FI74999C - Methods for the extraction of high quality steam when refining fiber material. - Google Patents

Description

riTSS ^ n ANNOUNCEMENT π / iqqq [BJ (11) UTLÄQQNINGSSKRIFT 74 99 9 (51) Kv.lk.Vlnt.CI4 D 21 B 1/12

SUOMI FINLAND

(FI) (21) Patent application - Patentansökning 802603 (22) Application date - Ansökningsdag 19 · θ8.8θ

National Board of Patents and Registration (23) Start Date-Giitighetsdag 19.08.80

Patent-och registerstyrelsen (41) Became public-Biivit offentiig 23.02.8l (44) Date of dispatch and publication: 31 .12.87

Ansökan utlagd och utl.skriften publicerad (86) Kv application - Int. ansökan (32) (33) (31) Privilege requested-Begärd priority 22.08.79 Sweden-Sverige (SE) 7907012-4 (71) Sunds Defibrator AB, Sundsvall, Sweden-Sverige (SE) (72) Agne Torvald Mattsson, Enköping , Sweden-Sweden (SE) (74) Berggren Oy Ab (54) Method for the recovery of valuable steam in the grinding of fibrous material -Sätt för utvinning av högvärdig änga vid raffinering av fibermaterial

The present invention relates to a method and apparatus for recovering valuable steam in the grinding of fibrous material.

The overpressure of the steam in the refiner is usually used to transport the ground fibrous material, allowing the steam to expand to atmospheric pressure. The steam is often allowed to flow out into the outside air at the end of the transport work, which means considerable energy loss. Although steam is sometimes recovered after the separator, due to its lower pressure and reduced temperature, it is a less valuable source of energy than steam in a refiner.

The object of the invention is to provide a method and an apparatus for recovering valuable steam in the grinding of a fibrous material, in which the valuable steam formed during the grinding is recovered. This is achieved by giving the method and the device, respectively, the features set out in the following claims. In a preferred embodiment, the steam is returned via a return line to the grinding chamber and / or the drop space to ensure the output of the ground material to the conveying device. This eliminates the need to supply water to clean the walls of the drop chamber and provides a powdered material with a higher dry matter content of 2 74999, without the need to lower the temperature of the steam from the refiner and the ground material. In another preferred embodiment, the steam is cleaned inside the main line with a cleaning device connected before the outlet valve. In a particularly preferred embodiment, the flow through the cleaning device is kept substantially constant.

Some embodiments of the invention will become apparent from the following detailed description of the drawings, in which Figure 1 schematically shows an apparatus for recovering valuable steam according to the invention, Figure 2 shows a section through a refiner, Figure 3 shows a conventional grinding plant, Figure 4 shows a plant according to the invention. 5 shows another known grinding plant, and Fig. 6 shows the plant according to Fig. 5 implemented according to the invention.

The purpose of the treatment of the fibrous material is to achieve the desired pulp properties in a controllable manner by means of a controllable adjustment of the various process parameters.

For example, the grinding energy fed to the cellulosic fibers varies between 300-2000 kWh / tonne for different pulp types and sometimes more depending on the desired pulp types and in addition the process steam pressure and temperature with or without preheating at varying cycles by treating the fed fiber with such chemicals.

The pattern of the refining members of the refiner and the distance between the refining members are varied, whereby the amount of material and the delay time of a certain amount of material in the refining zone also vary.

The input grinding power is largely converted to frictional heat and generates an amount of friction vapor that is approximately proportional to the input grinding energy. The friction steam generated in the grinding zone causes the ground material to

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3 74999 output power is output from the grinding zone.

This conveying power is becoming more and more noticeable in larger machines and in the production of pulp types with a high need for grinding power.

In order to apply the desired grinding power to the fibrous material, e.g. reduces the distance between the refining members of the refiner. In this case, however, the probability of the fibers shearing, i.e. their breaking, increases, which leads to poorer strength values in the final product.

Another way to affect the power transfer, between the expanding vapor which gives rise to the refiner, the refining can be achieved by fitting a pressure difference between the inlet and the refining outlet side.

When the pressure difference is larger, whereby a higher pressure prevails on the outlet side, the expansion of the generated friction steam remains smaller. Such an increased pressure difference results in a lower speed and a longer lag time of the ground material in the grinder. This makes it possible to increase the distance between the grinding members and thus to obtain a ground material which is more defibered due to the effect of the fiber against the fiber, whereby the properties of the pulp are improved.

According to the present invention is designed to exploit these advantageous results obtained by the pressure difference between the inlet and the refining outlet side, and in this way be recovered by steam having a higher pressure.

The fibrous material, preferably preheated, is fed at a suitable rate down to a refiner 1, which may be a single disc refiner, but which is preferably a twin disc refiner with counter-rotating refiner discs 18 (Figure 2). The chamber 17 surrounding the refiner is made to withstand strong overpressure. The ground material and the generated steam exit the chamber 17 through an opening 19 located above the drop space 2. The drop space 2 terminates in a conveying device 3 which includes a reversible screw 24. The screw 24 feeds the fibrous material to the right in Fig. 1 to an outlet device 4 of such a construction that ground 74999 4 material can be discharged without or with limited steam removal. steam pressure.

In the left part of the conveying device, steam is sucked out via the suction device 5 located in Fig. 1, so that only a small amount of ground material follows with the steam. The device 5 can also, in some cases, suck off steam on both sides of the downcomer 2. The exhaust device 5 preferably has a large inlet opening compared to the outlet opening terminating in the line 6. The sucked steam is conveyed to a cleaning device 7, e.g. a cyclone, where the pulverized material accompanying the steam is separated, for sufficient purification of the steam generated by friction. The ground material is suitably returned to the conveying device 3 next to the discharge device 4.

