Abstract:
A method and apparatus for separating adhered paper from paper-covered gypsum board, involving passing the gypsum board past a magnet to automatically remove ferrous materials from the gypsum board without stopping the process/apparatus, pulverizing that gypsum board into a screenable mixture of pieces of paper and smaller separated gypsum board particles, and then screening that mixture and segregating the pieces of paper from the gypsum board particles. This method and apparatus may optionally also include an area for manually pre-sorting and removing non-gypsum materials from the gypsum board prior to pulverization, may optionally also include additional screening steps, and may optionally also include passing the screened and segregated gypsum board particles past a second magnet. The magnets may have self-cleaning belts.

Description:
TECHNICAL FIELD 
     This invention relates to the separation of adhered paper from paper-covered gypsum board, and has application in the recovery and recycling of gypsum and paper from paper-covered gypsum board. 
     BACKGROUND 
     In the residential and commercial construction industries, gypsum board with paper adhered to the surfaces thereof (often referred to as gypsum wallboard, or simply wallboard) is an extensively used building material. Generally, it is supplied in the form of large rectangular sheets, which the builder cuts to size depending upon the particular project. 
     Although efforts may be made to minimize the wastage of material, a single construction site will often generate a substantial amount of leftover gypsum wallboard pieces which are essentially useless and which require disposal. A need for disposal also arises when homes or buildings containing gypsum wallboard are demolished. 
     Historically, the disposal of wallboard material has posed a problem. At the very least it is an uneconomic nuisance and, in some jurisdictions, it is considered to be an unacceptable environmental hazard. The material is not readily degradable and disposal may be prohibited at conventional dumps or waste fill sites. In some cases, the material is transported by barge and disposed of at sea. 
     The disposal problem arises because waste wallboard has no significant practical purpose so long as the paper and gypsum board remain adhered together. Further, when exposed to the weather and outside environmental conditions, the combination can deteriorate to a polluting sludge of paper and gypsum. On the other hand, if the paper and the gypsum board are separated, the sludge problem can be avoided. Furthermore, if the separation is sufficiently complete, then the paper and/or the gypsum can be recycled. 
     Accordingly, efforts have been made to achieve a separation of the adhered paper from scrap wallboard. One such method has involved the pulverization of the wallboard, but the resulting product has been a somewhat inefficient and difficult-to-manage mixture of gypsum board particles and paper fluff. Even so, pulverization is preferable over another known method of using a shredder in conjunction with one-stage or twostage air aspiration to separate paper from non-paper waste; the shredder produces a great deal of fluff and the aspirators are expensive and complicated. As well, it is understood that chemical processes have been tried, but with results considered unsatisfactory either by reason of insufficient separation or excessive cost. 
     U.S. Pat. No. 5,593,096 is a suggested improved method and apparatus for wallboard recycling wherein the wallboard is hammermilled through holes of a hammermill grate, the hole size being selected to produce a screenable mixture of pieces of paper and separated gypsum particles, which can then in turn be screened to segregate the pieces of paper from the gypsum particles. However, this method and apparatus have a number of disadvantages: 
     1. Inability to easily separate ferrous materials such as steel from gypsum board prior to hammermilling, resulting in safety and component wear hazards associated with ejection of shrapnel from the hammermill under high force and damage to the hammermill itself. 
     2. Inability to achieve relatively uniform feed to the hammermill resulting in: (a) the hammermill being plugged with excess gypsum material, thus resulting in poorer separation of gypsum core from the paper, and (b) poorer screening resulting in more paper in the gypsum product and more gypsum in the paper product. 
     3. Lack of a manual sorting station to supplement screen separation resulting in foreign objects, such as wood, concrete, plastics, aluminum, green waste, putrescible garbage, etc. in the end products and more wear and maintenance to the hammermill. 
     What is required is a new and improved method and apparatus for separating adhered paper from paper-covered gypsum board. Ideally, the method and apparatus should be able to separate and segregate a substantial amount of adhered paper from paper covered gypsum in a continuous and efficient manner, while minimizing wear and damage to the hammermill or other pulverizer and ensuring safety. 
     SUMMARY OF INVENTION 
     In accordance with a broad aspect of the method of the present invention there is provided a method of separating adhered paper from paper-covered gypsum board, the method comprising the steps of: 
     (a) Feeding wet and/or dry gypsum board into a feed hopper and onto a conveyor; 
     (b) Conveying the gypsum board past a magnet to remove ferrous materials prior to being fed into a hammermill or other type of pulverizer; 
     (c) Fracturing the gypsum board in a hammermill or other type of pulverizer; and 
     (d) Sieving pulverized gypsum board through at least one screen to segregate paper and gypsum particles. 
