The invention provides an internal-external circulation
system for
sintering flue gas. The internal-external circulation
system comprises an internal circulation device, an external circulation deviceand a desulfurization and
denitrification device, wherein the internal circulation device is connected with a middle-front section
flue of a main
flue of a
sintering machine, and first purified fluegas is obtained and is then circulated into the
sintering machine; the outer circulation device is connected with a
machine head flue and a middle-rear section flue of the main flue of the sintering machine, second purified
flue gas is obtained, one part of the second purified
flue gas is circulated into the sintering machine, and the other part of the second purified
flue gas enters the desulfurization and
denitrification device; and flue gas from the middle-rear section flue exchanges heat with flue gas from the middle-front section flue and then enters the outer circulation device. The invention further provides an internal-external circulation
system for sintering flue gas. According to the invention, the circulation rate of the sintering flue gas is increased from 20% to 60% or above,the
utilization rate of
waste heat is increased, the concentration of
NOx in the flue gas is reduced, a two-stage CO removal reaction is achieved, and a large amount of investment and operation costis saved.