Classifier, pulverizing and classifying device, and pulverized coal burning boiler

A classifier, comprising:

• a housing configured to take in an air flow from below into a radially outer region of an inside space;
• a flow deflection portion disposed on an inner wall surface of the housing and configured to deflect the air flow toward a center axis of the housing;
• and
• an annular rotational portion disposed rotatably in a radially inner region positioned on a radially inner side of the radially outer region, of the inside space of the housing, and configured to classify particles which accompany the air flow,
• wherein the annular rotational portion includes a plurality of rotational blades arranged at intervals around a rotational axis of the annular rotational portion, and
• wherein the plurality of rotational blades form an outer shape of the annular rotational portion which forms an angle θ of not greater than 75° with a segment extended in a horizontal direction from the annular rotational portion outward in a radial direction, in a side view of the annular rotational portion, and
• wherein the classifier further comprises a material feed pipe extending downward into the housing of the classifier from an upper part of the housing of the classifier,
• wherein the plurality of rotational blades of the annular rotational portion are disposed around the material feed pipe, and
• wherein, provided that H is a total height of the annular rotational portion, a vertical distance between a lower end of the material feed pipe and a lower end of the plurality of rotational blades is not greater than 0.1H.