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what are the differences between ball mill and rod mill? | fote machinery

what are the differences between ball mill and rod mill? | fote machinery

Ball mill and rod mill are the common grinding equipment applied in the grinding process. They are similar in appearance and both of them are horizontal cylindrical structures. Their cylinders are equipped with grinding medium, feeder, gears, and transmission device.

The working principle of ball mill and rod mill machine is similar, too. That is, the cylinder drives the movement of the grinding medium (lifting the grinding medium to a certain height then dropping). Under the action of centrifugal force and friction, the material is impacted and ground to required size, so as to realize the operation of mineral grinding.

Grate discharge ball mill can discharge material through sieve plate, with the advantage of the low height of the discharge port which can make the material pass quickly so tha t to avoid over-grinding of material. Under the same condition, it has a higher capacity and can save more energy than other types of mills;

It is better to choose a grate discharge ball mill when the required discharge size is in the range of 0.2 to 0.3 mm. Grate discharge ball mill is usually applied in the first grinding system because it can discharge the qualified product immediately.

Overflow discharge ball mill can grind ores into the size under 0.2 mm, so it is very suitable for the second grinding system. The capacity of it is about 15% lower than grate discharge ball mill in the same specification, and the loaded grinding medium is also less than that one.

It can be divided into three types of rod mills according to the discharge methods, center and side discharge rod mill, end and side discharge rod mill and shaft neck overflow discharge rod mill.

It is fed through the shaft necks in the two ends of rod mill, and discharges ore pulp through the port in the center of the cylinder. Center and side discharge rod mill can grind ores coarsely because of its structure.

This kind of rod mill can be used for wet grinding and dry grinding. "A rod mill is recommended if we want to properly grind large grains, because the ball mill will not attack them as well as rod mills will."

It is fed through one end of the shaft neck, and with the help of several circular holes, the ore pulp is discharged to the next ring groove. The rod mill is mainly used for dry and wet grinding processes that require the production of medium-sized products.

The diameter of the shaft neck is larger than the diameter of the feeding port about 10 to 20 centimeters, so that the height difference can form a gradient for ore pulp flow. There is equipped with a spiral screen in the discharge shaft neck to remove the impurities.

It has high toughness, good manufacturability and low price. The surface layer of high manganese steel will harden rapidly under the action of great impact or contact. The harder index is five to seven times higher than other materials, and the wear resistance is greatly improved.

It has high toughness, good manufacturability and low price. The surface layer of high manganese steel will harden rapidly under the action of great impact or contact. The harder index is five to seven times higher than other materials, and the wear resistance is greatly improved.

It is made of several elements such as chromium and molybdenum, which has high hardness and good toughness. Under the same work condition, the service of this kind of ball is one time longer than the high manganese steel ball.

After the professional technology straightening and quenching processing process, a high carbon steel rod has high hardness, excellent performance, good wear resistance and outstanding quality.

The steel ball of ball mill and the mineral material are in point contact, so the finished product has a high degree of fineness, but it is also prone to over-grinding. Therefore, it is suitable for the production with high material fineness and is not suitable for the gravity beneficiation of metal ores.

The steel rod and the material are in line or surface contact, and most of the coarse particles are first crushed and then ground. Therefore, the finished product is uniform in quality, excellent in particle size, and high in qualification rate.

The cylinder shape of the rod mill and the ball mill is different: the cylinder of the rod mill is a long type, and the floor area is large. The ratio of the length to the diameter of the cylinder is generally 1.5 to 2.0;

The cylinder of the ball mill is a barrel or a cone. And the ratio of the length to the diameter of the cylinder is small, and in most cases the ratio is only slightly larger than 1, and the floor area is small, too.

The above is the main content of this article. The ball mill and the rod mill are the same type of machine on the appearance, but there are still great differences in the interior. It is very necessary to select a suitable machine for the production to optimize the product effect and maximize its efficiency.

