In order to obtain better combustion effect, improve boiler capacity and automate boiler operation, modern large-scale boilers generally use pulverized coal combustion. The raw coal transported from the mining area should be made into qualified pulverized coal for boilers, which needs to be crushed by coal. , clear iron parts, remove wood chips, secondary crushing, weighing and sampling, drying, grinding coal, separation and other steps. Combustion of pulverized coal: The pulverized coal produced by the pulverized coal preparation system enters the furnace through the pulverized coal burner. The burner is the main combustion equipment of the pulverized coal furnace. The burner has three functions: one is to ensure that the pulverized coal gas stream is quickly ignited after being sprayed into the furnace; the second is to make the first and second winds be strongly mixed to ensure the full combustion of the pulverized coal; and the third is to let the flame fill the furnace and reduce the stagnant zone. After the pulverized coal gas enters the furnace through the burner, the combustion process of the coal begins. The three stages of the combustion process are generally the same as the other furnace types. The difference is that the preparation phase and the combustion phase of the furnace before combustion are short, and the burnout phase is relatively long. The difficulty of coal being pulverized into pulverized coal depends on the structure of the coal itself. Due to the different structural characteristics of the coal itself, the mechanical strength and brittleness of various coals are greatly different, so the grindability is different. The grindability index indicates the difficulty of grinding coal into pulverized coal, and its significance represents the relative ease of grinding coal into pulverized coal on a special equipment. The practice of the power plant proves that as the moisture in the coal increases, the grindability index of the coal decreases and the coal output decreases. Pulverized coal is an irregular fine coal granule which is ground by coal mills. The average particle size is 0.05~0.01mm, and the particles below 20~50μm (micron) account for the majority. Since the pulverized coal particles are small and have a large surface, they can absorb a large amount of air and have a property which is not found in general solids - fluidity. The smaller the particle size of pulverized coal, the smaller the moisture content, and the better the fluidity. However, if the pulverized coal particles are too small or too dry, the pulverized coal self-flow phenomenon will occur, and the working characteristics of the coal feeder will be unstable. The adjustment operation of the operation causes difficulty. In addition, coal powder is oxidized by contact with oxygen, and spontaneous combustion of coal powder may occur under certain conditions. In the milling system, the pulverized coal is transported by the gas. When the mixture of the gas and the pulverized coal encounters the spark, the fire source is enlarged and a large pressure is generated, thereby causing the explosion of the pulverized coal. The fineness of pulverized coal used in boilers should be determined by the following conditions: In the case of combustion, it is desirable to grind the pulverized coal so that the amount of air supplied can be appropriately reduced, so that the loss of q2 and q4 is reduced; from the viewpoint of the pulverizing system, it is desirable to grind the pulverized coal. some, thereby reducing the consumption of grinding coal and metal consumption. Therefore, when selecting the fineness of pulverized coal, the sum of the above losses should be minimized. The total loss of small coal fines is called "economic fineness". It can be seen that for coal types with high volatile matter and flammability, or for relatively uniform milling equipment for grinding pulverized coal particles, and some intensified combustion boilers, the fineness of pulverized coal can be appropriately larger to save grinding. Coal energy consumption. Because of the different degrees of softness and hardness of various coals, their anti-wear capabilities are also different, so the economical fineness of each coal is also different.
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Improving the utilization rate of pulverized coal combustion
Coal powder fineness is an important property of pulverized coal, the pulverized coal, combustion in the furnace, the smaller the loss of incomplete combustion, and is conducive to stable combustion, but the milling system consumes more power consumption, equipment The amount of wear is also large. Conversely, the coarser coal powder, although less power consumption, is not conducive to fuel combustion and burnout. Therefore, in the operation of the boiler equipment, the appropriate fineness of the pulverized coal should be selected to make the mechanical incomplete combustion loss and the power consumption of the milling system. Therefore, in the boiler system, the appropriate fineness of the pulverized coal should be selected to make the mechanical incomplete combustion loss. The sum of the power consumption of the system and the milling system is the smallest, and the fineness of the pulverized coal at this time is called economic fineness.