GB2130759A

GB2130759A - Apparatus for fractionating a fibrous suspension

Info

Publication number: GB2130759A
Application number: GB08329220A
Authority: GB
Inventors: Walter Musselmann; Rudolf Gehlig
Original assignee: JM Voith GmbH
Current assignee: JM Voith GmbH
Priority date: 1982-11-12
Filing date: 1983-11-09
Publication date: 1984-06-06
Also published as: ATA354483A; CH661545A5; GB2130759B; GB8329220D0; DE3241876A1; FR2536097A1; AT385294B; FR2536097B1; DE3241876C2

Abstract

Connected into the long fibre line which leaves fractionating apparatus in which a fibrous suspension e.g. paper-pulp is separated into a fraction of long fibres and of short fibres there is pulp consistency monitoring equipment 4 which controls a regulator 3 depending on which a throttle 5 in the long fibre line is operated proportionally with the pulp consistency measured to obviate blocking of the fractionating apparatus. A throttle 6 in the short fibre line may in addition be controlled to close as the throttle 5 opens Constant consistency at the net to apparatus 1 is ensured by control equipment 2, 8, 16. <IMAGE>

Description

SPECIFICATION Apparatus for fractionating a fibrous suspension The invention relates to apparatus for separating a fibrous suspension into a fraction with a predominant proportion of long fibres and a fraction with a predominant proportion of short fibres by means of fractionating apparatus.

Apparatus of this kind became known from "Wochenblatt für Papierfabrikation" 10 (1981), pages 334 to 339, and in particular the right-hand column on page 337. The object with this apparatus was to provide an operating method for the fractionating apparatus which was as operationaily reliable as possible and achieved a high level of efficiency, that is, resulted in the best possible separation of long and short fibres, by using the known method of throughput regulation.

As is known, this throughput regulation involves the apparatus being operated in the vicinity of maximum strainer loading, and when over-loading phenomena occur in the motor drive either the throughput is reduced, that is, the throughput amount is throttled, or the outlet lines, especially that for the long fibre fraction, are throttled to a lesser extent. However, this method is not the optimum; it requires the through-flow, i.e. the processed fibre suspension, to be broadly constant, and there is also a danger that despite this the strainer may become blocked and that the apparatus will therefore break down.

The object of the invention is to provide apparatus which ensures that fractionation can be carried out in a troublefree manner, and with which, although the apparatus is operated close to the obstruction level of the strainer, reliable operation is achieved, i.e. with the fewest possible interruptions in operation.

The object is achieved according to the invention is apparatus of the kind cited in the introduction with the characteristic features given in Patent Claim 1.

Pulp concentration monitoring equipment is of course widely known as measuring equipment in the processing of waste paper. However, it has not hitherto been used in the way proposed in the invention, and in fractionating processes at most corresponding to the characterising section of Patent Claim 2. This monitoring equipment is fairly accurate, and it enables deviations in the consistency of 0.1% to be detected. This means that the apparatus is made very sensitive with a relatively simple construction, despite a higher level of efficiency. In this way, operating reliability is also brought to the highest possible level.

Naturally, it would also be possible to measure the amount by determining whether there were still an adequate throughflow in the long fibre line, for example. However, such measurement would have to be carried out with a very considerable outlay on a high level of precision. Even then the results would not be as favourable as with the method according to the invention.

In the following the invention is described with reference to an embodiment example shown on the drawing.

The fractionating apparatus is designated 1 herein, the concentration monitoring equipment in the long fibre line after the fractionating apparatus 1 is designated 4, corresponding concentration monitoring equipment in the inlet line 14 to the apparatus is designated 2. A throttle 5, for example in the form of a sliding valve or a ball valve, is provided in the long fibre line Lf, and a corresponding throttle is provided similarly in the short fibre line Kf. The opening of these throttles is controlled by the concentration monitoring equipment 4 via the consistency regulator 3. This sends its output signal to the pneumatic computer relays 9 and 10. The relay 10 which acts on the throttle in the short fibre line Kf receives its input' signal via an inversion component 11.The effect is thereby obtained that the two throttles open and close in inverse proportion to each other.

A consistency regulator 8 which acts on a valve 1 6 in a water line 1 5 through which dilution water can be supplied to the suspension is also connected to the consistency monitoring equipment 2, in order thus to obtain a constant consistency at the inlet to the fractionating apparatus 1.

Further correcting adjustment can be undertaken by means of manual control stations 18 and 19.

The fractionating apparatus 1 is thus operating with a throughput such that its strainer is operating almost at the obstruction level. If now the consistency regulator 3 detects via its consistency monitoring equipment 4 that too high a consistency has developed in the long fibre line, this means at the same time that the danger of the strainer becoming blocked is increased. The regulation system is therefore designed to open the throttle 5 further when this occurs, so that the danger of the strainer becoming blocked in the fractionating apparatus 1 recedes again.

Conversely, with the aid of this consistency monitoring equipment and consistency regulator the apparatus is also run so that it is virtually always operating near to the obstruction level of the strainer. In this way, the best fractionation effect is achieved. However, at the same time operating reliability is at its highest level with this method.

Variations in the amounts of pulp can also be accommodated by this apparatus, as long as these variations do not deviate downwards by more than 30% of the nominal value. Variations upwards are possible only to a very limited extent.

