DE102008026677B3 - Drying lignocellulose fibers, for fiberboard production, has a separator to detach fibers from a steam flow for drying with recovered steam for heating the wood chip start material - Google Patents

Abstract

To dry lignocellulose fibers, for the production of medium- or high-density fiberboards, the start material is digested to be fed through a blower tube (8) as a flow of fibers in steam to a steam separation stage (15) and through a blower tube (16) to the dryer. At the separator, the steam/fiber flow is passed to the surface of a rotating drum sieve (18) where the fibers are caught. A scraper (19) detaches the fibers to be passed on to the dryer.

Description

The The invention relates to a process for drying lignocellulose-containing Fibers used for the production of moldings, in particular MDF or HDF plates are provided, wet-digested from a starting material and via steam as a steam-fiber stream over a Blowpipe fed to a dryer be, in front of the dryer in a vapor separator at least a portion of the water vapor is separated from the fibers, as well as a Steam separator for use in this process.

The method and the vapor separator are for example from DE 10 2006 012 521 B3 known.

at In the production of MDF or HDF boards, the fibers are in one wet refiner process and recovered by means of transport steam transported in the direction of the dryer. Be in the dryer dried the fibers to the moisture required for further processing. The transport steam falls Therefore, on the one hand in the dryer as a load and on the other hand has a filter and fireplace consuming be disposed of. In the blowpipe between the exit of the refiner and the entrance to the dryer are temperatures of about 150 ° C to 270 ° C.

Around to recover at least part of the steam, which is then added the fiber preparation can be used, thereby simultaneously reduces the energy required to dry the fibers in the dryer can be, is provided in the known method, a partial area the wall of the blowpipe porous to design, so that water vapor can escape.

It are also heat recovery systems by means of a pressure cyclone (swaped di-scharger) or by means of a pressure cylinder (board heat recovery system) known. These systems are in "Deppe / Ernst, MDF medium density fiberboard, page 54 "described in detail.

In the DE 37 28 123 A2 Heat recovery systems are explained, for example, operate on the principle of gravity or centrifugal force and / or are constructed of filters or mechanical separators. The separated water vapor is reintroduced into the process for reasons of saving energy and expediently used for heating and soaking the wood chips still to be fibrillated.

The WO 2004/106 632 A1 describes a vapor separator, which may be designed as a non-pressurized cyclone, as a pressure cylinder or as a mechanical separator.

It has been shown to be a technical implementation with the help of known Heat recovery systems not the hoped-for economic benefits ensures. The high technical effort required for the realization the known heat recovery systems necessary, leads to a susceptibility the plants. Furthermore The achievable throughput rates are low.

From Based on this problem, the initially described Method be improved and it should also be a vapor separator for use in the method.

to Troubleshooting distinguishes the generic method characterized in that the steam-fiber stream on a rotatable Strainer is passed and the water vapor passes through the sieve Direction steam discharge flows, while the Fibers on the surface of the rotating screen and from there by means of a Scraper scraped off and then fed to a fiber discharge. The flowing through the sieve Water vapor can be used to treat the wood chips, the starting material for the Fibers are to be used. Because by that, by the previously deposited Transport steam the dryer load is reduced, the dryer temperature can be lowered. Especially with high quality chemical components wetted fibers reduces their amount used, because the temperature-dependent chemical Crosslinking reaction is lower.

Preferably the rotary screen is driven. For this purpose, an electric motor be provided. The rotation of the screen can also be done by means of the fiber vapor fiber stream.

• a) ein in zwei Kammern unterteiltes geschlossenes Gehäuse mit
• b) einem Blasrohreingang,
• c) einer Dampfableitung,
• d) einer Faserableitung,
• e) einem drehbar gelagerten Sieb und
• f) einem auf die Oberfläche des Siebes einwirkenden Abschaber, wobei
• g) die Kammern nur über das Sieb miteinander in Verbindung stehen und
• h) die erste Kammer die Dampfableitung aufweist und
• i) die zweite Kammer die Faserableitung aufweist.

