Patent Publication Number: US-2021190314-A1

Title: Fuel Management System for a Biomass Furnace

Description:
This application claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Application Ser. No. 62/950,210 filed Dec. 19, 2019, which is incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to a biomass furnace for transferring heat from combustion of biomass fuel in a combustion chamber of the furnace to a heating medium such as a fluid, whether liquid or gaseous, and more particularly to a fuel management system of the biomass furnace having a fuel delivery conveyor for supporting and displacing the fuel during combustion within the combustion chamber. The fuel management system is designed to be particularly suited for handling biomass fuel in the form of wood chips which generate ash following combustion. 
     BACKGROUND 
     It is known to provide a biomass furnace for transferring heat from combustion of biomass fuel in a combustion chamber of the furnace to a heating medium with a conveyor located in the combustion chamber to move or displace the fuel within the combustion chamber as it is being combusted. This allows the fuel already under combustion to be moved away from an inlet through which fuel is added to the combustion chamber for subsequent combustion so that the combustion chamber can be continuously replenished with fuel in a manner which substantially does not affect existing combustion. Biomass fuel which is consumed in such a furnace is generally provided in particulate form, and particularly in pelletized form, for example wood pellets. Pelletized biomass fuel typically burns clean so as not to leave behind substantial waste that requires cleaning to ensure reliable continued operation of the biomass furnace 
     SUMMARY OF THE INVENTION 
     According to an aspect of the invention there is provided a fuel management system for a biomass furnace having a combustion chamber, comprising: 
     a fuel delivery conveyor arranged to be located in the combustion chamber for receiving biomass fuel to be combusted therein, the fuel delivery conveyor defining a support surface for supporting the fuel during combustion and being operable to displace the fuel as the fuel is being combusted in the combustion chamber; and 
     an ash removal conveyor operatively communicated with the fuel delivery conveyor to receive therefrom ash generated by the combustion of the fuel, the ash removal conveyor being arranged to transfer the ash to a location external of the combustion chamber. 
     Thus there is provided a conveyor for automatically removing the ash generated by combustion so that the fuel management system can continue to generate heat without interference due to the generated ash. 
     According to another aspect of the invention there is provided a fuel management system for a biomass furnace having a combustion chamber, comprising: 
     a fuel delivery conveyor arranged to be located in the combustion chamber for receiving biomass fuel to be combusted therein, the fuel delivery conveyor defining a support surface for supporting the fuel during combustion and being operable to displace the fuel in a conveyance direction of the fuel delivery conveyor as the fuel is being combusted in the combustion chamber; 
     an ash removal conveyor operatively communicated with the fuel delivery conveyor to receive therefrom ash generated by the combustion of the fuel, the ash removal conveyor being arranged to transfer the ash to a location external of the combustion chamber and being operable to displace the ash in a discharge direction which is substantially parallel to the conveyance direction of the fuel delivery conveyor; and 
     a common drive motor operatively coupled to both the fuel delivery conveyor and the ash removal conveyor to actuate the fuel delivery conveyor to displace the fuel and the ash removal conveyor to displace the ash. 
     This arrangement enables a single motor to drive two distinct conveyors of the system. 
     According to yet another aspect of the invention there is provided a fuel management system for a biomass furnace having a combustion chamber, comprising: 
     a fuel delivery conveyor arranged to be located in the combustion chamber for receiving biomass fuel to be combusted therein; 
     the fuel delivery conveyor being operable to displace the fuel in a conveyance direction of the fuel delivery conveyor as the fuel is being combusted in the combustion chamber; 
     the fuel delivery conveyor defining a support surface for supporting the fuel during combustion, the support surface locating a plurality of openings sized to prevent passage of the fuel which is not combusted; 
     ducting arranged to convey airflow generated by a blower for subsequent discharge into the combustion chamber; 
     the ducting defining at least one orifice below the support surface of the fuel delivery conveyor to supply the airflow at a location beneath the fuel; and 
     the ducting including one or more air nozzles at spaced locations along the conveyance direction and extending in a generally upward direction above the support surface for supplying the airflow at a location above the fuel. 
