EP0290317B1 - Increased-control flexibility boiler furnace, particularly for urban refuse, with a grate composed of fire bars which are alternately secured and movable to and fro - Google Patents

Abstract

PCT No. PCT/FR88/00203 Sec. 371 Date Dec. 20, 1988 Sec. 102(e) Date Dec. 20, 1988 PCT Filed Apr. 26, 1988 PCT Pub. No. WO88/08502 PCT Pub. Date Nov. 3, 1988.The grate comprises, within its length, two consecutive beds (41, 42) with substantially the same general slope joined together at a point in substantial vertical alignment with the altar wall (7), each bed having its own mobile frame (45d, 46d) with its own control means (45, 46) and its own draft chamber (43, 44) with its own ventilation means. It is therefore possible to adjust the combustion conditions so as to optimize the carbonization mode combustion on the upstream bed (41) and the brasier mode combustion on the downstream bed (42).

Description

The invention relates to a boiler hearth according to the preamble of claim 1.

The type of grate which equips such fireplaces, where the faces of the elements devoted to the thrust of the fragments of mass in combustion are turned upstream to oppose the rapid descent of combustible solids and cause stirring or stirring of the mass, has been abundantly described in the state of the art since patent US-A-2250067 filed in 1938. Since improvements have been made, aiming in particular the provision of blowing orifices which pass through the elements of bars to bring combustion air to the mass in combustion, from blowing boxes located below the grate.

Provisions have been recommended to improve the poking by lining at least certain elements of bars with projections at the connection of the dorsal and front faces, and to improve the cooling of the bars by the blowing combustion air.

Patent document FR-A-2574160 describes a hearth grate which comprises elements of bars provided at the connection of the front face and the dorsal face, and on the latter, of faceted transverse projections, with blowing orifices of air formed in a rear facet of the projections so as to look downstream and conduct air jets from below the grid into the mass of combustible solids, in a direction which goes up by about 15 ° on the horizontal.

This patent document further describes means for keeping the elements of adjoining bars in alignment.

The use of solid fragment fuels of uneven quality, such as urban waste, with sometimes relatively large contents of non-combustible components which will constitute clinkers and ashes, poses problems of adjusting the combustion rates.

In order to modulate the adjustment of the combustion stages along the grate, the document FR-A-1466632 proposes an urban waste incinerator with a grate in several successive layers whose back and forth movements are individually adjustable. However, this arrangement applies to a grid whose successive tiers of bars, alternately fixed and movable, are arranged with a front face facing downstream, the lower edge of which then rests on the dorsal face of the bar immediately downstream. This arrangement causes a thrust of the fuel downstream cooperating with gravity to advance the fuel towards the ashtray. This mode of action of the bars induces combustion conditions different from those which prevail on grates of the kind described in FR-A-2576160 where the thrust of the front faces of the bars acts against the progression of the combustible. In addition, the incinerator described by FR-A-1466632 is not associated with a boiler, and the grid is disposed entirely under a radiation vault, the fumes of which escape mainly downstream, a minor part being diverted to an entry dryer.

Furthermore, most solid fuels successively have two modes of combustion, a first mode of carbonization, where the volatile components are released, which burn giving long flames, and a brazier mode, almost without flames, where combustion continues. on solid fuel components, or embers.

The optimal combustion conditions are different depending on the combustion modes. During carbonization, the fuel layers can be relatively thick, and the pressure drop of the combustion air through the layer remains moderate, the channels between combustible fragments being of relatively large sections, and the formation of the flames giving an impulse to combustion air. On the other hand, in the brazier mode, the ashes and bottom ash cause significant pressure losses for the combustion air and the layers are advantageously thinner. In addition, the heat transmission from the ignition points to the remaining combustible parts takes place mainly by radiation and partly by convection of the fumes, and is hampered by the presence of ash and bottom ash.

When, in a current way, the combustion conditions are regulated for a compromise between the optimization of the carbonization mode and that of the brazier mode, approaching the optimization of the carbonization mode which implements a major part of the latent energy of combustion, the proportion of unburnt in bottom ash is significant.

The subject of the invention is a hearth of the kind defined above, in which the combustion efficiency is increased by particular settings of the combustion conditions in the carbonization and brazier modes.

