EP0215830B1 - Plant for cooling by spraying means - Google Patents

Abstract

Apparatus comprising one suction chamber opposite the upper surface of the sheet material and at least at the entry point and at the exit point. The spray bars (7 to 9) are arranged between two adjacent suction chambers (3, 4; 4, 5; 5, 6). The chambers are arranged above the droplet deflection zone which is limited by the flaps mounted on the edges of the chamber opening. Spray bars are also provided opposite the lower surface of the material.

Description

The invention relates to a spray treatment installation more particularly intended for cooling metallurgical products successively comprising spraying means and a suction box disposed in front of a material such as plate, sheet metal, etc. continuously scrolling.

Attempts have been made, in installations intended for coating a surface with a powdery product or material, to avoid the dispersion of said product or material in the atmosphere for ecological and / or economic reasons.

Thus, manual or automatic painting installations always include suction means in which the paint mist and the solvents are separated from the spraying air before being discharged into the atmosphere.

Installations having the same aims have been adapted to operations comprising the projection of powdered products onto surfaces already coated with a base coating before proceeding to fix the coating by heat or chemical treatment.

European patent application No. 0 117 958 describes a device intended to collect a gas charged with metallic powder after this has been used for coating a strip provided with a base coating. The device comprises a box formed by two symmetrical casings between which the strip to be covered circulates. The box is divided lengthwise into three compartments, the first and last compartments comprising means for blowing the gas loaded with powder and the central compartment having return slots for collecting the gas loaded with residual metal powder. The central compartment is connected to the suction of a fan and the charged gas is sent to a metering device which restores the powder content before it returns to the gas blowing means. Aerodynamic seals are provided at the ends of the box to prevent the blown gas loaded with metal powder from escaping outside the device.

We know, for example, from patent JP-A-5 681 633, a thermal treatment installation comprising ramps of sprayed water jets intended to cool a material at high temperature passing in front of them. The steel sheet runs vertically, in a closed enclosure, in front of a series of spray bars between which suction pipes are arranged. These conduits carry on their lower edge collecting plates which have the function of collecting the drops of water which fall from an upper ramp and which would risk disturbing the functioning of the ramp. The drops thus collected by the plates are sucked out of the installation. The enclosure is connected to extraction means in order to prevent fog exits through the sheet metal inlet and outlet passages.

This device is suitable for thin sheets capable of running vertically but cannot be suitable for the treatment of thick sheets which must necessarily run horizontally. In this case in film boiling regime (non-wetting regime) intervening for example for steel sheets for wall temperatures higher than approximately 400 ° C to 500 ° C, the water droplets fractionate in contact with the wall to cool with a very low evaporation and spur out.

If these droplets are not evacuated, they grow and fall on the sheet, producing accumulations of water. This water is then evacuated towards the sides of the sheet which undergo a more intense cooling than the medium.

To avoid this, it is necessary to create a sufficient air flow in order to transport the droplets after their fractionation.

The object of the invention is to provide an installation for treating by spraying a liquid, intended for the cooling of a metallurgical product continuously scrolling and for the evacuation of the sprayed water by the organization of gas flows conveying the droplets so as to avoid asymmetric cooling of the treated surface.

The invention can in particular be used for the formation of a moderate cooling zone as provided for in patent FR-A-2,571,384 in the name of the applicant.

The treatment installation according to the invention is carried out according to the characteristics described in claim 1.

• - Les rampes et les caissons sont séparés par des espaces libres permettant le passage de l'air venant accompagner les jets des pulvérisateurs. Le débit d'air est ainsi supérieur à celui amené par les fentes des pulvérisateurs, ce qui est favorable pour véhiculer les gouttelettes;
• - les distances entre les rampes de pulvérisation et la face à refroidir d'une part et les distances entre deux rampes de pulvérisation consécutives d'autre part sont définies de façon à organiser l'écoulement de l'air provenant du pulvérisateur et de l'air secondaire pénétrant entre caisson et pulvérisateur et accompagnant le jet, cette organisation ayant pour effet de permettre de véhiculer et évacuer les gouttelettes rejaillissant de la surface chaude.

