GB2042492A - A composting plant for production compost from organic waste material - Google Patents

Abstract

A composting plant for composting organic waste by laying on surface 1 the waste in a substantially circular path in the form of a ring which is broken at one location includes a material-supply conveyor means (7, 8) for conveying waste material from a first station located externally of the ring-shaped path and beneath the surface 1 to the conveyor 9 at centre of said path. Rotatably mounted material-laying conveyor wise to the surface 1. Fully composted material is removed sectorwise by means of rotatably mounted material- removal means (4, 18, 20-23) at the end of the material ring which was first formed, and the material is conveyed to means (10, 11) receive waste material from conveyor 9 and deliver it sector- the centre of the ring and to a removal means (27-31), which remove the fully composted material beneath the surface 1 to a second station located externally of the ring-shaped path. <IMAGE>

Description

SPECIFICATION A composting plant for producing compost from organic waste material Field of invention The present invention relates to a composting plant for producing compost from such organic waste material as household waste, waste wood, vegetation, bark and sewage sludge.

State of the art Waste material is normally composted by mechanically disintegrating said material to a given extent, whereafter the material is placed into a plurality of elongate, mutually parallel heaps, said heaps being formed after a given period of time has lapsed since the forming of a preceding heap. Normally. air is continuously blown through each of said heaps of material to be composted, and when necessary said heaps are moisten with water to facilitate decomposition of the material. Normally, the material to be composted, hereinafter referred to as compost material, is built up to form a heap of given size, whereafter the building of a second heap is started.

When the second heap has reached a given size, building of the next heap is started etc. The building of further heaps is continued until the compost material in the first heap has decomposed to an extent such that it comprises fully composted material, which can be removed for use. When all the material in the first heap has been removed, the remaining heaps are moved one place, so that each heap occupies the place of the previously preceding heap. In this way, the compost material of respective heaps becomes well mixed. The disadvantage with moving the compost heaps in the manner aforementioned are quite significant, however, since much time - consuming work is required, particularly in the case of large compost heaps.

It is also known to lay the compost material in two ring-shaped heaps of different radii, through which air is caused to pass, said heaps being concentrically arranged and separated by an intermediate wall, made of, for example, concrete. The compost material is pre-composted in the inner ring of material, while continued composting ofthe material is effected in the outer ring. Thus, the dimensions of the outer ring can be so large as to enable said ring to serve simultaneously as a storage place for ready composted material. Because the material is composted intermittently in two, mutually separate heaps, it is necessary to move the compost material from one heap to the other, i.e. from the inner ring to the outer ring.Thus, although by placing the compost material in ring-shaped heaps the practical advantage is afforded whereby said heaps exhibit the least possible heat-radiation surface, thus enabling decomposition of the material to be effected more rapidly than when the same material mass is divided into separate heaps, the disadvantages of such a procedure are quite significant. Thus, transport of the material between the inner and outer rings is time consuming and expensive, besides which all the waste material forming the rings will be composted at one and the same point of time. This means that the material to be composted must be stored in readiness when the composting plant is completely empty of composted material, whereby space requirements in the form of available ground areas will be very high.

The aforementioned known technique makes is necessary to move the waste material from one composting location to another during the decomposition process, in order that said process can be controlled in a manner to obtain complete decomposition in all parts of the heap during a given, relatively short period of time. Since the technique of composting waste material is developing towards the use of increasingly larger composting plants and compost heaps, the costs of moving the compost material involves a correspondingly increasing percentage of the total handling costs. This disadvantage is eliminated by means of the present invention, in that the invention enables the decomposing process to be accurately controlled in all parts of the compost heap without it being necessary to move the compost material.

For the purpose of eliminating problems encountered with known composting plants and apparatus, the invention provides a composting plant for producing compost from organic waste material, in which material is placed in a ring-shaped path on a stacking site, said path being broken at one location.

