Convective hood for heat treatment of a continuous strip

Abstract

A convective hood for transverse installation in a system for continuous heat treatment of moving strip material comprises blowing nozzles for blowing hot gas against the moving strip in an arrangement transverse to the direction of movement of the strip material; and a first transverse suction zone for the suction of hot gas. The first transverse suction zone comprises a first transverse section and a second transverse section. The first transverse section and the second transverse section are provided at the same side downstream or upstream of the movement of the strip material from the blowing nozzles when the convective hood is installed in a system for continuous heat treatment of moving strip material. The second transverse section is provided along the line for movement of the continuous strip material between the first transverse section and the blowing nozzles. The first transverse section comprises suction openings for suction of hot gas directly from outside the convective hood into the convective hood; the suction openings being in closed gas flow connection to a first manifold for recirculation of at least part of this hot gas to the blowing nozzles for blowing the hot gas onto the continuous strip material. The second transverse section comprises suction openings for suction of hot gas directly from outside the convective hood into the convective hood; the suction openings being in closed gas flow connection to a second manifold for exhausting 100% of this hot gas outside of the convective hood.

Claims

1. A convective hood for transverse installation in a system for continuous heat treatment of moving strip material; the convective hood comprises blowing nozzles for blowing hot gas against the moving strip in an arrangement transverse to the direction of movement of the strip material; and a first transverse suction zone for the suction of hot gas; wherein the first transverse suction zone comprises a first transverse section and a second transverse section; wherein the first transverse section and the second transverse section are provided at the same side downstream or upstream of the movement of the strip material from the blowing nozzles when the convective hood is installed in a system for continuous heat treatment of moving strip material; wherein the second transverse section is provided along the line for movement of the continuous strip material between the first transverse section and the blowing nozzles; wherein the first transverse section comprises suction openings for suction of hot gas directly from outside the convective hood into the convective hood; wherein said suction openings are in closed gas flow connection to a first manifold for recirculation of at least part of this hot gas to the blowing nozzles for blowing the hot gas onto the continuous strip material; wherein the second transverse section comprises suction openings for suction of hot gas directly from outside the convective hood into the convective hood; wherein said suction openings are in closed gas flow connection to a second manifold for exhausting 100% of this hot gas outside of the convective hood, wherein in between the blowing nozzles, additional suction openings are provided for the suction of hot gas, and wherein the additional suction openings are in flow connection with the second manifold for the evacuation out of the convective hood of all gas sucked by the additional suction openings.

2. The convective hood as in claim 1, wherein the first transverse section is provided for suction of hot gas from a first transversal section at the moving strip material; and wherein the second transverse section is provided for suction of hot gas from a second transversal section at the moving strip material.

3. The convective hood as in claim 1, wherein suction openings of the second transverse section of the first transverse suction zone are provided such that when the convective hood is used in a system for continuous heat treatment of moving strip material, the suction openings of the second transverse section are located in a plane parallel with the average plane in which the strip material runs through the system.

4. The convective hood as in claim 1, wherein the convective hood comprises an individual fan; wherein the individual fan is provided for the suction of hot gas by suction nozzles of the first transverse section of the first transversal suction zone and for blowing hot gas by the blowing nozzles.

5. The convective hood as in claim 1, wherein at the other side of the blowing nozzles than where the first transverse suction zone is provided, a second transverse suction zone comprising suction nozzles is provided; wherein the suction nozzles of the second transverse suction zone are all in flow connection with the second manifold for evacuation out of the convective hood of all gas sucked by the suction nozzles of the second transverse suction zone.

6. The convective hood as in claim 1, wherein said suction openings of the first transverse section are in closed gas flow connection to a first manifold for recirculation of 100% of this hot gas to the blowing nozzles for blowing the hot gas onto the continuous strip material.

7. A system for continuous heat treatment of moving strip material, comprising a plurality of convective hoods as in claim 1; and at least one radiant emitter transversally installed to the direction of movement for strip material; wherein two consecutive convective hoods are separated from each other in the direction of movement of the strip material by at least one radiant emitter, wherein at least one of the convective hoods comprises a first transversal suction zone wherein a first transversal section and a second transversal section is provided in the convective hood in the upstream direction of movement of the strip material from the blowing nozzles, wherein the system comprises a central fan for the suction of hot gas by the suction nozzles of the second transversal sections of the first transversal suction zones of the convective hoods; wherein said central fan is provided for blowing the hot gas sucked by it into piping for exhausting the hot gas out of the system.

8. The system as in claim 7, wherein each of the convective hoods comprises an individual fan; wherein the individual fan is provided for the suction of hot gas by the suction nozzles of the first transversal sections of the first transversal suction zone of the convective hood and for blowing hot gas by the blowing nozzles of the same convective hood.

9. The system as in claim 7, wherein the radiant emitter comprises gas-fired radiant burners or wherein the radiant emitter comprises electrical radiant emitters.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a longitudinal cross section of a system for continuous heat treatment of moving strip material, comprising a plurality of convective hoods as in the first aspect of the disclosure.

(2) FIG. 2 shows a view of a convective hood according to the first aspect of the disclosure.

DETAILED DESCRIPTION

(3) FIG. 1 shows a longitudinal cross section along the direction of movement of the strip material of a system 100 for continuous heat treatment of moving strip material 102. The strip material 102 can e.g. be paper or board. The system 100 can e.g. be installed downstream of coating equipment for coating paper, to dry and cure the coating. The direction of movement of the strip material through the system is indicated by arrow 103. The system comprises two convective hoods 110, 111 as in the first aspect of the disclosure, transversely installed to the direction of movement of the continuous strip material. The two consecutive convective hoods are separated from each other in the direction of movement of the strip material by at least one radiant emitter 115. FIG. 1 shows two convective hoods 110, 111; however it must be understood that more convective hoods can be installed, with each time radiant emitters transversally installed between two consecutive hoods.

