FR2490320A1 - Furnace for compressed straw bales - has ash rake with scrapers for discharge through combustion chamber floor - Google Patents

Abstract

The furnace has a combustion chamber (4) which has a vertical panel separating it from the fuel feeder located over the ash collector (6). The secondary combustion air is admitted through an opening (2) in the rear panel (5) of the furnace. The exhaust gases pass through a heat exchanger (16) mounted over the combustion chamber. The ashes are raked by revolving arms (9) fitted with prongs. There is a base between the combustion and collecting chambers with a groove for the discharge of cinders and to induce the primary air.

Description

 Heating boiler for burning straw bales, especially compressed bales.

 The subject of the invention is a heating boiler for the combustion of straw bales, in particular of compressed bales, comprising a combustion chamber, the vertical front wall of which has a fuel supply opening disposed above a collecting chamber. ash, the fuel supply opening being supplied by means of a closed fuel supply duct and provided with transporting members, at least one secondary air opening being provided in the rear wall of the combustion in front of the fuel supply opening, a flue gas heat exchanger being arranged above the combustion chamber.

 Such heating boilers are known from document DE-OS 24 00 778. In this case, it is a hearth for a household waste combustion installation in which the fuel packets are simply introduced into a well. free of grate or bottom, using conveyors, in front of an additional combustion burner. This known principle of hearth arrangement cannot be applied directly for compressed bales of straw.

 However, even when slowly introducing bales of compressed straw in continuous succession into the hearth at the rate of their combustion, it is practically impossible to obtain regular combustion. The reason is that, for its combustion, compressed straw behaves entirely differently from waste materials (household waste) in general and even from uncompressed straw.

 With an additional burner, as in the case of the object of the document DE-OS mentioned, to burn the straw compressed by a conveyor screw and which arrives at the mouth of the gallery of the conduit, it is immediately understandable that this would cause a gallery light impossible to stop in the supply duct and that there would not occur an incandescent zone essential for permanent and, as far as possible, uniform combustion.

 If, on the other hand, the combustion were allowed to proceed by itself in the straw, the whole of the vertical incandescent zone would descend or, as experience 11a shown, this zone would become more or less encrusted complete due to the minerals normally found in straw. This would interrupt the automatic continuation of proper combustion.

 Consequently, the object of the invention is to improve a heating boiler for the tee 1 indicated in the preamble in order to obtain the most regular combustion zone possible over the entire front surface of the straw bale arriving at combustion. In addition, ash must be removed from the combustion zone, ensuring that the incandescent combustion zone is not disturbed.

 To this end, the invention relates to a heating boiler of the above type, characterized in that a horizontal bottom is provided between the combustion chamber and the ash collecting chamber, this bottom having along the rear wall of the combustion chamber a slot for the removal of ash and the supply of primary air, and in that an ash scraper member movable in a vertical plane in front of the combustion zone is provided above the slot.

 Provisions indicated below allow to obtain. advantageous embodiment nodes of the invention.

 It has been found that, on the one hand, the primary air supply from the slot on which the combustion zone of the ball is located e, on the other hand, the central secondary air directed towards the center of the combustion zone guaranteed uniform combustion of the front surface of the ball.

Simultaneously, by the ash scraper constantly moved immediately in front of the combustion zone, it is ensured that these ash formed and tending to stay in place are scraped and that the incandescent combustion zone is thus accessible for the necessary combustion air. .

 It is also essential that the entire bottom of the combustion chamber is not simply arranged in the form of a grid as is usual, but that the primary air cannot essentially sweep the ball portion located in the combustion chamber. than in the area of the front surface in uniform incandescent combustion. In this regard, it is however possible to provide a grid covering the entire surface of the bottom, this grid then being covered or masked, except as regards the slot, for the combustion of compressed bales of straw.

 It is advantageous that the secondary air openings are combined with the movable ash scraper member, so that, for the movement of the ash scraper member, the latter is mounted on a hollow shaft of sufficient dimensions so that 1 secondary air can flow through it, this flow can, if necessary, be assisted by a fan arranged upstream. The hollow shaft is driven in slow rotation, outside the combustion chamber, by an appropriate drive control, the direction of this rotation being able to change at predetermined time intervals.

