Abstract:
There is provided an apparatus for crushing anodes, including a chamber for receiving the anodes. At least one movable wall is received in the chamber. The wall has a plurality of cutting devices associated therewith. The wall is able to move in a first direction for crushing the anodes and in a second direction away from the anodes. An apparatus is provided for applying pressure to the wall for moving the wall in the first direction. At least one pressure sensor associated with the apparatus for applying the pressure is provided. When a predetermined pressure level is reached, the wall ceases moving in the first direction and begins moving in the second direction.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This is a U.S. non-provisional application relating to and claiming the benefit of U.S. Provisional Patent Application Ser. No. 60/964,166, filed Aug. 8, 2007. The entire disclosure set forth in that provisional patent application is hereby incorporated herein by reference. 
    
    
     BACKGROUND 
     The present invention relates to an apparatus and method for recovering carbon from anodes and particularly for recovering carbon from anodes or remnants of anodes of the type used in the production of aluminum. When used herein, the term “anodes” means complete anodes, remnants of anodes and portions of anodes. Aluminum producers use large anodes in connection with the reduction of aluminum oxide to aluminum metal. These anodes are primarily made of carbon with metal conductors embedded therein. After a certain time of use in connection with the production of aluminum, these carbon anodes become less efficient and must be replaced. However, there is a substantial market for the carbon in these spent anodes. In order to provide a useful product, these carbon anodes must be crushed into smaller pieces. An example of an apparatus for salvaging carbon from spent anodes is disclosed in U.S. Pat. No. 3,708,128 issued to Limpinsel et al. 
     One of the problems associated with many prior art anode crushers is that the crusher can become damaged and worn because of impact with the metal components embedded in the carbon or impact with so-called hard anodes which were over-baked during their production. In addition, some prior art anode crushers consume a great deal of energy during operation. It is desirable for an anode crusher to operate at minimal velocity to minimize wear and tear and to prevent substantial dusting and to provide minimal generation of fines. It is also desirable to be able to control the pressure to prevent the anode crusher from attempting to crush items such as metal or hard anodes which can further damage the crusher. 
     SUMMARY OF THE INVENTION 
     In accordance with one form of this invention, there is provided an apparatus for crushing anodes, including a chamber for receiving anodes. At least one movable wall is received in the chamber. The wall has a plurality of cutting devices associated therewith. The wall is able to move in a first direction for crushing the anodes received in the chamber and in a second direction away from the anodes. An apparatus is provided for applying pressure to the wall for moving the wall in the first direction. At least one pressure sensor associated with the apparatus for applying pressure is provided. When a predetermined pressure level is exceeded, the wall ceases moving in the first direction and begins moving in the second direction. 
     In accordance with another form of this invention, there is provided a method for crushing anodes. The method includes placing anodes in a chamber having at least one movable wall and a bottom grate, applying pressure to the wall thereby moving the wall toward the anodes, crushing the anodes with cutting devices which are attached to the wall, sensing a pressure above a predetermined level, and moving the wall away from the anodes in response to the pressure being above the predetermined level. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an anode crusher apparatus in accordance with one form of this invention. 
         FIG. 2  is a top view of the apparatus of  FIG. 1 . 
         FIG. 3  is a side elevational view of the apparatus of  FIG. 1 . 
         FIG. 4  is an end elevational view of the apparatus of  FIG. 1 . 
         FIG. 5  is an end view of a portion of the apparatus of  FIG. 1  with an end wall and a movable wall removed. 
         FIG. 6  shows a piece of anode material which may be crushed utilizing the apparatus of  FIG. 1 . 
         FIG. 7  is a schematic showing the hydraulic circuit used to operate the apparatus of  FIG. 1 . 
         FIG. 8  is a side elevational view showing two of the apparatus of  FIG. 1  set up for continuous operation. 
         FIG. 9  is a front elevational view of one of the apparatus of  FIG. 8 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now more particularly to  FIGS. 1-5 , anode crushing apparatus  10  includes a rectangular chamber  12  which is open at the top to accept anodes in the form of large mineral lumps up to 60 inches in width, depth, and height in size with the objective of size reduction (crushing) of the mineral lumps to a smaller size for (A) a specific market need or (B) as a feed stock for secondary crushing by alternative means of crushing. An example of such a mineral lump is partial anode  14  shown in  FIG. 6 . In part, the crushing apparatus  10  is unique in that two major operational features of the apparatus are controlled for the specific material to be crushed. The first major operational feature relates to the pressure of the system when contacting the mineral lumps to accomplish the size reduction. The second major operational feature relates to the speed of travel of the two moving walls in the chamber, which will be described below. 
