WO1993011389A1

WO1993011389A1 - Combustion and ash-removal grate having a rotary bar array

Info

Publication number: WO1993011389A1
Application number: PCT/FR1992/001088
Authority: WO
Inventors: André MAGRI
Original assignee: Europeenne De Combustion S.A.
Priority date: 1991-11-25
Filing date: 1992-11-24
Publication date: 1993-06-10
Also published as: CA2124317A1; FR2684170A1; EP0663054A1; FR2684170B1

Abstract

A combustion and ash-removal grate consisting of horizontal parallel bars (1) placed side by side and resting on supporting and rolling rails (2). The bars are interconnected by chain links (3) linked to control bars (4) and actuators (5). The bars may be rotated by imparting a linear reciprocating motion to the resulting bar array relative to the supporting rails. Said grate is used to burn various homogenous or heterogenous solid materials which may contain non-combustible components.

Description

COMBUSTION AND ASH GRID WITH ROTATING BARS TRAIN

A) Basic techniques to which the invention relates: i>

The present invention relates to a grate intended to equip a boiler hearth or an incineration oven making it possible to burn all types of solid combustible or semi-combustible materials, and in particular various waste and mixtures such as: wood, textile, papers, straw, household waste, supermarket waste, agricultural biomass, industrial waste, etc.

These burnt materials generally pose two major difficulties: non-homogeneity of the mixture resulting in a more or less variable calorific value and humidity, but also untimely presence of non-combustible foreign bodies such as metals, glass, etc.

There are traditionally, in particular in the old construction of certain gas generators, combustion grates constituted by rotary bars with integrated air blowing which have the advantage of simultaneously ensuring a double function:

- Supply the fireplace continuously with metering and distribution of primary air.

- Regularly eliminate combustion residues (ash removal).

The grid according to the invention is inspired by this type of grid in its initial design, but while benefiting from the basic advantages, is characterized by aptitudes for new functions, by a certain simplicity of design, and by a reliability and a increased operational safety.

B) Composition of the device according to the invention:

Figure 1 schematically shows a plan view of the grid consisting of a set of identical bars (1), with horizontal axes, juxtaposed parallel, and resting on two running rails (2) located at the ends.

The bars of circular section are joined together at their ends by large chain links (3) to thus form a train of bars.

The pitch of the chain produced according to FIG. 1 corresponds to the distance between the bars. In order to ensure lateral movement in both directions of the bar train, the ends of the two chains are connected to two lifting beams (4) connected to two hydraulic or pneumatic single or double acting cylinders (5) coupled together. This makes it possible to carry out a regular back and forth movement of the train of bars on the two support rails (2).

As an indication, the approximate dimensions of a bar (not definitively fixed) can be of the order of 3 meters in length and 0.3 meters in diameter.

Figure 2 shows in elevation and in section the end of a bar which can be made hollow and in this case the combustion air will be distributed by a collector (6) which can be fixed or mobile, the air being introduced at the end of each bar by means of a double sonic cone (7).

The principle of the sonic cone consists in the manner of a venturi to increase the speed of the air passing through a duct by a progressive reduction of the passage section, in order to create a dynamic pressure effect in the longitudinal direction of the bar thus decreasing static pressure being exerted transversely and consequently the importance of air leaks.

This system thus has a double advantage; on the one hand, to use the dynamic pressure effect to distribute the air more uniformly over the entire length of the bar, particularly in the theoretically disadvantaged central part; and on the other hand to make a non-sealed proximity connection between the movable bar and the fixed collector.

The connection between the bar (l) and the chain links (3) consists of a hub fitted with a wear ring (8) with high temperature friction resistance.

Figure 3 shows in section the current section of a bar whose external profile is similar to that of a ratchet wheel, which has teeth (9) and in the case of a hollow bar of the blowing orifices (lθ ) alternately and uniformly distributed over the entire periphery of the bar.

FIG. 4 represents a longitudinal section of the bar with a regular toothing profile but not rectilinear so as to limit the risks of jamming by possible foreign bodies. C) Different design variants

The present invention based on the principle described above includes all of the following design variants, the adoption of which will depend on the overall size of the equipment, the type of material to be burned, the manufacturing technique, the quality of the materials used. work, and the automation or not of the device:

- The assembly of the bars (l) constituting the bar train can be carried out in any other way instead of the chain link system defined in Figure 1, provided that the bars can always rotate on themselves according to their main axis. Can be used as defined for example in Figure 9 a movable comb system (14) which could be located below the level of the rails (2) or above as specified in the figure. More simply, according to the examples defined in Figure 10 can be used any device (15) playing the role of spacer between the bars with different possibilities using friction pieces or rollers, single or multiple, mounted free assembled together to constitute floating assemblies located outside or possibly inside the ends of bars. Depending on the configuration chosen, the movement of the train of bars must be carried out only by traction or compression of the assembled assembly.

- The bearing support rails (2) can be increased in number, supporting all of the bars or even groups of bars by first defining treads (ll) assigned to each bar or each group of bars according to the example of the sketch defined in figure 6.

