A solid fuel boiler

Abstract

 A solid fuel boiler, particularly for domestic heating, has a fuel charge chamber (2) of elongate cylindrical conformation which is completely immersed in a heat exchange fluid contained in a casing (4). An electric fan (6) draws air from outside the boiler and directs it through a duct (5) into the fuel charge chamber (2) which, in its lower part, communicates with a combustion chamber (12), also immersed in the said heat exchange fluid, and which in turn communicates with a plurality of tubes (13) which extend vertically alongside the fuel charge chamber (2), and lead into a smoke collection chamber (20) from which the smoke can escape through a flue outlet.

Description

[0001] The present invention relates to a solid fuel boiler, and particularly to a boiler designed for domestic heating.

[0002] Domestic solid fuel boilers in which the combustion of a solid fuel, such as wood, coal and such like is used to heat a fluid (usuallywater) as a heat transfer medium for central heating or for domestic hot water are known. It is also known to provide such boilers with a forced draught by means of a fan which enables the direction of the draught to be selected by the designer and it has been found convenient for the draught to be directed downwardly with the fuel supported on a grille and charged from above through a hopper or fuel charge chamber. Down draught boilers, have many advantages, particularly the fact that they allow a charge to be loaded into the hopper and slowly added to the fire in a combustion chamber by gravity. Such boilers do have a very low energy yield, however, and they create significant problems for their installation.

[0003] Another disadvantage of known boilers of this type is constituted by the fact that significant maintenance problems occur because of the build up of deposits on the heat exchange surfaces, which deposits detrimentally affect the heat exchange itself. Further, known such boilers have a very complex structure and are consequently expensive.

[0004] The present invention seeks to reduce or even eliminate the above indicated disadvantages, and to provide a solid fuel boiler structure which can be used particularly for domestic heating, which permits very high energy yields to be obtained by exploiting substantially the whole of the calorific value of the fuel, whilst nevertheless obtaining a combustion which is easily controllable and adjustable in dep_- endence on the requirements of use.

[0005] According to the present invention, therefore, there is provided a solid fuel boiler particularly for domestic heating, characterised by the fact that it includes a fuel charge chamber of elongate cylindrical conformation which is completely immersed in a heat exchange fluid, means for directing air into the said fuel charge chamber and a combustion chamber in communication with the fuel charge chamber, the combustion chamber also being immersed in the heat exchange fluid and further being in communication with a plurality of tubes leading to a smoke collection chamber and extending vertically alongside the fuel charge chamber.

[0006] A particular advantage of the invention is that it provides a solid fuel boiler structure in which all the maintenance operations can be reduced to the minimum because the heat exchange surfaces may be disposed in such a way as to ensure that deposition of combustion residues or tarry elements is reduced to a minimum.

[0007] Another advantage of the present invention is that the boiler may be formed with a large surface area for heat exchange with the heat exchange fluid thus contributing to optimisation of the yield of the boiler as well as facilitating the heat exchange itself.

[0008] The boiler structure of the present invention, by its particular constructional characteristics, is able to offer the widest guarantees of reliability and security in use, and, moreover, is competitive from an economic point of view.

[0009] One embodiment of the invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a schematic section through a boiler structure formed according to the principles of the present invention, sectioned along a vertical longitudinal plane;

Figure 2 is a sectional view taken on the line III-III of Figure 1; and

Figure 3 is a sectional view taken on the line III-III of Figure 1.

[0010] With reference now to the drawings, the solid fuel boiler structure shown is particularly designed for domestic heating, and is generally indicated with the reference numeral 1; the boiler includes a fuel charge chamber 2, which advantageously has a substantially elongate cylindrical conformation and is immersed in a heat exchange fluid contained in an interspace 3 which is defined by an outer containment casing 4 which in practice defines the outer surface of the boiler.

[0011] At the lower end of the fuel charge chamber 2 is an air inlet duct 5 which leads from an electric fan 6 the function of which, during operation of the boiler, is to maintain the fuel charge chamber under a pressure greater then atmospheric pressure for reasons which will become clearer hereinbelow. Between the electric fan 6 and the duct 5 is a gravity-closed valve 7, on which acts an adjustment element 8 by means of which the desired flow rate can be set.

[0012] Near the top of the fuel charge chamber 2 there is a charging aperture 9 closed, in a manner known per se, with a door (not shown). Also at the top of the fuel charge chamber 2 there is provided a safety valve 10 which can be opened for lighting the boiler and which also serves to allow excess pressure in the fuel charge chamber to be relieved by venting into a smoke collection chamber 20 having a flue outlet which when the boiler is installed is connected to a chimney.

[0013] Moreover, a circular distributor is provided, which can be dismantled for cleaning, and which rests in the lower part of the chamber and is completely open in its upper part and closed in its lower part.

