RU2761544C1 - Grinding fittings - Google Patents

Abstract

FIELD: grinding.

SUBSTANCE: invention relates to grinding fitting of disk mills and is used in the stock preparatory departments of cellulose and paper industry enterprises at the stage of mass grinding of aqueous suspensions of a high-concentration wood-fibre mass. The fittings include a rotating rotor and a stationary stator disks with working surfaces facing one another, provided with circular blade protrusions alternating with through inter-blade grooves, directed in opposite directions, the cutting edges whereof are made with an eccentricity relative to the centre of the disk, and the angle between the tangents of the cutting edges and the radii from the centre of the disk to the point of tangency increases uniformly from the most possible value - on the input edge of the disk - to the most possible value - at the output, wherein the radius of curvature of the circular cutting edges r₁=0.633∙R, and the centres of curvature are uniformly distributed along a circumference with a radius drawn from the centre of the disk, r₂=0.6∙R, wherein R is the radius of the output circular edge of the disk of the fittings, to ensure grinding of the aqueous suspension with a concentration of the wood-fibre mass of 6 to 15%.

EFFECT: increase in the values of the parameters of speed, power mechanical and hydrodynamic impact on the fibrous semi-finished product in the annular grinding cavity during one pass through said cavity to optimal values.

1 cl, 1 dwg

Description

The invention relates to grinding sets of disk mills and is used in grinding and preparatory workshops, enterprises of the pulp and paper industry, at the stage of mass grinding of aqueous suspensions of high concentration wood fiber pulp.

An analogue of the proposed solution is known, which is a grinding set of a disk mill, including a rotating rotor and stationary stator disks, equipped with alternating through intercutting grooves, rectilinear knives, the cutting edges of which are inclined to the radius of the disk (V.F. Pashinsky, Machines for grinding pulp "," Timber industry ", M., 1972, p. 81, fig. 32).

The disadvantage of the set is the small length of the cutting edges of the straight knives, which is not connected with the impossibility of intensifying the grinding process and with a decrease in its productivity.

The closest to the proposed set in technical essence is a grinding set, including, rotating - rotary and stationary - stator, disks, the working surfaces of which, facing one another, are equipped, alternating with through inter-knife grooves, circular knife protrusions directed in opposite directions , the circular cutting edges of which are made with eccentricity relative to the center of the disc (RU No. 2307883 C1, IPC D21D 1/30, В02С 7/12, declared 3.4.2006, published 10.10.2007, bulletin No. 28).

The advantage of the headset is the effect of increasing, from the input circular edge of the disc to the output, the angle between the tangent to the cutting edge of the unit knife and the radius drawn from the center of the disc to the point of contact.

The disadvantage of the headset is the impossibility of achieving this effect at any value:

- mass concentration;

- radii of curvature of circular cutting edges;

- the radius drawn from the center of the disk of the circle on which the centers of curvature of the circular cutting edges are located.

With a high concentration of an aqueous suspension of wood fiber pulp (6-15%), in all ranges of curvature radii of circular cutting edges and radii, circles on which the centers of curvature of circular cutting edges are located, this disadvantage does not contribute to:

- free passage of the mass through the annular grinding cavity of the headset;

- intensification of the grinding process;

- increasing the productivity of the grinding process. The invention solves the problem of intensification, quality improvement

grinding process and productivity, as well as reducing specific energy consumption when grinding an aqueous suspension of high-concentration wood fiber pulp.

The technical result consists in increasing to the optimum values of the parameters of the speed, power mechanical and hydrodynamic effects on the fibrous semi-finished product in the annular grinding cavity, during one pass through it.

To ensure the specified technical result, in a grinding set, including rotating - rotor and stationary - stator disks with working surfaces facing one another, equipped with, alternating with through inter-knife grooves, circular knife protrusions directed in opposite directions, the circular cutting edges of which made with eccentricity relative to the center of the disc, according to the invention, at a mass concentration (6-15%), the radius of curvature of the circular cutting edges r ₁ = 0.633 R, and the centers of curvature are evenly distributed on a circle with a radius of r ₂ = 0.6 R drawn from the center disk, where R is the radius of the output circular edge of the headset disk.

