WO2002026404A1

WO2002026404A1 - Apparatus for sorting wood chips in separate fractions

Info

Publication number: WO2002026404A1
Application number: PCT/FI2001/000811
Authority: WO
Inventors: Pekka Kokko
Original assignee: Andritz Oy
Current assignee: Andritz Oy
Priority date: 2000-09-20
Filing date: 2001-09-19
Publication date: 2002-04-04
Anticipated expiration: 2003-03-20
Also published as: FI20002076A0; AU2001289966A1; FI108922B

Abstract

The invention relates to an apparatus for sorting wood chips (1), involving chips (11, 12) in a variety of sizes and similar, substantially hexahedral pieces having a length and a width, as well as a thickness substantially less than the latter, and possibly fines particles (13), by means of an impulse action. such that the excess thickness chips (11) or the fines particles (13), or both the excess thickness chips (11) and the fines particles (13) are separated from the wood chips (1) to form a separate fraction, the miscellaneous chips (11, 12) and the fines particles (13) being adapted to be sorted from each other by means of one or more separating walls (5, 5') arranged to comply with various trajectories established by means of the impulse action, said apparatus comprising a feeder (6, 6') for supplying the wood chips (1) onto a sloping support surface (2) and for sliding the same along said support surface (2) over a slit (3) extending thereacross, said slit being adapted to provide an impulse action therethrough by means of a continuous gas flow (4) on the chips (11, 12) or the fines particles (13) presently in line with the slit (3). The apparatus comprises a power-operated component (6', 9) conveying the wood chips (1) sorted out by means of the apparatus, and a guide surface (30, 31, 32) arranged in line therewith, which are dimensioned such that the wood chips (1) are diverted by the action of gravity partially or totally past said component (6', 9) by way of a sliding surface (33) established by the wood chips accumulated on top of the component in the event of malfunction, and by way of said guide surface (30, 31, 32).

Description

Apparatus for sorting wood chips in separate fractions

The invention relates to an apparatus for sorting wood chips, involving chips in a variety of sizes and similar, substantially hexahedral pieces having a length and a width, as well as a thickness substantially less than the latter, and possibly fines particles, by means of an impulse action, such that the excess thickness chips or the fines particles, or both the excess thickness chips and the fines particles are separated from the wood chips to form a separate fraction, the miscellaneous chips and the fines particles being adapted to be sorted from each other by means of one or more separating walls arranged to comply with various trajectories established by means of the impulse action, said apparatus comprising a feeder for supplying the wood chips onto a sloping support surface and for sliding the same along said support surface over a slit extending thereacross, said slit being adapted to provide an impulse action therethrough by means of a continuous gas flow on the chips or the fines particles presently in line with the slit.

An apparatus of the above type is known from the Applicant's Finnish utility model No. 3899. Such an apparatus is intended for the separation of various fractions from a major mass flow of wood chips (volume in hundreds of bulk cubic meters an hour), as determined by chip thickness. At the same time, it also enables the separation of higher density stuff, such as scrap, as well as irregularly shaped harmful particles, the same way as fines particles. This type of separation is needed in pulp production for processing feed stock.

In this type of apparatus, a plane defined by the width and length of a chip is subjected to a dynamic gas pressure (in practice atmospheric pressure) for a given short period for creating a constant effect per unit area. This results in an impulse action, which brings about a deviation of velocity for the chip as fol- lows: force = pressure x area or F = pA, impulse = force x application time or I = Ft, and deviation of velocity = impulse/mass or dv = l/m => dv = pAt/m. Since the mass of a chip is dependent on its volume, which is dependent on thickness and area and, on the other hand, the impulse is dependent on area, the entity will be independent of the width and length of a chip, whereby the devia- tion of velocity is dependent on a thickness dimension as the material density is constant, such that the ratio of deviations in velocity is inversely proportional to the ratio of thicknesses. With this deviation of velocity, the chips are caused to travel in the direction of a thickness dimension over varying distances, while travelling in longitudinal or lateral direction at the same velocity over the same distance.

The application of an impulse action on a desired chip surface requires that the chips be directed to have said surface facing perpendicularly the application direction of a dynamic pressure. The establishment of a given application time requires that the chips travel at the same speed across the pressure application site of a given size.

The chips slide along a sloping plane over a given distance for a time sufficient to set themselves in a proper position and to attain a given velocity. At this speed, the chips slide across a narrow slit, the air flowing therefrom applying its dynamic pressure to provide an impulse action. The chips fly freely in the airspace, thus having a common speed component downwards and, in accordance with the above calculation, a thickness-specific speed in horizontal direction, whereby the chips of varying thicknesses fly to various distances from the site of impulse action: thinner chips fly farther away.

High-density scrap particles (e.g. steel has a density which is about tenfold in comparison to solid density of wood) adopt a very slight deviation of velocity, and the same applies to irregularly shaped particles, due to aerodynamic properties. This way, such particles can be separated from a flow of chips in a single process. Respectively, fine dust particles adopt a major deviation of velocity, due to a thickness dimension being very small. Consequently, dust separates effectively to form a separate flow.

