CA1233685A - Method and device for manufacturing cellulose pulp - Google Patents

Abstract

Abstract A method and a means for manufacturing cellulose pulp from ligno-cellulose fibre material wherein the fibre material is treated under steam pressure. The treatment is carried out in a mill or similar means under such conditions that substantially all the liquid present in the material and/or added thereto during the treatment is converted into gaseous form or steam. The gas or steam thus generated, plus any added gas, is used to convey the cellulose material at high velocity to at least one subsequent separating vessel wherein the fibres entrained with the gas or steam are given a trajec-tory of motion in the course of which the fibre material is sorted with respect to weight, surface area, or other distinguishing characteristics.

Description

The present invention is concerned with a method of manufacturing cellulose pulp from ligno-cellulose material wherein -the material is ground in a mill which is subjected to internal steam pressure. The invention is further concerned with means for the implementation of the method.

In such manufacture of cellulose pulp, especially for paper making, it is necessary in order for the pulp to be used efficiently that said pulp consist of a uniform fibre fraction lo without oversize noncom minuted (non-defibrated) knots or bundles of fires. In conventional pulp manufacture this is achieved by slurring the manufactured pulp with water, thereafter it is caused to pass in the form of a relatively thin suspension through a variety of fibre sorting means such as screens equipped with perforated or slotted plates for the removal of shrives, or so-called hydrocyclones wherein the stock is cleaned of shrives and insufficiently commented (defibrated) bundles of fires by centrifugal action.

All these so-called water-dependent systems suffer from the drawback of requiring large quantities of water, in the order of 1:300 to lo which water must be removed in subsequent treatment before the pulp is transported to the point of use, baled, etc. The suspension of the pulp in water and the trays-partition of the large volumes of liquid to screens and hydrous-clones takes a great deal of energy, and, moreover, the oversize bundles of fires or shrives removed in the screens and hydrous-clones must be detoured again to a concentration of approxi-mutely 1:2 to 1:4 for efficient further treatment thereof.
The present invention provides a method of the above-mentioned type whereby the pulp as manufactured can be cleaned and the solves or bundles of fires removed in the cleaning pro-cuss can be subjected to further treatment, without the addition of substantial quantities of water which must subsequently be removed by various dewaterlng methods. The present invention I

also provides such a method, economical of energy and water, which can be implemented in combination with the mechanical sepal ration of lignocellulose material at - lo -I

temperatures in excess of Luke and/or at pressures exceeding normal atmospheric pressure.

According to the present invention there is provided a method of producing pulp from moisture-containing cellulosic fiber material comprising: treating the material in a pressurized refining zone in a liquid-gas phase at super atmospheric pressure and correspondingly elevated temperature until substantially all of said liquid-gas phase is converted in-to a pressurized gaseous phase; passing a suspension of refined material and gaseous phase under high velocity into an initial fiber-separating zone by using the energy of said pressurized gaseous phase as the propel-tent high-velocity force; separating fiber material from said initial fiber-separating zone by imparting to the suspension by cyclonic means a trajectory of motion calculated to fractionate said suspension into an accepted fraction and a reject fraction according to weight, size or surface area of the fibers; disk charging the reject fraction from said initial fiber-separating zone and successively passing the accepted fraction to a steam separator at least one further refining zone and to at least one further fiber-separating zone for further fractionation; passing the accepted fraction from said further fiber-separating zone to a collection station and recycling the reject fraction from said further fiber-separation zone is passed to a reject refining zone and said steam separator before being recycled to said further refining zone. Suitably the reject fraction from said initial fiber-separating zone is passed to said reject refining zone and recycled to said further refining zone along with the reject fraction from said at least one further fiber-separating zone.
Preferably the treatment includes grinding by mechanical means at temperatures in excess of 100C and/or under pressure in excess of atmospheric pressure. In one embodiment of the present invent lion the cellulose suspension is given a trajectory wherein the fibre material is sorted by changing the direction of flow of the cellulose suspension. Alternatively the cellulose suspension is given a trajectory wherein the fibre material is sorted by gravy I

t' iota. Yet again the cellulose suspension is given a trajectory wherein the fibre material is sorted by means of changes in the flow velocity of the cellulose suspension. Still further the cellulose suspension is blown into at least one shell wherein the fibre material is given a rapid spiraling motion to separate the components thereof.