 The "mobility" of the ash scraper member can also be advantageously provided also in the axial direction, namely in opposition to the thrust of an elastic support disposed outside. If the combustion speed and the fuel advance speed are not identical, such a device can also be used at the same time as a pulse generator to modify the advance speed.

 By the arrangement with a hollow shaft and the supply of secondary air by this hollow shaft, it is also advantageously obtained, on the one hand, that the ash scraper member undergoes cooling and, on the other hand, the secondary air, on the other hand, is preheated.

 So that the combustion zone is well maintained, it has also proved advantageous to have elements in the corners of the combustion chamber reducing its section and thus acting on the fuel to compress it. These elements are in particular to be considered when round bales must be burned, as will be explained more precisely in the following. They can be provided without difficulty, for example, during the shaping of masonry. The best and simplest arrangement of these compression elements as well as their most judicious arrangement are obtained when they are in the form of funnels, of which however only the upper part is still sufficiently wide.

The bales are thus compressed in a "round shape" before the combustion zone and shaped, so to speak, to the shape of the ash scraper member.

 Without such an arrangement, incandescent angle zones would form on the balls which would burn much less quickly than the zones immediately in front of the scraper member.

 When the compressed straw starts to glow, it is usually pasty. By means of the ash scraper member, the particular embodiment of which will be described in detail below, the speed of combustion is favored and the ashes are constantly removed from incandescent pieces of straw.

 The entire cross-section of the combustion chamber can be designed to receive several bales or extremely large compressed bales simultaneously. Depending on the size of this section, it is of course possible to provide several ra ra ashes bodies distributed in a sa1nl-trique around the centrE.

The invention will be better understood with reference to the description below and the appended drawings representing examples of embodiment of the invention, drawings in which
- Fig. 1 is a view in longitudinal section of a heating boiler provided with a hearth.

 - Fig. 2 is a front elevation view of the ash scraper member.

 - Fig. 3 shows on a larger scale the part of the hearth in which the ash scraper member is disposed.

 - Fig. 4 shows a particular embodiment of the hearth without the ash scraper element.

 - Fig. 5 is a view of the hearth from the fuel supply opening.

 - Fig. 6 is an elevational view of a particular and preferred embodiment of the ash scraper member.

 - Fig. 7 is a top view of the member shown in FIG. 6.

 - Fig. 8 is a sectional view of a particular embodiment of the fireplace door.

 - Fig. 9 is a view of a particular embodiment of the bottom of the hearth.

 - Fig. 10 is a view of the interior of the foyer.

 - Fig. 11 is a sectional view of the hearth area according to a particular embodiment, in particular for round straw bales.

 - Fig. 12 is a simplified horizontal sectional view of the area of the hearth and the supply tunnel for round bales of straw.

 - Fig. 13 is a sectional view of the downstream heat exchanger.

 - Fig. 14 is a sectional view of the heat exchanger according to FIG. 15.

 - Fig. 15 is an elevational view of part of the cleaning members of the downstream heat exchanger.

 The army of the combvstible, the ccnoustio.n, 1 evacuation of the ashes, the supply of combustion air, the removal of heat and the evacuation of the flue gases are ensured in a clearly visible manner on the drawings. The bales of straw are introduced continuously into the combustion chamber 4 by a fuel supply tunnel 14, the combustion taking place only in the zone 8 near the rear wall of the combustion chamber, in which moves also, by rotation, the ash scraper member 9. This member 9 is provided with scraper elements 10 directed forwards towards the combustion zone. According to FIG. 3, the scraper elements 10 are shorter when going towards the periphery of the scraper member 9.

 From the combustion zone, the hot gases rise in the upper part of the combustion chamber 4 having, overall, the shape of a well. From there, the hot gases arrive on the downstream heating surface 16 which will be described more precisely in the following. After providing their heat, they are then evacuated by the connection 17 for evacuating the flue gases.

