US3682444A

US3682444A - Dewaterers for fiber pulp suspensions

Info

Publication number: US3682444A
Application number: US51419A
Authority: US
Inventors: Rolf Bertil Reinhall
Original assignee: Defibrator AB
Current assignee: Valmet AB
Priority date: 1966-10-20
Filing date: 1970-07-01
Publication date: 1972-08-08
Anticipated expiration: 1989-08-08
Also published as: GB1201635A

Abstract

A pressure actuated dewatering device for a fiber pulp suspension having an elongated container with an inlet and an outlet for the suspension and a motor driven stirrer. The container wall includes separate sets of perforations each set communicating with a compartment located externally of the container and each compartment communicating through one-way valve with a common discharge conduit having a valve-controlled outlet for the drainage of water pressed from the suspension. A motor driven conveyor may be provided to carry the suspension having a higher concentration of fiber pulp away from the outlet. The driving motor of either the stirrer or the optional conveyor actuates a power control relay which emits pulses to a motor actuating the valve in the discharge conduit to control the pressure in the compartment thus regulating the amount of water removed from the suspension and consequently the concentration of fiber pulp in suspension as it passes through the outlet.

Description

United States Patent Reinhall 1151 3,682,444 1 Aug. 8, 1972 [54] DEWATERERS FOR FIBER PULP SUSPENSIONS [72] Inventor: Rolf Berti] Reinhall, Lidingo,

Sweden [73] Assignee: Detibrator Aktiebolag, Stockholm,

Sweden [22] Filed: July 1, 1970 [21] Appl. No.: 51,419

Related US. Application Data [63] Continuation-impart of Ser. No. 675,183, Oct.

13, l967, abandoned.

52 u.s.c1. ..259/6 51 1111. C1. morn/20 58 Field ofSearch....259/9, 10,154, 149,169, 170,

[56] References Cited I UNITED STATES PATENTS 2,452,142 10/1948 Pecker ..137/92 2,498,876 2/ 1950 Bowen ..l37/92 2,815,763 12/1957 Fanselow ..l37/92 2,880,654 4/1959 Henry ..137/92 Primary Examiner-Robert W. Jenkins Attorney-Munson & Fiddler ABSTRACT A pressure actuated dewatering device for a fiber pulp suspension having an elongated container with an inlet and an outlet for the suspension and a motor driven stirrer. The container wall includes separate sets of perforations each set communicating with a compartment located externally of the container and each compartment communicating through one-way valve with a common discharge conduit having a valve-controlled outlet for the drainage of water pressed from the suspension. A motor driven conveyor may be provided to carry the suspension having a higher concentration of fiber pulp away from the outlet. The driving motor of either the stirrer or the optional conveyor actuates a power control relay which emits pulses to a motor actuating the valve in the discharge conduit to control the pressure in the compartment thus regulating the amount of water removed from the suspension and consequently the concentration of fiber pulp in suspension as it passes through the outlet.

10 Claims, 2 Drawing Figures PAYENIEmus 8 m2 ow mm 9 g @m 4 mm mm 4. ww 8 cm N1 6 i 0000. o... mm mm g a 4m n S W Om m 0.1.0000 m mm w u u an. unook fi m 0..

L mM NH E 5 n L 0 TUE 5 6 X film/50m ATTORNEY DEWATERERS FOR FIBER PULP SUSPENSIONS suspensions and more particularly to pressure actuated dewatering devices.

Briefly, the dewaterer of the present invention is in the form of a relatively long container provided with inlet and outlet means for the suspension and a stirrer driven by an electric motor. Separate sets of perforations are provided in the wall of the container, each set of perforations communicating with a compartment located externally of the container for drainage of water pressed out of the fiber pulp suspension in the container. The compartments communicate through separate one-way valves with a common discharge conduit provided with a control valve. The pressure in the compartments is regulated but maintained lower than in the container to control drainage of water pressed out of the fiber pulp suspensions through the perforations. The suspension is preferably introduced under superatmospheric pressure into the container such as by means of a pump.

