FI89946B - Method of treatment and a disperser for fine distribution of wood fibre pulp, especially that containing waste paper - Google Patents

Abstract

In a method of treating wood fibre pulp, especially that containing waste paper, the pulp is dewatered and heated by means of superheated steam under pressure before the pulp is sent to a disperser 10 for fine distribution. From the disperser, the pulp is transferred without separate escaping of the steam to an output plug screw 20, at the end of which is formed a tight plug consisting of compressed pulp. The end of the plug screw 20 is closed by a valve element 21 which opens when the pressure of the formed plug exceeds a predetermined value. The protected subject also includes a disperser 10 with essentially rectangular outlet, connected to a plug screw 20 of the indicated kind. <IMAGE>

Description

89946

The present invention relates to a method for treating wood pulp, in particular pulp containing waste or recovered paper, according to the preamble of claim 1.

The invention also relates to a diffuser, in particular a diffuser according to the preamble of claim 6, for grinding wood fiber pulp.

When treating such a pulp according to conventional techniques, the pulp is treated in several processing steps comprising dewatering the pulp in a dewatering area by means of a screw press to increase the consistency of the pulp from 4-6% feed to about 30% discharge.

: / · The pulp is directed from the dewatering zone to the heating zone, where: * · 'the pulp is fed forward while steam is fed to the zone. The pulp is treated in this area by means of a so-called .... pulp dry diffuser, which converts the pulp into granules. .. or into small particles or a similar shape so that the mass can be heated quickly and uniformly to the desired temperature by means of saturated steam. The average steam consumption is about 300 kg / ton of pulp.

The heated and comminuted pulp is then directed to a decomposer, which allows gentle handling of the pulp material at high consistencies. This is made possible by means of mutually opposed toothed discs ···, one of which rotates relative to the other. The spreading interval is adjusted during operation, suitably by means of an electro-hydraulic Λ system.

• 2 3 9 i 4 6 The temperature of the treated pulp can be varied between, for example, 80eC and 120eC depending on the properties of the treated pulp. The fibers present in the pulp are easily broken or damaged at too high temperatures.

The consistency of the pulp leaving the heating zone can be up to 30%. This consistency decreases to some extent due to the pressurized steam supplied to the area.

During the decomposition process, dilution water is usually added and thus the consistency of the pulp pumped from the decomposer is 3.5 to 6%. However, the consistency of the pulp can in some cases be as high as about 10%.

Approximately 12-13% has a limit at which it is no longer possible to pump pulp with current techniques.

However, there are several cases where a thicker mass is required, in which case values of 25-30% would be desirable. It is not possible to obtain such consistencies. he used until the pulping methods used.

'*' At the same time, it is desirable to increase the temperature and / or pressure of the feed * * · in which case such a wish occurs: V especially in cases where pulp containing highly liquid recovered paper is treated.

However, it is difficult to effectively recover the heat content of the steam. For example, there is a risk that steam will blow out of the system and thus cannot be fully utilized. si.

Examples of the current state of the art are presented in SE, B, 435 532 and FI, B, 66927 (Sunds Defibrator) and FI, B, 58171 (Central Laboratory). According to these known methods and devices, steam is separated and removed through separate steam removal pipes to allow steam to be reused.

None of these known methods involve the treatment of recovered paper, especially pulp containing very dirty paper.

It is a primary object of the present invention to provide an improved method of treating wood fiber pulp which enables the heat content of the steam fed to the heating zone to be utilized more efficiently, allowing more efficient treatment of highly soiled recovered paper and increasing pulp density of the final product treated.

Another object of the invention is to provide a treatment method which can be adapted to the prevailing parameters of the treated product by simple means and which gives a good result when the temperature prevailing in the treatment process varies between less than 100 ° C and substantially above 100 ° C. , and which produces the final product at mass densities which have hitherto been considered impossible to achieve.

It is a further object of the present invention to provide an apparatus for treating wood fiber pulp, especially wood fiber pulp containing recovered paper, which allows more efficient utilization of the heat content of the fed steam without causing substantial structural complexities and allows simple adaptations and adjustments according to the degree of soiling and other properties. -. * can be easily adjusted according to the desired characteristics of the final product, in particular the consistency of the mass fed.

• ·

Thus, the present invention relates to a method of the type described above, characterized in that the pulp comminuted from the diffuser is fed to a screw press, the other end of which is closed, without separate steam removal, to form a predominant sealing plug of the compressed pulp.

The plug formed in the screw press provides an effective seal to prevent steam from escaping from the system, making it possible to increase the bulk consistency of the treated final product.

