Abstract:
A heating device for burning fuel pellets ( 2 ) having a spherical combustion area ( 7 ), the surrounding wall of which is perforated ( 37 ), is disclosed. The combustion area ( 7 ) is surrounded concentrically by a wall( 40 ) having perforations ( 36 ) and is spaced from the wall ( 10 ) of the combustion chamber. The space between the two walls ( 10  and  40 ) is utilized to hold the fuel pellets which are ignited by a heated medium directed from the outside towards both the walls ( 10  and  40 ).

Description:
FIELD OF THE INVENTION 
     The present invention relates to heating equipment allowing the use of particle shaped fuel of various materials such as pellets produced from starting materials of wood and the like. 
     BACKGROUND OF THE INVENTION 
     Several such types of equipment are known and the present invention aims at using an arrangement for burning brushwood waste. Two cylindrical units are used here, arranged concentrically so that a core area and an annular space are formed. Both the wails forming said unit are perforated and the annular space is filled with brushwood waste which is fed into the space from below. The brushwood waste is ignited and combustion is maintained by air being allowed to flow through perforations in the two pipes. This known arrangement provided the impulse to develop a completely new type of heating equipment for burning pellets. 
     SUMMARY OF THE INVENTION 
     The present invention has a central body with a flame outlet, the central body having coherent walls and being closed except for the flame outlet. The wall of the central unit is perforated. A wall is arranged concentrically outside said central unit and spaced from the wall of the central unit so that a space is formed, the outer walls of said space also being perforated. The space is filled with pellets and both units are subjected to medium directed towards the core unit. Initially the medium has elevated temperature so that the fuel is ignited. Once this has occurred the temperature of the medium supplied is reduced. Fuel is gradually supplied to the space around the central unit by a dosing device. The central unit and its surrounding outer wall can rotate about its axis when only one directed air jet is used. It is obvious that said air jet can be supplied to the central unit in a number of different ways and that rotation can thus be avoided. One way of avoiding rotation is for the outer wall to be surrounded by annular pipes, these pipes being arranged in rings around the outer wall and following each other so that substantially the entire outer wall is covered by pipes lying one on top of the other, each pipe also communicating with a perforation inside the wall. Each pipe is connected to a unit for supplying medium. The space for pellets, the outer wall of which is perforated, can cooperate with a closed wall situated outside the perforated wall of the pellet space and, together with this wall, forms a closed space with the exception of an inlet for medium. By means of transverse walls spaced from each other, the closed space can form a number of pipes situates one above the other and having substantially rectangular cross section, said pipes having a perforated wall. This rotation can be avoided if the outer wall is surrounded by annular pipes. These pipes are arranged as rings around the outer wall. The pipes are arranged one after the other so that substantially the entire outer wall is covered by pipes lying one on top of the other. Each pipe also communicates with a perforation inside the wall. Each pipe is connected to a unit for supplying medium. The supply of medium is controlled by means of a distributing unit connected to a fan. Said fan is also connected to a fuel-supply channel so that medium can be supplied to the central space via a valve in the transport channel. A number of openings are arranged around the edge of the flame outlet, said openings being connected to a fan which supplies medium to return uncombusted particles to the combustion chamber. The flame outlet is in communication with a container transferring heat from the flame to a heat-absorbing medium such as water, arranged in a container. This container may be connected, for instance, to various units which conduct the heat further to a heating system in which the heat is waterborne, for instance. The space transferring heat to the heat-absorbing medium is in communication with a flue-gas outlet such as a chimney. 
     For said heating equipment to function optimally a control unit is required which communicates with the chimney, with a dosing device, with both fans, with the distributing unit, and with a valve arranged on the central unit, said valve also acting as distributing means for fuel. A device is also connected to the control unit which reacts when the fuel is ignited and a device to indicate the temperature of the heat-absorbing medium. 
