Abstract:
The invention resides in a de-aeration device including at least one de-aeration chamber for locating a slurry; at least one slurry inlet connected to the de-aeration chamber to allow the slurry to pass into the de-aeration chamber; at least one slurry outlet to allow slurry to pass out of the de-aeration chamber; and at least one de-aeration face for collecting and transporting air from the slurry.

Description:
FIELD OF THE INVENTION 
     This invention relates to a de-aeration device. In particular, the invention relates to a de-aeration device for de-aerating slurries particularly used in mineral processing. 
     BACKGROUND OF THE INVENTION 
     The classification of particles according to their size and/or weight is often used in mineral processing. In order to classify these particles it is common to locate the particles in a solution to form a slurry. This slurry is then passed through various types of equipment in order to separate the particles into different sizes and/or densities. 
     A problem using a slurry to classify particles is that air is often formed or entrained within the slurry as the slurry moves through various types of processing equipment in a processing plant. Air bubbles formed within the slurry can cause problems with the movement of the slurry through a processing plant. For example, aeration of the slurry can reduce the efficiency of a pump used for pumping of the slurry through the processing plant. Further, aeration of the slurry can cause cavitation and premature wear of the impellor of a pump. This can lead to higher maintenance costs and premature failure of the pump. 
     Air bubbles formed within the slurry can also cause complications when trying to classify the particles using classifying equipment. Classifying equipment typically relies on movement of the particles within the slurry based on the size and/or weight of the particles. Air bubbles located within the slurry can effect the desired movement of the particles within the slurry. This is particularly evident in floatation processes as heavy particles can often become attached to air bubbles allowing them to pass upwardly through the classifying equipment when it is desirable for the heavy particles to remain at a bottom of the classifying equipment. 
     OBJECT OF THE INVENTION 
     It is an object of the invention to overcome or alleviate one or more of the disadvantages of the above disadvantages or provide the consumer with a useful or commercial choice. 
     SUMMARY OF THE INVENTION 
     In one form, although not necessarily the only or broadest form, the invention resides in a de-aeration device including:
         at least one de-aeration chamber for locating a slurry;   at least one slurry inlet connected to the de-aeration chamber to allow the slurry to pass into the de-aeration chamber;   at least one slurry outlet to allow slurry to pass out of the de-aeration chamber; and   at least one de-aeration face for collecting and transporting air from the slurry.       

     The slurry that is classified may be any mineralised slurry. Normally the slurry is a coal slurry. 
     The de-aeration device may form part of a classifier or may be stand alone piece of equipment. 
     The de-aeration device may include an air outlet to allow air to be passed out of the de-aeration chamber. 
     The de-aeration device may also include a screen located adjacent the slurry outlet to filter oversize particles from the slurry before the slurry passes through the slurry outlet. 
     The de-aeration device may include may include a hatch to access and/or remove the screen. 
     In yet another form, the invention resides in a classifier for classifying particles, the classifier including:
         a de-aeration device including:
           at least one de-aeration chamber for locating a slurry;   at least one slurry inlet connect to the de-aeration chamber to allow the slurry to pass into the de-aeration chamber;   at least one slurry outlet to allow slurry to pass out of the de-aeration chamber; and   at least one de-aeration face for collecting and transporting air from the slurry; and   
           a classification device used to classify the slurry after it passes out of the de-aeration device.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An embodiment of the invention will be described within reference to the accompanying drawings in which: 
         FIG. 1  shows a perspective view of a classification apparatus which includes de-aeration devices according to an embodiment of the invention; 
         FIG. 2  shows a front view of the classification apparatus according to  FIG. 1 ; 
         FIG. 3  shows a left side view of the classification apparatus according to  FIG. 1 ; 
         FIG. 4  shows a right side view the classification apparatus according to  FIG. 1 ; 
         FIG. 5  shows a top view of view of the classification apparatus according to  FIG. 1 ; 
         FIG. 6  shows a lateral sectional view of the classification apparatus along the line G-G shown in  FIG. 5 ; and 
         FIG. 7  shows a longitudinal perspective sectional view of the classification apparatus according to  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1 to 7  show a classifier  10  used to separate coal particles, which are located in a coal slurry, on the basis of both size and weight. The classifier  10  includes a housing  20 , a series of plate arrays  30 , a series of launders  40 , a series of de-aeration devices  50  and a reservoir  60 . 
     The housing  20  is used to house the plate arrays  30 , launders  40 , de-aeration devices  50  and reservoir  60 . It should be appreciated that the housing  20  may be shaped and sized differently according to design requirements. It should also be appreciated that a top of the housing  20  is not shown in the FIGS in order to more clearly shown the plate arrays  30  and launders  40 . 
     There are six sets of plate arrays  30 . However, it should be appreciated that the number plate arrays  30  may be varied depending on design criteria. Each plate array  30  is made up of a set of spaced apart, parallel inclined plates  31 . For clarity, only a minimal number of plates  31  have been illustrated within each plate array  30 . It should be appreciated that the number of plates  31 , the size of the plates  31 , the angle of inclination of the plates  31  and the spacing of the plates  31  can again be varied according to design criteria. Longitudinal members  32  are located on sides of respective sets of plates  30 . 