The apparatus includes a radially displaceable ma-terial-laying conveyor which is arranged to rotate horizontally about the centre of the ring-shaped path and which is arranged to receive waste material at said centre and to convey said material radially outwardly from said centre; a material-laying means for receiving composted waste material; and treatment means for stirring or turning the ring of waste material sectorwise and supplying air and liquid thereto.The invention is characterized by a materialsupply conveyor for conveying waste material from a first station located outside the ring-shaped path and beneath the stacking surface of the stacking site, to said centre and to the material-laying conveyor, said material-laying conveyor being arranged to deliver material to the stacking surface sectorwise, to form a ring of material which is broken at one location, said material-removing means being arranged to remove composted waste material in sectors from the end of the ring of material which was first stacked and convey said material to the centre and to a removal conveyor for removing the composted material beneath said stacking surface and conveying said material to a further station located externally of the ring-shaped path.

Advantages ofthe invention Because treatment of the waste material is effected in successively formed ring sectors, there is obtained a controlled, gradual composition of the material, sector by sector, thereby rendering movement of material from one location to another during the treatmentprocess for this purpose unnecessary.

Further, material supplied to the ring will always form a unit with previously supplied material, wherewith departure of the heat required for decem- posing the waste material is mai;;tained within the mass of material to the greatest possible extent. A further advantage resides in the fact that the con- tinuity of the decomposing process is not disturbed by material being continually supplied to the heap or stack of material and removed therefrom. This has been achieved by forming the compost heap in a ringlike shape which is broken at one location and to one end of which material is supplied and removed from the other end thereof, both supply of material and removal of said material being effected sectorwise.

An exemplary embodiment of the invention will now be described with reference to the accompanying drawings.

Brief description ofthe drawings Figure 1 illustrates the plant in side view and partially in cross-section.

Figure 2 illustrates means for laying the waste material in a heap and stirring the heap.

Figure 3 and 4 illustrate means for removing composted waste material from said heap.

Figure 5illustrates means for aerating the heap, and Figure 6 illustrates means for watering said heap.

Preferred embodiments In Figure 1 the reference 1 identifies a ring-shaped waste-material stacking or heaping site arranged on the ground. Sunk in the ground in the centre of the ring is a circular chamber 2. Mounted in the chamber 2 is a cylindrical pillar 3 which extends from the bottom of the chamber 2 upwardly to a level substantially above the surface of the ground. Two elongate piers 4, 5 of lattice construction are each mounted at one end thereof for rotation about the pillar 3 in respective movement paths which, in the case of pier 4, lies close to the surface of the ground, and, in the case of piers E, st a height above the ground greater than the height to which the stack is to be formed.The free Enllss oF the piers are supported by respective wheels 4a and 5a resting on the ground. A culvert 6 extends from the central chamber 2 beneath the surface of the ground in a radial direction, said culvert sloping slightly upwardly and out from the stacking site. Arranged in the culvert6 is a belt conveyor 7 for transporting waste material to be composted from a supply station (not shown) located outside the stacking site, to a screw conveyor 8 arranged in the central chamber 2. The screw conveyor extends horizontally from the infeed end of the belt conveyor 7, and is connected at its other end, through an inlet opening in the pillar 3, to a vertical screw conveyor 9 arranged in said pillar.

The screw conveyor 9 is arranged to convey material upwardly through the pillar and to transfer said material at the upper end of said pillar to a belt conveyor 10 stationarily arranged on the pier 5. The belt conveyor 10 extends radially from the pillar to approximately the centre of the pier, where it is connected to a further belt conveyor 11 arranged at a lower level on the pier, for laying compost material in sectors on the stacking site.The conveyor 11, is a reversible conveyor and can be moved parallel with and beneath the fixed conveyor it 0, between an outer and an inner limit position, in which position it extends from the outfeed end of the fixed conveyor to a position above the outer and inner circular limit lines 1 a, 1 b respectively of the stacking site. The means carrying the conveyor 11 and the means for moving said conveyor in its longitudinal direction are not shown in detail, although said means may, for example, comprise a frame structure 1 1c (Figure 2) in which the two rollers 11 a, 11 b of the conveyor are rotatable journal led, and slide rails 11 d on which the frame is displaceably mounted.At least one of the rollers of each of the two conveyors 10 and 11 is coupled to a respective drive motor, e.g. the drive motor lid, and a reversible motor 1 if is provided for driving the frame lic.

