Co-combustion experimental study on high speed pulverized coal burner with large blending proportion of straw

In order to study the combustion and NOx emission characteristics on the industrial pulverized coal boiler，experimental study method is used and the high speed pulverized coal burner installed on a WNS boiler with a volume of 6 t/h is selected as the research object. The mixed fuel for the boiler is straw and Shenfu bituminous coal. Combustion stability at the high speed burner of the mixed fuel is the first research target and the second target is to study the effect of blending proportion，boiler load and air staging combustion on NOx emission. The research result shows that the high speed burner has a good combustion stability performance for the mixed fuel without any structural changes as the oxygen and pressure fluctuating is steadily. The boiler can fire immediately and get to full load in 26 minutes when the straw blending is 100% and its flame is orange in the burner and bright orange at the furnace tail. When the deep air staging combustion technology is used，tertiary air accounts for 50% of the total air. The experiment shows that NOx emission is about 420 mg/m3and the calorific value of fly ash is 1 320 kcal/kg when the straw is 0% while the initial NOx emission is between 110～120 mg/m3 when the straw blending ratio is 50% and 70% with the remaining fly ash calorific value is 600～700 kcal/kg. When the straw blending ratio is 100% the NOx emission is controlled under 200 mg/m3 and the ash calorific value is 0.1 t shows that co-combustion is beneficial to acquire lower NOx emission and higher combustion efficiency when deep air staging combustion technology is used. When the boiler load increases from 4 t/h to 6 t/h，the combustion efficiency is improved and NOx emission is decreasing when the straw blending ratio is 50% and 70%. While the NOx emission increases from 135 mg/m3 to 218 mg/m3 when the pure straw power is burned as the boiler load increases with the fly ash calorific value remains 0.Secondary air is the decisive factor which influences the NOx emission. For example NOx emission reduced from 417 mg/m3 to 182 mg/m3 when the valve lift is 27% and 100% for the secondary and tertiary air at 100% load with the fuel is blended with 50% straw. The NOx emission reduced from 711 mg/m3 to 205 mg/m3 when the valve lift is 20% and 100% for the secondary and tertiary air with the 80% boiler load.