SE518251C2 - Apparatus for washing and dewatering a fiber suspension - Google Patents

Abstract

A device for dewatering and washing a fibrous suspension, comprising two rolls (1), which together form a nip, in which a seal (8) is located. A head chamber (2) for the suspension is placed symmetrically directly beneath the nip, and a common washing chamber (10) for the supply of washing liquid to at least on first washing zone (25) is placed symmetrically directly above the nip. The shell surface of the rolls (1) is divided into compartments (3) with screen bottoms for receiving the suspension from the head chamber (2) and for draining filtrate into each roll in the washing zone (25). The washing zone (25) is defined by each roll (1) and a washing flap (12), which extends along the shell surface of each rool (1).

Description

20 25 - = 30 518 251 šïï:: š .- :; åi!: Š = * the system is wear on valve seats and high power consumption.

In addition, phase shifts and mixing of filtrates remain in different stages due to filtrate lines from the valve to the shell around the drum becoming long.

The present invention provides a solution to the above problems in that the device is formed with two mutually rotating compartmentalized rollers which between them form a nip with a symmetrical inlet chamber for the fiber suspension and a washing chamber located above the nip. The more detailed features of the invention appear from the claims.

According to the present invention, two rotating rollers are used, which can have a substantially smaller diameter with maintained capacity compared to the devices as above, and thus the dimensions of the valve system can also be limited.

Another object is to shorten the filtrate lines from the valve sector of the second washing stage to the axial connection of the first stage, which reduces the risk of phase shift and mixing of the washing stages.

A further object is to obtain a more efficient device for dewatering and washing for better formation of the fiber suspension, which entails an increase in capacity or possibilities to construct a smaller device with the same capacity as a larger device according to the prior art.

According to one aspect, the inlet for the fiber suspension consists of an inlet box which is equipped with seals which delimit an inlet chamber towards a removal zone. The device is easily adjustable in the vertical direction to apply the seals to the rollers. The headbox is demountable for changing seals.

According to another aspect, the inlet chamber towards the washing zone is sealed by an adjustable wedge-shaped seal which divides the fiber suspension and the washing liquid into two flows. The seal is placed between the rollers and forms part of a common washing chamber where washing liquid is supplied axially at the end valves of the rollers.

Washing flaps in a first washing step end with a) lO 15 20 25 anwa »n-w, 35 518 2351 .... .. o | u u n o a n. longitudinal seal enclosed by a pre-throttled wash chamber for a second wash step, the overpressure of which pressurizes the seal.

According to a further aspect, a transport screw is placed between and under the rollers, the trough sweep with ends being used as a bracket for vertically adjustable arms and where seals are connected as a seal between a second washing step and the removal zone.

In the following, the invention will be described in more detail in connection with the figure which shows a cross section of a device according to the invention.

The device shown comprises two opposite rollers 1 whose circumferential surface is divided into compartments 3 which are delimited by radial wall elements which extend in the axial direction of the rollers.

The compartments 3 are designed with screen bottoms for drawing liquid into each roller. The rollers 1 together form a pinch. Under the nip, an inlet chamber 2 is symmetrically located.

The inlet chamber is limited by an inlet drawer 5 with inlet 4 for the fiber suspension and the compartments 3 on the casing surfaces of the rollers.

The inlet chamber 2 is pressurized and sealed against the rollers in that the headbox 5 is vertically movable and has two inclined seals 6 which abut against the rollers. The inlet 4 of the headbox is axially located between the opposite rollers. For cleaning the compartments 3 in front of the inlet chamber 2, spray pipes 7 are placed on the vertical ends of the inlet drawer 5. In the nip between the rollers 1 a wedge-shaped seal 8 is arranged which is regulated vertically by actuators 9. Above the nip between the rollers is a common washing chamber 10 placed with axial connection 11 for supply of washing liquid. The common washing chamber 10 communicates with a first washing zone 25 on each roller 1. » The sealing zones 25 are delimited by the two rollers 1 and washing flaps 12 which extend along the mantle surface of each roller so that the height of the washing zones gradually decreases. The wash flaps 12 end with seals 13 against a second wash chamber 14 on each roller.

These second washing chambers 14 are connected to second inlets 15 and communicate with a second washing zone 26 on each roller 1. These second washing zones 26 are bounded by each roller 1 and other 1 »., | W Ü 20 25 30 35 518 2.51 4 «- | n .u wash flaps 16 extending along the mantle surfaces of the rollers so that the height of the wash zones gradually decreases. The other washing zones 26 end with seals 19. After these seals 19, in the circumferential direction, there is a removal zone 28 where the dewatered and washed fiber suspension is removed from the compartment 3 of the rollers to a trough 17 located below in which a transport screw 21 is arranged. The seals 19 are suitably arranged on arms 18 which are vertically adjustable in guides 20 on the trough 17 for adjusting and adjusting the seals.

