Biomass fuel furnace system and related methods

A furnace system for heating a poultry brooder house includes a firebox for burning biomass fuel, and a grate within the firebox for burning the biomass fuel thereon. A distributor assembly may positioned within the firebox and is located directly above the grate. The distributor assembly includes a distributor plate having a plurality of apertures therethrough, and a distributor arm above the distributor plate that is movable relative to the distributor plate to cause biomass fuel supported on the plate to pass through the apertures and fall onto the grate. The furnace system may include a hopper assembly that defines a well for receiving a volume of biomass fuel for delivery to the grate or to the distributor plate.

TECHNICAL FIELD

This invention relates generally to the conversion of energy, and more particularly, to the conversion of biomass fuel from livestock into useful heat.

BACKGROUND

Commercial livestock operations, such as poultry operations, are known and may include, for example, relatively large buildings that house foul, such as turkeys and chickens, until these reach a desired weight. In these operations, the buildings must be heated to maintain the temperature within a desirable range, and the litter (or droppings) produced by the birds must be removed from the buildings. In conventional commercial poultry operations, heaters are used to provide heat to the buildings housing the birds, with known heaters being fueled by propane or natural gas, for example. The cost to operate these types of heaters, however, is increasingly more expensive due to high fuel costs. Since the profitability of a poultry operation is directly related to the costs associated with the buildings' operating costs, the profitability of the poultry operation decreases with rising heating costs unless the revenue received by the poultry operator (e.g., farmer) also increases. This may translate into higher prices for the consumer.

Removal of litter (or droppings) from the large buildings housing the birds may include placing clean litter on the floor of a poultry house before the birds are delivered. Known litter materials include organic materials such as sawdust, wood chips, and rice hull; inorganic materials such as sand; and processed materials such as shredded newspaper, for example. In operations of this type, the birds leave their droppings on the litter, which in turn absorbs most of the liquid content of the litter and adheres to the solid litter. Once the birds are removed from the poultry house, the clumped or caked portion of the soiled litter may then be removed from the poultry house and has generally been spread on farm land as a fertilizer, while the rest of the soiled litter may be left in the poultry house to be available for the next flock.

A problem associated with the processing of soiled litter arises when the litter is mixed with water, as a result of cleaning out of the poultry house, and/or from use of the soiled litter as a fertilizer. Specifically, the water exposed to the litter may become contaminated and become a threat to streams, lakes, or underground water supplies, and may ultimately contaminate the drinking supply. Government agencies in areas of the United States having significant poultry operations have recognized the dangers to the clean water supply. It has become recognized, for example, that soiled litter entering streams and lakes results in growth of organisms that attack and destroy fish in the streams and which may even attack other animals and/or humans, causing severe illness.

Soiled litter, in this type of operation, therefore often represents an expense and pollution liability rather than a marketable fertilizer product. For growers that are unable to simply pile up poultry litter, the only option is to transport the litter to an acceptable location for dumping or other type of disposal. This, of course, incurs additional handling and transportation costs that may affect the commercial viability of the poultry operation.

There is a need, therefore, for an apparatus and related methods that address the problems discussed above.

SUMMARY

In one embodiment, a furnace system is provided for heating a poultry brooder house. The furnace system includes a firebox for burning biomass fuel, and a grate within the firebox for burning the biomass fuel thereon. A distributor assembly is positioned within the firebox and is located directly above the grate. The distributor assembly includes a distributor plate having a plurality of apertures therethrough, and a distributor arm that is spaced above the distributor plate and which is movable relative to the distributor plate to cause biomass fuel supported on the plate to pass through the apertures and fall onto the grate.

The furnace system may include a hopper assembly that defines a well for receiving a volume of biomass fuel for delivery to the distributor plate. The well includes an inlet for receiving biomass fuel from a supply, and an outlet that communicates with an interior of the firebox and which is positioned above the distributor plate assembly. An agitator is disposed within the well and is movable to urge biomass fuel in the well through the outlet and onto the distributor plate.

The agitator may be sized and arranged to conform closely to the dimensions of the well, and the agitator may cooperate with the biomass fuel in the well to limit heat loss from combustion of biomass fuel in the firebox through the hopper assembly. The agitator may have first and second spaced apart agitator arms, wherein the first and second agitator arms are operatively coupled to a shaft at their respective proximal ends and are movable within the well to agitate biomass fuel in the well. At least one elongate member extends between the first arm and the second arm to facilitate agitation of the biomass fuel within the well.

