FR2541329A1 - METHOD AND DEVICE FOR MANUFACTURING WOOD PULP - Google Patents

Abstract

THE INVENTION RELATES TO THE MANUFACTURE OF WOOD PULP. IT IS CHARACTERIZED IN THAT THE DEFIBRATION IS CARRIED OUT IN A CLOSED ENVELOPE 2 WITH SAS 7, 8, FOR THE DELIVERY OF WOOD, AND A CLOSED DUCT 10 FOR THE DISCHARGE OF WOOD PULP, IN ORDER TO BE ABLE TO WORK IN OVERPRESSURE AND AT TEMPERATURES OVER 100C. APPLICATION: CONTINUOUS PRESS AND DEFIBREURS.

Description

The invention relates to a method and a

  device for making wood pulp in a

  grinding wheel against which the wood is pressed, with the supply of water into the grinding zone.

  So far we have made the de-

  wood fibrers, press shredders or continuous shredders

  bare, without pressure In continuous shredders, the wood is fed continuously through the conveyor chains into a feed well; in the press shredders, the wood feed to be defibrated is done by means of charges, via a well, the grinding operation occurring continuously in a press chamber where a pressure shoe pushes the wood against the wheel After ending the defibration stroke, the pressure shoe returns to the starting position, and triggers a pulse

  opening of the well for the wood to be defibrated After the

  filling time, the well is again closed.

  The supply of water into the defibration zone produces a film of water which is necessary for the dissolution of

  However, there is the disadvantage that water is

  porise in part and thus occurs overheating

  wedges and wood burns The wood pulp is thus im-

pure and non-uniform.

  At the base of the present invention is the problem of creating a process for defibrating wood.

  with which one obtains a better and better quality

  This problem is solved according to the invention

  the defibration is carried out under overpressure and at times

  water temperatures of over 1000 C. The production of overpressure, which obviously makes it necessary to perform the grinding operation in

  an enclosure isolated from the outside air, allows work-

  at higher water temperatures.

  that the wood pulp produced was better and more uniform

  In addition, this process requires a lower energy expenditure, due to the softening of the lignin at about 1220.degree. C. The length of long fibers and the breaking length of the wood pulp thus increase.

  An advantageous process according to the invention

  in that the overpressure is 1 to 3 bar, and the temperature

  A device according to the invention, for the implementation of the method consists in a shredder comprising a grinding wheel placed in an envelope, a wood supply well, an advance debois hydraulic or mechanical, a supply of water

  in the defibration zone and a collection tray or chute

  for the wood pulp, placed under the grinding wheel, in that the envelope is formed in a pressure-tight manner

  and is provided with an air supply device under pres-

  in that the supply well is provided with sealed airlock under pressure, and that the evacuation of wood pulp

performs in a closed pipe.

  Because, according to the invention,

  under pressure, it is necessary to build the envelope

  For example, it must be sealed under pressure. The wood to be defibrated must then be sumped by the supply well into the pressure chamber, by means of the charges. The passage of the wood to be defibered in the press chambers of a shredder.

  presses, or in the transport shaft of a shredder

  In the same way, a closed pipe must be attached to the tank or to the tank.

collector chute.

  In an improvement of the invention, it is expected that the locks of the feed well consist of two trays trays arranged one behind the other

  Another feature of the invention

  is that the drawer trays are in corners in the

  In this way, we avoid

  due to the weight of the wood and the pressure chamber may

  be constantly closed tightly.

  It is very advantageous to have a di-

  chip finder upstream of the closed pipe.

  When defibering, it sometimes occurs

  also coarse chips and

  can have a whole length of log These frag-

  could lead to obstructions in driving

  By arranging a chip divider upstream of this closed pipe, we manage to put in small pieces these

  shavings or barks and, therefore, to be able to

wear with the wood paste.

  An embodiment according to the invention of the chip divider is that it comprises a rotating drum provided with several discs placed next to one another, with arrangements of teeth or knives, which cooperates with stators. also equipped

  arrangements of the kind teeth or knives.