     In this arrangement common ducting feeds both underfire and overfire airflow. 
     According to a further aspect of the invention there is provided a fuel management system for a biomass furnace having a combustion chamber, comprising: 
     a fuel delivery conveyor arranged to be located in the combustion chamber for receiving biomass fuel to be combusted therein; 
     the fuel delivery conveyor being operable to displace the fuel in a conveyance direction of the fuel delivery conveyor as the fuel is being combusted in the combustion chamber; 
     the fuel delivery conveyor defining a support surface for supporting the fuel during combustion; 
     a housing operably supporting the fuel delivery conveyor; 
     the housing being arranged to be removably insertible into the combustion chamber of the furnace. 
     This provides an arrangement of fuel management system which is removable from the combustion chamber for easy maintenance of mechanical components. 
     According to yet a further aspect of the invention there is provided a biomass furnace for transferring heat from combustion of biomass fuel to a heating fluid, comprising: 
     a combustion chamber arranging for containing the combustion of the fuel; 
     a heat exchanger assembly in fluidic communication with the combustion chamber for receiving gases generated by the combustion of the fuel and arranged to transfer heat from the gases to the heating fluid; 
     a flue in fluidic communication with the heat exchanger assembly arranged for guiding the gases which have passed through the heat exchanger assembly away therefrom; 
     a fuel delivery conveyor located in the combustion chamber for receiving the fuel to be combusted therein; 
     the fuel delivery conveyor being operable to displace the fuel in a conveyance direction of the fuel delivery conveyor as the fuel is being combusted in the combustion chamber; 
     the fuel delivery conveyor defining a support surface for supporting the fuel during combustion; and 
     a housing operably supporting the fuel delivery conveyor and being removably insertible into the combustion chamber through an opening defined by the combustion chamber. 
     In one arrangement the fuel management system further includes a guide member supported over the support surface of the fuel delivery conveyor at a spaced location from an inlet through which the fuel is passed to the fuel delivery conveyor to substantially obstruct passage of ash in the conveyance direction, the guide member defining an upstanding surface to said support surface which is oriented at an acute angle to the conveyance direction of the fuel delivery conveyor so as to guide the ash to one side of the fuel delivery conveyor for subsequent transfer to the ash removal conveyor. 
     In one arrangement, when the support surface of the fuel delivery conveyor locates a plurality of openings sized to prevent passage of the fuel which is not combusted but to enable passage of the ash therethrough, the system includes a chute extending underneath the support surface and arranged to guide the ash which has passed through the openings to the ash removal conveyor by gravity. 
     In one arrangement the chute defines an upper guide surface extending in the conveyance direction and sloped downwardly to one side of the fuel delivery conveyor to guide the ash towards the ash removal conveyor. 
     In one arrangement, when the system further includes a guide member supported over the support surface of the fuel delivery conveyor at a spaced location from an inlet through which the fuel is passed to the fuel delivery conveyor and defining an upstanding surface to the support surface to substantially obstruct passage of ash in the conveyance direction, an end of the chute is spaced in the conveyance direction from the upstanding surface so as to capture ash passing under the guide member. 
     In one arrangement the system further includes an ash transfer conveyor arranged externally of the combustion chamber and operatively communicated with the ash removal conveyor to receive the ash therefrom, the ash transfer conveyor being transversely oriented to the ash removal conveyor and being operable to displace the ash in a transverse direction to the discharge direction. 
     In one arrangement the ash transfer conveyor is also operatively coupled to the common drive motor so as to be actuated thereby to displace the ash in the transverse direction. 
     In one arrangement, drive shafts of the fuel delivery conveyor and the ash transfer conveyor are substantially parallel, a drive shaft of the ash removal conveyor is transversely oriented to the drive shaft of the fuel delivery conveyor, and wherein there is provided a first transmission operatively interconnecting the common drive motor and the drive shaft of the ash removal conveyor, and a second transmission operatively interconnecting the common drive motor and the drive shaft of each of the fuel delivery conveyor and the ash transfer conveyor. 