Arranged on the long sides of the pier 5 parallel with the longitudinal axis of said pier are raiis 12, 13 (see also Figure 2) on which a carriage 14 is arranged for movement along the underside of the pier, said carriage being driven by a motor 14a. The carriage carries two downwardly extending screws 15, 16 which can be rotated by a motor 15a, 16a coupled to respective screws, for stirring or turning the waste material laid on the stacking site. Movement of the carriage along the pier is restricted, in a manner not shown in detail, in those positions in which the screws reach the outer and inner circular limit lines la, 1 b of the stacking site.

Arranged on the pier 4 is a belt conveyor 16, which extends parallel with the longitudinal axis of the pier from its outer end to the central chamber 2.

Arranged for movement along the pier 4 is a carriage 20 which is moved by means of a motor not shown.

The carriage 20 carried an obliquely upwardly extending scraper means 21, which extends from the carriage to the upper part of the heap of compost material and form an angle a with the horizontal plane, said angle a being smaller than the angle of repose t3 of said heap. Also arranged on the carriage 20 is a horizontal screw conveyor 22 and a vertical screw conveyor 23 connected to said conveyor 22.

The scraper means 21 is o-r conventional design and may be provided with a screw 21 a driven bye motor 21 b. The screw 21 is arranged to scrape composted material from the outfeed end of the ring-shaped heap of material, down to the ground for feeding into the horizontal screw conveyor 22. The screw conveyor 22 is located close to the surface of the ground and extends transversely of the direction of movement of the carriage along the pier. The conveyor includes a conveyor screw 24 (see Figure 3) driven by a motor (not shown) in a conveyor tube 25. The wall of the conveyor tube is provided along the whole of its length with an infeed opening 2G, said opening being turned obliquely downwardly towards the centre of the composting plant. The conveyor 25 is arranged so that it can be turned about its longitudinal axis to enable the opening 26 to be turned to face selected directions, as hereinaf- ter made apparent. Infeed of material in the horizon tal screw conveyor is effected by moving said conveyor along the pier 4 by the carriage 20 in towards the centre end through the material scraped down by the scraper means, said material being pressed into the screw conveyor through the infeed opening 26.The conveyor screw 24 is threaded in two opposite directions, for conveying material to the centre part of the conveyor tube and for transferring the material to the vertical conveyor 23 connected at said centre part. Material is moved by the conveyor 23 to a level above the pier 4, where said material is fed to the belt conveyor 18. The conveyor 18 transports the material in towards the centre, where it is transferred to two mutually integral hoppers or funnels 27,28 located adjacent the pillar 3. Each hopper is provided with a rectangular bottom part in which there is arranged a horizontal conveyor screw 29,30 (see Figure 4). The conveyor screw 29 is threaded for transporting compost to one end of said rectangular bottom part, at which there is provided a downwardly facing opening for discharging material to a belt conveyor 31 located therebeneath.Between the two hoppers there is provided a space for the pillar 3, said pillar being totally surrounded by the hoppers. In this way, material discharged from the belt conveyor 18 will always fall into the hoppers, irrespective of the position to which the belt conveyor is moved when the pier 4 rotates about the pillar 3. The belt conveyor 31 is arranged in the culvert 6 on one side of the belt conveyor 7 and extends through the culvert for feeding the ready composted material to a receiving station (not shown) located externally of the stacking site.

The composting plant according to the invention also includes means for continuously blowing air through the heap of material, and, when necessary, for supplying water thereto. The aerating means is illustrated schematically Figure 5 and comprises a plurality of perforated pipes 32 arranged on the stacking site at ground level and extending radially between the outer and inner limit lines 1 a, 1 b of said site. The pipes 32 are connected together in sectors to form mutually separated groups 33 around the stacking site, each group of pipes being connected, in turn, by means of a pipe 34, to a fan 35 arranged in the central chamber 2, via a three-path valve 36. The valve is arranged to couple the suction side of the fan or alternatively its pressure side to the groups of pipes 33 over corresponding connecting pipes 34.