 The bottom 3 of the combustion chamber 4 is closed, except as regards a more or less wide slot 7 extending along the rear wall 5 of the combustion chamber. As a result, the primary air rising from the ash collecting chamber 6 does not sweep from the bottom the entire bale arriving in the combustion chamber, but in practice that the front surface of this bale or the area combustion.

 The rear wall 5 of the combustion chamber 4 or of the combustion shaft has at least one secondary air opening 2, in accordance with FIG. 3; the rear wall 5 is produced in the form of a combustion chamber door 5 ′ with water circulation having substantially the dimensions of the fuel supply opening 1. This door 5 ′ appropriately carries the shaft, produced under shape of a hollow shaft 11, for rotating the ash scraper member 9 which is seen in front elevation in FIG. 2. The shape and arrangement shown for the member 9 are given only by way of example and will be described more precisely below. The only essential point is that the scraper elements 10 exert, so to speak, a gentle scraping action on the front surface of the combustion zone. Due to the use of a hollow shaft 11, it is not necessary to provide additional openings of secondary air in front of the combustion zone. It suffices only to provide them, if necessary, in the side walls 4 "of the combustion chamber 4, as seen in FIG. 4.

The particular mounting of the hollow shaft 11 will also be described more precisely in the following in connection with the particular arrangement of the door 5 ′ of the combustion chamber.

 The arrangement and arrangement of the ash scraper member 9 are shown very schematically in FIG. 3, in particular with regard to the rotary drive control 18 and the elastic support 12. As mentioned previously, values can be taken from this elastic support, if necessary, for adjusting the speed of supply of the fuel. These values can be appropriately transmitted to the transport device (not shown) arranged in the fuel supply tunnel. If the feed speed is too high, the fuel slightly displaces the hollow shaft to the right in the axial direction. This displacement can be appropriately converted, without difficulty, to control a modification of the feeding speed.

 The rotational movement transmitted by means of the drive control 18 is slow and preferably takes place in alternately opposite directions.

 The compression elements 15 mentioned above and arranged in the corners of the combustion chamber 4 are presented in accordance with FIG. 5 (or in Fig. 14) when looking into this chamber, through the inlet opening 1. In other words, the whole of the combustion chamber forms a sort of funnel part.

 As regards the ash scraper member, reference is made to FIG. 6 and in FIG. 7. On the shaft 11, produced in the form of a hollow shaft, are arranged using triangular support plates 25, the arms 19 ′ forming the frame 19. On the front edges 26 are mounted the ash scraper elements proper in the form of triangular sheets 27.

 The two arms 19 'define at their ends 22 an opening 23 through which a scraper element 21 "is mounted in the shaft 11, so that the end 24 of this element advances a little beyond the arms 19'.

 Side scraper elements 21 are mounted for rotation, as shown, so that during the rotation of the whole scraper member, they can come alternately against stops 20 by moving along the arms 19 'and avoiding thus the formation of sintered deposits. On the same axis as that of the central scraper element 21 ", which also rocks in reciprocating motion during rotation, are mounted in the shaft 11 two scraper elements 21" 'lengthened accordingly, these elements sweeping the area middle of arms 19 '. In addition, one can also provide, on the outside, two other scraper elements 21 'moving between stops 20' in the form of stirrups.

 During the rotation of the entire device, all the scraper elements tilt in an alternating movement between their stops, the ends 22 of the arms 19 'and the wall of the hollow shaft also serving as stops.

 The arms 19 ′ can also be produced in the form of flat tubes with four sides and be placed, if necessary, in direct connection with the internal volume of the tube in order to obtain a certain cooling action.

 Moreover, as mentioned above, air is sent into the hollow shaft, so that the entire ash scraper member thus also experiences a certain cooling. With an appropriate dimensioning and arrangement, it may moreover be quite sufficient to provide only four lateral scraper elements 21.

