1. Determine the target value of transformation
(1) when the coal is currently in operation in the fuel power plant, the NOX emission value is controlled from 200 to 150mg/Nm3 at the load of 500MW~1000MW. The target value was obtained by comprehensive comparison of NOX reduction capacity of denitrifying device and NOX reduction capacity of low nitrogen burner.
(2) after the modification, there is no obvious change in incomplete loss and smoke discharge loss of the boiler.
(3) after the modification, the characteristics of coking, high temperature corrosion and steam temperature and vapor pressure of the boiler are the same as before the modification.
2. How to transform the low-nitrogen burner of 1000MW tower furnace?
1. Low-nitrogen burner renovation scheme 1
(1) the original six-layer SOFA is a newly added three-layer SOFA. After the renovation, the ratio of the total SOFA exhaust air volume to total air volume will be increased from the original 23% to about 40%.
(2) replace all secondary air vents in the main burner area to reduce the secondary air flow area.
(3) replace the primary air pulverized coal nozzle, nozzle and elbow in the main burner area.
2. Low-nitrogen burner renovation plan ii
Only the original six-layer SOFA has a new three-layer SOFA with no changes in other burners.
3. Comparative analysis of transformation plans
(1) scheme 1: large amount of renovation project and high renovation cost;
(2) scheme 2: it affects the combustion efficiency of the boiler, and there are some safety risks. The detailed analysis is as follows: the primary secondary air rate of the boiler is 79.16%, the burnout wind rate is 23%, the secondary air rate of the main combustion zone is 56.16%, and the secondary air design speed is 60.3m/s. If a new section of exhaust air is added after the construction, the wind rate is 17%, while the area of secondary air flow in the main combustion area does not decrease, the area of secondary air flow increases by 17/79.16=21.475%. After the reconstruction, the secondary wind speed dropped to 49.64m/s.
The cross-section of the furnace of the tower boiler of 1000MW unit is large, so it needs high secondary wind speed to ensure the penetration depth and influence depth of the torch, to reach the vicinity of the nozzle of the adjacent burner, to ignite the adjacent burner, and to effectively promote the combustion of coal powder. The decrease of secondary wind speed will have adverse effects on the flow field in the furnace. On the one hand, it is not conducive to the combustion of coal powder; on the other hand, the secondary wind will weaken the effect of primary wind on the wind packing powder, and the risk of slag formation and high temperature corrosion of the boiler is increased.
Through comprehensive comparison, choose reform plan 1.
Iii. Commissioning after renovation
1. It is important to control NOX emission value reasonably after the modification of the low nitrogen burner. Low NOX control may affect the boiler combustion efficiency, and in severe cases, may cause severe high temperature corrosion.
Through reasonable combustion control adjustment, when 500MW~1000MW is loaded, the NOX emission value can be controlled within the set design range: 200mg /Nm3, which can not only ensure the basic economic efficiency of the unit is not affected, but also eliminate the potential safety risks after the modification of the low-nitrogen burner.
According to this core idea, the combustion adjustment is carried out under different operating conditions. According to the optimal adjustment effect, the adaptive optimization of each combustion automatic control system is carried out.
2. Comparison of effects before and after transformation
(1) the monthly average reduction of NOX emission value was 70mg/Nm3;
(2) the burning loss of the boiler is basically unchanged;
(3) due to low NOX emission, the daily consumption of ammonia decreased by about 2t/h, and the annual consumption of ammonia was calculated at 3,000 yuan per ton, saving a total of 2.19 million yuan.
(4) after the modification, the main steam temperature is 2~3 times higher than the original value, but after the adjustment, the unit economy will not be affected.
(5) after the modification, there is no obvious change in boiler coking, high temperature corrosion, variable load stability, etc.
For more information on low nitrogen burners, please consult Beijing chuangwei electromechanical equipment co., LTD.