EP2198931B1 - Method and apparatus for extinguishing sparks transported by a stream of gas - Google Patents

Abstract

The method involves channelizing the gas flow to allow passages of the gas flow through an outlet flow disturbance unit that disturbs the outlet flow to inflame the sparks, where the disturbance unit is infusible and non-combustible and is in contact with the sparks. A displacement of the disturbance unit is achieved in a continuous or discontinuous manner. The disturbance unit is deformed so as to release particles stuck in the disturbance unit. An independent claim is also included for an installation including a spark extinguishing device and filtering device.

Description

The invention relates to a device and a method for extinguishing sparks. This device and method are intended to prevent fires in installations or gases and / or fumes are transported. They are in particular intended to prevent fires in dust and / or soot filtration devices transported with gases, in particular flue gases. The invention also relates to an installation comprising a previously mentioned device mounted upstream of a filtration device or integrated with a filtration device.

The device and method may in particular be used, upstream of filtering devices, in the flue gas discharge ducts of boiler rooms, in particular boilers using wood combustion or in gas evacuation ducts and / or dust produced at any level of an industrial process, in particular at a grinding dust suction station on a metal part deburring station or at a gas suction station released during of the melting of metals in the field of iron and steel industry.

In the installations mentioned, fires or malfunctions are caused by sparks. For the purposes of this description, the term "spark" is understood to mean any incandescent particle and the notion of an electric spark which is formed by an electric arc made possible by the ionization of a non-conductive medium is excluded. The sparks are transported by the gases circulating in the installations. When this installation comprises a filtration device, the spark is transported to this device. In the case where the filter comprises fusible and / or combustible filter elements, problems are pose. In fact, sparks arriving on fusible filter elements melt and locally pierce these elements. As a result, the filtration device is damaged and can no longer provide the performance for which it was designed. In addition, sparks on combustible filter elements can ignite these elements. Therefore, a fire can occur in the filter device that can be completely destroyed. Such a fire also involves a significant risk to the safety of property and people in the vicinity.

For reasons other than a risk of fire or deterioration of a filtration device, it may also be useful to extinguish sparks carried by gases.

Different solutions have been developed to overcome these disadvantages.

A first solution consists in detecting the presence of sparks at the level of a duct carrying gases by means of a detector using for example a technology based on infrared radiation and injecting, in the duct, downstream from the location of the detection, a product to extinguish sparks. The product can be a liquid, such as water, injected for example in the form of fog. The product can also be a non-oxidizing powder or gas. Examples of implementation of this first solution are for example known documents EP1422675 , DE20004490 , US4194570 and US3885631 .

A second solution is also to detect the presence of sparks in a gas-carrying pipe by means of a detector using, for example, a technology based on infrared radiation and to stop the gases or deflect them out of the atmosphere. driving downstream of the place of detection. Examples of implementation of this first solution are for example known documents DE20004490 , IT1223223 and EP0885633 .

These two solutions can still be combined.

These solutions have significant disadvantages. On the one hand, they require numerous and constraining means: it is necessary to provide an opening in the pipe for detecting sparks, to install the detection means, to install injection or deflection means in the pipe, to supply the means of injection into extinction product, connected the different means to each other and to a power supply. All of this translates accordingly into significant costs in hardware, installation and maintenance.

On the other hand, they are intrusive. Indeed, the injection of extinguishing products can have important consequences, especially on gas treatment processes downstream of the injection point. Similarly, stopping or deflecting gases can have significant consequences, especially on gas treatment processes downstream of the stopping point or deviation.

Document is also known GB 2 183 020 a device for stopping a flame propagating in a pipe. The structure of such a device comprises a set of annular plates arranged at a distance from each other. Such a device does not make it possible to extinguish sparks transported in a flow of gas.

We still know the document US 4,307,673 a spark extinguishing device. Such a device comprises a relatively complex structure and expensive to implement. Indeed, it includes a frame rigid defining rectangular openings in which fitted blades move.

