Gas fired radiant emitter

Abstract

Gas fired radiant emitter having a premixing chamber for preparing a premix of gas and air; a perforated ceramic plate acting as burner deck; and a pilot burner having a premix gas supply flow tube and two electrodes. The premix gas supply flow tube of the pilot burner extends from the side of the perforated ceramic plate where the premixing chamber is located, into a through hole in the perforated ceramic plate. The premix gas supply flow tube has a gas exit in the through hole in the perforated ceramic plate or at the combustion side of the perforated ceramic plate. The gas fired radiant emitter has features so that in an area of the perforated ceramic plate around where the premix gas supply flow tube extends into a through hole in the perforated ceramic plate, no premix gas flows through the perforated ceramic plate.

Claims

1. A gas fired radiant emitter comprising: a premixing chamber for preparing a premix of gas and air; a perforated ceramic plate acting as burner deck, onto which the premix of gas and air can be combusted after it has flown through the perforations of the perforated ceramic plate; a pilot burner comprising a premix gas supply flow tube and two electrodes; wherein the premix gas supply flow tube of the pilot burner extends from the side of the perforated ceramic plate where the premixing chamber is located, into a through hole in the perforated ceramic plate; and wherein the premix gas supply flow tube has a gas exit in the through hole in the perforated ceramic plate or at the combustion side of the perforated ceramic plate; and wherein means are provided so that when the emitter is in use, in an area of the perforated ceramic plate around where the premix gas supply flow tube extends into a through hole in the perforated ceramic plate, no premix gas flows through said area of the perforated ceramic plate, wherein the through hole comprises an annular opening around the pilot burner, and wherein the annular opening creates a fluid flow connection between both surfaces of the perforated ceramic plate; and wherein no combustible gas flows through the annular opening.

2. The gas fired radiant emitter as in claim 1, wherein the two electrodes are arranged such that in use a flame of the pilot burner is present at the gas exit of the premix gas supply flow tube.

3. The gas fired radiant emitter as in claim 1, wherein the area of the perforated ceramic plate around where the premix gas supply flow tube extends into a through hole in the perforated ceramic plate where no premix gas flows through the ceramic plate, comprises at least a number of perforations of the perforated ceramic plate.

4. The gas fired radiant emitter as claim 1, wherein the area of the perforated ceramic plate around where the premix gas supply flow tube extends into a through hole in the perforated ceramic plate where no premix gas flows through the ceramic plate, does not comprise perforations in the ceramic plate open for gas flow.

5. The gas fired radiant emitter as in claim 1, wherein said means comprise a seal for sealing off an area of the ceramic plate from the premixing chamber.

6. The gas fired radiant emitter as in claim 1, wherein the gas premix flow tube extends into a through hole of the perforated ceramic plate without the pilot burner making contact with the perforated ceramic plate.

7. The gas fired radiant emitter as in claim 1, wherein the two electrodes extend from the side of the perforated ceramic plate where the premixing chamber is located, and into the through hole in the perforated ceramic plate.

8. The gas fired radiant emitter as in claim 1, wherein the pilot burner can be dismounted and replaced in the gas fired radiant emitter without having to open the premixing chamber.

9. The gas fired radiant emitter as in claim 1, wherein the gas fired radiant emitter comprises a housing enclosing the premixing chamber; and wherein the pilot burner is releasably connected to the housing, such that the pilot burner can be dismounted and replaced without having to open the premixing chamber.

10. The gas fired radiant emitter as in claim 1, comprising a cooling flow tube around the premix gas supply flow tube extending from the side of the perforated ceramic plate where the premixing chamber is located, for providing a cooling air flow for cooling at least part of the length of the premix gas supply flow tube.

11. The gas fired radiant emitter of claim 10, wherein the cooling flow tube is provided with means to exit its cooling air at the housing that delimits the premixing chamber of the radiant emitter; or wherein the cooling flow tube is provided with means to enter cooling air into the cooling flow tube at the housing that delimits the premixing chamber of the radiant emitter.

