The principle of pulverized coal preparation refers to pulverizing the raw coal into coal powder whose particle size and moisture content are in accordance with the requirements of pulverized coal injection. Requirements from Blast furnace injection system to coal : particle size less than 74μm accounts for more than 80%, moisture is not more than 1%. According to the coal mill equipment can be divided into two kinds of ball mill milling process and medium speed grinding mill.
 

 

Usually improving the fineness of pulverized coal is to make the pulverized coal finer, which will make the coal easier to fire, burn more completely, lower carbon content in fly ash, reducing the possibility of secondary combustion; At the same time, the center of the furnace flame is relatively decreased, and the furnace efficiency is relatively high. However, to improve the fineness of pulverized coal, the power consumption of pulverizing system will increase, and the abrasion of coal grinding parts in the pulverizer will increase (especially the steel ball mill), which will increase the maintenance volume. Therefore, for the power plant, the commissioning unit will give the reference value of the coal amount and current in the normal operation of the coal mill according to the grindability coefficient of the design coal type.
 

 

According to the type of coal grinded, coal grinding process can be divided into bituminous coal milling technology, anthracite milling technology and bituminous coal and anthracite mixed milling process, the three processes are basically the same. Based on explosion-proof requirements, bituminous coal milling technology and bituminous coal and anthracite mixed milling process need to increase the following systems:

 

(1) Nitrogen system: used to inert the system atmosphere.

(2) hot stove flue gas introduction system: use the hot stove flue gas as dry gas to reduce the oxygen content of the atmosphere.

(3) monitoring system of O2, CO content in the system: When the system content of O2 and CO content exceeds a certain range, the system will alarm and take appropriate measures. Bituminous coal and anthracite mixed milling technology is increased with coal blending facilities to adjust the mixing ratio of bituminous coal and anthracite.

 

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