The dewaterer optionally may be provided with a power driven conveyor for conveying the suspension having a higher concentration away from the outlet for further processing as for example in a grinding apparatus.

In one embodiment of the present invention the motor driving the stirrer operates a power control relay which emits electrical impulses to a motor actuating the valve in the discharge conduit so that the pressure in the compartments is adjusted to a value corresponding to the predetermined concentration of fiber pulp in the suspension in the container. The power required to operate the stirrer as sensed by the power control relay will be proportional to the concentration of solid fiber pulp in the suspension. V

In another embodiment, the motor driving the optional conveyor for conveying the suspension away from the outlet operates a power control relay for transmitting electrical impulses to the motor actuatingthe discharge conduit valve. The power required to operate the conveyor is proportional to the concentration of solid fiber pulp in the suspension carried by the conveyor.

The dewatering device according to the present invention permits the rapid conversion of a pumpable pulp suspension to a highly concentrated pulp mass suitable for further treatment such as in a grinding apparatus.

One main object of the invention is to provide a dewaterer which is capable of maintaining the concentration of the fiber pulp at a predetermined level with only small deviations. Thus, the dewaterer must be capable of responding rapidly to every such deviation to maintain the fiber pulp concentration constant.

Another object of the invention is to provide a de- 1 waterer having a large capacity relative to its overall dimensions.

Further objects and advantages of the invention will become apparent from the following description considered in connection with the accompanying drawings which form part of this specification wherein:

FIG. 1 shows diagrammatically and in vertical section a pressure-operated dewaterer combined with a grinding apparatus; and

FIG. 2 shows diagrammatically a fragmentary view of a modification in the dewaterer of FIG. 1.

Referring to FIG. 1, reference numeral 10 generally denotes a pressure-operated dewaterer and 12 a grinding apparatus such as a refiner of the disc-type. The dewaterer comprises an elongated vertically extending cylindrical container 14 which at its bottom or outlet connects with an inlet 16 of the grinding apparatus 12. The cylindrical container 14 is provided with separate sets of perforations in the wall thereof, the separate sets being spaced from each other along the length of the cylindrical container. A further cylindrical wall 28 is located concentrically and externally of the container 14 and a series of annular partitions 62 extend between the interior of cylindrical wall 28 and the exterior of the cylinder 14 to define a plurality of annular compartments 64, each compartment being associated with a different set of perforations 24. Each of the compartments 64 communicates through a pipe 66 having a one-way valve 68 with a common discharge conduit 30 having a control valve 32 which is adapted to be actuated by a motor 34 to control adjustment of the valve opening.

A stirrer 36 comprising a shaft 38 having a plurality of inclined blades 40 is located within the cylindrical container 14. The free ends of the inclined blades 40 contact the internal surface of the container wall and operate as scraping members. The plurality of blades 40 extending over substantially the total length of the container 14 serve to rake the perforated wall of the container. The shaft 38 is driven by a motor 42 which also actuates a power control relay 44.

A liquid suspension of preferably vegetable or lignocellulose containing fiber material which has been subjected to partial disintegration through digestion, defibration or grinding is pumped from a container 46 by pump 48 through a conduit 50 and valve 52 into the dewaterer device 10. The suspension as fed into the dewaterer has a very low pulp concentration and therefore may be easily pumped into the dewaterer.

