EP3027806B1 - System and method for processing fibrous materials - Google Patents

Description

The invention relates to a plant for processing pulps with a pre-damper, a digester and a refiner, which is connected via a blow pipe with a dryer, wherein in the blowpipe means for continuously discharging a portion of the steam is arranged and that a discharge opening for steam is connected from the device via a steam line with the pre-damper and / or the digester, wherein the device is in open communication with the continuing in the flow direction blowing line.

The invention further relates to a process for processing fibrous materials, wherein the raw material to be processed, e.g. Wood chips, one after the other a pre-damper, a stove, a refiner and a blower is fed to a dryer, wherein the pulp-steam mixture after the refiner and before the dryer in a device continuously a portion of the steam is removed and that the extracted steam the Pre-damper and / or the digester is supplied, wherein the pulp-steam mixture from the device (15) is continuously further promoted by an open connection to the blow pipe.

At present, the steam that emerges from the refiner together with the fibers is not recovered, but is introduced into the dryer. Among other things, this represents an increased expenditure of energy for the drying EP 1834747A2 a method and an apparatus for the production of moldings from lignocellulosic bevels. The plant has a separation device, which is designed as a ceramic filter. The DE 3728123A1 further describes a process for the production of shredded pulp material for the production of fiberboard. Here, the vapor-fiber mixture resin is supplied before it is cooled and the steam, preferably completely, is separated under atmospheric pressure. The impregnated wood fibers are then conveyed intermittently via a rotary valve air flow and fed through a further rotary valve intermittently to a molding station. The DE 102008026677B3 shows a method for drying lignocellulosic fibers and a vapor separator thereto. In this method, a water vapor fiber stream is directed onto a screen drum, with the water vapor passing through the screen drum and the fibers being caught and scraped off the surface of the screen drum. The pressure-tight measuring sluice then directs the fibers to a dryer. After the dryer, the superfluous air-water vapor mixture is deposited in a cyclone separator.

The invention is therefore based on the object to provide a system and a method in which the energy expenditure u.a. can be reduced for drying.

This object is achieved in a system of the type mentioned above in that the device is a cyclone and the discharge opening is formed by a dip tube.

Through the use of a cyclone for the continuous discharge of steam excess vapor can be separated, which is not needed for the transport of the fiber and can be reused. This thermally relieves the dryer and thus saves energy. Furthermore, this can lead to a reduction of emissions at the dryer. The withdrawn excess steam can be introduced directly to the preheating of the raw material in the pre-damping and / or in the digester. There are several attempts to separate the steam from the fiber-steam mixture. This can be accomplished with fiber centrifuges, cyclones, or other centrifugal separator. This device must be sealed against the environment. The discharge from the device therefore takes place eg via rotary valves. This has the consequence that fibers are partially compressed and, for example, the classic Blasleitungsbeleimung necessary for MDF production does not work or worse. In dry gluing, in turn, the clumping of the fibers leads to difficulties in further processing.

Since only a portion of the steam is removed in the device, the device need not be sealed off downstream of the blowpipe and the pulp-steam mixture can be easily further promoted with a sufficient amount of steam in the blowpipe without causing lumping the fibers come.

Further preferred embodiments and embodiments of the invention are the subject of the remaining subclaims.

Further features and advantages of the invention will become apparent from the following description of a preferred embodiment of the invention with reference to the accompanying drawing, in which a plant for the processing of fibrous materials is shown schematically.

The device has a pre-damper 1, to which raw material to be processed, for example wood chips, is supplied via a line 2. After the pre-damper 1, the pre-damped raw material via a plug screw 3, a Cooker 4 and a Kocheraustrag 5 then fed to a refiner 9. After the refiner 9, the thus prepared pulp-steam mixture is fed through a blow line 6 to a dryer 7.

