Apparatus and method for removing impurities in crushed recycled material

A concrete processing apparatus (10) including at least one chute (14) along which crushed concrete and impurities is to pass. The chute (14) is downwardly inclined and has an air outlet to which air is delivered from a blower (29). An air stream issuing from the air outlet is directed across the interior of the chute (14) to deliver impurities to an impurities outlet (23).

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a U.S. National Phase and claims the benefit of PCT Patent Application No. PCT/AU2006/000947, filed Jul. 5, 2006, which claims the priority of Australian Patent Application No. 2005904700, filed Aug. 29, 2005, the disclosures of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an apparatus and method for removing impurities in crushed material such as concrete to be recycled.

BACKGROUND OF THE INVENTION

When a concrete building is demolished, the demolished concrete is transported in small pieces by trucks to a concrete recycling facility. The concrete material is crushed and transferred to a conveyor where magnets are used to remove metallic objects from the crushed concrete. Large non-metallic material is removed manually. After these processes, what is typically left is concrete crushed to about 80 mm minus, meaning concrete particles having a dimension of 80 mm or less. The crushed concrete is separated using multiple deck grated screens into different sizes of 80 mm plus (>80 mm), 20 mm (having a dimension of 80-20 mm), 10 mm (20-10 mm) and minus 10 mm (“dust”). Material which is 80 mm plus is returned by conveyor to a secondary crusher to be crushed again and then returned to the screens for sizing.

Generally, recycled 80 mm minus, 20 mm minus and dust concrete can be used again in the building of new buildings or for other purposes. The crushed concrete however is contaminated with large amounts of foreign material such as timber, plastics, light aluminum, wire, asbestos, and other material.

Numerous apparatus and methods for removing impurities from crushed recycled concrete have been proposed. However, the current methods are either not effective or too expensive to be commercially viable.

SUMMARY OF THE INVENTION

It is an object of the present invention to substantially overcome or at least ameliorate the prior art disadvantages or at least provide a useful alternative.

There is disclosed herein a processing apparatus to remove impurities from crushed material that is to be recycled, the apparatus including:

a chute having an interior along which crushed material having impurities is to pass under the influence of gravity, the chute having an impurities outlet disposed on a first side of the chute, and an air outlet disposed on a side opposite the impurities outlet so that an air stream issuing from the air outlet passes across the interior towards the first side; and

a blower means connected to the air outlet to deliver air thereto so that the stream passes through the crushed material passing along the chute to engage the impurities to deliver the impurities to the impurities outlet while permitting the crushed material to continue along the chute.

Preferably, the chute is inclined to the horizontal by the acute angle so that the first side is above the opposite side.

Preferably, the chute has a transverse width, with the air outlet extending across the width.

Preferably, the apparatus further includes speed retarding means to retard speed of the crushed concrete passing along the interior, the retarding means being located upstream of the air outlet.

Preferably, the apparatus further includes a bar extending transversely across the interior adjacent the opposite wall at a position upstream of the air outlet.

Preferably, the air outlet is configured so that the air stream is evenly distributed across the chute.

Preferably, the apparatus further includes means to adjust the flow rate of air delivered to the air outlet.

Preferably, the apparatus is an apparatus to process crushed concrete.

There is also disclosed herein an assembly including a plurality of concrete processing apparatuses, each apparatus being a concrete processing apparatus as described above.

There is further disclosed herein, in combination, the above assembly, and a sieve apparatus, the sieve apparatus being adapted to provide crushed concrete in several streams, each stream having crushed concrete of a desired size, with each stream being associated with a respective one of the processing apparatuses.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows an apparatus10according to a preferred embodiment of the present invention. The apparatus10is shown attached to a triple deck screen apparatus100and mounted on top of a flatbed trailer120having wheels121.

The screen apparatus100includes an upper first screen102, a middle second screen104, a lower third screen106and a chute108below the third screen106. The screens102,104and106are horizontal, of similar dimensions and placed one on top of the other. The screen102has an outlet103, the second screen104has an outlet105, and the third screen106has an outlet107. A dust conveyor122is mounted onto the trailer120below the chute108.

The screen100can be any of the known multiple deck screens commercially available, such as the Cedar Rapids Triple Deck Screen.

The apparatus10includes an upper first chute12, a middle second chute14and a lower third chute16, each providing a duct along which the crushed concrete is to flow under the influence of gravity. The chutes12,14and16are as wide as the screens102,104and106. The first chute12is angled downwardly and includes an inlet50and an outlet51below and downstream from the inlet50. The first chute inlet50is connected to the first screen outlet103.

