FI72154B - PROCEDURE FOR THE MEASUREMENT OF FOER MALNING AV LIGNOCELLULOSAHALIGIGT AEMNE TILL FIBERMASSA - Google Patents

Description

1 72154

The present invention relates to a process for preparing a pulp from a lignocellulosic material, including grinding in a steam pressure grinder, wherein the ground fibrous material together with the steam therein is conveyed to the outlet via a pipeline. The invention also relates to an apparatus for grinding a lignocellulosic material into a pulp, the apparatus comprising a container for heating the substance, a conveying screw for conveying the substance to the refiner, and a pipeline and a valve for conveying the ground material from the refiner to the outlet unit.

It is already known to lead the fibers and steam to an expansion tank, cyclone or the like, in which, when expanded, the steam maintains the flow of steam and fibers. However, the reuse of steam thus expanded is most often limited by its low pressure and impurities (fibers and solutes).

The object of the invention is to provide a method and a device which do not have the disadvantages of the known solutions. According to the invention, this is achieved by separating a substantial part of the steam from the fibers in an outlet unit and returning it to the refiner or to a container in communication with the refiner without swelling in between, and to remove the fibers for further processing. The device according to the invention is characterized in that the device has means for squeezing steam from the pulp, as well as means for returning the steam back to the refiner or tank.

Other preferred embodiments of the invention will become apparent from the appended claims.

The invention represents a considerable saving of steam compared to the amount of steam hitherto used to carry out the known cycle when steam and fibers are sucked into the cylinder by means of a piston and the steam contained in this mixture is pressed out of the mixture by the same piston. The extruded steam is returned to the grinder and the fibers are mixed with water to form a pulp.

The method is applicable to all defibering processes in which the defibering of the lignocellulosic material takes place in a state filled with impregnated steam above 100 ° C, usually at a temperature of 130 ° C to 200 ° C with a vapor pressure of 297-1599 kPa.

The invention will now be described with reference to the accompanying drawings, in which Figure 1 shows a device according to the invention, and Figure 2 shows a system in which two devices are connected together.

In Fig. 1, reference numeral 1 shows a storage silo for a lignocellulosic raw material, e.g. wood chips. The chips are fed by means of a screw feeder with a double former 2 into a pressurized container in which the substance is heated. From a source not shown, for example, steam is supplied via a pipeline 18 to the tank 3 to heat the substance. The container 3 communicates via a conveying screw 4 at its lower part with a refining part 20 consisting of a closed housing 5 to which a refining plate 21 and a rotating grinding wheel 6 are rotated by an electric motor 22. The raw material fed by the conveying screw 4 is defibered as it passes between the grinding plates 6 and 21. At the same time, steam flows between the grinding plates into the housing 5.

The material and steam defibered from the housing 5 are led via a pipe 7 to an outlet unit consisting of an inlet valve 8, a cylinder 9, a piston 10, a shut-off flange 11, a screen plate 12, a non-return valve 13 and hydraulic or pneumatic cylinders 14 and 15.

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One cycle of operation of the output unit takes place as follows: The piston 10 is initially in its extreme position on the right as shown in Fig. 1 and the closing flange 11 is vapor-tight by means of a cylinder 14. The non-return valve 13 is closed. Valve 8 opens. As the piston 10 starts to move by means of the cylinder 15 in the figure to the left, it absorbs steam and fibers through the pipe 7 and the valve 8 from the housing 5. When the piston 10 reaches its extreme position in the figure on the left, the valve 8 closes and the piston 10 starts to move to the right. The screen 12 allows steam, but no fibers, through the non-return valve 13 and the flexible pipe 16 into the tank 3.

When the fiber dose in the cylinder 9 has been sealed between the piston 10 and the shut-off flange 11 at a predetermined pressure, the flange 11 moves to its right-hand position in the figure by means of the cylinder 14 and the non-return valve 13 closes. The piston 10 moves to its starting position and pushes the fiber dose out of the cylinder 9. The fiber dose is removed between the piston 10 and the flange 11 by water, compressed air, mechanically or in another suitable manner and mixed with water into a pulp. The flange 11 closes by means of the cylinder 14 and the cycle is at the end.

To minimize the work, it is advisable to connect two or more units together according to Figure 2 to operate alternately so that the suction step of the second unit assists the compression step of the second unit. Several units also compensate for pressure fluctuations in the housing 5.

Another way to reduce the amount of work required is to arrange the pressure in the refiner also in the piston 10, e.g. by enclosing it in a steam-tight cylinder 24, to which steam is introduced from the same source as in the tank 3.

Claims (7)

721 54 A method of making a pulp from a lignocellulosic material, including milling in a steam pressure mill (20), wherein the milled fibrous material together with the steam therein is transferred via a pipeline (7) to an outlet unit (23), and a substantial portion of the steam is separated and returned to the refiner (20) or to the tank (3) in communication with the refiner without swelling therebetween, characterized in that the fibers are transported out for further processing and the fibers and steam are sucked into the steam-tight cylinder (24) by the piston (10) and pushed a substantial portion of the steam passes through a screen plate (12) or the like back to the refiner (20) or tank (3). A method according to claim 1, characterized in that the two or more output units (23, 23 ') are connected to each other mechanically or hydraulically to operate in pairs so that one operates in the suction phase while the other operates in the compression phase. An apparatus for grinding lignocellulosic material in a fibrous scissor, the apparatus comprising a container (3) for heating the substance, a conveying screw (4) for conveying the substance by the grinder (20) and a pipe (7) and a valve (8) for conveying the ground substance from the grinder (20) 23), characterized in that the device has means (9, 10, 11, 12) for squeezing the steam from the pulp, and means (13, 16) for recirculating the steam to the refiner (20) or to the tank (3). Device according to claim 3, characterized in that the means for compressing the steam from the pulp consist of an inlet valve (8) connected to the cylinder (9), a piston (10) movable in the cylinder (9), a closing flange (11) fitted to the cylinder end and a screen plate (12). ) and a hydraulic or pneumatic cylinder (15) guiding the piston (10). Il 72154 Device according to one of the preceding claims, characterized in that the means for returning steam to the refiner (20) or tank (3) consist of a non-return valve (13), a flexible pipe (16) and a hydraulic or pneumatic cylinder (14) controlling the shut-off flange (11). . Device according to Claim 4 or 5, characterized in that the two or more outlet units are connected in pairs hydraulically or mechanically so that one operates in the suction phase and the other in the compression phase. Device according to one of the preceding claims, characterized in that the vapor pressure prevailing in the refiner is arranged on both sides of the piston (10) by applying vapor pressure to the vapor-tight cylinder (24) from the refiner's steam line (18) via a pipeline (25). 72154