Abstract:
A reactor is provided for converting organic material to charcoal, with the reactor having a furnace and a retort extending through the furnace. The retort has an auger extending therethrough, with the auger having a flight with gaps therein. Members project inwardly from the walls of the retort at the gaps in the flight to unplug blockages in the retort. A gas collection system is provided which has a branched portion having two or more venting tubes, each with valves so that each may be shut off independently to allow to off-line cleaning without requiring shutdown of the system. A method for converting organic material may be practised by introducing combustible materials into the reactor.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to apparatus and methods for producing charcoal in a continuous manner. In particular, the invention relates to apparatus and methods in which organic material is advanced by an auger through one or more retort tubes. The organic material is converted to charcoal by anaerobic heating in the retort tube.  
       BACKGROUND OF THE INVENTION  
       [0002]     It is known that charcoal may be produced by moving organic material through retorts, or heated anaerobic vessels. For example, Canadian Patent Application No. 2,110,282 relates to a method of treating biomass material wherein the material is carried through a heated casing by an auger which runs the entire length of the heated casing.  
         [0003]     Canadian Patent Application No. 2,140,898 discloses an apparatus that allows thermal dimensional changes of metal parts in a retort mechanism which incorporates heating and cooling stages and comprises a retort auger that extends the entire length of the retort.  
         [0004]     Canadian Patent No. 2,242,279 discloses an apparatus for continuous charcoal production comprising a heated tubular retort with a screw element extending through the retort. The flight of the screw element is separated into sections by gaps coincident with gas vents penetrating the retort.  
         [0005]     Japanese Patent Document 58-501912 discloses a method for manufacturing carbonised briquettes by introducing vegetable matter into a heated retort. The heated retort incorporates a screw to advance material through the retort.  
         [0006]     Australian Patent Document 90 50613 discloses an apparatus for use in the production of charcoal comprising a hollow retort shell containing an auger for advancing material through the shell.  
         [0007]     A significant problem with prior systems is that organic material often adopts a viscous liquid or semi-solid state at a certain stage during the conversion to charcoal. Tar and creosote are typical examples of such partially converted organic material. These materials are sticky and often form plugs within the retort, often where the retort is initially exposed to heat. Plugs impede the steady feed-through of material and in some instances can completely block the advance of organic material. Removing plugs can be costly, and may require shutting down the system and disrupting otherwise continuous charcoal production. Plugs can also prevent pyrolysis gases from properly venting from retorts. Gas condensers to which pyrolysis gases are vented may also become congested with partially converted organic material.  
         [0008]     There is a need for apparatus and methods that reduce or eliminate plug formation and congestion in retort charcoal reactor systems.  
       SUMMARY OF THE INVENTION  
       [0009]     This invention provides apparatus and methods for the continuous production of charcoal in retort charcoal reactors while reducing or eliminating the above-mentioned problems with prior systems.  
         [0010]     The following embodiments and aspects thereof are described and illustrated in conjunction with apparatus and methods which are meant to be exemplary and illustrative, not limiting in scope.  
         [0011]     In one embodiment of the invention, a reactor is provided for converting organic material, the reactor comprising: 
    (a) a furnace;     (b) a retort extending through the furnace;     (c) an auger extending through the retort, the auger comprising a flight; and,     (d) one or more members projecting from an interior surface of the retort; 
 
 wherein the flight comprises two or more sections separated by one or more longitudinally extending gaps wherein the flight is at least partially removed, the gaps being coincident with the one or more members. 
   
 
         [0016]     In one embodiment of the invention, the members may be pins removably threaded through the wall of the retort.  
         [0017]     In one embodiment of the invention, the reactor has a gas collection and condensation system, the system comprising: 
    (a) one or more gas vents penetrating the retort;     (b) a collection vent in fluid communication with the one or more gas vents;     (c) a transfer vent in fluid communication with the gas collection vent, the transfer vent comprising a plurality of arms, each arm comprising a valve; and,     (d) a gas condenser comprising a plurality of branches, each branch in fluid communication with a corresponding arm, each branch comprising a cleaning means; 
 
 wherein closing any of the valves directs gases from the retort to the gas condenser through any of the arms with open valves, permitting the branch corresponding to the arm with the closed valve to be cleaned by the cleaning means. 
   