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china grinding ball manufacturer, forged steel ball, grinding rods supplier - shandong shengye grinding ball co., ltd

china grinding ball manufacturer, forged steel ball, grinding rods supplier - shandong shengye grinding ball co., ltd

Grinding Ball, Forged Steel Ball, Grinding Rods manufacturer / supplier in China, offering 10-150mm Bola De Acero De Alto Cromo/Forged Grinding Steel Balls, Dia. 30-200mm Forged Grinding Steel Bar/Rod for Rod Mill, Bolas De Acero 1 "-6" Chrome Forging Steel Ball for Ball Mill and so on.

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rod mill - an overview | sciencedirect topics

rod mill - an overview | sciencedirect topics

Rod mills have an industrial yield that is less than that of a ball mill, which explains the fact that balls have a much larger grinding surface than rods. The power needed to operate a rod mill could exceed 30% of the power used in a ball mill.

Rod mills have the highest rolling speeds, with interpass times in the finishing stand of 15150 ms. This is too short for either static recrystallization or strain-induced precipitation, and dynamic recrystallization is the main grain refining mechanism. Microalloying could limit grain growth during rolling by particle pinning and solute drag. However, austenite grain sizes of 10m can be achieved in CMn steels with optimally designed rod rolling schedules, so the main purpose of microalloying is precipitation strengthening. As-rolled rod is typically controlled-cooled at 15C s1 in loose coils (Stelmor process) to achieve a desired final microstructure and precipitate distribution. The principle application for HSLA rod steels is as cold-formed fasteners. An example of such a steel is given in Table 2.

Rod mill charges usually occupy about 45% of the internal volume of the mill. A closely packed charge of single sized rods will have a porosity of 9.3%. With a mixed charge of small and large diameter rods, the porosity of a static load could be reduced even further. However, close packing of the charge rarely occurs and an operating bed porosity of 40% is common. Overcharging results in poor grinding and losses due to abrasion of rods and liners. Undercharging also promotes more abrasion of the rods. The height (or depth) of charge is measured in the same manner as for ball mill. The size of feed particles to a rod mill is coarser than for a ball mill. The usual feed size ranges from 6 to 25mm.

For the efficient use of rods it is necessary that they operate parallel to the central axis and the body of the mill. This is not always possible as in practice, parallel alignment is usually hampered by the accumulation of ore at the feed end where the charge tends to swell. Abrasion of rods occurs more in this area resulting in rods becoming pointed at one end. With this continuous change in shape of the grinding charge, the grinding characteristics are impaired.

The bulk density of a new rod charge is about 6.25t/m3. With time due to wear the bulk density drops. The larger the mill diameter the greater is the lowering of the bulk density. For example, the bulk density of worn rods after a specific time of grinding would be 5.8t/m3 for a 0.91m diameter mill. Under the same conditions of operation, the bulk density would be 5.4t/m3 for a 4.6m diameter mill.

In the rod mill, high carbon steel rods about 50 mm diameter and extending the whole length of the mill are used in place of balls. This mill gives a very uniform fine product and power consumption is low, although it is not suitable for very tough materials and the feed should not exceed about 25 mm in size. It is particularly useful with sticky materials which would hold the balls together in aggregates, because the greater weight of the rods causes them to pull apart again. Worn rods must be removed from time to time and replaced by new ones, which are rather cheaper than balls.

As mentioned by earlier wire rod mills housed within smelter plant premises rejects large volume of waste emulsions which because of its toxic oil contents can not be discharged in open drains. Further since above toxic oil contain in the waste emulsion being only around 7% it is imperative that the residual water after breaking the emulsion needs to be recirculated to the plant itself. Present authors developed a process [123] for breaking the emulsion and release of the residual the water conforming to statutory norms for disposal of treated water in the open drain. In this process the waste emulsion was treated with calcium hydroxide in order to coagulate the toxic oil and separate it out from the residual water. Small contaminants in the residual water were finally removed by activated charcoal, pH adjusted to 7 and the water released. Typically for 7% oil content in waste emulsion, application rate of 3wt% calcium hydroxide and 2.5wt% charcoal brought down C.O.D. of treated water within permissible range. Table3.5 gives an example of such treatment process.