 The entire device also serves, at the same time, as a device for adjusting the speed of supply of fuel because its shaft is also mounted to move in axial direction in a -ertR rle limit. A corresponding preferred embodiment is shown in FIG. 8.

 A console 29 being judiciously in the form of two arms and extending upwards is judiciously disposed on the door 5 ′ of the hearth. The bearing support 30 is hinged freely hanging from the upper end 29 ′ of the console 29. In the area of the door 5 ′ of the hearth, the bearing support 30 intended for the shaft 11 is made in the form of box. In the box 33 are the bearings of the shaft. A gear 34 surrounding the shaft is also mounted in the box, this gear meshing with a small drive pinion 35 whose rotation is controlled by a drive motor 36 disposed outside the box 33.

 At the other end of the shaft 11 is mounted the ash scraper member 9 which has been described previously. In Fig.

8, this organ is simply indicated.

 At the lower end 31 of the box 33 is provided a projection 39 traversed with sufficient clearance by a rod 37 of the hearth door and maintained in the middle position between two springs 38. As can be seen in the figure, the springs 38 are adjustable by means of adjustment nuts 40.

 A control projection 32 is further mounted at the lower end 31 of the box 33, this projection being appropriately held, opposite a pulse generator 41. This pulse generator is connected to the transport device ( not shown) solid fuel.

 Due to the large length of the bearing support 30 and therefore the large distance from the upper end 29 'of the console 29 to the axis of the hollow shaft 11, it is clear that the curvature of the operating path shaft 11, which can effectively swing, is extremely small. As a result, the passage opening 42 provided in the hearth door can be narrow as a result.

 Since the weight of all the pendulum suspensions 9, 11, 30, 33, 36 is entirely supported by the console 29, an extremely sensitive pendulum behavior is obtained which can be adapted to the extent desired by the conditions encountered by adjusting the nuts 40.

 As can be seen in Figs. 9 to 12, the slot 7 for falling ash and the primary air inlet is widened in its middle part by a slot 7 'directed opposite the direction of supply (from right to left in the 'example considered). There is thus obtained on the whole a slot having in plan a shape of T.

 The lateral parts 47 of the bottom 3 of the hearth located next to the slot 7 'are, as can be seen in FIG. 10, bent with a downward concave curvature.

 Above the assembly, is arranged the ash scraper member 9 rotatably mounted. This organ has been described previously and is indicated in broken lines. The incandescent bed 43 which forms and which burns on the front surface has a section having substantially the shape of a right triangle placed on its short side in accordance with FIG. 11 (as far as this can be represented in a simplified manner). Due to the concave curvature, the ball and the incandescent bed are free above the slot 7 ', so that the primary air can arrive in good conditions on the lower part of the incandescent bed which is not directly reached by the ash scraper member 9 and therefore cannot be destroyed, which is very important for continuous combustion. On the other hand, the same is true for the more or less light scraping of the ashes in the field on the long side, that is to say known on the front surface, by the ash scraper member 9. These ashes can pass through the slot 7 and arrive in the ash collecting chamber e.

 Large round bales of straw (dimensions approximately 1.5 to 0.8 m thick / 300,000 kcal / h) can thus be burned. It has been found advantageous to bring these round bales into the supine position as this can provide optimal combustion conditions in continuous service.

 For this reason, the supply tunnel 14 has a flattened rectangular shape adapted to the section of lying round bales 44, in accordance with FIG. 12.

 The supply takes place from the side at the unrepresented end of the feed tunnel 14 Under the effect of the transport pressure in the tunnel, the round bales are deformed and take a rectangular shape (only the principle of this deformation is indicated). The entire fuel cap is, before reaching the actual combustion zone, brought by a shaping and mouthpiece 45 in one or more elements, to a section corresponding at least ap approximately to that which can be reached by the ash scraper member 9. A guide plate 46 connecting without step to the shaping and mouthpiece 45 can extend into the tunnel from the upper part of this part 45.

 Since the walls 4 "of the hearth (Fig. 10) must in any case be coated with a refractory material to obtain good combustion, the elements for shaping the fuel cap are directly provided with such a material.