[0014] In the floor of the fuel charge chamber 2 there is a diametral slot 11 which leads to a combustion chamber 12 positioned under the fuel charge chamber 10. The combustion chamber 12 is disposed transversely with respect to the fuel charge chamber and is in communication, at its rear, with an array of boiler tubes 13 which will be described in more detail hereinbelow. The front of the combustion chamber 12 is provided with an inspection door 14, and further is in communication by means of a branch duct 15 extending from the air inlet duct 5, with the electric fan. Air flow through the branch duct 1₅ is controllable by means of a flap valve 16 provided with an adjustment element 17.

[0015] The casing 4 extends around the combustion chamber 12 except for its front portion having the door 14 and branch duct 15, so that the combustion chamber 12 is also completely immersed in the heat exchange fluid.. Thus the walls of the combustion chamber 12 also act as heat exchange surfaces since the flames, which form in the upper part are directed by means of the flow of air generated by the electric fan to flow over the whole of the interior surfaces of the combustion chamber, thus obtaining a very effective heat exchange with a small volume. Moroever, the adjustable introduction of air through the branch duct 15 allows a complete combustion to be obtained and gives to the flame a blue colour similar to that obtainable with forced draught methane, butane or propane burners.

[0016] The tubes 13 all extend substantially vertically and run alongside the rear part of the fuel charge chamber 2; all of the tubes 13 are also completely immersed in the heat exchange fluid. At the upper end the tubes 13 open into the smoke collection chamber 20, which is connectable in a known way by a flue outlet to the flue of a chimney. The tubes 13 which are immersed in the heat exchange fluid can be considered as self cleaning in that the flow path for the combustion product gases through them is vertical and the smoke is conveyed through the tubes at a high speed both by the pull of the chimney and by the pressure generated by the fan 6 with very little pressure drop due to the low resistance. This avoids the deposition of soot within the tubes.

[0017] The smoke collection chamber 20 is situated in the upper part of the boiler and in part allows the heat exchange of the smoke from the combustion to be completed; moreover, within the chamber 20 is situated the safety valve 10 which allows the evacuation of air under pressure from the fuel charge chamber 2 if excess pressure should build up within the appliance during the operation of the boiler.

[0018] As indicated above, all the elements described above are housed within the outer casing 4 which allows all of these constitutent elements of the boiler to be held together and encloses all the heat exchange fluid. For completeness of description it is suitable to mention that the boiler described above also has the usual adjustment and safety controls and instrumentation which may be substantially similar to that utilised for normal liquid or gas fuelled boilers. In addition the boiler of the present invention also has an end-of- cycle or minimum temperature thermostat which is switched on, after lighting the boiler, by means of a switch, and which then permits the fuel in the boiler to be completely burned, and, at the same time, allows complete utilisation of the heat in the heat exchange fluid, thus recovering all the heat stored therein without forming acid condensates which would damage the internal heat exchange surfaces. However, when the heat exchange fluid falls to the predetermined temperature the thermostat switches off the electric fan thus avoiding unnecessary wear and saving electrical energy.

[0019] The boiler of the invention has no components which will deteriorate either by wear or by their particular function, such as insulators, refractories, refractory steels, components made in cast iron, turbulence elements, burners or the like and this gives the boiler described above advantages which are not present in boilers known in the art.

[0020] Thus, by the adoption of a fuel charge chamber which, together with the combustion chamber is completely immersed in the heat exchange fluid, the pos- ibility of increasing the obtainable yield to the maximum is obtained.

Claims

1. A solid fuel boiler particularly for domestic heating, characterised by the fact that it includes a fuel charge chamber (2) of elongate cylindrical conformation which is completely immersed in a heat exchange fluid, means (5,6) f_br directing air into the said fluid charge chamber (2) and a combustion chamber (12) in communication with the fuel charge chamber (2), the combustion chamber also being immersed in the heat exchange fluid and further being in communication with a plurality of tubes (13) leading to a smoke collection chamber (20) and extending vertically alongside the fuel charge chamber (2).

2. A solid fuel boiler according to Claim 1, characterised by the fact that the fuel charge chamber (2) has a fuel loading aperture (9) in the upper part thereof.

3 A solid fuel boiler according to Claim 1 or Claim 2, characterised by the fact that the fuel charge chamber 2 is in communication with the combustion chamber (12) by means of a diametrally extending slot (11) in the bottom of the fuel charge chamber (2).

4. A solid fuel boiler according to any preceding Claim, characterised by the fact that the combustion chamber (12) extends transversely under the fuel charge chamber (2).

5. A solid fuel boiler according to any preceding Claim, characterised by the fact that the said combustion chamber (12) has, in its front part, an access and inspection door (14) and is in communication with the said electric fan (6) by means of a branch duct (15).

6. A solid fuel boiler according to any preceding Claim, characterised by the fact that it further includes a safety valve (10) which controls the communication between the said fuel charge chamber (2) and the smoke collection chamber (20).

7. A solid fuel boiler according to any preceding Claim, characterised by the fact that it includes an outer casing (4) containing the said fuel charge chamber (2), the said combustion chamber (12) and the said plurality of tubes (13), and defining, in cooperation therewith, an interspace (3) for the circulation of the heat exchange fluid.

Drawing