Various fractions are collected from the separated flow of chips by setting up separating walls in appropriate places. The separating walls can be adjustable for varying the content of chips in the fractions, as necessary. This also en- ables the implementation of a resorting process for a desired fraction by the same method.

In comparison to other equipment known from the prior art, this type of apparatus requires less maintenance, the number of moving parts being radically reduced. Mechanical strength is also improved throughout the apparatus by virtue of a minor fatigue stress, especially the fact that no reciprocating or gyroscopic motion is necessary. In terms of its adjustability, the apparatus can be designed to be easier and quicker than those available at present.

It is an object of the invention to provide an apparatus of the above discussed type, which offers a simple and reliable possibility in the event of malfunction of diverting wood chips already sorted out in the apparatus or still to be sorted past the defective mechanical component in amongst the accepted chips (ac- cept) and, thus, of avoiding the situation in which the process associated with the apparatus would have to be completely aborted.

According to the invention this object is accomplished in such a way that, and an apparatus of the invention is characterized in that the apparatus comprises a power-operated component conveying the wood chips sorted out by means of the apparatus, and a guide surface arranged in line therewith, which are dimensioned such that the wood chips are diverted by the action of gravity partially or totally past said component by way of a sliding surface established by the wood chips accumulated in the event of malfunction on top of the com- ponent, and by way of said guide surface.

In one preferred embodiment of the invention, the arrangement is such that at least two pieces of apparatus are set in sequence, such that the processing- bound wood chips are adapted to pass gravitationally through the pieces of apparatus between the power-operated component conveying the unsorted wood chips and/or the power-operated components conveying the sorted wood chips, respectively included therein. In yet another preferred embodiment of the invention, the arrangement is such that the fraction of chips sorted out as having excess thickness (reject) by the apparatus upstream in the wood chips' advancing direction is adapted to fall gravitationally into the feeder of the downstream apparatus.

In a still further preferred embodiment of the invention, the arrangement is such that said downstream apparatus has the inlet side of its feeder dimensioned such that the fraction of chips sorted out as having excess thickness (reject) by the apparatus upstream in the wood chips' advancing direction is adapted in the event of overload or malfunction to proceed gravitationally in amongst the accepted chips (accept).

In still another preferred embodiment of the invention, the arrangement is such that, with regard to said at least two pieces of apparatus, the last one down- stream in the wood chips' advancing direction is provided with a conveyor for removing excess thickness chips (reject) from the apparatus, said conveyor having its inlet side dimensioned in such a way that in the event of overload or malfunction the reject is adapted to proceed gravitationally in amongst the accepted chips (accept).

The invention will now be described in more detail with reference to the accompanying drawings, in which:

Fig. 1 shows an apparatus of the invention in a diagrammatic section.

Fig. 1 shows schematically an apparatus for sorting wood chips 1 in separate fractions. Fines particles 13, possibly contained in the wood chips 1, are sorted out to form a separate fraction and individual chips 11 , 12 are determined by the thickness thereof as excess thickness chips 11 (reject) and accepted chips 12 (accept).

The apparatus comprises a feeder 6 for supplying the wood chips 1 onto a sloping support surface 2 for a substantially single layer. The individual chips 11 , 12 settle in a natural way on the support surface 2 to rest upon the largest surface thereof, i.e. in the case of wood chips, upon the longitudinal/lateral surface thereof.

The support surface 2 is a solid, plain, and durable flat surface, which forms a steeply sloping slide surface for the wood chips 1 to be sorted.

The wood chips 1 emerging from the feeder 6 are first adapted to slide down the sloping support surface 2 and then over a slit 3 arranged across the support surface, said slit being adapted to deliver an impulse action 4 directed away from said support surface 2 and applied to one or more chips 11 , 12 or fines particles 13 presently in line with the slit. The impulse action is adapted to be produced by means of a gas flow 4, preferably an air flow. The impulse action 4 may have a direction which is perpendicular to the support surface 2, or also at an oblique angle relative to the support surface 2.

The air flow is generated by a fan 7. In order to secure uniformity of the impulse action 4, a nozzle chamber 8 is arranged between the fan 7 and the slit 3.

The individual chips 11, 12 of varying thickness and the eventual fines particles 13 are adapted to be separated from each other along various trajectories established by the impulse action 4 for the particles to be sorted.

The fines particles 13, which are smaller in size than the width of the slit 3, adopt a maximum deviation of velocity and, thus, are adapted to be deflected by the action of a guide/baffle 14 in a separate fraction into a chute 15.

The individual chips 11 , 12, which are substantially larger in size than the width of the slit 3 and, thus, heavier than said fines particles 13, adopt a deviation of velocity which is substantially less than that adopted by the fines particles 13 when present in line with the slit 3. A pressure-generated impulse sends the individual chips 11 , 12 flying in different trajectories defined by a chip thickness, and the flow of chips is divided in separate fractions by means of a separating wall 5. The averagely minimum thickness chips 12 fly over the separat- ing wall 5 and are further guided to a discharge screw 10. Respectively, the averagely maximum thickness chips fly a shorter distance and fall into a feeder 6' present between the separating wall 5 and the slit 3.