Thus, the process according to the invention makes it possible to obtain mass densities of 30% or more.

It is also possible to increase the temperature of the steam in the heating zone, which is particularly advantageous when handling very dirty waste paper. Within the scope of the invention, it is possible to use temperatures of up to 120 ° C or even higher. The pressure of the steam fed to the heating zone can also be increased to improve the yield of the treatment process.

In practice, it is advantageous to close said other end of the screw clamp by means of a valve device which is activated against the • · »:. pressure and which opens when the pressure applied by the plug to the valve exceeds a predetermined value.

I · ·· • • ·· The higher the back pressure applied by the valve device, the harder or denser the plug and the more effective the removal of contaminants from the pulp.

Likewise, within the scope of the invention, it is possible to adjust the steam pressure and temperature as well as the back pressure applied by the valve according to the degree of soiling of the mass.

* ♦ • ·

The invention also relates to a diffuser of the type described above for grinding a water-pulp pulp released from water and heated, characterized in that the discharge pipe of the comminuted pulp leads to a screw press, by means of which the mass • · • * 5 69946 is fed forward without separate steam removal and that one end of the screw press is closed by a valve device so that the advancing mass is compressed and forms a plug closure at said other end.

Other features of the device according to the invention are set out in the subclaims.

In order to illustrate the invention and its features, an embodiment will be explained in more detail below with reference to the schematic drawings.

Figure 1 shows the basic structure of some components of a processing plant for carrying out the method according to the invention.

Figure 2 shows a partially sectioned side view of a diffuser forming part of a treatment plant and its interaction with a screw press or "plug removal screw" to form a pulp plug which seals the system.

Figure 3 is an end view of the arrangement shown in Figure 2.

· («• * ·’ Figure 1 schematically shows some essential parts of a pulp processing plant containing recovered paper.

• ·

The pulp is fed through a pipe 2 to a screw-type dewatering device 3, in which water is removed from the pulp from a feed consistency of 2% to a drainage consistency of 8%, whereby water compressed from the pulp is removed via a pipe 19.

\. The dewatering range also includes a screw press 4 which increases the pulp consistency from a feed value of 6% to a discharge value of 30%. The screw is coated with carbide. The screw clamp is designed · »· .V so that all parts of the disintegration system are easily accessible. The pulp is then transferred by a plug screw 5 and 6 .1 a «/ 5 j> -» 6 with a vertical conveying screw 6 to a dry diffuser 7 located in the heating zone of the treatment plant. The steam is led from different points along the axial length of the dry pulp diffuser through the manifold system 8. The steam pressure and temperature are varied according to the degree of soiling of the feed mass.

The pulp dry diffuser converts the pulp plug into a particulate shape, which allows the pulp to be heated uniformly and quickly. In this way, the finely divided mass can be efficiently heated to the desired temperature by means of saturated steam. The steam overpressure is monitored by means of suitable valve devices.

The heated pulp granules are transferred from the dry pulp diffuser 7 by means of a conveying screw 9 to the diffuser 10, which is shown on a larger scale in Fig. 2, in which parts of the diffuser have been cut away.

As can be seen in Figure 2, the diffuser comprises a housing 10a provided with an inlet pipe through which the pulp is fed axially to the central supply area.

.... The diffuser comprises a rotor 11 which is driven by an electric motor ____ and which supports pump blades at an end in the vicinity of the supply area. The rotor also supports a disc 12 with a circumferential portion with teeth 12a. These teeth work in conjunction with the teeth of a toothed ring or disc rigidly mounted in the housing to grind the pulp entering the diffuser. Dilution water is fed to the diffuser via pipes 13, 14.

«·. The diffuser also comprises an outlet pipe 16 connected by means of a flange 10b.

The flange connection 10b of the discharge pipe 16 is connected to the corresponding flange connection 7 of the screw clamp or plug removal screw 20. A flap valve 21 is provided at one end of the screw 20, which is articulated to the pivot pin 22 and is activated by a pneumatic piston cylinder projection 23, 24. The setting of the piston cylinder device is adjusted by a control device (not shown) so that the flap valve 21 The flap valve thus opens when the pressure exerted by the plug exceeds a predetermined pressure, whereby the plug is removed in the screw at the desired mass density, e.g. at a mass density of 30% or more.

As can be seen from the above, the pulp plug acts to seal the system so that the heat content of the steam fed to the system at overpressure and at a relatively high temperature, e.g. 110-120eC, can be utilized as efficiently as possible.

The pressure and temperature of the steam fed into the system are suitably controlled when the mass to be treated is very dirty. Likewise, the back pressure applied to the butterfly valve 21 by the piston-cylinder device 23 is adjusted according to the degree of soiling of the pulp.