     In one arrangement the second transmission is operatively connected to the drive motor via the first transmission. 
     In one arrangement, when the system includes ducting arranged to convey airflow generated by a blower for subsequent discharge into the combustion chamber, and when the support surface of the fuel delivery conveyor locates a plurality of openings sized to prevent passage of the fuel which is not combusted, the ducting defines at least one orifice below the support surface of the fuel delivery conveyor to supply the airflow at a location beneath the fuel and also includes one or more air nozzles at spaced locations along the conveyance direction and extending in a generally upward direction above the support surface for supplying the airflow at a location above the fuel. 
     In one arrangement, when the support surface of the fuel delivery conveyor locates a plurality of openings sized to prevent passage of the fuel which is not combusted but to enable passage of the ash therethrough, and there is provided a chute extending underneath the support surface and arranged to guide the ash which has passed through the openings by gravity to waste, the at least one orifice is disposed above the chute and is configured to provide the airflow across a width of the chute to assist discharge of the ash to the ash removal conveyor or, generally, to waste. 
     In one arrangement the ducting extends generally in a U shape from one side of the fuel delivery conveyor, around an end of the support surface of the fuel delivery conveyor arranged at a spaced location from an inlet through which the fuel is passed to the fuel delivery conveyor, and to the other side of the fuel delivery conveyor, and the one or more air nozzles comprises a plurality of air nozzles located on either side of the fuel delivery conveyor. 
     In one arrangement the system further includes a single blower mounted in fluidic communication with the ducting and arranged to provide the airflow. 
     In one arrangement the single blower is mounted to one side of the fuel delivery conveyor. 
     In one arrangement the fuel delivery and ash removal conveyors and the drive motor are operably mounted on a common housing which is arranged to be removably insertible into the combustion chamber of the furnace. 
     In one arrangement, when the fuel management system further includes ducting arranged to convey airflow generated by a blower for subsequent discharge into the combustion chamber and which extends generally in a U shape from one side of the fuel delivery conveyor, around an end of the support surface of the fuel delivery conveyor arranged at a spaced location from an inlet through which the fuel is passed to the fuel delivery conveyor, and to the other side of the fuel delivery conveyor, the housing defines the ducting. 
     In one arrangement the housing comprises an exterior wall arranged to be located on an exterior side of the combustion chamber in which a ducting inlet is defined so as to communicate the ducting and the blower located externally of the housing. 
     In one arrangement, when the fuel management system further includes further including an ash transfer conveyor arranged externally of the combustion chamber and operatively communicated with the ash removal conveyor to receive the ash therefrom, the ash transfer conveyor is operably mounted on the common housing so as to be movable relative to the combustion chamber with the housing. 
     In one arrangement the drive motor is arranged to be located externally of the combustion chamber. 
     In one arrangement, when the fuel management system further includes at least one transmission operatively interconnecting the drive motor and drive shafts of the fuel delivery and ash removal conveyors, said at least one transmission is arranged to be mounted externally of the combustion chamber. 
     In one arrangement the ash removal conveyor is located to one side of the fuel delivery conveyor. 
     In one arrangement the ash removal conveyor is located at a height below the support surface of the fuel delivery conveyor. 
     In one arrangement the ash removal conveyor is operable to displace the ash in the discharge direction which is opposite to the conveyance direction of the fuel delivery conveyor. 
     In one arrangement, when the system further includes an ash removal conveyor operatively communicated with the fuel delivery conveyor to receive therefrom ash generated by the combustion of the fuel, the ash removal conveyor is operably mounted on the housing so as to be movable relative to the combustion chamber with the housing. 
     In one arrangement, when the system further includes an ash transfer conveyor operatively communicated with the ash removal conveyor to receive the ash therefrom and being operable to displace the ash in a transverse direction to the discharge direction, the ash transfer conveyor is operably mounted on the housing so as to be movable relative to the combustion chamber with the housing. 