     This method can, if desired, be combined with one or more of the following optional performance enhancing steps: 
     (a) Prior to conveying the gypsum past the magnet, providing an area wherein non-gypsum debris such as plastic, insulation, wood, concrete, aluminum, green waste, garbage, etc. can be manually sorted and removed from the gypsum; 
     (b) After sieving pulverized gypsum board through the first screen, resieving the coarsely screened gypsum board through a finer screen to achieve improved gypsum/paper separation; and 
     (c) Conveying the coarsely sieved and/or finely sieved gypsum past one or more additional magnets to further purify the gypsum product of ferrous debris (e.g. screws, corner bead pieces, nails, etc.). 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     In Figures which illustrate non-limiting embodiments of the invention: 
     FIG. 1 is a perspective elevation view, partially cut-away, of a separation apparatus according to an embodiment of the present invention, and which implements the method of the present invention; 
     FIG. 2 is a perspective elevation view, partially cut-away, of a separation apparatus according to a first alternative embodiment of the invention, and which also implements the method of the present invention; 
     FIG. 3 is a perspective elevation view, partially cut-away, of a separation apparatus according to a second alternative embodiment of the invention, and which also implements the method of the present invention; 
     FIG. 4 is a perspective elevation view, partially cut-away, of a separation apparatus according to a third alternative embodiment of the invention, and which also implements the method of the present invention; 
     FIG. 5 is a perspective elevation view, partially cut-away, of a separation apparatus according to a fourth alternative embodiment of the invention, and which also implements the method of the present invention; 
     FIG. 6 is a perspective elevation view, partially cut-away, of a separation apparatus according to a fifth alternative embodiment of the invention, and which also implements the method of the present invention; 
     FIG. 7 is a perspective elevation view, partially cut-away, of a separation apparatus according to a sixth alternative embodiment of the invention, and which also implements the method of the present invention; 
     FIG. 8 is a perspective elevation view, partially cut-away, of a separation apparatus according to a seventh alternative embodiment of the invention, and which also implements the method of the present invention; and 
     FIG. 9 is a perspective elevation view, partially cut-away, of a separation apparatus according to an eighth alternative embodiment of the invention, and which also implements the method of the present invention. 
    
    
     DESCRIPTION 
     Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention may be practiced without these particulars. In other instances, well known elements have not been shown or described in detail to avoid unnecessarily obscuring the invention. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive, sense. 
     FIG. 1 illustrates a separation apparatus  10  embodying the present invention and which implements the method of the present invention. Separation apparatus  10  comprises a feed hopper  12  for receiving wet and/or dry gypsum, a conveyor  14  for conveying the gypsum from feed hopper  12  for pulverizing, a magnet  16  positioned over or proximate to conveyor  14  for automatically removing ferrous materials from the gypsum during normal operation of conveyor  14 , a pulverizer  18  for fracturing and breaking the gypsum, and a screen  20  for segregating said fractured and broken pieces of gypsum. Feed hopper  12  is preferably a steel hopper that allows for a large amount of gypsum to be fed in a controlled manner. Conveyor  14  is preferably a drag chain conveyor operated in conjunction with feed hopper  12  and equipped with a variable frequency drive that controls the rate at which conveyor  14  feeds gypsum into pulverizer  18 . By using a variable frequency drive, separation apparatus  10  can be configured to achieve relatively uniform feed of gypsum to pulverizer  18  and thereby: (a) reduce or eliminate clogging of pulverizer  18  with excessive gypsum, resulting in better separation of paper from gypsum; and (b) improve screening, resulting in less paper in the segregated gypsum material and less gypsum in the segregated paper material. 
     Conveyor  14  conveys gypsum under magnet  16 , or otherwise past magnet  16 , in order to automatically remove ferrous materials from the gypsum prior to the feeding of the gypsum into pulverizer  18 . By utilizing magnet  16  to automatically remove loose ferrous materials, such as nails, screws, and corner bead pieces, the invention reduces safety hazards associated with the ejection of shrapnel from pulverizer  18  under high force and reduces the likelihood of wear and damage to pulverizer  18  itself. Using a magnet to remove loose ferrous materials is also useful after pulverization to remove ferrous materials further loosened by the pulverization (as explained below), but the use of magnetic separation before pulverization is especially useful for the protection of both human operators and the equipment itself. 
     Magnetic separation according to the present invention is automatically accomplished without deactivating separation apparatus  10  or otherwise disrupting the flow of the process. Otherwise, separation apparatus  10  would need to be frequently deactivated in order to permit a human operator to remove ferrous waste, which would dramatically reduce gypsum separation output. This invention, on the other hand, allows for essentially uninterrupted operation of separation apparatus  10 , which, in turn, permits a variable frequency drive to be utilized to control conveyor  14  to achieve relatively uniform and uninterrupted feed of gypsum to pulverizer  18 . 
