Abstract
A nozzlebox for blowing hot gas in the convective drying zone of equipment for the continuous drying of air-borne paper sheets comprises at least one direct impingement nozzle for ejecting a jet of hot gas perpendicular to the average plane of the paper sheet to be dried. The nozzle box comprises a plurality of inclined jet nozzles for ejecting jets of hot gas under an inclined angle with respect to the average plane of the paper sheet to be dried. At least two inclined jet nozzles are provided for which the plane comprising the vector representations of the jet directions of the at least two inclined jet nozzles does not comprise the vector representing the jet direction of a direct impingement nozzle.
Claims
1. Nozzle box for blowing hot gas in the convective drying zone of equipment for the continuous drying of air-borne paper sheets, the nozzle box comprises at least one direct impingement nozzle for ejecting a jet of hot gas perpendicular to the average plane of the paper sheet to be dried; and a plurality of inclined jet nozzles, wherein inclined jet nozzles are provided for ejecting jets of hot gas under an inclined angle with respect to the average plane of the paper sheet to be dried; wherein at least two inclined jet nozzles are provided for which the plane comprising the vector representations of the jet directions of the at least two inclined jet nozzles does not comprise the vector representing the jet direction of a direct impingement nozzle.
2. Nozzle box as in claim 1, wherein the nozzle box comprises at least three inclined jet nozzles, wherein each of the at least three inclined jet nozzles has a vector representing its jet direction when in use; wherein each of the vectors of the at least three inclined jet nozzles has a different direction in the three-dimensional space.
3. Nozzle box as in claim 1, wherein the inclined jet nozzles comprise or consist out of a first set of inclined jet nozzles and a second set of inclined jet nozzles; wherein the first set of inclined jet nozzles are provided for blowing in a first direction; and wherein the second set of inclined jet nozzles are provided for blowing in a second direction; and wherein the first direction is perpendicular to the second direction.
4. Nozzle box as in claim 1, wherein the nozzle box comprises suction openings for the evacuation of gas.
5. Nozzle box as in claim 1, wherein the nozzle box comprises a plurality of nozzle units over the nozzle box, wherein each of the units comprises at least one direct impingement nozzle for ejecting a jet of hot gas perpendicular to the average plane of the paper sheet to be dried; and a plurality of inclined jet nozzles, wherein inclined jet nozzles are provided for ejecting jets of hot gas under an inclined angle with respect to the average plane of the paper sheet to be dried; wherein at least two inclined jet nozzles of the nozzle unit are provided for which the plane comprising the vector representation of the jet directions of the at least two inclined jet nozzles does not comprise the vector representing the jet direction of a direct impingement nozzle of the nozzle unit.
6. Nozzle box as in claim 5, wherein suction openings for the evacuation of gas are provided in the nozzle box between nozzle units.
7. Nozzle box as in claim 5, wherein nozzle units are provided as nozzle heads mounted in the nozzle box.
8. Nozzle box as in claim 5, wherein the at least one direct impingement nozzles are provided in the central section of the nozzle unit; and wherein the inclined jet nozzles surround the at least one direct impingement nozzles.
9. Nozzle box as in claim 8, wherein a first part of said inclined jet nozzles are provided for blowing inwards towards the at least one direct impingement nozzle; and wherein a second part of said inclined jet nozzles are provided for blowing in the direction away from the at least one direct impingement nozzle.
10. Nozzle box as in claim 5, wherein the inclined jet nozzles within a nozzle unit are provided so that when the inclined jet nozzles are in operation, the jets of the inclined jet nozzles are present in equi-angularly distributed planes perpendicular to the nozzle box
11. Equipment for continuous air-borne drying of a paper sheet, comprising a nozzle box as in claim 1, wherein said nozzle box spans the width available in the equipment for the transport of the paper sheet.