A vapor separator for use in the method is characterized by

• a) a divided into two chambers closed housing with
• b) a blower pipe entrance,
• c) a vapor discharge,
• d) a fiber discharge,
• e) a rotatably mounted sieve and
• f) a scraper acting on the surface of the screen, wherein
• g) the chambers communicate with each other only through the sieve and
• h) the first chamber has the vapor discharge and
• i) the second chamber has the fiber discharge.

The steam-fiber stream is directed directly onto the rotatable screen. The steam through the sieve flows and the fibers are collected at the surface. As the screen rotates, the fibers adhering to the top are conveyed towards the scraper and, upon further rotation of the screen, are scraped off the surface thereof to fall in the direction of fiber discharge from where they are fed to the dryer.

The Sieve is preferably a screen drum and the scraper is particular Stationarily arranged in the second chamber and abuts the sieve.

The Sieve can be drivable by an external drive or by the Steam-fiber power to be driven. In the latter case points the sieve in particular preferably peripherally a plurality of Shovels on, which are arranged so that the impinging water-fiber stream set the sieve in rotation. The holes of the perforation of the sieve preferably have a diameter of 0.1 to 3 mm.

To the pressure-tight separation in the direction of the dryer can in the second Chamber before the fiber discharge a knife lock be arranged.

With Help a drawing to an embodiment of the invention below to be discribed. It shows:

1 A flow chart of fiber production and drying;

2 - The schematic view of a plant for digestion and processing of lignocellulosic fibers;

3 - The schematic sectional view of a vapor separator.

For the production of lignocellulosic fibers is present in the form of wood chips wood source material 2 in a bunker 3 warmed up and by means of steam, which over the line 4 is fed, moistened. The warmed and moistened starting material 2 is via a plug screw 5 a pressurized stove 6 fed, is introduced into the supersaturated water vapor. Due to the vapor pressure softening of the wood occurs. For this purpose, saturated steam with a temperature of 160 ° to 180 ° and a pressure of 6-10 bar can be used. The residence time of the wood chips in the cooker 6 is 3 to 6 minutes. Via a discharge screw 12 and one of an electric motor 1 driven stuffing screw 18 The softened wood chips get into the refiner 7 where she frayed wet and then into a blowpipe 8th be delivered. To singulate the fiber is here before the cooker 6 built-up pressure relaxed, so that, in the blowpipe 8th a steam-fiber stream flows. In a Beleimstation not shown, the fibers in the blowpipe 8th glued by spraying with a binder. The glued fibers get into the dryer with the steam 11 in which they are previously in the heat exchanger 9 warmed air can be adjusted to a desired fiber moisture. Subsequently, the superfluous air-water vapor mixture in a cyclone separator 13 deposited and the fibers enter a fiber container 14 from which they are further processed by being pressed in a press under temperature and pressure to a shaped body, in particular a HDF or MDF board.

To reduce the dryer performance, the blowpipe leads 8th in front of the dryer 11 in a steam separator 15 made of a pressure-tight housing 24 exists in which two chambers 21 . 22 are formed. In the area of the connection of the blowpipe 8th is in the case 24 a sieve drum 18 rotatably mounted. The sieve drum 18 is to the housing 24 over the scraper 19 and the wall 20 sealed together with the sieve drum 18 as separation of the chambers 21 . 22 are provided. The chambers 21 . 22 stand over the sieve drum 18 in contact with each other atmospherically. The holes of the perforation of the sieve drum 18 have a diameter of 0.1 to 3 mm. The first chamber 21 is with a steam discharge 17 provided, the second chamber 22 has a fiber discharge 16 on. At the bottom of the chamber 22 is a knife lock 23 intended. The fiber derivation 16 leads to the dryer 11 , the steam discharge 17 back to the bunker 3 ,

