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Professional Design Rod Grinding Mill

Professional Design Rod Grinding Mill

Rod Grinding Mill For Sand Making, Causing High Stone Powder

At present, there are many sand-making equipments on the market that have vertical shaft impact and tower-type dry sand making systems, and users of Rod Grinding Mills are gradually reduced. However, there are still some users who use Rod Grinding Mills for sand making for price or other factors.

In China’s current sand and gravel related specifications, the content of artificial sand is controlled to be 6%-12%, the mud content is <3%, and the water content is <5%. When the sand is artificially produced by a Rod Grinding Mill, the content of the stone powder in the sand is not low or even high. Especially when the raw material rock is brittle and the fineness modulus of the sand is small, the stone powder content is particularly high, and sometimes the stone powder content in the discharge material is as high as 30%, and the stone powder in the finished sand often exceeds the standard. Excessive stone powder will increase the loss, the sanding rate will decrease, and the stone can not be fully utilized. The high content of stone powder in the finished sand will prolong the dehydration time of the sand, increase the volume of the sand bin, and it is easy to be in the process of dehydration. “Consolidation”; excessive stone powder content will increase the amount of cement used in concrete and even reduce the performance of concrete. So, what is the reason for the high stone powder when using the Rod Grinding Mill?

The Proportion Of Steel Bars Slipping And Lax

The Rod Grinding Mill grinds the material by the movement of its grinding medium steel rod. Steel bars in the same Rod Grinding Mill typically have three different forms of motion, while steel bars moving in different forms will impart different effects to the material. When thrown off, the steel bar is separated from the wall at a higher position, falls along the parabolic trajectory, and smashes into the simple coarse material, and smashes the coarse material into pieces of different sizes with great impact force. When the steel rod falls, the upper steel rod rolls down step by step along the lower steel rod. At this time, it grinds the debris and gives an impact to further break into smaller particles. When the steel rod is slipped, the steel rod only causes grinding due to relative sliding or rolling of itself.

Although the impact of steel throwing is very large, it is not the main reason for over-grinding of the material. This is because the rock mass will greatly increase the breaking strength under the impact of rapid impact, and may reach its static strength. Several times. The rock mass is brittle under impact. This damage is mainly caused by the destruction of existing fragile surfaces inside the rock mass, and the number of these fragile surfaces is limited; the impact of the throwing steel rod on the rock mass is instantaneous and one-time. When the rock breaks into debris, it falls into the gap between the bars and the gap between the coarse rock blocks, thus avoiding the re-impact of the throwing steel bar.

Sliding and sloping are different, and they all work on cuttings that have been crushed to a certain extent. Although the former accounts for a small proportion, the cuttings are placed in the gaps of a few layers of steel bars close to the lining when they are placed away from the landing zone of the steel bar, and the steel bar on the top is heavily loaded. At this time, the steel bar has a large pressure on the rock block and the grinding effect is strong. Although the diarrhea only occurs on several layers of steel bars on the surface, the cuttings are subjected to a small weight. However, at this time, the steel bars have both impact and grinding, which makes the compressive stress and shear stress in the cuttings higher. Since the shear strength of the cuttings is much lower than the compressive strength, the cuttings are more likely to be cut, and the steel bars have more effect on the cuttings and have a longer acting time. More importantly, under actual production conditions, diarrhea accounts for the largest proportion, so sloping and slipping are the root causes of excessive smashing.

Small Rod Diameter

There are strip gaps between the steel jaws of the Rod Grinding Mill, which can timely receive the debris that has been broken to a certain extent. It is prevented from being hit again by the steel rod when it is thrown off, and the particles which have reached the fineness requirement are flushed out of the cylinder by the water along the slit, so that the rod slit can play a certain “screening” effect. Obviously, if the cross section of the rod is large, the debris it receives will be coarse, and the fine particles in the crumb will be less likely to be ground, and the over-grinding phenomenon will be light. On the contrary, the over-grinding will increase. Under normal production conditions, the steel grip wears continuously, its diameter gradually becomes smaller, and the joint of the rod becomes smaller accordingly. However, these steel bars that have been ground to a certain extent are often not detected in time during operation. In this way, although the new sticks are added regularly, the grading of the steel holdings is often too fine.

Material Residence Time Is Too Long

After the rock block enters the cylinder of the Rod Grinding Mill, it is first crushed into scraps under the impact of the throwing steel bar, and then further pulverized under the impact and grinding action of the sliding and falling steel bars. Obviously, if the material that is ground to the desired particle size can be discharged out of the cylinder in time, the over-grinding phenomenon will be greatly reduced. Otherwise, the material is repeatedly subjected to the grinding of the steel rod, and once broken, it will inevitably form more stone powder. It can be seen that the material stays in the cylinder for too long, that is, the grinding time of the steel rod is too long, which is also an important cause of excessive pulverization.

At present, Rod Grinding Mills for sand making are generally wet intermediate peripheral discharge type. This Rod Grinding Mill relies on hydraulic discharge. Obviously, if the flow rate of water is large, the sand blasting ability is strong, and it is easy to flush out the fine materials. However, if the flow rate of the water is too large, the sand blasting ability is too strong, and a part of the coarse particles will be taken out to form a super-path phenomenon. . In order to avoid this, the amount of water added has to be reduced in production. As a result, the slurry concentration tends to be higher, often above 70%, making it an important cause of over-grinding.

Feed Amount

In the production process, the fineness modulus of the sand is generally controlled by the amount of feed. Thus, in the production of sand with a small fineness modulus, the Rod Grinding Mill tends to feed less. At this time, because the effective volume of the material in the simplified body is reduced, under the other conditions, the impact force and the grinding force per unit volume of the material will increase, that is, the actual crushing work of the material increases, so it is easy The actual crushing ratio is too large, causing more serious over-grinding.

When grinding different rocks with a Rod Grinding Mill, in order to ensure that the fineness modulus of the finished sand meets the requirements, the excessive pulverization of the sand and the processing capacity of the Rod Grinding Mill are minimized.

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