In a specific embodiment, the furnace system has an actuator that is operatively coupled to the agitator, and a controller that communicates with the actuator and which controls operation of the actuator to move the agitator within the well such that biomass fuel within the well is urged through the outlet. At least one sensor is adapted to sense a volume of biomass fuel in the well, with the sensor communicating with the controller and generating a signal related to the sensed volume of biomass fuel in the well. The controller directs the actuator to move the agitator in response to the signal generated by the sensor. The furnace system may, alternatively or additionally, include a storage bin for receiving and storing a volume of biomass fuel for use in the furnace, and a conveyor that is associated with the storage bin and which is configured to deliver biomass fuel from the storage bin to the hopper assembly. A shredder may be located intermediate the storage bin and the hopper assembly for breaking up the biomass fuel into a size suitable for processing through the distributor assembly. The shredder may include a plurality of blades that are spaced from one another by a pre-determined distance, with this distance being substantially the same as a dimension of one or more of the apertures of the distributor plate.

In another specific embodiment, the furnace includes an actuator that is operatively coupled to the distributor arm, and a controller that communicates with the actuator and which controls operation of the actuator to move the distributor arm relative to the distributor plate. At least one sensor is adapted to sense a temperature within the firebox, with the sensor communicating with the controller and generating a signal related to the sensed temperature. The controller directs the actuator to move the distributor arm in response to the signal generated by the sensor. The controller may, for example, direct the actuator to move the distributor arm in an intermittent manner.

In a specific embodiment, the grate includes a first grate plate configured to receive biomass fuel thereon, with the first grate plate having a plurality of first apertures therethrough, and a second grate plate beneath the first grate plate and having a plurality of second apertures therethrough. The first grate plate is movable relative to the second grate plate, and the furnace system includes an actuator that is operatively coupled to the first grate plate and which is configured to move the first grate plate relative to the second grate plate to thereby effect removal of ash from the grate through the first and second apertures. At least some of the first or second apertures through the respective first and second grate plates may include slots having a transverse width of about 0.5 inch.

In a specific embodiment, the firebox of the furnace system includes a first chamber containing the grate and the distribution assembly for primary combustion of the biomass fuel, and a second chamber. The second chamber is in communication with the first chamber and receives gaseous products from the primary combustion of the biomass fuel for secondary combustion of the gaseous products combined with air. The furnace system may include a conduit communicating with the firebox and directing air into the firebox for mixing with the gaseous products to facilitate the secondary combustion. Additionally or alternatively, the furnace system may include a heat exchanger proximate an exit of the second chamber and which is in fluid communication with the poultry brooder house, with the heat exchanger being configured to heat air with heat produced by the second combustion for heating of the poultry brooder house. The furnace system may, additionally or alternatively, include an igniting apparatus, such as a gas burner or a propane heater, for example, proximate the grate, with the igniting apparatus providing initial ignition of biomass fuel received on the grate.

In yet another embodiment, a method is provided for heating a poultry brooder house. The method includes supporting biomass fuel on a grate within a firebox and burning the biomass fuel on the grate. The method includes sensing a temperature within the firebox. Biomass fuel is then supplied to the grate in response to the sensed temperature. The heat generated from combustion of the biomass fuel is used to heat the poultry brooder house. The method may include feeding biomass fuel into the firebox so as to maintain the height of the biomass fuel on the grate in the range of about 0.5 inch to about 4 inches. In another embodiment, biomass fuel is fed into the firebox to maintain the height of the biomass fuel at about 0.5 inch. Alternatively or additionally, the firebox includes an inlet for feeding the biomass fuel into the firebox, and the method includes maintaining a pre-determined amount of biomass fuel at the inlet so as to substantially block heat loss therethrough. In a specific embodiment, a pre-determined temperature is maintained in the firebox so as to permit self-ignition of the biomass fuel supplied onto the grate.

DETAILED DESCRIPTION

With reference to the figures, and particularly toFIGS. 1-2, a furnace system10is provided for heating a poultry house12, using biomass fuel such as, and without limitation, soiled litter14removed from the poultry house12. System10includes a furnace18that processes the litter14to produce heat which, in turn, heats air (arrows22,24) that is directed toward the poultry house12through ducts26. A storage bin30of the system10receives the litter14from the poultry house12, for example, through conveyors (not shown), manual processes, or any other suitable method. The storage bin30, which may, for example, be a silage loader, delivers litter14to the furnace18without any additional processing such as dewatering, for example. The storage bin30receives and accumulates the litter14, and supplies the litter14to an inlet of the furnace18in the form of a hopper assembly32. In this exemplary embodiment, the litter14is fed from the storage bin30to the hopper assembly32through a conveyor36. The system10may additionally or alternatively include a shredder or chipper45located intermediate the storage bin30and the hopper assembly32and which breaks up the litter14into a size that is suitable for processing through components of the furnace18described in further detail below.

