EP0054004A1 - Multi fuel heater - Google Patents

Abstract

This multi-fuel boiler possesses a combustion chamber (1) for the solid fuel, a combustion chamber (2) for the liquid or gaseous fuel, and a hopper (3) for feeding the combustion chamber (1) with coal. A water circuit (7, 8, 9, 10, 11) and a fume extractor (13) serve both the chambers jointly, the said chambers having their respective heat exchangers (12, 14) and the exchanger of the combustion chamber (1) extending adjacent to the rear wall of this chamber. A feed device is provided for discharging the coal parallel to the exchanger (12). <IMAGE>

Description

The present invention relates to a multi-fuel boiler in which the solid fuels on the one hand and the liquid or gaseous fuels on the other hand are burned in separate combustion chambers.

There are already multi-fuel boilers comprising two combustion chambers for alternately burning solid or fluid fuels. If, in these boilers, the automatic supply of fluid fuels does not pose a problem, it is not the same for solid fuels and in particular for coal. Indeed, if the wood autonomy of the boiler is a function of the volume of the combustion chamber of the solid fuel, it is not the same for some coals, since it is not possible to fill the combustion chamber like this can be done in the case of wood, especially if the coal is swelling.

Several automatic feeding systems are known for coal-fired boilers, in particular systems using tappets. However, it turns out that the construction of a compact multi-fuel boiler capable of operating with good efficiency, in which the water circuit is common to the two combustion chambers, a common outlet conduit also serving for the evacuation of fumes from these two combustion chambers and which is capable of operating with a large autonomy whatever the type of fuel used, poses many problems that are still poorly or even unsolved. It quickly turns out that there are several incompatibilities between the architectural requirements on the one hand and optimal performance on the other. This apparently explains the fact that such boilers are devoid of a coal supply, so that the autonomy of the boiler varies very significantly depending on whether it is supplied with liquid or gaseous fuel, wood or coal. In the latter case in particular, this autonomy cannot exceed a few hours and provided that they are coals of the coke or anthracite type. The addition of a coal storage hopper comes up against a space issue as well as the mode of supplying the combustion chamber. The ali the simplest statements are made by gravity, however the quality of combustion depends on the type of coal burned. Furthermore, such a feed can only allow the formation of an elongated pile, the longitudinal axis of which is parallel to the distribution opening of the hopper. However, the longitudinal direction of the pile of coal on the hearth must be parallel to the heat exchanger if we want the hot combustion gases to be distributed evenly over the entire exchange surface, to obtain a good efficiency of heat exchange.

In the case of a compact polycombustible boiler, the solid fuel combustion chamber and the hopper must be adjacent to a common partition so that the coal is deposited parallel to this partition and the heat exchanger and the water circuit are located towards the wall opposite this partition. Considering that the hearth of the solid fuel combustion chamber must be below the output level of the hopper, it makes sense to use the free volume located under the hopper for the combustion chamber of the liquid fuel . Consequently, it is obvious that it becomes difficult to interconnect the water circuit of the two exchangers and to bring together at a common smoke outlet the fumes leaving the two exchangers associated with the respective combustion chambers.

It is noted that the development of such a boiler, capable of a large autonomy, of burning different fuels in good conditions and of obtaining a good heat exchange efficiency while occupying a relatively small volume, poses problems. quite complex. This tends to explain the reason why, in boilers of this type, the question of automatic storage and distribution of coal has been avoided. However, the public has contracted certain habits with boilers with liquid or gaseous fuel, in particular that of a great autonomy and it is obviously difficult to completely lose these advantages, from where the need which is felt to increase the autonomy solid fuel boilers especially when combined with fluid fuel boilers.

The solid fuel combustion chamber must not only be able to burn anthracite but also tanks good bituminous oils which swell on burning, agglomerate and form a crust on the surface. Such coals in particular must be burned in a thin layer. The importance of being able to burn this type of coal comes from the fact that the reserves of anthracite decrease and that there are still enormous quantities of bituminous coals which were less sought after as long as the anthracite was available in sufficient quantity and especially as long as fuel was cheap. In addition to the above-mentioned requirements relating to multi-fuel boilers, the supply device must make it possible to distribute the coal in a relatively thin layer provided that consideration is given to burning swelling coals, whether or not the combustion chamber of the solid fuel is combined with a multi-fuel boiler.

The purpose of the present invention is to provide a solution capable of responding to all of the above-mentioned problems.

