FI57455B - ANORDING FOR THE TORKNING OF SUSPENSION EXV CELLULOSA - Google Patents

Description

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Patent and Registration Office ............. . .

'(44) Date of departure and delivery date. -

Patent- och registerstyreleen 'Antokin utltgd och uti.tkriftan pubiicand 30. Oh. 80 (32) (33) (31) Pyydattjr etuelkeu »- Begird prlerltat 15.05.72 USA (US) 253198 (71) Improved Machinery, Inc., Nashua, New Hampshire, USA (US) (72) Oscar Luthi, Nashua, New Hampshire, Lawrence A. Carlsmith, Amherst,

New Hampshire, USA (US) (7M Berggren Oy Ab (5M Apparatus for washing and drying suspensions, e.g. cellulose -Anordning för tvättning och torkning av suspensioner, exv. Cellulosa

The invention relates to an apparatus for washing and drying suspensions, e.g. cellulose, in which at least two screen drums arranged on parallel shafts are arranged in a common pressure vessel so that the jacket surfaces are formed so as to form a sink between them. under the action of the washing liquid are resiliently pressed against the pulp layer formed on the screen drums.

The object of the invention is to provide a new, better device which is constructed and adapted in particular for washing and drying suspensions containing cellulose, such as pulp slurry. The invention is characterized in that the suspension is adapted to flow under pressure into the inner wall of the pressure vessel at its upper end at the upper end of the tapered channel formed by the pressure plate and the screen surface of the screen drum 57455 from its own feed member for each screen drum to a pressurized space defined by the press plate and the pressure vessel wall so that the press plate remains resiliently pressed against the pulp layer formed on the screen drum jacket and the wash liquid escapes from the free leaving edge of the press plate.

With the pressure plate according to the invention, which extends along an essential part of the outer circumference of the screen drum, the suspension can be fed considerably thicker than is possible with known devices.

This advantage of the device is further emphasized by the fact that the fibrous material is still compressed in the drain between the screen drums, and the structure fitted to the common detergent tank also allows an additional pressure plate to be inserted between the drums before the drain. The elongated pressing plate also gives the pulp layer a better shape than the short rubber or plastic strips according to known devices. The invention also achieves the great advantage of avoiding the need for vacuum or counter-pressure of known devices when forming a pulp layer on a screen drum. In addition, the capacity of the two-drum device is high, even if it handles a thicker suspension than normal.

Other advantages of the invention will become apparent from the following description and the accompanying drawing, in which a preferred embodiment of the invention is shown by way of illustration only.

The figure of the drawing is a vertical sectional view of a device according to the invention.

The drawing, in which the same reference numerals denote corresponding parts, shows a device comprising two sieve drums 142, 144 of annular cross-section, mounted for rotation about parallel axes and enclosed inside a pressure vessel, i.e. a container 146. The drums 142, 144 have circumferential, permeable jacket surfaces, i.e. screen surfaces 148, between which a drain 150 remains, and which have conventional axial liquid or filtrate outlet passages connecting the holes of the jacket surfaces 148 to the filtrate outlet lines at opposite ends of the drums 142, 144. The drums 142, 144 are provided with drum-specific scraper blades 152 which remove compressed solids from the filter member 148 and an outlet line 154 which is open into the container 146 along its entire length to receive the compressed solids therefrom. The discharge line 154 has a conventional discharge coil 156 which rotates in the direction of rotation schematically indicated by the arrow, tearing the solid and conveying it away from the press.

The drums 142, 144 are provided with jets 158 for spraying washing liquid onto the jacket surfaces 148 after the scraper blades 152 have removed solids therefrom. Leakage around the ends of the drums 142, 144 is prevented by suitable, conventional sealing devices (not shown). When the device according to the drawing operates, the drums 142, 144 are continuously rotated in the opposite directions of rotation marked in the drawing and described in Finnish patent application 1569/72, i.e. one of the drums 142, 144 can move laterally with respect to the other to vary the cross-section of the throat 150, drums 142, 144 with the axes remaining parallel.

The apparatus includes supply means through which a pressurized liquid suspension containing fibrous material can be fed to both jacket surfaces 148 of the drums 142, 144 in the direction of rotation of the drums. More specifically, the device includes a separate supply line 160 for each drum 142, 144, which communicates with a pressurized source of liquid suspension and is adapted to supply the suspension to a container 146 near the top of each drum 142, 144. In addition, near each feed tube 160 is a resilient sealing strip 162 that contacts the sheath 148 of the respective drum 142, 144 along its entire length and prevents suspension from the feed tube 160 from flowing around the drum 142, 144 in the opposite direction of rotation.

Immediately after the discharge point of each feed tube 160 into the vessel 146, a non-perforated curved barrier plate, i.e., a second pressure plate 164 extending the full length of the vessel 146, is rigidly attached to the vessel wall 168 so that a curved chamber 166 remains between the feed tube 160 and the respective drum 142 or 144. . The non-perforated pressure plate 170, which also extends over the entire length of the sheath surfaces, extends curved along the outer periphery of each sheath surface 148 from the exit end of the respective barrier plate 164. Each compression plate 170 preferably has a curved length greater than about 40 ° and shorter than about 120 ° from the circumference of the respective drum 142, 144, and the total arc length of each pair of plates 164, 170 is preferably greater than about 80 ° and less than about 180 ° from said drum circumference. .