  It is then advantageous that the various provisions of the genus teeth or knives are placed relative to each other at staggered angles. This measure allows a long bark not to arrive at the same time in the shredding zone, but in a staggered manner.

  which saves energy and avoids possible obstructions

  An inventive improvement consists in the introduction of a dough circulation tube into the collecting tray or tube. This tube brings wood paste already in the form of a suspension and the mixture to the

freshly formed wood pulp.

  With this additional flow, a higher flow rate is obtained, which avoids thickening and accumulations of chips in the tank. A very advantageous improvement according to the invention of the process consists in that after defibration

  dehumidification of the wood pulp in which

  the obtained water, which is still in overpressure, eet

  brought back into the defibration zone, and the thick wood pulp

  is, immediately afterwards, relaxed to the pressure

  mosphérique. After the grinding operation, it is indeed necessary to bring back to atmospheric pressure the

  obtained wood pulp which is in a concentration zone

  This lock of the wood pulp causes very large amounts of heat to escape from the overpressurized parts of the installation. ON can only recover these amounts of heat with heat recovery methods. relatively large and complicated In addition, steam washing and chemical vapor neutralization are required. Due to the low temperature of the vapors that occur, the heat loss can only be used to preheat the water to C. To maintain the temperature equilibrium in the grinding operation, therefore, 2 to 3 tons of steam per ton of material per hour are required. The thickening according to the invention of the pulp

  of wood is, therefore, intended to lower the need for

  required in the process of manufacturing wood pulp in overpressure. The fact that the wood pulp, which is

  normally at a concentration of material in the water of

  1 to 2.5, is dehumidified before the lowering of

  sion, and that the resulting water, which is still

  pressure, is brought back into the defibration zone, limits the energy requirement of this process. If, for example, the suspension is thickened more than 5% with respect to the dry matter, there is an additional need for fresh steam. is required The condensing that is formed can be fully brought back into the process;

  It is advantageous to bring dehumidification

  cation the paste concentration to more than 5%.

  A device according to the invention for implementing the thickening according to the invention consists in that one provides? in or after the collecting trough or the tank, an endless dehumidification screw whose water diversion tube is connected to a pressurized water tank where a return pipe goes into the defibration zone, and

  whose evacuation pipe goes to a

  The lock arrangement for the thickened wood pulp may be a sluice chamber or a nozzle, or a throttling slot, which is, for example

  formed by two disks facing each other in planes

  and which are movable relative to one another or it can also be carried out by a hydrocyclone arranged

  downstream, where impurities and splinters of wood are separated

  Res. Embodiments of the invention will now be described in greater detail with the aid of the attached drawing, in which: FIG. 1 represents in principle a shredder with two presses under pressure

  FIG. 2 is a section of a two-point shredder

  his; Figure 3 is a sectional view of line III III of Figure 2; Figure 4 is a partial sectional view of a continuous shredder with a pressure-tight lock arrangement according to the invention; FIG. 5 is a representation of the principle of a

  two-press shredder, with a dehumidification plant

edification.

  The shredder as shown in the illustration

  re 1, which is a shredder with two presses, is made in a pressure-tight manner The grinding wheel 1 is in a closed envelope -2 On both sides of the grinding wheel are located

  pressure chambers 3 in each of which are

  has a pressure shoe 4 (Figure 2) This shoe 4 is moved

  5 above the two pressurized chambers 3, there are

  6, equipped with pressure-proof seals, each consisting of

  cun by two trays drawers 7 and 8, for a better

  tightness, the drawers 7 and 8 have a configura-

  corner in the closing direction In order to avoid

  wood wedges, at least two well walls are

  in the corners are formed in an inclined manner in

widening downwards.

  As soon as the pressing operation is completed, the pressure shoe 4 is brought back immediately afterwards, the drawer 8 is opened, and a new load of wood arrives in the pressurized chamber 3 Then the drawer 8 is closed and after the drawer 7 is opened , a new load of wood

goes into "waiting position".

  Below the grinding wheel 1, there is a pulp container 9, hence a pipe 10 upstream of the pipe b

  , a chip divider has been installed which is

  killed by a rotating drum 12 on which several

  13 of these knives 14 cooperate with a stator 15 which has also been fitted with tooth-like arrangements.

