The combustion apparatus 1 of the present invention is comprised of an insulated housing 10, a primary combustion chamber 20, a secondary combustion chamber 22, a divider 30 disposed between and separating the primary and secondary combustion chambers 20,22, an oxygen introduction mechanism 40, a pressurizing mechanism 50, and an exhaust structure 60.
The housing 10 of the present invention is constructed of a heavy-duty metallic material, such as steel or cast iron, though other materials may also be used. It comprises insulation within its interior sufficient to allow for safe contact of the outer surface during operation of the combustion apparatus 1. The housing 10 defines an internal space in which the other elements are located, though portions of the pressurizing mechanism 50 and the exhaust structure 60 extend outside the housing 10. See
The primary combustion chamber 20 is a contained space located within the housing 10, suitably adapted to contain a quantity of solid fuel 5 and gases and to allow for the combustion of the fuel 5 and gases. See
One or more of the housing's 10 access doors 80 allow access into the primary combustion chamber 20, and one or more of the housing's 10 access doors 80 allow access into the secondary combustion chamber 22. Fuel 5 may be loaded into the primary combustion chamber 20 through the access doors 80, and residue from combustion, such as fine ash, may be removed from the combustion chambers 20,22 through the access doors 80.
The divider 30 between the primary and secondary combustion chambers 20,22 has a first surface 32 located within the primary combustion chamber 20, a second surface 34 located within the secondary combustion chamber 22, and at least one aperture 36 passing completely through it from the first surface 32 to the second surface 34, resulting in the primary combustion chamber 20 and the secondary combustion chamber 22 being in communication with each other through the aperture or apertures 36. See
The divider 30 may have any shape or configuration suitable for separating the primary and secondary combustion chambers 20,22, as described above. In one embodiment the divider 30 may be formed of a plurality of intersecting rods, forming a grate. In another embodiment the divider 30 may be a single planar member having one or more apertures formed through it. In the preferred embodiment of the present invention, the divider 30 is comprised of multiple elongated rectangular bricks 38 placed side by side, each brick 38 placed proximate to another brick 38 such that a gap exists between the pair, with each gap representing an aperture 36 of the divider 30. See
Both the primary combustion chamber 20 and the secondary combustion chamber 22 may be lined with castable refractory ceramic material. In the preferred embodiment the primary combustion chamber 20 is lined along one or more of its vertical walls for a portion of the height of those walls, beginning from the bottom of the chamber 20 and extending upwards, and the secondary combustion chamber 22 is lined along one or more of its vertical walls, beginning from the top of the chamber 22 and extending downwards. See
The oxygen introduction mechanism 40 of the present invention is suitably adapted to direct oxygen into the primary and secondary combustion chambers 20,22 in a controlled manner. See
A controlled amount of combustion air (comprised at least in part of oxygen) travels through the duct work 48 and through the primary and secondary inlets 42,44. In the preferred embodiment the amount of combustion air passing through the primary inlets 42 and the secondary inlets 44, respectively, is controlled by the length of duct work 48 the combustion air must pass through before arriving at the respective inlets 42,44, in combination with the gas flow resistance of said ductwork 48 and inlets 42,44. An additional or alternate mechanism for controlling the combustion air passing through the oxygen introduction mechanism 40 involves the use of one or more dampers 46 situated within the duct work 48 of the oxygen introduction mechanism 40. See
In the preferred embodiment the damper or dampers 46 of the oxygen introduction mechanism 40 are suitably adapted to automatically be positioned to the closed position when operation of the combustion apparatus 1 must cease due to unsuitable environmental conditions. This stops combustion, thereby preventing the buildup of heat in the system. Each damper 46 comprises a gravity-based mechanism which disposes the damper 46 to the closed position. Alternatively, a spring mechanism may be used to dispose the damper 46 to the closed position. The flow of combustion air, controlled by the pressurizing mechanism 50, is sufficient to overcome the force of gravity on the damper 46 and disposes the damper 46 to the open position. During adverse environmental conditions, such as overheating, the pressurizing mechanism 50 can be stopped to completely halt the flow of combustion air into the duct work 48, whereby gravity returns the damper 46 to the closed position. A loss of power to the combustion apparatus 1, which could cause damage to the heating system if heat were to continue to be generated, would also stop the pressurizing mechanism 50 from causing air to flow into the duct work 48, achieving the same result and a complete cessation of combustion. Alternatively, the damper or dampers 46 can be mechanically positioned to the closed position, by a manual lever or by an actuator.
The primary inlet or inlets 42 are located in the primary combustion chamber 20 and are oriented to direct oxygen onto fuel 5 placed into the primary combustion chamber 20. In the preferred embodiment there are multiple primary inlets 42, with the primary inlets 42 disposed along at least two of the side walls of the primary combustion chamber 20. See
The secondary inlet or inlets 44 are located in the secondary combustion chamber 22 and are oriented to direct oxygen into the burn region 24 of the secondary combustion chamber 22. In the preferred embodiment there are multiple secondary inlets 44, and in the most preferred embodiment the secondary inlets 44 are apertures formed bi-laterally into a horizontal extension of the duct work 48 located within the secondary combustion chamber 22 proximate to the divider 30. See
The pressurizing mechanism 50 of the present invention is suitably adapted to supply positive pressure to the primary combustion chamber 20 to create a pressure differential between the gases contained in the primary combustion chamber 20 and the gases contained in the secondary combustion chamber 22, such that the gases contained in the primary combustion chamber 20 are at a higher pressure relative to the gases contained in the secondary combustion chamber 22. The pressure differential must be sufficient to cause gases contained in the primary combustion chamber 20 to flow through the aperture or apertures 36 of the divider 30 into the secondary combustion chamber 22. In the most preferred embodiment, the pressure differential is between 0.005 and 0.030 inches of mercury as measured by the difference in pressures between the maximal values of the primary inlet or inlets 42 and secondary inlet or inlets 44. During combustion this pressure differential causes the flow of combustion gases through the divider 30 in a downward direction, resulting in a downward burn in the burn region 24 of the secondary combustion chamber 22.