     The anodes or minerals  14  are placed into the chamber  12  between a first movable wall  16  within chamber  12  on the right side of chamber  12  and a second movable wall  18  within chamber  12  on the left side of chamber  12 . The movable walls are propelled towards each other using hydraulic cylinders  20  and  22  that function at an adjustable pressure (pounds per square inch) based upon the compressive strength of the mineral to break. The hydraulic cylinders  20  and  22  apply pressure or force to movable walls  16  and  18 . As used herein in reference to moving the movable walls  16  and  18 , the term “pressure” means force and pressure. The pressure is set to crush the specific mineral and at the same time not crush hard overbaked anode material or foreign objects such as ferrous and nonferrous metal that may be attached to or a part of the feed material coming into the apparatus. For example,  FIG. 6  shows metal piece  24  embedded in carbon material  26 . The movable walls  16  and  18  have cutting devices  28  attached to them that are of staggered lengths based upon the mounting arrangement of the cutting devices  28  on each movable wall. The staggered cutting devices allow more pounds per square inch of pressure to be exerted on the mineral lump or lumps in chamber  12  at any given time to allow less contact area on the lump for a given force which translates to a higher pressure on the mineral. The cutting devices  30  that are recessed behind the most forward cutting devices  32  come in contact with the lump after the initial contact of the most forward cutting devices  32  which are followed by a third and fourth tier of cutting devices also to optimize the transfer of pressure into the mineral lump for a given force. The pressure threshold is established to crush the target mineral or minerals and not to crush harder or extraneous material such as metal or hard anode material. Hydraulic pressure increases when the cutting devices  28  come in contact with hard or metal material. 
     The velocity of a moving wall is a function of the flow rate of hydraulic fluid through the cylinders  20  and  22  that is also adjustable. The more flow through the hydraulic cylinders, the higher the impact velocity of the moving walls  16  and  18  as they contact the anode  14 . This allows infinite control of impact which along with the pressure is another key element of anode size reduction. As will be explained in more detail below, a sensor or sensors associated with the hydraulic cylinders  20  and  22  monitor pressure and flow in the crusher  10 . When a pressure is sensed at a level above the point necessary to break the anode, the hydraulic system sends hydraulic fluid back to a reservoir from a power pack that provides energy into the crusher  10 . As will be noted below, this pressure is adjustable by means of a bypass valve diverting hydraulic fluid. The movable walls  16  and  18  continue to move towards each other until this pressure is reached and when the maximum desired pressure is reached, the walls are retracted via a joy stick control to allow the material crushed in that cycle to drop down through a grate  34  in the bottom  36  of the chamber  12  into a collection area or transfer device such as a conveyor. When the walls retract (typically 6 to 12 inches), the pressure drops below the desired set point and the process can start again on the remaining anodes in the chamber until the walls  16  and  18  effectively meet at which time the walls retract to the fully open position to accept more feed material. Two items that determine the size of the crushed material are the size of the apertures  38  of the grate  34  and the spacing of the cutting devices  28 . The closer the spacing of the cutting devices  28  and the smaller the apertures  38  in the grate  34 , the finer the product coming from the crusher  10 . These dimensions can be varied based upon size objectives of the material discharged. 
     Crusher  10 , as shown in  FIG. 1 , includes guides  40  and  42  having anti-wear strips. Guides  40  and  42  are located on each side of the center section of chamber  12  in the travel area of movable walls  16  and  18  and are adjacent to the tops of movable walls  16  and  18 . The guides  40  and  42  are firmly attached to the chamber  12  for the purpose of holding the movable walls  16  and  18  down during travel that otherwise would potentially raise up out of the crushing zone above the grate  34 . This allows the crusher  10  to maintain the desired dimensional tolerances between the movable walls  16  and  18  and the grate  34 . 
