低氮燃燒器改造后穩定燃燒分析

低氮燃燒器改造目的：燃燒器及配風方式在改造后，主要是為了實現了爐膛內部真正的濃淡分離和濃相相對集中達到爐內燃燒梯度分級要求，實現最初的降低NOx和著火穩定性目的。但改造后存在前屏易超溫、熱偏差較大、再熱汽溫偏低以及單C制粉系統運行主再熱汽溫均偏低的現象。且采用的低氧分級燃燒技術對鍋爐的穩燃有一定的影響。
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、低氧燃燒控制氮氧化物與穩定燃燒分析
1. Low oxygen combustion control nitrogen oxides and stable combustion analysis

根據低氮燃燒的要求，爐膛的主燃燒區域減小過量空氣系數，進行貧氧燃燒，降低主燃燒區域的爐溫，來抑制氮氧化物的生成。但過低的氧量控制，使鍋爐燃燒的穩定性及安全性大大折扣。以高負荷300MW為例，將總風量由改造前的80%降至70%～75%，調整關小主燃燒區域的輔助風擋板，SOFA1-3層采用SOFA1：80%;SOFA2：100%SOFA3：100%配風方式，與之前的大風量，SOFA風擋板不開或小開度相比，SCR入口氮氧化物有了顯著下降，但此種配風方式下爐膛抗擾能力下降，爐膛風箱差壓只能維持在600pa左右，嚴重偏離該爐改造前給定的優化值850pa以上。在風煙系統主要輔助設備出現故障時及煤質突變時，很可能造成滅火，所以安全起見，只能適當增加氧量或者關小上層SOFA風擋板。
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、分級梯度燃燒控制氮氧化物與穩定燃燒分析
2. Graded gradient combustion control nitrogen oxides and stable combustion analysis

此次改造從燃燒方面控制氮氧化物的排放上講，改造范圍較小，實際控制上只能實行水平濃淡燃燒加配風調整手段，低負荷運行時僅僅能滿足穩定燃燒，燃燒效率上講又有所下降。負荷較高時，燃燒穩定，抗擾能力較強，分級梯度燃燒可以發揮明顯作用。低負荷以負荷150MW為例，總風量控制在45%～50%由于爐膛風箱差壓的限制，上層sofa風開度不能很大，每層開度的大小將影響汽溫的熱偏差，嚴重時達到40度，且任一層SOFA風開大至50%以上后，會造成B層火檢短閃，嚴重影響燃燒的穩定性。所以從客觀上講，150MW負荷基本上是用SOFA風來調整熱偏差，分級低氮燃燒的基本未能實現。氮氧化物此時只是跟氧量量控制的大小有明顯的關系。
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.

低負荷(180MW以下)SOFA風在分級燃燒中的效果不大，主要是根據制粉系統運行方式不同來調整汽溫的熱偏差，隨著負荷(180～220MW)的增加，SOFA風開度不斷加大，分級梯度燃燒也越來越明顯。為保證實驗數據對比最大化，現已300MW負荷為例。按分級梯度燃燒最優化調整，取參數：SOFA風1～3三層開度分別為：50%100%100%總風量72%，SCR入口氮氧化物測量值為506mg/m3，主再熱汽溫536度、535度。關閉上層SOFA風開度，調整開大下層輔助風擋板穩定運行20分鐘，發現SCR入口氮氧化物上升至680。兩種調整方式，爐膛火焰金黃色，火檢正常，但氮氧化物有明顯的區別，所以高負荷是SOFA風的開大可以有效的抑制氮氧化物的排放。

(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.