  In this way, the large chips or barks are put in

  In the dough tray 9 further opens a circulation tube 17.

  the flow velocity in the tank.

  As can be seen in Figure 1, the

  dough coming out of the closed pipe 10 reaches, by a van-

  There is no pressure reduction 18, a hydrocyclone 19 in the

  which impurities, such as chips or similar fragments, are removed in a material outlet

  coarse 20, while the disaggregated wood pulp is

  taken from the hydrocyclone 19 by a discharge pipe of

  For the heat recovery, the heat

  of wood passes through a heat exchanger 22 before being diverted to the subsequent preparation In this exchanger

  heat 22, water is passed from a pipe

  fresh water 23 and entering immediately into the envelope.

  2 at a temperature of about 1250 ° C. Compressed air is introduced into this casing via a pipe 24. The suspension for the circulating pulp tube 17 can be taken from the material pipe 25 after the heat exchanger. heat 22 (as we have seen in

dotted line).

  The continuous shredder works in a manner similar to that of the two-press shredders shown in FIGS. 1 to 3 As shown in FIG. 4, because of the larger dimensions of the filling well, the drawers 7 'and 8 'in pairs one in

facing each other.

  Figure 5 shows a definition of

  double press, with a dehumidification plant

  The grinding wheel 31 is in a closed envelope 32.

  The pressure of the wood to be defibrated is produced by pressing shoes 34 and 35 The wood is brought by pressure locks 36 and 37 Under the grinding wheel 31 is a dough tray 38-dice a pipe 39 Between the bottom 38 and the pipe 39, a chip divider 40 has been arranged which has been previously described.

  a dehumidification screw 41 o occurs an increase

  concentration of the wood pulp which goes from about 1.5% to more than 5% The thickened wood pulp is immediately introduced by a wood pulp outlet pipe 48 into a pulp collecting vessel 42, while the still pressurized water is diverted by a water intake tube 43 and pump 44 into a pressurized water tank 45 of the water tank

  pressure 45, a return line 46 returns to the

  no defibering o water under pressure is thrown by nozzles 47 on the grinding wheel 41 To lock the drink paste

  represented in this embodiment, four values

  possible laughs ON can pass the thickened dough

  from the dough collecting tank 42 by a hydrocycloid

  ne 49 Overpressure is then used for the function

  The impurity is removed at the tip of the cone in a known manner, while the purified suspension is removed without pressure on the upper side. Instead of a hydrocyclone 49, a nozzle can also be provided.

  or a double airlock 51, or a plate refiner 55.

  To cover the losses of water, it brings in addition to the pressurized water tank 45, downstream water coming from other places, by a pipe 52.

  control of temperature and pressure in the envelope

  In the case of a shredder 32, a steam pipe 53 is used.

  with adjustment arrangement 54.

Claims (5)

  1 Process for the production of wood pulp in a grinding mill, operating under pressure at water temperatures of more than 100 ° C, characterized in that after defibering, a dehumidification of the wood pulp occurs water which is obtained there and which is still under pressure being brought back to the defibration zone and the concentrated wood pulp being immediately relaxed at the pressure atmospheric.   2 Process according to revebdication 1, characterized in that dehumidifies to bring the pulp to a concentration of more than 5% 3 Device for the implementation of the   process according to any one of claims 1 and 2,   characterized in that a dehumidifying worm (41) is provided in or after the collecting trough (38), the water diversion tube (43) of which is connected to a pressurized water tank (45). ) a return pipe (46) goes into the deflection zone and the wood pulp discharge pipe (48) goes to a lock installation (49) 9 (50)   (51) to atmospheric pressure.   4 Device according to the revebdication 3, characterized in that a hydrocyclone (49) is provided as a lock device Device according to claim 3,   characterized in that the fillet pipe (48) leads to   mouth in a dough collecting tank (42) which is provided with a nozzle (50).   Device according to Claim 3,   characterized in that the woodpulp pipe (48) is   in a dough collecting tank (42) which is provided with a double airlock (51).   Apparatus according to claim 3, characterized in that the wood pulp pipe (48) opens into a dough collecting tank (42) which is provided with a plate refiner (55).