12. Equipment as in claim 11, wherein one or more than one nozzle box as in claim 1 is provided such that the vector sum of the vectors representing the jet direction and having as magnitude the jet impulse of the inclined jet nozzles of the nozzle box points in the opposite direction of the direction of transport of the paper sheet through the drying equipment.
13. Equipment as in claim 11, wherein the equipment comprises a multiple number of nozzle boxes as in claim 10; and wherein at least two consecutive nozzle boxes comprise nozzle units that are staggered when comparing the positions of the nozzle units in the first nozzle box of the two consecutive nozzle boxes with the positions of the nozzle units in the second nozzle box of the two consecutive nozzle boxes.
14. A method for continuous drying of a paper sheet, wherein an equipment for continuous drying is used as in claim 11; wherein a paper sheet is transported through the equipment in order to dry the paper sheet in the equipment for continuous drying; wherein the paper sheet is air-borne in the equipment without the selvedge of the paper sheet being held by mechanical means; wherein the paper sheet undulates in the direction of transport of the paper sheet through the drying equipment; and wherein the paper sheet undulates in the direction perpendicular to the direction of transport of the paper sheet through the drying equipment.
15. Method as in claim 14, wherein the vector sum of the vectors representing the jet direction and having as size the jet impulse of the inclined jet nozzles of the nozzle box, points in the opposite direction of the direction of transport of the paper sheet through the drying equipment.
Description
BRIEF DESCRIPTION OF FIGURES IN THE DRAWINGS
[0047] FIG. 1 shows an example of a nozzle box as in the first aspect of the invention.
[0048] FIGS. 2 and 3 respectively show the front and back view of a nozzle head that can be used in the invention.
[0049] FIG. 4 shows an example of a nozzle box as in the first aspect of the invention.
[0050] FIG. 5 shows yet another example of a nozzle box as in the first aspect of the invention.
[0051] FIG. 6 shows the section in paper transport direction; and
[0052] FIG. 7 shows a cross section in the traverse direction of an example of equipment for the continuous air-borne drying of a paper sheet comprising nozzle boxes as in the first aspect of the invention.
[0053] FIG. 8 shows the vectors representing the jets of the inclined jet nozzles of one of the nozzle boxes of the equipment of FIGS. 6 and 7.
[0054] FIG. 9 shows another example of a nozzle box as in the first aspect of the invention.
[0055] FIG. 10 shows an embodiment of equipment for continuous air-borne drying of a paper sheet according to the second aspect of the invention.
[0056] FIG. 11 shows an embodiment of a nozzle box as in the first aspect of the invention.
[0057] FIG. 12 shows air dryer equipment according to the second aspect of the invention.
MODE(S) FOR CARRYING OUT THE INVENTION
[0058] FIG. 1 shows an example of a nozzle box 100 as in the first aspect of the invention. The nozzle box 100 is provided for blowing hot gas in the convective drying zone of equipment for the continuous drying of air-borne paper sheets (including paper board), e.g. for the continuous drying of air-borne coated paper sheets; and is provided for installation across the width of the continuous drying equipment. The nozzle box 100 comprises a plurality of nozzle units 105 over the nozzle box. In the example, the nozzle units 105 are nozzle heads 105, that are removably mounted by means of a bolt 107 and nut onto the nozzle box 100. It is also possible that the nozzle units are integrally formed out of the material of the nozzle box. In the examplealthough not necessarily for the invention, all nozzle heads of the nozzle box have identical nozzle configurations. The nozzle heads 105 are provided staggered over the nozzle box, such that when installed in a drying apparatus, the nozzle units are provided staggered over the width of the drying apparatus. In the example, the first, third, fifth nozzle unit in the nozzle box are linearly aligned; and the second nozzle unit is staggered between the first and third nozzle unit; the fourth nozzle unit is staggered between the third and the fifth nozzle unit. The even numbered nozzle units are linearly aligned; and the odd numbered nozzle units are linearly aligned, but each in a staggered position compared to the even numbered nozzle units. The nozzle units comprise inclined jet nozzles for which the jet direction is oriented towards spaces in between the nozzle units. The even numbered nozzle units comprise inclined jets for blowing into the direction of the space between the even numbered nozzles. The odd numbered nozzle units comprise inclined jets for blowing into the direction of the space between the odd numbered nozzles.
