FI68005C - FOERFARANDE FOER TJOCKNING AV MASS ELLER SUSPENSION OCH SKIVFILTER FOER TILLAEMPNING AV FOERFARANDET - Google Patents

Description

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^ (11 * UTLÄGGN! NGSSKRIFT 68005 ϊ'ί'λΒ c («) '13 7 1: 3 (51) Kv.lkd / Int.CI. * B 01 D 33/26 FINLAND —FINLAND (^) Patent application - Patentansöknlng 803100 (22) Application date - Ansökningsdag 30 Q9 80 (Fl) (23) Starting date —Glltighetsdag 30 09 80 (41) Has become public - Bllvit offentlig 3 ^ 03 82

National Board of Patents and Registration Date of publication and month of publication. - __ q

Patent and registration authorities in the United States of America and the Public Procurement Act .03 .09 (32) (33) (31) Requested priority - Begird priority (71) Rauma-Repola Oy, Helsinki, Fl; Pori Factories, PO Box 96, 28101 Pori,

Finland-Finland (FI) (72) Alpo Tuomi, Pori, Finland-Finland (FI) (7 * 0 Ruska & Co Oy (54) Method for precipitating pulp stock or sludge and applying the disc filter method - Förfarande för tjockning av massa eller suspension This invention relates to a method for precipitating a pulp stock or slurry by means of a rotating disc filter partially immersed in a stock or slurry in a basin. rotating filter discs.

The pulps are thickened by means of various filters, e.g. drum or disc filters. The advantage of a disc filter over a drum filter is that it has a large filtration area relative to the total volume it requires. When using a disc filter, a filter surface of about 2-3 times that of a drum filter can be applied to the same floor area. The structure and operation of disc filters have been described e.g. in Finnish patents 5 * 1060 and 56628.

In previously known disc filters, the filtration event is achieved by using suction inside the filter discs. However, normal outside air pressure prevails outside the discs. However, suction filters cannot filter masses with a temperature higher than about 80 ° C at a vacuum of about 3 to 5 m F 2 O. At higher temperatures, the filtrate begins to boil on the vacuum side.

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However, pressure grinders and the like having a low consistency are often at a temperature of about 100 to 105 ° C. Masses with low consistency contain a lot of liquid, so they are difficult to cool. The object of the present invention is to solve the above-mentioned problems. The method according to the invention is characterized in that there is an overpressure outside the filter surface of the discs.

In this case, the filtration can be carried out, for example, in a temperature range of 40 to 110 ° C, more suitably 75 to 105 ° C. The required overpressure is <5 m H 2 O, more preferably 2-3 m H 2 O. In this case, 0.3 to 2% of the initial consistency reaches a residual consistency of 10 to 25%. The method is suitable for use e.g. for precipitating a low-density hot, difficult-to-infiltrate pulp stock, such as, for example, a pressure grit at a vortex cleaner consistency.

In the method according to the invention, the overpressure air can be used not only for filtration but also for removing the filtered mass from the filter surface. The system can be built closed, so that the pressure is easily created. The pressure can be generated, for example, by centrifugal fans connected in series.

The device according to the invention is characterized in that the longitudinal cavity inside the shaft communicates with the source of overpressure and with the disc sector at the point of detachment of each disc.

In the device according to the invention, the disc removal point can be arranged in the direction of rotation of the discs after the uppermost point and not before, as is the case with currently known disc filters. In this case, an area of up to 90 ° from the surface of the discs can be used as the drying area. The effective area is about 340 ° instead of the current about 150 °. E.g.

At 1r / rain speed this increases the drying time by 15 seconds, which increases the droplet density by about 5%

The invention and its details will be described in more detail below with reference to the accompanying schematic drawings, in which Figure 1 shows a cross-section of a disc filter according to the invention, Figure 2 shows the same filter in longitudinal section, Figure 3 shows a cross-section of a disc filter according to another embodiment and Figure 4 shows a longitudinal section .

5 68005

In Figs. The discs 4 formed by the sectors 3 are attached to the shaft 5. Each sector has two water-permeable opposite filter surfaces 6. The closed partitions 16 of the sectors separate the sectors from each other. The shaft 5 is formed by an open tube and a fixed, non-rotating hollow tube 14 runs inside it. A hood 7 is tightly attached above the bath.

Between the discs, on the other side of the filter, there are vertical tubes 8 as drop chutes, into which the filtered mass is collected from the surface of the discs. The lower ends of the vertical pipes 8 merge into a horizontal trough with a screw conveyor 9 · From the discharge screw 9 the pulp exits into a tank or device, e.g. a pulp pump 10, which acts as an overpressure lock on the discharge side.

A tube 12 is connected to the hollow tube 14 toward the point of removal of each disc. The tube 12 is slidably connected to the rotating disc by a sealing shoe 13. The blowing side of the fan 15 is connected to the inside of the pipe 14 and the suction side to the space inside the shaft 5.

When the filter is operating, its discs rotate in the direction indicated by arrow A in Figure 1. The mass to be precipitated is led to the tank through the distribution pipe 2 (arrow B). As the disc sector rises from the pulp stock (right side of disc 4 in Figure 1), the mass remains on the surface of the sectors and the filtrate is pressed inside the sectors by overpressure. From there, the filtrate flows into an open tube 5, from which it is led out (arrows C and C'l. Air also flows from the outside of the wafers into the wafers (arrows C ').

The fan 15 blows air inside the pipe 14 (arrow D). From here, the overpressure air passes through the tubes 12 inside each sector in the disc release shift (arrows D'1. The overpressure air escapes through the perforated surface of the sectors outside the sectors while 1Q The pump 1Q acts as an overpressure lock on the discharge side.

The air coming from the fan thus enters the hood through the sectors in the removal shift, creating the necessary overpressure there, removing the mass mat and cleaning the wire at the same time. Air is sucked into the fan from inside the shaft tube 5 (arrow F), thus creating a closed air circulation.

Claims (2)

68005 Figures 3 and 4 show another embodiment of the invention. The inner part of the shaft 5 is here provided with longitudinal compartment walls 17 known per se, which rotate with the shaft. The shaft compartments thus formed are associated with the sector at that disc of each disc. At the compartment 19 corresponding to the disc sector in the release shift, at the other end of the filter there is a sealing shoe 18 which allows the shaft 5 to rotate with its compartments. The blowing side of the fan 15 is connected by means of a sealing shoe 18 to the shaft compartment 19 at the disc sector in each case of removal. In other respects, the structure and operation of the filter are as shown in Figures 1 and 2. A method of precipitating soil or sludge by means of a rotating disc filter partially immersed in a stock or sludge in a basin, wherein the filter housing has an overpressure outside the disc filter surface, characterized in that air used to pressurize the space outside the filter surface is blown into the housing through each disc removal sector. detach the pulp web from the discs. A disc filter for applying the method according to claim 1, wherein the filter has a basin (1), a housing (7) above the basin and filter basin (4) rotating in the basin, formed by sectors (3) and arranged on the shaft (5), wherein inside the shaft (5) The longitudinal cavity (1A or 19) is connected to the overpressure source (15) and to the disc sector (3) at the disc removal point, characterized in that the disc removal point (3) is located in the direction of disc rotation (A) after the uppermost point.