Each connecting pipe 34 is provided with a separate valve 37, by which the through-flow area of the pipe can be regulated or the connection between the fan and the corresponding group of pipes shut-off. For the sake of clarity, only one group of pipes 33 has been shown in the Figure. Some of the pipes forming said group have been partly removed in the figure, so as to illustrate the underlying connecting pipe 34.

The watering means comprises a fixed pipe 38 (see Figure 6) located beneath the pier 5, said fixed pipe extending from the end part of the pier at the pillar 3 to a position above the inner limit line 1 b of the stacking site. The pipe is connected at its end adjacent the pillar to a hose 39 made of rubber or some other flexible material, which hose, is, in turn, connected to a pipe (not shown) arranged in the culvert 6 for supplying water from an externally located source of water under pressure. The length of the hose is such that it can be wound several times around the pillar as the pier is rotated, without being stretched. At its opposite end, the pipe 38 connects with two parallel branching pipes 40,41.

These are fixedly mounted in the pier in spaced apart relatingship and extend to a position above the outer limit line 1a of the stacking site. The branch pipes are closed at their free ends, and are provided on their undersides with one or more rows of downwardly facing spray nozzles 42, which are in open communication with the interior of the pipes.

The composting plant has the following mode of operating. When all the infeed conveyors have been started up, waste material can be conveyed to the stacking site. Transport of material is effected with the belt conveyor 7 from the supply station (not shown) located externally of the stacking site, through the culvert 6 to the screw conveyor 8 arranged in the centre. The material is then moved by said conveyor 8 and the conveyor 9 arranged in the pillar 3, to the belt conveyor 10 on the pier 5. It is assumed that the pier has previously been rotated to a position in which it is located over a predetermined sector of the stacking site defined by the corresponding group of pipes 33 arranged sectorwise in the surface of the ground, for example the sector referenced A in Figure 5.The material is transferred from the belt conveyor 10 to the belt conveyor 11, and from there to the stacking site and to the heap-sector A being formed. During laying of the material in said material in said sector the conveyor 11 is moved between its limit positions on the pier while changing the conveying direction, so that material is spread evenly between the arcuate limit lines of the sector. Simultaneously therewith, the pier is rotated forwards and backwards between the straight limit lines 33a, 33b of the sector A until the heap of material within said sector has reached the intended size, when the building of a sector has been completed, the pier is rotated to the nextfollowing sector B ofthe stacking site; the rotation or swinging of said pier is considered to take place always in one and the same direction of rotation.In this way, the heap of material will always grow in one and the same direction around the stacking or heaping site, which, as will later be made clear, is of great advantage.

It is estimated that the time taken to decompose the material to a ready compost in each sector of the heap is about 3 months. During this time, the material is continuously aerated and sprayed with water and stirred or turned sectorwise at intervals of approximately 2 weeks. The heap is aerated by alternately blowing and sucking air in stages through the material, each blow period being 6-7 days and each suction period 2-3 days. While the heap is being aerated, the valves 37 on the connecting pipe 34 are set so that the relevant groups of pipes 33, which are arranged in sections as beforementioned, are connected to the fan 35. The pipes are connected to the pressure side of the fan during the blow periods and to the suction side of said fan during the suction periods, by suitable setting of the three-path valve 36. It will be understood that the flow of air through respective sectors can be reg ulated individually, as can also the amount of air passed thereto. Thus, it is possible hereby to control the decomposition of material in each separate sector with a great deal of accuracy.

Respective sectors of the compost heap are watered by supplying water under pressure to the pipe 38,40 and 41 via the hose 39, said water being sprayed over the material through the nozzles 42 while the pier 5 is rotated backwards and forwards across said sector. Since the pier carries both the means for watering the compost heap and the means for laying the compost material, it is, of course, impossible to carry out these two operations at the same time.