In the illustrated example, the averagely maximum thickness chips 11 received in the feeder 6' are reprocessed in a downstream second apparatus, whereby a fraction thereof (the averagely lightest fraction) is guided over a separating wall 5' further onto the discharge screw 10, and another fraction (the averagely heaviest fraction) falls into a chute present between the separating wall 5' and the slit 3 and provided with a discharge screw 9.

Processing of the wood chips 1 is overall adapted to take place in a dustproof processing chamber 17. The discharge of air is effected through an opening represented by reference numeral 34.

In the exemplary embodiment of fig. 1 , the gas flow 4 emerging from a top nozzle chamber 8 on the one hand separates the fines particles into the chute 15 and on the other hand divides the chips in such a way that the chips 11 determined by the trajectory as having excess thickness end up in the bucket feeder 6' and the chips 12 determined as acceptable fly over the separating wall 5 and fall on top of the discharge screw 10.

The chips emerging from the bucket feeder 6' are further resorted by means of the gas flow 4 discharging from a nozzle chamber 8', whereby the chips 11 , determined again by the trajectory as having excess thickness, fall on top of the discharge screw 9 and the chips 12 determined as acceptable fly over a separating wall 5" and fall on top of the discharge screw 10.

In order to avoid the need of immediately stopping the entire apparatus, for example in the event of possible malfunction of the bucket feeder 6', alongside the bucket feeder 6' is provided a guide surface 30, along which the excess thickness chips 11 accumulating on top of the bucket feeder 6' begin to slide, as soon as a sufficient pile of chips has developed on top of the bucket feeder 6' for establishing a sliding surface 33. Instead of the separate guide surface 30, the separating wall 5 may have its top surface 32 establish a necessary guide surface for diverting all chips to land on top of the discharge screw 10 in the event of malfunction.

Respectively, in the event of malfunction of the discharge screw 9, all chips are adapted to slide, as the discharge screw 9 is being filled up, along a guide surface 31 , or optionally along the top surface 32 of the separating wall 5', to land on top of the discharge screw 10.

Claims

1. An apparatus for sorting wood chips (1), involving chips (11 , 12) in a variety of sizes and similar, substantially hexahedral pieces having a length and a width, as well as a thickness substantially less than the latter, and possibly fines particles (13), by means of an impulse action, such that the excess thickness chips (11) or the fines particles (13), or both the excess thickness chips (11) and the fines particles (13) are separated from the wood chips (1) to form a separate fraction, the miscellaneous chips (11 , 12) and the fines particles (13) being adapted to be sorted from each other by means of one or more separating walls (5, 5') arranged to comply with various trajectories established by means of the impulse action, said apparatus comprising a feeder (6, 6') for supplying the wood chips (1) onto a sloping support surface (2) and for sliding the same along said support surface (2) over a slit (3) extending thereacross, said slit being adapted to provide an impulse action therethrough by means of a continuous gas flow (4) on the chips (11 , 12) or the fines particles (13) presently in line with the slit (3), characterized in that the apparatus comprises a power-operated component (6', 9) conveying the wood chips (1) sorted out by means of the apparatus, and a guide surface (30, 31 , 32) arranged in line therewith, which are dimensioned such that the wood chips (1) are diverted by the action of gravity partially or totally past said component (6', 9) by way of a sliding surface (33) established by the wood chips accumulated on top of the component in the event of malfunction, and by way of said guide surface (30, 31 , 32).

2. An apparatus as set forth in claim 1 , characterized in that at least two pieces of apparatus are set in sequence, such that the processing-bound wood chips (1) are adapted to pass gravitationally through the pieces of apparatus between the power-operated component (6) conveying the unsorted wood chips (1) and/or the power-operated components (6', 9) conveying the sorted wood chips (1), respectively included therein.

3. An apparatus as set forth in claim 2, characterized in that the fraction of chips (11) sorted out as having excess thickness (reject) by the apparatus upstream in the wood chips' (1) advancing direction is adapted to fall gravitationally into the feeder (6') of the downstream apparatus.

4. An apparatus as set forth in claim 2, characterized in that said downstream apparatus has the inlet side of its feeder (6') dimensioned such that the fraction of chips (11) sorted out as having excess thickness (reject) by the apparatus upstream in the wood chips' (1) advancing direction is adapted in the event of overload or malfunction to proceed gravitationally in amongst the accepted chips (12) (accept).

5. An apparatus as set forth in claim 2, characterized in that, with regard to said at least two pieces of apparatus, the last one downstream in the wood chips' (1) advancing direction is provided with a conveyor (9) for removing the excess thickness chips (11) (reject) from the apparatus, said conveyor (9) having its inlet side dimensioned in such a way that in the event of overload or malfunction the reject (11) is adapted to proceed gravitationally in amongst the accepted chips (12) (accept).