FR2522781A1 - Solid fuel boiler control - has open top hearth with bottom feed tube controlled by level detector - Google Patents

Abstract

The combustion, feed and control system is for a boiler burning solid and homogeneous fuel in bulk. It incorporates a combustion hearth (19) mounted inside the boiler (1) and with an open top (25), while the bottom (21) is formed by a feed tube (22) connected to it. A tube (32) injecting primary air into the hearth is supplied by a fan (36) outside the boiler and operating under the control of a temperature detector. Secondary air openings are formed in the hearth below the open top, while a detector for the level to which the hearth is filled with fuel controls operation of the feed tube.

Description

 The present invention relates to the means used in the boilers to ensure the combustion, the supply and the combustion regulation of a bulk, solid and homogeneous fuel.

By solid and homogeneous solid fuel, it is necessary to understand those constituted by natural fragments of small particle size, in particular of coal or else fragments reconstituted from fuels of pulverulent pulp, such as the granules obtained by compression, compaction or extrusion of sawdust. of wood with or without the presence of a binder.

 The invention relates, more particularly, to a combustion assembly for a heating boiler of a liquid coolant vehicle, such as water or oil, intended to heat premises by means of radiators with permanent circulation. maintained or intermittent.

 In the above field of application, it is known to operate boilers with combustion stoves in which are placed fragments of coal, of uniform particle size, or granules, such as those based on sawdust.

 Such fireplaces can periodically receive a load of solid, homogeneous bulk fuel or, on the contrary, be fed intermittently by an automatic device taking fuel from a storage hopper.

 The first mode of supply does not allow flexible and regular operation and represents a significant constraint for the personnel responsible for driving the operation of such a boiler.

 The second feeding method eliminates the above drawbacks and should therefore be satisfactory.

 However, it can be seen that the operating speed of a boiler is determined on average by the frequency of intermittent supply and the fuel load delivered for each successive supply phase. Consequently, this results in operation / admittedly relatively regular, but which cannot adapt to variations in demand corresponding, for example, to the instantaneous commissioning of a certain number of additional radiators or to a sudden variation outside temperature.

 In any case, it is also conceivable that, if there was a regulation of this supply, this would not necessarily result in a rapid adaptation of the operating speed of the boiler according to demand, given the time elapsing necessarily between the arrival of an additional charge of such a fuel and its combustion state capable of modifying the operating speed of the boiler.

 The present invention aims to remedy the above drawbacks by proposing a new combustion, supply and regulation assembly making it possible to adapt, quickly and efficiently, the operating speed of a boiler and, consequently, the calories it provides Depending on the demand from a bulk, solid and homogeneous fuel.

 An object of the invention is to provide a combustion, supply and regulation assembly which is in the form of a unitary device which can be quickly adapted to any existing boiler, without requiring any modification of its structure or that of the boiler.

 Another object of the invention is to propose a new set of combustion, supply and regulation of particularly simple and robust design and which can be produced at an attractive cost price.

 Another object of the invention is to propose a new set of combustion, supply and regulation, which can be adapted to the power of a given boiler by simple adaptation of its constructive characteristics.

To achieve the above goals, the assembly of com bastion, supply and control for solid fuel boiler, solid and homogeneous, is characterized in that it comprises
- a combustion hearth intended to be placed inside
laughing of a boiler, having an open top and
the bottom of which consists of a feed tube
with whom he communicates,
- at least one injection pipe in said focus
primary activation air produced by a fan
lator located outside the boiler and of which
the operation is placed under the dependence of a
temperature sensor*
- secondary air passage openings
in the fireplace below the open top,
- a fuel filling level detector
of the fireplace controlling the operation of the supply tube
mentation.

 Various other characteristics will emerge from the description below made with reference to the appended drawings which show an embodiment of the object of the invention.

 Fig. 1 is a schematic sectional elevation of a boiler equipped with an assembly according to the invention.

 Fig. 2 is a cross section taken, on a larger scale, along the line II-II of FIG. 1.

 Fig. 3 is a plan view taken, on a larger scale, along the line III-III of FIG. 1.

