EP0127881A1 - Hot water generator, in particular a central heating boiler, for solid fuel, especially for burning logs of wood - Google Patents

Abstract

1. Hot-water generator, in particular central heating boiler, for solid fuels especially for burning wood and, if required, also for liquid and gaseous fuels, comprising a firebox/heat-exchanger surrounded by a housing at a distance and surrounding a large-volume chamber substantially in the form of a cylinder with horizontal axis provided for accepting the solid fuel and delimited on its sides and on its rear end by double walls between which the water to be heated is circulated, and on its front end by a door, said double walls being interrupte at their lowermost part by at least one opening which is lined with a combustion nozzle, characterized in that the heating body (1) is composed of a plurality of identical annular hollow intermediate elements (11) each of which forms a closed annular chamber (14) around a central passage opening, each of said intermediate elements at one of its front faces having a local axial offset (20) which defines a recess part, two opposite holes (21, 22) being present in each of its two front faces ; of an annular front end element (10) which forms likewise a central opening, which provided with substantially opposite holes in at least one of its front faces and which is closed with a door (15, 17) in the plane of its other front face ; and of a hollow rear end element (12) without central opening which forms a double bottom and its provided with two substantially opposite holes in at least one of its front faces, said elements (10, 11, 12) lying end-to-end and being assembled so that the front faces with the said recess and the front faces without said recess of the successive intermediate elements (11) are disposed alternately in face-to-face and opposite relationship so that said recesses complete one one another in pairs defining thus a radial opening, and that the said holes (21, 22) of the successive elements (10, 11, 12) coincide, the firebox/heat-exchanger thus formed being set up with the said radial openings directed downwardly and each of said openings is lined with a jacket-like inserted element (25) which forms the combustion nozzle.

Description

The present invention relates to a hot water generator, in particular to a central heating boiler, with solid fuel, in particular with wood and, where appropriate, with liquid or gaseous fuel, comprising, surrounded at a distance by a carcass, a hearth-exchanger surrounding a large chamber, substantially in the shape of a cylinder with a horizontal axis, intended to receive solid fuel and delimited laterally and at the rear end by double walls between which circulates the water to be heated and, at the front end, by a door, the double walls being interrupted, in the lowest part of the chamber, by at least one opening furnished with a combustion bowl.

In such a reverse flame combustion type generator, both the inner wall and the outer wall of the double-walled chamber serve as the heating surface. Indeed, the inner wall is heated by the heat given off by the carbonization of the wood, which takes place inside the chamber, while the outer wall is heated by the flames and the hot gases of combustion proper to flames spilled volatile matter contained in the wood and released by carbonization, this combustion taking place when passing through the lower opening of the chamber and in the part below the chamber, the flames and combustion gases then skirting the outer wall of the chamber upwards and backwards before escaping into the chimney.

Such a generator is distinguished both by the complete combustion of the wood, due to the combustion with reverse flames (absence of bistrage, minimal CO and C0 _{2 content} in the combustion gases) and by the high efficiency due to the use of the inner wall and the outer wall of the heating body as a heat exchange surface.

This known hot water generator has a one-piece hearth-exchanger and has several drawbacks. On the one hand, the manufacture of the one-piece steel hearth-exchanger involves significant welding work resulting in a considerable labor cost. In addition, in the case of large boilers, the handling and transportation of the factory-assembled hearth-exchanger can cause problems. Furthermore, due to the manufacture of the hearth-exchanger in sheet steel, there are risks of corrosion.

The present invention relates to a hot water generator of the type defined above which, while retaining the advantages of complete combustion and high efficiency, can be manufactured at a reduced cost price, allows transport and simple handling with regard to the heat exchanger and eliminates or at least considerably reduces the risk of chemical corrosion (sulfuric acid, acetic acid).

In the hot water generator according to the present invention, the hearth-exchanger of the double wall type, has several openings in its lower part and is divided along its length into several elements. These elements comprise several identical hollow annular intermediate elements, each delimiting an annular chamber closed around a central passage opening. Each of these intermediate elements has on a front side a local axial recess defining an axially recessed part. Each of these intermediate elements also has two substantially opposite holes in each of these two end faces. The elements of the hearth-exchanger further include a rear end element, hollow, constituting a double bottom and having two substantially opposite holes in one of its front faces, as well as a connector leading outwards. The elements of the heat exchanger also include a hollow annular front end element defining, like the intermediate elements, an annular chamber closed around a central passage opening. This front end element which can be provided or devoid of the recess provided on the intermediate elements has two substantially opposite holes in one of its two front faces, as well as a connector leading outwards. The end elements and the intermediate elements are placed end to end and assembled in such a way that the front faces with recess and the front faces without recess of the successive elements are alternately in opposition and facing each other so that the recesses complement two in pairs to form a radial opening and the front holes of the successive elements coincide. Each of said radial openings is lined with an insert in the form of a jacket, constituting a combustion bowl without circulation of water.