In the embodiment shown, furnace system10includes a firebox50located below the hopper assembly32, from which it receives litter14, and an air-to-air heat exchanger54that is used to heat the air (arrows22) flowing through the heat exchanger54and toward the poultry house12. Firebox50includes a housing defined by one or more sidewalls103and a top wall104. Doors56, secured in a closed position by a latch57, provide access to an interior58of the firebox50to facilitate, for example, cleaning and/or maintaining the components in the interior of firebox50. As discussed in further detail below, a first air inlet60(FIG. 2) disposed at the base63, and a second air inlet61(FIGS. 3,3A) though a sidewall103of the firebox50provide combustion air, through respective blowers into the interior of the firebox50(only blower61aassociated with second air inlet61is shown). In particular, air entering firebox50through air inlets60,61facilitates primary and secondary combustion processes, within firebox50, for producing heat, as discussed more fully below. The heat exchanger54of furnace system10is in fluid communication with an exit68of the firebox50through a duct66(FIG. 4) and receives heat generated within the firebox50for heating incoming air (arrows22) that is then directed (arrows24) to the poultry house12, as explained in further detail below. Ducts26also direct a portion of the incoming air generally around the firebox50to facilitate cooling the firebox50. After being heated by the exterior surfaces of the firebox50, this portion of the air is rejoined with the air passing through the heat exchanger54and is directed to the poultry house12.

With reference toFIGS. 3 and 3A, the interior portions of hopper assembly32and firebox50are now described in further detail. The interior of hopper assembly32defines a well70that receives litter14and feeds it into the interior58of firebox50. An agitator78is mounted at the upper end of hopper assembly32, onto a frame80, and includes helical flightings82that facilitate feeding the litter14through an outlet86at the bottom end of hopper assembly32. In the embodiment shown, an actuator in the form of a motor88is supported by frame80, and drives a shaft90that in turn supports the helical flightings82. Rotation of the shaft90(arrows93) by action of motor88rotates the helical flightings82to thereby feed the litter14toward the bottom i.e., toward outlet86(arrows94). The agitator78may further include one or more upper arms87proximate the upper end of well70, and one or more lower arms89proximate the start of the helical flightings82. In the embodiment shown, pairs of upper arms87and lower arms89are disposed on opposite sides of the shaft90, however, it will be appreciated that various other arrangements are possible. Elongate members95, such as cables or rods, extend between the distal ends of associated upper and lower arms87,89and generally proximate the sidewalls of well70to facilitate agitation of the litter14and to prevent clumping of litter14within the well70.

Actuation of motor88to turn shaft90is selectively controlled by a controller96, such as a PLC, for example. In the embodiment shown, the hopper assembly32includes a sensor97apositioned within well70at a location to sense a volume of litter14within the well. Signals from sensor97arelated to the volume of litter14in well70are communicated to controller96for use in controlling the operation of motor88to feed litter14toward outlet86, and for controlling the operation of storage bin30and conveyor36to replenish litter14when the volume within well70is low. In one embodiment, controller96may keep track of the number of revolutions of shaft90and control operation of storage bin30and conveyor36to replenish well70after a predetermined number of revolutions. Operation of storage bin30and conveyor36may continue until a signal from sensor97ais received at the controller96, indicating that a desired volume of litter14within well70has been attained. In another embodiment, hopper assembly32may further include a second sensor97bpositioned within well70to sense the presence of litter14and to generate a signal related to a low volume of litter14within well70. Signals generated by second sensor97bmay be communicated to controller96to facilitate operation of motor88and/or storage bin30and conveyor36to maintain a desired volume of litter14within well70.

The hopper assembly32in this embodiment is thus configured to maintain a pre-selected volume of litter14in well70, for example, to facilitate feeding of litter14through outlet86into the firebox50. Alternatively or additionally, the hopper assembly32may be configured to maintain a pre-selected volume of litter14in well70so as to limit the loss of heat and/or gases from firebox50through hopper assembly32. More specifically, in this embodiment, the configuration of the helical flighting82and upper and lower arms87,89relative to the interior walls of well70and a bottom section32aof the hopper assembly32may be selected such that the litter14in well70and/or section32ais effective to plug section32ato thereby limit the escape of gases and/or heat from the interior of firebox50.