According to the results of experimental studies, it was revealed that, in comparison with the known solutions, when grinding a mass of high concentration (6-15%), these distinctive features determine:

- the most possible value of the entrance angle of inclination formed by the tangent at the point of entry of the circular cutting edge of the knife projection into the annular grinding zone of the disk and the radius drawn from the center of the disk to the point of contact;

- the most possible value of the rate of penetration of the initial mass through the leading edge into the annular grinding cavity, due to which the retraction of the mass is more intensive;

- the most possible values of the rate of exit of the mass from the grinding

- the most possible values of the rate of exit of the mass from the grinding annular cavity;

- the excess of the value of the tangential component of the total force effect on the mass over the value of its normal component at all points of the circular cutting edge of the knife projections due to the most possible values of the entry angle;

- achievement of the expected technical result.

In a static position, the grinding set includes a rotating rotor, and stationary, with a hole for supplying the mass, stator disks, the grinding annular surfaces of which are mated through an interdisk gap, forming an annular grinding cavity (Fig. 1).

FIG. 1 shows, in the X-Y coordinate axes, a fragment of the frontal projection of the annular grinding surface of the rotor disk, on which the working surfaces of uniformly distributed circular knife protrusions 1, alternating with inter-knife grooves 2, are visible.

The circular arrow shows the direction of rotation of the rotor disc.

The area of the fragment is limited by circular edges 6, 7 and wavy clipping lines.

The area of the annular grinding surface is limited by the circular edges 5, 6 and wavy break lines. The circular edge 7 is the beginning of the circular chamfer 8, width ƒ, ending with the circular edge 5, which is the beginning of the entrance to the grinding annular cavity.

The areas of the grinding surfaces of the single knife projections 1 are shaded and limited by a circular edge:

- cutting 3, with a radius r ₁ = 0.633 R;

- not cutting 4, with a radius r ₃ = r ₁ + e, where e is the width of the groove 2;

- entrance 5 with radius r ₄ = r + ƒ;

- exit 6 with radius R.

The centers of curvature O _{1 of} all cutting edges 3, with a radius of r ₁ = 0.633R and concentric to them (see drawing), not cutting - 4, with a radius of r ₃ = r ₁ + e, are located on a circle 9 with a radius of r ₂ = OO ₁ = 0.6 R, drawn from the center of the O disk.

For the sake of simplicity, the X coordinate axis passes through the center O of the disc and the center of curvature O _{1 of the} circular cutting edges 3.

At the same time, the proposed solution has a number of features that significantly affect the operation of the proposed grinding set.

From the entrance to the annular grinding zone of the discs to the exit from it, at the points of application of the general force action, the value:

- the torque is constant in magnitude;

- the radius drawn from the center O of the disc to these points increases uniformly from the minimum to the maximum;

- the total peripheral linear speed at these points increases uniformly, from the minimum to the maximum;

- the total circumferential force applied at these points decreases uniformly, from maximum to minimum.

In contrast to the known solutions, the design of the proposed headset fulfills the requirement that the angle α formed by the tangents of the circular cutting edges 3 of the knife protrusions 1 and the radii drawn from the center O of the disc to the points of contact a or b increases uniformly, from the most the possible value of α _in - at the input circular edge of 5 discs (at point a), up to the most possible value of α _out - at the output - 6 discs (at point b).

This determines the following advantages of the proposed headset:

- the normal components of the total force impact at the input have a maximum value, and at the output, respectively, have a minimum value;

- the component of the penetration rate of the mass of the total circumferential speed of action on it, at the entrance to the grinding annular cavity, has, although less than at the exit, but the most possible optimal value, and the addictive component of the total force effect has, accordingly, the largest and most possible optimal value ;

- the speed of ejection of the processed mass at the exit from the grinding annular cavity has the most optimal value, and the ejection component of the total force effect has, respectively, although less, but also the most, optimal value.

