NZ211324A

NZ211324A - Processing particle suspensions using screens and rotating refiners

Info

Publication number: NZ211324A
Application number: NZ211324A
Authority: NZ
Inventors: Ruvo A R De; E H Eriksson
Original assignee: Sunds Defibrator
Priority date: 1984-04-03
Filing date: 1985-03-06
Publication date: 1986-07-11
Also published as: SE8401846L; FI863998A; FI863998A0; WO1985004433A1; SE8401846D0; SE441758B; NO854832L; JPS61501715A; EP0207937A1; AU3934985A

Description

21132' Complete Specification Filed: <P.\ Close: &Q. 7&. I .. £)Q?£.7ilLP. v.

SQ ?£-?. JQ^.m .. JO.^t (AV./30 .QRMS/OG U.I JUL 1986 Publication Date: .. P.O. Journal, No: .. .4?.?$ PATENTS FORM NO. 5 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION "METHOD AND APPARATUS FOR PROCESSING MATERIAL SUSPENSIONS" i, WE SUNDS DEFIBRATOR AKTIEBOLAG a Swedish Body Corporate of S-851 94 Sundsvall Sweden hereby declare the invention, for which-f/we pray that a patent may be granted to me/us, and the method by which it is to be performed, to be particularly described in and by the following statement: - (followed by page I A.) 2 f 132^ Method and apparatus for processing material suspensions This invention relates to a method and an apparatus for continuously processing material suspensions comprising particles of different size, for example lignocellulose--containing fibrous material.

By separating coarse particles from a material suspension by means of a screen device, the suspension can be divided into an accept portion and a reject portion. These portions can thereafter be processed separately in different ways. It cannot be avoided, however, that a substantial amount of small particles follow along with the reject. For solving this problem, additional screening steps for the reject are required for recovering these small particles. For being able to recover also the reject, special equipment is required.

According to the present invention, the material suspension is separated by a screen device into an accept portion and a reject portion, and the reject portion is passed directly through a refiner for reducing the size of the particles. The reject is thereafter returned to the screen device for repeated separation. This combination yields the unique effect that the material suspension supplied is converted to 100% accept, i.e. a suspension without overdimension particles. Separated coarse particles passing through the refiner and returned to the screen device, thus, circulate in one or several sequences until the dimension of the particles permit their passage through the screen device.

The refiner is provided with two refiner members, which are rotatable relative to each other and define a diverging gap. Owing to the fact that the gap is designed with an inlet of a smaller diameter and an outlet of a greater diameter, a vacuum is created at the inlet. As a result thereof, the suspension (reject) enriched on 2 2 f -f 3 2 greater particles on the inlet side of the screen device is sucked into and passed through the gap. The fluidiz-ation arising at the entrance into the gap can contribute to rendering the refining more efficient. The flow can be adjusted by special means, for example valves and means for adjusting the gap.

According to the invention, different types of screen devices can be utilized, for example rotary or stationary screening cylinders. Other types of screens (vibrating, pulsating ones, etc,) can also be imagined.

The characterizing features of the invention become apparent from the attached claims.

The invention is described in greater detail in the following, with reference to the accompanying drawings, which illustrate two embodiments of the invention.

The embodiments shown comprise a refiner consisting of a rotary conic refiner member 10, the refining surface of which is provided with grooves 12 and bars 14, the longitudinal direction of which substantially coincide with the generatrices of the conic refiner surface.

