Pulverizing device, throat for pulverizing device, and pulverized-coal fired boiler

1. A pulverizing device, comprising:

a housing;

a pulverization table configured to rotate inside the housing; and

a throat, disposed inside the housing on a radially outer side of the pulverization table, for forming an upward air flow,

wherein the throat includes:

an inner ring extending along an outer periphery of the pulverization table;

an outer ring, disposed on a radially outer side of the inner ring so as to form an annular flow passage between the inner ring and the outer ring;

a plurality of throat vanes disposed between the inner ring and the outer ring, and wherein, following expressions (a) and (b) are satisfied:

2.0≤ L/d≤ 4.0  (a)

0.5≤ H/d≤ 1.5  (b)

where H is a gap between the inner ring and the outer ring with respect to a radial direction, L is a length of the throat vanes, and ‘d’ is a distance between

adjacent two of the throat vanes,

wherein each throat vane is oblique toward an upstream side, with respect to a rotational direction of the throat, from a lower end toward an upper end of the throat vane, and

wherein following expression (d) is satisfied:

H/d≥ 0.95×(sin θ) −2.0 ×( L/d ) −1.2   (d)

where θ is an inclination angle of the throat vanes with respect to a rotational center axis of the throat.

2. The pulverizing device according to claim 1 ,

wherein each throat vane is oblique toward an upstream side, with respect to a rotational direction of the throat, from a lower end toward an upper end of the throat vane, and

wherein following expression (c) is satisfied:

45°≤θ≤60°  (c)

where θ is an inclination angle of the throat vanes with respect to a rotational center axis of the throat.

3. The pulverizing device according to claim 1 ,

wherein the inner ring includes a flow guide portion for guiding an air flow which flows from below into the annular flow passage, the flow guide portion being disposed on a lower end side of the inner ring and having a curved shape so as to become closer to an inner side, with respect to the radial direction, toward a lower end of the inner ring.

4. The pulverizing device according to claim 1 ,

wherein a circumferential speed of the pulverization table is not less than 3 m/s and not more than 5 m/s.

5. A throat for a pulverizing device, comprising:

an inner ring extending along an outer periphery of a pulverization table;

an outer ring, disposed on a radially outer side of the inner ring, for forming an annular flow passage between the inner ring and the outer ring; and

a plurality of throat vanes disposed between the inner ring and the outer ring, wherein following expressions (a) and (b) are satisfied:

2.0≤ L/d≤ 4.0  (a)

0.5≤ H/d≤ 1.5  (b)

where H is a gap between the inner ring and the outer ring with respect to a radial direction, L is a length of the throat vanes, and ‘d’ is a distance between adjacent two of the throat vanes,

wherein each throat vane is oblique toward an upstream side, with respect to a rotational direction of the throat, from a lower end toward an upper end of the throat vane, and

wherein following expression (d) is satisfied:

H/d≥ 0.95×(sin θ) −2.0 ×( L/d ) −1.2   (d)

where θ is an inclination angle of the throat vanes with respect to a rotational center axis of the throat.

6. The pulverizing device according to claim 1 , configured to pulverize coal as a to-be-pulverized material.

7. A pulverized-coal fired boiler, comprising:

the pulverizing device according to claim 6 ; and

a furnace for combusting pulverized coal obtained by the pulverizing device.