In the dewaterer 10, part of the liquid is driven off through the perforations 24 into the compartments 64, the pressure in the compartments being lower than that in the container 14. Pulp material collected on the interior wall of the cylindrical container is scraped off by the rotating blades 40 and is conveyed downwardly by the continuous stirring and scraping action of the blades 40. Thedewatered pulp passes from the outlet of the dewaterer 10 into the inlet 16 of the grinding apparatus 12 where the pulp is conveyed towards the

grinding discs

18 and 20 by screw conveyor 54 driven by motor 56. The concentrated pulp suspension is fed between the

grinding discs

18 and 20 where a further disintegration of the pulp into individual fibers and possibly also fibrillation is effected. Superatmospheric pressure is maintained in the grinding apparatus 12 as in the dewaterer 10. The ground pulp is discharged through conduit 58 having a valve 60 for further treatment which is not described here as it falls outside the scope of the present invention.

The power control relay 44 transmits signals over a conductor 58 which serve to actuate the motor 34 to 3 control the opening and closing of valve 32 in response to the concentration of pulp in container 14. If the concentration of pulp at any moment exceeds the predetermined desired level the stirrer 36 will meet increased resistance against rotation. The power required to operate motor 42 will be increased because of the increased resistance against rotation in the container, and this increase in required power will be sensed by the control relay 44 which in turn will transmit a signal to the motor 34 causing the valve 32 to be moved towards the closed position. This results in a pressure rise in the discharge conduit 30 and the compartments 64 whereby the pressure drop between the container 14 and the compartments 64 is reduced, thereby reducing the rate of dewatering of i the suspension. Consequently, more water will remain in the container 14 and the concentration of the pulp therein will be reduced until the predetermined level of concentration has been reached again. Conversely, if the dilution of the pulp suspension in the container 14 becomes too great, the resistance against rotation of the stirrer 34 is reduced causing the control relay 44 to transmit signals opening the valve 32 so that the rate of dewatering mayv be increased.

FIG. 2 shows an alternative form of the present invention wherein those parts of the apparatus common with FIG. 1 have been given the same numerical designations. Here, however, a power control relay 44' similar to the power control relay 44 shown in FIG. 1 is actuated by the motor 56 which operates conveyor 54. It will be readily appreciated that the conveyor 54 is subjected to a resistance from the pulp suspension proportional to the concentration of pulp in the suspension as it is being conveyed. Thus, if the concentration of pulp is above a predetermined level, the increased power required in motor 56 required as a result of the increased resistance is detected by the relay 44' which in turn transmits signals through conductor 62 to the motor 34 moving valve 32 towards the closed position to reduce the rate of dewatering and thereby reduce the concentration of pulp in the dewatered suspension as it is conveyed by conveyor 54. Conversely, if the pulp concentration in the suspension conveyed by conveyor 54 falls below a predetermined value, the power control relay 44 will cause the valve 32 to be opened increasing the dewatering rate whereby the pulp concentration in the dewatered suspension is maintained at a predetermined value.

I claim: 7

1. A dewaterer for fiber pulp suspensions comprising a container having inlet means and outlet means for feeding said pulp suspension therethrough, discharge conduit means for said container for discharging of water from said suspension, valve means in said discharge conduit means for controlling the rate of liquid discharge, means for determining the proportion of pulp in said suspension in said container and for regulating said valve means in accordance with said determination, whereby the pressure in said discharge conduit means is adjusted to maintain a predetermined pulp concentration in said suspension in said container, said discharge conduit means comprising a conduit containing said valve means, a plurality of perforations along the length of a wall of said container and passage means connecting said perforations with said conduit.

2. A dewaterer as claimed in claim 1 wherein said passage means comprises a one-way valve means to prevent flow towards said container.

3. A dewaterer as claimed in claim 2 wherein said perforations are divided into separate sets spaced along the length of the container and said passage means comprises a plurality of compartments, each compartment communicating with one set of said perforations and said conduit, a one-way valve being positioned between each of said compartments and said conduit.

4. A dewaterer as claimed in claim 1 wherein said means for determining the proportion of pulp in said suspension in said container and for regulating said valve means comprises a rotatable stirrer in said container and means for detecting the power required to rotate said stirrer which is proportional to the relative proportion of pulp is said suspension.

