Air preheating and flue gas waste heat utilizing system and method

The invention particularly aims to the technical field of boiler air preheating. A disclosed air preheating and flue gas waste heat utilizing system comprises a flue gas channel (17), an air channel (20), an air preheater (9), a condensed water flue heat exchanger (8) and a condensed water air channel heat exchanger (19), and further comprises a condensed water feeding main pipe (15) and a condensed water returning main pipe (12); the flue gas channel (17) and the air channel (20) are connected with the air preheater (9); the condensed water flue heat exchanger (8) is arranged on the flue gas channel (17) at the back of the air preheater (9) in a flue gas flowing direction; the condensed water air channel heat exchanger (19) is arranged on the air channel (20) at the front of the air preheater (9) in an air flowing direction. According to the air preheating and flue gas waste heat utilizing system, flue gas discharge and heat exchange can be automatically adjusted according to change of operation conditions; on the premise of ensuring the safety of a heated surface and the regular operation of the system, the maximization of the heat circulation efficiency and the system economical efficiency is ensured.