Method for treating pourable, inorganic grain, and rotary tube suitable for performing the method

A method for treating pourable, inorganic grain in a heated rotary tube that rotates about an axis of rotation and surrounds a treatment chamber that is divided into a plurality of treatment zones (A;

• B;
• C;
• D) by separating elements, the plurality of treatment zones including at least one reaction zone (C), the method comprising:
• supplying the grain to the treatment chamber at a grain inlet side;
• transporting the grain, in a grain transport direction, to a grain outlet side;
• and
• exposing the grain to a treatment gas;
• wherein spent treatment gas is suctioned out of the reaction zone (C) by a gas manifold, which rotates about the longitudinal axis thereof;
• wherein the spent treatment gas is suctioned out of the gas manifold by a rotationally fixed suction pipe, which protrudes into the gas manifold;
• wherein the treatment gas is introduced into the gas manifold at the grain outlet side and is conveyed from one chamber (A;
• B;
• C;
• D) to the next chamber counter to the grain transport direction and emerges from the gas manifold, into the reaction zone (C), through at least one gas outlet wall opening, and spent treatment gas enters the gas manifold again, from the reaction zone (C), through at least one gas inlet wall opening;
• and
• wherein between the gas outlet wall opening and the gas inlet wall opening, the gas manifold is closed.