The throughput of pulp-steam mixture can be adjusted by means of a first blow valve 8 on the refiner 9. Before the dryer 7, a device 10 for gluing the fibrous-vapor mixture in the blowpipe 6 may be arranged. The pre-damper 1, the cooker 4 and the refiner 9 can be supplied via lines 11, 12, 13, 14 with live steam.

This structure is known per se from the prior art.

According to the invention, a device 15 for the continuous discharge of steam is arranged in the blowpipe, which is a cyclone which separates excess steam, which is not required for transporting the fibers, by centrifugal force from the pulp-steam mixture. This excess steam is passed through a dip tube 16 of the cyclone 15 and further through a

Steam line 17 discharged. This steam line 17 is subsequently divided and the excess steam can now be supplied to the boiler 4 either via a first branch line 18 to the pre-dam 1 or a second branch line 19. Since the vapor pressure in the second branch line 19 will generally not be large enough, a thermal vapor compressor 20 is still arranged in this.

The cyclone 15 is in open communication with the continuing blowline 6, so that it does not come to the outlet of the cyclone 15 in the blowpipe 6 to a denser or clumping of the fibers. This is possible because only part of the vapor is removed by the cyclone and the remaining portion of the steam is used to convey the fibers further, so that the cyclone does not have to be completely sealed against the subsequent line 6.

As a throttle for the pressure control, a further blowing valve 21 is arranged in the blowing line 6 in the flow direction after the cyclone 15 and then a pressure measuring device 22, with which the pressure in the blowing line 6 is measured. Depending on the continuously measured pressure, either a valve 23 in the first branch line 18 or a valve 24 in the second branch line 19 is opened via the control of the system if necessary. It is also possible in principle to open both valves 23, 24 simultaneously or partially in order to supply both the pre-damper 1 and the cooker 4 with excess steam. In principle, it would also be possible to connect the steam line 17 with a valve installed therein directly only to the pre-damper 1, wherein the withdrawn excess steam could then just be supplied exclusively to the pre-damper 1.

In front of the dryer 7, a fiber switch 25 is arranged in the blowpipe 6, with which the pulp-steam flow can be passed either to the dryer 7 or to a start-cyclone 26 until the system has reached a stable operating condition.

In normal operation, the blow valve 8 is fully open. The pulp-steam mixture is passed through the cyclone 15 and the fiber switch 25 is set in the direction of the dryer 7. The valves 23, 24 are either open or closed depending on the pressure in the blowpipe 6 measured by the pressure measuring device 22, whereby either the suction pipe of the thermal vapor compressor 20 is supplied with steam or the steam is conducted into the pre-steaming vessel 1.

When the separated vapor is passed via the line 19 into the suction pipe of the vapor compressor 20, this steam can be brought with live steam via a line 27 to the vapor pressure of the digester 4. The steam supply for the cooker 4 is regulated by the pressure in the cooker. If the steam supplied by the thermal vapor compressor 20 is insufficient, live steam is supplied directly via the line 13.

If the separated steam is passed directly into the pre-steaming vessel 1 and the amount of steam recovered is not sufficient to adjust the temperature, live steam can be added via line 12 into the pre-steaming vessel 1. If the amount of steam withdrawn through the cyclone 15 and supplied via the line 18 is not required in its entirety, it will automatically come to the deposition of the steam via the pre-damping tank 1.

The the pulp-steam mixture through the cyclone 15 to The amount of steam taken depends, on the one hand, on the minimum quantity of steam required for the further transport or the further processing of the pulp-steam mixture and, on the other hand, on the fact that clumping of the fibers in the cyclone 15 or thereafter beyond an admissible extent should be avoided, and can take place via the valves 23, 24 and the blowing valve 21 are set. The amount of steam taken off is preferably at least 2% by weight, more preferably at least 10% by weight of steam and preferably at most 70% by weight, particularly preferably at most 20% by weight. At these proportions of withdrawn and returned to the system steam is on the one hand a significant energy savings given, on the other hand, it is ensured that the further promotion of the fibers after the cyclone 15 still works reliably. For example, the fibrous-steam mixture before the cyclone contains 28% by weight of steam and, after the cyclone, 14% by weight of steam. The difference of 14% by weight of extracted steam can be supplied to the pre-steaming container 1 and / or the digester 4 as described.