The wash flaps 12, 16 may be provided with perforated cover plates 27 which abut against the compartments of the rollers for distributing the washing liquid into the compartments for displacing the liquid in the fiber suspension through the screen bottoms of the compartments into the rollers.

The rollers 1 should have a diameter of 1-3 meters, preferably 1.5-2.5 meters.

The inlet chamber 2 constitutes a thickening and forming zone for the incoming fiber suspension which at the inlet normally has a concentration of 3-8%. The inlet chamber is sealed against the common washing chamber 10 by the wedge-shaped seal 8, which distributes the fiber suspension in two equal parts in the compartments 3 on the respective roller. The pulp concentration in compartments 3 is then suitably 12-16%. The seal 8 also forms part of the common washing chamber 10 from which the washing liquid is distributed in two equal flows in the first washing zones 25. The washing liquid is supplied axially to the washing chamber 10 whose connection 11 is located at the end valves of the rollers 1.

The wash flaps 12 in the first wash zones 25 should extend along about one third or more of the circumference of the rollers.

The wash flaps 16 in the other wash zones 26 should likewise extend along one third or more of the circumference of the rollers.

Together, the wash flaps 12 and 16 can surround 250-300 ° of each roller.

The other washing chambers 14 are arranged to partly distribute the washing liquid and partly to pressurize the longitudinal seals 13, which are arranged at the end of the washing flaps 12., 10 15 20 518 - »: HE _2" ':' 5 1. 3 '' '.LI the removal zone 28 after the seals 19, the treated fiber suspension is removed from the compartments 3 and removed by the transport screw 21 to a subsequent treatment step.

The compartments 3 are then flushed by means of the spray pipes 7.

According to an alternative embodiment, the device can be designed with a single washing zone on each roller. This washing zone then extends from the common washing chamber 10 to the removal zone 28.

The washing principle of the device according to the invention is to direct washing liquid to the washing zones 25, 26 where the washing liquid is distributed over the fiber suspension in the compartments of the rollers 3. When the device is designed for two washing steps, the filtrate is pumped by means of a pump 30 from the second washing zone 26 directly to the axial connection 11 to the common washing chamber 10 and to the first washing zone 25. The filtrate from the first washing zone is taken out through the end valves of the rollers and passed to somewhere else in the process.

It will be clear to a person skilled in the art in this field that the various forms of application of the invention are not limited to the described embodiments but that they can be varied within the scope of the claims with regard to the description and figure.

Claims (8)

v |> ~ u .nmn 10 U 20 25 v a n - uu 518 2561. Patentkrav Device for dewatering and washing a fiber suspension comprising an inlet chamber (2) for the suspension, rotating rollers whose outer surface is divided into compartments (3) for receiving the suspension from the inlet chamber (2), washing liquid, a washing zone with a washing chamber for supplying the compartments being formed with screen bottoms for drawing filtrate into each roller and a removal zone (28) for the treated fiber suspension, characterized in that two rollers (1) together form a nip in which a seal (8) is arranged, that the inlet chamber (2) is symmetrically located directly below the nip, that a common washing chamber (10) is symmetrically located directly above the nip, said washing chamber (10) communicating with at least a first washing zone (25) on each roller (1), which washing zones are delimited by the two rollers and wash flaps (12) extending along the mantle surface of each roller (1). Device according to Claim 1, characterized in that the seal (8) in the nip between the rollers (1) is symmetrically wedge-shaped and can be adjusted by means of actuators (9). Device according to one of the preceding claims, characterized in that a second washing chamber (14) and a second washing zone (26) with a washing flap (16) are arranged at each roller (1) directly after the first washing zone (25), wherein a pressurized seal (13) delimits the two washing zones (25, 26). Device according to claim 3, characterized in that the second washing chamber (14) is designed partly for distributing washing liquid to the second washing zone (26) and partly for pressurizing the seal (13) between the washing zones (25, 26). Device according to one of Claims 3 to 4, characterized in that a pump (30) is arranged to pump filtrate from the other washing zones (26) directly to an axial connection (11) for supplying washing liquid to the common washing chamber (10). ). (JN Io »; ~» ».., t) 10 518 251 7 Device according to one of the preceding claims, characterized in that the removal zone (28) for the treated fiber suspension is arranged after the washing zones (25, 26) and delimited from them by means of seals (19). Device according to claim 6, characterized in that the seals (19) are adjustably arranged on a trough (17) for receiving the removed fiber suspension under the rollers (1). Device according to any one of the preceding claims, characterized in that the washing flaps (12, 16) are provided with perforated cover plates (27) which abut against the compartments (3) of the rollers (1) for distributing the washing liquid into the compartments.