With continued reference toFIGS. 3 and 3A, litter14fed through outlet86of hopper assembly32may be deposited onto a distributor plate98of an optional distributor assembly100located inside a first chamber50aof firebox50. Distributor plate98is supported, in this exemplary embodiment, by support frame members102secured to the top wall104of firebox50, although this is intended to be exemplary rather than limiting. The distributor assembly100is configured to temporarily hold the litter14and controllably feed the litter14onto a grate110located within the first chamber50aand generally below the distributor plate98. To this end, the distributor assembly100includes a distributor arm112mounted, in this embodiment, to shaft90, and rotatable relative to the distributor plate98by action of motor88. Distributor arm112may be operable to rotate in one or both directions of rotation (i.e., clockwise and counter-clockwise), with rotation of the arm112being continuous or intermittent. In this regard, intermittent rotation of arm112may, in one embodiment, be such that distributor arm112periodically rotates less than a full revolution, stopping between rotations for a predetermined length of time, such as about 15 seconds, for example. In one embodiment, movement of distributor arm112is controlled by controller96to provide litter14to grate110at a desired rate.

Distributor arm112is spaced close to distributor plate98such that rotation of distributor arm112evenly distributes litter14across the distributor plate98and the grate110below. As noted above, the distributor arm112, in this embodiment, is mounted to shaft90, such that rotation of shaft90results in rotation of the distributor arm112and rotation of the agitator arms82of hopper assembly32. Those of ordinary skill in the art will readily appreciate, however, that distributor arm112may alternatively be rotatable independently from the agitator arms82, and may be controlled, for example, by a driving mechanism separate from motor88and shaft90.

With continued reference toFIGS. 3 and 3A, and with further reference toFIGS. 2A,4,4A,5, and7, rotation of distributor arm112causes litter14supported on the plate98to pass through (arrows116) a plurality of apertures118of the plate98. In this embodiment, and with particular reference toFIGS. 5 and 7, one or more of the apertures118may have a dimension (e.g., transverse width “d”) that is substantially the same as a spacing “s” between blades45aof shredder45(FIG. 4A), such that the litter14processed through the shredder45is of a size suitable to pass through the apertures118.

Litter14passing through the apertures118of plate98falls onto grate110for burning thereon. As discussed above, the movement of distributor arm112may be intermittent or continuous. The grate110of this exemplary embodiment includes first and second generally circular grate plates122,124(FIGS. 3A,4A,5, and6), each having respective sets of first apertures122a,124aand second apertures122b,124b, at least some of which may be in the form of slots having, for example, a transverse width of about 0.5 inch. Each of the first and second apertures122a,124a,122b,124bof this exemplary embodiment are in the form of slots of at least two different lengths. The first and second apertures122a,124a,122b,124bfacilitate the passage of ash “A” therethrough when aligned in registration with one another.

A pair of upwardly extending, concentric rims120a,120bpositioned radially outwardly from grate110are sized and arranged to receive a plurality of fire bricks126arranged in a side-by-side configuration to help retain the litter14on grate110.

An optional leveling arm125(FIGS. 3,3A) may be coupled to the shaft90, or to some other component, so as to be selectively movable relative to grate110. Specifically, the leveling arm125may be configured to selectively rotate relative to grate110so as to maintain a uniform layer of litter14across the grate110. The leveling arm125may further include a plurality of fingers125aextending downwardly toward grate110and arranged to rake through the litter14and ash “A” on grate110as leveling arm125is rotated. The raking action of fingers125areduces or eliminates the formation of hot spots in the ash that will tend to solidify, thereby maintaining the ash “A” at a size that will pass through grate110.

In another exemplary embodiment, furnace18may be provided without the optional distributor assembly100for receiving litter14from hopper assembly32. In such an embodiment, leveling arm125may be utilized to maintain a uniform layer of litter14across grate110, as discussed above.

The grate plates122,124are movable relative to one another such that, when the respective sets of apertures122a,124a,122b,124bare in registration with one another, ash “A” (FIG. 3A) produced by the burning of litter14on the grate110is allowed to pass through both sets of apertures122a,124a,122b,124band toward an ash-removing apparatus, discussed more fully below.