For given values of r, r ₁ , r ₂ and R, the fulfillment of this requirement is associated with solving the problem of finding 3 values for circular cutting edges:

- coordinates of their center of curvature O ₁ ;

- α _in at the input circular edges of the 5 discs;

- α _{out the} output circular edges of the 6 discs.

In a dynamic position, the proposed grinding set works as follows.

The torque from the drive is transmitted to the driven end of the drive shaft and the rotor disk seated at its opposite leading end.

Wood fiber pulp, at a concentration of (6-15)%, is fed through the circular edge 7 (feed inlet) in the stator disk, chamfer 8, the inlet peripheral edge 5 of the stator inlet, into the annular inter-blade grinding cavity (formed by mating through an adjustable disk gap , the working surfaces of the rotor and stator discs), where it is distributed along the inter-knife grooves 2.

The value of the speed of penetration of the mass through the inlet into the grinding annular cavity, limited by the inlet circular edge 5 has a minimum, but the most possible optimal value, and the tightening component of the total force effect has, accordingly, the maximum, but also the most possible optimal value

As can be seen from figure 1, the active part of the knife protrusions 1, directly affecting the mass in the annular grinding cavity, are their convex side surfaces running on it, due to which the mass:

- first, it is pressed against the knife protrusions 1 and, under the influence of frictional forces, twists along with them;

- then, under the action of developing centrifugal and tangential forces, when the value of the friction force is exceeded, the mass rushes towards the output circumferential edge 6.

In one pass through the annular grinding cavity and along the inter-knife grooves 2, the bulk of the mass falls several times into the inter-disk gap, into the crossing zone of the cutting edges 3 and the working surfaces of the circular protrusions 1, where, under their force, it is subjected to more intense known grinding devices in the form of:

- cutting the fiber bundles with the cutting edges 3 of the knife projections 1, which leads to shortening and splitting of single fibers;

- crushing of the fiber bundles by the grinding planes of the knife projections 1, as a result of which the fibers are combed and their surface is fibrillated.

The nature of grinding also depends on the size:

- the gap between the knives;

- the specific pressure between the grinding planes of the knife projections 1;

- curvature of cutting edges 3;

- the peripheral speed of the rotor disk;

- mass temperature. In this case, the value:

- the speed of ejection of the processed mass, at the exit from the grinding annular cavity through the output circumferential edge 7, has the maximum and most optimal value;

- the throwing component of the total force impact has a minimum and most optimal value.

The wood-fiber semi-finished product that has passed the stage of mass grinding is sent to the next stage of the technological process.

Compared with the known solutions, the use of the proposed grinding set, by increasing the amount and optimal ratio of mechanical and hydrodynamic effects on the fibrous semi-finished product during one pass through the inter-knife grinding annular cavity, will provide the following technical and economic advantages:

- to intensify the process of forced transportation and simultaneous grinding of a mass of high concentration (6-15%);

- increase productivity;

- to improve the quality of processing of the fibrous semi-finished product;

- to reduce specific energy consumption.

Claims (1)

Grinding set, including rotating rotor and stationary stator disks with working surfaces facing one another, equipped with alternating through inter-knife grooves, circular knife protrusions directed in opposite directions, the cutting edges of which are made with eccentricity relative to the center of the disk, and the angle between the tangential cutting edges and radii from the center of the disc at the point of tangency increases uniformly from the most possible value - at the input edge of the disc, to the most possible value - at the output, characterized in that the radius of curvature of the circular cutting edges r ₁ = 0.633⋅R, and the centers of curvature are uniformly distributed on a circle with a radius drawn from the center of the disk, r ₂ = 0.6⋅R, where R is the radius of the output circular edge of the headset disk, to ensure grinding of an aqueous suspension with a concentration of wood fiber pulp of 6-15%.

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