WO1997048486A1

WO1997048486A1 - Apparatus for producing strings of compacted granules from powder material and binder

Info

Publication number: WO1997048486A1
Application number: PCT/SE1997/000963
Authority: WO
Inventors: Wiking Pettersson
Original assignee: Wiking Pettersson
Priority date: 1996-06-14
Filing date: 1997-06-03
Publication date: 1997-12-24
Also published as: SE9602353L; SE506685C2; SE9602353D0; AU3198497A

Abstract

Apparatus for providing compacted granule strings from powder material and binder comprises a mixer (10-14) for producing a mixture of powder material and binder; and a feeder (15, 16) for feeding the mixture to a compaction arrangement (1, 2, 5; 1, 4, 5). The compaction arrangement includes an endless belt (1) which runs around two belt guide rollers (2, 3), and a clamping roll (5) which defines moulds in coaction with the outwardly facing surface of the belt (1), said moulds being at least partially surrounded by rubber-elastic material, such that the mixture present in the moulds is subjected to compaction in at least two dimensions during passage between the clamping roll (5) and the belt (1). The moulds are formed by grooves (9) in a rubber-elastic surface layer on the clamping roll (5) or on the belt (1), wherein the grooves define an angle which deviates from the belt travel direction by an angle of at most 45 degrees in the plane of the belt (1).

Description

APPARATUS FOR PRODUCING STRINGS OF COMPACTED GRANULES FROM

POWDER MATERIAL AND BINDER

The present invention relates to apparatus for producing compacted granular strings from powder material and binder, in accordance with the preamble of the following main Claim.

Powdered material, such as ashes from the combustion of tree waste, bark, twigs, wood chips, peat, etc., cannot be readily transported away from the site on which the ashes are produced. The ash must first be converted to granules, pellets or like forms in order to enable it to be handled, transported and reused without risk of generating dust, etc. It is known in practice to add a binder to the ash and to press the ash/binder mixture to a granular, pellet or like form. It has been proposed that to this end, there is used an endless rubber fabric that includes recesses which are filled with the mixture, wherein the fabric and the mixture contained in the fabric recesses are compressed between two stamps or clamping rollers, wherewith the rubber material flows into the recesses when compressed between the stamps/rollers. The mixture is thus subjected to semi- isostatic compaction which alleviates the difficulty of removing the granules from the recesses.

If desired, the produced granules are subjected to a heat- treatment process as they are transported by the belt and are finally removed from the belt with the aid of vibrators. An example of this known technique is disclosed in DE-C-2 215 577.

Known equipment of this kind, however, has a relatively low production rate, due to the fact that the ratio between the area of the recesses and the area of the fabric (in the plane of the fabric) is relatively small, and also due to the strenuous efforts that must be applied in actually releasing the granules from the belt recesses. It is important to ensure that the produced, optionally cured, granules leave the recesses before said recesses reach the position at which the mixture is delivered thereto.

Accordingly, it is an object of the present invention to provide apparatus of the aforesaid kind that has a high granule production rate and that will enable the granules to leave the recesses more effectively than with hitherto known apparatus of this kind.

This object is achieved with apparatus according to Claim 1.

Further developments of the apparatus are defined in the following Claims.

An essential feature of the invention is that the powder/binder mixture is formed into strings which are compacted semi-isostatically transversely to the longitudinal direction of the strings and that the apparatus produces the strings in a manner such that subsequent to compaction the strings lie on the circulating belt in a position of orientation in which the longitudinal axis of the strings deviates from the direction of belt travel by at most 45 degrees. The-longitudinal axes of the strings will preferably extend parallel with the direction of belt travel.

This enables the flexural rigidity of the strings/granules to be utilized in removing the string-like granules from the belt as the belt is deflected from one belt run, preferably the upper belt run, to its other belt run. Because adhesion of the string-like granules to the belt increases with increasing binder contents and because the bending strength of the strings also increase with increasing binder contents, the inventive apparatus is relatively insensitive to binder overdoses. In one preferred embodiment of the invention, the belt guide roller located at the upstream end of the upper belt run also functions as one of the clamping rollers. In another preferred embodiment, the recesses are established in the circulatory fabric.

Located at the downstream end of the upper belt run, slightly beneath the level of said run, is a deflection plate which extends across the full width of the belt with an edge lying adjacent the belt surface. The deflection plate is preferably arranged to slope obliquely downwards, away from its edge located adjacent the belt. The plate will suitably include teeth that engage in the grooves in the belt.

The inventive apparatus is particularly well-suited for producing granules from the ashes of combusted tree waste, bark, twigs, brushwood, wood chips, etc., and enables the produced granules to be readily released from the belt. Release of the granules is facilitated by the fact that the granules are formed as strings which extend in the direction of belt travel, said strings being bent loose from the belt as said belt is deflected from the belt run on which the granules are formed. It is normally necessary to add binder to the ash prior to compressing the ash into the string-like granules. Although the invention is described with reference to handling such ash and a binder herefor, it will be obvious that the invention can also be applied with other types of powdered products that shall be converted to a granule form, so as to avoid dusting problems and also to be able to extend the time period required for the powder material to constituent parts thereof to be released.

The invention will be described in more detail with reference to exemplifying embodiments thereof and also with reference to the accompanying drawing. Fig. 1 is a schematic side view of an inventive apparatus.

Fig. 2 is a schematic sectional view taken on the line B-B in Fig. 1.

