Abstract:
A process and system for recovering fine coal having a size at or below 400 mesh. The process and system includes a series of cyclone separators, vibratory separators, centrifuges and a flow path to clean, recover and dewater fine coal having a nominal size of 3 mm down to 400 mesh or below. The process and system includes the use of commercially available components arranged in a novel manner to efficiently recover fine coal for use in various energy supplying systems.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention generally relates to a process of recovering fine coal and more particularly to a process which enables recovery of fine coal having a size at or below 400 mesh. The process includes a series of cyclone separators, vibratory separators, centrifuges and a flow path to clean, recover and dewater fine coal having a nominal size of 3mm down to 400 mesh or below. The process includes the use of commercially available components arranged to efficiently recover fine coal for use in various energy supplying systems.  
           [0003]    2. Description of the Prior Art  
           [0004]    Prior art in this field of endeavor utilizes various types of separators to separate fine coal from contaminants which utilizes cyclones, vibratory separators and centrifuges by which fine coal can be cleaned and recovered for use in various energy producing systems. However, the prior art recovery systems for fine coal do not include the specific interrelationships between the components of the recovery process as utilized in the present invention.  
         SUMMARY OF THE INVENTION  
         [0005]    The process for recovering fine coal of the present invention includes a raw coal sump which provides a supply of raw coal, contaminants and a liquid, such as water, to form a slurry which is pumped into a bank of cyclones such as water only cyclones. The underflow from the water only cyclones discharges to a column cell sump and the overflow from the water only cyclones is discharged to a classifying cyclone sump. The material in the classifying cyclone sump is pumped to a bank of classifying cyclones for sizing.  
           [0006]    The classifying cyclone underflow, clean coal, is deposited onto high frequency vibrating screens which provides initial dewatering of the clean coal. The classifying cyclone overflow also discharges to the column cell sump. The material in the column cell sump which includes the overflow from the water only cyclones and the classifying cyclones is pumped to column flotation cells for cleaning.  
           [0007]    The float from the column flotation cells, clean coal, is discharged to a clarifying cyclone sump and the sink, or rejects, from the column flotation cells is discharged to waste. The material in the clarifying cyclone sump is pumped to clarifying cyclones to remove below 400 mesh material and the overflow from the clarifying cyclones, over 400 mesh, is discharged to waste.  
           [0008]    The clarifying cyclones discharge underflow onto the bed of material on the high frequency vibrating screens formed by the material discharged onto the vibrating screens from the classifying cyclone underflow. The initial bed formed by the classifying cyclone underflow material will trap the material discharged onto the bed from the clarifying cyclones underflow.  
           [0009]    Underflow from the high frequency vibrating screens is discharged to the clarifying cyclone sump and is recycled through the system and the overflow from the high frequency vibrating screens is discharged to modified centrifuges for further dewatering. The effluent from the centrifuges is discharged to the clarifying cyclone sump and is recycled through the system and the dewatered clean fine coal product from the centrifuges is discharged to a conveyor and stockpiled as finished product.  
           [0010]    Accordingly, an object of the present invention is to provide a process for recovering fine coal utilizing a serial arrangement of water only cyclones, classifying cyclones, clarifying cyclones, vibrating screens and centrifuges for depositing cleaned fine coal in a stockpile for subsequent use and discharging contaminants or the like above 400 mesh size from the clarifying cyclones and column flotation cells to waste. The underflow from the vibrators and the effluent from the centrifuges is recycled through the system by discharge into a clarifying cyclone sump. The clarifying cyclone sump also receives material from the column flotation cells. The column float cells discharges contaminant material to waste and the separated material is discharged into the clarifying cyclone sump for recycling through the system.  
           [0011]    Another object of the invention is to provide a fine coal recovering process which enable efficient recovery of fine coal at or below 400 mesh in size which includes a series of cyclone separators, a vibrating screen separator and a centrifuge dewatering device to produce cleaned, dewatered fine coal to a stockpile or other storage area combined with a column cell arrangement and a flow path which enables recycling of a portion of the material which passes through the cyclones, vibrating separator and centrifuge back through the system for more effective complete separation of fine coal from contaminants that are discharged to waste. 
       
    
    
     DESCRIPTION OF THE DRAWING  
       [0012]    The figure is a schematic diagram illustrating the components of the process and the flow path of material through the components resulting in recovery of dewatered fine coal at or below 400 mesh and discharge of contaminants to waste. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0013]    Although only one preferred embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawing. The invention is capable of other embodiments and of being practiced or carried out in various ways. Also, in describing the preferred embodiment, specific terminology will be resorted to for the sake of clarity. It is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose.  