The construction method according to the invention of the hearth-exchanger makes it possible to assemble the latter from several elements of reduced size which lend themselves without problem to manufacture by casting in cast iron. The works welding are therefore superfluous, the assembly being reduced to simple assembly work. This assembly can be carried out at the place of installation of the generator, particularly for high powers, which simplifies transport and handling. From a model of elements, it is possible to produce hot water generators of different powers, by the use of a more or less large number of intermediate elements. Finally, the production of cast iron elements greatly reduces the risk of corrosion compared to a steel plate heat exchanger.

According to one embodiment of the invention, the holes in the front faces of the elements of the hearth-exchanger are tapped and the elements are assembled using threaded sleeves screwed into said holes. According to another embodiment, the elements are assembled using biconical sleeves press fitted into the smooth holes of the elements of the exchanger hearth.

These are two simple assembly methods which, moreover, make it possible to easily replace a possibly faulty element.

The combustion air enters the chamber defined by the heat exchanger is carried out in the usual way at the front end of the heating body. In order, however, to ensure uniform combustion from the front to the rear of the hearth-exchanger, it is advantageous to provide shutters to reduce the passage section of a portion of the combustion bowls added in the lower openings of the hearth- exchanger.

• la fig. 1 est une vue en élévation latérale, partiellement en coupe longitudinale verticale, d'un foyer-échangeur conforme à l'invention installé dans une chaudière;
• la fig. 2 est une vue en élévation frontale d'un élément intermédiaire du corps de chauffe;
• les fig. 3 et 4 sont des coupes suivant III-III et IV-VI de la fig. 2.

Referring to the attached drawing, an illustrative and nonlimiting embodiment of a hot water generator according to the invention will be described below in more detail; on the drawing :

• fig. 1 is a side elevational view, partially in vertical longitudinal section, of a heat exchanger according to the invention installed in a boiler;
• fig. 2 is a front elevation view of an intermediate element of the heating body;
• fig. 3 and 4 are sections along III-III and IV-VI of FIG. 2.

The reverse combustion central heating boiler illustrated in fig. 1 includes a heat exchanger 1 which is in the form of a circular cylinder, elliptical or the like, with a horizontal axis. The hearth-exchanger 1 is surrounded at a distance, at its upper half and at the rear, by a carcass 2 which may preferably be of welded sheet steel. The carcass 2 comprises a side wall 3 which is substantially semi-cylindrical in its upper part and is extended vertically downwards to a base wall 4. The carcass 2 also comprises a rear wall 5 provided with a nozzle 6 intended for connection of the boiler to a chimney flue. The carcass 2 finally comprises a front wall 7 provided below the heating body 1, with a secondary air inlet 8a and a decentering door 8b. The base wall 4 is lined on its upper face with a layer 9 of refractory material.

The carcass 2 is advantageously surrounded by an insulating jacket (not shown).

The heating body 1 is composed of a succession of elements, namely a front end element 10, several intermediate elements 11 and a rear end element 12 which are connected to one another according to vertical planes perpendicular to the horizontal longitudinal axis of the hearth-exchanger 1.

The front end element 10 and the intermediate elements 11 each consist of a hollow annular element delimiting an annular chamber 13, 14, respectively, of square or rectangular section.

On the front end face of the front end element 10 is articulated a door 15 having a central opening 16 of square or rectangular shape 16 capable of being closed by a change door 17. This door 17 has an opening of primary air intake 18 controlled by a primary air shutter 19 under the action of a draft regulator (not shown) which usually detects the temperature of the water on departure to the radiators of the central heating installation .

The annular chamber 13 of the front end element 10 has a constant section over the entire circumference.

Each intermediate element 11 has on a front side, in the lower part, a local axial recess 20 defining a recessed part (see fig. 2 to 4). This step 20 causes a local reduction in the otherwise constant section of the annular chamber 14.

The rear end element 12 is a hollow element without central opening like the elements 10 and 11, constituting a double bottom for the hearth-exchanger 1.;

The intermediate elements 11 are placed end to end so that the front faces with recess and the front faces without detachment of the successive elements are alternately facing and in opposition, the recesses 20 facing each other completing each other in the form of 'A radial opening having a section twice that of each step 20.

Each intermediate element 11 has two substantially opposite holes 21, 22, one at the top and the other at the bottom, in each of its two front faces (see fig. 2 to 4). The front end element 10 and the rear end element 12 each have two corresponding holes in its front face turned towards the intermediate elements 11 and, preferably but not necessarily, two corresponding holes in its other front face.

The two flat end faces of the intermediate elements 11 are rectified, while the end elements 10 and 12 are rectified on their flat end face facing the intermediate elements 11.