The second chute14is also angled downwardly, and includes an inlet52, a first outlet15below and downstream from the inlet52, and a second outlet23. The second chute inlet52is connected to the second screen outlet105. A conveyor20is arranged below the second chute outlet15, and the lower outlet23connects to an outlet18.

The third chute16includes an inlet54, a first outlet21below and downstream from the inlet54, and a second lower outlet24. The third chute inlet54is connected to the third screen outlet107. A conveyor22is arranged below the second chute outlet21, and the lower outlet24connects to the outlet18.

The second chute14includes a blower outlet30aarranged immediately upstream of the outlet15thereof, and the third chute16includes a blower outlet30barranged immediately upstream of the outlet21thereof. The blower outlets30aand30bwill be further described below. Arranged upstream of the blower outlets30aand30bare retardation curtains19.

FIG. 2shows a blower assembly29for the apparatus10. The blower assembly29includes a blower machine38having an outlet connected to a first duct37. The first duct37includes a split end outlet, each outlet being connected to second ducts36, which are respectively connected to third ducts35. The third ducts35are connected by elbow pipes34to mid-portions of blower pipes31. The blower outlets30aand30bshown inFIG. 1consist of the third ducts35, elbow pipes34and the blower pipes31. Each blower pipe31includes closed end plates33at ends thereof and a number of spaced holes32formed along its length. The size of the holes32may vary depending on the air pressure required. The length of each blower pipe31extends the width of the respective second chute14or third chute16.

The blower machine38is operable to supply high pressure air to the blower pipes31, exiting same via the spaced holes32. Slidable valves39are arranged at the outlets of the first duct37, which are slidable from a fully open position (at which the first duct outlet is fully open) to a substantially closed position (at which the first duct outlet is substantially closed) such that the amount of air exiting the pipes31can be altered as desired.

FIG. 3shows a blower outlet assembly60for the first chute12of the apparatus10. The assembly60is an optional feature of the apparatus10and is not shown inFIG. 1. The assembly60can be arranged below and downstream of the retardation curtain19of the first chute12. The blower outlet assembly60includes a pipe43connected to a transition duct42which is connected to an opening40at the bottom wall of the chute12. A mesh panel41extends across the opening40. A bar45is disposed across the chute12immediately upstream and above the opening40. Opposite to the opening40, a reject material outlet opening47is formed in the upper wall of the chute12. Baffle plates46extend from the opening47wider than the opening40. Connected to the outlet47is a hood48which leads to a reject material duct49. The first chute12may also contain a blower pipe (the same as blower pipes31). In other applications, all chutes may have a blower installed and the capacity of blowers may vary.

The pipe duct43receives high pressure air from the blower38as indicated by arrow44. Arranged in the pipe43is a slidable valve39for altering the volume of air exiting the opening40.

The use of the apparatus10will now be described.

Referring toFIG. 1, crushed concrete having impurities is poured onto the screen apparatus100. The screens102,104and106are moved in a known manner in order to separate the crushed concrete particles into separate sizes. The screen102is sized to allow particles having dimensions less than 80 mm to pass therethrough onto the second screen104. Particles having a dimension greater than 80 mm are moved by the screen102onto its outlet103. The screen104is sized to allow particles having dimensions less than 20 mm to pass therethrough onto the third screen106. Particles which have a dimension greater than 20 mm (but less than 80 mm due to the first screen102) are moved by the screen104onto its outlet105. The third screen106allows particles having dimensions less than 10 mm to pass therethrough onto the chute108and conveyor122. Particles having a dimension greater than 10 mm (but less than 20 mm due to the screen104) are moved by the screen106onto its outlet107. In other applications, the size of the screens may be different and the particle sizes of 80 mm, 20 mm and 10 mm are specific to this embodiment only.

The particles having dimensions less than 10 mm received by the conveyor122are collected. At the third screen outlet107, the particles fall substantially as a sheet across the width of the screen106into the chute16and across the blower outlet30b. The natural path for the particles will be toward the outlet21. As mentioned above, the blower machine38forces high pressure air out through the blower outlets30aand30b. The outlet30bthus blows high pressure air across and through the falling particles. The impurities within the crushed concrete which are lighter than the concrete, such as wood and plastics, are forced by the air stream into the second outlet24, while the heavier crushed concrete falls through into the first outlet21. The impurities are thus substantially removed from the crushed concrete. The crushed concrete is collected by the conveyor22and the impurities fall into the outlet18.

