System and method for high-proportion circular reduction of pellet roasting flue gas of chain grate-rotary kiln

The invention provides a chain grate-rotary kiln pellet roasting flue gas high-proportion circulation reduction system and method. The system comprises a chain grate, a rotary kiln, an annular cooler and a flue gas backflow pipeline subsystem used for flue gas circulation which are connected in sequence. Smoke in a first air bellow set and a second air bellow set at the bottom of a first preheating section in the chain grate machine is conveyed to a first cooling section and a second cooling section of the circular cooler through smoke backflow pipelines to participate in cooling, and meanwhile the smoke in the first cooling section is conveyed to a rotary kiln to participate in roasting. The flue gas of the first preheating section is divided into two paths to be efficiently recycled, so that waste heat recovery can be realized, the total flue gas amount in the system can be effectively reduced by 30-40%, meanwhile, the process emission reduction of NOx reaches 14-16%, the operation load of a tail end pollut