 
         [0022]     A method is also provided for converting organic material, the method comprising: 
    (a) introducing the organic material into an interior of a retort at an inlet region of the retort;     (b) advancing the organic material through the interior by rotating an auger extending through the interior, wherein the auger comprises a core and a flight; and     (c) disrupting any plugs of the organic material in the interior by providing one or more members fixed to the retort and projecting into the interior, the one or more members coinciding with longitudinally extending gaps in the flight.    
 
         [0026]     In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and the following detailed description. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]     In drawings which illustrate non-limiting specific embodiments of the invention:  
         [0028]      FIG. 1  is a semi-schematic side view of a reactor according to one embodiment of the invention;  
         [0029]      FIG. 2  is a cutaway side view of a retort according to one embodiment of the invention;  
         [0030]      FIG. 3  is a view corresponding to plane I-I of the gas condenser of the reactor shown in  FIG. 1 ; and  
         [0031]      FIG. 4  is a view corresponding to plane II-II of the retort shown in  FIG. 2 . 
     
    
     DETAILED DESCRIPTION  
       [0032]     A reactor  1  according to one embodiment of the invention is shown in  FIG. 1 . Feed system  2  supplies organic material to one or more anaerobic retorts  4 . Organic material may be wood waste or agricultural waste, for example. Heat provided by furnace  6  converts the organic material advancing through retorts  4  into charcoal. Exhaust from combustion of fuel used to heat furnace  6  is released at stack  8 . Charcoal produced in retorts  4  is collected at chute  10 . Pyrolysis gases released during charcoal production are vented from retorts  4  to condenser  12 . The gases are cooled in condenser  12  to form a distillate. The distillate may be routed to tank  14  for use as fuel to heat furnace  6 , or to boiler  16  for use as fuel to drive turbine  18 .  
         [0033]     Retort  4  according to one embodiment of the invention is shown in  FIG. 2 . Retort  4  has inlet region  18  and outlet region  20 . Feed system  2  loads organic material into inlet region  18 . Organic material converted to charcoal is collected by chute  10  at outlet region  20 . The bulk of retort  4  is sealed within the interior of furnace  6 .  
         [0034]     Auger  22  extends through the interior of retort  4 . Auger  22  is rotated along its longitudinal axis by a motor (not shown). The main components of auger  22  are core  24  and helical flight  26 .  
         [0035]     Core  24  has a constant diameter except at inlet region  18  where core  24  widens. As shown in  FIG. 2 , the diameter of core  24  may be widest at the upstream end of retort  4  and taper to a narrower constant diameter at approximately upstream wall  29  of furnace  6 . The widening of core  24  reduces the volume of organic material that could otherwise be loaded into retort  4  by feed system  2  at any given time. Reducing the volume of incoming organic material reduces the likelihood of organic material forming plugs in retort  4 .  
         [0036]     Auger  22  has gap sections  28 ,  28 ′ where a portion of flight  26  has been removed. Gap sections  28 ,  28 ′ are located downstream of upstream wall  29  of furnace  6 . One or more projections  30  correspond to each gap section  28 . Projections  30 ,  30 ′ are removably fixed to retort  4  and project radially from the interior surface of retort  4  toward core  24  of auger  22 . As shown in  FIG. 4 , projections  30 ,  30 ′ may be pins inserted through wall  31  of retort  4 , for example. Projections  30 ,  30 ′ serve to break up any plugs to allow free and continuous advancement of organic material through retort  4 .  
         [0037]     Flight  26  forms one or more fins  32  at outlet region  20  of retort  4 . The base of fin  32  is fixed to core  24  in parallel to the longitudinal axis of auger  22 . Fin  32  projects radially from core  24  toward the interior surface of retort  4 . Organic material advanced to outlet region  20 , which is mostly charcoal by this stage, is swept into chute  10  by the broad side of fin  32  as auger  22  rotates. Fin  32  thereby prevents buildup of organic material at outlet region  20 .  
