A retort heating apparatus for processing a feed material includes a heating chamber bounded at least in part by a side wall. A plurality of baffles are at least partially disposed within the heating chamber. Each baffle includes an elongated body having a top surface, at least a portion of the top surface being arched. The plurality of baffles are vertically and horizontally spaced apart so that substantially all of the feed material that vertically passes through the heating chamber is horizontally displaced as the feed material passes by the baffles. Systems are also provided for heating the feed material within the heating chamber.