The present invention also provides an apparatus for effecting -the aforesaid method which comprises at least one mill wherein the material is ground under steam pressure, the material being mechanically commented and at - pa -LO I

the same time all the liquid present in the material and/or added thereto during the grinding process being converted in-to gaseous form or steam, at least one fibre separator downstream o-f said mill and connected thereto including a S steam collecting and/or gas-collecting shell which is shaped so that the cellulose suspension, dispersed in the gas or steam, blown whereinto is given a trajectory in -the course of which the fibre material is sorted with respect to pro-determined distinguishing characteristics. Suitably the separator includes a downward-tapering conical shell wherein there is provided a central outlet pipe connected to a disk charge line from the separator for acceptable material, and a discharge means at the bottom of the shell for reject material. Desirably the centrally positioned outlet pipe is adapted to be raised and lowered to vary its vertical post-lion thereof in relation to the conical lower part of the shell, In an embodiment of the invention the separator includes a shell with a downward-tapering conical lower part, an inlet pipe disposed in the centre of the shell, which pipe is closed at the top and open at the bottom, a feed pipe for cellulose suspension connected to the inside of the inlet pipe, a dish disposed below the inlet pipe with a clearance thereto, and outlet openings for acceptable and reject material at the top and bottom ends, respectively, of the shell.

In another embodiment of the invention the swooper-ion includes an elongated shell with an inlet pipe for fibre material connected to one end thereof, an outlet pipe for steam at the other end of the shell, and outlets at the bottom of the shell for reject and acceptable material respectively, a partition between the last-mentioned out-lets to separate the different stock fractions, and disk charge means for the conveyance of the material to the - 2b-., outlets. Suitably the partition is movable to control the separation of the fibre material.

The invention will be more particularly described hereafter with reference to an embodiment, illustrated in the accompanying drawings, of a plant for the implementation of the method, in which drawings;

Figure 1 is a schematic diagram of a plant implementing the method;

Figure 2 is a section through a type of mechanical separator that can be used in the plant of Figure l;

Figure 3 is a section through another embodiment of mechanical separator; and Figure 4 is a longitudinal section through yet another type of separator.
In the plant illustrated in Figure 1, the number 10 indicates a feed hopper for a lignocellulose fibre material, such as wood chips. From the hopper 10 the material is fed by a screw 12 to a preheater 14 and from there by a screw 16 to a first defibrator 18, such as a disc defibrator, wherein the lignocellulose material, such as wood chips, is commented to single fires or bundles of fires. In this treatment, which may or may not be preceded by chemical treatment and/or heating in the preheated 14, most of the energy supplied to the material in -the defibra-ion 18 is converted into heat. The natural moisture present in the material and/or water added to prevent overheating of the fibre material during defibration in the defibrator 18 is thereby converted into steam.
I The steam thus generated, together with steam, _ I

3 I R j compressed air, or other gases added during or after the defibration process in the defibrator 18, is now used accord ding to the invention for the very effective removal of large, unwanted bundles of fires or shrives without the 5 addition of water. This separation is effected by using the gas or steam so generated to carry the fibre material at high velocity via a pipeline 20 from the defibrator 18 to at least one separating vessel 22. In this vessel 22 fires and/or fibre bundles of various sizes are separated by imparting to the cellulose suspension a motion such that a sorting of the fires takes place according to certain disk tinguishing properties such as weight, size, or other semi-far feature. Separation may be assisted by changes in the velocity or motion of the cellulose suspension or by gray viny, as is described more particularly below with reference to Figures 2 to 4.

