Patent Publication Number: US-8109392-B2

Title: Apparatus and method for removing impurities in crushed recycled material

Description:
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 (&gt;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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments of the present invention will now be described by way of examples only, with reference to the accompanying drawings, wherein: 
         FIG. 1  shows a schematic cross-sectional side view of an apparatus to remove impurities in crushed concrete; 
         FIG. 2  shows a blower assembly for the apparatus of  FIG. 1 ; 
         FIG. 3  shows a blower outlet assembly for the first chute of the apparatus of  FIG. 1 ; 
         FIG. 4  is a schematic cross-section side view of a modification of the apparatus of  FIG. 1 ; 
         FIG. 5  is a schematic illustration of a blower assembly employed in the apparatus of  FIG. 4 ; and 
         FIG. 6  is a schematic side elevation of a blower to be used with the apparatus of  FIG. 4 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows an apparatus  10  according to a preferred embodiment of the present invention. The apparatus  10  is shown attached to a triple deck screen apparatus  100  and mounted on top of a flatbed trailer  120  having wheels  121 . 
     The screen apparatus  100  includes an upper first screen  102 , a middle second screen  104 , a lower third screen  106  and a chute  108  below the third screen  106 . The screens  102 ,  104  and  106  are horizontal, of similar dimensions and placed one on top of the other. The screen  102  has an outlet  103 , the second screen  104  has an outlet  105 , and the third screen  106  has an outlet  107 . A dust conveyor  122  is mounted onto the trailer  120  below the chute  108 . 
     The screen  100  can be any of the known multiple deck screens commercially available, such as the Cedar Rapids Triple Deck Screen. 
     The apparatus  10  includes an upper first chute  12 , a middle second chute  14  and a lower third chute  16 , each providing a duct along which the crushed concrete is to flow under the influence of gravity. The chutes  12 ,  14  and  16  are as wide as the screens  102 ,  104  and  106 . The first chute  12  is angled downwardly and includes an inlet  50  and an outlet  51  below and downstream from the inlet  50 . The first chute inlet  50  is connected to the first screen outlet  103 . 
     The second chute  14  is also angled downwardly, and includes an inlet  52 , a first outlet  15  below and downstream from the inlet  52 , and a second outlet  23 . The second chute inlet  52  is connected to the second screen outlet  105 . A conveyor  20  is arranged below the second chute outlet  15 , and the lower outlet  23  connects to an outlet  18 . 
     The third chute  16  includes an inlet  54 , a first outlet  21  below and downstream from the inlet  54 , and a second lower outlet  24 . The third chute inlet  54  is connected to the third screen outlet  107 . A conveyor  22  is arranged below the second chute outlet  21 , and the lower outlet  24  connects to the outlet  18 . 
     The second chute  14  includes a blower outlet  30   a  arranged immediately upstream of the outlet  15  thereof, and the third chute  16  includes a blower outlet  30   b  arranged immediately upstream of the outlet  21  thereof. The blower outlets  30   a  and  30   b  will be further described below. Arranged upstream of the blower outlets  30   a  and  30   b  are retardation curtains  19 . 
       FIG. 2  shows a blower assembly  29  for the apparatus  10 . The blower assembly  29  includes a blower machine  38  having an outlet connected to a first duct  37 . The first duct  37  includes a split end outlet, each outlet being connected to second ducts  36 , which are respectively connected to third ducts  35 . The third ducts  35  are connected by elbow pipes  34  to mid-portions of blower pipes  31 . The blower outlets  30   a  and  30   b  shown in  FIG. 1  consist of the third ducts  35 , elbow pipes  34  and the blower pipes  31 . Each blower pipe  31  includes closed end plates  33  at ends thereof and a number of spaced holes  32  formed along its length. The size of the holes  32  may vary depending on the air pressure required. The length of each blower pipe  31  extends the width of the respective second chute  14  or third chute  16 . 
     The blower machine  38  is operable to supply high pressure air to the blower pipes  31 , exiting same via the spaced holes  32 . Slidable valves  39  are arranged at the outlets of the first duct  37 , 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 pipes  31  can be altered as desired. 
       FIG. 3  shows a blower outlet assembly  60  for the first chute  12  of the apparatus  10 . The assembly  60  is an optional feature of the apparatus  10  and is not shown in  FIG. 1 . The assembly  60  can be arranged below and downstream of the retardation curtain  19  of the first chute  12 . The blower outlet assembly  60  includes a pipe  43  connected to a transition duct  42  which is connected to an opening  40  at the bottom wall of the chute  12 . A mesh panel  41  extends across the opening  40 . A bar  45  is disposed across the chute  12  immediately upstream and above the opening  40 . Opposite to the opening  40 , a reject material outlet opening  47  is formed in the upper wall of the chute  12 . Baffle plates  46  extend from the opening  47  wider than the opening  40 . Connected to the outlet  47  is a hood  48  which leads to a reject material duct  49 . The first chute  12  may also contain a blower pipe (the same as blower pipes  31 ). In other applications, all chutes may have a blower installed and the capacity of blowers may vary. 
     The pipe duct  43  receives high pressure air from the blower  38  as indicated by arrow  44 . Arranged in the pipe  43  is a slidable valve  39  for altering the volume of air exiting the opening  40 . 
     The use of the apparatus  10  will now be described. 