In the exemplary embodiment of theFIG. 6, relative rotation of the first and second grate plates122,124is facilitated by an actuator in the form of a air cylinder138operatively coupled to a source of pressurized air140. A drive rod138aof air cylinder138is operatively coupled to a protruding arm141, extending radially outwardly from a main portion of the first grate plate122, to cause selective rotation thereof (arrows143ofFIG. 6). When actuated, drive rod138aextends or retracts relative to a housing138b, causing rotation of arm141and rotation of the entire first grate plate122. This rotation selectively moves the first grate plate122relative to the second grate plate124, from a first position wherein the first and second apertures122a,122bthrough the first grate plate122are not in registration with the first and second apertures124a,124bof the second grate plate124, to a second position wherein the first and second apertures122a,122bthrough the first grate plate122are aligned in registration with the first and second apertures124a,124bof the second grate plate124. The first grate plate122is maintained in the first position during normal operation of the furnace18to burn litter14on grate110. The first grate plate is periodically moved to the second position by the air cylinder138, under the control of controller96, to align the apertures122a,124a,122b,124bof the first and second grate plates122,124so that ash “A” can pass therethrough onto an ash-removing apparatus.

Those of ordinary skill in the art will readily appreciate, however, that movement of the first and second grate plates122,124relative to one another may take various other forms, which may or may not include relative rotation of the grate plates122,124. For example, and without limitation, an alternative configuration may include rotation of both grate plates122,124, or linear, rather than rotational, movement of one or both grate plates122,124.

In exemplary embodiment shown in the figures, the ash-removing apparatus includes a generally V-shaped plate127and an auger128, driven by a motor130, that removes ash “A” supported on plate127. Rotation of auger128advances the ash “A” through an ash exit outlet132(FIGS. 4 and 5) away from the base63of firebox50, for further disposition. To facilitate moving ash “A” toward auger128, furnace18may further include a second, generally V-shaped plate129positioned within V-shaped plate127. The second V-shaped plate129is movable relative to V-shaped plate127by an actuator134, such as a pneumatic cylinder or any other suitable device (FIG. 4A). In the embodiment shown, an opening is formed in the second V-shaped plate129for receiving the auger128therein. Accordingly, as second V-shaped plate129is moved by actuator134, ash “A” is moved in a direction toward auger128for removal through exit outlet132.

The V-shaped plate127of this embodiment also facilitates the uniform distribution of combustion air (arrows60a) received through air inlet60. Specifically, combustion air (arrows60a) passes through a plurality of apertures127aof V-shaped plate127into the ash-receiving region127babove V-shaped plate127. Air then passes through combustion air apertures124cin the second grate plate124, which are aligned in registration with the first and second apertures122a,122bof the first grate plate122when the first grate plate is in the first position described above.

With particular reference toFIGS. 3A,4,4A and5, burning of the litter14on grate110is facilitated by combustion air received from outside of the firebox50through the first air inlet60(FIGS. 2,3A,5, and6). Initial ignition of the litter14on grate110may be facilitated by an igniting apparatus150located beneath grate110. Igniting apparatus150may, for example, be in the form of a gas burner or any other type of burner or heater. In the embodiment shown, igniting apparatus150is a power gas burner, Model No. HSG 400 available from Wayne Combustion Systems of Fort Wayne, Ind., received in a conduit62extending beneath grate110(FIGS. 4,4A,6). Igniting apparatus150may be controlled by controller96to selectively provide ignition of the litter14on grate110until combustion of the litter14is self-sustaining and/or until the temperature within first chamber50areaches a predetermined level. For example, in an exemplary embodiment, the igniting apparatus150may be kept energized until the temperature within first chamber50areaches about 500° F.

In operation, the frequency of actuation of the igniting apparatus150is minimized, in this embodiment, by maintaining the height of the litter14on grate110at a predetermined level. This predetermined level is such that combustion of litter14received on grate110from the distributor assembly100is self-sustaining by virtue of the relatively high temperature within the firebox50and by providing a proper amount of combustion air using a variable speed blower, for example. In this regard, for example, it has been found that maintaining the volume of litter14on grate110to have a height between about 0.5 inch and about 4 inches minimizes the required frequency of actuation of igniting apparatus150and eliminates or at least reduces the amount of smoke generated by combustion of litter14on grate110. In another exemplary embodiment, a volume of litter14on grate110is maintained corresponding to a height between about 0.5 inch to about 2 inches. In yet another exemplary embodiment, a volume of litter14on grate110is maintained corresponding to a height of about 0.5 inch to about 1 inch. In yet another exemplary embodiment, a volume of litter14on grate110is maintained corresponding to a height of about 0.5 inch.