     Three launders  40  are used to catch the particles located with coal slurry after the coal slurry has passed through the plate arrays  30 . Launders  40  are spaced between respective plate arrays  30 . For clarity, only a single launder has been illustrated. However, a person skilled in the art would appreciate where the additional launders  40  are located. Further, a person skilled in the art would appreciate number and type of launders  40  may be varied according to design criteria. Each launder  40  is formed from a two side walls  41 , an inclined base  42  and a series of cross-members  43 . 
     A collector  70  is formed at the end of the launders  40 . The collector  70  is located within the housing  20  to collect the coal slurry once it has passed through the launders  40 . The collector  70  is formed by a pair inclined members  71  that are angled toward each other to form a V-shaped valley. A top outlet pipe  72  is connected to the collector  70  at the bottom of the V-shaped valley to transport the slurry for further processing. 
     There are three de-aeration devices  50  that are used to de-aerate the coal slurry so that the classifier  10  can classify the coal slurry more effectively. Each de-aeration device  50  is located below a respective launder  40  and between respective plate arrays  30 . It would be appreciated by a person skilled in the art that the number of de-aeration devices is typically the same as the number of launders  40 . However, it would also be appreciated that this need not be the case. Each de-aeration device  50  is formed from a slurry inlet  510 , a slurry outlet  520 , an air outlet  530  and a de-aeration chamber  540 . 
     The slurry inlet  510  is connected to the de-aeration chamber  540  via an inlet pipe  511  to allow the coal slurry to enter into the de-aeration chamber  540 . 
     The slurry outlet  520  is located adjacent a bottom of the de-aeration chamber  540  to allow the coal slurry to pass into the reservoir  60 . 
     A screen  550  is located adjacent the slurry outlet  520  and covers the slurry outlet  520 . The screen  550  is used to assist in preventing oversize particles from being passed into the reservoir  60 . The screen  550  is made of wedge wire which extends longitudinally. However, it should be appreciated that the screen  550  may be made from a variety of other materials that a person skilled in the art would appreciate. 
     Cleaning hatches  560  are located adjacent an end of the screens to allow access to the screens. The screens  550  are removable through respective cleaning hatches in order to clean the screens  550 . 
     Oversize particle outlets  570  are located at the opposite end of the screens to the cleaning hatches. The oversize particle outlets  570  are used to remove oversized particles from a bottom of the de-aeration chamber. An over size particle valve  571  may be opened to remove the over size particles through the oversize particle outlet  570 . 
     A top of each of the de-aeration chambers  50  are inclined and are formed by the inclined bases  42  of the respective launders  40 . The bottom of the inclined bases form a inclined de-aeration face  580 . An air outlet  530  is located adjacent an end of the inclined base  42  (and accordingly the de-aeration faces  580 ) at the top of the de-aeration chamber  50 . An air pipe  531  is connected to the air outlet  530 . It should be appreciated that the tops of the de-aeration chambers  50  need not be formed from the inclined bases of the respective launders  40  and may be formed irrespective of the launders  40 . That is, the de-aeration faces  580  may be formed by other means. 
     The reservoir  60  is formed in the bottom of the housing  20  and is used to receive the coal slurry after it passes through the de-aeration devices  50 . Accordingly, the reservoir  60  is located below the de-aeration chambers  510 . The reservoir  60  is also located below the plate arrays  30  and is used to deliver the coal slurry to the plate arrays  30 . The longitudinal members  32  of which abut the plates  31  extend into the reservoir  60 . 
     In use, the coal slurry is passed through a central pipe  512  which divides into the three inlet pipes  511 . The coal slurry is passed through the slurry inlets  510  into respective de-aeration chambers  540 . The coal slurry then passes through respective screens  550  which remove oversize particles from the slurry. The slurry then passes out of the slurry outlet  520  and into the reservoir  60  located at the bottom of the housing  20 . The slurry then passes upwardly through the plate arrays  30  where particles located within the coal slurry are sorted according to size and weight. The heavy and large particles pass into the bottom of the reservoir  60  where they are removed using a reservoir  60  outlet (not shown). The lighter and smaller particles are able to pass through the plates  31  of the plate arrays  30  where they pass into launders  40 , into the collector  70  and out of the top outlet pipe  72 . 
     When the coal slurry is located within the de-aeration chambers  540 , air bubbles located within the coal slurry pass upwardly through the coal slurry. The air bubbles move upwardly until they contact respective inclined de-aeration faces  580  which are formed by the inclined bases  42  of the respective launders  40 . The air located within the bubbles travels along the de-aeration faces  580  due to the inclination of the de-aeration faces  580  until the air passes through the air outlets  530  and into the air pipes  531 . The air is then vented back into the launders  40 . However, the air may be vented into the atmosphere. 
     The removal of air from the slurry provides a number of benefits including a better separation of the particles when the slurry moves through the plate arrays  30  and a likely increased throughput. 
     It should be appreciated that various other changes and modifications may be made to the embodiment described without departing from the spirit or scope of the invention.