- The bearing support rails (2) can be positioned horizontal or in an inclined plane according to the example of the sketch defined in FIG. 7, while maintaining the axes of the horizontal bars, and in this case the movement back and forth from the train of bars may be produced by means of a single assembly composed of a lifting beam (4) and a jack (5), the assembly being situated on the highest side of the train of bars. The return movement of the bar train can be carried out naturally by gravity under the effect of the weight of the bar train. In the event, for example, of insufficient inclination of the support rails (2), the return movement may be accompanied by a system with one or more springs (12) or any other hydraulic or pneumatic mechanical means producing the same effect. - The bearing support rails (2) instead of being fixed may be movable according to the sketch defined in FIG. 8, mounted on sliding pads or rollers (13) mounted idly around their axis, the rails being able to be moved along their longitudinal axis in the same way as the chains (3) using the same devices as those described above. In this case the ends of the two chains making up the train of bars will be connected to a fixed frame and the movement of the rails will make the bars rotate on themselves without moving the train of bars.

- The lifter (s) (4) can be deleted and in this case the jacks (5) will be connected directly to the ends of the two chains (2), the action of the jacks needing to be coupled and coordinated so as to obtain the movement desired from the train of bars.

- The cylinder (s) (5) used may be single or double acting combined or not, provided that one wishes to maintain a tension or a permanent or untimely compression on the two chains (3).

- The jacks may be hydraulic or pneumatic and replaced by any pneumatic or electric mechanical device producing a similar linear linear translational movement of the train of bars.

- The bars can be either full or hollow, depending on whether one wishes to supply combustion air above or below the grate via an independent air distribution network, or through the interior of the bars themselves.

D) Advantages provided by the grid according to the invention

The grid according to the invention, in addition to certain and well-known advantages linked to the technique of rotary bars; such in particular the improvement of the behavior of the materials thanks to the cooling provided by the circulation of air inside the bars, as well as a very uniform distribution of the combustion air; has many unique features.

To satisfy the multiple conditions making it possible to ensure the most complete combustion possible by reducing the rate of unburnt at the level of the ashes, it is desirable to first of all create a circuit for prior drying of the materials to be burned at the level of the oven, and then to regularly and uniformly supply the fireplace with primary combustion air, to ensure a good distribution and permanent mixing of the waste to be burned in a layer not too thick and uniform, and finally to evacuate the residues regularly and if possible automatically combustion. The rotation of the bars by rolling on rails is clearly different from the system which consists in rotating them on support bearings situated at the ends.

This rotation of the bars being accompanied by a displacement relative to a simple rotation about themselves along a fixed longitudinal axis makes it possible to simultaneously meet the best conditions for satisfying the combustion described above. The creation of a dynamic effect allows, at the same time as the evacuation of the ashes, a stirring facilitating the homogenization and the aeration of the layer in combustion, which has the effect of improving the activation of the hearth and increasing thus clearly the thermal capacity of the furnace.

The asymmetrical external profile of the teeth as shown in Figure 3, allows thanks to a jerky back and forth movement of the train of bars, on the one hand by a chopper effect to grind the bottom ash which usually tend to form a hard layer difficult to evacuate at the same time as the ashes through the bars, and on the other hand by a treadmill effect to ensure the progressive displacement at the top of the train of bars of any incombustible foreign bodies, up to their evacuation at the end of the grid.

In the event of any foreign body blocking between two bars, safety is automatically ensured by the sliding of the bars concerned on the rails during the movement of the train of bars, which makes it possible to benefit from a role of torque limiter of the system. Thanks to the asymmetrical profile of the teeth, the movement in the opposite direction of the train of bars will automatically ensure the release.

The rotation of the bars by rolling on two rails also makes it possible to avoid the use of bar support bearings, which usually constitute a difficulty of implementation in a difficult and corrosive atmosphere at high temperature.

The uniform cross-section of the bars makes it possible to avoid any angular positioning with respect to each other, and to allow for safety deviations in rotation in particular by the play of the sliding of the bars on the rails, and thus to avoid to constantly have the same bar surface exposed to fire and abrasion. This will help to significantly increase the longevity and life of the bars.

Another advantage of the train of bars lies in the ease of extracting for repair or maintenance the entire grid by simple rolling on the two support rails without the addition of an additional device. In the case of the use of hollow bars, the introduction of air inside the bars is carried out at high speed thanks to a sonic cone placed at each end of the bar. By dynamic effect, this ensures a uniform distribution of flow rates over the entire length of the bar and a better aeraulic balance.

The use of a sonic cone makes it possible to avoid a direct mechanical connection posing difficulties at high temperature while minimizing air leaks.

The air leaks caused by the system during the movement of the train of bars do not present any difficulties since they have the advantage of allowing the cooling and dusting of the mechanical elements situated at the ends of the bars.

The ash removal is ensured by a movement back and forth quite fast and more or less frequent depending on the evolution of combustion, the nature and characteristics of the waste burned.

The grid surface can be easily modified by adding or removing one or more bars, for example using chain links.

The method which consists in assembling the bars by means of a system composed of chain links is advantageous at the start given the high temperatures encountered or any rigid element of great length is to be avoided because of the risk of deformation.