Powder milling process, using ball or rod mills, aim to produce a high-quality end-product that can be composites and nanocomposites, and nanocrystalline powder particles of intermetallic compounds, amorphous, hydrides, nitrides, silicates, etc. Powder milling process has been continuously improving by introducing numerous innovative types of ball mills in order to improve the quality and homogeneity of the end-products and to increase the productivity. This chapter discusses the factors affecting the mechanical alloying, mechanical disordering, and mechanical milling processes and their effects on the quality of the desired end-products. Moreover, we will present some typical examples that show the effect of these factors on the physical and chemical properties of the milled powders.

To equalize the charge segregation at the ends of the mill, the mill is rotated in the level position for eight revolutions then tilted up 5 for one revolution, tilted down 5 for one revolution then returned to the level position for eight revolutions and the cycle repeated throughout the test.

A study of the movement of materials in a rod mill indicates that at the feed end the larger particles are first caught between the rods and reduced in size gradually towards the discharge end. Lynch [1] contended that the next lower size would break after the sizes above it had completely broken. He described this as stage breakage, the stages being in steps of 2. The size difference between the particles at the two ends of the mill would depend on

The presence of this size difference indicates that a screening effect was generated within a rod mill and that the movement of material in the mill was a combination of breakage and screening effects. The breaking process was obviously repetitive and involved breakage function, classification function and selection functions. Therefore for rod mills, an extension of the general model for breakage within each stage applies, where the feed to stage (i + 1) is the product from stage i. That is, within a single stage i, the general model defined by Equation (11.18) applies

The number of stages, v, is the number of elements taken in the feed vector. A stage of breakage is defined as the interval taken to eliminate the largest sieve fraction from the mill feed or the feed to each stage of breakage. The very fine undersize is not included as a stage.

The breakage function described by Equation (11.2) could be used. For the classification matrix, which gives the proportion of each size that enters the next stage of breakage, the value of the element in the first stage C11 equals 1. That is, all of size fraction 1 is completely reduced to a lower size and all the particles of the classification underflow are the feed to the second stage of breakage and so on. Hence, the classification matrix is a descending series. If we take the 2 series, then the classification matrix C can be written as

The selection matrix S is machine dependent. It is affected by machine characteristics, such as length (including length of rods) and the speed of operation. Both B and C have to be constant to determine the selection function S within a stage.

Thus for each stage a similar matrix can be developed resulting in a step matrix which provides a solution of the rod mill model. Calculations are similar to that shown previously for grinding mill models.

The industrial comminution process under consideration has the following four units: Rod mill, Ball mill, hydro-cyclones, and water sumps. Fresh feed from the bin is fed to the rod mill along with water. The slurry generated from the rod mill is mixed with the slurry from the ball mill in a primary sump. The primary sump outlet stream is sent to the primary cyclone. The overflow from the primary cyclone goes to the secondary sump and the underflow is taken as a feed to the ball mill. The slurry generated in the secondary sump is taken to another hydro-cyclone which is called as secondary cyclone. The underflow of the secondary cyclone is recycled back to the ball mill for grinding and the final product is the overflow which goes to a flotation circuit as feed. Water is added to both sumps to facilitate the flow of the slurry smoothly within the circuit. Complete circuit configuration can be found in Figure 1.

Modeling of individual unit operations of the grinding circuit is performed separately using an amalgamated approach of population balance and empirical correlations. A simulation of an entire circuit is done by using a connectivity matrix which connects all the unit operations in terms of binary numbers. Here 0 denotes no connection and 1 denotes existence of a connection. Multiple simultaneous differential algebraic equations were formed using the entire set of equations which can be solved using well tested public domain software, called DASSL (Petzold, 1983). Details on these model equations can be found elsewhere (Mitra and Gopinath,2004) and not attached here for the sake of brevity.

The product size from HPGR can be much finer than the corresponding ball or rod mill products. As an example, the results by Mrsky, Klemetti and Knuutinen [12] are given in Figure6.8 where, for the same net input energy (4kWh/t), the product sizes obtained from HPGR, ball and rod mills are plotted.

Related Equipments