FI88810C - FOERFARANDE FOER REGLERING AV MALNINGSVERKAN HOS EN RAFFINOER SAMT ETT MALSKAER - Google Patents

Abstract

The invention concerns a method for controlling the refining results imparted on stock in refiners used in the pulp and paper industry, said refiner performing refining between opposed refiner blades (1), of which at least one is rotary, and said blades having protruding blade edges (2, 3) on their surface. The method according to the invention is implemented by arranging the cutting length of the refiner blades (1) to be alterable by moving one or a multitude of the blade edges (3) with respect to the other blade edges (2). <IMAGE>

Description

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METHOD OF ADJUSTING THE GRINDING RESULT OF A GRINDER AND A FLOUR PRICE - FÖRFARANDE FÖR REGLERING AV MALNINGSVERKAN HOS EN RAFFINÖR SAMT ETT MALSKÄR

The present invention relates to a method for adjusting the grinding result of pulp mills used in the pulp and paper industry, in which the grinder is ground between opposite blades, at least 10 of which are rotatable, and in which the blades have steel edges projecting from their surface. In addition, the invention relates to a grinding blade implementing the method.

At present, in the paper and pulp industry, either disc or cone blade type grinders are used to grind pulp pulp. Regardless of the type of grinder, the dimensioning of grinding is based on the need to change the properties of the fibers in the pulp pulp to be ground (different wood grades and their fiber properties, as well as the final products to be manufactured). The production volume itself (tons / day) influences the choice of refiner size.

The grinding parameters selected for each pulp also depend on the pulping method; mechanical softwood and hardwood pulps, chemical softwood and hardwood pulps, combinations of the above and various recovered paper pulps. According to the state of the art, the amount of grinding given to each different type of fiber (changing the properties of the fibers) is achieved by transferring the energy provided by the grinder motor through a rotating shaft through rotor and stator blades inside the grinder to the pulp and individual fibers. The required specific energy consumption (MJ / tonne) is different for different pulp grades.

35 As the required energy is transferred to the fiber pulp through the grinding blades, the properties of the blades (width of the edges, width and depth of the grooves, angles and number of edges of the edges, and metallurgical properties) are very important.

In general, in order to obtain a grinding result, a single edge load (Ws / m) is also determined. The specific edge load (OSK) is selected on the basis of the effective energy (pe) / grinding speed (n) and the cutting blade cutting length (L) of the grinder according to the following formula: 10

OSK = Pe / (n * Lg), where Ls - Zr * Zst * 1J

15 = number of edges of the rotor blades, Z. = number of edges of stator blades, st 1 = meeting length of steel edges.

The OSK to be selected depends on the length of the fibers in the fiber stock, the thickness of the fiber wall and the need for the desired change in the leaching properties of the fibers.

The so-called refiners after determining the fixed parameters (installed engine power (kW) and speed (n)), changing the effective energy used for grinding is the only method that modifies the grinding result without modifying the downtime of the refiner. Changing the grinding power changes both the specific energy consumption (load change) and the specific edge load.

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As the production volume of the mill increases, the specific energy consumption can be kept constant by increasing the load of the refiners, but at the same time the specific edge load is increased, whereby the properties of the fibers change substantially after grinding.

35 The specific edge load can then be kept constant by changing the rotational speed of the motor and / or by changing the blades inside the refiners and / or by increasing the number of refiners. That is, in prior art refiners and milling systems, as production volumes and / or fiber quality change, the only way to maintain a consistent milling result is to change the sharpening of the mills, which requires the mills to be stopped and the pipe sections generally removed.

The object of the present invention is to provide a method for improving the grinding result of pulp mill 10 used in the pulp and paper industry, which method does not have the above-mentioned drawbacks, and which method is able to maintain a uniform grinding result as production volume and / or fiber quality changes.

The method according to the invention is characterized in that the cutting length of the refining blades is changed by moving one or more steel edges relative to the other steel edges.

A preferred embodiment of the method according to the invention is characterized in that the cutting length of the grinding blades is changed by raising or lowering one or more steel edges in the stator and / or rotor blade in a direction perpendicular to the blade surface.

Another preferred embodiment of the method according to the invention is characterized in that the cutting length of the refining blades is changed by moving one or more steel edges in the rotor and / or stator blade substantially transversely to the other steel edges.

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Another preferred embodiment of the method according to the invention is characterized in that the angle of one or more steel edges in the rotor and / or stator blade is changed in order to adjust the grinding result.

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Yet another preferred embodiment of the method according to the invention is characterized in that the cutting length of the refining blades is changed without substantially interrupting production while the engine of the refining is running.

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A refining blade for use in the paper and cellulose industry using the method according to the invention, in which the refining blade has a plurality of steel projecting blade edges, is characterized in that at least one steel edge is movably mounted relative to the other steel edges.

A preferred embodiment of the refining blade according to the invention is characterized in that at least one steel edge is mounted for raising and lowering in a direction perpendicular to the surface of the refining blade.

Another preferred embodiment of the refining blade according to the invention is characterized in that the at least one steel edge is mounted so as to be movable transversely to the other steel edges of the refining blade.