The operating clearance between two bars, which may possibly be defined and adjusted according to the nature of the fuel burned, can be permanently adjusted by modifying the length of the chain links used.

But if necessary and if the nature and characteristics of the products to be burned justify it, a play between the bars can also be usefully carried out in an untimely manner, so as to ensure a regular release of the train of bars by simple variation of the space available between the bars. In this case, a simple technical modification consists in making chain links with non-circular but oblong holes in the form of horizontal light forming a hub into which the circular axes of the bars are introduced according to the sketch defined in FIG. 5.

This modification makes it possible, thanks to a simultaneous traction / compression action at the ends of the chains of the train of bars, to modulate the space available between the bars, thus facilitating the passage of foreign bodies through the grid. This obviously requires in automatic operation a coordination of the action of the jacks. The movements can be ensured with great reliability by means of jacks connected to the two lifting beams and controlled by a hydraulic or pneumatic group, thus authorizing the installation of a complete automation by means of a servo and / or any programming.

The combustion grate according to the invention has, in addition to a very moderate manufacturing cost, a large number of advantages, while using a mechanical and hydraulic system of great simplicity adapted to the difficult ambient conditions of high temperature and abrasion. imposed by the combustion of various wastes.

Depending on the type of material burned and the size chosen for the bars, the air blowing can be carried out independently under a train of solid bars. Likewise the shape of the toothing, in particular the number of teeth, can be modified.

The present invention is deemed to cover these various variants as stipulated in the claims below.

Claims

1) Combustion and ash removal grid consisting of at least two horizontal bars juxtaposed in parallel, characterized in that the bars (l) free to rotate about their longitudinal axis rest on at least two parallel rails (2) forming a raceway and perpendicular to the axes of the bars, said bars being interconnected in whole or in groups so as to constitute a train of bars whose relative movement between rails and train of bars in a direction parallel to the rails is likely to cause the rotation of the bars.

2) Combustion and ash removal grid according to claim 1 characterized in that the support and rolling rails (2) will be arranged in an inclined plane thus allowing to benefit from the exercise of a relative movement between rails and train bars in one direction and by gravity effect in a direction parallel to the rails.

3) Combustion and ash removal grid according to claim 1 and claim 2 characterized by the use of multiple and parallel support and running rails (2) making it possible to define different treads (ll) according to the bars and d '' assign a bar or a group of bars to one or more specific rails.

4) Combustion and ash removal grate according to claim 2 or 3 above, characterized by the use of a system composed of a return system produced by one or more springs (12) or any other means producing the same effects, allowing to ensure an automatic return movement of the bar train.

5) Combustion and ash removal grid according to any one of the preceding claims, characterized in that the support and rolling rails (2) will be movable and the train of bars fixed, the bars being rotated by a traction or compression of the support rails (2) along their longitudinal axis resting on several sliding shoes or rollers (13).

6) Combustion and ash removal grid according to any one of the preceding claims, characterized by bars (l) connected to each other at the various ends by means of two chains made up of links (3), the pitch of these chains being equal to the distance between the axes of two adjacent bars or equal to an integer fraction of this distance. 7) Combustion and ash removal grate according to claim 6, the axis holes of the links (3) will be made oblong in the form of horizontal light and constituting a hub for the circular axes of the bars, this arrangement making it possible to modulate the spacing of the bars (l) during a relative movement back and forth between rails and train of bars in a direction parallel to the rails.

8) Combustion and ash removal grid according to Claims 1 to 5, characterized by bars connected to one another by means of various devices (15) constituted by the assembly of one or more friction pads or free rollers, which devices can be inserted at the ends of the bars outside or inside thereof.

9) Combustion and ash removal grid according to any one of the preceding claims, characterized in that the chain links (3) or any other elements connecting the bars together are joined at one or the other or at both ends of the train of bars by means of a lifting beam (4).

10) Combustion and ash removal grid according to any one of the preceding claims, characterized by the use of one or more cylinders (5) with single or double effect and with control coupled or not depending on the configuration chosen, said cylinders being actuated by a hydraulic or pneumatic unit ensuring the relative movement of the bar train relative to the rails in a direction parallel to the rails in an alternating movement back and forth.

11) Combustion and ash removal grate according to any one of the preceding claims, characterized by bars (l), the cross section of which has a regular succession of asymmetrical teeth (9) at the periphery, making it possible to obtain an external profile of bar similar to a ratchet wheel (Figures 3 and 4).

12) Combustion and ash removal grid according to any one of the preceding claims, characterized by hollow bars (l) whose air supply inside the bars is effected by means of a double sonic cone ( 7) placed at one or both ends of each bar and at each outlet of an air distributor manifold (6). 13) Combustion and ash removal grid according to any one of the preceding claims, characterized by hollow bars (l) and comprising over their entire periphery and in a uniform manner an alternating succession of blowing holes (10) and teeth (9) with a longitudinal profile that is not straight but regular in shape, over the entire length of the bar (Figure 4).

14) Combustion and ash removal grid according to any one of the preceding claims 1 to 6, characterized by solid bars and an independent fixed air distribution network ensuring uniform distribution of combustion air below or above the train. of bars