 It is not absolutely necessary that the regulation of the speed of supply of the bales, to a large extent in accordance with the combustion speed, take place by means of the ash scraper member 9 movable in the axial direction.

Equivalently, it would be entirely possible to provide on the transport members of the supply tunnel 14 elements with similar action cutting the drive control when the transport resistance becomes too large, that is to say when the bullet cap comes through its front surface against the ash scraper member. In such a case, the rotational movement of the latter is obviously stopped. The ash scraper member must therefore not, in this embodiment, be displaceable in the axial direction, nor be equipped with detectors, limit switch switching elements, pulse generators or the like. Of course, this is valid not only for round bales 44, but also for bales compressed in the shape of a box.

 The type and arrangement of the downstream heating surface 16 is also not unimportant for optimal use of the heat obtained by the combustion of straw. For this, this surface must have a very particular construction, as this is shown in Figs. 13 to 15. In this case, the box 48 is arranged with water circulation, except with regard to the front side, the connection side to the boiler and a separate chamber 62. The entire interior volume comprising the duct passage 51 which extends by forming meanders from the inlet opening 63 to the outlet opening 56 is accessible by means of a closing cover 61 covering all the passage elements 49.

 The inlet opening 63 of the heat exchanger 16 is connected to a corresponding opening of the well of the combustion chamber of the heating boiler (see Fig. 1).

 By the meandering arrangement of the passage duct 51 as well as by the appropriate arrangement, one after the other, of passage elements 49, the flow of flue gases, which constantly tends to rise, is deflected twice in the embodiment shown. There is obviously a separation of the ashes in each deflection zone.

The illustrated flue gas evacuation pipe 52 is advantageous because it descends into the area of the outlet opening, so that there is still a deviation and separation of ash in the separate chamber 62.

 Ash depositing chambers 53, 53 'provided with ash collecting boxes 57, 57' are arranged below the flow opening 55 and the separate chamber 62. The ash collecting box 57 'can be removed laterally of the box 48.

 The passage elements 49 are separated from each other by water circulation partitions 50 each provided with longitudinal ribs 54 directed downwards. The same applies to the cover of the upper passage element 49.

 By means of cleaning members 58 movable along the longitudinal ribs 54, actuated by hand or automatically and constituted by rod screens 19 and movable plates 60, the passage elements 49 can be cleaned without having to open the closing cover 61 in which the rods 59 are mounted. The side of the movable plates 60 directed towards the longitudinal ribs 54 is, in accordance with FIG. 15, arranged in the form of a comb. This comb-shaped side is dimensioned or cut so as to reach, during its displacement, not only the long longitudinal grooves; 4, but also the bottoms of the passage elements 49.

 It has been found that the separation of the ashes was so intense that a heating boiler provided with such a heat exchanger 16 could be directly connected to a normal chimney without interposing a particular ash separator which would increase the resistance to draft.

 The two partitions 50 with water circulation are, in accordance with FIG. 14, arranged with a slight inclination from one side wall to the other of the box with which they are in connection with the circulation of water. This can guarantee good water circulation.

 Refractory masonry is indicated by coarse hatching and exterior insulation is indicated by fine cross hatching.

Claims (9)

