Classifier and a method of modifying a classifier for use with a pulveriser

A method of modifying a classifier for use with a pulveriser, the classifier being operable to classify crushed particulate material received from the pulveriser into a fine fraction which is expelled from the classifier and a coarse fraction which is returned to the pulveriser for further crushing, the classifier including:

• an external housing;
• an internal housing, disposed at least partially within the external housing, the internal housing defining an inward classification zone and further including:
• an airflow inlet for receiving a pulveriser airstream containing crushed particulate material from the pulveriser into the classification zone;
• at least one operatively upper exit;
• and
• a rejection outlet, arranged operatively below the exit, the method including:
• retrofitting at least two articulated closure members to a lower region of the classifier at or toward the rejection outlet, wherein the closure members are displaceable relative to the lower region of the classifier between:
• a closed position in which the closure members are arranged side-by-side such that adjacent sides of the closure members are in abutment and a cross-sectional area of the rejection outlet is at a minimum;
• and
• an open position in which the adjacent sides of the closure members are not in abutment and the cross-sectional area of the rejection outlet is increased.

A self-cleaning, load operated rejection gate for a particle classifier, the rejection gate being configured for connection to an operatively lower part of a particle classifier in a configuration in which the gate, together with the classifier, defines a rejection outlet, and in which the rejection gate is movable relative to the classifier between a closed position and an open position, the rejection gate including:

• a plurality of closure members which, when the gate is in the closed position, are arranged alongside one another in a configuration in which:
• sides of adjacent closure members are in abutment such that the closure members collectively define a depending skirt which has a continuous, operatively lower periphery;
• and
• a cross-sectional area of the rejection outlet is at a minimum;
• and, when the rejection gate is in the open position, sides of adjacent closure members are not in abutment and the cross-sectional area of the rejection outlet is increased.