     In one arrangement, when the system further includes ducting arranged to convey airflow generated by a blower for subsequent discharge into the combustion chamber, the ducting is defined by the housing. 
     In one arrangement, when the combustion chamber of the biomass furnace defines an opening arranged to permit passage of the housing into and out of the combustion chamber, the housing comprises an exterior wall arranged to be located on an exterior side of the combustion chamber and to close said opening of the combustion chamber and an inlet is defined in the exterior wall and arranged to permit passage of the fuel from a fuel supply located externally of the combustion chamber to the fuel delivery conveyor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described in conjunction with the accompanying drawings in which: 
         FIG. 1  is an exploded view of an arrangement of biomass furnace according to the present invention; 
         FIG. 2  is a side elevational view of the arrangement of furnace of  FIG. 1 ; 
         FIG. 3  is a top plan view of the arrangement of furnace of  FIG. 1 ; 
         FIG. 4  is an end elevational view of the arrangement of furnace of  FIG. 1 ; 
         FIG. 5  is a cross-sectional view along line  5 - 5  in  FIG. 4 ; 
         FIG. 6  is a perspective view of an arrangement of fuel management system according to the present invention; 
         FIG. 7  is another perspective view of the arrangement of fuel management system of  FIG. 6 , in which some components are omitted for convenience; 
         FIG. 8  is a top plan view of the arrangement of fuel management system of  FIG. 6 ; 
         FIG. 9  is a cross-sectional view along line  9 - 9  in  FIG. 8 ; and 
         FIG. 10  is a cross-sectional view along line  10 - 10  in  FIG. 9 . 
     
    
    
     In the drawings like characters of reference indicate corresponding parts in the different figures. 
     DETAILED DESCRIPTION 
     In the accompanying figures there is shown a biomass furnace  1  for transferring heat from combustion of biomass fuel, generally in particulate form, in a combustion chamber  2  of the furnace to a heating fluid. The biomass furnace includes a fuel management system  20  having a fuel delivery conveyor  22  for supporting and displacing the fuel during combustion within the combustion chamber. 
     Referring to  FIGS. 1-5 , the combustion chamber  2  is arranged for containing the combustion of the fuel. This is basically an insulated fireproof box within which the combustion takes place comprising a plurality of upstanding walls  4  on a base  6  enclosing an interior combustion space  7 . Typically there is provided an access opening  9  in one of the walls  4  which is sized for enabling inspection of the interior  7  of the chamber during combustion. A door  10  is provided to close the access opening  9 . 
     The furnace  1  includes a heat exchanger assembly  12  in fluidic communication with the combustion chamber  2  for receiving gases generated by the combustion of the fuel and arranged to transfer heat from the gases to the heating fluid. The heat exchanger assembly  12  is disposed above the combustion chamber  2  and includes a plurality of tubes  14  through which the combustion gases are guided as they rise and exit the combustion chamber. As the gases are conveyed through the tubes  14  the heat is transferred to the heating fluid (not shown). 
     A flue  17  of the furnace is in fluidic communication with the heat exchanger assembly  12  downstream of the combustion chamber  2  (relative to the flow of combustion gases through the furnace) and is arranged for guiding the gases which have passed through the heat exchanger assembly  12  away therefrom, generally towards an outside environment to which the waste gases are discharged. However, the flue  17  may be fluidically communicated with a downstream scrubber (not shown) for cleaning of the combustion gases prior to discharge to the outside environment. 
     A fan  18  is housed externally of the combustion chamber  2  and is arranged to generate an airflow ducted as by  19  so as to flow across the heat exchanger assembly  12  to carry heat therefrom for subsequent delivery to spaces in a building to be heated. In other arrangements which are not shown, the heat carrier fluid may be a liquid, not a gas as in the illustrated arrangement, such that the fan is replaced with a pump and ducting  19  replaced with suitable piping to convey the liquid. 
