of a spring or similar element, in order to allow passage of such material through the gap 8 between the two rollers 2, 3. With the position of the two rollers shown in Figure 1, material of the bales which has not been gripped by the first roller 2 and passed to the gap 8 between the two rollers 2, 3 will eventually reach the teeth-like elements 9 on the second roller 3 and be gripped by these and thereby forced into the gap 8 between the two rollers. One axial row of the teeth-like elements 7 on the first roller 2 may project further from the surface of the roller than the rest of the teeth-like elements 7, whereby said roller may be positioned in such a way that only those further projecting teeth-like elements will actually grip material from the bale of compacted biomass forwarded on the conveying system 1, the smaller teeth-like elements 7 not projecting above the supporting surface of said conveying system 1. In this way, the first roller 2 could in connection with square bales of hay or straw grip one bale stroke of hay or straw for each revolution of the roller 2, the bale stroke being forwarded through the gap 8 in a controlled manner by the smaller teeth-like elements 7 on the roller 2. The main processing of the material is performed by the teeth-like elements 9 on the second roller 3 rotating at a higher peripheral speed than the teeth-like elements 7 on the first roller 2, using the teeth-like elements 7 on the first roller 2 as a moving retainer moving at a slower speed than the teeth-like elements 9 on the surface of the second roller 3. The processing of the material will naturally cause wear on the teeth-like elemets 7, 9 and the wear parts on these teeth-like elements 7, 9 may be replaceable, shown for the teeth-like elements 9 by the front part being a separate part of these teeth-like elements which are screwed onto a fixed backpart. LIST OF REFERENCE NUMERALS 1 conveying system 2 first roller 3 second roller 4 chute 5 screw conveyor 6 sliding damper 7 teeth-like elements 8 gap 9 teeth-like elements

Claims: Apparatus for processing compacted biomass, said apparatus comprising a conveying system (1) forwarding compacted biomass in a controlled manner in a mainly horizontal direction, a first (2) and second (3) rotatable roller positioned downstream of the conveying system (1) with their axes of rotation generally horizontal and parallel, the first roller (2) being positioned horizontally closer to the conveying system (1) than the second roller (3), said first (2) and second (3) roller being rotated in opposite directions with different peripheral speeds and the rollers (2, 3) being provided with teeth-like elements (7, 9) projecting from the outer surfaces to engage the compacted biomass material and passing it through a gap (8) formed between the two rollers (2, 3), characterized by the peripheral speed of the second roller (3) being higher than the peripheral speed of the first roller (2). Apparatus in accordance with claim 1, characterized by the first roller (2) being positioned to engage the front end of the compacted biomass forwarded on the conveying system (1) at the bottom part of said compacted biomass, thereby gripping material from the compacted biomass and feeding the gripped material into the gap (8) between the two rollers (2,3). Apparatus in accordance with claim 2, characterized by the mutual vertical position of the first roller (2) and the mainly horizontal upper supporting surface of the conveying system (1) being adjustable. Apparatus in accordance with claim 2 or 3, characterized by the first roller (2) comprising at least one axial row of teeth-like elements (7) projecting further from the surface of said roller (2) than the rest of the teeth-like elements (7) on said roller (2). Apparatus in accordance with any of the preceding claims, characterized by the second roller (3) being positioned with its axis of rotation at a higher level than the axis of rotation of the first roller (2). Apparatus in accordance with any of the preceding claims, character ized by the diameter of the second roller (3) being larger than the diameter of the first roller (2). Apparatus in accordance with any of the preceding claims, characterized by the gap (8) between the two rollers (2,3) being adjustable. Apparatus in accordance with claim 7, characterized by the gap (8) being adjustable down to a minimum distance, at which the teeth-like elements (7,9) of one of the rollers (2,3) are almost in contact with the surface of the opposite roller, the teeth-like elements (7,9) of the two rollers being positioned in a staggered relation to avoid mutual interference. Apparatus in accordance with any of the preceding claims, characterized by at least one of the two rollers (2,3) being movable away from the other roller against the force of a spring or a similar element, in order to allow passage of stones or similar material contained in the compacted biomass. Apparatus in accordance with any of the preceding claims, characterized by at least some of the teeth-like elements (7,9) comprising replaceable wear parts. Apparatus in accordance with any of the preceding claims, characterized by the front face of the teeth-like elements (7) on the first roller (2) forming an angle greater than 90° with the surface of said roller (2). Apparatus in accordance with any of the preceding claims, characterized by the front face of the teeth-like elements (9) on the second roller (3) forming an angle smaller than 120°, preferably smaller than 90° with the surface of said roller (3).

Inventors: PIPER JOHN E, PIPER, JOHN E.
Applicants: BABCOCK & WILCOX VOLUND APS
Application year: 1999
Main classification: A01F29
IPC codes: A01F29