With the introduction and implementation of new domestic environmental protection standards, power plants, as an important project of low nitrogen combustion renovation, have responded positively to calls for low nitrogen rectification. The low nitrogen combustion retrofit activities of the power plant have greatly improved the operation efficiency of the power plant to a certain extent, and also have a positive effect on the environmental protection of the power production activities of the power plant. The structure of low-nitrogen burners in power plants is complex and the matching requirements of various parts are high. therefore, we need to accurately grasp the structure of low-nitrogen burners in power plants and lay a solid foundation for subsequent rectification work.
1, the main bellows external equipment
The external equipment of bellows is mainly composed of igniter control cabinet, oil igniter and fire detector. All air nozzles and fuel nozzles in the bellows device are connected to the electric tilt drive unit by connecting rods outside the bellows and can adjust the tilt angle in the vertical direction. The tilt drive adjustment of the four corners of the hearth in the bellows is synchronous, ensuring that all nozzles are the same in terms of tilt angle. While the relative position of fireball in the hearth can move up and down by synchronizing the inclination of all nozzles. The degree of opening and closing of the air door is controlled according to a preset program, and all the air doors are driven by an electric drive device.
2. inner bellows structure before renovation
Before the reformation of the low nitrogen burners in the power plant, there were four air boxes at each of the four corners of the furnace. the equipment in these air boxes sent fuel and wind to the furnace to ensure the control of the fuel and air volume in the furnace. The inside of each air box is divided into nine small air chambers, which are respectively provided with secondary air nozzles or pulverized coal burners. Each air box has its own independent action control system, which uses flap doors to control the air volume and fuel volume entering the furnace. the flap doors of the four corners on the same floor are synchronized, so the air volume entering the four small air chambers is consistent and the fuel in the furnace can be fully combusted. The flap door can be adjusted to different opening and closing degrees in different layers, so that the amount of fuel and air delivered to the bellows will be different. The wind speed of the secondary air generated in different small wind chambers can be controlled according to some operating parameters, such as the amount of coal supplied and the differential pressure between the bellows and the furnace.
3. air distribution inside the air chamber
The fuel wind is also called perimeter wind or tertiary wind, and the wind source comes from the large secondary wind bellows. It is located close to the pulverized coal nozzles and plays a role in accelerating and mixing the pulverized coal flow and cooling the pulverized coal nozzles. each pulverized coal nozzle is equipped with a fuel plenum, which is generally controlled by the coal supply quantity of this floor. The auxiliary air is mainly the secondary air entering the hearth through the small air chamber between the nozzle layers of the two-layer pulverized coal burner. it is the air term that regulates the combustion efficiency in the hearth. The differential pressure between combustion pressure and air volume in the furnace can be controlled by adjusting the opening and closing degree of these " combustion control dampers" ( flap doors controlling auxiliary air ). Other fuels and oxygen can be ensured to enter through adjusting the opening of the air door and the air inlet quantity of the hearth.