     Referring to  FIGS. 5-7 , the fuel management system  20  comprises the fuel delivery conveyor  22  which is arranged to be located in the combustion chamber  2  for receiving the fuel to be combusted therein. The fuel delivery conveyor  22  defines a support surface  24  for supporting the fuel during combustion, and the support surface locates a plurality of openings  25  sized to prevent passage of the fuel which is not combusted but to enable passage of ash generated by the combustion of the fuel therethrough. The fuel delivery conveyor  22  is operable to displace the fuel in a conveyance direction  27  of the fuel delivery conveyor as the fuel is being combusted in the combustion chamber  2 . 
     Referring now to  FIGS. 5 and 7 , in the illustrated arrangement the fuel delivery conveyor  22  is in the form of a belt conveyor arranged for rotation about a pair of parallel axes spaced from one another in the conveyance direction  27 . The conveyor  22  thus has an upper run  30  and a lower run  31  and comprises a plurality of metallic links  33  such that the upper run forms the support surface  24  in the form of a metallic grate. Each of the rotation axes are defined by a sprocket assembly  36  or  37  around which the endless loop of metallic links is entrained. One of the sprocket assemblies indicated at  36  is driven and the other at  37  is idle. Although a portion of the conveyor  22  extends beyond boundaries of the combustion chamber  2  defined by its walls  4 , the reason for which will be better appreciated shortly, a usable area of the upper run  30  for carrying fuel is confined to the interior  7  of the combustion chamber  2 . 
     Still referring to  FIGS. 5 and 7 , the system  20  includes an ash removal conveyor  40  operatively communicated with the fuel delivery conveyor  22  to receive therefrom the ash generated by the combustion of the fuel. The ash removal conveyor  40  is arranged to transfer the ash to a location external of the combustion chamber  2  and is operable to displace the ash in a discharge direction  43  which is substantially parallel to the conveyance direction  27  of the fuel delivery conveyor and opposite thereto. 
     As most clearly shown in  FIG. 10 , in the illustrated arrangement the ash removal conveyor  40  is in the form of a screw conveyor or auger having a central shaft  45  which is mounted for rotation within a tubular housing  46  and to which a helical flight  48  is connected so that rotation of the shaft  45  in the same direction that the flight winds around the shaft is conducive to transferring the ash along the tubular housing  46  in the discharge direction  43 . 
     Now referring back to  FIG. 5 , like the fuel delivery conveyor  22  the ash removal conveyor  40  is also arranged to be located in the furnace combustion chamber  2 . The ash removal conveyor  40  extends past the wall  4  of the combustion chamber where there is located, externally of the combustion chamber  2 , an ash transfer conveyor  49  operatively communicated with the ash removal conveyor  40  to receive the ash therefrom and convey the ash to a farther location from the furnace, such as towards waste. 
     As more clearly shown in  FIG. 10 , the ash removal conveyor  40  is located to one side of the fuel delivery conveyor  22  so that the ash is transferred thereto by movement generally in a direction transverse to the conveyance direction  27  of the fuel delivery conveyor. Also, the ash removal conveyor  40  is located at a height below the support surface  24  of the fuel delivery conveyor so that the ash can be transferred to the removal conveyor by the assistance of gravity. 
     Referring now to  FIGS. 6 and 8 , to transfer ash which has been retained on the support surface  24  and towards the ash removal conveyor  40 , the system  20  includes a guide member  52  supported over the support surface  24  of the fuel delivery conveyor at a spaced location from an inlet  54  through which the fuel is passed to the fuel delivery conveyor to substantially obstruct passage of ash in the conveyance direction  27  past the guide member  52 . That is, a bottom  52 A of the guide member  52  is located just above the support surface  24  so as to permit passage of the links  33  thereunder but to substantially retain the ash at a location of the guiding retention member  52  along the fuel delivery conveyor  22 . The guide member  52  defines a planar smooth surface  56  upstanding to the support surface  24  and oriented at an acute angle θ to the conveyance direction  27  of the fuel delivery conveyor so as to guide the ash to one side of the fuel delivery conveyor for subsequent transfer to the ash removal conveyor  40 . Thus as the fuel delivery conveyor  22  continues to operate in the conveyance direction  27 , the ash retained on the support surface  24  interacts with the upstanding surface  56  and gradually shifts to the side of the delivery conveyor  22  where there is located a discharge opening  59  through which the ash passes towards the removal conveyor  40 . In the illustrated arrangement the upstanding surface spans substantially the full width of the support surface  22  so as to guide all of the retained ash to a common side. 