To start the system, the blow valve 8 is first closed and the system is heated to operating temperature. Subsequently, the blow valve 8 after the refiner 9 in part and the blow valve 21 is fully opened after the cyclone 15 and the fiber-optic 25 in the direction of start cyclone 26. After reaching the desired fiber quality, the fiber switch 25 is switched in the direction of dryer 7. Then, the blowing valve 21 is slowly closed after the cyclone 15 until the pressure in the cyclone 15 increases. Then the blow valve 8 is slowly opened completely after the refiner 9 and the opening of the blow valve 21 is readjusted. Finally, one of the two valves 23, 24 is slowly opened after the dip tube 16 and the control is activated.

To stop the system, the flow rate is reduced and the open valve (s) 23, 24 closed. The blowing valve 8 behind the refiner 9 is then throttled and placed the fiber-optic 25 towards the start-cyclone 26. The system can then be driven down completely.

Claims (11)

1. Plant for processing fibre materials with a pre-steamer (1), a digester (4), and a refiner (9), which is connected via a blow line (6) to a dryer (7), where a device (15) for continuous discharge of part of the steam is arranged in the blow line (6) and where a discharge opening (16) for steam from the device (15) is connected via a steam line (17, 18, 19) to the pre-steamer (1) and/or the digester (4), where the device (15) is connected directly to the blow-line (6), which continues to run in the direction of flow, characterized in that the device (15) is a cyclone and the discharge opening (16) is formed by an immersion tube.
2. Plant according to Claim 1, characterized in that a pressure measuring device (22) is arranged in the blow line (6) in flow direction downstream of the device (15).
3. Plant according to Claim 2, characterized in that at least one valve (23, 24), which is connected in the control equipment to the pressure measuring device (22), is arranged in the steam line (17).
4. Plant according to Claim 2 or 3, characterized in that the steam line (17) splits into a first branch line (18) and a second branch line (19), that the first branch line (18) is connected to the pre-steamer (1) and the second branch line to the digester (4), and that a valve (23, 24), which is connected in the control equipment to the pressure measuring device (22), is arranged in each branch line (18, 19).
5. Plant according to Claim 4, characterized in that a thermal steam compressor (20) is arranged in the second branch line (19).
6. Plant according to one of Claims 2 to 5, characterized in that a throttle valve (21) is arranged in the blow line (6) downstream of the device (15) and upstream of the pressure measuring device (22).
7. Method for processing fibre material in which raw material to be processed, e.g. wood chips, are fed consecutively to a pre-steamer (1), a digester (4), a refiner (9), and through a blow line (6) to a dryer (7), where part of the steam is removed continuously from the mixture of fibres and steam downstream of the refiner (9) and upstream of the dryer (7) in a device (15) and the steam removed is fed to the pre-steamer (1) and/or the digester (4), where the mixture of fibres and steam from the device (15) is conveyed onwards continuously through a direct connection to the blow line (6), characterized in that steam is removed continuously from the mixture of fibres and steam by means of centrifugal force, e.g. in a cyclone.
8. Method according to Claim 7, characterized in that the pressure in the blow line (6) is measured after steam has been removed and that the steam removed is fed to the pre-steamer (1) and/or the digester (4), depending on the pressure measured.
9. Method according to one of Claims 7 or 8, characterized in that the pressure of the steam removed is increased before it is fed to the digester (4).
10. Method according to one of Claims 7 to 9, characterized in that at least 2% by wt., preferably at least 10% by wt., is removed from the mixture of fibres and steam.
11. Method according to one of Claims 7 to 10, characterized in that a maximum of 70% by wt., preferably a maximum of 20% by wt., is removed from the mixture of fibres and steam.

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