12. A gas fired radiant emitter comprising: a premixing chamber for preparing a premix of gas and air; a perforated ceramic plate acting as burner deck, onto which the premix of gas and air can be combusted after it has flown through the perforations of the perforated ceramic plate; a pilot burner comprising a premix gas supply flow tube and two electrodes; wherein the premix gas supply flow tube of the pilot burner extends from the side of the perforated ceramic plate where the premixing chamber is located, into a through hole in the perforated ceramic plate; and wherein the premix gas supply flow tube has a gas exit in the through hole in the perforated ceramic plate or at the combustion side of the perforated ceramic plate; and wherein means are provided so that when the emitter is in use, in an area of the perforated ceramic plate around where the premix gas supply flow tube extends into a through hole in the perforated ceramic plate, no premix gas flows through said area of the perforated ceramic plate; further comprising one or more radiation screens positioned on the combustion side at a distance from the perforated ceramic plate; and wherein at least one of the one or more radiation screens has an opening where the premix gas supply flow tube extends into a through hole of the perforated ceramic plate.

13. A radiant oven for treating continuously moving web of sheet material, comprising a number of gas fired radiant emitters positioned over the width of the radiant oven; wherein at least one of the gas fired radiant emitters is a gas fired radiant emitter as in claim 1.

14. The radiant oven as in claim 13, wherein the pilot burner is configured to be dismounted without having to dismount from the radiant oven the gas fired radiant emitter which comprises the pilot burner.

15. A method of using the gas fired radiant emitter as in claim 1 in a radiant oven, comprising the steps of firing the gas fired radiant emitter at a power density of at least 100 kW/m.sup.2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a gas fired radiant emitter according to the first aspect of the invention.

(2) FIG. 2 shows a view perpendicular to the burner deck of an exemplary gas fired radiant emitter according to the invention.

(3) FIGS. 3 and 4 show embodiments of the invention.

(4) FIG. 5 schematically shows a radiant oven according to the second aspect of the invention.

(5) FIG. 6 shows a gas fired radiant emitter according to the first aspect of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(6) FIG. 1 shows a gas fired radiant emitter 100 according to the invention.

(7) The gas fired radiant emitter 100 comprises a premixing chamber 110 for preparing a premix of gas and air; a perforated ceramic plate 120 acting as burner deck, onto which the premix of gas and air can be combusted after it has flown through the perforations of the perforated ceramic plate; and a pilot burner 130 comprising a premix gas supply flow tube and two electrodes 160, 170. A non-electrically conductive separation part 165 spaces the two electrodes 160 and 170 from each other. The two electrodes 160, 170 extend from the side of the perforated ceramic plate where the premixing chamber 110 is located, and preferably into the through hole in the perforated ceramic plate. The pilot burner 130 comprises a premix gas supply 133 and electrical connections 135 to a control unit (not shown on the figure).

(8) The premix gas supply flow tube 140 of the pilot burner extends from the side of the perforated ceramic plate where the premixing chamber 110 is located, into a through hole 180 in the perforated ceramic plate 120. The premix gas supply flow tube 140 has a gas exit in the through hole 180 in the perforated ceramic plate 120 or at the combustion side of the perforated ceramic plate 120.

(9) Means 192, 194 are provided so that when the emitter is in use, in an area of the perforated ceramic plate 120 around where the premix gas supply flow tube 140 extends into a through hole 180 in the perforated ceramic plate; no premix gas flows through the perforated ceramic plate 120.

(10) In the example of FIG. 1, the means comprise a partition wall 192 in the cast iron housing 190 of the radiant emitter 100, in combination with a seal 194 between the partition wall 192 and the perforated ceramic plate 120.

(11) The housing comprises an inlet 195 to supply premix gas to the premixing chamber 110.

(12) The radiant emitter 100 further comprises side flanges 196 and connection means 197 to connect the side flanges 196 to the housing 190.

(13) The pilot burner 130 is releasable connected to the housing 190, such that the pilot burner 130 can be dismounted and replaced without having to open the premixing chamber 110.

(14) FIG. 2 shows a view at the side where the premixing chamber is located perpendicularly to the burner deck of an exemplary gas fired radiant emitter according to the invention. The gas premix flow tube 240 extends into a through hole 280 of the perforated ceramic plate 220 without the pilot burner and the gas premix flow tube 240 making contact with the perforated ceramic plate 220. Sealing means 294 are provided so that when the emitter is in use, in an area of the perforated ceramic plate 220 around where the premix gas supply flow tube 240 extends into a through hole 280 in the perforated ceramic plate; no premix gas flows through the perforated ceramic plate 220. In the example, the gas fired radiant emitter comprises a second perforated ceramic plate 222, positioned sidewise to the perforated ceramic plate 220. Between the two perforated ceramic plates 220, 222, a seal 223 is provided. In the example, each of the perforated ceramic plates 220, 222 have a surface area of 11628 mm.sup.2. The area of the perforated ceramic plate 220 around where the premix gas supply flow tube 240 extends into a through hole 280 in the perforated ceramic plate; and where no premix gas flows through the ceramic plate 220 is 1598 mm.sup.2.

