METHOD OF OPERATING A MULTIPLE HEARTH FURNACE

摘要

A method of operating multiple hearth furnace (10) with a plurality of vertically aligned hearth floors (361, 362, 363, 364, 365), comprises in particular following steps. A first material is fed onto the uppermost heart h floor and moved over this uppermost hearth floor (361) before it falls throu gh a drop hole (40) onto the next lower hearth floor. This first material is processed in this way from hearth floor to hearth floor down to the lowermos t hearth floor (366). A second material is fed onto one of the hearth floors t o be mixed into the first material. This second material (64) is moved separately from the first material in a separate annular zone (68) of the hearth floor onto which it is fed before it is mixed into the first material . The method allows to provide an efficient thermal preconditioning of the second material prior to mixing it into the first material without requiring any supplementary equipment therefore.