For the assembly of the hearth-exchanger 1 from the elements 10, 11 and 12, the said elements are placed end to end so that the holes 21, 22 of the different elements coincide, by interposing a refractory sealing material between the faces front facing elements 10, 11 and 12, and the various elements are assembled by keeping them tight against each other. Thus, the chambers 13 and 14 of the elements 10 and 11 and the chamber of the element 12 communicate with each other through the holes 21 and 22. Consequently, the hearth-exchanger 1 can be inserted in a heating circuit by means of a connector 23 provided on the front end element 10 and a connector 24 provided on the rear end element 12.

Each lower opening formed in the hearth-exchanger 1 by the recesses 20 of two intermediate elements 11 of which the recesses 20 complement each other is provided with a jacket 25 attached from the top, protruding from the hearth-exchanger 1 downwards. This shirt 25 serves as a "combustion bowl".

We recognize on f ig. 1 that the combustion bowl 25 closest to the primary air intake opening 18 comprises a shutter 26 reducing the passage section of the bowl 25. The next bowl 25 also includes a shutter 27 which reduces the cross-section of passage of the bowl 25 in a weaker as the shutter 26. This gradual reduction in the cross section of the combustion bowls as one approaches the primary air intake opening 18 ensures a uniform distribution of the primary combustion air on the various lower openings of the hearth-exchanger 1, hence regular combustion through the various combustion bowls, despite the different distances of these bowls from the primary air intake opening, and despite the use of all identical intermediate elements 11 and identical combustion bowls 25.

Different embodiments are possible for the assembly of the elements 10, 11 and 12 in the form of a hearth-exchanger 1.

A particularly advantageous embodiment consists in assembling said elements in the manner of the elements of a cast iron radiator. To this end, the holes 21, 22 of the elements 10, 11, 12 can be tapped and the neighboring elements are then tightened against each other using threaded sleeves 28 screwed into the tapped holes provided in the front faces in look at neighboring elements, each sleeve 28 having a left-hand thread and a right-hand thread. Another possibility is to use smooth biconical sleeves 28 and press these sleeves into the smooth holes 21, 22 of the elements 10, 11 and 12.

In both cases, at least one of the end elements 10 and 12 must have holes 21, 22 in its two front faces in order to allow such an assembly which is done from the inside. The holes of the end elements 10, 12 not receiving sleeves 28 can be closed with plugs or used to connect the hearth-exchanger 1 to the heating circuit, as shown by the connector 23 of the front end element 10 according to FIG. 1. It is also possible to use this opening to connect other accessories, for example a draft regulator acting on the flap 19 of primary air intake.

When assembling using press-fitted sleeves, it is preferable to provide, outside the hearth-exchanger, several axial tie rods to tighten the elements 10, 11 and 12.

Although the boiler as described above and shown in the accompanying drawing, of the reverse flame combustion type, is designed more particularly for the use of wood and in particular of wood logs as fuel, it goes without saying that it can also be equipped as a complement with a liquid fuel burner mounted on the door 17, or with a burner gas.

Claims (4)

1. Hot water generator, in particular central heating boiler, with solid fuel, in particular with wood, and, where appropriate, with liquid or gaseous fuel, comprising, surrounded at a distance by a carcass, a hearth-exchanger surrounding a chamber of large size, substantially in the shape of a cylinder with horizontal axis, intended to receive solid fuel and delimited laterally and at the rear end by double walls between which the water to be heated circulates and, at the front end, by a door, the double walls being interrupted, in the lowest part, by at least one opening furnished with a combustion bowl, characterized in that the heating body (1) is composed of several intermediate elements 1 hollow annular ( 11) identical each delimiting a closed annular chamber (14) around a central passage opening, each of said elements! intermediates comprising, on a front side, a local axial recess (20) defining a recessed part, and having two holes (21, 22) substantially opposite in each of its two front faces, of a front end element (10 ) hollow annular also delimiting a central opening, having two substantially opposite holes in at least one of its front faces and closed by a door (15, 17) in the plane of its other front face, and an element of hollow rear end (12) without central opening, constituting a double bottom and having two substantially opposite holes in at least one of its front faces, said elements (10, 11 and 12) being placed end to end and assembled so that the front faces with recess and the front faces without recess of the successive intermediate elements (11) are alternately opposite and in opposition so that the recesses complement each other two by two in the form of an opening re radial and that said holes (21, 22) of successive elements (10, 11, 12) coincide, the hearth-exchanger thus formed being installed so that said radial openings are facing downward, and that each of said openings is packed an insert (25) in the form of a jacket constituting the combustion bowl. 2. Generator according to claim 1, characterized in that said holes (21, 22) in the front faces of the elements (10, 11, 12) are tapped and that said elements are assembled using threaded sleeves (28 ) screwed into said holes. 3. Generator according to claim 1, characterized in that said elements (10, 11, 12) are assembled using biconical sleeves (28) fitted to the press in said smooth holes (21, 22) of the elements ( 10, 11, 12). 4. Generator according to any one of claims 1 to 3, characterized in that the hearth-exchanger further comprises shutters (26, 27) to reduce the passage section of part of the liners (25) reported in the lower openings of the heat exchanger.

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