US 4,536,211 AGranted

Waste gas circulation method and system for sintering apparatus

AssigneesSumitomo Metal Industries, Ltd., Sumitomo Heavy Industries, Ltd.

InventorsTakashi Futakuchi, Kiyofumi Nakamura, Yoshimasa Sato, Toshio Tsukuda, Hiroyuki Shiraishi

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Abstract

Herein disclosed are both waste gas circulation method and system for effectively recovering waste heat from an on-strand type sintering apparatus which has its sintering and cooling zones extending continuously along a horizontal strand. The hottest waste gases coming from the final stage of the sintering zone and the front stage of the cooling zone, in which the sintering reaction of a charge mixture is completed, are subjected to heat recovery, and sulfur oxides in the hottest gases are prevented from condensing on the water pipe or pipes of a waste-heat boiler by preheating the water, which is supplied for the heat recovery, with the still hot waste gases coming from the downstream half of the cooling zone. The heat of the still hot waste gases are exchanged with cold water so that this water may be heated into hot water. On the other hand, the heat of the hottest gases is exchanged with steam so that this steam may be heated into superheated steam. Moreover, the heat of the hot waste gases obtained as a result of the second-named heat exchanging step is further exchanged with the hot water heated at the first-named heat exchanging step. Thus, it is possible to conduct the ore sintering operation of regenerative type while assuring that the boiler components in those heat exchanging operations will not be corroded by the waste gases.

A method for recovering heat from the hot waste gas from a conveyor-type sintering apparatus in which a charge mixture of ore, solid fuel and flux is sintered, said sintering apparatus comprising a sintering zone through which said mixture is moved and is sintered therein and a cooling zone located downstream from said sintering zone and through which said mixture is moved and is cooled therein, said sintering zone having first, second and third groups of wind boxes for withdrawing heated waste gas from said sintering zone, said first, second and third groups of wind boxes being arranged in series in said sintering zone and being located, respectively, at the front stage, intermediate stage and final stage of said sintering zone, said cooling zone having fourth, fifth and sixth groups of wind boxes for withdrawing heated waste gas from said cooling zone, said fourth, fifth and sixth groups of wind boxes being arranged in series in said cooling zone and being located, respectively, at the front stage, intermediate stage and final stage of said cooling zone, the steps comprising:

a first heat exchange step of flowing a first stream of the heated waste gas from said fifth and sixth groups of wind boxes in indirect heat exchange with cold water whereby to extract heat from said first stream of heated waste gas and to heat and said cold water to transform it into hot water;
and
a second heat exchange step of flowing the hot water obtained in said first step in indirect heat exchange with a second stream of heated waste gas from said third and fourth groups of wind boxes whereby to extract heat from said second stream of heated waste gas and to heat said hot water to transform it into steam, said second stream of heated waste gas containing sulfur oxides and being maintained, in said second step, at a relatively high temperature effective to prevent condensation of said sulfur oxides in the form of droplets of sulfuric acid.

Abstract

Claims9