5. A dewaterer as claimed in claim 4 further comprising electric motor means for driving said stirrer and a power control relay actuated by said motor for controlling said valve means.

6. A dewaterer as claimed in claim 5 wherein said stirrer comprises a shaft and a plurality of inclined blades attached to said shaft the free ends of said blades substantially contacting the internal surface of the container wall to scrape pulp deposited on said wall.

7. A dewaterer for fiber pulp suspensions comprising a container having inlet means and outlet means for feeding said pulp suspension therethrough, discharge conduit means for said container for discharging of water from said suspension, valve means in said discharge conduit means for controlling the rate of liquid discharge, means for determining the proportion of pulp in said suspension in said container and for regulating said valve means in accordance with said determination, whereby the pressure in said discharge conduit means is adjusted to maintain a predetermined pulp concentration in said suspension in said container, said means for determining the proportion of pulp in said suspension in said container and for regulating said valve means comprising conveyor means for conveying the dewatered suspension away from said outlet means of the container and means for detecting the power required to drive said conveyor which is proportional to the relative proportion in the said dewatered suspen- $1011.

8. A dewaterer as claimed in claim 7 further comprising electric motor means for driving said conveyor and a power control relay actuated by said motor for controlling said valve means.

9. A dewaterer for fiber pulp suspensions comprising a container having inlet means and outlet means for feeding said pulp suspension therethrough, discharge conduit means for said container for discharging of water from said suspension, valve means in said discharge conduit means for controlling the rate of liquid discharge, means for determining the proportion of pulp in said suspension in said container and for regulating said valve means inaccordance with said determination, whereby the pressure in said discharge conduit means is adjusted to maintain a predetermined pulp concentration in said suspension in said container,

a refiner for said pulp and feeding means for delivering said dewatered suspension from the outlet means of said container to said refiner.

regulating said valve means in accordance with said determination, whereby the pressure in said discharge conduit means is adjusted to maintain a predetermined pulp concentration in said suspension in said container, said outlet means includes means for refining said pulp and feed means for delivering said dewatered suspension to said refining means.

Claims

7. A dewaterer for fiber pulp suspensions comprising a container having inlet means and outlet means for feeding said pulp suspension therethrough, discharge conduit means for said container for discharging of water from said suspension, valve means in said discharge conduit means for controlling the rate of liquid discharge, means for determining the proportion of pulp in said suspension in said container and for regulating said valve means in accordance with said determination, whereby the pressure in said discharge conduit means is adjusted to maintain a predetermined pulp concentration in said suspension in said container, said means for determining the proportion of pulp in said suspension in said container and for regulating said valve means comprising conveyor means for conveying the dewatered suspension away from said outlet means of the container and means for detecting the power required to drive said conveyor which is proportional to the relative proportion in the said dewatered suspension.

9. A dewaterer for fiber pulp suspensions comprising a container having inlet means and outlet means for feeding said pulp suspension therethrough, discharge conduit means for said container for discharging of water from said suspension, valve means in said discharge conduit means for controlling the rate of liquid discharge, means for determining the proportion of pulp in said suspension in said container and for regulating said valve means in accordance with said determination, whereby the pressure in said discharge conduit means is adjusted to maintain a predetermined pulp concentration in said suspension in said container, a refiner for said pulp and feeding means for delivering said dewatered suspension from the outlet means of said container to said refiner.

10. A dewaterer for fiber pulp suspensions comprising a container having inlet means and outlet means for feeding said pulp suspension therethrough, discharge conduit means for said container for discharging of water from said suspension, valve means in said discharge conduit means for controlling the rate of liquid discharge, means for determining the proportion of pulp in said suspension in said container and for regulating said valve means in accordance with said determination, whereby the pressure in said discharge conduit means is adjusted to maintain a predetermined pulp concentration in said suspension in said container, said outlet means includes means for refining said pulp and feed means for delivering said dewatered suspension to said refining means.