Low speed coal mill

Is mainly drum-type steel ball coal mill, generally referred to as steel ball mill or ball mill. It is a rotating cylindrical or tapered roller with steel balls in the roller. The rotation speed of the drum is 15-25 rpm. When working, the steel ball in the cylinder continuously hits and squeezes the coal block, and the coal block is ground into pulverized coal. Then the coal is dried by the hot air flowing into the drum and the pulverized coal is sent out. After being separated by the separator, the pulverized coal with a certain particle size is sent to the pulverized coal silo or directly to the pulverized coal burner. The steel ball mill is heavy and bulky, has high power consumption and high noise; but it has a wide range of adaptability to coal types and reliable operation, and is especially suitable for grinding hard anthracite.

Medium speed coal mill

The speed is 50-300 rpm, and there are many types. The common ones are flat disc mills, bowl mills, E-type mills and roller mills (Figure 2). Their common feature is that the grinding parts are composed of two groups of relative moving grinding bodies. The coal lump is crushed by being squeezed and milled between the surfaces of the two sets of milling bodies. At the same time, the hot air fed into the coal mill dries the coal and sends the pulverized coal to the separator in the upper part of the milling zone. After separation, the coal powder of a certain particle size is carried out of the mill with the air flow, and the coarse coal powder is returned to the grinding area for regrind. The medium-speed coal mill has significant advantages such as compact equipment, small footprint, low power consumption (about 50 to 75% of steel ball mill), low noise, and relatively light and sensitive operation control; but

The structure and manufacturing are more complicated, the maintenance cost is higher, and it is not suitable for grinding harder coal. The bowl-type medium-speed mill is more used in large-capacity coal-fired boilers.

High-speed coal mill

The speed is 500～1500 rpm, mainly composed of high-speed rotor and grinding shell. Common ones are fan mill and hammer mill. In the fan mill (Figure 3), the coal blocks are impacted by the high-speed rotor at high speed and collide with the grinding shell, and the coal blocks collide with each other to be ground. The coal pulverizer and the pulverized coal separator form a whole, with simple structure, compactness, and low initial investment. It is especially suitable for grinding high-moisture lignite and bituminous coal with high volatile content and easy to grind. Due to the large wear and tear of the fan mill, the continuous operation time is shorter than that of other coal mills, so it is not suitable for grinding hard coal.