To this end, the invention provides a boiler hearth, with a grid intended to support a mass of solid fragments in combustion, in particular urban waste, made up of two parts, namely a boiler chamber connected to a flue gas flue. and extending longitudinally from a loading area upstream of the grate to a generally vertical wall called an altar wall, and a lowered vault connecting to the boiler chamber in the altar wall and extending the hearth up to an ashtray downstream of the grid, the latter comprising, in a downward slope between the upstream loading area and the downstream ashtray at least one ply consisting of a succession of transverse bars with a dorsal face for the support of the mass, and a front face in sliding support by a lower edge on the dorsal face of the bar immediately upstream, the bars being hooked by a downstream end alternately to a fixed frame d e hearth and a movable frame back and forth longitudinally under the impulse of a control means, the hearth further comprising, under the grid, at least one blowing box equipped with ventilation means for supplying air oxidizing the mass through blowing orifices provided in the bars, characterized in that the grid comprises, in its length, two successive layers with substantially the same general slope, one of the layers being disposed in the boiler chamber and the in the lowered vault, each tablecloth having its own movable frame with its own independently adjustable control means, and its own blowing box with its own independently adjustable ventilation means.

As each of the two grid layers has its own means of adjustment, both of the blowing and of the conditions of progression of the fragments of combustible mass, the upstream layer can be adjusted to optimize the carbonization mode and the downstream layer to optimize the brazier mode.

On the other hand, the division of the hearth into two parts, boiler chamber and lowered vault, connected by the altar wall, has the effect of determining different combustion regimes, the boiler chamber lending itself to the development of long flames, while the lowered vault downstream forms a reverberation and lends itself to the burning of embers. Thus the separation of the grate into two layers, and that of the hearth into two parts with corresponding connections, do they cooperate in the separate optimizations of the two combustion modes.

Preferably, the grid layers will be equipped with rod elements according to FR-A-2574160.

Advantageously, the grate is extended by an awning apron above the ashtray, adjustable in orientation around a horizontal axis adjacent to the grate end. The orientation of this apron makes it possible to adjust the rate of dumping of ash and clinker into the ashtray, and therefore to act on the thickness of the layer of embers on the downstream layer.

• la figure 1 est une coupe d'ensemble d'un foyer selon l'invention;
• la figure 2 est une vue latérale de la grille qui équipe le foyer de la figure 1;
• la figure 3 est une coupe suivant le plan III-III de la figure 2;
• la figure 4 est un détail IV de la figure 2, montrant le raccordement des deux nappes de grilles;
• la figure 5 est une vue montrant la solidarisation latérale des éléments de barreaux de grille.

Secondary characteristics and advantages of the invention will emerge from the description which follows, by way of example, with reference to the appended drawings in which:

• Figure 1 is an overall section of a fireplace according to the invention;
• Figure 2 is a side view of the grid which equips the hearth of Figure 1;
• Figure 3 is a section along the plane III-III of Figure 2;
• Figure 4 is a detail IV of Figure 2 showing the connection of the two grid layers;
• Figure 5 is a view showing the lateral connection of the grid bars elements.

According to the embodiment of the invention chosen and shown in Figure 1, the hearth 1 as a whole comprises, between an upstream loading hopper 2 and a downstream ashtray 3, a grid 4 composed of an upstream ply 41 and a downstream ply 42, the grid plies being made up of bars which are alternately fixed and movable back and forth longitudinally under the impulse of control means 45 and 46. Under the plies 41 and 42, respectively, are blown boxes 43 and 44. All of this will be explained in detail with reference to FIGS. 2 to 4.

Above the ply 41 develops a boiler chamber 5, which will be traversed by the fumes, guided by baffled partitions, up to an evacuation flue 8.

Above the grid 4, the boiler chamber 5 is closed, downstream, by a brick wall 7 commonly called an altar wall. Beyond this altar wall 7, the hearth extends longitudinally downstream by a lowered vault 6 which terminates in the ashtray 3, the connection of the grate layers 41 and 42 being located substantially at the entrance to the vault 6 in the altar wall 7.

As best seen in Figures 2 to 4, the grid 4 consists of two plies 41 and 42, formed of adjoining elements of bars alternately fixed, 55 and 56 respectively, and movable back and forth respectively 55 ′ And 56 ′. The bars include (see FIG. 4) dorsal faces 55 a , 55 ′ a , 56 a , 56 ′ a , front faces facing upstream 55 b , 55 ′ b , 56 b , 56 ′ b , and projections 55 c , 55 ′ c , 56 c , 56 ′ c , on the dorsal side 55 a , 55 ′ a , 56 a , 56 ′ a at the connection thereof ci with the front face 55 b , 55 ′ b , 56 b , 56 ′ b corresponding.