To this end, the subject of the invention is a multi-fuel boiler comprising a casing containing a combustion chamber for solid fuel and a combustion chamber for liquid or gaseous fuel, these two combustion chambers having two respective heat exchangers, the water circuits are connected to each other, and whose smoke circuits are connected to a common smoke evacuation, a vertical partition extending between the front and rear walls of the casing by dividing it into two compartments, one is occupied by the solid fuel corbustion chamber and the other by the liquid fuel combustion chamber. This boiler is characterized in that the heat exchanger of the solid fuel combustion chamber is located near the rear wall of the casing, a horizontal partition dividing the other compartment into two upper and lower compartments, this the latter receiving the combustion chamber of liquid or gaseous fuel with a burner integral with the front wall of the casing and its heat exchanger having a smoke outlet on the side of the rear wall of this casing, while the upper compartment is occupied by a coal storage hopper associated with a distributor communicating with the combustion chamber of the solid fuel, associated with means for discharging the coal parallel to said heat exchanger.

• La fig. l est une vue en coupe de face de cette chaudière.
• La fig. 2 est une vue en coupe selon II-II de la fig. l.
• La fig. 3 est une vue en coupe selon III-III de la fig. 1.
• La fig. 4 est une vue en coupe selon IV-IV de la fig. l
• La fig. 5 est une vue de détail agrandie de la fig. 4.
• La fig. 6 est une vue en élévation de la fig. 5.
• La fig. 7 est une vue d'une variante de la fig. 1.
• La fig. 8 est une vue selon VIII-VIII de la fig. 7.

The appended drawing illustrates, schematically and by way of example, an embodiment and a variant of the boiler and of the distributor object of the invention.

• Fig. l is a front sectional view of this boiler.
• Fig. 2 is a sectional view along II-II of FIG. l.
• Fig. 3 is a sectional view along III-III of FIG. 1.
• Fig. 4 is a sectional view along IV-IV of FIG. l
• Fig. 5 is an enlarged detail view of FIG. 4.
• Fig. 6 is an elevational view of FIG. 5.
• Fig. 7 is a view of a variant of FIG. 1.
• Fig. 8 is a view along VIII-VIII of FIG. 7.

The multi-fuel boiler illustrated in figs. 1 to 4 comprises a combustion chamber 1 for solid fuel, a cylindrical combustion chamber 2 for fuel or gas and a storage hopper 3 for coal. The whole is included in a parallelepipedic casing 4. The combustion chamber 1 of the solid fuel occupies a little more than half of the interior volume of the casing 4 and extends over the entire height of this volume between the front 5 and rear 6 walls. of this housing. The rest of this volume is distributed between the storage hopper 3 and the cylindrical combustion chamber 2 arranged one above the other. Each of these combustion chambers 1 and 2 is surrounded by a porticn 7 respectively 8 of a common water circuit having an inlet 9 and an outlet 10. The two portions of this circuit communicate with each other by a vertical connection portion 11, which at the same time forms the partition separating the storage hopper 3 from the combustion chamber 1 of the solid fuel.

A heat exchanger 12 with vertical water blades extends adjacent to the part of the rear wall 6 of the casing 4 closing the bottom of the combustion chamber 1. The circulation of smoke through this exchanger 12 leads to a duct for outlet 13 intended to be connected to a chimney. A heat exchanger 14 extends around the combustion chamber 2 and provides a gas inlet 15 located at the front of this chambre while a manifold 16 located at the rear conducts the cooled gases to the outlet conduit 13. A partition 17 diametrically separates this outlet 13 to prevent the smoke from one exchanger from entering the other exchanger.

A gas / fuel burner 18 (fig. 2) is mounted in an opening in the front wall 5 of the casing 4. It is noted that the combustion chamber 2 is not in direct contact with the water circuit so that the walls of this combustion chamber are not directly cooled. It is therefore a hot combustion chamber capable of developing significant power compared to its volume, leaving a maximum of space for the hopper and for the combustion chamber 1 of the solid fuel.

The latter communicates with the storage hopper through an opening 19. A door 20 (fig. 3) formed at the top of the front wall 5 of the casing 4 serves to fill the combustion chamber 1 with wood. The bottom of this chamber has an inclined grid 21 at variable angle formed by two parts 21a, 21b hinged to one another. The least inclined part 2la is adjacent to a vertical stop 22 located at the end of a grid 23 on which a block 24 of refractory material is placed. This grid has the particularity of being able to be turned over so as to retract the stop 22 below and to form a hearth for burning wood. In this position the block 24 is simply removed. The vertical stop 22 serves to retain the carbon on the part 2la of the grid which forms a hearth.

It should be noted that different air intakes are provided depending on whether one burns coal or wood. In both cases, primary air is called to pass through the burning materials through the grid 21 in the case of coal and through the grid 23 in the case of wood. To complete these primary admissions, secondary air is admitted through the openings A ₁ in the case of coal combustion. This air admitted through these openings A ₁ can also serve as tertiary air in the case of wood combustion. An opening A _{2 is} used for the admission of secondary air for the combustion of wood and of tertiary air for that of coal.

