Drying and gas or vapor contact with solids – Apparatus – With means to treat gas or vapor
Patent
1989-07-14
1991-04-23
Yuen, Henry C.
Drying and gas or vapor contact with solids
Apparatus
With means to treat gas or vapor
34124, 34119, 432 8, 432 59, F26B 332
Patent
active
050090160
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The invention concerns a method for contact-free drying of a paper or board web, or of any other corresponding continuous web, in which method both infrared radiation and drying air jets are used for drying, the air jets also supporting the web as it runs through the dryer, so that the web is carried free of contact, preferably from two sides, and in which method, after the infrared drying gap, the web is substantially immediately passed into an airborne web-drying gap, wherein the web is supported and dried by means of air jets.
Also included herein is a description of a device intended for carrying out the method of the invention, which device comprises an infrared drying unit and an airborne web-drying unit or airborne web-drying units, which infrared drying unit comprises a series of infrared radiators and an infrared treatment gap fitted in its connection, through which gap the web to be dried can be passed. The airborne web-drying unit or units comprise a box portion, inside of which a nozzle box or boxes are fitted, in connection with which there are nozzle parts, through which drying and supporting air jets are applied to the web to be dried. The infrared drying unit and airborne web-drying unit are integrated with each other both structurally and functionally, and the infrared unit is placed, in the direction of running of the web to be dried, immediately before the airborne web-drying unit.
The present invention relates to the drying of a paper web, board web, or of any other corresponding moving web. A typical object of the invention is the drying of a paper web in connection with its coating or surface-sizing.
As is known in the prior art, paper webs are coated either by means of separate coating devices or by means of on-machine devices or surface-sizing devices integrated in paper machines and operating in the drying section of a paper machine. At the final end of a multi-cylinder dryer, the web to be coated is passed to a coating device, which is followed by an intermediate dryer and finally, e.g., by one group of drying cylinders as an after-dryer. A typical application of the present invention is the intermediate dryer after the coating device, the invention being, however, not confined to the intermediate dryer alone.
In the prior art, so-called airborne web dryers are known, wherein a paper web, board web, or equivalent is dried free of contact. Airborne web dryers are used, e.g., in paper coating devices after a roll coater or a spread coater to support and to dry the web, which is wet with the coating agent, free of contact. In airborne web dryers various blow nozzles and nozzle settings for drying and supporting air are applied. The blow nozzles can be divided into two groups, i.e. pressure or float nozzles, and negative-pressure or foil nozzles, both of which can be applied in the dryer and the method in accordance with the invention.
The prior art airborne web dryers that are used most commonly are based exclusively on air flows. It is partly for this reason that the airborne web dryer becomes quite spacious, since the distance of effect of the airborne web dryer must be relatively long in order that a sufficient high drying capacity could be obtained. Another reason for these drawbacks is that in air drying the depth of penetration of the drying remains relatively low.
In the prior art, different dryers are known which are based on the effect of radiation, in particular of infrared radiation. The use of infrared radiation provides the advantage that the radiation has a relatively high depth of penetration, which depth of penetration is increased when the wavelength becomes shorter. The use of infrared dryers in the drying of paper webs has been hampered, e.g., by the risk of fire, because the temperatures in infrared radiators become quite high, e.g. 2000.degree. C., in order that a drying radiation with a sufficiently short wavelength could be achieved.
With respect to the prior art, reference is made to the German published Patent Applicat
REFERENCES:
patent: 3826014 (1974-07-01), Helding
patent: 3972127 (1976-08-01), Hoshi et al.
patent: 4143468 (1979-03-01), Novotny et al.
patent: 4678433 (1987-07-01), Ellison
patent: 4821427 (1989-04-01), Chern
patent: 4882853 (1989-11-01), Schaft
Ilmanen Reijo
Karlsson Markku
Laakso Sauli
Lepisto Matti
Valmet Oy
Yuen Henry C.
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