Fig. 3 is a sectional view taken on the line A-A in Fig. 1 and illustrates a first embodiment of the invention during production of string-like granules.

Fig. 4 is a view corresponding to Fig. 2 and shows a granule formed in the inventive apparatus.

The apparatus shown in Fig. 1 includes an endless belt 1 which runs over two horizontal and mutually spaced belt- deflecting rollers 2, 3, of which one may be driven so as to move the belt 1 in the direction shown by the arrow 20. The upper belt run moves between two vertically spaced clamping rollers 4, 5. Two conduits 11, 13 extend from a respective ash container and binder container 10, 12 to a mixer 14, from which a feed pipe 15 conducts the mixture to a nozzle 16 that extends across the full width of the belt 1, in a position above the upper belt run, upstream of the upper clamping roller 5.

As evident -from Fig. 2, the belt 1 is provided with longitudinally extending grooves 9 in the rubber material from which the belt 1 is formed. It will be seen from Fig. 2 that the belt 1 will suitably have a band-stabilizing cord reinforcement.

The clamping rollers 4, 5 will preferably be made of a rigid material, for instance steel. The rollers 4, 5 are pressed against the belt 1 at a pressure in the order of 100-500 cm². The rubber material of the belt 1 will therewith experience an elastic reduction in thickness, wherewith the rubber material flows into the grooves 9 and reduces the width thereof, whereby the ash/binder mixture experiences semi- isostatic compaction in the grooves 9. The compacted strings 8 formed from said mixture then accompany the upper run of the belt 1 through a heating device 6 in which the strings are hardened. The strings 8 will then have an intrinsic flexural rigidity and therefore strive to continue to move in the direction of the upper belt run as the belt 1 is deflected around the guide roller 3, which defines the downstream end of the upper belt run. Adhesion between the string-like granule 8 and the belt 1 is herewith broken. A deflecting plate 7 is provided adjacent the belt-deflecting roller 3 at a level immediately beneath the upper belt run, for assisting the release of the granule string 8 from the belt 1.

Fig. 3 shows the bottom defining surface 51 of the upper clamping roller 5, the upper defining surface 41 of the lower clamping roller 4, the belt 1, and also shows in broken lines the contours of a non-loaded groove 9 and the upper surface of the belt 1. The Figure also shows the compacted string 8 in cross-section.

As will be seen from Fig. 4, the compacted string 8 has a much smaller cross-section than the groove 9 when no load acts on the belt 1.

When the powdered material is comprised of the ashes of combusted tree waste, bark, wood chips, sawdust or like material for instance, the binder may consist of green liquor sludge (tall oil pitch), lignin. The binder is thus advantageously a product that is considered a waste product in the wood/paper industry. The binder serves to reduce the inner friction of the powder material as it is compacted, and also binds the ash particles. The binder shall be added in the smallest possible amount, and will therefore be present in somewhat larger proportions than is desired, in order to ensure that a free ash is avoided.

The resultant granules can be dumped in natural surroundings, since the ash contains nutrients beneficial to forests and ground on which berries grow, the beneficial constituents of the ash being leached-out under the influence of weather and wind over a suitably long period of time.

Claims

1. Apparatus for forming compacted granule strings from powder material and binder, wherein the apparatus includes a mixer (10-14) for producing a mixture from said material and said binder, a feeder (15, 16) for feeding the mixture to a compacting arrangement (1, 2, 5; 1, 4, 5), characterized in that the compacting arrangement includes an endless belt (1) which runs around two belt guide rollers (2, 3) , and a clamping roll (5) which defines in coaction with the upwardly facing surface of the belt (1) moulds (9) that are at least partially surrounded by rubber elastic material such as to subject mixture present in the moulds to compaction in at least two dimensions during passage between the clamping roll (5) and the belt (1); in that the moulds are formed by grooves (9) in a rubber-elastic outer layer on the belt (1); and in that the longitudinal axes of the grooves define an angle which deviates from the direction of belt travel by an angle of at most 45 degrees in the plane of the belt (1) .

2. Apparatus according to Claim 1, characterized in that the grooves (9) are provided in a rubber-elastic outer layer on the clamping roll (5) .

3. Apparatus according to Claim 1 or 2, characterized in that both the walls and the bottoms of said grooves are comprised of rubber-elastic material.

4. Apparatus according to any one of Claims 1-3, characterized in that the compaction arrangement (1, 2, 5; 1, 4, 5) is located adjacent one (2) of the belt guide rollers; and in that a device (6) for hardening the granules produced by the compaction arrangement is provided at that belt run that extends from the region of the compaction arrangement.

5. Apparatus according to any one of Claims 1-4, characterized by a pick-up blade (7) located at the first belt guide roller (3) downstream of the compaction arrangement, wherein the pick-up blade (7) is located at a level beneath the outer surface of that part of the belt which carries the compacted granule strings with the pick-up edge of said plate being positioned in the close proximity of the outer surface of the belt (1) .

6. Apparatus according to Claim 5, characterized in that the pick-up blade (7) has teeth that extend into the grooves (2) .

7. Apparatus according to any one of Claims 1-6, characterized in that in addition to the clamping roll (5) the compaction arrangement also includes a counter-roll which coacts with the clamping roll (5), said belt running between the clamping roll (5) and the counter roll (4; 2) .

8. Apparatus according to Claim 7, characterized in that the counter-roll (2) is comprised of one belt guide roller (2) .