[0059] Other arrangements of the nozzle units or nozzle heads in the nozzle box are possible however, e.g. the nozzle units or nozzle heads can be linearly aligned on the nozzle box, e.g. such that when installed in a drying apparatus, the nozzle units are provided linearly aligned over the width of the drying apparatus.
[0060] FIGS. 2 and 3 respectively show the front (FIG. 2) and back (FIG. 3) view of a nozzle head 105 used in the exemplary nozzle box 100 of FIG. 1. The nozzle head 105 comprises a drilled hole 103 that allows mounting the nozzle head by means of a bolt and nut replaceably into a nozzle box. The nozzle head 105 comprises four direct impingement nozzles 108 for ejecting a jet of hot gas perpendicular to the average plane of the paper sheet to be dried. The nozzle head 105 comprises twelve inclined jet nozzles 109, 110, 111, 112, provided for ejecting jets of hot gas under an inclined angle with respect to the average plane of the paper sheet to be dried. Inclined jet nozzles 109 and 111 are provided for which the plane comprising the vector representation of the jet directions of the inclined jet nozzles 109 and 111 does not comprise the vector representing the jet direction of the direct impingement nozzles 108 of the nozzle unit. On the other hand, the plane formed by the vector representations of the jet directions of the inclined jet nozzles 111 and 112 comprises the vector representing the jet direction of the direct impingement nozzles 108 of the nozzle unit. In the nozzle box head 105, although not necessary for the invention, the direct impingement nozzles 108 are provided in the central section of the nozzle head 105. The inclined jet nozzles 109, 110, 111, 112 surround the direct impingement nozzles 108. Inclined jet nozzles 109 and 110 are provided for blowing inwards towards the direct impingement nozzles 108. The inclined jet nozzles 109, 110, 111, 112 surround the direct impingement nozzles 108. Inclined jet nozzles 111 and 112 are provided for blowing in the direction away from the direct impingement nozzles 108.
[0061] At the inside of the nozzle head 105, a hot gas chamber 122 is provided (see FIG. 3).
[0062] The hot gas chamber is provided for supplying the at least one direct impingement nozzle and the plurality of inclined jet nozzles with hot gas to be ejected by the impingement nozzles and by the inclined jet nozzles. A hot gas chamber in the nozzle box is arranged to provide hot gas to the air chambers of each of the multiple of nozzle heads.
[0063] Optionally, suction openings 125 for the evacuation of gas can be provided in the nozzle box 100 between nozzle heads 105 (see FIG. 1).
[0064] FIG. 4 shows another example of a nozzle box 100 as in the first aspect of the invention. The nozzle box 100 is provided for blowing hot gas in the convective drying zone of equipment for the continuous drying of air-borne paper sheets, e.g. for the continuous drying of air-borne coated paper sheets; and is provided for installation across the width of the continuous drying equipment. The nozzle box 100 comprises a plurality of nozzle units 105 over the nozzle box. In the example, the nozzle units 106 are nozzle heads 106, that are removably mounted by means of a bolt 107 and nut onto the nozzle box 100. It is also possible that the nozzle units are integrally formed out of the material of the nozzle box. In the examplealthough not necessarily for the invention, all nozzle heads of the nozzle box have identical nozzle configurations. The nozzle heads 106 are provided staggered over the nozzle box, such that when installed in a drying apparatus, the nozzle units are provided staggered over the width of the drying apparatus. Other arrangements of the nozzle units or nozzle heads in the nozzle box are possible however, e.g. the nozzle units or nozzle heads can be linearly aligned on the nozzle box, e.g. such that when installed in a drying apparatus, the nozzle units are provided linearly aligned over the width of the drying apparatus.
