A flue gas waste heat utilization system was proposed

which is based on capacity increase of air preheater and heating condensation water by primary air. It can control the temperature of primary air entering the pulverizing system and avoid direct mixing of the cold air for coals with low moisture content. It also can reduce the abrasion and low-temperature corrosion of the heating surface. For a supercritical 600 MW coal-fired unit

applying this system reduced the flue gas temperature by 15 ℃. Comparison of system structure

energy saving effect and economy were performed between the above waste heat utilization system and the conventional waste heat utilization system equipped with low pressure economizer. The results show that

the heat transfer area that the primary air-condensation water heat exchanger required is less than 1/3 of the low pressure economizer

and the land area the new system covers is about 1/6 of that of the conventional system. The waste heat utilization system based on capacity increase of air preheater and heating condensation water by primary air can reduce the standard coal consumption for power supply by 2.42 g/(k W·h)

which is 2.75 times as much as that of the conventional waste heat utilization system

and it can increase the average annual net income by 5.901 million yuan

which is about 3.5 times as much as that of the conventional waste heat utilization system. Therefore

the proposed flue gas waste heat utilization system saves the materials and site area

which has dramatic energy conservation and economic effect.