The lower edge of the opening 19 formed at the base of the hopper is located at a horizontal distribution surface 25 which runs along the internal face of the part of the front wall 5 of the casing 4 which extends in front of the chamber combustion 1. The width of this distribution surface 25 corresponds to that of the opening 19. A deflector 26 (FIG. 4) is disposed at an angle at the end of this distribution surface.

A device for distributing the coal contained in the storage hopper 3 is placed under this hopper, in the space left free by its inclined bottom (FIGS. 5 and 6). This device comprises a pusher 27 to which is fixed a sheet 28 adjacent to the distribution surface 25. An adjustment guillotine 29 serves to vary the passage section of the opening 19. The pusher 27 is integral with a drive tab 30 drilled and provided with a threaded sleeve 31 engaged with a drive screw 32 fixed to the output shaft of a gear motor 33.

A comb 34 (fig. 3 and 5) is mounted oscillating around an axis 35 parallel to the grids 21. This comb is used for ash removal as well as for breaking the crust which is formed during the 'combustion of bituminous coal in particular. The actuation of this comb can be done either manually using an actuating lever 36 or automatically at a given frequency by means of the pusher 27. For this purpose, a transmission member 37 constituted by a lever bent articulated to a vertical axis 38 is engaged by one of its ends with a pin 39 secured to the pusher 27 and by its other end with a connecting member 40 articulated to a sleeve 41. This sleeve is slidably mounted on a rod 42 of control of a rack 43 engaged with a pinion 44 fixed on the shaft 35 for controlling the comb 34.

The sleeve 41 and the rod 42 both have a transverse bore 45 which are brought to coincide in an axial position of the sleeve 41 corresponding to the withdrawal position of the pusher 27. An electromagnet 46 is fixed to the sleeve 41 and has a core mobile intended to engage in the holes 45 to make the rod 42 integral with the sleeve 41 so as to impart an oscillating movement to the comb 34. The purpose of this disengageable mechanism for driving the comb 34 is to allow manual control of this comb on the one hand and the automatic actuation of this comb at a frequency slower than the actuation frequency of the pusher 27 on the other hand.

When the boiler is used with a liquid or gaseous fuel, this fuel is brought to the burner 18 of the combustion chamber 2. The gases burned in this chamber heat its wall red since it is not cooled directly so that combustion is co-complete. Hot gases enter the longitudinal channels of the heat exchanger 14 through the inlet 15 and transfer their calories to the water circuit 8 surrounding the exchanger. These cooled gases exit at the rear of the chamber 2, are collected by the manifold 16 and reach the chimney through the outlet opening 13. The supply of the burner with liquid fuel is carried out using a pump. (not shown) used in all oil burners.

For coal heating, you must first fill the storage hopper 3 and turn on the push coal dispenser 27. This is programmed according to a given power to perform back-and-forth movements. comes at a certain frequency. On each actuation of the pusher 27, a certain quantity of charcoal is pushed onto the distribution surface 25. In the event that this is still empty, each actuation of the pusher 27 pushes a new dose of charcoal which itself pushes the doses introduced previously until the entire distribution surface 25 is saturated. Of course, during the start-up phase of the combustion chamber 1, the actuation of the pusher 27 can be carried out continuously until the quantity of coal is sufficient. When the distribution surface is saturated, the coal falls in rain on the grid 21b and descends on the grid 2la until it is stopped by the abutment surface 22 (fig. 3). The deflector 26 is intended to distribute the coal uniformly along the grid 21 so as to obtain a regular layer of burning coal extending parallel to the exchanger 12, guaranteeing the production of heat regularly distributed over the entire surface of the exchanger, resulting from homogeneous combustion.

The advantages of the coal dispenser according to the invention are numerous. In the case of a multi-fuel boiler, it makes it possible to form a layer of carbon extending transversely to the storage hopper so that the heat exchanger 12 can occupy the rear wall (6) of the combustion chamber 1. This device facilitates the common evacuation of the fumes from the two combustion chambers 1 and 2 and above all allows the production of a water circuit 7, 8 common to these combustion chambers without any particular difficulty of realization. Regardless of these more specific advantages to multi-fuel boilers, this coal distributor of fre the advantage of allowing a distribution of the coal not by gravity or by displacement of the heap of glowing charcoal as it burns, but by dumping metered quantities of charcoal on all the surface of the heap of glowing charcoal of so as to perfectly control the thickness of the layer and to make the coal fall in rain on this layer as it burns. This control of the thickness of the coal layer is important in particular for burning swelling coals as well as for promoting the combustion of the coals by natural draft. These properties could obviously be used for any self-feeding coal combustion chamber.

