Drying and gas or vapor contact with solids – Apparatus – With means to treat gas or vapor
Patent
1988-05-25
1989-11-28
Bennet, Henry A.
Drying and gas or vapor contact with solids
Apparatus
With means to treat gas or vapor
34 68, F26B 332
Patent
active
048828521
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention concerns a procedure for drying moving web material, in which on the material to be dried infrared radiation is directed and in which the moving web material is transported through the radiation zone of an infrared radiator, where the web material to be dried absorbs radiation.
The invention also concerns an IR dryer.
In paper and pulp industry, and in other branches of industry as well, moving web material is dried. Paper manufacturing and paper conversion include a number of steps in which it is necessary to accomplish drying by a non-contact method, that is using appropriate radiation and/or hot gases or air.
Existing types of infrared radiation apparatus used in drying web material consist of high-temperature quartz tube radiators or gas-operated medium wavelength radiators. The wavelength range of high-temperature short wave radiators is mainly 0.5 to 2 .mu.m, with peak at about 1.2 .mu.m. Shortwave radiation is penetrating when drying a thin web, because the coefficient of absorption of the material is poor as a rule in the wavelength range between 0.5 and 2.0 .mu.m, peak absorption usually occurring in the range above 3.0 .mu.m. As a consequence, the emission peak of the radiator and the absorption peak of the material do not coincide. However, high power per unit area is achieved with a high-temperature short wave radiator. The total power may be up to 450 kW/m.sup.2, in which case the radiant power absorbed in the web is more than 100 kW/m.sup.2. Power outputs of the magnitude are required when rapid drying is aimed at; this, in its turn, is required e.g. in the paper coating process. Short wave infrared radiators have also been employed under zone control in order to control the moisture profile of paper web material in the direction across the web.
The wavelength range of medium long wave infrared radiators is mainly 1.5 .mu.m to 6 .mu.m. The wavelength corresponding to maximum intensity is located at about 3.0 .mu.m. The same point is also usually one of the absorption points of the water constituting the object to be evaporated. At this point the cellulose fibres also display good absorptivity. Owing to the circumstances mentioned, the radiation efficiency of the radiation from a medium long wave radiator is high, about 45%, while this figure is about 25-30% for short wave infrared radiation apparatus, or for a high-temperature radiator, in cases in which thin web materials are being dried. The efficiency of both types of radiator increases with increasing material thickness.
The maximum radiation power achievable with medium wave infrared radiators is 60-75 kW/m.sup.2 when using a unilateral radiation source and 120-150 kW/m.sup.2 when using a radiation source on both sides.
The dryer built up with an infrared radiation means, or the IR dryer, is composed of a radiant surface which is located as close as possible to the surface to be dried. In apparatus of prior art, the radiant surface is encapsulated in a housing and the housing is installed, fixedly or provided with a motion mechanism, at a suitable location, attached to the frame structure of the process equipment. In said dryers the use of a counter-reflector is further known which throws back the radiation that has passed through the object being dried and thereby enhances the drying process. Furthermore, prior art knows air-conditioning systems employed in association with IR dryers, which serve the purpose of enhancing the drying and, at the same time, serve as coolers. The IR dryer may moreover comprise a system by which the drying power of the apparatus can be controlled.
Numerous different IR dryers used to dry a moving web, or a web material, are known in the art. Their operation is based on the ability of bodies to emit electromagnetic radiation, which is characteristic of the temperature which the body has. Another characteristic feature of the radiation is that, instead of one single wavelength, the radiator emits a plurality of wavelengths, whereby the characteristic emission
REFERENCES:
patent: 3499232 (1970-03-01), Zimmermann
patent: 3972127 (1976-08-01), Hoshi et al.
patent: 4202112 (1980-05-01), von der Eltz et al.
patent: 4513516 (1985-04-01), Bjornberg
patent: 4565917 (1986-01-01), Furtek
patent: 4594795 (1986-06-01), Stephanson
Bennet Henry A.
Imatran Voima Oy
LandOfFree
Procedure and means for drying moving web material does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Procedure and means for drying moving web material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Procedure and means for drying moving web material will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-574752