Measurement and investigation of energy efficiency and emission of gas-fired boilers and potential of energy saving and emission reduction

Investigates the installation, energy consumption, boiler thermal efficiency and nitrogen oxide emission of 46 heating and industrial boiler rooms (167 boilers) in Ningxia, and analyses their energy saving and emission reduction potential. The results show that the investigated boilers are mainly small and medium-sized boilers, and the nitrogen oxide emission is 43 to 130 mg/m3, which is higher by 43% to 333% than the nitrogen oxide emission criterion of 30 mg/m3 for the local low-nitrogen retrofitting. The exhaust gas temperature of more than 85% of the heating boilers investigated is 130 to 190 ℃, and the return water temperature is 20 to 47 ℃. If the exhaust gas temperature is reduced to 25 to 53 ℃, the thermal efficiency of boilers can improve by 6% to 17% through the recovery and utilization of waste heat from exhaust gas. The recovery rate of waste heat is 34% to 95%, of which the latent heat recovered accounts for 23% to 66%. The unit capacity boiler produces flue gas condensate of 0.3 to 2.4 tons every day, and the fog-removing rate is 11% to 81%. The exhaust gas temperature of industrial boilers is 62 to 175 ℃. If the exhaust gas temperature is reduced to 25 ℃, the thermal efficiency of boilers can improve by 10% to 14% through the recovery and utilization of waste heat from exhaust gas, and the recovery rate of waste heat is 93% to 95%, of which the latent heat recovered accounts for 56% to 85%. The unit capacity boiler produces flue gas condensate of 1.7 to 2.5 tons every day, and the fog-removing rate is 80% to 82%. The energy saving, water saving, emission reduction and social, environmental and economic benefits of nitrogen reduction and exhaust waste heat utilization of gas-fired boilers in this area are huge.