 Fig. 1 shows a boiler 1 comprising an outer casing 2, elongated, of generally horizontal axis, closed at its two ends by two walls 3 and 4. The wall 3 supports a soot box 5 comprising an upper sleeve 6 for connection with a conduit 7 chimney.

 The envelope 2 contains, internally, a jacket 8, for example of the cylindrical type, comprising a bottom 9 and an open end 10 passing through the wall 4 of the envelope 2. The open end 10 can be closed by a door 11, of any suitable type, for example articulated on hinges not shown.

 The jacket 8 and the casing 2 together delimit a capacity or annular enclosure 12, filled with a heat-transfer fluid which can be caused to circulate in the direction of an exchange installation, such as a central heating installation, by outgoing and returning pipes 13 and 14.

 The jacket 8 delimits, inside the envelope 2, a combustion chamber 15 which is connected to the soot box 5 by means of smoke ducts 16 contributing, possibly also to ensure the maintenance and immobilization of the shirt 8 inside the envelope 2.

 Circulation tubes 17 pass through the interior part of the jacket 8 to open into the enclosure 12. These tubes 17 together form, as it were, a sole 18 making it possible to support, directly or in combination with a mesh grid, bulk fuel, heterogeneous in nature, such as coal or wood logs.

 The object of the invention is to provide a combustion, supply and regulation assembly for supplying a boiler, as described above, with a bulk, solid, homogeneous fuel of small particle size. , consisting of calibrated fragments of coal or, again, of pellets reconstituted from combustible materials such as sawdust.

 According to the invention, the assembly comprises a combustion hearth 19 intended to be placed in the chamber 15 bearing directly on the hearth 18 formed by the tubes 17 or, again, suspended from a support structure 20 forming part of the jacket 8 and shown in phantom in FIG. 1.

 The hearth 19 rises from a feed tube 21 intended to pass through the door 11 and to connect the hearth 19 to a hopper for storing bulk fuel, not shown. The feed tube 21 is, preferably constituted by the sheath of an endless feed screw 22 driven in a known manner by an electric motor.

 Preferably, the tube 21 represents, at least in part, the bottom of the hearth 19 which is delimited by two transverse walls 23 connected to each other by two longitudinal walls 24 connected to the bottom 22. The transverse walls 23 are, preferably , flat, while the longitudinal walls, parallel to the axis of the tube 21, comprise two parts 24a forming a divergent with respect to the section of the bottom 22 and two flat parts 24b extending substantially vertically.

 The walls 23 and the parts 24b together define an open top 25 and carry, in the plane of this top, a substantially flat head frame 26. The frame 26 extends beyond, on either side of the vertical plane of each of the walls, towards the inside and the outside of the hearth. The head frame 26 comprises, in its part projecting outwards, holes 27 whose function appears in the following.

 The flat and substantially vertical parts 24b have lights 28 of vertical direction intended to establish communication between the internal volume 29 of the hearth and the chamber 15.

 The parts 24a internally carry distribution deflectors 30 which are constituted by wall segments or wings. The height of these deflectors decreases progressively from the connection section between the tube 21 and the hearth 19, in order to delimit a passage section progressively increasing in the direction of the opposite transverse wall 23 (FIG. 3). The deflectors 30 are preferably flat and oriented in the direction of one another, defining a convergence angle preferably between 120 and 150. The re-entrant angular parts defined by the upper faces of the deflectors 30 and the parts 24a are preferably occupied by two ignition means 31 which can be constituted by electrical resistances.

 The longitudinal walls 24 carry two tubes 32 which can be attached internally or be an integral part of the structure of the longitudinal walls. The pipes 32 extend parallel to the axis of the supply tube 21 and have, in their walls, a continuous slot or a series of holes 33 oriented towards the inside of the volume 29 while being located at a level below that of the base of the lights 28. The tubes 32 are connected, outside the hearth 19, to a distribution box 34, the inlet of which is connected, by a sheath 35, to the outlet of a fan 36, the operation of which is placed under the control of a temperature probe. In the example considered, the temperature probe is, for example, formed by a sensitive element appreciating the temperature of a living room.

