The History of Raymond Mill1906 C.V. gruber founded Curt Von Grueber Machinery Factory in the southern suburbs of Berlin, and used his patents obtained in the United States to produce the first Maxecon mill, which was used as coal grinding equipment in MOABIT Power Station in Bevage, Berlin. The grinding energy can reach 5T/H, and nearly 600 sets are sold in a few years, which are used in grinding fields of different industries. During the same period, BEWAG plans to build a coal mill with higher output. After E.C.Loesche became a shareholder and took charge of Curt Von Grueber Machinery Factory, he decided to purchase the raymond centrifugal ring roller mill patent published by the United States and produced the first generation raymond mill system. Its structure is that a rotating spindle with a plum blossom frame is erected in the center of the machine, and three or more self-rotating grinding rollers are hung on the plum blossom frame. The rotating shaft rotates at a certain speed, which drives the grinding roller to swing outward, and is driven by centrifugal force to press against the grinding ring embedded in the inner wall of the cylinder. When the material enters the grinding area, the material is brought to the front area of the grinding roller under the action of plow-shaped guide blades below the grinding roller. Because the grinding force (centrifugal force) of Raymond mill roller is limited by the diameter and speed of the roller, the mill at that time was only suitable for soft, low ash and good grindability coal, while Germany's coal quality was hard and high ash, which required higher grinding force. Raymond mill with this structure is difficult to meet the grinding requirements, so Raymond mill has not been popularized in Germany. At that time, Raymond coal mill was just suitable for the grinding requirements of coal quality in the United States, so Raymond coal mill was widely popularized and applied in the United States.
1925 E.C.Loesche summarized the use characteristics and structural shortcomings of the first generation Raymond mill, decided to further improve the grinding structure of Raymond mill, and developed a mill with the opposite grinding principle, called improved Raymond mill. The main structural feature is that the bowl-shaped grinding ring rotates, the grinding roller is pressurized by the mechanical spring load to increase the grinding force, and the material is fed into the bowl-shaped grinding ring from the center and brought into the grinding roller by the rotating centrifugal force. The roller shaft of the grinding roller is fixed on the rocker arm which can move in one direction, and the grinding force of each rocker arm is controlled by an adjustable spring. The ventilation of this improved Raymond mill system has two ways: positive pressure and negative pressure direct blowing. This type of Raymond Mill patent was quickly purchased by American Combustion Engineering Company. Because the improved raymond mill still has the problem of ring roller grinding, although the roller diameter increases slightly, the grinding force does not increase much. Later, Raymond Branch of American combustion engineering company developed a new generation of Raymond mill called VR mill. This Ramon mill is similar in structure to Lacey mill in many aspects. It is worth noting that it is different from the conical grinding roller and plane grinding disc of Lech mill, but adopts cylindrical grinding roller and grinding disc, and the grinding surface is inclined at an angle of 15 degrees. In the process of inspection and maintenance, the grinding roller has an eversion device similar to Lecher mill, and it is also equipped with a protective device to prevent metal contact between the grinding roller and the grinding disc. In addition, the grinding roller can be raised in advance before the mill starts, which can reduce the starting torque of the motor. Raymond mill is usually used to prepare pulverized coal in industrial applications in the United States. The fineness of products varies from 250 mesh to 325 mesh, and the fineness and output of products can be adjusted during operation. Hardness and Mohs hardness
Hardness: Because it is a destructive test, it can only be used for unpolished rough stones or cheap ores. There are two scales of hardness, one is absolute hardness and the other is Mohs hardness (a relative hardness).
Mohs hardness: based on ten common minerals, we can distinguish which is hard and which is soft by scraping each other. Traditionally, Mohs hardness is used in mineralogy or gemology.
Mohs hardness is divided into ten grades. Talc, gypsum, calcite, fluorite, apatite, orthoclase, timely, topaz, corundum and diamond.
The purpose is to generally characterize that pore size of molecular sieve, and the conversion formula is as follow:
Cm= 16/ mesh
There are English and American orders. English refers to how many holes there are per square inch.
Comparison between new superfine Raymond mill and traditional Raymond mill: Raymond mill, also known as Raymond mill, mill, Raymond mill and high-pressure roller mill, is a widely used grinding equipment. Raymond mill is a kind of grinding equipment widely used in mines, cement plants and chemical plants, and it is one of the important equipment for deep processing of nonmetallic minerals. Raymond Mill was introduced to China for more than 20 years. Because of its stable performance, strong adaptability and high cost performance, it has been widely used in non-metallic mineral processing. However, with the extensive development of nonmetallic minerals in the application field of ultrafine powder, downstream enterprises have higher and higher requirements for nonmetallic minerals. In particular, the requirements for product fineness are higher. This makes the traditional Raymond Mill seem inadequate. These problems in traditional raymond mill have been puzzling mineral processing enterprises and equipment manufacturers. These problems are mainly manifested in:
1. The fineness of the product is low, and the fineness of ordinary Raymond mill is generally below 500 mesh. These devices can only occupy the lower-end powder application market.
2. High mechanical failure rate, high power consumption, high noise and high emission pollution.
3. The efficiency of the system is low, the separation effect of the product collection system is not ideal, and a large amount of fine powder can not be effectively collected, which leads to the repeated circulation of the system and the waste of electric energy.
4. There is an error in the air duct design of the main engine bellows. The larger particles in the materials entering the grinding area and the particles that have not been ground before are often thrown into the bellows to gather at the tail of the worm box and continue to extend forward, so that the excessive air volume is gradually reduced, which is easy to cause traffic jams, no powder or less powder, and affect the output. According to the processing technology of ultrafine powder equipment mastered for many years, people have carried out comprehensive and thorough technical innovation on the above problems. When using the traditional raymond mill, it is found that there are a lot of 10um ultrafine mineral powder in 325 mesh mineral powder when processing calcite mineral powder in raymond mill. If it can be separated and expanded, the benefits will be greatly improved. To this end, the structure of raymond mill has undergone many innovations:
The traditional way of the main engine is improved, and the spindle and quincunx frame are transformed into stable structures to make it run smoothly.
There is no swing in the middle. The traditional part of the analyzer was changed from dragging in the cavity to hanging outside the cavity, and the rotation in the cavity was isolated, which enhanced the stability and durability. In the grinding area, the ground materials always gather in the grinding area for effective treatment, which improves the grinding efficiency. We also updated the structure of the grinding roller, so that the grinding roller wheel and the grinding roller shaft can run complementarily. It can also revolve while rotating. Make it more effective and lasting. And can work at higher grinding force and higher running speed. In the ventilation part, the bellows and air duct are changed from the flat bottom of raw water to 30 degrees inclined to the center, forming a bucket shape, which ensures that the bellows and air duct are always unimpeded and not blocked, so that the air volume is always needed, and the grinding efficiency of the main engine is high. In the whole system design, the traditional two-level acquisition is changed to four-level acquisition. The primary and secondary collection are locked by circulating negative pressure, and there is no dust overflow. The third and fourth grade collection adopts controllable overflow dry-wet series collection to prevent dust overflow. The whole system not only collects ultrafine powder, but also eliminates or reduces the pollution to the surrounding environment.
The new raymond mill can be used for superfine grinding of calcite, dolomite, talc, aged soil, barite, rutile, fluorite and other nonmetallic minerals. The practice shows that when the fineness of calcite with a feed particle size of 25mm is adjusted to 1250 mesh (10um), the output can reach 450kg/h, and the input power is only 23kw, which is obviously more cost-effective than the traditional raymond mill.