How do I choose a coal grinding machine?

The coal grinding machine is an important part of the pulverizing system of the power plant and an important auxiliary power equipment of the power plant. Its main task is to break the coal into pulverized coal and provide it to the boiler equipment. The quality of its configuration will directly affect the performance of the unit, safety and economy. Because different coal mills have great differences in adaptability to different coal types, the quality of coal products will directly affect the economical efficiency of pulverizing system operation. So, how to choose a coal grinding machine?

There are many types of coal grinding machine. According to the speed of coal grinding working parts, coal mill equipment can be divided into three types, namely: low-speed coal mills, medium-speed coal mills and high-speed coal mills. The selection of these three types of coal grinding equipment will be introduced separately below.

1: low speed coal mill

A typical representative of a low-speed coal mill is a ball mill. Its working principle is: the high-power motor drives the heavy circular block to rotate through the gearbox, and the steel ball inside the block is rotated to a certain height and then falls down. Pressing between the plates grinds the coal down. The unqualified coal powder that is too coarse is separated when it flows through the coarse powder separator at the rear of the ball mill, and then sent from the powder return pipe to the cylinder for re-grinding. In addition to conveying coal powder, hot air also plays the role of drying coal, so hot air is also called desiccant in the pulverizing system. This product has the characteristics of long continuous operation time, easy maintenance, stable output and fineness, large storage capacity, quick response, high operating flexibility, low air-to-coal ratio, saving spare coal machines, and a wide range of ground coal types. It is mainly used for It is suitable for hard and medium hardness coal, especially for coal with high volatile content and strong abrasiveness. But this kind of low-speed ball mill is heavy, consumes a lot of metal, occupies a lot of land, and has high initial investment. The ball mill is suitable for full-load operation.

2: medium speed coal mill

The medium-speed coal mill is also called a vertical coal mill, and its characteristic is that the grinding part is composed of two groups of relatively moving grinding bodies. The coal block is squeezed, ground and pulverized between the surfaces of the two sets of grinding bodies. At the same time, the hot air passing through the coal mill dries the coal and sends the coal powder to the separator in the upper part of the grinding area. After separation, the pulverized coal with a certain particle size is taken out of the mill with the airflow, and the pulverized coal with coarse particles returns to the grinding area for regrinding. The medium-speed coal mill has significant advantages such as compact equipment, small footprint, low power consumption (about 50%~75% of the steel ball mill), low noise, and relatively light and sensitive operation control; but it is not suitable for grinding hard of coal.

3: high-speed coal mill

The speed of the high-speed coal mill is 500~1500 r/min, and it is mainly composed of a high-speed rotor and a grinding shell. The common ones are fan mill and hammer mill. In the mill, the coal blocks are crushed by high-speed impact and the impact of the grinding shell and the collision between the coal blocks. The coal pulverizer and the pulverized coal separator form an integral body, which has a simple and compact structure and low initial investment, and is especially suitable for grinding high-moisture lignite and bituminous coal with high volatile content and easy grinding. However, due to the serious wear and tear of the impact plate directly by the airflow, when grinding lignite, its service life is generally only about 1000h, and the replacement is frequent, and the moisture content of the coal to be ground should not be too high. Boilers are not suitable for use in blast furnace injection workshops.

The selection of the above three types of coal grinding equipment has its own advantages and disadvantages. When selecting the type of coal grinding equipment, it is necessary to consider the selection of the pulverizing system as a whole.