Method of drying and/or curing an organic coating on a continuously running metal strip, and device for implementing this method

Abstract

A method of drying and/or curing an organic coating on a continuously running metal strip, includes heating the strip by electromagnetic induction in a tunnel furnace having an enclosure with hot internal walls and heating the enclosure. The heating of the strip by electromagnetic induction is coupled with heating by infrared radiation and heating by convection with a combustion gas. The heating of the enclosure of the furnace is performed by convection using the same combustion gas used for heating the strip by convection. A device for implementing the method is also provided.

Claims

1. A device for curing, drying, or curing and drying an organic protective, decorative, or organic protective and decorative coating previously deposited on a metal strip, the device comprising: a tunnel furnace having an enclosure with hot internal walls, a first end with an inlet and a second end with an outlet; said enclosure having a moving device for moving the strip with the organic coating from said inlet to said outlet; said enclosure having each of: an electromagnetic induction strip heating device for heating the strip passing through the furnace by electromagnetic induction; a wall heating device for heating the walls of the enclosure and the strip with the coating by convection with a combustion gas; and an infrared radiation device for heating the strip with the coating by infrared radiation.

2. The device according to claim 1, wherein said infrared radiation device for heating by infrared radiation and said device for heating by convection are formed of at least one infrared radiation emitter with a catalytic burner including a catalytic structure formed of a catalytic element impregnated with a catalytic combustion material and having a surface onto which a combustion gas or mixture of air and combustion gas is injected.

3. The device according to claim 1, wherein said electromagnetic induction strip heating device for heating by induction includes a plurality of inductors distributed along said enclosure between said inlet and said outlet in a direction of travel of the strip.

4. The device according to claim 1, wherein said infrared radiation device for heating by infrared radiation includes a plurality of infrared radiation emitters with catalytic burners distributed along said enclosure in a direction of travel of the strip and disposed on both sides of the strip.

5. The device according to claim 1, wherein: said electromagnetic induction strip heating device for heating by induction includes a plurality of inductors distributed along said enclosure between said inlet and said outlet in a direction of travel of the strip; said infrared radiation device for heating by infrared radiation includes a plurality of infrared radiation emitters with catalytic burners distributed along said enclosure in said direction of travel of the strip and disposed on both sides of the strip; and said inductors and said infrared emitters are distributed alternately along said enclosure.

6. The device according to claim 5, which further comprises a control system for adjusting a number and positioning of said inductors during operation and their electrical power supply as well as a number and positioning of said infrared emitters during operation and their supply of combustible gas or air/combustible gas mixture.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 is a flow diagram in section of a first example of the curing and/or drying device according to the invention,

(2) FIG. 2 is a flow diagram in section of a second example of the curing and/or drying device according to the invention.

DESCRIPTION OF THE INVENTION

(3) The curing and/or drying device represented in FIG. 1 comprises a curing and/or drying device 1, commonly also referred to as a furnace, preferably vertical and forming a tunnel, through which a strip of steel 2 passes, on which an organic coating of the varnish or paint type has first been deposited and means 3 (for example deflecting rollers) of moving the strip 2 from an inlet E located at a first end of the enclosure 11 of the furnace 1 to an outlet S located at the other end of said enclosure 11.

(4) The furnace 1 comprises an enclosure 11 with hot internal walls (not represented in FIGS. 1 and 2), which is fitted with: a plurality of inductors 4 distributed along the enclosure 11, and a plurality of infrared emitters with catalytic burners 5 (or catalytic radiants) arranged on both sides of the strip 2 alternating with the inductors 4.

(5) The curing and/or drying device 1 also comprises a recovery chamber 6 for the oxidized gases and residual solvents, which are directed towards an incineration device 7.

(6) The recovery chamber 6 is positioned between two inductors 4 in the middle third of the enclosure 11 of the curing and/or drying device 1. The curing and/or drying device 1 represented in FIG. 2 differs from that represented in FIG. 1 in the position of the recovery chamber 6, which is located in the upper third of the enclosure 11.

(7) Also, FIG. 2 also shows a possible example of the distribution of power of the different means of heating, being inductors 4, and burners 5 positioned along the enclosure 11 with, at the bottom of the enclosure, inductors operating at full power (W) in order to facilitate the heating of the coating by conduction from the strip 2 and to promote vaporization of the solvents. The power of the inductors then decreases to reach a low power (W/4) at the top of the enclosure. The catalytic radiants, on the other hand, operate at full power (W) at the top of the enclosure 11 in order to promote cross-linking of the coating and at low power (W/4) at the bottom in order not to hinder the beneficial effect of heating by the strip 2 on the evaporation of the solvents.