The pressurizing mechanism 50 may comprise any means for generating positive pressure to create the required pressure differential. In the preferred embodiment the pressurizing mechanism 50 comprises a low power electric fan. See
The combustion apparatus 1 may comprise a thermostatic control device, such as a thermostat. The thermostatic control device must be suitably adapted to control the combustion of fuel 5 and gases contained within the combustion apparatus 1, such that when the thermostatic control device calls for heat fuel 5 and gases within the combustion apparatus 1 are burned and when the thermostatic control device does not call for heat the burning of fuel 5 and gases within the combustion apparatus 1 ceases. This thermostatic control of combustion makes the combustion apparatus 1 more convenient to use and better regulates the ability of the combustion apparatus 1 to provide only desired amounts of heat to a heating system. This in turn yields better fuel efficiency. In the preferred embodiment, the thermostatic control device controls the operation of the oxygen introduction mechanism 40, such that thermostatic control is achieved by depriving oxygen to extinguish combustion, and re-introducing oxygen to re-ignite combustion. No separate energy source is needed to re-ignite combustion, because the temperature within the combustion chambers 20,22 is above the flash point of the fuel 5. In this embodiment, when the thermostatic control device calls for heat the thermostatic control device positions the damper or dampers 46 of the oxygen introduction mechanism 40 to the open position, allowing combustion air to be introduced into the combustion chambers 20,22, and when the thermostatic control device does not call for heat the thermostatic control device positions the damper or dampers 46 of the oxygen introduction mechanism 40 to the closed position, preventing further introduction of combustion air into the combustion chambers 20,22. In the most preferred embodiment, the use of a thermostatic control device in conjunction with the use of castable refractory ceramic material for the divider 30 and combustion chamber liners 26 ensures efficient extinguishment and re-ignition of combustion on an as-needed basis.
The exhaust structure 60 of the present invention is suitably adapted to remove heated gases from the secondary combustion chamber 22. It has a connection end 62 in communication with the secondary combustion chamber 22, and a chimney which vents outside the housing 10 of the combustion apparatus 1. See
The combustion apparatus 1 may further comprise a bypass damper 90. See
The combustion apparatus 1 may also comprise a heat exchanger 70. See
In the preferred embodiment the heat exchanger 70 is located within the housing 10 but remotely from the secondary combustion chamber 22 in such a manner that heated gases moving from the secondary combustion chamber 22 via the exhaust structure 60 to the heat exchanger 70 must move at least partially in a downward direction prior to reaching the heat exchanger 70. This is a safety feature, since the failure of a circulating pump could prevent the heat exchange medium from releasing heat energy, and an uncontrolled buildup of heat energy in the heat exchange medium could lead to a rupture of the closed loop piping. Moving the heated gases in a downward direction can only be achieved by applying a force to the gases, for example, the pressure differential created by the pressurizing mechanism 50 is sufficient to move the gases downward. However, upon a power failure, which would disable the circulating pump, the pressurizing mechanism 50 would also cease pressurizing the system, causing the damper or dampers 46 of the oxygen introduction mechanism 40 to return to the closed position, completely halting combustion. This prevents more heat energy from being created, and the heated gases already in the combustion apparatus 1 will naturally rise, moving away from the heat exchanger 70. This dual safety design greatly reduces the risk of an undesirable overheating of the heat exchange medium of the heat exchanger 70.
In the most preferred embodiment the heat exchanger 70 runs horizontally along the bottom of the housing 10, beneath the secondary combustion chamber 22, and then extends vertically along the rear of the housing 10. See
The initial combustion of the solid fuel 5 occurs in the lower portions of the primary combustion chamber 20. Combustion air combines with combustion gases released from the fuel 5 to feed the combustion process. A char fuel bed 7 is created from an initial preparatory combustion. The char fuel bed 7 is created from the lowest portions of the fuel 5 located at the bottom of the primary combustion chamber 20. The top of the char fuel bed 7 is proximate to the primary inlets 42 of the oxygen introduction mechanism 40. Gasification of the solid fuel 5 occurs above the char fuel bed 7, releasing combustion gases which are burned in the initial combustion; these gases are then forced downward by the pressure differential through the char fuel bed 7 and through the apertures 36 of the divider 30 into the secondary combustion chamber 22, becoming superheated in the process. The addition of a controlled amount of combustion air into the burn region 24 of the secondary combustion chamber 22 causes the superheated combustion gases to re-ignite in the burn region 24 of the secondary combustion chamber 22, resulting in secondary burn achieving an extremely hot, clean, continuous blue flame. As a result of the two burns, the exhaust gases are extremely hot, reaching temperatures in excess of 2000° F., with very little particulate matter remaining. The gases then move past the heat exchanger 70 where heat energy is released into the heating system, and are then exhausted.
Modifications and variations may be made to the disclosed embodiments of the present invention without departing from the subject or spirit of the present invention as defined in the following claims.