     In FIG. 1, pulverizer  18  is a pulverizer of conventional design such as a Maxigrind 500 pulverizer manufactured by CMI Corporation of Oklahoma City, Okla. Such a conventional pulverizer will work in accordance with the invention, although a hammermill is preferred (for the reasons set out above and as further detailed below). Screen  20  is positioned at the output of pulverizer  18  to segregate pieces of paper and gypsum particles output by pulverizer  18 . 
     In operation of separation apparatus  10 , wet and/or dry gypsum is fed into feed hopper  12  and then is dropped by feed hopper  12  onto conveyor  14 . Conveyor  14  then conveys the gypsum material under or otherwise past magnet  16  to automatically remove ferrous materials before the gypsum material enters pulverizer  18 . Pulverizer  18  fractures and breaks the gypsum material into smaller pieces that can be more easily screened and segregated. The fractured and broken gypsum material falls from the output of pulverizer  18  onto a screen  20  to segregate pieces of paper and gypsum particles. The pieces of paper tend to be larger than the gypsum particles. A screen size is selected that permits most gypsum particles to fall through screen  20  but that prevents most pieces of paper from similarly falling through. 
     FIG. 2 illustrates a separation apparatus  10 A that is identical to the separation apparatus  10  illustrated in FIG. 1, other than the fact that it further comprises additional optional performance enhancing techniques/components. Referring to FIG. 2, separation apparatus  10 A further comprises an optional manual pre-sorting section in the form of a presorting belt  22 , wherein non-gypsum debris can be manually sorted and removed from the gypsum prior to the gypsum passing under magnet  16  and being fed into pulverizer  18 . Also, separation apparatus  10 A further comprises an optional second screen  24  having smaller openings than screen  20  for finer screening and segregating. In particular, smaller pieces of paper and gypsum that fall through the relatively coarse screen  20  can be further screened and segregated by screen  24 . Separation apparatus  10 A also further comprises an optional second magnet  26  for the automatic removal of any remaining ferrous materials. 
     In operation of separation apparatus  10 A, wet and/or dry gypsum is fed into feed hopper  12  and then is dropped by feed hopper  12  onto conveyor  14 . Conveyor  14  then conveys the gypsum material to pressorting belt  22 , where non-gypsum material is manually sorted out and removed without stopping separation apparatus  10 A. The presorted gypsum material is then conveyed under or past magnet  16  to automatically remove ferrous materials before the gypsum material enters pulverizer  18 . Pulverizer  18  fractures and breaks the gypsum material into smaller pieces that can be more easily screened and segregated. The fractured and broken gypsum material falls from the output of pulverizer  18  onto a screen  20  to segregate pieces of paper and gypsum particles according to the method described above. Smaller pieces of paper and gypsum dust fall through screen  20  onto screen  24 , where the material is further segregated before being conveyed under second magnet  26  for the automatic removal of remaining ferrous materials. 
     FIG. 3 illustrates a separation apparatus  10 B that is identical to the separation apparatus  10  illustrated in FIG. 1, other than the fact that pulverizer  18  has been replaced with a hammermill  18 A. Hammermill  18 A is a hammermill pulverizer of conventional design, but is preferably a hammermill pulverizer similar to that described in U.S. Pat. No. 5,593,096 as producing exemplary results, namely, an H1100 Tub Grinder manufactured by Haybuster Manufacturing Inc. of Jamestown, N. Dak. A hammermill pulverizer is preferable over a conventional pulverizer such as pulverizer  18  illustrated in FIG. 1 because a hammermill pulverizer better processes wet as well as dry gypsum, resulting in a more effective separation of paper from the core of the gypsum board. In separation apparatus  10 B, hammermill  18 A comprises a lower grate having holes of about 2″ in diameter, and works well with its rotor driven at about 1750 rpm with a 60 HP motor (not shown). Otherwise, the structure and operation of separation apparatus  10 B are identical to those of separation apparatus  10 . 
     FIG. 4 illustrates a separation apparatus  10 C that is identical to the separation apparatus  10 A illustrated in FIG. 2, other than the fact that pulverizer  18  has been replaced with the hammermill  18 A described above in respect of FIG.  3 . Otherwise, the structure and operation of separation apparatus  10 C are identical to those of separation apparatus  10 A. 
     FIG. 5 illustrates a separation apparatus  10 D that is identical to the separation apparatus  10  illustrated in FIG. 1, other than the fact that the drag chain conveyor  14  has been replaced with a conventional feed conveyor  14 A. In practice, any type of conveyor can be used, each with its own advantages and disadvantages, which would be apparent to one skilled in the art of such conveyors. Otherwise, the structure and operation of separation apparatus  10 D are identical to those of separation apparatus  10 . 
