Drying and gas or vapor contact with solids – Apparatus – Rotary drums or receptacles
Patent
1998-08-14
2000-12-19
Wilson, Pamela
Drying and gas or vapor contact with solids
Apparatus
Rotary drums or receptacles
34124, 34128, 34134, 165 89, 165 90, 165 91, F26B 1102
Patent
active
061613029
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a dryer apparatus for paper, cardboard or some other porous fiber web. The invention replaces the pressurized-steam heated cast-iron dryer cylinders available since the nineteenth century.
Development in the art of paper making machines has been slow and concentrated mainly on the so-called wet end. An object of the machine is to dewater pulp pumped onto the machine and formed into an even fiber web. As for a newsprint machine, for example, the dewatering breaks up as follows:
The dryer section constitutes about 80% of the total machine weight and also represents technology from decades ago.
The dryer section of a paper machine, e.g. in the production of cardboard and newsprint, comprises 45-65 cast-iron cylinders, diameter 1.5-1.8 meters, fast rotating (peripheral speed 700-2000 meters/min.) pressure vessels. Carrying a fragile fiber web through such a complicated installation without breaking the same and as required by quality standards is one of the most demanding challenges in paper making. The dryer section also sets strict requirements for the building and subconstructions. Other factors adding to complexity include the passage of a paper web, drive, machine ventilation, pocket ventilation, steam and condensate system, dryer felts, etc.
The "Yankee" cylinder is used for the manufacture of one side glazed (MG-) papers as well as cardboard and creped papers (tissue and industrial crepes). It is a highly massive and demanding body of casting, having a diameter of 3-6 meters, a cylinder length of 3-6 meters, and a weight of 50-100 tons with accessories. Heretofore, there has been no viable, more preferred option available.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the invented apparatus is to substantially simplify and improve the drying of a paper web.
The invention is characterized in that the cylinder interior is fitted with elements for the injection of a hot heat-transfer fluid against the inner surface of the cylinder for heating the surface, as well as elements for discharging the spent fluid from the cylinder interior, said cylinder being tight or sealed for eliminating fluid leaks.
In a preferred embodiment, the cylinder is provided with a dual-jacket, including an outer jacket against whose outer surface the web to be dried is laid, and the heat-transfer fluid injection elements and discharge elements being positioned between said jacket surfaces.
In order to produce a preferred heating effect, the injection elements can be directed towards an upper segment of the inner surface of the outer cylinder jacket and the discharge elements can be respectively mounted on a lower segment within an intermediate space between the jackets.
The dryer cylinder rotates around a large-diameter stationary core cylinder and it is sealed e.g. with an anti-leak packing. The core cylinder may have a diameter which is e.g. 0.5-1.5 meters less than that of the dryer cylinder.
In a preferred embodiment, the heating elements; and discharge elements are stationary relative to the cylinder.
The drying cylinder can be at least partially covered by a drying hood, which is provided with an inlet and outlet duct for a drying medium, such as air, water vapor and/or an inert gas. In view of recovering waste heat, the inlet duct for a drying medium can preferably be in a heat-exchange contact with an inlet and/or outlet duct for a heat-transfer fluid, in addition to which the outlet duct for a drying medium can be fitted with a heat exchanger (13) for recovering its waste heat, e.g. in view of heating water or air.
The present invention relates also to a method for drying fiber webs, such as webs of natural fiber, synthetic fiber and the like, by means of a rotating, substantially horizontal cylinder, the fiber web to be dried being laid against the outer surface thereof. An essential feature in the method is that the inner cylinder surface is injected or sprayed with a hot heat-transfer fluid and that the spent heat-transfer fluid is dis-charged from the
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Mattera Michelle A.
Wilson Pamela
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