CLAIMS 1 - Heating boiler for the combustion of straw bales, in particular of compressed bales, comprising a combustion chamber (4), the vertical wall of which has a fuel supply opening (1) disposed above it '' an ash collecting chamber (6), the fuel supply opening (1) being supplied by means of a closed fuel supply duct (14) and provided with transporting members, at least one air opening secondary (2) being provided in the rear wall (5) of the combustion chamber opposite the fuel supply opening, a flue gas heat exchanger (16) being arranged above the chamber boiler combustion characterized in that a horizontal bottom (3) is provided between the combustion chamber (4) and the ash collecting chamber (6), this bottom having along the rear wall (5) of the combustion chamber combustion a slit (7) for the evacuation of the ashes and the supply of primary air, and in c e that an ash scraper member (9) movable in a vertical plane in front of the combustion zone is provided above the slot (7).  20) - Heating boiler according to claim 1, characterized in that the ash scraper member (9) is provided like a rake of scraper elements (10) directed towards the combustion plane, this member being arranged at the end of a hollow shaft (11) passing through the rear wall (5) of the combustion chamber, capable of being driven in at least one direction of rotation and forming the opening of secondary air.  30) - Heating boiler according to claim 2, characterized in that the ash scraper member (9) is arranged with the hollow shaft (11) in order to be able to move in the axial direction in opposition to the thrust of a support elastic (12> disposed outside the combustion chamber (4).  40) - Heating boiler according to either of claims 2 and 3, characterized in that the scraper elements (10) are shorter and shorter from the center towards the periphery of the scraper member.  5) - Heating boiler according to claim 1, characterized in that compression elements (15) are arranged in the corners of the combustion chamber (4) and reduce the section of this chamber.  6) - Heating boiler according to claim 1, characterized in that the slot (7) for ash fall and primary air supply is widened in its middle part by a slot (7 ') directed at the opposite of the fuel supply direction and extending in the bottom of the hearth, under the ash scraper member (9), the lateral parts (47) of the bottom of the hearth located next to the slot (7 ') being curved downwardly, if one refers to the flat bottom (3) of the hearth in front of the slot.  70) - Heating boiler according to claim 1, characterized in that the section of the tunnel supply duct (14) is rectangular and flattened, this section being adapted to the section of round bales (44) introduced flat.  8) - Heating boiler according to claim 1, characterized in that the ash scraper member (9) is arranged in the form of a bar (19) slightly bent like a snowplow, at least one side scraper element (21) , mounted to turn bremert o live between knolls Ct limitation (20), being arranged on either side of each arm (19 ') of the bar - (19).  90) - Heating boiler according to claim 8, characterized in that scraper elements (21 ') mounted to rotate freely and pivot between limiting stops (20) are arranged at the end of the shaft (11) to outside the area of action of the bar (19).  100) - Heating boiler according to any one of claims 1 to 5, characterized in that the ash scraper elements are arranged in the form of sheet triangles (27) or projections in the form of strips mounted on the arms (19 ').  11 ") - Heating boiler according to claim 8, characterized in that an adjustment member (37) is disposed at the end on the drive side (11 ') of the shaft (11) of the ash scraper member (9), a pulse generator (41) in connection with the drive control of the ash scraper member (9) being arranged in the adjustment path of the adjustment member.  120) - Heating boiler according to claim 1, characterized in that a console (29) projecting upward is disposed on a door (5 ') constituting the rear wall (5) of the combustion chamber, a bearing support-of the shaft of the ash scraper member, suspended in front of the door, being pivotally mounted at the upper end (29 ') of the console (29j, the lower end (31) of this support being held resiliently relative to the door (5 ') and being provided with a control projection (32).  13b) - Heating boiler according to claim 1, characterized in that the flue gas heat exchanger is arranged in the form of a box (48) whose internal volume is divided into several horizontal passage elements (49) constituting a passage duct (51) which forms meanders, these elements being separated from each other by water circulation partitions (50), at least one ash collecting chamber (53) with removable ash box ( 57) being arranged in the path of the passage duct (51), the water circulation cover walls of the passage elements (49) being provided with longitudinal ribs (54) extending in the direction of flow.  140) - Heating boiler according to claim 13, characterized in that cleaning members (58) are arranged to move in the box (48) in the direction of the longitudinal ribs (54), these members being constituted by rods (59) at the ends of which are mounted mobile plates (60) in the form of a comb corresponding to the profile of the longitudinal ribs.  150) - Heating boiler according to claim 14, characterized in that the cleaning members (58) are mounted towards the outside in a closure cover (61) extending over all of the passage elements (49) and closing them.  16) - Heating boiler according to claim 13, characterized in that the ash collecting chamber (53) of the flue gas discharge pipe (52) and the mouth of the outlet opening (56) are arranged in a chamber (62) separate from the passage duct (51).