     The method and apparatus as described above is commonly termed a “batch” system in that there is a period of time when no size reduction is taking place, specifically while the crusher  10  is being fed before the process described in detail above takes place. A second identical unit  44 , as shown in  FIGS. 8 and 9 , may be incorporated into this invention whereby one of the crushers  10  is performing the crushing operation while the second crusher  44  is being fed by a separate loading apparatus that could include any material transfer machine capable of elevating the feed minerals and dropping them into the chamber of the second crusher. A single power source no larger than the power source necessary to operate a single crusher alternately powers one, then the other unit to allow a “continuous” process as opposed to the “batch” process noted above. 
     Control of the two crushers  10  and  44  is accomplished by an attached push button control station which allows hydraulic fluid to be directed to the active apparatus while the alternate apparatus is on standby. When the “stop” button is pushed on either of the two devices, the fluid flow is transferred via valve to the apparatus which has the “start” button pushed, typically the alternate unit that has been loaded with feed material while the other apparatus finishes processing material in its chamber. The pressure relief system, flow measurement and control system, and the method of utilizing alternate chambers from a single power unit are all features of this invention. 
     By way of example and by no means intending to limit the applicability of the invention to a single mineral, the invention is utilized in crushing spent carbon anodes, such as anode piece  14  shown in  FIG. 6 , after an aluminum plant has used the carbon lumps in its manufacturing process. The spent anodes require size reduction for various alternative market needs as well as a need to isolate and segregate hard anodes and metals that are attached to or within the carbon lumps including but not limited to copper, iron, aluminum, and manganese all of which are separated post crushing by various means to make the recycled carbon as viable for other uses as possible. The invention has applications in other mineral industries as well and is notably effective due to the extremely low velocity compared to other crushing technologies, the low wear on the cutting devices and other mechanical components, the low horsepower required per ton per hour fed into the crusher, and the overall effective cost of operation factoring in all financial elements of a dual crusher box assemblies and common power pack component. 
       FIG. 7  shows a hydraulic circuit which controls the operation of cylinders  20  and  22 . Hydraulic fluid from reservoir  46  is pumped through pump  48  and through flow meter  50 . The velocity of the hydraulic fluid through flow meter  50  is preset, preferably at fifty grams per meter (50 g/m) which is a very low velocity for the anode crusher industry. Thus, the velocity of the hydraulic fluid can not exceed a preset speed. The hydraulic fluid from the flow meter travels through VG35 valve  52 . Valve  52  includes a pressure sensor  54  and a diverter. If the hydraulic pressure sensed by sensor  54  exceeds a predetermined amount, which should be set to the maximum amount required to crush a specific material such as soft carbon in a carbon anode, a warning light goes off. By using joy stick  56 , an operator can reverse the flow of the hydraulic fluid to cylinders  20  and  22 . That is, during normal operation hydraulic fluid will flow through hydraulic line  58  from valve  52  and into the normal operating sides  60  and  62  of cylinders of  20  and  22 . However, when the operator reverses the flow by moving joy stick  56 , hydraulic fluid will flow through hydraulic lines  64  through flow divider  66  and into the opposite sides  68  and  70  of cylinders  20  and  22  so that walls  16  and  18  to reverse direction, thereby ceasing the crushing operation. Typically, a high pressure will occur when some of the cutting devices  28  come into contact with a hard anode or uncrushable metal such as metal  24  shown in  FIG. 6 . 
       FIG. 8  shows the simultaneous use of two (2) crushers  10  and  44  so as to convert this assembly from a batch process to a continuous process. As stated previously, crusher  10  is loaded with anode material while crusher  44  is doing a crushing operation. Once the crushing operation in crusher  44  has been completed, crusher  10  begins its crushing operation and crusher  44  is loaded. The materials which fall from the bottom of crushers  10  and  44  drop to conveyor  72 . 
     The apparatus and method of this invention provides minimal velocity compared to most prior art crushers, which minimizes wear and associated operating costs. Pressure is controllable based on the material to be crushed, thereby crushing the desired material and not crushing items such as commingled metal or hard anode material. The invention provides for less power consumption for a given throughput than most alternative crushing apparatus. Low velocity translates to low dust and to minimal fines generation, which is universally desired in crushing minerals. 
     From the foregoing description of the preferred embodiments of the invention, it will be apparent that many modifications may be made therein. It should be understood, however, that each of these embodiments of the invention are exemplifications of the invention only and that the invention is not limited thereto. It is to be understood, therefore, that it is intended in the appended claims to cover all modifications as fall within the true spirit and scope of the invention.