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Ed -3 ~2~368ij The accepted fires pass on via pipeline 24 to a cyclone steam separator 26, while the reject fires or bundles are fed by a Scrooge 28 to an outlet pipe 30. The accepted fires are fed from the cyclone steam separator 26 to a refiner 32 for a second refining step From the refiner 32 the cellulose suspension is carried via a pipeline 34 to a further separating step, Wesley in the embodiment illustrated consists of three units 36, I and 40. These units are in the form of cleaning cyclones whose reject outlets are connected to a discharge means 42 whose outlet is connected to a pipeline 44 leading to a collector 46.
The reject line 30 from the first cyclone separator 22 is also connected to the collector 46, so that all reject fires and fibre bundles are collected therein. The contents of the collector 46 are fed to a doff-orator 48 where the reject fires or fibre bundles are retreated and commented and the outlet of the defibrator 48 is connected via a pipe-5 line 50 to -the cyclone steam separator 26, i.e. the cellulose suspension discharged from the defibrator 48 is fed to the second refining step 32.
The outlet from the cyclone 36 in the second cleaning step is connected to the cyclone 38, whose outlet is in turn connected to cry-clone 40. The accepted flow front cyclone 40 is fed via a pipeline 52 to 20 a sicken steam separator 54 frown which the stock is fed to a stock chest 56. From the stock chest 56 the stock is drawn off via a pipeline 58 for further treatment or use. In the embodiment illustrated the pulp, after being dried in a drying plant 60 which may be served by steam from the cyclone steam separators 26, 54, is conveyed via a pipe-line loop 62 and pump 64 to a baling station 66.
The separator 22 used in the first separation step may, as shown in more detail in Figure 2, include a steam-collecting and/or gas-collect-in shell into which the pipeline 20 from the first defibration step discharges and into which the cellulose suspension is blown at high velocity by the energy supplied in the fibre separation step in the form of electricity and/or steam or compressed gas. On entering the cyclone 22 the pulp is thus given a rapid spiraling motion while at the same time the gas or steam fed to the cyclone causes the cellulose suspension to pass, against the action of centrifugal force, to an outlet pipe 68 located at the centre of the cyclone 22, to which pipe the pipeline 24 is connected. The sorting of the fires or fibre bundles present in the ~23~
gas or steam suspension is easily controlled by varying the quantity of steam or gas passed through the cyclone. For this purpose the pipe 68 may be arranged to be raised and lowered in the cyclone 22 so that by varying the vertical position of the outlet pipe 68 in relation -to the conical lower part of the cyclone one can likewise control the swooper-lion of the fires or fibre bundles. Through the action of centrifugal force the larger, heavier fires and fibre bundles will offer greater resistance to the change of direction inwards towards the centre pipe 68 of the cyclone 22, with the result that the heavier particles will be lo entrained towards the bottom of the cyclone, where they are discharged by means of e.g. the discharge screw 28 shown in Figure 1 to the disk charge line 30.
In the embodiment illustrated in Figure 3 the separator consists of a shell 70 having a centre pipe 72 to which is connected a feed line for the cellulose suspension such us the feed line 20 in Fig. 1. Thus, in this embodiment the cellulose suspension enters the centre pipe and is set in rapid spiraling motion therein while simultaneously flowing downwards in the pipe 72. Below the pipe 72 there is provided a conical dish 74 on which the cellulose suspension impinges. The lighter, act suitably fires will then be entrained with the gas or steam upwards inside the shell 70 to the outlet 76 which is connected to the pipeline 24 in Figure 1, while heavier fires and fibre bundles drop down inside the shell 72 to the conical bottom thereof, where they are discharged by the screw 28 to the reject line 30.
The sorting of fires and fibre bundles can also be effected by gravity, as illustrated in Figure 4. In this case the cellulose suspend soon is introduced via a pipeline 78 at one end of an elongated shell 80 and blown at high velocity into the interior thereof. The heavier fires and fibre bundles fall more rapidly to the bottom of the shell 80, while lighter, acceptable fires follow a flatter trajectory inside the shell. In the bottom of the shell there are provided feed screws 82 and 84 for the respective stock fractions, which screws are separated by a partition 86. The screw 82 carries the rejected fibre bundles and shrives to an outlet 88 which discharges to vessel 46 in Figure 1. The screw 84 carries the acceptable fires to an outlet 90 which is connect-Ed to the second refining stage 32 in Figure 1. The steam is discharged ~233~i8~ j via an outlet 92 from the shell 80 to a steam cyclone 94. By making the partition 86 movable in the lengthwise direction of the casing 80 it is possible to control easily the sorting of the fires or fibre bundles of various sizes present in the gas or steam suspension.

Claims (2)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. According to the present invention there is pro-vided a method of producing pulp from moisture-containing cellu-losic fiber material comprising: treating the material in a pres-surized refining zone in a liquid-gas phase at super atmospheric pressure and correspondingly elevated temperature until substan-tially all of said liquid-gas phase is converted into a pressur-ized gaseous phase; passing a suspension of refined material and gaseous phase under high velocity into an initial fiber-separat-ing zone by using the energy of said pressurized gaseous phase as the propellant high-velocity force; separating fiber material from said initial fiber-separating zone by imparting to the sus-pension by cyclonic means a trajectory of motion calculated to fractionate said suspension into an accepted fraction and a reject fraction according to weight, size or surface area of the fibers; discharging the reject fraction from said initial fiber-separating zone and successively passing the accepted fraction to a steam separator at least one further refining zone and to at least one further fiber-separating zone for further fractiona-tion; passing the accepted fraction from said further fiber-sepa-rating zone to a collection station and recycling the reject fraction from said further fiber-separation zone is passed to a reject refining zone and said steam separator before being rec-ycled to said further refining zone.

2. The method according to claim 1, in whcih the reject fraction from said initial fiber-separating zone is passed to said reject refining zone and recycled to said further refin-ing zone along with the reject fraction from said at least one further fiber-separating zone.