When a sector of the compost heap has been supplied with sufficient water to carry out the process of decomposition, the watered material is stirred or turned for one or more hours. Turning of the material is effected by the screws 15, 16, which are caused to rotate in the material while being moved along the pier 5 by the carriage 14. By also rotating the pier above the sector of material, all parts of said sector can readily be reached by stirring screws. Since the material-stirring means are carried by the pierS, it is not possible to lay material in a sector while the material in said sector is being stirred.

The manner in which the compost heap is formed is suitably planned so that material in the first formed material - sector A has been fully composted while one or more sectors of the stacking site are still empty, for example the sector C (Figure 5). Thus, the compost heap has the form of a ring which is broken at one location (sector C), one end of the broken ring comprising a sector A of the fully composted material and the other end comprises a sector D (Figure 5) comprising material which has just been laid or stacked, or which sector is under the process of being formed. As work is continued, the infeed and outfeed of material is adjusted so that the infeed and outfeed locations at the ends of the ring are continuously moved around the stacking site while substantiaily maintaining the mutual distance between said locations.In this way, fully composted material can always be removed, sectorwise, from one end of the ring, while at the same time, supplying fresh material to the sector at the other end of said ring. This decomposing process, effected stagewise in sectors, enables decomposition of the material to be readily controlled without it being necessary to move the material from one composting location to another during the process.

Subsequent to starting up the outfeed conveyors, material can be removed from the sector at the outfeed end of the compost heap. This is effected by moving the scraper means 21, and the mutually connected screw conveyor 22 and 23, along the pier 4 by means of the carriage 20, towards the inner limit line 1 b of the stacking site, with the pier in position adjacent the outfeed end. During this movement, the horizontal screw conveyor 22 turns the infeed opening 26 obliquely downwardly and in the direction of movement, wherewith the material scraped down by the scraper means is pressed into the conveyor through said opening. When the screw conveyors have been moved by the carriage to the inner limit line 1 b of the stacking site, the direction of movement of the carriage is reversed, whereupon the screw conveyors return, out of operation, to the outer end of the pier.Thus, during the return movement of the conveyors, no material is fed into the horizontal screw conveyor, since it then turns the infeed opening 26 to face the direction of movement.

Consequently, the horizontal screw conveyor only removes material from the compost heap when the carriage is moved in a direction towards the centre of the stating site. Material is transferred from the screw conveyors 22 to the vertical screw conveyor 23 and from there to the belt conveyor 18. The material is conveyed by the belt conveyor to the hoppers 27,28 arranged in the centre, in which hoppers the material is transferred by the conveyor screw 29,30 to the belt conveyor 31, for removal through the culvert 6 out from the stacking site.

The plant can be modified within the scope of the invention. For example, in the illustrated embodiment transport of material is effected in a culvert placed beneath the compost heap, although said material may well be moved instead by conveyors arranged on a bridge structure fixedly mounted above the compost heap. It is also possible to provide a conveyor with scraper conveyors or, when the conveying distance is not excessively long, with screw conveyors instead of the belt conveyors described in the exemplary embodiment The exemplary embodiment has been provided with a fan 35, to the suction side or pressure side of which the sector-laid groups of pipes 33 can be selectively connected for passing air through the compost heap. It may be suitable, however, to use instead two fans, of which one serves as a pressure fan and the other as a suction fan.

It is also conceivable to replace one or more of the screw conveyors of the illustrated embodiment with other suitable conveying means, such as bucket elevators.

The means for stirring or tuning the compost heap can also be varied within the scope of the invention, and need not necessarily have the form of screws illustrated in the exemplary embodiment.

Neither is the invention restricted to the number of screws illustrated. These screws can well be replaced by any other conventional form of agitator, such as for example a plurality of radially extending blades mounted along a vertical rotatable shaft.

It is also possible to arrange the watering means and stirring means on separate piers arranged for rotation about the pillar 3, instead of on the pier 5 carrying the heap-laying conveyors, as illustrated in the exemplary embodiment.