     FIG. 6 illustrates a separation apparatus  10 E that is identical to the separation apparatus  10 D illustrated in FIG. 5, other than the fact that pulverizer  18  has been replaced with the hammermill  18 A described above in respect of FIG.  3 . Otherwise, the structure and operation of separation apparatus  10 C are identical to those of separation apparatus  10 D. 
     As can be seen from FIGS. 1 to  6 , different combinations of conveyors and pulverizers can be selected to suit any given set of parameters/requirements without departing from the scope of the invention. Indeed, the conveyor can be replaced with anything that effectively and efficiently moves the gypsum to pulverizer  18  or hammermill  18 A or pre-sorting belt  22 , as the case may be. For example, FIG. 7 illustrates a separation apparatus  10 F that is identical to the separation apparatus  10 A illustrated in FIG. 2, other than the fact that conveyor  14  has been replaced with an auger screw-feeder  14 B. Auger screw-feeder  14 B crushes the material as it is rotated along the screws, resulting in material that is more even in size and loosening embedded metal to make it easier for magnet  16  to remove. Even so, a drag chain conveyor as illustrated in FIG. 2 is preferable to an auger screw-feeder  14 B, since auger screw-feeder  14 B is more likely to cause undesirable shredding of the gypsum, resulting in excessive fluff. Otherwise, the structure and operation of separation apparatus  10 F are identical to those of separation apparatus  10 A. 
     FIG. 8 illustrates a separation apparatus  10 G that is identical to the separation apparatus  10 F illustrated in FIG. 7, other than the fact that pulverizer  18  has been replaced with the hammermill  18 A described above in respect of FIG.  3 . Otherwise, the structure and operation of separation apparatus  10 G are identical to those of separation apparatus  10 F. 
     FIG. 9 illustrates a separation apparatus  10 H that is identical to the separation apparatus  10 C illustrated in FIG. 4, but with a further improvement. In separation apparatus  10 H, magnet  16  has a self-cleaning belt  28 . Self-cleaning belt  28  is essentially a conveyor belt surrounding magnet  16 , and is preferably positioned to move perpendicular to the path of the gypsum. In operation, as gypsum passes under or proximate to magnet  16 , ferrous materials  30  are attracted from the passing gypsum by magnet  16  and held to the rotating self-cleaning belt  28  until they pass from under magnet  16 , at which point, ferrous materials  30  are dropped from self-cleaning belt  28  to a suitable place away from the passing gypsum. Self-cleaning belt  28  typically operates from a power source separate from magnet  16 . Self-cleaning belt  28  is operated at a speed fast enough to prevent excessive ferrous materials accumulating on self-cleaning belt  28 , but slow enough to allow magnet  16  to attract ferrous materials adequately and drop such ferrous materials from the end of the self-cleaning belt  28 . A speed of 15 r.p.m., for example, may be suitable. The use of a self-cleaning belt  28  prevents excessive accumulation of ferrous materials on magnet  16 , and permits continuous operation of separation apparatus  10 H without interruption even to clean magnet  16 . Similar to separation apparatus  10 C in FIG. 4, separation apparatus  10 H has a second magnet  26  for post-pulverization magnetic separation. In separation apparatus  10 H, magnet  26  has a self-cleaning belt  32  identical or similar to the self-cleaning belt  28  of magnet  16 . Self-cleaning belt  32  operates in the same manner self-cleaning belt  28 , although ferrous materials  34  removed by magnet  26  and self-cleaning belt  32  would obviously be finer than the ferrous materials  30  removed by magnet  16  and self-cleaning belt  28 . Magnets having a self-cleaning magnetic belt are known in the art, and include Master Magnets Ltd.&#39;s Model No. MASTERMAG 10 PCB 5 K EL, although other self-cleaning magnets, such as those described at the Internet website of Global Equipment Marketing Inc.&#39;s Magnetic Division at www.globalmagnetics. com, would also work. Other than self-cleaning belts  28 ,  32 , the structure and operation of separation apparatus  10 H are identical to those of separation apparatus  10 C. 
     Separation apparatus  10 H is a particularly preferred embodiment of the present invention, taking the best elements of separation apparatuses  10 ,  10 A,  10 B,  10 C,  10 D,  10 E,  10 F, and  10 G, along with the further improvement of the self-cleaning belts  28 ,  32 . The use of a drag chain conveyor  14  and a hammermill  18 A reduce undesirable fluff, the use of magnets  16 ,  26  both before and after pulverization automatically reduce metal contamination and safety hazards without disrupting the continuous operation of separation apparatus  10 H (especially when operated in conjunction with self-cleaning belts  28 ,  32 ), and the pre-sorting belt  22  and multiple screens  20 ,  24  permit finer screening and segregation. 
     As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.