WO1995014886A1

WO1995014886A1 - Combustion chamber continuously fed by a hopper with movable walls

Info

Publication number: WO1995014886A1
Application number: PCT/FR1993/001163
Authority: WO
Inventors: André MAGRI
Original assignee: Europeenne De Combustion S.A.
Priority date: 1992-05-22
Filing date: 1993-11-25
Publication date: 1995-06-01

Abstract

A combustion chamber for combusting solids in a continuous solid fuel feed boiler furnace or incinerator. The chamber consists of an insulating housing made up of a number of walls (1-6), a combustion grate (7) and at least one side hopper with two movable slanting walls (8 and 9) consisting of various elements. The alternating and co-ordinated movements of the two movable walls (8 and 9) having a rack-shaped cross-section enable the fuel mass to be moved such that it is dried before being fed into the combustion chamber.

Description

CONTINUOUS HOPPER FIREPLACE WITH MOBILE WALLS

DESCRIPTION

A) BASIC TECHNIQUES TO WHICH THE INVENTION RELATES:

The present invention relates to a hearth for the combustion of solid combustible materials, the feeding of which is carried out continuously, by carrying out the preliminary drying of the materials to be burned.

The hearth defined below can be integrated into a boiler, or equip an incineration oven with combustible materials and various wastes. The materials to be burned may possibly consist of a mixture of combustible or semi-combustible elements which are difficult to burn, knowing that these elements could simultaneously have a low calorific value and a high humidity. The following materials are included in this category: wood, textiles, paper, straw, household waste, supermarket waste, agricultural biomass, miscellaneous waste, etc.

Feeding a fireplace continuously requires generally the reduction and grinding of the fuel elements, in order to allow the use of conventional techniques for transporting pulverulent products. In particular, Archimedes' screw systems, or pneumatic transport systems, are widely used.

In the event of non-prior reduction by grinding or crushing the elements to be burned, the systems commonly used are "feeders" constituted by a movable belt composed of chain elements and tiles in the manner of a tank track, or more conventional belt conveyors. These traditionally used devices do not allow easy separation between the external and internal ambience of the hearth, so that they must be necessarily coupled with devices effecting the intermittent introduction of materials into the hearth, of the type multicell airlock (for example: rotating barrel distributor). Another important difficulty arises when it comes to intermittently filling a fireplace in operation. The sudden introduction of the materials to be burned into the combustion mass causes a cooling of the hearth, sparks and ash flights difficult to control.

Furthermore, in the case of feeding a mixture of non-homogeneous ground materials such as household waste for example, the mechanical transport systems used must be extremely robust, taking into account the abrasion of certain materials, and the presence of significant heat related to the proximity of the fireplace.

Can also be cited fireplaces of the "volcano" type, used in the supply of certain wood waste boilers. In this case, the waste is crushed beforehand and transported to the heart of the hearth, under the burning mass, generally using an Archimedes screw. Only this type of fireplace ensures the drying of materials before burning. However, this type of hearth can only be applied to materials of relatively homogeneous composition and particle size. It does not benefit from a gravitational effect for the introduction of materials, which generally generates numerous blockages of operation. Furthermore, it does not make the best use of the heat source of the hearth which is located above rather than below the mass in combustion.

The device according to the invention consists of a hearth with continuous lateral feed by hopper with movable walls. The purpose of this device is to combine the advantages of the "volcano" type fireplace, while avoiding certain disadvantages. The device thus ensures the following multiple functions:

- supply the fireplace permanently without requiring prior grinding of combustible materials.

- ensure the isolation of the interior atmosphere of the hearth in the form of a buffer plug made up of the materials to be burned, without the addition of another device.

- ensure the gradual drying of the materials to be burned before introduction, making the best use of the heat source created by the hearth itself.

- avoid the drawbacks associated with a sudden introduction of the materials to be burned, which could cause the fireplace to cool during operation. B) COMPOSITION OF THE DEVICE ACCORDING TO THE INVENTION:

Figure 1 schematically shows an elevational view of the hearth consisting of a volume materialized by an envelope of heat insulating and refractory material composed of several walls (1) (2) (3) (4) (5) (6). This envelope is open on the side loading hopper, as well as on the flue gas discharge duct in the upper part.

The fireplace thus defined comprises a combustion grate (7) located in the lower part, fixed or movable with manual or automatic ash removal, as well as a system for introducing primary air at the level of the combustion grate, and possibly secondary air in the hearth itself.

All the elements making up the device are located between two vertical and parallel flat walls (5) (6), which can make up both the enclosure walls of the hearth, and the fixed side walls of the hopper.