In this embodiment, maintenance of a predetermined volume of litter14on grate110, and a predetermined temperature within first chamber50a, may be accomplished by supplying litter14to grate110at a rate selected to maintain the desired volume and temperature during combustion of the litter as described above. This operation is facilitated by one or more sensors162(one shown in the figures) that sense a temperature within firebox50. Signals from sensor162are communicated to controller96, which may adjust the operation of agitator78, supply bin30, and conveyor36to increase or decrease the rate at which litter14is provided to grate110. Controller96may also vary the speed of variable speed blowers that provide the primary and secondary combustion air to firebox50. For example, controller96may vary the speed of the blowers based on signals received from sensor162, the rate at which litter14is provided to grate110, or any other factors or combinations of factors.

Signals from sensor162may be utilized by controller96to control operation of the igniting apparatus150, although this is intended to be exemplary rather than limiting. While a single controller96has been shown and described herein, it will be appreciated that operation of the furnace system10, as generally described herein, may be controlled by more than one controller, as may be desired.

In another exemplary embodiment, the height of litter14on grate110is sensed by an optional sensor163(shown in phantom inFIG. 3A) positioned proximate the grate110. Sensor163may be a contact-type sensor, a non-contact-type sensor, or any other type of sensor suitable to sense a height of the litter14on grate110. Signals from sensor163may be communicated to controller96and used by controller96to control the operations of the storage bin30, conveyor36, hopper assembly32, grate110, combustion air blowers, or various other components of furnace system10. In such an embodiment, furnace18may or may not additionally include sensor162for sensing a temperature inside firebox50.

With continued particular reference toFIGS. 3A,4,4A, and5, burning (i.e., combustion) of litter14on grate110produces combustion gases (arrows168) that circulate within first chamber50a. Combustion gases (arrows168) leave the first chamber50aand enter a second chamber50bof firebox50through an opening170for secondary combustion. In the embodiment shown, second chamber50bis at least partially defined by a generally vertical wall174located in firebox50and extending downwardly from top wall104toward base63In this embodiment, secondary combustion air is provided through one or more conduits186extending horizontally across the interior of firebox50and proximate opening170. A variable speed blower61acontrolled by controller96is operatively coupled to conduits186to provide the secondary combustion air at a desired rate, and the secondary combustion air exits the conduits via a plurality of spaced apart apertures187disposed therealong. As the combustion gases move past conduit186and enter opening170, the secondary combustion air exiting apertures187turbulently mixes with the combustion gases and secondary combustion is achieved due to the relatively high temperatures within the firebox50. If complete combustion is not achieved at the opening170, additional conduits186may be provided within the second chamber50bto provided additional secondary combustion air for subsequent combustion within second chamber50b.

In one embodiment, an optional second igniting apparatus176may be in communication with the second chamber50bto facilitate combustion of the mixture of combustion gases and secondary combustion air therein. In the exemplary embodiment of the figures, the high temperature within firebox50is sufficient to ignite the mixture of combustion gases (arrows168) and secondary combustion air (arrows172), thus obviating the need for second igniting apparatus176. In this exemplary embodiment, supply of the secondary combustion air, as well as supply of the primary combustion air may be facilitated by one or more blowers, such as variable speed blowers, for example, controlled by a dedicated controller, such as controller96, as discussed above.

With particular reference toFIG. 4, heat produced by combustion within the second chamber50btravels (arrows190) through firebox exit68and through a plurality of tubes54aof the heat exchanger54. Exhaust gases (arrows188) from the combustion in second chamber50bleave furnace18through an outlet189. Air, such as forced air22, travels in cross-flow fashion past the tubes54aand is convection-heated by contact with the tubes54a. The resulting heated air24then flows, through ducts26(FIG. 2), to poultry house12to heat same.

While the above embodiments describe the burning of litter14from birds housed within poultry house12, it is contemplated that the above-described system and methods may additionally or alternatively include the burning of other types of biomass fuels that may or may not be supplied by the birds or other animals housed in a building heated by the combustion of the biomass fuel. In this regard, it is therefore contemplated that the furnace system may burn biomass fuels other than the exemplary bird litter and still fall within the scope of the present disclosure.

While the present invention has been illustrated by a description of various preferred embodiments and while these embodiments have been described in some detail, it is not the intention of the Applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Thus, the various features of the invention may be used alone or in numerous combinations depending on the needs and preferences of the user.