     All units in the equipment which are subjected to high temperatures shall be made of materials resistant to said high temperatures and a suitable material may be ceramic material or the like. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional characteristics of the present invention are revealed in the following description and the appended claims. The invention will be described in more detail with reference to the accompanying drawings in which 
     FIG. 1 shows a complete heating equipment, 
     FIGS. 2 and 3 show the fuel bin with dosing device in two different situations, 
     FIGS. 4,  5  and  6  show a distributing unit with control means in different situations, 
     FIG. 7 shows more clearly the actual heating unit in FIG. 1, 
     FIG. 8 also shows the heating unit, showing more clearly the medium-supply openings at the inlet end of the flame outlet, 
     FIG. 9 is a modification of FIG. 1, 
     FIG. 10 is a modification of the units  6 ,  7  and  16 , 
     FIG. 11 shows a modification of the flame outlet  8 , and 
     FIG. 12 shows a modification of the distributing unit  16 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a fuel bin  1  for pellets  2 . The fuel bin should be closed to prevent it being ignited from below. The fuel bin emerges into a dosing device  3  which supplies the transport channel  26  with fuel. The fuel is supplied to a spherical space  6  surrounding a combustion area  7  which shall function as combustion chamber and is completely closed with the exception of a flame outlet  8 . The outer wall  10  of the central area is perforated and forms one wall of the spherical space  6 , the other wall being formed by a wall  9  consisting of an outer wall  39  and an inner wall  40 . This inner wall is also perforated. From the flame outlet a heated medium is supplied to a space  11  arranged in a container  12  holding medium for absorbing heat. Water is a medium for absorbing heat and the container  12  can be connected to a system containing water or to some other system that requires energy. The space  11  communicates with a flue-gas outlet  13  which may be in the form of a chimney. A number of channels  38  are arranged at the inner end of the flame outlet and are connected to a channel  18  from a fan  17 . Medium can thus be blown in towards the centre of the combustion area  7 . The inner wall  40 , provided with a number of perforations, is surrounded by a number of medium-transporting units in the form of pipes  34 , each pipe forming a ring around the inner wall  40 . The pipes are arranged from the upper end of the wall  40  to its lower end. Each pipe is connected to a perforation in the inner wall  40  by means of a pipe connection  35 . Each pipe  34  is then connected to a pipe  28  leading to the distributing unit  16 . The distributing unit  16  is in communication with a fan  14  which also communicates with the transport channel  26  running between the dosing device  3  and the spherical space  6 . The distributing unit includes a heating device, not shown, for medium which passes the distributing unit. The distributing unit may be cylindrical and has a cylindrical partial wall  27  which can be turned by a motor  29  via a gear  30 . The control wall is secured by an arm  32  and this arm can be turned by the motor  29  via a shaft  31  so that some of the pipes  28  can be closed off, as well as the supply of medium from the connection  15 . FIGS. 7 and 8 show how medium is supplied from the fan  17  to the outlet openings  18  at the upper end of the flame outlet  8 . Furthermore, the inner combustion chamber is provided with a valve  9  at its upper end. The valve is arranged in a unit  4  protruding from the combustion chamber, said unit being substantially conical and provided with passages  33  so that when the valve is open air can be supplied via the passages  33  to the combustion chamber  7 . 
     As is clear from FIG. 1, control means are required if the heating equipment is to function optimally, and a control unit  41  is arranged for this purpose. The control unit  41  is provided with indicating means  19  at the dosing device,  20  at the chimney,  21  at the fan  17 ,  22  at the unit  4 ,  23  at the distributing unit  16  and  42  at the fan  14 . An indicating means, not shown, is also provided in the combustion chamber  7 , as well as indicating means in the space  11  and container  12 . 
     The equipment described functions as follows: the bin  1  is filled with pellets  2  which are then supplied via the dosing device  3  and transport channel  26 . When it reaches the unit  4  the material is split so that it is distributed uniformly in the combustion chamber  7 . When the spherical space  6  is full the fuel is ignited, this being achieved by medium flowing from the fan  14  to the distributing unit  16  which contains a heating device, not shown, which heats the medium, the latter then being supplied to the spherical space  6 . Once this is ignited the heating device is switched off and the control wall  16  is set in the desired position with the aid of the motor  29 . If necessary the valve  5  may be opened so that air is supplied to the combustion chamber  7  from above. The combustion chamber can then be supplied with air from the nozzle end of the flame outlet through the channel openings  38 . The equipment is trimmed by means of the control unit  41  so as to provide optimal energy, by influencing the various indicating devices. 
     Uncombusted particles can be returned to the centre of the combustion area by means of medium supplied through the channels  38 . The dosing device  3  will operate intermittently during function of the heating equipment. The fuel in the spherical space  6  shall be allowed to burn out when the heating equipment is no longer to be used. The medium from the fan  14  can subsequently be used to blow the spherical space  6  around the combustion area  7  clean, and all ash is collected in an ash box arranged in the space  11 . 
     Movable parts are avoided by the use of pipes forming rings as shown in FIG. 7 for the transport of medium, said rings receiving medium from the unit  16  and having branch pipes which supply the medium obtained to the perforations in the wall  40 . 
     Naturally the combustion area  7  with its wall  10  may be allowed to rotate with the concentrically arranged wall  40 , in which case no pipe system is required to the perforations. Instead a jet of medium can be directed towards the rotating unit and, since both the walls  10  and  40  rotate, the fuel in the spherical space  6  will be subjected to a continuous flow of medium. 
     With minor modifications, equipment of the present type can be adjusted to various systems designed to supply heat. 
     FIG. 9 differs from FIG. 1 in that the perforated outer wall of the fuel chamber is surrounded by pipes having rectangular cross section arranged one on top of the other. 
     FIG. 10 shows the central unit  7  and distributing unit  16  with a heating element  42 . 
     FIG. 11 shows the flame outlet  8  provided with outflow channels  38  which, when medium is flowing through them, cause rotation of the flame when it passes the flame outlet. 
     FIG. 12 shows how the distributing unit  16  supplies medium to the fuel space via rectangular pipes.