The cleaning device 7 is suitably provided with a device 7A, e.g. a screw, in order to avoid deposits or blockages, so that a safe outlet is obtained. The cleaning device is adapted to the purity requirements set for the economical use of the generated friction steam in the second process operation. In addition to the mechanical cleaning of the accompanying fibers, steam cleaning can also be dry cleaning.

The pressure required to transport the steam through the cleaning device 7 is obtained by a connected pressure sensor 8. The pressure sensor 8 is connected either before or after the cleaning device 7. Steam from the cleaning device 7 is further led, possibly over the pressure sensor 8, to the valve 12 of the main line 6. The return line 9 containing the valve 14 leaves the main line 6 before the valve 12 and preferably after the pressure sensor 8 and the cleaning device 7. Through the return line 9, the steam is returned to the transport line 3 through the grinding chamber 17 and / or the drop space 2 of the refiner. The drop space is suitably shaped so that the steam supplied through the openings 10 prevents this space from becoming clogged. This avoids the use of any other tool for this purpose. The pressure and temperature of the system are determined by the control of the valve 12, whereby the valve is suitably controlled by pressure automation for the controlled removal of the kitt steam generated.

Il 74999 5 The advantage of a transport circuit with steam recovery is that the steam side has the possibility of maintaining a constant flow and thus a good cleaning of the circulating steam even when the load on the grinding members varies. Such a varying load causes the amount of friction steam generated to also vary. Most cleaning devices 7 are designed in such a way that the varying flow impairs the cleaning performance.

Also connected to the system is a pressure controlled fresh steam line 16 which is used to supply steam during start-up and to maintain the desired pressure in the system when process production is uneven and the amount of frictional heat generated is insufficient.

In the special case of the invention, where the process is carried out with steady production and thus generates an approximately constant amount of steam, it is possible to dissipate the generated friction steam, whereby the valve 14 is closed and the pressure sensor is bypassed. However, this results in a decrease in steam pressure and economic value due to the flow resistance of the system up to the valve 12.

In order to avoid production disruption during malfunction of a pressurized system, e.g. 3.

The friction steam generated in the production of the non-pressurized system is sucked out by a closed valve 14. In connection with the openings 14, the drop space 2 can be provided with a device (not shown) for cleaning the walls of the drop space 2. The valve 13 and the line 15 are provided with a device (not shown) or a rinsing water inlet to ensure the supply of ground material via the line 15. In production using a pressurized system, the valve 13 is, of course, closed.

The invention is not limited to its embodiment shown in Fig. 1, but its structure can be modified within the framework of the basic principle, whereby, for example, the arrangement of the outlet 6 74999 of the separated substance and the pressure relief can be varied. For example, the cleaning device 7 may consist of two separators connected in series.

When several refiners are placed in a production plant, for example the conveying device can be common to a common feeder for several machines.

Figure 3 shows a conventional fibrous material grinding apparatus in which the preheated material is fed to the refiner 44 from the preheater 40 through a cell feeder 41, an expansion tank 42 and a screw feeder 43. The steam generated in the refiner is passed through a screw feeder 42 to an expansion vessel 42 where it is allowed to expand.

Figure 4 shows a plant according to Figure 3 modified in accordance with the invention. The steam generated partially passes directly against the fed fibrous material into the preheater. Due to the high overpressure on the outlet side of the powder heater, some of the steam is compressed inside the preheater. If this amount is not sufficient, part of the steam taken out via the valve 12 can also be led to the preheater. The cell feeder 41 has been removed from the plant according to Figure 4.

Figure 5 shows another conventional plant used for grinding fibrous material. The fibrous material enters the refiner 51 through the preheater 50. From there, the ground material is blown into a cleaning device 52, e.g. a cyclone, where the steam is cleaned. The fibers are fed out through the screw.

Figure 6 shows the plant of Figure 5 modified in accordance with the present invention. The ground material is now removed from the bottom of the grinding chamber, in the same way as in Fig. 1, and is led to the cleaning device 52 via a line connected to the steam outlet and the conveying device 3. The steam separated in the separator 52 is removed through the valve 12. Prior to this valve, a return line is provided to return a portion of the steam to the refining chamber and / or drop space 2 of the refiner. The ground material separated in the cleaning device 52 is led to an outlet device connected to the conveying device 3.

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Claims (5)

7 74999 A method for the artistic extraction of valuable steam in the grinding of a fibrous material, wherein the generated steam and the ground material are removed from a grinding chamber (17) which is pressurized and has a pressure-tight outlet (4) for the ground material, the generated steam being substantially discharged, characterized in that the ground material and the generated steam are discharged from the milling chamber (17) in a drop-down manner (2), that the steam is discharged from the ground material falling aside in the drip tray (2) so that only a small part of the ground material travels with the steam, and the dropped material from the drop1 (2) for further transport to the pressure-tight outlet (4). A method according to claim 1, characterized in that the steam is discharged via an associated suction device (5) with a large inlet opening towards the drop space (2) compared to its inlet opening towards the steam outlet line (6). Method according to Claim 1 or 2, characterized in that the steam is discharged on both sides of the drop space (2). 1. For use in the refining of fibrous materials, including all other fractions and mills (17), for the purpose of refining or for the manufacture of flax products (4) for use in the manufacture of foodstuffs and waste products, kännetecknat av att man liter malgodset och den alstrade Ingan frln malhuset (17) av-gl account to fallrum (2), att man i fallrummet (2) aids Ingan i sidled frln det fallande malgodset , you will be able to play in the world with the help of Ingan, och att man trans-