Also, the object of the invention is to provide a device and a spark quenching method that overcomes the disadvantages mentioned and improves the spark quenching devices and methods known from the prior art. In particular, the invention provides a device and a method implementing simple means, inexpensive and easy to implement, easy installation and maintenance operations are reduced. The invention also provides a device and a method without consequences on possible downstream gas treatment processes.

The process according to the invention is defined by claim 1.

Different embodiments of the process are defined by claims 2 to 4.

The device according to the invention is defined by claim 5.

Different embodiments of the device are defined by claims 6 and 7.

An installation according to the invention is defined by claim 8.

• La figure 1 est un schéma d'une installation comprenant un dispositif d'extinction d'étincelles selon l'invention.
• La figure 2 est un schéma d'un premier mode de réalisation d'un dispositif d'extinction d'étincelles selon l'invention représenté en coupe selon le plan II-II de la figure 3.
• La figure 3 est un schéma du premier mode de réalisation représenté en coupe selon le plan I-I de la figure 2.

The appended drawing represents, by way of example, an embodiment of a spark extinguishing device according to the invention.

• The figure 1 is a diagram of an installation comprising a spark extinguishing device according to the invention.
• The figure 2 is a diagram of a first embodiment of a spark extinguishing device according to the invention shown in section along the plane II-II of the figure 3 .
• The figure 3 is a diagram of the first embodiment shown in section according to plane II of the figure 2 .

The installation represented at figure 1 comprises a system at which sparks 12 are produced, such as in particular a grinding station, a welding station, a steel furnace, a boiler. The sparks produced are transported by gases in a first pipe 3 to a spark extinguishing device 4. After passing through this device, gas and particles 13 (sparks extinguished) pass through a second pipe 5 allowing them to 6. The gases making it possible to set the sparks and the particles in motion are themselves set in motion by means of a fan, in particular a fan arranged in the filtering device, upstream or downstream of the means for filtering. filtration of the filtration device. The extinguishing device can be integrated into the filtration device.

The filtration device is preferably of the type with fusible and / or combustible filtering means. The filtration means are for example sleeves having a closed end and an open end and mounted on supports, for example metal called mannequins. The filter elements are arranged so that the gases must pass through the material, for example felt, forming the sleeves of the outside of the sleeves towards the inside of the sleeves. Crossing these sleeves, the particles are separated from the gases. Indeed, all particles larger than a critical size determined by the structure of the material constituting the sleeves are stopped at level of the outer surface of the sleeves. The gases emitted at the outlet of the filtration device are therefore devoid of particles larger than this critical size.

An embodiment of an extinguishing device 4 is described below with reference to FIG. figure 2 . It mainly comprises a housing 7, for example made of metal sheets and means 9a and 9b disturbance of the gas flow. In this embodiment, the housing comprises two communicating chambers 14 and 15 delimited by a partition 16. The first chamber is connected to the pipe 3 from which gas and sparks 12 and possibly other extinguished particles arrive. second chamber 15 is connected to the pipe 5 where the gases and the extinguished particles 13 leave in the direction of the filtration device 6.

The gases, the sparks and the particles thus enter and pass through the first chamber 14 before entering and passing through the second chamber 15. The aeraulic sections of the chambers can be dimensioned so that the velocity of the gases is lower in the rooms to what it is in the pipes.

In the first chamber 14 is a first means 9a for disturbing the flow of gas.

In the second chamber 15 is a second means 9b disturbance of the gas flow.

By means of disturbance means any means for modifying the characteristics of the gas velocity vector, that is to say its direction and / or its norm. Indeed, these disturbances have a very important effect on the sparks. Sparks have a high density compared to gases so a significant inertia compared to that of the gases. carrying. Thus, a sudden disruption in gas velocity creates significant relative velocities between gases and sparks. These relative speeds make it possible, when the gases containing oxygen, to stoke and consume the sparks. In the case of sparks formed by metal particles, the relative speeds can cool them. Thus, after the first disruption means 9a a portion of the sparks has been extinguished. Paradoxically, we get the extinction of the sparks by stoking them until they are completely consumed.