The rotary refiner member 10 co-operates with a stationary refiner member 20, the surface of which is designed similar to the surface of the rotary refiner member 10. Between the refiner members 10,20 a gap 22 is formed,which can be adjusted according to the particle size desired at the discharge zone 24 of the refiner by moving the rotary refiner member 10 in axial direction. The said refiner member is supported on a shaft 11, which is mounted in an axially movable bearing housing 13 and driven via an axially adjustable coupling Ik by a motor, the shaft 15 of which is connected to said coupling. The axially movable bearing housing 13 is adjusted to and retained in desired position by means of a piston 16, which is mounted on the bearing housing and enclosed in a cylinder housing 17, which is rigidly secured in the stationary casing 30 of the refiner. 3 211324 The distance between the rotary and the stationary refiner member 10,2.0 is adjusted in known manner, see for ex- ' Specification.No.^3212721, ample U.S. Patent/ by means of a hydraulic servo valve 40, which is actuated by a sensing arm 44 mounted on the axially movable bearing housing, which arm carries an adjusting screw 46 through a threaded connection 45, and by which the bearing housing can be adjusted to desired position. The adjusted position is thereafter maintained constant automatically, in that the sensing arm 44 actuates the servo valve 40, which adjusts and controls the hydraulic pressure in the cylinder chambers 18 and 19.

The embodiment shown in Fig. 1 comprises a screen device ^ x.v. . • ~ «• - , . ■ „ ^ ■ Specification No., 4346 of the kind disclosed m U.S. Patent / . The screen device consists .of a stationary screening cylinder 50, which is rigidly connected in the pressurized casing 30. The material suspension is intended to be supplied through an inlet 64 via an adjusting valve 65. The screening cylinder 50 is provided with slits or perforations of the size permitting the passage for accepted particle size, but which prevents the passage of greater particles. The screening cylinder 50 is concentrically enclosed by a rotary outer cylinder 60, which is provided with relatively great feed openings, through which the material suspension supplied at overpressure and intensely agitated can pass without particle separation. The material suspension supplied is moved by the supply pressure toward the particle separating screening cylinder 50, where particles with overdimensions are prevented from passing through the apertures of the screening cylinder. Particles of oversize accumulated on the screening cylinder 50 are removed from the cylinder surface by means of a series of radial tubular members 66, which are attached on the rotary cylinder 60 and upon rotation of the cylinder generate a vacuum, by which the fibre particles deposited are removed from the screening cylinder and passed to the space 63 outside the rotary cylinder 60. In said £ w space 63 the suspension is enriched with oversize p$}t- -2 MAY 1986 211324 n icles, which were not permitted to pass through the screening cylinder 50. By means of the axial flow of the unprocessed suspension supplied in the direction to the space between the rotary cylinder 60 and an enclosing cylinder 67, the suspension enriched on great particles is moved in axial direction toward the gap 22. The accept is conducted away from the interior of the screening cylinder 50 via an outlet 68 with a valve 69.

The embodiment shown in Pig. 2 comprises a refiner of the same kind as shown in Fig. 1 in combination with a different type of screen " riewice. This screen . device is of the . Specification No. 3586172 kind disclosed m U.S. Patent / and consists here of a stationary screening cylinder 70, which is rigidly connected in the pressurized casing 30. An inlet 71 with adjusting valve 72 is provided for the material suspension. The screening cylinder 70 is provided with perforations of a size permitting the passage of accepted particle size. The screening cylinder 70 is located spaced from the casing 30 so as to define an accept chamber 73 on the outside, from which the accept can be conducted away through an outlet 74 with a valve 75. Inside of the screening cylinder 70 and concentrically therewith a rotary pulsation cylinder 76 is located, which is provided with surface deformations 77 in the form of depressions and/or projections. The rotation of the pulsation cylinder 76, preferably together with the rotary refiner device 10, generates a flow along the screening cylinder 70 which is favourable for particle separation, and at the same time the perforations are kept clean. The particles unable to pass through the perforations of the screening cylinder 70 continue past the screening surface and are sucked into the gap 22 as described above.

At both embodiments an. intense fluidization of the suspension is effected by the rotary members, the inder 60 and, respectively, the pulsation cyli which are attached on the rotary refiner member implies that the reject enters the gap 22 in fluidized state,and thereby the efficiency of the refining- is improved. The strong fluidization further renders it possible that the refining is carried out at a concentration at optimum for refining.