The in the blowpipe 8th supplied steam-fiber stream meets in the vapor separator 15 on the rotatably mounted screening drum 18 , The water vapor flows through the jacket of the sieve drum 18 provided holes in the chamber 21 , The openings in the sieve drum 18 are so small that the fibers can not pass through, but on the surface of the sieve drum 18 be intercepted. The circumference of the sieve drum 18 has blades (not shown) which are arranged so that the water vapor stream impinging on them is the sieve drum 18 set in rotation. This causes the fibers trapped on the surface to rotate counterclockwise in the direction of the scraper 19 promoted, which scrapes off them, so that due to gravity through the knife lock 23 through into the fiber discharge 16 reach. From here they become the dryer 11 fed. In the measuring lock 23 For example, both the amount and the moisture content of the fibers can be determined to determine the temperature in the dryer in the subsequent process 11 according to the determined To regulate measured data. The knife lock 23 serves for pressure-tight separation in the direction of the dryer 11 , The one in the chamber 21 incoming steam is via the steam discharge 17 back to the bunker 3 promoted.

The Sieve drum can also over an electric motor driven foreign, which is not shown here is.

1

electric motor

2

Chips / starting material / wood chips

3

bunker

4

management

5

stuffing screw

6

Stove

7

refiner

8th

blowpipe

9

heat exchangers

11

dryer

13

cyclone

14

fiber bunker

15

steam separator

16

fiber derivation

17

steam discharge

18

Sieve / screen drum

19

scraper

20

wall

21

chamber

22

chamber

23

Knife sheath

24

casing

Claims (11)

Process for drying lignocellulose-containing fibers, which are intended for the production of moldings, in particular MDF or HDF boards, from a starting material ( 2 ) wet-processed and by means of steam as steam-fiber stream via a blowpipe ( 8th . 16 ) a dryer ( 11 ), wherein in front of the dryer ( 11 ) in a vapor separator ( 15 ) at least part of the water vapor is separated from the fibers, characterized in that the steam-fiber stream is directed onto a rotatable sieve ( 18 ) and the water vapor is passed through the sieve ( 18 ) in the direction of steam discharge ( 17 ) flows while the fibers on the surface of the rotating screen ( 18 ), from there by means of a scraper ( 19 ) and then a fiber discharge ( 16 ). Method according to claim 1, characterized in that the rotatable sieve ( 18 ) is driven. Method according to claim 1, characterized in that the rotation of the wire ( 18 ) is initiated by means of the steam-fiber stream. A vapor separator for use in the method according to claim 1, characterized by a) one in two chambers ( 21 . 22 ) closed housing ( 24 ) with b) a blower pipe entrance ( 8th ), c) a vapor discharge ( 17 ), d) a fiber derivation ( 16 ), e) a rotatably mounted sieve ( 18 ) and f) one on the surface of the screen ( 18 ) acting scraper ( 19 ), where g) the chambers ( 21 . 22 ) only over the sieve ( 18 ), h) the first chamber ( 21 ) the steam discharge ( 17 ) and i) the second chamber ( 22 ) the fiber derivation ( 16 ) having. Vapor separator according to claim 4, characterized in that the sieve ( 18 ) is a sieve drum. Steam separator according to claim 4 or 5, characterized in that the scraper ( 19 ) stationary in the housing ( 24 ) and on the sieve ( 18 ) is present. Vapor separator according to one of claims 4 to 6, characterized in that the sieve ( 18 ) is drivable by an external drive. Steam separator according to one or more of claims 4 to 7, characterized in that the blowpipe ( 8th ) into the second chamber ( 22 ) opens. Steam separator according to claim 4 or 5, characterized in that the sieve ( 18 ) has a plurality of blades, which are arranged such that the impinging steam-fiber stream, the sieve ( 18 ) rotated. Vapor separator according to one or more of claims 4 to 9, characterized in that in the second chamber ( 22 ) before the fiber discharge ( 16 ) a knife lock ( 23 ) is arranged. Vapor separator according to claim 4 or 5, characterized in that the holes of the perforation of the sieve ( 18 ) have a diameter of 0.1 to 3 mm.