Each bar 55, 55 ′, 56, 56 ′ rests, by a lower edge of its front face 55 b , 55 ′ b , 56 b , 56 ′ b in sliding support, on the dorsal face of the bar immediately upstream. Furthermore, the fixed bars 55, 56 are hooked by their rear end on a cross member secured to a hearth frame 50, while the mobile bars 55 ′ and 56 ′ are hooked by their rear end to frames respectively 45 d and 46 d , movable longitudinally. To this end, the frames 45 d and 46 d are provided with rollers 53, 54 which are capable of rolling on rails 51, 52 fixed to the hearth frame 50, and arranged parallel to the bars.

In addition, the frame 45 d is coupled to its upstream end, by means of a connecting rod 45 b to a return lever 45 a in turn coupled to a double-acting hydraulic cylinder 45. Similarly, the frame 46 d has a drawbar 46 c fixed at its front end, which passes under the ply 41 to couple, by means of a connecting rod 46 b , to a return lever 46 a , in turn coupled to a hydraulic cylinder 46 double acting.

It will be noted that, at the connection of the plies 41 and 42, is disposed a bar 58, the lower edge of the front face 58 b of which rests on the dorsal face of the movable bar 55 ′ extreme downstream of the upstream ply 41, while the face dorsal 58 a of this bar 58 receives the support of the front face 56 ′ b of the movable bar 56 ′ extreme upstream of the downstream ply 42. The bar 58 is attached by its rear end to a cross member secured to the fixed frame 50.

As best seen in Figure 4, the projections 55 c , 55 ′ c , 56 c , 56 ′ c and 58 c of the bars have, in a facet facing rearward, blowing holes 55 d , 55 ′ d , 56 d , 56 ′ d and 58 d whose axis, directed downstream, rises in this direction with a slope closer to the horizontal than to the vertical, here around 15 °. This arrangement reduces the amount of fly ash entrained with the fumes.

Under the plies 41 and 42 are arranged blowing boxes 43 and 44, respectively, in the form of a hopper, and connected to a general blowing pipe 48 through adjustment valves 43 a and 44 a . Note that in Figure 1, the supply air blowing into the boxes is shown very schematically. The outlet of the valves 43 a and 44 a in the boxes 43 and 44 is located halfway up these boxes, so that the collection of fine ashes which pass through the sheets 41 and 42 does not interfere with the blowing.

At the downstream end of the grid 4 is disposed an apron 47, orientable around a horizontal axis 47 a adjacent to the grid end, and forming a canopy above the ashtray 3. A panel 47 b is arranged in bridge between the extreme downstream (mobile) bar of the ply 42 and the deck 47.

In operation (Figures 1 to 4), urban waste is pushed out of the hopper 2 on the upstream end of the grid 4. The jack 45 is driven back and forth with a rate and a controlled amplitude, driving by the play of the lever 45 a and of the connecting rod 45 b the frame 45 d , so that the bars 55 ′ move back and forth, at the rate of the jack 45 and with a corresponding amplitude, relative to the bars 55 which frame them. The mass discharged from the hopper 2 is kept fragmented and descends the slope along which the grid extends, with a speed determined by the operation of the jack 45, and a thickness depending on this speed and the flow rate of waste discharged from the hopper 2. The supply air flow rate is adjusted by the valve 43 a , so as to obtain adequate large flame combustion (combustion of the distilled products and carbonization of the fixed parts).

On arriving at the bar 58, the waste, reduced for the most part to its solid parts, essentially heavy tars and carbon, and more or less vitrified ash, pass over the sheet 42, whose movable bars 56 ′ are moved back and forth by the jack 46, by a mechanism corresponding to that of the sheet 41, but with a cadence and an amplitude independently adjusted by means of control. It is understood that thus the thickness of the combustible layer can be adjusted to the conditions of burning in the brazier; blown combustion air flow is adjusted by the valve 44 has adequately, given the composition of the fuel layer, the layer thickness correlation with the rate of descent. It will be noted that the adjustment of the inclination of the apron 47 acts in cooperation with the reciprocating adjustment of the movable bars 56 ′ of the sheet 42 to control the thickness of the combustible layer.

It will be noted that the passage over the tablecloth 42 for the establishment of combustion in brazier mode coincides with the engagement of the combustible layer in the lowered vault 6, beyond the altar wall 7. This lowered vault reverberates , and facilitates the maintenance of the burning of embers.

All these provisions contribute to a better use of the calorific power of combustion of urban waste, by reducing the rate of unburnt in ash and bottom ash.