(4) Although FIG. 1 only shows convective hoods and radiant emitters on one side of the strip material, a plurality of convective hoods, with in between radiant emitters, can be installed on both sides of the strip material.

(5) The radiant emitters 115 can comprise gas-fired radiant burners. Next to infrared radiation, the gas-fired radiant burners produce hot combustion gas that is conveyed towards the strip material that is to be heat treated. It is also possible that the radiant emitter comprises electrical radiant emitters. Besides infrared radiation to the strip material, the electrical radiant heaters will heat the gas at the strip material.

(6) The convective hoods 110, 111 comprise blowing nozzles 120, 122 for blowing hot gas against the moving strip for convective heat treatment of the moving strip. The blowing nozzles are installed in an arrangement transverse to the direction of movement of the strip material. The convective hoods further comprise a first transverse suction zone 130, 132 for the suction of hot gas. The first transverse suction zone comprises a first transverse section 140, 142 and a second transverse section 144, 146. The first transverse section and the second transverse section are provided at the same side downstream or upstream of the movement of the strip material from the blowing nozzles. The second transverse section 144, 146 is provided along the line for movement of the continuous strip material between the first transverse section 140, 142 and the blowing nozzles 120, 122. The first transverse section 130, 132 and the second transverse section 144, 146 of the first transverse suction zone 130, 132 will suck hot gas from outside the hood, from at the strip material 102. By their positioning, the first transverse section 130 will suck warmer gas with less moisture content than the second transverse section, as the first transverse section is provided for suction of hot gas from at a first transversal section at the moving strip material; and as the second transverse section is provided for suction of hot gas from at a second transversal section at the moving strip material.

(7) The first transverse section 140, 142 comprises suction openings 150 for suction of hot gas directly from outside the convective hood into the convective hood. The suction openings 150 are in closed gas flow connection to a first manifold 160 for recirculation of at least part, and optionally 100%, of this hot gas to the blowing nozzles 120, 122 for blowing the hot gas onto the continuous strip material 102. To this end, a or each convective hood can comprise an individual fan 162, provided for the suction of hot gas by the suction nozzles 150 of the first transverse section of the first transversal suction zone of a convective hood and for blowing hot gas by the blowing nozzles of the same convective hood.

(8) In the example of FIG. 1, suction openings 150 of the first transverse section 130, 132 of the first transverse suction zone 140, 142 are provided in a segment of the convective hood which tapers between the convective hood and the strip material in the direction of the second transverse section of the suction zone of the convective hood. The taper angle (the angle made with the strip material) is e.g. 45°.

(9) The second transverse section 144, 146 comprises suction openings 152 for suction of hot gas directly from outside the convective hood into the convective hood; these suction openings 152 are in closed gas flow connection to a second manifold 164 for exhausting 100% of this hot gas outside of the convective hood. To this end, the system can comprise a central fan (not shown in FIG. 1) for the suction of hot gas by the suction nozzles of the second transversal sections of the first transversal suction zones of the convective hoods. The central fan is provided for blowing the hot gas sucked by it into piping for exhausting the hot gas out of the system.

(10) In the example of FIG. 1, the suction openings 152 of the second transverse section 144, 146 of the first transverse suction zone 130, 132 are provided such that in the system for continuous heat treatment of moving strip material, the suction openings are located in a plane parallel with the average plane in which the strip material runs through the system.

(11) In the exemplary hoods of FIG. 1, at the other side of the blowing nozzles 120, 122 than where the first transverse suction zone 130, 132 is provided, a second transverse suction zone 166, 168 comprising suction nozzles 170 is provided. The suction nozzles 170 of the second transverse suction zone 166, 168 are in the example all in flow connection with the second manifold 164, for evacuation of the sucked gas out of the system by means of the central fan (not shown in FIG. 1).

(12) In the system of FIG. 1, the first convective hood 110 encountered by the strip material when moving through the system comprises a first transverse suction zone 140 installed in the convective hood in the direction downstream from the blowing nozzles of the movement of the strip material.

(13) The system of FIG. 1 comprises a convective hood 111 in which the first transverse suction zone 142 is provided in the convective hood 111 in the upstream direction of movement of the strip material from the blowing nozzles. When more than two convective hoods are installed at the same side of the strip material to be treated, the convective hoods located further downstream may be positioned according to this configuration.

(14) FIG. 2 shows a planar view at the suction nozzles and blowing nozzles of the convective hood 111 of FIG. 1. FIG. 2 shows the first transverse suction zone 242 with its suction openings 250 and the second transverse suction zone 246 with its suction openings 252. In between the blowing nozzles 222, additional suction openings 272 are provided for the suction of hot gas. To this end, the blowing nozzles 222 can be provided as blowing openings in blowing heads 274 (shown in 174 in FIG. 1). The blowing heads 174, 274 are each supplied with hot air from a manifold via piping 176 (see FIG. 1). The manifold can be supplied by hot air from the individual fan 162 (of FIG. 1) of the convective hood. In the example, the additional suction openings 272 (FIG. 2) are in flow connection with the second manifold 164 (FIG. 1) for evacuation by the central fan (not shown in the figures) out of the system.

(15) FIG. 1 shows a system for continuous heat treatment of moving strip material installed at one side of the moving strip only. It is possible to install a similar system at the other side of the moving strip as well, in order to treat both sides of the strip material. Although some features, concepts or aspects of the embodiments may be described herein as being a preferred (more or less) arrangement or method, or an advantageous arrangement or method, such description is not intended to suggest that such feature or features are required or necessary unless expressly so stated.