Research and Development of The Fly Ash Grinding Mill
Experiments have proved that the mechanical pulverization/grinding method is very effective for the coarse ash activity. With the help of fly ash grinding mill, the coarse and porous glass body is crushed, the glass particles are released from bonding, the bead particles are increased, the particles themselves have less pores, the surface property is improved, the friction during the mixing process is improved, and physical activity is also increased. When grinding, the solid protective film is destroyed, so that the internal soluble SiO2, Al2O3 is dissolved, and specific surface area and the chemical activity are also increased.
With the help of fly ash grinding mill, the coarse fly ash is ground into fine powder, which not only can increase the activity of the fly ash, but also reduce the water demand ratio. So the fly ash can be made full use. For example, fly ash improves concrete performance mainly due to the presence of 10 ~ 40μm particles. Long time ago, the fly ash had been put into the cement clinker to improve the cement quality. Due to the different abrasiveness of fly ash and clinker, the particles of cement are relatively coarse (80 μm). Fly ash is not fine enough to make full use of its activity. In addition, there are also a small number of users who grind fly ash directly with cement in the grinding mill. Due to the different chemical composition of fly ash and cement, the physical properties are quite different, and the grinding ratio is also very different, which bring low grinding efficiency, high power consumption, low output and high grinding ash cost.
According to the characteristics of fly ash, a special ultra-fine grinding mill for fly ash is used. The ball grinding mill is a very mature equipment with a history of more than a hundred years, it has grinding body, grinding ball, bearing support and driving device. In this article, we put more focus on its internal structure.
Grinding ball or grinding rod
The size, shape and gradation of grinding ball or grinding rod are the keys to grinding efficiency and the final fineness and particle gradation. We tested spherical, ellipsoidal, rod-shaped, truncated cone and other forms of grinding bodies to determine the appropriate shape of the grinding body. The maximum ball diameter is related to the particle size, hardness, and product fineness of fly ash. There are many calculation formulas, and the calculation results are also different. Through experimental comparison, and through a 1.8m grinding mill, the actual maximum ball diameter is 16 mm. The gradation of the grinding body is adjusted according to the shape of each fly ash and the target fineness of the final product. Ball diameter is between 4 ~ 16 mm.
Because input fly ash size is very small, the factor that influence grinding is not the impact force, it is grinding times. The special fly ash grinding mill for fly ash uses micro-abrasive bodies as the grinding medium. The number of grinding bodies is about 20 times that of ordinary steel sections. Therefore, the number of grinding times for fine powder is increased, and the grinding effect is greatly enhanced; at the same time, the surface area of the grinding body is increased. It also improves grinding efficiency.
Classifying and Activating Device:
The special grinding mill for fly ash uses micro-abrasive bodies to achieve the purpose of grinding fly ash. The internal structure of a conventional cement mill cannot be adapted to such an abrasive body without modification.
Generally, the fly ash grinding mill is provided with a coarse grinding chamber and a fine grinding chamber. When the fly ash enters the fine grinding bin from the coarse grinding bin, then firstly sorted by a screening device, and the screening device returns the coarse powder to the coarse grinding bin, and the fine powder enters the fine grinding bin. As the screening device selects the fine powder in time, the coarse powder content of the coarse grinding chamber increases, and the fine powder content decreases. The sieving device, like the powder separator of the closed circuit system, can separate materials with qualified particle size.
After the micro-abrasive body is used, due to the more inlaying and entrainment between the layers of the abrasive body, the relative sliding between the abrasive bodies is less, and the exchange and transfer between the layers is difficult to occur, that is, an abrasive body is retained. Belt, is extremely detrimental to grinding efficiency and quality. In order to eliminate this retention zone, an activation device was designed and penetrated into the retention layer. With the rotation of the grinding mill, the activation device broke up and destroyed the retention zone, so that all the micro-abrasive bodies gained energy and participated in the grinding. , Greatly improve the grinding efficiency.