• · · ____ It can be seen from Figures 2 and 3 that the flange connections 10b, 20b located between the diffuser and the screw 20 have a straight line. . an angular cross-section, the inner dimension of the diffuser outlet pipe and the screw inlet pipe, i.e. the flow area of the mass transferred from the diffuser to the screw corresponds approximately to the diameter of the rotor disc 12 multiplied by the entire width of the diffuser in the region of the interacting toothed discs.

· * ’As mentioned above, arranging a plug removal screw of the above type for direct connection to the diffuser *: *. allows the pulp product to increase the consistency to 30% or more and also allows efficient recovery of the energy content of the steam fed to the system, as a pulp plug formed at one end of the screw 20 effectively seals the system so that the heat content of the fed steam can be utilized .

The shape of the diffuser outlet pipe is significant in that it is not possible to pump a very thick mass through a narrow pipe or narrow space by means of a diffuser.

Thus, according to the above embodiment, the diffuser outlet pipe has relatively large dimensions. It is not essential to the invention the way in which the outlet pipe is arranged in other respects or how the diffuser and the plug removal screw are arranged in relation to each other. The only essential feature in this respect is that the two units together form a closed system and that the mass plug formed in the screw prevents steam from escaping from the system.

The components located upstream of the diffuser in the treatment system can be changed according to the prevailing conditions.

Finally, it should be emphasized that it is not possible at this time to indicate exactly which hand-held temperatures can be applied or which mass concentrations can be achieved within the scope of the present invention. However, it has been found that the invention allows the use of considerably higher working temperatures and provides a significantly higher mass consistency than has hitherto been considered possible. The numerical data presented are to be considered as approximate in this respect and do not exclude the possibility of higher values in the practice of this invention.

Claims (9)

9, ~ c,. Γ-: exam requirements A method for treating wood fiber pulp, in particular pulp containing recovered paper, wherein after the pulp has been passed through a dewatering zone, it is fed and passed through a heating zone while feeding steam to the zone, and then comminuted in a diffuser, characterized in that the comminuted pulp is fed from a diffuser without separate removal of steam to a screw press, one end of which is closed to compress the pulp and form a sealing pulp plug at this other end. A method according to claim 1, characterized in that said other end of the screw press is closed by a valve device producing an opposite bore, which opens when the pressure applied to it by the plug exceeds a predetermined value. Method according to Claim 2, characterized in that the pulp is fed to the screw press at temperatures of more than 100 ° C, optionally more than 110 ° C and, in certain cases, more than 120 ° C. A method according to any one of claims 1 to 3, if the dilution water is fed to the diffuser, characterized in that the mass consistency of the plug formed in the screw press is more than 10%, possibly more than 20% and in some cases more than 30%. Method according to one of Claims 1 to 4, in which the highly dirty mass is treated, characterized in that the pressure and temperature of the supplied steam are adjusted and the back pressure produced by the valve device is adjusted according to the degree of soiling of the mass. A diffuser for grinding wood pulp, in particular pulp containing recovered paper, the diffuser comprising a) a housing (IGa) with a feed pipe for feeding the pulp to the feed area in a substantially axial direction, b) a rotor (11) preferably supporting a pump vane in the feed area , c) a disc (12) supported by the rotor and having a circumferential portion provided with teeth (12a) cooperating with the opposite teeth of the ring or disc, preferably rigidly mounted in the housing (10a), for grinding the pulp, and d) an outlet pipe (16) for comminuted pulp, characterized in that the outlet pipe is connected by means of a connecting piece (10b) to a screw press (20) which acts to convey the pulp without separate steam removal to one end of the screw, this other end of the screw being closed by a valve device (21) compress the screw to form a sealing plug puristxmen near this other end. Diffuser according to claim 6, characterized in that the coupling piece (10b) has a substantially rectangular cross-section, the inner dimension of the coupling piece corresponding approximately to the diameter of the rotor disc (12) and the entire width of the diffuser in the area of its toothed discs. Diffuser according to Claim 6 or 7, characterized in that the valve device (21) is kept closed, e.g. by a pneumatically operated mechanism (22, 23, 24) which allows the valve to open when the pressure applied to the valve by the formed plug exceeds a predetermined specified value. Diffuser according to one of Claims 6 to 8, characterized in that it is intended, in particular, for treating highly contaminated pulp which is fed to the feed pipe after the steam has been fed, characterized in that it has means for applying the pressure and temperature of the steam fed to the pulp. to adjust the back pressure produced by the valve device (21) according to the degree of soiling of the pulp. 11 8 9 9 46