The shape of the enclosure making up the hearth is not fixed, except that it must adapt to the loading mode constituted by a lateral hopper, i.e. located on one side of the oven , or alternatively, by several hoppers located around the envelope constituting the hearth.

If it is desired to recover the heat from the hearth, the wall (l) can be executed as a double wall and consist of an internal heat conducting wall made of metallic material or silicon carbide with high thermal conductivity, and a external wall made of fibrous insulating materials for example.

Between these two walls, heat recovery can be carried out either by simple circulation of air, or by a network of tubes making up a primary circuit, with circulation of a heat-transfer fluid which will preferably be thermal oil taking into account the temperature level of the fireplace.

The vertical side walls (5) and (6) will preferably be made of refractory materials, so as to maintain a minimum thermal inertia for the entire hearth.

The hopper for the introduction of combustible materials is constituted (FIG. 1), by two fixed walls constituted in this case by the lateral vertical walls (5) and (6) and by two movable walls (8) and (9), located in two inclined planes constituting a V-shaped or Y-shaped profile, which can be materialized in different ways described below. C) CHARACTERISTIC FUNCTIONS OF THE DEVICE:

The inclined movable walls (8) and (9) of the hopper can be made by a simple rigid preformed sheet, reinforced or not, or by several sheets assembled and fixed on the same chassis.

These walls can be supported by two inclined slides fixed on the fixed vertical walls (5) and 6). These slides can be smooth with a U-shaped profile or have rollers to facilitate the movement of the movable walls.

Alternatively, and depending on the configuration chosen, the axes of the rollers can be fixed either directly on the fixed vertical walls (5) and (6) of the hopper, or at the two ends of the movable walls (8) and (9) .

As shown in Figure 1 the profile of the movable walls (8) and (9) is made in the form of a rack.

The profile thus defined, thanks to its orientation will allow for each of the movable walls during their movement, in one direction to advance the combustible materials supported by the wall, and in the other direction to escape this function.

Figure 2 defines the relative movements of the various elements making up the device.

The simultaneous movement of the movable walls (8) and (9) in the X and Y directions will allow the introduction of waste inside the hearth, knowing that inside the hopper the materials to be burned will follow a particular movement defined by direction Z. The advantage of such a movement is to introduce in priority into the hearth the materials in contact with the inclined wall (9), which is itself in direct contact with heat fireplace.

The angle A of the wall (8) relative to the horizontal will be a so-called closed angle and may vary from zero to forty five degrees maximum, while the angle B between the walls (8) and (9) must be an angle said to be open, that is to say greater than ninety degrees. These two conditions are necessary to maintain the essential functions of the device, which consist on the one hand of benefiting from a certain gravity effect for the introduction of the materials, and on the other hand of creating a specific movement of the materials in the direction Z , to ensure drying before introduction. In the case where the angle B is closed, it would not be possible on the one hand to introduce into the hearth only previously dried materials, and on the other hand the risks of blockage of the device would be considerably increased, in particular in the event of presence of foreign bodies.

According to Figures 3 and 4, the movable walls (8) and (9) may be formed as an alternative, and according to the defined profile, by independent elements in the form of carriages (lθ) equipped with rollers (ll).

The trolleys thus formed will be assembled together on each side at the level of the rollers, so as to produce a movable belt formed by the assembled trolleys which can move by rolling on two support rails (12). The moving belt can be driven in an alternating movement back and forth, by one or more jacks (13), double or single acting, with return by spring or counterweight.

The carriages (lθ) can be made with sheets forming an inclined plane, so that the assembly of several carriages makes it possible to obtain a movable belt with a longitudinal profile similar to that of a rack.

Various arrangements can be made with regard to the design of the carriages (lθ), so as to facilitate a certain diffusion of hot air through the layer of material in contact with the wall (9) in order to ensure its drying. Different grids, perforated sheets or expanded metal plates can be used for their manufacture.

The movement of the movable walls of the hopper can be controlled manually with, for example, a counterweight return device, or automatically by actuation of the jacks (13) which can be hydraulically, electrically, or pneumatically controlled, knowing that this command can be automated, either in the form of programmed sequences, or controlled by the value of certain operating parameters of the fireplace (example: temperature). When using a mobile combustion and ash removal grid, the movements of the hopper walls can be coupled with the movements of the ash removal grid.

As a variant, depending on the nature, the mass and the particle size of the materials to be burned; and depending on the value of the angle of inclination A the inclined walls (8) and (9) may be produced in planar elements in the form of tiles (14) with flat or inclined face (FIG. 5) connected together and driven by chains at the ends.

Alternatively also, the tiles thus defined, may be replaced in part or in whole, by rotary bars (15) having a profile in the form of a ratchet wheel, said bars being connected together by chain links and driven by rolling. on rails (12) so as to constitute a movable belt (Figure 6).