(15) In alternative embodiments, no perforations are present in the ceramics plate 220 in the area within the sealing means 294 around where the premix gas supply flow tube 240 extends into a through hole 280 in the ceramic plate 220.

(16) In yet an alternative embodiment, the perforations present in the ceramics plate 220 in the area within the sealing means 294 around where the premix gas supply flow tube 240 extends into a through hole 280 in the ceramic plate 220 are clogged, e.g. by means of a ceramic material, thereby making the perforations impervious to gasses.

(17) The gas fired radiant emitter 100 shown in FIG. 1 comprises in the pilot burner 130 a cooling flow tube 137 around the premix gas supply flow tube 140, extending from the side of the perforated ceramic plate where the premixing chamber 110 is located. The cooling flow tube 137 is provided with an inlet chamber 138 to supply compressed air and with one or more holes 139 to exit the cooling air at the housing 190 that delimits the premixing chamber 110 of the radiant emitter 100.

(18) Alternatively, air can be sucked via holes 139, through the cooling flow tube 137 and exiting the cooling flow tube 137 at the level of chamber 138 via holes not shown in FIG. 1.

(19) The gas fired radiant emitter 100 of FIG. 1 comprises two radiation screens 125, 128 positioned on the combustion side at a distance from the perforated ceramic plate 120. The radiation screen 125, which is located closest to the perforated ceramic plate 120, is interrupted where the premix gas supply flow tube 140 extends into a through hole 180 of the perforated ceramic plate 120.

(20) As an example, the radiation screen 125 can be formed by a series of bars out of a temperature resistant material (e.g. appropriate ceramic material), wherein one or more bars are missing thereby creating the interruption where the premix gas supply flow tube extends into a through hole of the perforated ceramic plate.

(21) FIG. 3 schematically shows a gas fired radiant emitter according to the first aspect of the invention wherein the premix gas supply flow tube 340 has a gas exit in the through hole 380 in the perforated ceramic plate 320. A partition wall 392, in combination with a seal 394 between the partition wall 392 and the perforated ceramic plate 320 is provided as means so that when the emitter is in use, in an area of the perforated ceramic plate 320 around where the premix gas supply flow tube 340 extends into a through hole 380 in the perforated ceramic plate; no premix gas flows through the perforated ceramic plate 320.

(22) FIG. 4 schematically shows a gas fired radiant emitter according to the first aspect of the invention wherein the premix gas supply flow tube 440 has a gas exit at the combustion side of the perforated ceramic plate 420. A partition wall 492, in combination with a seal 494 between the partition wall 492 and the perforated ceramic plate 420 is provided as means so that when the emitter is in use, in an area of the perforated ceramic plate 420 around where the premix gas supply flow tube 440 extends into a through hole 480 in the perforated ceramic plate; no premix gas flows through the perforated ceramic plate 420.

(23) FIG. 5 schematically shows a radiant oven 500 for treating continuously moving web of sheet material according to the second aspect of the invention. A web-like (e.g. paper) or sheet-like (e.g. a steel strip) material 510 is lead through the continuous oven 500 in the direction of arrow 520. The radiant oven 500 comprises a number of gas fired radiant emitters 530, 540, 550 positioned over the width direction of the oven 500. At one end of the row of radiant emitters, a gas fired radiant emitter 530 is located according to the first aspect of the invention wherein the pilot burner 580 is arranged for igniting the gas fired radiant emitter. At the other end of the row of radiant emitters, a gas fired radiant emitter 550 is located according to the first aspect of the invention wherein the pilot burner 580 is arranged for detecting flames on the burner deck of the gas fired radiant emitter.

(24) FIG. 6 schematically shows a gas fired radiant emitter according to the first aspect of the invention. The emitter comprises a radiant screen 695, e.g. a woven wire mesh. The premix gas supply flow tube 640 has a gas exit at the combustion side of the perforated ceramic plate 620, where the premix gas supply flow tube 640 extends through an opening in the radiant screen 695. A partition wall 692, in combination with a seal 694 between the partition wall 692 and the perforated ceramic plate 620 is provided as means so that when the emitter is in use, in an area of the perforated ceramic plate 620 around where the premix gas supply flow tube 640 extends into a through hole 680 in the perforated ceramic plate; no premix gas flows through the perforated ceramic plate 620.