Low pollution emission optimization scheme for gas-fired boiler based on deep utilization of flue gas waste heat

For the problems of high concentration of nitrogen oxides and fog emission from gas-fired boiler, lower efficiency of the boiler usually resulted by low nitrogen retrofitting, the boiler corrosion caused the flue gas recirculation, energy consumption increased to ensure air environment requirements of the boiler room and other issues, puts forward a low nitrogen emissions optimization scheme that based on deep recovery flue gas condensation heat and flue gas condensate water, which heating the water in the network, combusting air and heating air by flue gas waste heat. Taking a retrofitting project of thermal efficiency improvement and nearly smoke-free emission of a 29 MW boiler in Beijing with the flue gas temperature dropped below 70 ℃ and the thermal efficiency being more than 95% as an example, makes a technical and economic benefit analysis on energy saving, water saving, fog removing and nitrogen emission reduction. The measurement results show that, the flue gas temperature drops from 48.6-60 ℃ to 37.6-46 ℃ under different loads of boiler, resulting 5.2%-8.4% of energy saving, the unit capacity (700 kW) of the boiler recovers condensate water of 0.68-1.54 t/d, the nitrogen oxide emission is under 30 mg/m3 and the water (fog) removing rate of flue gas reaches 66%, and the energy saving, water saving and environmental protection effects are remarkable.