The complete device thus produced makes it possible, with a relatively simple manufacture, to carry out a continuous or sequential introduction of the materials to be burned into the hearth, while ensuring their prior drying in order to facilitate their combustion.

The device according to the invention makes it possible to solve the problem commonly encountered concerning the difficulties of introducing materials to be burned into a fireplace in operation.

Claims

1) Hearth constituting a combustion chamber, characterized in that the supply of combustible materials takes place laterally by means of one or more hoppers each comprising at least two walls (8) and (9) forming two inclined planes constituting a V-shaped or Y-shaped profile, each wall being entirely mobile and driven by an alternating movement of linear translation in the plane defined by the wall itself, the relative displacements of the two walls being coordinated so that when 'one wall moves away from the intersection of the two planes considered, the other approaches it and vice versa.

2) A fireplace according to claim 1, characterized in that it comprises at least one hopper for supplying the materials to be burned, the two movable walls (8) and (9) of which are produced with a profile in the form of a rack, which profile is oriented in such a way that the materials to be burned introduced into the hopper are drawn towards the intersection of the two planes relating to the two movable walls when the said walls are driven by an alternating movement of linear translation in the two planes considered (FIG. 1 ).

3) Fireplace according to claims 1 and 2, characterized in that it comprises at least one hopper for feeding the materials to be burned, itself composed of two movable walls (8) and (9) rigid made in one piece , or by assembling several elements, these walls being supported and guided in their movement by U-shaped slides fixed to the vertical walls (5) and (6) of the hopper.

4) Fireplace according to claims 1 and 2, characterized in that it comprises at least one hopper for supplying the materials to be burned, the movable walls (8) and (9) of which are made rigid, are supported and guided in their movement by rollers whose axes are fixed on the fixed vertical walls (5) and (6) of the hopper. 5) A fireplace according to claims 1 to 3 characterized in that it comprises at least one hopper for supplying the materials to be burned, the movable walls (8) and (9) of which are supported and guided in their movement by means of slides in U or rails fixed on the fixed vertical walls (5) and (6) of the hopper, said rails or slides being intended to receive rollers whose axes are fixed at the two ends of the movable walls.

6) A fireplace according to claims 1 to 3 characterized in that it comprises at least one hopper for supplying the material to be burned, the movable walls (δ) and (9) of which are made rigid are supported and guided by resting at the ends on several rollers whose axes are fixed directly on the vertical walls (5) and (6).

7) A fireplace according to any one of the preceding claims, characterized in that it comprises at least one hopper for supplying the materials to be burned, the movable walls (8) and (9) of which are formed by multiple elements in the form of carriages (lθ) connected to each other at both ends, supported by rollers (ll) resting on two rails (12) so as to constitute a movable belt (Figure 3 and 4).

8) A hearth according to any one of claims 1 to 6 characterized in that it comprises at least one hopper for supplying the materials to be burned, the movable walls (8) and (9) of which consist of multiple elements in the form tiles (13) with a flat or inclined profile connected to each other at the two ends by chain links so as to constitute a movable belt (FIG. 5).

9) A fireplace according to any one of claims 1 to 6 characterized in that it comprises at least one hopper for supplying the materials to be burned, the movable walls (8) and (9) of which are formed by multiple elements in the form of rotary bars (15), the section of which is produced with a ratchet wheel-shaped profile, the bars being connected together by chain links and driven by rolling on rails (12) so as to constitute a movable belt ( figure 6). 10) Hearth according to any one of the preceding claims, characterized in that it comprises at least one hopper for the supply of material to be burned, the inclined movable walls (8) and (9) of which consist of grid elements , perforated sheets or expanded metal plates ensuring the transfer of part of the heat from the hearth and allowing the drying of the materials to be burned.

11) Hearth according to any one of the preceding claims, characterized in that it comprises at least one hopper for the supply of material to be burnt, comprising two inclined movable walls (8) and (9) knowing that the wall (8) will have an angle of inclination A with respect to the closed horizontal between zero and forty five degrees, and that the angle B between the ρarois (8) and (9) will constitute an open angle greater than forty five degrees (figure 2) .

12) Hearth according to any one of the preceding claims, characterized in that it comprises at least one hopper for the supply of material to be burnt, comprising two inclined movable walls (8) and (9) whose linear translational movements will be provided by cylinders (13) with electric or pneumatic hydraulic control, these movements making it possible to obtain a continuous or intermittent back and forth cycle by means of any automatic mechanism, said movements being coupled and slaved to any movement d '' a combustion grate (7) made mobile.