The succession of spraying booms and suction boxes is organized according to the following criteria:

• - The ramps and the boxes are separated by free spaces allowing the passage of the air coming to accompany the jets of the sprayers. The air flow is thus greater than that supplied by the slots of the sprayers, which is favorable for transporting the droplets;
• - the distances between the spray bars and the face to be cooled on the one hand and the distances between two consecutive spray bars on the other hand are defined so as to organize the flow of air from the sprayer and the secondary air penetrating between box and sprayer and accompanying the jet, this organization having the effect of allowing to transport and evacuate the droplets reflecting from the hot surface.

In particular, the distance between consecutive spraying booms will be sufficient so that there is substantially no direct interaction between the jets of successive sprayers and that it is, moreover, possible to form and separate directed flow zones. towards the product to be cooled and flow zones deviating from the product;

- the suction boxes placed between the spray bars and also at the two ends of the machine are located directly above the area where the gas and droplet flows from two successive spray bars meet; they include skirts provided on the edges of the suction opening confining the zone of spouting of flows and droplets.

• - la figure 1 représente schématiquement en perspective et en partie arraché un exemple d'installation de traitement selon l'invention.
• - la figure 2 est une vue en perspective d'un caisson d'aspiration.
• - la figure 3 est une vue en coupe transversale du caisson selon la figure 2.

The explanations and figures given below by way of example will make it possible to understand how the invention can be implemented.

• - Figure 1 shows schematically in perspective and partially broken away an example of a treatment installation according to the invention.
• - Figure 2 is a perspective view of a suction box.
• FIG. 3 is a cross-sectional view of the box according to FIG. 2.

According to the embodiment shown schematically in Figure 1, the installation according to the invention is intended for the cooling of a metallurgical product which passes horizontally after, for example, its exit from a treatment furnace or from a rolling mill.

A roller conveyor 1, horizontal, supports and drives a sheet 2 in a spray treatment installation constituted according to the example shown, of four suction boxes 3, 4, 5, 6 arranged transversely relative to the direction of movement sheet metal and three spray bars 7, 8, 9 arranged between the boxes. According to a preferred embodiment, the booms are made up of two-dimensional ply jet sprayers such as those described, for example, in French Patent No. 2,375,911. The jets of the sprayers reach the sheet, spread out along its surface then rebound during the interaction with the flows coming from the neighboring sprayers. It has been found, and this in a fairly wide range of flow rates, that the droplets, forming the sprayed sheets coming from two neighboring sprayers, after their cooling action on the sheet, reflect with air in a relatively limited area, centered in the space separating the two sprayers. If these reflective droplets are not evacuated they grow and fall on the sheet. The water thus deposited in this zone is evacuated by the edges of the sheet where it produces cooling conditions different from those initially planned with the sprayed water and produced in the central area of the sheet.

In order to avoid the enlargement of the droplets and their fallout, the suction boxes are placed between the sprayers above the area in which the air and droplet flows are reflected, the area being confined by skirts carried by the openings of the boxes, the free edge of which descends near the surface of the sheet. The distance separating the edge of the skirt from the surface of the sheet allows the passage of the air flow conveying the droplets reflecting after impact on the sheet.

The installation, according to the example shown, being intended for homogeneous cooling of the sheets, lower ramps 10 whose jets are directed from bottom to top, are arranged below the sheet, and approximately opposite the upper ramps 7, 8, 9 so that the surface covered by the jets on the lower surface of the sheet corresponds to that covered on the upper surface by the jets of the upper ramps. This avoids the tensions produced by cooling differences on the two faces of the sheet and consequently the deformations.

The problem of evacuating the droplets which have reached the sheet does not arise for the lower ramps 10, the droplets falling by gravity and not risking gathering on the sheet to locally modify the cooling conditions.

An embodiment of the suction boxes is shown in Figure 2. A box is formed of a metal frame, of approximately parallelepiped shape, closed on three of its longitudinal ribs by a formwork ensuring sealing. The ends of the box are closed by plates 11 carrying a central hatch 12 giving access to the drop separator. The profiles constituting the upper part of the chassis extend outside the formwork to secure the box on the main frame of the installation. The upper wall 13 of the formwork carries, according to the embodiment, two circular passages 14, 15 on which are fixed cylindrical housings 16, 17 connected to the suction of fans (not shown).