[0065] The nozzle heads 106 comprise direct impingement nozzles 108 for ejecting a jet of hot gas perpendicular to the average plane of the paper sheet to be dried. Each nozzle head 106 comprises twelve inclined jet nozzles 114, provided for ejecting jets of hot gas under an inclined angle with respect to the average plane of the paper sheet to be dried. In the nozzle box head 106, although not necessary for the invention, the direct impingement nozzles 108 are provided in the central section of the nozzle head 106. The inclined jet nozzles 114 surround the direct impingement nozzles 108. The inclined jet nozzles 114 are provided so that when the inclined jet nozzles 114 are in operation, the jets of the inclined jet nozzles 114 are present in equi-angularly distributed planes perpendicular to the nozzle box 100. Each of the twelve inclined jet nozzles 114 has a vector representing its jet direction when in use; wherein each of the vectors of the twelve inclined jet nozzles 114 has a different direction in the three-dimensional space.
[0066] At the inside of the nozzle head 106, a hot gas chamber is provided. The hot gas chamber is provided for supplying the at least one direct impingement nozzle and the plurality of inclined jet nozzles with hot gas to be ejected by the impingement nozzles and by the inclined jet nozzles. A hot gas chamber in the nozzle box is arranged to provide hot gas to the air chambers of each of the multiple of nozzle heads.
[0067] Optionally, suction openings for the evacuation of gas can be provided in the nozzle box 100 between nozzle heads 106. Alternatively, in the drying equipment specific suction boxes can be mounted aligned with the nozzle box or nozzle boxes.
[0068] FIG. 5 shows yet another example of a nozzle box 100 as in the first aspect of the invention. The nozzle box 100 comprises nozzle units 105 that are linearly aligned on the nozzle box, such that when installed in a drying apparatus, the nozzle units 105 are provided linearly aligned over the width of drying apparatus. Optionally, the nozzle box is provided with suction units 125 in between nozzle units.
[0069] FIG. 6 shows the section 600 in paper transport direction; and FIG. 7 shows a cross section 700 in the traverse direction of an example of equipment for the continuous air-borne drying of a paper sheet (e.g. a coated paper sheet) comprising a plurality of nozzle boxes 670, 770 as in the first aspect of the invention (e.g. as shown in the examples of FIG. 1 or FIG. 4). The nozzle boxes 670 span the width available in the equipment for the transport of the paper sheet 650, 750. The nozzle boxes 770 are mounted laterally in support structures 772. In the example, a first set of nozzle boxes as in the first aspect of the invention is provided above the plane available for transport of the paper sheet; and a second set of nozzle boxes according to the first aspect of the invention is provided below the plane available for the transport of the paper sheet. The coated paper sheet 650 moves through the equipment in the direction indicated by arrow 660. Although not necessary, the equipment comprises rows of infrared emitters 680, e.g. premix gas fired infrared emitters, in between nozzle boxes 670.
[0070] The paper sheet 650, 750 is air-borne in the equipment without the selvedge of the paper sheet being held by mechanical means. The paper sheet 650, 750 undulates in the direction of transport of the paper sheet through the drying equipment. And the paper sheet 650, 750 undulates in the direction perpendicular to the direction of transport of the paper sheet through the drying equipment.
[0071] FIG. 8 shows the vectors representing the jets of the inclined jet nozzles of one of the nozzle boxes of the equipment of FIGS. 6 and 7. Arrow 860 shows the direction of transport of the paper sheet through the drying equipment. Vector V.sub.1 represents the sum of the vectors of the inclined jet nozzles of one nozzle box that have a jet component in the direction of transport of the paper sheet through the equipment; vector V.sub.2 represents the sum of the vectors of the inclined jet nozzles of the same nozzle box that have a jet component in the direction opposite to the direction of transport of the paper sheet through the equipment. Vector V.sub.s is the sum of vectors V.sub.1 and V.sub.2 and has a component in the direction opposite to the direction of transport of the paper sheet through the drying equipment.