     Referring to  FIG. 1 , crushed concrete having impurities is poured onto the screen apparatus  100 . The screens  102 ,  104  and  106  are moved in a known manner in order to separate the crushed concrete particles into separate sizes. The screen  102  is sized to allow particles having dimensions less than 80 mm to pass therethrough onto the second screen  104 . Particles having a dimension greater than 80 mm are moved by the screen  102  onto its outlet  103 . The screen  104  is sized to allow particles having dimensions less than 20 mm to pass therethrough onto the third screen  106 . Particles which have a dimension greater than 20 mm (but less than 80 mm due to the first screen  102 ) are moved by the screen  104  onto its outlet  105 . The third screen  106  allows particles having dimensions less than 10 mm to pass therethrough onto the chute  108  and conveyor  122 . Particles having a dimension greater than 10 mm (but less than 20 mm due to the screen  104 ) are moved by the screen  106  onto its outlet  107 . 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 conveyor  122  are collected. At the third screen outlet  107 , the particles fall substantially as a sheet across the width of the screen  106  into the chute  16  and across the blower outlet  30   b . The natural path for the particles will be toward the outlet  21 . As mentioned above, the blower machine  38  forces high pressure air out through the blower outlets  30   a  and  30   b . The outlet  30   b  thus 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 outlet  24 , while the heavier crushed concrete falls through into the first outlet  21 . The impurities are thus substantially removed from the crushed concrete. The crushed concrete is collected by the conveyor  22  and the impurities fall into the outlet  18 . 
     At the second screen outlet  105 , the particles also fall substantially as a sheet across the width of the screen  104  into the chute  14  and across the blower outlet  30   a . The natural path for the particles will be toward the outlet  15 . The outlet  30   a  blows 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 outlet  23  and into outlet  18 , while the heavier crushed concrete falls through into the first outlet  15 . The crushed concrete substantially free of impurities is collected by the conveyor  20 . 
     At the first screen outlet  103 , the particles also fall substantially as a sheet across the width of the screen  102  into the chute  12 . If the apparatus  10  includes the blower outlet assembly  60 , referring to  FIG. 3 , the particles fall along the bottom wall of the chute  12 . The natural path for the particles will be toward the outlet  51 . The falling particles strike the bar  45  at which the particles are “bounced” into mid-air. As the particles are suspended in mid-air within the chute  12 , high pressure air from the duct  43  is forced through the suspended particles. The baffles  46  substantially ensure that the air stream from the outlet  40  is directed into the outlet  47 . Impurities lighter than the crushed concrete are blown into the hood  48  and duct  49 , allowing the heavier concrete material to fall into the chute outlet  51 . The crushed concrete collected at the outlet  51  is sent to a crusher to be re-crushed and re-classified by the screen apparatus  100 . 
     The apparatus  10  thus 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 valves  39  in the ducts  37  and  43  allow 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 curtains  19  substantially spread the particles in a thin sheet-like layer and slow the speed of the particles falling down the chutes prior to the blower outlets  30   a ,  30   b  and  40  for increased effectiveness of the apparatus  10 . The operation of the screen apparatus  100  can 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 pipes  31  of the outlets  30   a  and  30   b . This increases the effectiveness of the apparatus  10 . In the embodiment, the pipes  31  have a diameter of 114.3 mm and a thickness of 4.5 mm. The holes  32  are 10 mm in diameter and spaced 20 mm apart. The holes  32  are countersunk and de-burred on the inside. The outlet pipes  31  are axially rotated such that the holes  32  are at an angle of about 23° to the horizontal. This has been found to be the most effective angle for the apparatus  10 . 
     The elbow pipes  34  are standard 90° elbows. The third ducts  35  are made from the same material as the pipes  31 . The second duct  36  has 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 duct  36 . The first duct  37  is made from galvanized steel and has a diameter of 125 mm. The blower  38  in 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 chutes  12 ,  14  and  16  are 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 blower  38 , multiple blowers can be used in the present invention, one for each outlet  30   a ,  30   b  or  41 . An example of such a blower  38  is shown in  FIG. 6 . Also, the present invention can be installed in a permanent recycling facility, rather than on a trailer. In the blower assembly  29 , it is also possible to simply connect the second duct  36  to an end of the pipes  31  and not use the third ducts  35  and elbow pipe  34 . This arrangement can be used if there is insufficient space to insert the outlets  30   a  and  30   b  into the apparatus  10 . Such an arrangement however is less preferred as it does not provide an even output of air along the length of the pipes  31 . 
     In  FIGS. 4 to 6  there is schematically depicted a modification of the apparatus  10 . In this example, the upper chute  12  also includes the inlet  50  and the outlet  51 ; however intermediate thereof is an impurities outlet  53  on one side of the chute  12 , while opposite the outlet  53  is a blower outlet  30   c . The outlet  53  communicates with a chute  17  down which impurities are ducted. 
     The outlet  51  delivers crushed concrete to a conveyor  55 , with the outlets  23  and  24  delivering impurities to a single conveyor  56 . 
     In this embodiment each blower  38  delivers air to a single blower outlet  30 . Also in this embodiment only a single baffle  46  is employed, that baffle  46  being downstream of the outlet  41 . The same can be applied to the other prior outlets. 
     In the modification of the apparatus  10  as shown in  FIGS. 3 and 5 , the duct  49  is spaced from the duct  12 , while in  FIG. 4 , the duct  49  is adjacent the duct  12 . 
     In the above embodiments, the ducts  12 ,  14  and  16  are located so as to be vertically stacked, that is, the duct  14  above the duct  16 , and the duct  12  above the duct  14 . 
     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.