According to the cross section of Figure 3, the box has at its lower part, approximately in the extension of its side faces 18, 19, mobile skirts 20, 21 which confine and isolate the rebound zone avoid, in case of deformation of the sheet to be treated, the deterioration of the boxes and allowing the passage of the deformed sheet. This arrangement makes it possible to place the upper sprayers at a sufficient distance from the pass line (for example 0.7 m) to allow the passage of deformed sheets without damaging the machine.

The box leaves at its lower part a longitudinal opening 22 of relatively large width, limited on one side by a gutter 23 and on the other by a partition 24 which forms, with an upper wall 25 and one face of a separator of drops 26, a chamber in which is sucked the air-droplet mixture flowing between the skirts 20, 21. A certain part of the droplets settle on the walls and fall back into the gutter 2, 3 while the other part passes through the plates separator 26 where the droplets are retained and flow in the lower part between the partition 24 and the wall 19 forming a gutter 27. Boxes 28, 29 provided at the ends of the box, receive the water recovered by the gutters which is led by pipes (not shown) to an evacuation or to a recycling installation.

The number of elements of the installation (suction boxes and spraying booms) depends on the length of the product to be treated but also on the desired cooling capacity.

Whatever the length of the installation, therefore the number of elements, it will always include an inlet suction box and an outlet box, this in order to avoid as far as possible a dissemination in the atmosphere of the fog produced by the spray bars.

The drop separators 26 can, as a variant, be arranged outside the suction boxes. In this case, several boxes can be connected to a single box carrying the separators 26 and the suction fans.

Claims (8)

1. Cooling apparatus, by water-spraying, of a plate in a high temperature material and in particular of a thick metal sheet (2) of large width, moved through the apparatus, said apparatus comprising spray-bars (7, 8, 9) supplied with water and pressurized air which provides the spraying of water in drop form and their high-speed projection onto the plate (2) to be cooled, alternated with suction chambers (3, 4, 5, 6) characterized in that the plate being horizontally, moved through the apparatus and cooled on both of its faces, only the upper spray-bars (7, 8, 9) are located between the suction chambers so that each bar is located between two chambers and spaced from the latter by a distance providing fresh air inputs for creating symetrical sweeping air flux which selectively drive upwardly for draining off, deflected droplets formed through thermal and mechanical divisions of the drop impacting the upper surface of the plate.

2. Apparatus according to claim 1, characterized in that the suction chambers (3, 4, 5, 6) are designed for draining off the total sweeping air flow, including the spraying air flow injected between the chambers and the bars.

3. Apparatus according to claim 1, characterized in that the upper spray-bars (7, 8, 9) and the fixed lower part of the suction chambers (3, 4, 5, 6) are located at a distance of the plate path large enough to allow deformed metal sheets to pass without damaging the machine.

4. Apparatus according to anyone of claims 1 to 3, characterized in that at least one spray-bar (7; 8, 9) consists of a sheet-jet sprayer.

5. Apparatus according to anyone of claims 1 to 4, characterized in that it has a spray-bars (10) arranged beneath the lower surface of the sheet material (2), approximately opposite the spray-bars (7 to 9) of the upper surface.

6. Apparatus according to anyone of the preceding claims, in which the suction chambers (3, 4, 5, 6) consist of a parallelepipedic casing closed on three of its longitudinal sides, characterized in that said chambers are provided, on the fourth side, with a longitudinal opening (22), delimited, at least on one side, by a gutter (23, 24) receiving the water formed by the droplets which are deposited on the walls (18, 19) of the casing, water chests (28, 29) provided at the ends of the chambers receiving the water recovered by the gutters, and in that flaps (20, 21) are provided in the extension of the opposed side faces (18, 19) along the opening.

7. Apparatus according to claim 6, characterized in that the other longitudinal side of the opening is provided with a separating wall (24) comprising a side of a droplet separator (26) wich forms, with the sides of the casing opposite with regard to the opening, a chamber inside which the air/ droplet mixture is sucked, the droplets retained by the separator (26) flowing away between the separating wall (24) and the side (19) of the casing, into the water chests (28, 29) provided at the ends of the casing receiving the water recovered by the gutters.

8. Apparatus according to claim 1, characterized in that the droplet separators (26) are placed outside the suction chambers (3, 4, 5, 6), several suction chambers being connected to one casing only comprising the separators (26) and suction fans.

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