[0072] FIG. 9 shows another example of a nozzle box 900 according to the first aspect of the invention. The nozzle box 900 is provided for blowing hot gas in the convective drying zone of equipment for the continuous drying of air-borne paper sheets, the direction of movement of the paper sheet with respect to the nozzle box 900 is indicated by arrow 960. The nozzle box 900 comprises a plurality of nozzle units 905 over the nozzle box. The nozzle units 905 are nozzle heads 905 which are removably mounted by means of a bolt 907 and nut onto the nozzle box 900. The nozzle heads 905 are provided staggered over the nozzle box, such that when installed in a drying apparatus, the nozzle units are provided staggered over the width of the drying apparatus. Each nozzle head 905 comprises two direct impingement nozzles 908 for ejecting hot gas perpendicular to the average plane of the paper sheet to be dried. The nozzle head 905 comprises inclined jet nozzles 909, 911, 912, provided for ejecting jets of hot gas under an inclined angle with respect to the average plane of the paper sheet to be dried. Inclined jet nozzles 909 are provided for ejecting hot gas jets in the transverse direction of the direction of movement of the paper sheet; vectors 995 and 997 show the direction of the ejection of the jets by the inclined jet nozzles 909. Four inclined jet nozzles 911 are provided for ejecting jets in the direction indicated by arrows 991; which is a direction opposite to the direction of movement of the paper. Two inclined jet nozzles 912 blow in the direction indicated respectively by arrow 993 and 994, which make acute angles with the direction of movement of the paper sheet; the two inclined jet nozzles 912 blow away from each other. The provision of inclined jet nozzles 912 of which the jets make an acute angle with the direction of movement of the paper sheet; and wherein the two inclined jet nozzles 912 blow away from each other has shown to result in improved drying efficiency of paper sheet.
[0073] The inclined jet nozzles 912 are provided in the cast nozzle head 905 by drilling a skew orifice. All of the inclined jet nozzles in the nozzle heat 905 are provided in the cast nozzle head via drilling orifices of the same diameter. All of the inclined jet nozzles 909, 911, 912 are supplied with hot gas from the hot gas chamber inside the nozzle heat 905. Therefore, the mass of hot gas ejected per unit of time is the same for each of the inclined jet nozzles 909, 911, 912. The result is that the mass of hot gas ejected per unit of time in the direction opposite to the movement of the paper sheet is larger than the mass of hot gas ejected per unit of time in the direction of the movement of the paper sheet; such arrangement has shown to provide higher efficiency of the drying equipment.
[0074] FIG. 10 shows an embodiment 1000 of equipment for continuous air-borne drying of a paper sheet according to the second aspect of the invention. The equipment 1000 comprises a multiple number of nozzle boxes 1070, 1071 as in the first aspect of the invention. Two consecutive nozzle boxes 1070, 1071 comprise nozzle units 1006 that are staggered when comparing the positions of the nozzle units in the first nozzle box of the two consecutive nozzle boxes with the positions of the nozzle units in the second nozzle box of the two consecutive nozzle boxes. A range of infrared emitters 1080preferably gas fired infrared emittersis positioned between the two consecutive nozzle boxes 1070, 1071. Between a nozzle box and a range of infrared emitters, suction openings 1090 are provided for the evacuation of gas.
