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By Hubery Editer
As we all know, ball mill is the key equipment for grinding materials after crushing, which is indispensable in beneficiation plant, metallurgy, chemistry, cement and other fields.
However, how to improve the ball mill efficiency has always been an important subject for engineers as well as a mattered issue to investors.
After consulting Fote engineers and having a reference, here five methods are sorted out for the improvement of ball mill efficiency and the materials utilization rate. This can reduce the energy consumption and the use cost of the ball mill.
To make the milling more efficient, we must first be acquainted with the factors. They are mainly the ball mill structure, the rotation speed, the ball mill media, the lining plate, the material fed and the feeding speed, etc.
In the following text, you will get some details on how to improve the grinding efficiency of the ball mill from the above aspects.
Here the structure means the ratio of ball mill length to its diameter. According to the industrial tests, the capacity varies with the ball mill types; Even from the same type of ball mill, the energy consumption and milling efficiency are different.
One of the factors is the function of the diameter and length. The length of the ball mill affects the discharge fineness. If the cylinder is too short, required fineness cannot be reached; while if it is too long, the materials are over ground resulting in a waste energy consumption.
Therefore, the ball mill length shall be designed appropriately, so is the diameter. In this way, the ball mill efficiency is improved with an appropriate crushing and energy consumption.
Ball mills of different length and diameter
The theoretical ratio of length to diameter is between 1.09 and 1.5. While according to different requirements, customers get customized ball mills with different ratios of length to diameter.
A suitable rotation speed of the ball mill cylinder helps to make full use of the impaction and grinding from the grinding media. It improves the ball mill efficiency greatly.
The cylinder cannot rotate at a too high or too low speed. The following picture shows the difference clearly.
What different rotation speeds result in
If the speed is too low, the grinding media are poured down, which results in a "gentle" grinding from the ball mill. Powerful impaction and grinding cannot be produced.
While if the speed is too high, the grinding material moves with the grinding media along the inner cylinder. Then the grinding media and material become "close friends", which also can't produce a high grinding efficiency.
Only when the cylinder rotates at a designed speed, the grinding media are thrown down at a suitable point. With the slide, the grinding media produce an efficient impaction and grinding to the material.
As a part of direct contact with the material, grinding media is an important factor to improve the ball mill grinding efficiency. The efficiency of the ball mill can be improved mainly from two aspects: the proportion of different sized grinding media and timely media refilling.
The proportion of different sizes of grinding media includes the size and quantity of media. Normally, the ball mill grinding media are shaped into balls with appropriate materials, of which the most used material is steel.
Ball mill grinding media made of different materials
For different grinding requirements, the proportion of steel balls with different diameters is different. Larger diameter steel balls are mainly used for crushing, while smaller ones are used for grinding.
If the bigger steel balls take a larger proportion, the impact force generated by the steel balls falling causes more damage to the liners and the steel ball consumption is increased. While if smaller steel balls are more than bigger ones, the material gets more buffering effect. And the grinding efficiency is decreased.
Therefore, an appropriate proportion of different sizes grinding media is very important. According to the feeding size, if there are more large materials in the cylinder, operators should load more large steel balls. If there are more small materials, then the reverse.
In the grinding process, the wear of the media is inevitable, so it is necessary to timely refill the steel balls. The ratio of supplemented steel balls should also be controlled. If the grinding media are not accurately added, they will be easily stuck in the cylinder and damage the machine. To accurately add steel balls, experts give some suggestions:
Working site of ball mill grinding media refilling
In addition to the grinding media proportion and frequency, other factors such as the grinding media material, the shape and so on can improve the ball mill efficiency. Consult a professional engineer for details.
The optimized grinding media can improve the ball mill efficiency by about 30%.
The lining plate is another part that direct contact with the material.
The liner made of ordinary material is too thick, which will reduce the effective volume of the ball mill cylinder. Besides, thick liners increase power consumption due to the large weight and reduce the production efficiency of the ball mill. So how to choose a hard material to make thin but durable liner is an important issue.
Based on experience and experiments, this material can be high manganese steel. High manganese steel is very wear-resistant, and the surface hardness of the liner made by it can reach HV500. Such material can increase the liner wear resistance, and the effective volume of the cylinder to improve the ball mill efficiency.
Besides, the shape of the liner can affect the ball mill efficiency. Fote Machinery, for example, provides customers with a corrugated liner, which greatly enlarges the contact surface area of the grinding media and materials, enhances the grinding effect, and gets good feedback.
Ball mill with corrugated liners
Controlling material feeding refers to feeding size and feeding speed. To control the feed size, “more crushing and less grinding” is a good principle. Feeding speed means to send the material into the ball mill cylinder at a moderate speed.
The researches show that the ball mill efficiency is also related to the feeding size. The larger the feed size, the longer the time needed to grind the material to needed fineness, the more power consumption, and the lower the efficiency.
The crushing efficiency is higher than the grinding efficiency, so a crusher can be equipped before grinding. Such crusher can be a jaw crusher with a large crushing ratio and an extensive application, or a roll crusher that can increase ore micro-cracks through lamination crushing.
Jaw crusher is used to work with ball mill to reduce the feed size
But it is not that the thinner, the better. The too-small material size will reduce the efficient grinding. Generally, the feeding size is controlled between 25 and 15mm (the feed size is affected by the ball mill diameter).
When the material is fed too slow, idling easily happens. This not only results in excessive crushing, wasting energy consumption but also causes serious wear to the lining plates and grinding media. If the material is fed too fast, material accumulation happens easily, which seriously affects the grinding effect and reduces efficiency.
Therefore, moderate feeding speed can ensure full contact between grinding media and materials, improving the ball mill efficiency and reducing energy consumption.
Chart of suitabl feed speed of ball mill
The above are the five most used ways to improve the ball mill efficiency. While two more things are often overlooked. They are choosing the right model and doing regular maintenance.
A good start will get you twice the result. For different materials, the engineer will provide different types of ball mill. Maintenance is the escort for improving the ball mill efficiency. Timely maintenance can remove the trouble to ensure that a last-minute glitch won't happen.
At the gold ore beneficiation site, the Tanzanian customer selected a suitable gold ball mill and does regular maintenance.
Compared with other ball mills that used for the same period, his ball mill grinding efficiency is higher by about 25%. At present, the capacity of the gold ball mill is 180TPH, the particle size of the feed is controlled at about 20mm, and the output easily reaches 200 mesh.
Gold ore working site
Professional things should be left to professional people. On how to improve the efficiency of the ball mill, the professional ball mill manufacturer, Fote Machinery is very ready to offer you solutions. Please feel free to consult our professional engineers online or send an email to quote@sinoftm.com.
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