Because the outdoor air temperature in cold regions is severely low in winter

the combustion-supporting air will cause deflagration and vibration while directly supplied to the boiler and the combustion efficiency is also decreased. At the same time

the temperature of the return water in a large heating system

and the exhaust gas from the gas boiler

are both high. Thus

the exhaust gas could not be cooled down to a relatively low temperature by the return water during the waste heat utilization process. This paper presents a new way to heat the air by using flue gas waste heat

which is smaller

requires less space

and has less resistance compared with conventional heat exchange equipment. The proposed method can be applied to the flue gas waste heat deep-utilization of a large gas heating boiler. Field test results show that the flue gas waste heat deep-utilization and the combustion-supporting air heating system can cool the flue gas temperature near to or even lower than the return water temperature of heating network. The utilization efficiency of gas combustion is increased by 13.2 %

and the recovery rate of the flue gas waste heat is 66.7 %. Then

flue gas waste heat deep recovery is realized

and the problem in which the combustion-supporting air causes deflagration and vibration while directly supplied to the boiler is solved. The paper provides a reference for flue gas waste heat deep-utilization in cold regions

and for combustion-supporting air heating system optimization.