The grid bars are obviously not one piece across the width of the hearth, for easily understandable reasons of weight, deformation, and installation and replacement. They consist of substantially rectangular elements, joined sideways. However, the reduction in weight of the unit pieces resulting from the division of the bar into elements, if it facilitates handling, has the disadvantage that the elements are more easily lifted from their support on the upstream bar when a foreign body tends to s between the bars.

Also, as seen in Figure 5, the elements 101, 102 are they joined by their end faces 101, 102 under the projections 103, 104 which are formed of blowing openings such as 104.

The connection is obtained by a C-shaped bridge 105 with two branches joined by a cross, the two branches penetrating into complementary cavities formed in the front faces 101 a , 102 a . The trigger guard 105 is fully engaged in these end faces, and is held in place by plates 107, 108, welded to the end faces 101 a , 102 a , by arc pointing.

Of course, the invention is not limited to the example described, but embraces all the variant embodiments thereof, within the scope of the claims. Thus, for example, the guide as described by rollers 53, 54 and rails 51, 52 can, in certain applications, advantageously be replaced by a guide of the movable frames by means of rollers on inclined planes.

Claims (10)

1. A furnace hearth with a grate designed to support a mass of burning solid fragments, in particular urban refuse, formed in two parts, viz. a furnace chamber (5) joined to a flue for drawing off fumes and extending longitudinally from a loading area (2) upstream of the grate to a generally vertical wall (7) known as an altar wall, and a surbased vault (6) joined to the furnace chamber (5) in the altar wall and extending the hearth as far as an ash box (3) downstream of the grate, the latter comprising, in a descending slope between the loading area (2) upstream and the ash box (3) downstream, at least one bank consisting of a succession of transverse bars (55, 55′) with a dorsal face (55a,...) for supporting the mass, and a frontal face (55b,...) with its lower edge slidingly resting on the dorsal face of the immediately upstream bar, the bars being attached by a downstream end alternately to a fixed structure of the hearth and to a movable frame which is in longitudinal to-and-fro movement under the impulse of a control means, the hearth further having, under the grate, at least one draught chamber (43, 44) equipped with ventilation means for feeding combustive air to the mass through draught openings made in the bars, characterised in that the grate comprises, within its length, two consecutive banks (41, 42) with substantially the same general slope, one of the banks (41) being arranged in the furnace chamber (5) and the other in the surbased vault (6), each bank having its own movable frame (45d, 46d) with its own independently adjustable control means (45, 46), and its own draught chamber (43, 44) with its own independently adjustable ventilation means.

2. A hearth according to Claim 1, characterised in that the grate bars (55, 56) consist of a row of elements (101, 102) substantially rectangular in plan view, adjoining at substantially vertical side faces.

3. A hearth according to Claim 2, characterised in that the bar elements (101, 102) have, at the junction between the frontal face and the dorsal face and above the latter, at least one projection (103, 104) having trapeze-shaped longitudinal section, with a front facet starting from the frontal face and a rear facet ending on the dorsal face and an upper facet between the front and rear facets.

4. A hearth according to Claim 3, characterised in that the draught openings (104a) are made in the rear facet, substantially perpendicular to the latter.

5. A hearth according to Claim 4, characterised in that the draught openings have axes upwardly inclined towards the downstream, nearer to the horizontal than to the vertical.

6. A hearth according to Claim 5, characterised in that the upward slope of the axes of the openings is at an angle of approximately 15° with the horizontal.

7. A hearth according to Claim 2, characterised in that the said bar elements are fastened together along the row by their frontal faces.

8. A hearth according to Claim 1, characterised in that the two banks (41, 42) are joined on a bar (58) attached to the fixed structure of the hearth, resting with the lower edge of its frontal face on the dorsal face of the extreme downstream bar of the upstream bank, and supporting with its dorsal face the lower edge of the frontal face of the extreme upstream bar of the downstream bank.

9. A hearth according to Claim 1, characterised in that the control means (45, 46) belonging respectively to each of the two banks (41, 42) are suited to impart a to-and-fro movement to the corresponding frame, with an amplitude and rhythm which can be adjusted independently of one another, and in that the ventilation means equipping the respective draught chambers of the two banks are independently adjustable in their flow rate.

10. A hearth according to Claim 1, characterised in that the grate is extended by a panel (47) forming a hood above the ash box (3), this panel being adjustable in a direction about a horizontal axis next to the downstream end of the grate.

Images