The automatic actuation of the comb 34 following the engagement of the sleeve 41 and the rod 42 by the electromagnet 46 makes it possible to evacuate the ashes through the grid 21 and to break the surface crust which is formed in particular when bituminous coal is burned. The frequency of the automatic actuation of this comb can be chosen from among the multiples of the actuation frequency of the pusher 27. In general the frequency of the pusher is too fast for the comb since it is useless to stir the layer incandescent too often and this can even be harmful, producing some loss of incompletely burned charcoal in the ashtray. This is why the coupling mechanism by electromagnet has been provided. The action of this comb promotes the formation of a layer of carbon of regular thickness and, by breaking the crust that can form a bituminous coal and by evacuating the ashes, it facilitates the aeration of this layer by the natural draft of the fireplace.

The combustion chamber 1 for solid fuel has been illustrated as a function of the use of coal as has already been mentioned previously, a slight transformation must be carried out for the use of wood. The grid 23 must be turned over to place the vertical stop 22 below the grid 23 and thus allow the grid to form the hearth for the wood, this hearth being below the exchanger 12 so that the rest of the combustion chamber 1 constitutes a voluminous reserve of wood. Of course, in this use, the comb 34 is held in the raised position. Thanks to this arrangement, the wood reserve is maintained at a temperature lower than the combustion temperature, the hot gases rising directly from the hearth in the exchanger 12. The wood descends as combustion proceeds, limited to the hearth.

The embodiment which has just been described has been designed to allow the addition of a hot water tank superimposed on the boiler. For this purpose, the top of the boiler is left entirely free. This design obviously assumes that a cleaning hatch 47 is provided on the side of the heat exchanger 12. Consequently, the side wall of the casing 4 of the boiler having this hatch must be placed at a certain distance from a wall . This can be annoying and can cause interest to be lost in this boiler which, although compact, thus presents a relatively large bulk.

The variant of figs. 7 and 8 shows another design of this boiler in which the plate exchanger 12 is replaced by a tubular exchanger 48 which has a collector 49 at its upper end closed by a removable plate 50 of a sweeping hatch. The combustion gas outlet is provided by a vertical duct 51 projecting laterally outside the casing and extending to the level of a passage 52 formed behind the tubular exchanger 48 and serving to connect the manifold 16 located behind the combustion chamber 2 at the chimney. This vertical smoke outlet also makes it possible to arrange the rear face of the boiler against a wall, which is not always possible with a horizontal outlet unless the chimney can be opposite. In any case, the vertical outlet generally allows more flexibility in the connection to the chimney than the horizontal outlet.

The design of the tubular exchangers 48 is advantageous insofar as it allows the exchange surface to be varied by closing certain channels. Thus, thanks to the coal distributor described, it is possible for the same boiler to modify the power by increasing or decreasing the supply frequency of the pusher 27. At the same time, a more or less long combustion chamber 2 can be put in place. ; indeed, we see for example in FIG. 8 a combustion chamber intended for a lower power boiler ble as that of fig. 2. This flexibility of adaptation has obvious advantages in terms of manufacturing, allowing further rationalization. On the user side this also offers advantages since this boiler allows, at low cost, an adaptation to changes in the living space of a house.

The boiler described in one or other of these variants allows autonomy at medium speed, much higher than the standards in force.

Claims (4)

1. Multi-fuel boiler comprising a casing containing a combustion chamber for solid fuel and a combustion chamber for liquid or gaseous fuel, these two combustion chambers having two respective heat exchangers, the water circuits of which are connected to one another. other and whose smoke circuits are connected to a common smoke evacuation, a vertical partition extending between the front and rear walls of the casing dividing it into two compartments, one of which is occupied by the fuel combustion chamber solid and the other by the liquid fuel combustion chamber, characterized in that the heat exchanger of the solid fuel combustion chamber is located near the rear wall of the casing, a horizontal partition dividing the '' other compartment in two compartments, upper and lower, the latter receiving the combustion chamber of liquid or gaseous fuel with a solidaire burner e of the front wall of the casing and its heat exchanger having a smoke outlet on the side of the rear wall of this casing, while the upper compartment is occupied by a coal storage hopper provided at its base with a communicating distributor with the combustion chamber of the solid fuel, associated with means for discharging the coal parallel to said heat exchanger. 2. Boiler according to claim 1, characterized in that the bottom of the hopper is inclined relative to said horizontal partition leaving a space occupied by an actuating mechanism of said distributor. 3. Boiler according to claim 1, wherein said distributor comprises a pusher with a horizontal trajectory disposed at the bottom of the hopper, a lateral opening for this pusher and means for alternately driving this pusher between two positions located on either side of this lateral opening, characterized in that this lateral opening is located at a distribution surface running along the front vertical face of the part of the casing delimiting the combustion chamber of the solid fuel and extending longitudinally above the hearth of this combustion chamber, parallel to the direction of movement of the pusher, the width of this distribution surface corresponding substantially to that of said lateral opening. 4. Boiler according to claim 3, characterized in that a deflector extends over at least part of the distribution surface and gradually reduces its width towards the end of this surface opposite to said opening.

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