Vertical roller mill
Provided is a vertical roller mill equipped with a rotary classifier for causing a plurality of classification blades provided above a rotary table and positioned around an axis to rotate about the axis, wherein: of a solid fuel pulverized by a roller, the rotary classifier guides solid fuel fine powder from an outer-circumferential-side space to an inner-circumferential-side space surrounded by the plurality of classification blades, and suppresses, by collision with the plurality of classification blades, an intrusion of solid fuel coarse powder into the inner-circumferential-side space; and each of the plurality of classification blades is shaped in a manner such that there is no interference between a scattering direction in which the coarse powder that collided with the classification blades scatters and an intake direction in which the fine powder is guided to the inner-circumferential-side space, and the scattering direction is oriented upward relative to a horizontal direction.
1. A vertical roller mill, comprising:
a rotary table that rotates about an axis by a driving force from a drive unit;
a fuel supply unit for supplying a solid fuel to the rotary table;
a roller for pulverizing the solid fuel supplied to the rotary table;
a rotary classifier for causing a plurality of blades provided above the rotary table and disposed around the axis to rotate about the axis; and
a ventilation unit for blowing oxidizing gas for supplying the solid fuel pulverized by the roller to the rotary classifier;
the rotary classifier guiding, of the solid fuel pulverized by the roller, fine powder smaller than a predetermined particle size from an outer-circumferential-side space to an inner-circumferential-side space surrounded by the plurality of blades, and suppressing, by collision with the plurality of blades, an intrusion of coarse powder larger than the predetermined particle size into the inner-circumferential-side space; and
each of the plurality of blades having a plate shape with a first end portion in a longitudinal direction disposed on an upper side along the axis and a second end portion disposed on a lower side along the axis, and the longitudinal direction being inclined from the axial direction so that the first end portion is positioned behind the second end portion in the rotational direction of the rotary classifier.
2. The vertical roll mill according to claim 1 , wherein:
a surface through which an outer circumferential side end portion of each of the plurality of classification blades centered around the axis passes is a side surface of a circular truncated cone that protrudes downward from above along the axis; and
an angle formed by the side surface of the circular truncated cone and a plane orthogonal to the axis is from 65 degrees to 75 degrees, both inclusive.
3. The vertical roller mill according to claim 2 , wherein the angle formed by the side surface of the circular truncated cone and the plane orthogonal to the axis is 70 degrees.
4. The vertical roller mill according to claim 1 , wherein the longitudinal direction is inclined at an angle of from 13 degrees to 23 degrees, both inclusive, from the axial direction when the blade is orthogonal to the axis and viewed from a radial direction that passes through the blade and the axis.
5. The vertical roller mill according to claim 4 , wherein the longitudinal direction is inclined at an angle of 18 degrees from the axial direction when the blade is orthogonal to the axis and viewed from a radial direction that passes through the blade and the axis.