[0075] FIG. 11 shows another embodiment of a nozzle box as in the first aspect of the invention. The nozzle box 1100 is provided for blowing hot gas in the convective drying zone of equipment for the continuous drying of air-borne paper sheets, the direction of movement of the paper sheet with respect to the nozzle box 1100 is indicated by arrow 1160. The nozzle box 1100 comprises a plurality of nozzle units 1105 over the nozzle box. The nozzle units 1105 are nozzle heads 1105 which are removably mounted onto the nozzle box 1100. The nozzle heads 1105 are devoid of sharp angles in order to prevent the risk of damaging the paper in case of unplanned contacts between the paper to be dried and the nozzle head. The nozzle heads 1105 are provided staggered over the nozzle box, such that when installed in a drying apparatus, the nozzle units are provided staggered over the width of the drying apparatus. Each of the nozzle heads comprises four direct impingement nozzles 1108 each for ejecting a jet of hot gas perpendicular to the average plane of the paper sheet to be dried. The direct impingement nozzles are provided such that some lines in the direction of the nozzle box that coincide with the width direction of the paper sheet to be dried cross only one direct impingement nozzle of a nozzle head, while other lines in the direction of the nozzle box that coincide with the width direction of the paper sheet to be dried cross two direct impingement nozzles of that same nozzle head, and while other lines in the direction of the nozzle box that coincide with the width direction of the paper sheet to be dried cross no direct impingement nozzles of that same nozzle head. Such arrangement of the direct impingement nozzles has proven to provide better uniformity of heat transfer by the direct impingement nozzles to the paper sheet to be dried.
[0076] Each of the nozzle heads comprises four series of inclined jet nozzles, wherein each of the series of inclined jet nozzles comprises a number of inclined jet nozzles provided on a straight line. Two series of inclined jet nozzles 1110 are each aligned on a line in the direction of the nozzle box that coincides with the width direction of the paper to be dried; of which one series is provided for blowing in the direction of movement of the paper sheet to be dried; and the other series is provided for blowing in the direction opposite to the direction of movement of the paper sheet to be dried.
[0077] The nozzle head comprises in addition two series of inclined jet nozzles 1111, 1112 that are each aligned on a line that makes an angle of e.g. 60 with the direction of the nozzle box that coincides with the width direction of the paper to be dried.
[0078] Each of the nozzlesdirect impingement nozzles as well as inclined jet nozzlesare provided in the nozzle head as drilled round openings perpendicular to the surface of the nozzle head where the round opening has been drilled.
[0079] Between the nozzle heads, the nozzle box is provided with suction openings 1125 for the evacuation of gas.
[0080] The nozzle box arrangement of FIG. 11 has shown particularly beneficial results in terms of drying efficiency of coated paper sheets, thanks to the particular arrangement of the direct impingement nozzles and of the inclined jet nozzles.
[0081] FIG. 12 shows hot air dryer 1200 equipment according to the second aspect of the invention. The hot air dyer equipment 1200 comprises a housing 1201 and a plurality of nozzle boxes 1270 according to the first aspect of the invention. Means are provided for suction of hot gas through suction openingse.g. round suction openings or slit shaped suction openingsin the nozzle boxes (e.g. between nozzle units or between nozzle heads) and/or between nozzle boxes. Means are provided to collect the sucked gas into piping 1202. Preferably, piping 1204 is provided to exhaust part of the sucked gas out of the equipment. Means are provided for the supply of fresh air into the equipment, wherein the freshly supplied airintroduced via piping 1216is mixed with sucked gas. Piping 1224 is provided to recirculatee.g. by means of a fan 1218at least part of the sucked gas back, together with the freshly supplied air, to the one or to the plurality of nozzle boxes for being blown onto the paper sheet to be dried by the direct impingement nozzles and by the inclined jet nozzles of the nozzles boxes. Means 1220 are provided to heat the mixture of sucked gas and freshly supplied air before it is supplied to the nozzle box(es). Such means can e.g. be a heat exchanger or a gas burner. Such gas burner can be provided such that the combustion gas of the gas burner is added to the mixture of sucked gas and freshly supplied air. Meansnot shown in FIG. 12e.g. dampers are provided in the piping to control the flows of the gases in the different pipes or tubes.
