Graduation design of low-load stable combustion technology for utility boilers. Urgent.

WR burner is equipped with a wave-shaped expanding cone in the pulverized coal nozzle. When the pulverized coal-air mixture flows through this wave-shaped expanding cone, a stable reflux zone is formed at the downstream of the expanding cone, that is, at the outlet of the burner, and the high-temperature flue gas continuously flows back into the reflux zone to maintain the stable ignition of pulverized coal. This is a very effective measure. The once-through burner is arranged in the furnace in a tangential combustion mode with four corners, and the four-corner jet is tangent to an imaginary tangent circle in the furnace, so that the jet rotates and ascends in the furnace. In this way, not only the high-temperature flue gas swept by the adjacent angle jet is used to help the fire, but also the rotating and rising airflow accelerates the disturbance and mixing of pulverized coal and air, which is beneficial to the burning of pulverized coal. 2) Improving the initial temperature of pulverized coal airflow by hot air feeding and higher preheating air temperature can reduce the fiery heat and speed up the ignition. Therefore, the pulverized coal furnace pulverizing system burning inferior coal that is difficult to ignite should widely adopt the hot air feeding system with intermediate storage bin, and use hot air with higher temperature instead of exhaust gas with lower temperature as primary air, and at the same time adopt higher preheating air temperature. 3) Increase the temperature in the burner area, and the pulverized coal airflow will ignite in the burner area, so increasing the temperature in the burner area can accelerate the ignition of coal. The widely adopted measures are as follows: 1. Adopt appropriate thermal intensity in the burner area. 2. Laying the burning zone in the burner area to reduce the heat absorption of the water wall in this area and correspondingly increase the temperature in this area is an effective measure to burn low volatile coal, but it should be noted that the location and quantity of the burning zone should be appropriate, otherwise it will cause slagging. In addition, the burning zone is easy to fall off and become thinner under the action of high temperature flue gas in the furnace, so it should be repaired in time during maintenance. 4) Using lower primary air rate and primary air speed to reduce the primary air rate will reduce the ignition of pulverized coal airflow, which is beneficial to ignition. For solid slag-discharging pulverized coal boilers burning anthracite, the primary air rate is within the range of 2%-25%, and the primary air speed is also controlled accordingly, usually within the range of 2-25m/s.. In order to reduce the local primary air rate in the pulverized coal air flow, a high-concentration pulverized coal burner with dense and weak separation is usually used, so that a part of the pulverized coal air flow ejected from the burner outlet has a high concentration, and the corresponding primary air rate is lower here, which greatly reduces the ignition heat required by the pulverized coal air flow in this local area, thus speeding up the ignition of pulverized coal here, accelerating the ignition in local areas, and contributing to the stable ignition of the whole pulverized coal air flow. At the same time, we should also pay attention to the mixing of primary air and secondary air later, and the mixing should be after the primary air pulverized coal airflow catches fire, otherwise it will increase the primary air rate accordingly, which is not conducive to fire. 5) Fine pulverized coal fineness with smaller pulverized coal particles is helpful to the ignition, combustion and burnout of low volatile coal. Therefore, the fineness of pulverized coal must be strictly controlled in operation, and the most suitable fineness of pulverized coal should be obtained through combustion adjustment experiments. 6) The load of boiler operation should not be too low. In the case of boiler operation, the minimum load should not be lower than the minimum stable combustion load considered in the design, otherwise the ignition and combustion of coal will be unstable due to the low load and low temperature level in the furnace, and may even turn off, or to stabilize the ignition and combustion, oil must be used for combustion.