Claims (8)

1. Acomposting plantforcomposting organic waste material, said material being laid in a ringshaped path on a stacking site, said path being broken at one location, said plant including a radially displaceable heap-laying conveyor (10, 11) which is arranged for rotation horizontally around the centre of the ring-shaped path and which is arranged to receive waste material at said centre and to transport said material radially outwardly therefrom; a material-removal means (4, 18,20-23) for removing fully composted material; and treatment means (15, 16, 33,35,40,41) for agitating material in said ring sectorwise, and for supplying air and liquid to said sector of material, characterized by a supplyconveying means (7, 8,9) for supplying waste material from a first station located externally of the ring-shaped path and beneath the surface of the stacking site to said centre and to the heap-laying conveyors (10,11), said heap-laying conveyors being arranged to deliver material sectorwise on the stacking surface to form a material ring which is broken at one location (C), said material - removal means (4, 18,20-23) being arranged to remove fully composted material sectorwise from the end (33a) of the ring which was laid first, and to convey said material towards the centre to a compost - removal conveyor means (27-31) for removing the composted material beneath said surface of said stacking site to a further station located externally of the ringshaped path.

2. A plant according to claim 1, characterized in that the hea p-laying conveyo r (10, 11)is arranged on a pier (5) mounted for rotation about the centre of the stacking site and above said site.

3. A plant according to claim 1 or claim 2, characterized in that the material-supply conveyor means (7,8,9) comprises a belt conveyor (7) for transport of material from a location externally of the stacking site to the centre thereof; a horizontal screw conveyor (8) for receiving the material from the belt conveyor (7) and transporting said material to a vertically upwardly extending screw conveyor (9) connected to the horizontal screw conveyor for transporting said material to the material-laying conveyor (10,11).

4. A plant according to claim 2 or claim 3, characterized in that the material-laying conveyor (10, 11) comprises a first belt conveyor (10) which is stationarily arranged on the pier (5) for receiving at the centre of rotation thereof material from the material-supply conveyor means (7,8,9) and for conveying the material along the pier to a location above the stacking site; and a second belt conveyor means (11) which is arranged on the pier (5) at a lower level than the first belt conveyor (10) for receiving material therefrom, said second belt conveyor (11) being arranged to be moved in its longitudinal direction parallel with and beneath the first belt conveyor (11), thereby to spread the material to all parts of the stacking site in its radial direction.

5. A plant according to any one of claims 1-4, characterized in that the material-removal means (4, 18,20-23) includes a pier (4) mounted for rotation about said centre and over the stacking site, on which pier there is arranged for movement in the longitudinal direction of said pier a motor-driven carriage (20) which carries a scraper means (21) arranged to scrape material from the compost heap, a horizontal screw conveyor (22) extending in the cross-direction of the pier and being located close to the surface of the ground with an infeed opening (26) turned obliquely downwardly for feeding the material scraped down by said scraper means into the conveyor when the carriage is moved in one of its directions of movement and which is connected to a vertical screw conveyor (23) arranged on the carriage for transferring the material from the horizontal screw conveyor (22) to a belt conveyor (18) arranged on said pier for conveying material to the centre of the stacking site and the means (31) extending therefrom for carrying away said material.

6. A plant according to any one of ciaims 2-5, characterized in that the mans for supplying liquid to the compost heap is arranged on the pier (5) carrying the material-laying conveyor, and comprises one or more pipes (40,41) having downwardly-directed spray openings (42), said pipes being arranged to be connected to a source of liquid under pressure.

7. A plant according to anyone of claims 2-6, characterized in that the apparatus for stirring or agitating the material in said heap is arranged on the pier (5) carrying the material-laying conveyor, and comprises a motor-driven carriage (14) arranged for movement along the pier and carrying one or more rotatably journalled, motor-driven agitating means (15, 16) which extend from the carriage downwardly to a level close to the surface of the ground.

8. A composting plant constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.