     As more clearly shown in  FIG. 7 , additionally to the retaining guide member  52  the fuel management system  20  includes a chute  63  extending underneath the support surface  24  and arranged to guide the ash which has passed through the openings  25  in the support surface  24  to the ash removal conveyor  40  by gravity. The chute  63  defines an upper guide surface  65  extending in the conveyance direction  27 , that is the surface  65  is elongated in same, and sloped downwardly to one side of the fuel delivery conveyor  22  to guide the ash towards the ash removal conveyor  40 . As the ash removal conveyor  40  is located to one side of the delivery conveyor  22 , the upper guide surface  65  of the chute is sloped downwardly towards this same side. Also, a top chute opening subjacent the support surface  24  substantially spans the full length of the usable portion of the upper run  30  of the fuel delivery conveyor. A plurality of upper run support members  67  extending perpendicularly transversely to the conveyance direction  27  may interrupt the chute opening at longitudinally spaced locations of the fuel delivery conveyor  22  without substantially interfering with an ability of the chute to capture the falling ash. A rear end  69  of the chute is located at a position spaced in the conveyance direction  27  from the upstanding retaining guide surface  56  such that the chute extends underneath the guide member  52  so that any ash which passes underneath the guide member  52  may still be captured by the chute  63 . 
     Referring to  FIGS. 5-8 , with the ash transferred to the ash removal conveyor  40  which acts to remove the ash from the combustion chamber  2 , upon removal therefrom the ash is transferred to the ash transfer conveyor  49  which displaces the ash away from the combustion chamber  2  but in a different direction from the discharge direction  43  which would otherwise lead to a fuel supply (not shown) for the biomass furnace, as the ash removal conveyor  40  protrudes from the furnace wall  4  in which the inlet  54  for communicating the fuel supply with the combustion chamber  2  is formed. The ash transfer conveyor  49  is transversely oriented to the ash removal conveyor  40  and is operable to displace the ash in a transverse direction  72  to the discharge direction  43 . In the illustrated arrangement, the ash transfer conveyor  49  is oriented perpendicularly transversely to the ash removal conveyor and is operatively communicated with an inclined conveyor  74  to transfer the ash thereto, as more clearly shown in  FIG. 4 . The inclined conveyor  74  is operable to raise the ash for dumping into a waste collection receptacle (not shown). 
     As more clearly shown in  FIG. 10 , the ash transfer conveyor  49  is disposed under an end  75  of the ash removal conveyor  40  which is external to the combustion chamber  2  protruding beyond the furnace wall  4  so that the ash is dropped by gravity out of the removal conveyor  40  for subsequent transfer by the transfer conveyor  49 . The ash transfer conveyor  49  is in the form of a screw conveyor having a central shaft  77  mounted for rotation within a tubular housing  78  and to which a helical flight  80  is connected. 
     Thus the fuel management system  20  is able to support continuous combustion of the fuel within the combustion chamber  2  by displacing the fuel under combustion from the inlet  54  so that the combustion chamber  2  can be charged with further fuel, and by removing ash as it is generated so that the combustion chamber is automatically cleaned. 
