Low Nitrogen Combustion Transformation and Operation Optimization Adjustment of Boiler in Thermal Power Plant


Low Nitrogen Combustion Transformation and Operation Optimization Adjustment of Boiler in Thermal Power Plant
The emission of nitrogen oxides (NOx) in the low nitrogen combustion process poses a threat to the ecological environment and human health. By adopting specialized methods, the low nitrogen combustion transformation and operation optimization adjustment of the boiler can effectively control NOx emissions, improve production efficiency and reduce environmental and ecological problems. In this paper, the status quo of low nitrogen combustion technology is briefly analyzed, and the transformation scheme and optimized operation process of low nitrogen burner are proposed.

China attaches great importance to the emission of air pollutants from thermal power plants and has issued various laws, regulations, and prevention policies. In addition to taking economic benefits into consideration, thermal power plants also take environmental issues into account in the development process, think about how to reduce the emission of air pollutants, and propose effective implementation methods. In fact, the retrofit of power plant boilers can effectively control NOx emissions, reduce environmental and air pollution, and achieve environmental benefits and objectives.

First: Current status of low nitrogen combustion technology
Reducing NOx emissions can effectively control air pollution. In terms of the production process, low nitrogen combustion technology is mainly used, with flue gas denitration as the auxiliary. Among these factors, the nitrogen generation mechanism is related to low nitrogen combustion technology, and the main components are low oxygen combustion and flue gas recycling. Burners are arranged longitudinally to promote the formation of three plates in the oxidation-reduction area, main reduction area, and burn-out area. This process can also place the burners in proper positions according to different boiler conditions, so as to facilitate the low temperature and low oxygen combustion of organic dyes and air distribution in the boiler, and achieve zoning and classification, so as to effectively control NOx emissions and achieve a good clean combustion effect.

Second: Low NOx burner transformation scheme
1. Select the burner
According to the actual needs, a scientific transformation scheme of low nitrogen burners is formulated for reference and optimization. Horizontal and vertical bias burners are widely used in China. The former is mainly used to separate the pulverized coal in the horizontal direction and separate its concentration from its dilution. It is widely used in the desulfurization work in the furnace. In the desulfurization work in the furnace, the jet tends to the central position in the furnace, which has strong direct entrainment and airbag coal effects. The vertical thick thin burner has the same principle, but the use process is just the opposite. It is mainly responsible for vertical pulverized coal separation, and the implementation effect is very good. The selection of burner type must not be blind. In addition to isolating the thick and thin pulverized coal in the furnace, it is also necessary to comprehensively master the separation ratio, various parameters, etc. It is strictly prohibited to have low nitrogen residues in the furnace.

2. Modification of the main burner
For the transformation of the main burner, not only the standard height of the main burner should be determined, but also the positions of the air ducts and bellows of the four bellows should be scientifically fixed, and all nozzles and elbows should be replaced to ensure that all components can meet the standard. The last layer is in the form of an axial plug-in plasma burner, which can also convert the remaining primary air burners into rich lean burners, with the upper concentrated and lower lean or the lower concentration and upper lean. In this context, the use of a high heat resistance steel plate is good. The secondary air nozzle in the middle of the four layers is kept closed. At the same time, the remaining secondary air nozzle is replaced. Also, the layout of the air nozzle attached to the wall should be taken into account to ensure that the surface layer of the water wall has sufficient oxygen, so as to avoid excessive furnace temperature due to insufficient oxygen, resulting in excessive furnace temperature, slagging, and corrosion. In addition, the other secondary air nozzles need to be changed to change the jet direction. The angle of primary air and other secondary air nozzles should be mainly controlled to fully mix the early oxygen deficient fuel and the late oxygen supply.

3. Scientifically design OFA nozzle and secondary air
Although the boiler combustion system is relatively complex, the OFA nozzle has a simple structure and is widely favored in the industry. In practical application, the OFA nozzle needs to be applied again on the basis of the original system, giving full play to its advantages, taking into account the tangency, and effectively controlling the airflow in the furnace to make the temperature of the furnace outlet normal. Assuming that the original OFA nozzle size, wind speed setting, air volume, and other indicators can not meet the requirements of low nitrogen combustion technology transformation, the heat-resistant version can be directly blocked, or it can be re-transformed. A large proportion of secondary air is arranged at the upper end of the burner, which is conducive to the classification of air in the furnace, reduces nitrogen oxides, and enables the boiler to be fully burned. In the design of secondary air, the location, area, and other indicators of the burnout zone should also be considered.

Third: The optimized operation scheme of nitrogen combustion
1. Optimize and adjust the perimeter wind of primary and secondary air
The change in airflow has a certain impact on the concentration of nitrogen oxides. If the airflow is too large, the furnace oxygen content and the concentration of nitrogen oxides are low. According to the adjustment of the operation state of each power supply and the comparison of the air distribution methods such as the forward and reverse pagodas, it can be seen that the air distribution operation of the inverted pagodas produces fewer nitrogen oxides and has no impact on the atmosphere. Based on the equivalent indicators of nitrogen oxides and boiler combustion efficiency, the secondary air opening of each layer shall not exceed 70%, and the upper secondary air opening and the perimeter opening of each layer shall be between 35% and 15% – 20% respectively.

2. Adjust the swing angle of the burner and the burnout air
It is very important to study the formation of nitrogen oxides in the low nitrogen combustion process and adjust the swing angle of the burner and the burnout air. Adjust the swing angle of the burnout air to make the furnace incline upward, which can not only avoid the deviation of the furnace temperature on both sides but also obtain a better swing angle to shorten the operation time. The optimization and adjustment of burnout air can increase the area of burnout air baffle according to the specific operating conditions while stabilizing the total composition of the boiler, so as to effectively control the emission of nitrogen oxides and fly ash parameters.

3. Adjust the oxygen content in the furnace
In fact, scientific adjustment of furnace oxygen content can also optimize the operation process of low nitrogen combustion. Control the oxygen content of furnace gas to avoid excessive nitrogen oxides. Under the condition of low oxygen content, the furnace will produce a small number of nitrogen oxides. The experimental results show that if the oxygen content in the furnace is too low, the fly ash combustibles will increase. Therefore, the oxygen content in the furnace should be scientifically controlled between 2.5% and 3.5%. In order to effectively control the NOx emission of thermal power plants, boiler combustion efficiency should also be considered.

4. Conclusion
The low nitrogen combustion transformation project of thermal power plant boiler has high technical content, high technical standards, high professional requirements, and a complex implementation process, which can significantly improve the boiler combustion efficiency, effectively control the emission of nitrogen oxides, and improve the daily work and service quality of thermal power plant. With the improvement of environmental awareness, relevant employees should protect the quality of the ecological environment, upgrade the low nitrogen combustion of the boiler according to the external conditions, make it meet the requirements of process production and social development, improve equipment performance, and achieve production and environmental benefits.