Each compression plate 170 is articulated at its leading edge, secured so that it can move toward and away from its respective screen drum 142, 144 on the pivot pin 172, and each plate 170 divides its entire length into an inner chamber 174 and an outer chamber 176. Each inner chamber 174 is connected. it with the space 166 in the direction of rotation of the respective drum 142, 144, and externally the chamber 174 is bounded by the inner surface of the plate 170 and internally by the drum jacket surface 148. Each outer chamber 176 is bounded externally by the vessel wall 168 and internally by the outer surface of the pressure plate 70.

A plurality of laterally spaced reinforcing ribs 178 are rigidly attached to the outer surface of each press plate 170, extending over most of the arc length of the plate 170 and preventing most of it from bending, but terminating shortly before the trailing edge of the plate 170 so that the trailing edge of each press plate 170 . The inner surface of each press plate 170, at least near the trailing edge of the plate, is coated with a low friction material such as polytetrafluoroethylene, or TFE. Opposite side edges of each plate 170 are at a small clearance from the end walls of the container, and there are suitable, resilient seals between each side edge and its adjacent end wall (not shown) to prevent suspension from flowing past the side edges of the plates 170.

Attached to each compression plate 170 are a plurality of pressure medium power devices 182 spaced across the width of the plate near the trailing edge of the plate to force the plate 170 toward the respective drum 140, 142. The power devices 182 can, of course, be used to resiliently press the plates 170 toward the sheath surfaces 148 throughout the operation of the device, but it is intended that the plates 170 be lifted toward the sheath surfaces 148 only initially, after the device has been started. Near the inlet edge of each pressure plate 170 is a supply line 184 which communicates with a source of pressurized fluid such as water and is adapted to supply fluid to the space 176 outside the pressure plate 170. The pressure fluid supplied upstream 184 is used as a means to resiliently compress pressure during operation, and causes each press plate 170 to gradually approach the jacket surface 148 in the direction of rotation of the respective drum 142, 144. As shown in the drawing, the exit ends of the chambers 176 are also in open communication with portions of the jacket surfaces 148 that follow the exit ends of the press plates 170 so that liquid can be used to further wash solids accumulated on the jacket surfaces 148 after the solids have rotated past the exit edges of the press plates 170.

As shown in the drawing, each drum 142, 144 may, if desired, be provided with a curved press plate 186 extending the entire length of the drum jacket surface 148 and located between the trailing edge of the press plate 170 and the drain 150. As shown in the drawing, these pressure plates 186 may be attached to a common support 188 which can be compressed toward the drain 150 by a plurality of pressure medium driven power devices 190.

During operation, the drums 142, 144 are continuously rotated in the opposite directions indicated by the arrows indicated in the drawing, and the pressure fluid supplied along the supply lines 184 compresses the plates 170 previously raised by the power devices 182 so that the plates 170 each approach their respective drums 142, 144 in the direction of rotation. .

A pressurized liquid suspension containing fibrous material is continuously fed to the vessel 146 down the feed tubes 160 and flows through the chambers 166, 174 in communication with each other up to the drum 142, 144 in the direction of rotation of the drum. As the fluid suspension passes through the chambers 166, the suspension pressure forces fluid to flow inwardly through the screen surfaces 148, initiating the formation of mats on the screen surfaces 148. As the suspension passes through the spaces 174, the inner surfaces of the press plates 170 are in contact with the fibrous material accumulated on the jacket surfaces 148. water, thus forcing considerably more liquid to flow from the suspension through the screen surfaces 148.

6 57455

The fibrous material which has passed past the trailing edges of the plates 170 due to the rotation of the drums 142, 144 is first washed by the washing liquid flowing from the spaces 176, then compressed by the pressure plates 186, and once again compressed in a throat 150 by each drum 142, 144. with. The material is then removed from the drums 142, 144 by means of scraper blades 152 and removed from the device by means of a screw 156.

Although only one embodiment of the invention has been shown and described in detail above in the drawing, the invention is not limited to this embodiment alone, but also encompasses other embodiments within the scope of the appended claims.

Claims (4)

7 57455 Apparatus for washing and drying suspensions, e.g. cellulose, in which at least two screen drums (142, 144) arranged on parallel axes are arranged to rotate in a common pressure vessel (146j) so that the jacket surfaces (148) are formed so as to form a drain (150) therebetween. wherein each screen drum (142, 144) has its own suspension supply member (16o), the device having compression members which resiliently press against the pulp layer formed on the screen drums under the action of the pressurized washing liquid, characterized in that the suspension is adapted to flow under pressure in the pressure vessel 146 ) to the upper end of the tapered channel (166) formed by the pressure plate (170) and the screen surface of the screen drum (142, 144) at its front end, and that the pressure plate (170) extends along the outer side of the screen (148) of the screen drum (142, 144). an integral part of the circumference and is under the pressure of the washing liquid which is passed to each screen drum (142, 144). from its own feed member (184) to a pressurized space (176) defined by the press plate (170) and the wall of the pressure vessel (146) so that the press plate remains resiliently pressed against the pulp layer formed on the screen (142, 144) of the screen drum (142, 144). ), and the washing liquid enters the screen drum jacket from the free leaving edge (180) of the press plate (170). Device according to claim 1, characterized in that an additional pressure plate (186) for each screen drum (142, 144) is provided between the drain (150) and the trailing edges (180) of each pressure plate (170). Device according to claim 1 or 2, characterized in that each screen drum (142, 144) further has a stationary pressure plate (164) which, together with the oscillatingly mounted pressure plate (170), extends along the circumference of each screen drum by an arc greater than than 80 ° but less than 180 °. Device according to claim 2 or 3, characterized in that the additional pressure plate (186) of each screen drum (142, 144) is movable independently of the other pressure plates (164, 170) and in that this pressure plate (186) has means (190) for adjusting it against opposite screen drums.