 The hearth is, moreover, associated with a filling level detector 37 intended to control the operation of the supply tube 21 and, in this case, the rotation by an electric motor of the screw 22. The detector 37 is formed by a probe 38, such as a grid, a frame, a panel, openwork or solid, the dimensional characteristics of which are compatible with the opening made by the head frame 26. The probe 38 is carried by a lever 39 capable of pivoting in at least one bearing 40 carried by the head frame 26 and oriented parallel to the axis of the tube 21.The lever 39 passes through the door 11, beyond which it comprises an end portion 41 actuating a housing 42 comprising electrical contactors controlling the energization of the motor for rotating the screw 22 and various safety members.

 Preferably, the probe 38 is mounted so as to be able to pivot on the lever 39 along an axis perpendicular to that defined by the bearings 40.

 The assembly described above operates in the following manner.

 From the state according to fig. 2, the detector 37 controls the tensioning of the supply tube 21, so that the rotation of the screw 22 brings loose, solid and homogeneous fuel into the hearth 19. The supply which is thus carried out has the result progressive filling, by raising the level of fuel in the volume 29. The wall segments 30, taking into account their variation in height, ensure a distribution of filling over the entire useful length, in order to obtain a substantially regular level. The filling is carried out in this way until the moment when the probe 38, urged in the direction of the arrow f1, controls, by the housing 42, the interruption of operation of the motor for driving the rotation of the screw 22. In this state, the filling level N is, for example, that determined in dashed lines in FIG. 2. The ignition of the mass of fuel contained in the hearth is carried out by the means 31. The relative position of these means 31 makes it possible to avoid any risk of deterioration resulting from the elevation of the fuel in the hearth 19.

 In consideration of a normal operating state, in which the increase in power of the boiler has been carried out to confer the desired temperature on the heat-transfer vehicle, the combustion of the fuel is carried out from the upper layer over a thickness which is determined by the height of the lights 28.

In fact, the latter allow the circulation of secondary air passing through the door 17 via an adjustable register 43.

This results in a progressive continuous combustion of the thickness of fuel concerned and corresponding to the zone of active influence of the lights 28.

 As the combustion progresses, the level N tends to drop, which causes the detector 37 in the direction of the arrow f2. When this detector reaches the minimum level, the lever 40 controls the housing 42 which restores the supply of the worm screw 22 to ensure the supply of a new charge of fuel, in order to complete the filling level at the interior of fireplace 19.

 It should be noted that, during the operating phase, as above, the stress exerted by the fuel charge inside the hearth 19 is partly taken up or supported by the wings 30. This results in a reduction of the vertical stress supported by the screw 22 which can thus be driven in rotation, in a regular manner to contribute to a progressive and precise filling of the useful volume 29 of the hearth 19.

It should also be noted that any risk of possible overflow of the fuel, as a result of the expansion following combustion, is combated by the head frame 26. In fact, any spillage or overflow from the level superior
N, brings the fuel fragments or granules bearing on the frame until the moment, after complete combustion, the resulting ashes are naturally poured out through the openings 27 into an ashtray 44 placed under the hearth 18.

 Insofar as, during continuous operation, as described above, it is necessary to increase the operating speed of the boiler, in we for example to meet a higher demand, the probe sensitive to the subsequent drop in reference temperature controls the powering up of the fan 36. The pulsed air thus supplied borrows the sheath 35, the distributor 34 and the pipes 32 which ensure its distribution and distribution in the fuel mass below the layer of burning embers. This results in an activation of the combustion which progressively interests the lower and lower layers, thereby providing an excess of calories which can be transmitted to the heat transfer vehicle occupying the enclosure 12.

 As this activation of the combustion leads to a lowering of the filling level, the detector 37 operates as said previously, in order to supply the screw 22 with additional fuel filling.

 As is apparent from the above, the assembly according to the invention makes it possible to ensure continuous regular combustion of a solid, homogeneous bulk fuel, to adapt the operating speed of the boiler as a function of calories to be produced to meet demand and to control the automatic supply of the combustion furnace from a storage hopper arranged outside the boiler.

 In addition, the constructive arrangement of the assembly makes it possible to obtain a combustion regularly distributed over the entire useful surface of the hearth, in order to obtain a layer of substantially constant thickness, ie in slow combustion, through the openings 28 , or in activated combustion, under the action of the primary air delivered by the pipes 32.

