Method for smoke gas residual heat utilization and device therefor

The invention relates to a method for utilizing the left heat of smoke and relative device, belonging to the heat exchange technique of left-heat boiler or heat exchanger. The invention feeds several smokes in different temperatures into boiler or heat exchanger, wherein the high-temperature smoke is cooled in high-temperature heat exchange face/area/chamber, while the temperature difference between high and low temperature smokes is higher than 50Deg. C when being mixed with low-temperature smoke at the temperature of the low temperature smoke, to recycle the left heat most. The inventive device is formed by a high temperature smoke inlet, a low temperature smoke inlet, a high temperature heat exchange face/area/chamber, a low temperature heat exchange face/area/chamber, mixing heat exchange face/area/chamber and a smoke outlet. The invention can recycle left heat most, with simple structure, flexible size and number, while the heat exchange face uses tubular box type, to confirm quality and improve installment speed, to be widely used in variable left-heat boilers and heat exchangers.