At the second screen outlet105, the particles also fall substantially as a sheet across the width of the screen104into the chute14and across the blower outlet30a. The natural path for the particles will be toward the outlet15. The outlet30ablows high pressure air across and through the falling particles. The impurities within the crushed concrete lighter than the concrete are forced by the air stream into the second outlet23and into outlet18, while the heavier crushed concrete falls through into the first outlet15. The crushed concrete substantially free of impurities is collected by the conveyor20.

At the first screen outlet103, the particles also fall substantially as a sheet across the width of the screen102into the chute12. If the apparatus10includes the blower outlet assembly60, referring toFIG. 3, the particles fall along the bottom wall of the chute12. The natural path for the particles will be toward the outlet51. The falling particles strike the bar45at which the particles are “bounced” into mid-air. As the particles are suspended in mid-air within the chute12, high pressure air from the duct43is forced through the suspended particles. The baffles46substantially ensure that the air stream from the outlet40is directed into the outlet47. Impurities lighter than the crushed concrete are blown into the hood48and duct49, allowing the heavier concrete material to fall into the chute outlet51. The crushed concrete collected at the outlet51is sent to a crusher to be re-crushed and re-classified by the screen apparatus100.

The apparatus10thus provides recycled 10 mm and 20 mm recycled concrete which is substantially free of impurities, or at the least having significantly fewer impurities than prior art apparatuses.

The sliding valves39in the ducts37and43allow a user to adjust the volume of air forced through the crushed particles to ensure that (1) the air pressure is sufficient to remove the impurities and (2) the air pressure is not excessive in that crushed concrete particles are also forced into the second outlets with the impurities.

The retardation curtains19substantially spread the particles in a thin sheet-like layer and slow the speed of the particles falling down the chutes prior to the blower outlets30a,30band40for increased effectiveness of the apparatus10. The operation of the screen apparatus100can also assist in ensuring that the volume of particle output therefrom is not excessive.

Air is forced out substantially evenly along the length of the pipes31of the outlets30aand30b. This increases the effectiveness of the apparatus10. In the embodiment, the pipes31have a diameter of 114.3 mm and a thickness of 4.5 mm. The holes32are 10 mm in diameter and spaced 20 mm apart. The holes32are countersunk and de-burred on the inside. The outlet pipes31are axially rotated such that the holes32are at an angle of about 23° to the horizontal. This has been found to be the most effective angle for the apparatus10.

The elbow pipes34are standard 90° elbows. The third ducts35are made from the same material as the pipes31. The second duct36has a diameter of 127 mm and is made from flexible plastics material (e.g. PVC) having a concertina fold therein to reduce vibration in the duct36. The first duct37is made from galvanized steel and has a diameter of 125 mm. The blower38in the embodiment is mounted on a free-standing support structure and has the capacity of blowing 2500 cfm of air at a pressure of 42″ WC.

The chutes12,14and16are downwardly inclined at an angle to suit the application.

Other materials that can be blown are bricks, tiles, pavers, masonry blocks, roof tiles and glass.

Although preferred embodiments of the present invention have been described, it will be apparent to skilled persons that modifications can be made to the above embodiments or that the present invention can be embodied in other forms.

For example, instead of utilizing a single blower38, multiple blowers can be used in the present invention, one for each outlet30a,30bor41. An example of such a blower38is shown inFIG. 6. Also, the present invention can be installed in a permanent recycling facility, rather than on a trailer. In the blower assembly29, it is also possible to simply connect the second duct36to an end of the pipes31and not use the third ducts35and elbow pipe34. This arrangement can be used if there is insufficient space to insert the outlets30aand30binto the apparatus10. Such an arrangement however is less preferred as it does not provide an even output of air along the length of the pipes31.

InFIGS. 4 to 6there is schematically depicted a modification of the apparatus10. In this example, the upper chute12also includes the inlet50and the outlet51; however intermediate thereof is an impurities outlet53on one side of the chute12, while opposite the outlet53is a blower outlet30c. The outlet53communicates with a chute17down which impurities are ducted.

The outlet51delivers crushed concrete to a conveyor55, with the outlets23and24delivering impurities to a single conveyor56.

In this embodiment each blower38delivers air to a single blower outlet30. Also in this embodiment only a single baffle46is employed, that baffle46being downstream of the outlet41. The same can be applied to the other prior outlets.

In the modification of the apparatus10as shown inFIGS. 3 and 5, the duct49is spaced from the duct12, while inFIG. 4, the duct49is adjacent the duct12.

In the above embodiments, the ducts12,14and16are located so as to be vertically stacked, that is, the duct14above the duct16, and the duct12above the duct14.

The above embodiments are described with reference to processing crushed concrete. In that regard the above embodiments could be adapted to process the crushed materials to be recycled.