The disturbance means makes it possible to increase the distance traveled by the sparks in the extinguishing device.

The term "disturbance means" excludes any means of connection between two pipes having different airspace section areas and / or any means of connection between two pipes having different directions or directions. The term "disturbance means" also excludes any network of tubes or fins of an exchanger that would be placed in the gas flow.

The gases, the particles and the sparks then pass into a second disturbance means 9b in the second chamber. The same effect is obtained so that after the second means of disturbance all the sparks are extinguished and there is no longer a risk of fire at the filtration device 6 downstream.

The plates defining the chambers 14 and 15 here constitute guide means for channeling the flow of gases through the first and second perturbation means.

Preferably, in the first chamber, the gas velocity is at least substantially parallel and in the same direction as the gravitational acceleration and, preferably, in the second chamber, the gas velocity is at least substantially parallel and of sense opposite to gravity acceleration. Thus, there is obtained between the two chambers a separation of particles and sparks, on the one hand, and gas on the other hand, by centrifugation and action of the gravitational acceleration, the flow of gas effecting a rotational movement between both rooms. It is advantageous to have a particle recovery means such as a tank at this level. Only the largest particles will be recovered at this level.

The flow disruption means comprises a network of wires in the spark-laden gas stream. These wires are non-combustible and non-fusible in contact with sparks. For example, the wires are metal wires. Preferably, they are juxtaposed. They can also be woven. Advantageously, they constitute a mat. The gases must pass between these wires to join the pipe 5. The density of the son, their diameter, their spacing are determined according to the perturbation characteristics that one wishes to obtain. Obviously, the more spaces between the wires will be limited in size and number, the more we will disrupt the flows. In addition, the size of the spaces between the wires determines the size of the particles that can pass through the disturbance means and the size of those that will be blocked by the disturbance means. Preferably, the limit size of the particles that can pass through the first perturbation means will be greater than that of the particles that can pass through the second perturbation means.

The diameter of the wires may be between 0.01 mm and 3.5 mm. For example, it may be 0.2 mm. The maximum distance between centers two wires disposed in a plane at least substantially perpendicular to the overall direction of the gas flow may be between 0.01 mm and 1 mm. For example, it may be 0.02 mm.

These parameters must be set precisely. Indeed, the abovementioned distance distances determine the critical size of the sparks that will be retained by the son and will remain fanned for a long time in the gas flow. It is important that sparks with a size greater than this critical size be retained because if they were not they could still be fanned through the disturbance means and reach the incandescent filtration device. Particles smaller than this critical size are considered unable to reach the filter device in an incandescent state. Indeed, the phases in which they are stoked enough to consume them completely. In particular, the parameters will be set according to the nature of the sparks (in particular their material wood, metal ...), the number of passage in disturbance means and the distance between the extinguishing device of the filtration device.

Thus, the son can be arranged in a row in a plane substantially perpendicular to the overall direction of the gas flow. Preferably, the disturbance means comprises several rows of wires at least substantially parallel and offset with respect to each other, so that if a particle of gas passes through the first row of wires without being deflected, it is necessarily deflected by the action son of one of the successive rows or it has, at least, strong chances of being deflected by the action of son of one of successive rows.

Means for setting the disturbance means in motion make it possible to move the means in a continuous or discontinuous manner disturbance so that any particles blocked between the wires can be evacuated.

Any sparks that would be trapped between the wires are also subject to significant relative velocities of the gases that bypass them. Thus, these sparks can also be fanned and consumed quickly. Blocked particles between the wires help to disrupt the flow or flow of gases and particles.

In the preferred embodiment, the first perturbation means comprises a shaft 17 on which are fixed wires 10a extending at least substantially radially, the wires extending towards the laminations of the housing 7 coming into contact with those this. Thus, the disturbance means substantially has a radial wire brush structure. Preferably, the second perturbation means has the same structure. Advantageously, it integrates the same tree, in particular, its part passing through the second chamber. In these cases, the moving means advantageously comprise a geared motor 11 in connection with the shaft 17. This shaft is guided by bearings and can be rotated.