At both embodiments a return conduit 80 is connected to the discharge zone 24 of the refiner This conduit 80 is coupled to the inlet side of the refiner devices 50,70. A control valve 81 is provided in the conduit 80 for controlling the recycling. The apparatus according to the invention, thus, acts as a screening or separation means without external reject flow. The invention renders possible substantial savings in respect of both building and machine equipment for the recovery and processing of the rejected portion of the material suspension. The apparatus according to the invention, thus,delivers 100# accept, i.e. accepted particle size. The processed fibre suspension is discharged through the outlet 68 and, respectively, 74 as 100# accept. The outgoing flow is adjusted by valves 69 and, respectively, 75 by means of a control device 84, which is connected to a pressure sensing device 85, by means of which a constant hydraulic pressure is maintained in the casing 30.

The difference in pressure required for the recirculation through the conduit 80 is generated by means of the refiner as: described above . The circulation flow can be controlled by means of the valve 8l. The adjustment to be made, of course, depends on the quality of the suspension supplied and on the quality desired of the outgoing suspension.

The invention, of course, is not restricted to the embodiments described above, but can be varied within the scope of the invention idea. 211324 WHAT -WWE CLAIM IS:. 6

Claims

Claimo-

1. A method of continuously processing material suspensions containing particles of different size, which particles are separated into accept and, respectively, reject by means of a screen device permitting the passage only of particles below a definite size (accept), characterized in that particles above said size (reject) are conducted away and processed directly during the passage outward through a gap between two refiner members rotating relative to each other for reducing the size of the particles, which thereafter are returned to the screen device for repeated separation so that the material suspension supplied is converted in its entirety to an outgoing material suspension containing only particles below the definite size (accept).

2. A method as defined in claim 1, characterized in that the difference in pressure required for the return is produced by the increase in pressure generated over the gap.

3. A method as defined in claim 1 or 2, characterized in that the recirculation flow is controlled in respect of the desired quality of the accept. k.

A method as defined in any one of the preceding claims, characterized in that the reject is supplied into the gap in fluidized state.

5. An apparatus for continuously processing material suspensions containing particles of different size, comprising a pressurized casing (-5HH with an inlet (6-H ■, 71-) for the suspension, a screen device (50?7<->) located in the casing and permitting the passage of particles below a definite size (accept) and preventing the passage of particles above said size (reject), and an outlet from the casing (■&&) for the accept, characterized i n that the casing (3#5 also comprises two refine 7 211324 members (10?20), which are rotatable relative to each other and between themselves define a diverging gap (22-)-, the inner portion of which is connected directly to the inlet end of the screen device (50,70") for receiving the reject, and the outer portion of the gap (2tJ opens into a discharge zone &nd-"a return conduit C&0") connects the discharge zone (^^T to the inlet portion of the screen device (5-0,70) *;

6. An apparatus as defined in claim 5, c haract -erized in that an inner refiner member (ioT is rotatable and an outer refiner member (20^ is stationary.;

7. An apparatus as defined in claim 6, characterized in that a rotary member (6thr¥£-) located in connection to the screen device (50,70) is attached on the rotatable refiner member (1&) •;

8. An apparatus as defined in claim 6 or 7, characterized in that the rotatable refiner member (^) is axially adjustable for controlling the flow through the gap (2^J and the processing degree of the reject.;

9. An apparatus as defined in any one of the claims 5-8,characterized in that a valve (8^5 is located in the return conduit (8j&j for controlling the recirculation flow.;

10. An apparatus as defined in any one of the claims 5-9, characterized in that it comprises a pressure sensing device (8pf in the casing (3and a control device connected to said sensing device (85* for adjusting an outlet valve (69,75) for the accept. n UN ¥ { -2 MAY 1986 -8- 21132

11. A method of continuously processing material suspensions comprising particles of different size, as hereinbefore described with reference to any one of the embodiments shown in the accompanying drawings.

12. An apparatus for continuously processing material suspensions comprising particles of different size, arranged, constructed and adapted to operate substantially as hereinbefore described with reference to any one of the embodiments shown in the accompanying drawings.