Flue gas circulating system

The utility model discloses a flue gas circulating system which comprises a sintering machine, an igniter and a plurality of flue gas covers are arranged above the sintering machine, a plurality of sintering air boxes are arranged below the sintering machine, each sintering air box is respectively connected with a large flue and a circulating flue through a branch pipe, and a valve is arranged on the branch pipe. The circulating flue is connected with the flue gas cover through a flue gas circulating pipeline, the large flue and the circulating flue are located below the sintering air boxes, the lengths of the large flue and the circulating flue are matched with the total length of the sintering air boxes, and flue gas of the sintering air boxes converges into the same circulating flue; and the circulating flue is connected with a flue gas circulating pipeline which is connected with a plurality of flue gas hoods. Smoke generated in the sintering machine can be completely used for supplying heat to the sinter