Since the wires come into contact with the laminations of the housing, they bend under the effect of the contact forces during their rotation. This allows effective release of particles that were jammed and that contributed to disrupting the flow or flow of gases and particles.

If this effect is not sufficient, it can have stops 23 on the plates. These stops having the function of bending even more strongly son and facilitate the release of particles stuck between the son.

Nevertheless, the yarns can also bend under their own weight and / or under the effect of the gas flow and / or under the effect of variations in speed (in particular of rotation) of the disturbance means, without the need for contacts on the means of disturbance, in particular on the son. In this case, the means of deformation of the disturbance means may be constituted by the structure of the perturbation means itself (in particular the diameters and lengths of the wires) and / or by a means for driving or setting in motion the means of disturbance.

In addition, to further facilitate the release of particles trapped between the son, it is possible to provide means 21, 22 for injecting gas under pressure to cause violent gas jets at the son to cause the evacuation of particles stuck and that contribute to disrupt the flow or flow of gas and particles.

Preferably, the setting in movement or the displacement of the means of perturbation causes the deformation of the means of perturbation.

Preferably, the whole of the disturbance means is set in motion or displaced.

In another embodiment not shown, the spark extinguishing device comprises only one means of disturbing the flow of gases. This means is placed in a single chamber and means are provided for moving the disturbance means.

The setting in motion can be ensured by any means which makes it possible to pass blocked particles downstream of the means of disturbance. In particular, it can be provided by periodic manual action on a lever, a crank.

Blocked particles at the level of the disturbance means also contribute to disrupting the flow or flow of gases and particles.

The invention also relates to a method for extinguishing sparks carried by a gas flow. It is for example implemented by one of the devices described above. It comprises a step of channeling the gas flow to pass through a means of disturbing the flow so as to fan the sparks, the disruption means being non-fuse and non-combustible in contact with the sparks. It also comprises a step of deformation of the disturbance means so as to release particles stuck therein and / or a step of projecting gas under pressure towards the disturbance means so as to release particles stuck in it .

Preferably, it also comprises a step of continuous or discontinuous displacement of the disturbance means, for example in rotation by action of a geared motor.

Advantageously, the process comprises several passages of the gas flow through distinct perturbation means.

Claims (8)

1. Method for extinguishing sparks (12) carried by a gas flow, comprising a step of channelling the gas flow in order to make it pass through a means (9a) for perturbing the flow so as to make the sparks burn up, the perturbation means being non-meltable and non-combustible in contact with the sparks, the method being characterized in that it comprises a step of deforming the perturbation means so as to release the particles trapped in it.
2. Extinguishing method according to Claim 1, characterized in that it comprises a step of continuously or discontinuously displacing the perturbation means.
3. Extinguishing method according to one of the preceding claims, characterized in that it comprises a step of spraying gas under pressure in the direction of the perturbation means so as to release the particles trapped in it.
4. Extinguishing method according to one of the preceding claims, characterized in that it comprises a plurality of passes of the gas flow through separate perturbation means (9a, 9b).
5. Device (4) for extinguishing sparks (12) carried by a gas flow, comprising a means (9a) for perturbing the flow, which makes the sparks burn up, and a means (7, 16) for channelling the gas flow through the perturbation means, the perturbation means being non-meltable and non-combustible in contact with the sparks, the device being characterized in that the perturbation means comprises a network of filaments (10a, 10b) which are non-meltable and non-combustible in contact with the sparks, and in that the device comprises a means (23) for deforming the perturbation means.
6. Extinguishing device according to Claim 5, characterized in that it comprises a means (11) for continuously or discontinuously displacing the perturbation means, such as in particular a means for setting the perturbation means in rotation.
7. Extinguishing device according to either of Claims 5 and 6, characterized in that it comprises a means (21, 22) for spraying gas under pressure in the direction of the perturbation means so as to release the particles trapped in it.
8. Installation (1) comprising an extinguishing device (4) according to one of Claims 5 to 7 and a filtration device (6).

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