Experimental study on the combustion and emission characteristics of a 350MW down-fired boiler under multi-source acoustic waves

To investigate the impact of multi-source acoustic waves on pulverized coal combustion under varying unit loads, an experimental study was conducted on a specific down-fired boiler with a rated capacity of 350 MW. In the test, 12 and 4 acoustic-assisted combustion devices were installed, respectively, in the primary combustion zone and the burning-out zone. The frequency of each single motor was controlled at 35Hz, and the intake pressure was 0.35–0.47 MPa. They were put into operation in a cycle of every 3 units. The combustion characteristics of W boilers under three loads of 190 MW (60 %), 265 MW (75 %), and 315 MW (90 %) were comparatively analyzed. The results show that at low load (190 MW), the sound wave effect leads to A-side 3.45 % increase in SOx concentration, significant fluctuations in NOx concentration (0.62 % increase on the A-side and a 9.23 % increase on the B-side), a 0.29 % decrease in coal consumption, and a 1.27 % decrease in the carbon content of fly ash. Under medium load (265 MW), the SOx concentration decreased by 0.2 %, the NOx concentration increased by 6 %–7 % (7.47 % on the A-side and 6.79 % on the B-side), coal consumption decreased by 0.4 %, and the carbon content of fly ash decreased by 1.55 %. Under high load (315 MW), the SOx concentration decreased by 1.24 %, the NOx concentration decreased by 7–8 % (8.22 % on side A and 7.62 % on side B), coal consumption decreased by 0.33 %, and the carbon content in fly ash decreased by 1.62 %. The test results prove that sound waves can effectively improve the combustion condition of pulverized coal and enhance the thermal efficiency of the boiler. Moreover, the addition of sound waves under high load has the best-promoting effect on the combustion of pulverized coal.