         [0014]    The drawing schematically illustrates the process and system for recovering fine coal in accordance with the present invention that is generally designated by reference numeral  10 .  
         [0015]    Raw coal with contaminants in a liquid slurry is deposited into a raw coal sump  12  having a pump  14  having an intake communicated with the raw coal sump  12  and discharging through conduit  16  to a bank of water only cyclones  18 . The water only cyclones are commercially available products and preferably have a diameter ranging between 8 to 15 inches. The water only cyclones discharge their underflow to a column cell sump  20  through flow line  22  and discharges the overflow (cleaned coal) to a classifying sump  24  through flow line  26 . A pump  28  having an intake communicating with the classifying cyclone sump  24  pumps the overflow from the water only cyclones  18  from the classifying cyclone sump  24  to a bank of classifying cyclones  30  through flow line  32 . The classifying cyclones  30  size the material, generally at approximately 325 mesh size and discharges the underflow, cleaned coal, onto a high frequency vibrating screen  34  through flow line  36 . Overflow from the classifying cyclones  30  is discharged to the column cell sump  20  through flow line  38 .  
         [0016]    Pump  40  has an intake in communication with the column cell sump  20  and discharges material into column flotation cells  42  for cleaning through flow line  44 . The float from column flotation cells  42 , clean coal, is discharged to a clarifying cyclone sump  46  through flow line  48  and the sink material from the column flotation cells  42  is discharged to a waste line  50  through flow line  52 . Pump  54  has an intake in communication with clarifying cyclone sump  46  and discharges material to clarifying cyclones  56  through flow line  58 .  
         [0017]    The clarifying cyclones  56  are of smaller diameter than the classifying cyclones  30  and preferably are 4 to 5 inch diameter cyclones to remove 400 mesh material as overflow which discharges to waste through flow line  50 . Underflow from the clarifying cyclones  56  discharge onto the high frequency vibrator screens  34  through flow line  60 . The underflow from clarifying cyclones  56  is discharged onto a bed of material on the vibrating screens  34  which has been created from the underflow from the classifying cyclones  30  which is initially deposited on the high frequency vibrator screens  34 . The initial bed of underflow material from classifying cyclones  30  traps or retains the clarifying cyclones  56  underflow material. The high frequency vibrator screens  34  discharge an underflow to the clarifying cyclone sump  46  through a flow line  62  for recycling through the system. The overflow, clean initially dewatered fine coal, is discharged from the vibrating screens  34  to modified centrifuges  64  through flow line  66 . Effluent from the centrifuges  64  is discharged into flow line  62  through flow line  68  and into the clarifying cyclone sump  46  for recycling through the system.  
         [0018]    The cleaned dewatered fine coal is discharged from the centrifuges  64  onto a clean coal conveyor  70  through a flow path  72 . The conveyor  70  discharges the cleaned, dewatered fine coal onto a stockpile or other storage area  74  as a finished product. The finished product of the process of the present invention may be utilized from the stockpile  74  wherever desired to produce energy. The fine coal which has been recovered and dewatered and stored in the stockpile has a nominal top size of 3 mm down to 400 mesh (about 0.038 mm) or below. The specific arrangement of the cyclones, sumps, pumps and column flotation cells combined with high vibrating screens and modified centrifuges efficiently produces cleaned, dewatered coal for various purposes and discharges waste material for disposal.  
         [0019]    The capability of recycling the float material from the column float cells, the underflow from the high frequency vibrating screens and the effluent from the centrifuges provides an arrangement for effectively recovering a larger percentage of fine coal from the raw coal sump  12  which supplies raw coal to the water only cyclones which discharges overflow material into the classifying cyclone sump and underflow to the column cell sump. Overflow material from the water only cyclones is supplied to the classifying cyclones which discharge underflow, clean coal, to the vibrating screens for initial dewatering with the overflow from the classifying cyclones also discharging into the column cell sump for passage through the column flotations cells. The float material from the column flotation cells is deposited into the clarifying cyclone sump along with the high frequency vibrating screens underflow and effluent from the modified centrifuges. The material in the clarifying cyclone sump is pumped to the clarifying cyclones from which the overflow is discharged to waste and the underflow is deposited onto or piggybacked onto the bed of classifying cyclone underflow material which traps the underflow from the clarifying cyclones thus enabling the float from the column float cells, the underflow from the high frequency vibrating screens and the effluent from the centrifuges to be recycled through the clarifying cyclones for more complete separation of usable fine coal from the raw coal supply provided in the raw coal sump  12 .  
         [0020]    The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and, accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.