1. Apparatus for separating a fibrous suspension into a fraction with a predominant proportion of long fibres and a fraction with a predominant proportion of short fibres by means of fractionating apparatus, characterised by pulp concentration monitoring equipment in the long fibre line for controlling, via a regulator, the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Apparatus for fractionating a fibrous suspension The invention relates to apparatus for separating a fibrous suspension into a fraction with a predominant proportion of long fibres and a fraction with a predominant proportion of short fibres by means of fractionating apparatus. Apparatus of this kind became known from "Wochenblatt für Papierfabrikation" 10 (1981), pages 334 to 339, and in particular the right-hand column on page 337. The object with this apparatus was to provide an operating method for the fractionating apparatus which was as operationaily reliable as possible and achieved a high level of efficiency, that is, resulted in the best possible separation of long and short fibres, by using the known method of throughput regulation. As is known, this throughput regulation involves the apparatus being operated in the vicinity of maximum strainer loading, and when over-loading phenomena occur in the motor drive either the throughput is reduced, that is, the throughput amount is throttled, or the outlet lines, especially that for the long fibre fraction, are throttled to a lesser extent. However, this method is not the optimum; it requires the through-flow, i.e. the processed fibre suspension, to be broadly constant, and there is also a danger that despite this the strainer may become blocked and that the apparatus will therefore break down. The object of the invention is to provide apparatus which ensures that fractionation can be carried out in a troublefree manner, and with which, although the apparatus is operated close to the obstruction level of the strainer, reliable operation is achieved, i.e. with the fewest possible interruptions in operation. The object is achieved according to the invention is apparatus of the kind cited in the introduction with the characteristic features given in Patent Claim 1. Pulp concentration monitoring equipment is of course widely known as measuring equipment in the processing of waste paper. However, it has not hitherto been used in the way proposed in the invention, and in fractionating processes at most corresponding to the characterising section of Patent Claim 2. This monitoring equipment is fairly accurate, and it enables deviations in the consistency of 0.1% to be detected. This means that the apparatus is made very sensitive with a relatively simple construction, despite a higher level of efficiency. In this way, operating reliability is also brought to the highest possible level. Naturally, it would also be possible to measure the amount by determining whether there were still an adequate throughflow in the long fibre line, for example. However, such measurement would have to be carried out with a very considerable outlay on a high level of precision. Even then the results would not be as favourable as with the method according to the invention. In the following the invention is described with reference to an embodiment example shown on the drawing. The fractionating apparatus is designated 1 herein, the concentration monitoring equipment in the long fibre line after the fractionating apparatus 1 is designated 4, corresponding concentration monitoring equipment in the inlet line 14 to the apparatus is designated 2. A throttle 5, for example in the form of a sliding valve or a ball valve, is provided in the long fibre line Lf, and a corresponding throttle is provided similarly in the short fibre line Kf. The opening of these throttles is controlled by the concentration monitoring equipment 4 via the consistency regulator 3. This sends its output signal to the pneumatic computer relays 9 and 10. The relay 10 which acts on the throttle in the short fibre line Kf receives its input' signal via an inversion component 11.The effect is thereby obtained that the two throttles open and close in inverse proportion to each other. A consistency regulator 8 which acts on a valve 1 6 in a water line 1 5 through which dilution water can be supplied to the suspension is also connected to the consistency monitoring equipment 2, in order thus to obtain a constant consistency at the inlet to the fractionating apparatus 1. Further correcting adjustment can be undertaken by means of manual control stations 18 and 19. The fractionating apparatus 1 is thus operating with a throughput such that its strainer is operating almost at the obstruction level. If now the consistency regulator 3 detects via its consistency monitoring equipment 4 that too high a consistency has developed in the long fibre line, this means at the same time that the danger of the strainer becoming blocked is increased. The regulation system is therefore designed to open the throttle 5 further when this occurs, so that the danger of the strainer becoming blocked in the fractionating apparatus 1 recedes again. Conversely, with the aid of this consistency monitoring equipment and consistency regulator the apparatus is also run so that it is virtually always operating near to the obstruction level of the strainer. In this way, the best fractionation effect is achieved. However, at the same time operating reliability is at its highest level with this method. Variations in the amounts of pulp can also be accommodated by this apparatus, as long as these variations do not deviate downwards by more than 30% of the nominal value. Variations upwards are possible only to a very limited extent. CLAIMS

1. Apparatus for separating a fibrous suspension into a fraction with a predominant proportion of long fibres and a fraction with a predominant proportion of short fibres by means of fractionating apparatus, characterised by pulp concentration monitoring equipment in the long fibre line for controlling, via a regulator, the opening of a throttle in the long fibre line proportionally with the concentration measured.

2. Apparatus according to Claim 1, characterised by further pulp concentration monitoring equipment arranged in the inlet line to the fractionating apparatus and connected to a consistency regulator which acts on a throttle in a line for supplying diluting water into the inlet line to the fractionating apparatus.

3. Apparatus according to Claim 1 or 2, characterised in that said pulp concentration monitoring equipment in the long fibre line also controls, via said regulator, a throttle in the short fibre line proportionally with the concentration measured.

4. Apparatus according to any one of Claims 1 to 3, characterised in that a proportional regulator is provided for the throttle in the long fibre line and, if provided, also-for the short fibre line.

5. Apparatus for separating a fibrous suspension, constructed, arranged and adapted for use substantially as hereinbefore described with reference to, and as shown in, the accompanying drawing.