Abstract: A closure mechanism (16) for controlling charging of material through a port into a rotary kiln such as a cement kiln comprises a first and second portion (24,26), and a passage (29) which communicates with the port (12) to enable material to pass into the kiln when the mechanism is open. The first portion (24) acts to prevent reactive material passing through the passage and the closure (26) acts to close the port when the mechanism is in a closed position. The mechanism is movable to enable material such as tires to pass into the kiln but helps prevent premature degradation of the material by the heat of the kiln when the mechanism is closed.