     Still Referring to  FIGS. 5-10 , both the fuel delivery  22  and ash removal  40  conveyors are operatively coupled to a common drive motor  83  arranged to be located externally of the combustion chamber  2  which actuates the fuel delivery conveyor to displace the fuel and the ash removal conveyor to displace the ash. At least one transmission is provided to operatively interconnect the drive motor  83  and drive shafts of the fuel delivery and ash removal conveyors. The at least one transmission is arranged to be mounted externally of the combustion chamber, similarly to the motor  83 . The drive shaft of the fuel delivery conveyor  22  is defined by a shaft  36 A of the drive sprocket assembly  36  and the drive shaft of the ash removal conveyor is defined by the central shaft  45  thereof. 
     In the illustrated arrangement, the drive shafts of the fuel delivery conveyor  22  and the ash removal conveyor  40  are transversely oriented to one another such that first and second transmissions  86 ,  87  are provided in order to drive the two distinct conveyors using the same motor. More specifically, the first transmission  86  whose output shaft is parallel to the drive shaft  45  of the ash removal conveyor is directly connected to the motor  83 . As the motor  83  is mounted at a spaced height above the base  6  of the furnace, the first transmission  86  is mounted under the motor but also is disposed at a spaced height above the base  6  such that the output shaft carries a gear  89  which via a chain drives a gear  90  mounted to rotate with the drive shaft  45  of the ash removal conveyor which is located spaced below and to one side from the output shaft of the first transmission. In this manner the first transmission  86  operatively interconnects the common drive motor  83  and the drive shaft  45  of the ash removal conveyor  40 . 
     The second transmission  87  is directly connected to the first transmission so as to be operatively connected to the drive motor  83  via the first transmission  86 . The second transmission  87  is located at a common height above the base  6  as the first transmission and is directly connected to the shaft of the drive sprocket assembly  36  of the fuel delivery conveyor  22 . Thus the second transmission  87  operatively interconnects the common drive motor  83  and the fuel delivery conveyor. 
     As a drive shaft of the ash transfer conveyor  49 , which is defined by the shaft  77 , is oriented substantially parallel to the drive shaft  36 A of the fuel delivery conveyor, the second transmission  87  also is operatively connected to the ash transfer conveyor  49  so that the common drive motor  83  is operatively coupled to same to actuate the ash transfer conveyor to displace the ash. At the second transmission  87  there is provided a gear  92  which via a chain drives a gear  93  mounted on the drive shaft  77  of the ash removal conveyor disposed spaced below the second transmission. 
     Thus a single drive source is provided for all of the distinct conveyors of the fuel management system. 
     Referring to  FIG. 5 , the fuel management system  20  also includes ducting  96  arranged to convey airflow generated by a blower  98  (schematically shown) for subsequent discharge into the combustion chamber  2 . The ducting defines at least one orifice  99  below the support surface  24  of the fuel delivery conveyor  22  to supply the airflow at a location beneath the fuel and also includes one or more air nozzles  101  at spaced locations along the conveyance direction  27  and extending in a generally upward direction above the support surface  24  for supplying the airflow at a location above the fuel. That is, the air nozzles  101  which may be termed in industry as overfire air nozzles have discharge openings  101 A at a height above the support surface  24  supporting the fuel so as to feed air to the flames of combustion. 
     The orifice  99  is in the form of an elongated slot formed in the ducting  99  above the chute, and more specifically over an upper end thereof. The orifice  99  extends horizontally across substantially a full width of the chute so as to be configured to provide the airflow used to supply the combustion of the fuel across the width of the chute  63  to assist gravity discharge of the ash to the ash removal conveyor  40 , which eventually conveys the ash to waste. It will be appreciated that the orifice  99  is shown in stippled line as it is formed on a portion of the ducting which is not actually shown in  FIG. 5 , but rather on an opposite side to that shown therein. 
