Low nitrogen burner alteration purpose: burner and air distribution mode after the transformation, mainly in the chamber of a stove or furnace in order to realize the real separation and thick shade relatively concentrated to furnace combustion phase gradient classification requirements, realize the original reduce NOx and ignition stability purposes. However, after the modification, there are some phenomena, such as easy overtemperature of the front screen, large thermal deviation, low reheating steam temperature and low main reheating steam temperature of the single C powder making system. The technology of low oxygen combustion has certain influence on the steady combustion of boiler
1. Low oxygen combustion control nitrogen oxides and stable combustion analysis
According to the requirement of low nitrogen combustion, the main combustion area of the furnace reduces the excess air coefficient, carries on the oxygen-poor combustion, reduces the furnace temperature of the main combustion area, and inhibits the formation of nitrogen oxides. However, the stability and safety of boiler combustion are greatly reduced by too low oxygen content control. Taking the high-load 300MW as an example, the total air volume was reduced from 80% before the renovation to 70% ~ 75%, and the auxiliary air baffle in the main combustion area was adjusted to be small. SOFA3 SOFA2:100% : 100% air distribution mode, and before the big air volume, SOFA than wind baffle doesn't open or small open degree, SCR nox entrance was decreased significantly, but the air distribution mode of a stove or furnace anti interference ability, bellows differential pressure chamber of a stove or furnace can only remain at around 600 pa, gravely deviates from the furnace before modification of the given optimal value more than 850 pa. In case of failure of the main auxiliary equipment of the smoke system and coal quality mutation, it is likely to cause fire extinguishing, so it is safe to increase the oxygen content or turn down the upper SOFA air baffle properly.
2. Graded gradient combustion control nitrogen oxides and stable combustion analysis
The transformation from the aspects of the combustion control of nox emissions, smaller scale, the actual control can only implement horizontal shading burning on air distribution adjustment means, runtime only can satisfy the steady combustion under low load, the combustion efficiency and decreased. When the load is high, the combustion is stable and the anti-disturbance capability is strong. Low load to load of 150 mw, for example, total air volume control in 45% ~ 50% because of the limitation of bellows differential pressure chamber of a stove or furnace top sofa opening can't wind is very big, each layer of the opening will affect the size of the steam temperature of thermal deviation, serious when reach 40 degrees, and any layer after sofa wind up to more than 50%, will cause the B layer short flash of flame detector, seriously affecting the stability of combustion. Therefore, objectively speaking, the 150MW load is basically SOFA wind to adjust the thermal deviation, and the graded low nitrogen combustion is basically not realized. Nitrogen oxides are only significantly related to the amount of oxygen they control.
300 mw conditions, due to the combustion stability, strong ability to resist disturbance, coupled with the coal pulverizing system run more, the upper three times with powder feeding machine can reduce the lower wind speed, grading gradient burn relatively obvious, nox under control. The opening degrees of the three-layer SOFA wind 1-3 are respectively: 50%, 100%, 100%, 72% of the total air volume, 506mg/m3 of the nitrogen oxides at the inlet of SCR, 536 degrees and 535 degrees of the main reheat vapor temperature. All parameters are within the normal range, the combustion is stable, the flame TV is golden, and the fire inspection is normal without fluctuation. The results show that the staged combustion effect is better at high load, which can ensure stable combustion and effective control of nitrogen oxide emissions.
3. The role of SOFA wind in various loads
(180 mw) under low load SOFA in the classification of burning wind effect is not big, mainly according to the coal pulverizing system running in a different way to adjust the steam temperature of thermal deviation, with the increase of load (180 ~ 220 mw), the SOFA of the opening of the wind rising, grading gradient combustion is becoming more and more obvious. In order to maximize the comparison of experimental data, 300MW load has been taken as an example. The parameters were: SOFA wind 1 ~ 3 opening degrees were: 50%100%100% total air volume 72%, SCR inlet nox value was 506mg/m3, and the main reheat vapor temperature was 536 degrees and 535 degrees respectively. The upper SOFA wind opening was closed, and the lower and larger auxiliary air baffle was adjusted to run stably for 20 minutes. It was found that the nitrogen oxides in the SCR inlet increased to 680. The two modes of adjustment, the furnace flame is golden yellow and the fire test is normal, but there is a significant difference in nitrogen oxides, so the high load is the opening of SOFA wind can effectively inhibit the nitrogen oxides emissions.