Yet another preferred embodiment of the grinding blade according to the invention is characterized in that every other blade edge is fixed and every other movable.

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According to the invention, the specific energy consumption can be varied according to the production requirements by keeping the specific edge load constant. In the above formula, increasing the effective grinding energy increases the specific edge load unless the rotational speed (n) and / or the cutting length (Lg) of the blade edges are increased. Correspondingly, as the effective grinding power decreases. In practice, changing the rotational speed (n) requires either the use of a DC motor or a special frequency converter, in which case the problem is insufficient grinding torque and the change in the flow characteristics of the refiner caused by the change in rotational speed,

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With the method according to the invention, the cutting length of the refining blades can be changed without changing the blades inside the refining machines. In practice, the change in the cutting length takes place by moving one or more edges in the rotor and / or stator blades, whereby the cutting length of the sharpening changes.

In the following, the structure of the grinding blade according to the invention will be explained by means of preferred exemplary embodiments with reference to the accompanying drawing, in which

Figure 1 shows a part of the grinding steel seen from above.

Fig. 2 shows a section 15 along the line A-A in Fig. 1 according to an embodiment.

Figure 3 shows the same as Figure 2, but in a different position of the movable steel edge.

Fig. 4 shows a section along the line A-A in Fig. 1 according to another embodiment.

Figure 5 shows the same as Figure 4, but in a different position of the movable steel edge.

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Figure 6 shows a part of the grinding steel seen from above.

Fig. 7 shows a section along the line B-B in Fig. 6.

Fig. 8 shows a section according to another embodiment along the line A-A in Fig. 1.

Figure 9 shows the effect of the angle of contact of the steel edges on the contact area between them.

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Figure 1 shows a grinding blade 1 provided with parallel steel edges 2 projecting from the grinding steel. As mentioned earlier, conical grinders or disc grinders are most commonly used for grinding. For the purposes of the present invention, the type of refiner is irrelevant.

Figure 2 shows a section along the line A-A in Figure 1. It can be seen that a raised and lowered steel edge 3 is arranged between the fixed steel edges 2. For example, hydraulic cylinders (not shown in the figures) can be used to move the steel edge 0. In the situation of Figure 2, the movable steel edge is in its lower position and in the situation of Figure 3, respectively, in its upper position. It is advantageous, for example, to arrange every other edge fixed and every other movable.

Figures 4 and 5 show an embodiment in which the movable steel edge 3 in its upper position substantially fills the gap between the fixed steel edges. The principle of movement of the steel edge in this embodiment may be similar to the above.

It is further possible that the steel edges are moved in a direction transverse to the fixed steel edges, as shown by the arrows in Figures 6 and 7. In principle, it is also conceivable that the same steel edge can be moved both vertically and laterally. In addition, it is possible to adjust the grinding result as shown in Fig. 8 so that the angle of the steel edges is changed, whereby the contact area of the edges of the rotor and stator blades changes. This is illustrated in more detail in Figure 9, where L1 denotes the width of the steel edge, A1 and A2 the meeting areas and a1 and a2 the angles between the steel edges. It can be seen from Figure 9 that the smaller the angle between the steel edges, the larger their contact area.

Claims (10)

A method for adjusting the grinding result of pulp pulp mills used in the pulp and paper industry, in which the mill is carried out between opposite milling blades (1), at least one of which is rotatable, and in which the blades have steel edges (2, 3) projecting from their surface, characterized in , that the cutting length of the grinding blades (1) is changed by moving one or more steel edges (3) relative to the other steel edges (2). Method according to Claim 1, characterized in that the cutting length of the grinding blades (1) is changed by raising or lowering one or more steel edges (3) in the stator and / or rotor blade in a direction perpendicular to the blade surface. Method according to Claim 1, characterized in that the cutting length of the refining blades (1) is changed by moving one or more steel edges (3) in the rotor and / or stator blade substantially transversely to the other steel edges (2). Method according to Claim 1, characterized in that the angle of one or more steel edges in the rotor and / or stator blade is changed in order to adjust the grinding result. Method according to one of Claims 1 to 4, characterized in that the cutting length of the refining blades (1) is changed without substantially interrupting production while the refiner motor is running. 6. Grinding blade for grinding in the paper and pulp industry, where the grinding blade (1) has several Grinder blade according to Claim 6, characterized in that at least one steel edge (3) is mounted for raising and lowering in a direction perpendicular to the surface of the grinder blade (1). 7 co pin 1. u O I <j Grinder blade according to Claim 6, characterized in that the at least one steel edge (3) is mounted so as to be movable transversely to the other steel edges (2) of the grinder blade (1). Grinding blade according to Claim 6, characterized in that the angle of the at least one steel edge (3) is mounted for movement relative to the other steel edges (2) of the grinding blade (1). Grinding blade according to one of Claims 5 to 9, characterized in that every other steel edge (2) is fixed and every other (3) movable. P881C projecting steel edges (2, 3), characterized in that the at least one steel edge (3) is movably mounted relative to the other blade edges (2). 9 R881C