         [0038]     The longitudinal axis of auger  22  is offset in relation to the longitudinal axis of retort  4  as shown in  FIG. 4 . Auger  22  is generally offset in a direction opposite to the location of exhaust gas vents  34 . Enlarged path  36  in retort  4  resulting from the offset of auger  22  improves venting of pyrolysis gases to exhaust vents  34 .  
         [0039]     Exhaust gas vents  34  connect to an exhaust collection vent  38 , which connects to transfer vent  40 . Transfer vent  40  splits into two arms. Each arm has a valve  42  to control the flow of exhaust gases. Each arm of transfer vent  40  connects to a respective branch of Y-shaped gas condenser  44 , as shown in  FIG. 3 . When gas condenser  44  is clean, both valves  42  remain open. If one of the branches of gas condenser  44  becomes congested (with tar, for example) valve  42  in the corresponding arm of transfer  40  is closed. Once valve  42  is closed, the congested branch of gas condenser  44  may be cleaned by cleaning means while exhaust gas continues to vent through the other arm of transfer vent  40  to its corresponding branch of gas condenser  44 . The cleaning means may be an auger  46  driven by a hydraulic piston  48 , for example, as shown in the embodiment illustrated in  FIG. 3 .  
         [0040]     Apparatus according to a specific embodiment of the invention will now be described. The following specifications are currently preferred where the organic matter being used as raw material is sawdust. These specifications are included here for illustrative purposes.  
         [0041]     The optimal temperature to which furnace  6  should heat retort  4  is approximately 600° C. The interior of furnace  6  is preferably coated with a suitable lining  50  such as a 1500° C. tolerant refractory. Lining  50  should be at least 3 inches thick. Thermal insulation  52 , at least one inch thick, should be provided between lining  50  and outer wall  54  of furnace  6 . Outer wall  54  may be fabricated of steel.  
         [0042]     Retort  4  ideally has an internal diameter of about 14 inches. Diameter  56  of flight  26  is ideally about 12 inches. Enlarged path  36  created by the offset of auger  22  in retort  4  has a maximum height  58  of about 2 inches.  
         [0043]     Pitch  60  of flight  26  is ideally about 9 inches. Plug formation tends to occur with substantially lower pitch diameters, while substantially higher pitch diameters do not provide sufficient time for organic material in retort  4  to convert to charcoal.  
         [0044]     Auger  22  ideally has two gap sections  28 ,  28 ′ and two corresponding projections  30 ,  30 ′. Gap sections  28 ,  28 ′ should be about 4 inches in length. First gap section  28  begins at about 12 inches downstream of upstream wall  29  of furnace  6 . Second gap section  28 ′ begins at about 24 inches downstream of upstream wall  29  of furnace  6 . First and second projections  30 ,  30 ′ are removably fixed to locations on retort  4  corresponding to about the centre of respective first and second gap sections  28 ,  28 ′. Ideally, the distance by which projections  30 ,  30 ′ project into retort  4  is adjustable, for example by providing threads on projections  30 ,  30 ′ and corresponding threaded holes in retort  4 .  
         [0045]     Six exhaust gas vents  34  are ideally provided for each retort  4 . This number of exhaust gas vents has been found to provide substantially complete discharge of pyrolysis gases from retort  4 .  
         [0046]     As will be apparent to those skilled in the art in 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. For example: 
        projections  30  may be of various shapes and sizes provided that the overall advancement of organic material is facilitated (by breaking up plugs) rather than impeded (by blocking the flow of the organic material);     more than one projection  30 ,  30 ′ may correspond to each gap section  28 ,  28 ′;     fin  32  may be of various, generally flat shapes;     fin  32  may be fixed to core  24  independently of flight  26 ; and     alternative means for cleaning gas condenser  44  may be provided. For example, auger  46  may be substituted with a brush with metallic bristles.        
 
         [0052]     Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.