     The ducting  96  extends generally in a U shape from one side  22 A of the fuel delivery conveyor  22 , around an end of the support surface  24  of the fuel delivery conveyor arranged at a spaced location from the inlet  54  through which the fuel is passed to the fuel delivery conveyor, which in the illustrated arrangement is defined by the upstanding guide surface  56 , and to the other side  22 B of the fuel delivery conveyor. The one or more air nozzles comprises a plurality of air nozzles  101  located on either side  22 A,  22 B of the fuel delivery conveyor  22 , as more clearly shown in  FIG. 6 or 8 . Furthermore, there is provided a single blower  98  arranged to provide the airflow that is mounted externally of the combustion chamber  2  to one side of the fuel delivery conveyor  22  in fluidic communication with the ducting  96 . Thus the airflow is conveyed by the ducting  96  from a single source for discharge on either side of the fuel delivery conveyor  22 . 
     As such, a single source of forced air can be used to suitably supply an airflow for combustion. 
     In order to provide easier maintenance, the fuel delivery conveyor  22  is operably mounted on a removable housing  105  which is arranged to be removably insertible into the combustion chamber  2  of the furnace through an opening  106  defined by the combustion chamber. The ash removal conveyor  40  and the ash transfer conveyor  49  are also operably mounted on the housing  105  so as to be movable relative to the combustion chamber with the housing which is thus a common support for all of the distinct conveyors of the fuel management system. 
     In the illustrated arrangement the housing  105  comprises a box-shaped main body portion  108  which is received in the combustion chamber during use, and which carries the fuel delivery conveyor  22  and the ash removal conveyor  40 . The main body portion  108  is substantially enclosed and thus defines an enclosed support for the fuel delivery and ash removal conveyors. The ducting  96  is also defined thereby, with suitable interior walls arranged to guide the airflow from the proximal side  22 A of the fuel delivery conveyor  22  on which the blower  98  is located to the distal side  22 B of the delivery conveyor  22 . The housing also comprises an exterior wall  110  connected to the main body portion  108  and arranged to be located on an exterior side of the combustion chamber  2  in use. The exterior wall  110  acts to close the opening  106  of the combustion chamber  2  in use and defines the fuel supply inlet  54  which arranged to permit passage of the fuel from the fuel supply located externally of the combustion chamber  2  to the fuel delivery conveyor  22 . The ash transfer conveyor  49  is mounted to the exterior wall  110  and extends along same. Additionally, the exterior wall  110  is arranged with a mounting location  111  to receive an auger of the fuel supply mounted fixedly to the wall  110 . 
     The housing  105  defines an opening  112  beneath the lower run  31  of the fuel delivery conveyor and vertically above the ash transfer conveyor  49  such that ash which is displaced by the conveyor  22  past the guide member  52 , and which continues to be displaced along the lower run  31  as if to circulate back to the upper run  30 , is enabled to be discharged from the housing  105 . An upstanding surface may be provided along a leading side of the opening  112  relative to a direction of movement of the fuel delivery conveyor  22  along the lower run  31 , and projecting inwardly into the housing  105  so as to prevent the ash from recirculating to the upper run  30  and to urge the ash downwardly to the ash transfer conveyor  49 . Thus, in some arrangements, the ash removal conveyor  40  may be excluded and only the ash transfer conveyor  49  may be provided as the ash removal device, with a delivery mechanism of the ash thereto being the lower run  31  of the belt-style fuel delivery conveyor. 
     The motor  83  and the transmissions  86 ,  87  are also operably mounted to the removable housing  105  by a framework  113  which is connected on an exterior side of the exterior wall  110 . The framework  113  comprises a pair of L-shaped brackets in the form of legs, which at one end attach to the exterior wall  110  and which at the other end are arranged to rest on the base  6 . 
     The housing  105  is supported for movement relative to the furnace  1 , through the opening  106  which is sized to permit passage of the housing into and out of the combustion chamber  2 , by a set of wheels  118  rotatably mounted on a bottom of the main body portion  108 . The wheels  118  rollably support the housing on the base  6  which defines a planar upper support surface. 
     The foregoing arrangement works particularly well with wood chips as the biomass fuel which generate ash when combusted. 
     The scope of the claims should not be limited by the preferred embodiments set forth in the examples but should be given the broadest interpretation consistent with the specification as a whole.