 The object of the invention can be easily adapted to the powers of the boilers to be equipped by providing for modifying the length of the hearth. It can also be provided to equip large power boilers with two or more assemblies as described above.

 According to another arrangement of the invention, provision is made to impart, to the part of the screw 22 close to the transverse wall opposite the door 11, a fraction of helicoid 22a of opposite pitch, in order to avoid any risk of solid fuel stuffing delivered in the useful volume 29.

 The housing 42 can be provided to control the operation of the supply tube 21 for a determined maximum duration, in order to interrupt such operation when, for example, the storage hopper is empty.

 The housing 42 can also be used to ensure, for example, the injection into the tube 21 and all the hearth 19 of an extinguishing product, such as water, in the event of abnormal operation and overheating of the hearth, as well as possible combustion inside the tube 21 appreciated by at least one detector internal to the boiler.

 Another advantage of the invention resides in the particular construction of the detector 37, the probe 38 of which is articulated to pivot along an axis perpendicular to that of the pivoting of the lever 39 carrying it. In this way, it becomes possible to take account of an irregular level N of filling, in the longitudinal direction of the hearth, before controlling the pivoting of the lever responsible for the control by the housing 42 of the stop of operation of the tube d food 21.

 The invention is not limited to the embodiment shown and described in detail since various modifications can be made without departing from its scope.

Claims (11)

 1 - Combustion, supply and regulation assembly for a solid, homogeneous fuel boiler, characterized in that it comprises  - a combustion hearth (19) intended to be  placed inside a boiler (1),  having an open top (25) and the  bottom (22) consists of a feed tube  tation (21) with which it communicates,  - at least one tube (32) for injection into  said focus of a primary activation air pro  supplied by a fan (36) arranged ex  inside the boiler and which works  ment is placed under the control of a probe  of temperature,  - openings (28) for secon air passage  daire provided in the foyer below the  open top,  - a filling level detector (37) in  fuel from the stove controlling it works  feed tube.  2 - assembly according to claim 1, characterized in that the hearth (19) rises from the opening of the supply tube (21) and comprises a bottom (22) formed at least in part by said tube, two transverse walls (23) and two longitudinal walls (24) defining a divergent therebetween.  3 - assembly according to claim 2, characterized in that the hearth (19) comprises two divergent walls (24a), extended by wall portions (24b) substantially vertical leading to the open top (25) and in which are formed slots (28) vertical orientation representing the openings for the passage of secondary air supplied by the boiler register.  4 - Assembly according to one of claims 1 to 3, characterized in that the hearth (19) comprises two pipes (32) for primary air injection defining an injection level towards the interior of the hearth located below openings (28) for secondary air passage.  5 - Assembly according to one of claims 1 to 4, characterized in that the hearth (19) has an open top (25) bordered by a frame (26) of generally horizontal planar shape, projecting inwards and towards the outside of said hearth and having openings (27) formed in its part projecting outwards.  6 - assembly according to one of claims 1 to 5, characterized in that the hearth (19) comprises deflectors (30) distribution placed on the internal faces of the longitudinal walls (24) in a direction substantially parallel to the axis bottom (22) and supply tube (21).  7 - assembly according to claim 1, characterized in that the filling detector (37) consists of a feeler (38) formed by a flat structure mounted at the end of a lever (39) pivoting on an axis parallel to the axis of the supply tube and actuating contactors for controlling the operation of the supply tube.  8 - assembly according to claim 7, characterized in that the detector (37) is constituted by a flat probe (38) carried by the lever (39) and capable of pivoting relative to the latter on an axis perpendicular to that of pivoting lever.  9 - assembly according to claim 7 or 8, characterized in that the filling detector (37) is carried by the frame (26).  10 - assembly according to claim 1, characterized in that the supply tube (21) comprises an endless screw (22) extending in the part of the tube forming the bottom of the hearth and whose internal end to this hearth includes a helicoid part (22a) of no opposite.  11 - assembly according to claim 1 or 6, characterized in that the hearth (19) comprises two means (31) for ignition placed parallel to the distribution deflectors (30).