Heat treatment apparatus for carbonaceous grains and method therefor

A heat treatment method for carbonaceous grains, using a heat treatment apparatus comprising:

• a furnace body, comprising a cylindrical furnace shell lined with refractory:
• a columnar upper electrode and a tubular lower electrode that are disposed, in the furnace body, above and below along a central axis of the furnace body;
• and
• a conductive tubular structure in the furnace body, being electrically connected to an upper end of the lower electrode in a manner of surrounding the upper electrode,
• wherein the tubular lower electrode is disposed to face the columnar upper electrode with a predetermined distance in a vertical direction,
• the heat treatment method comprising step of setting, to be equal to or less than 70%, a rate of change between electrical resistivity of grains at a time of light filling in which filling is performed only by an own weight of the carbonaceous grains and electrical resistivity of grains at a time of applying a predetermined load after tap filling of the carbonaceous grains, the rate of change being defined as (1-tap filling/light filling)×100.