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# selection function rod milling

## rod mill design calculations

EF2 Open Circuit Grinding when grinding in open circuit ball mills, the amount of extra power required, compared to closed circuit ball milling, is a function of the degree of control required on the product produced. The inefficiency factors for open circuit grinding are given in Table VIII.

EF4 Oversized Feed when being fed a coarser than optimum feed, this factor applies to rod milling and ball milling. However, the most frequent use is found in conjunction with single stage ball milling. This is the one efficiency factor that is related to Work Index as is seen in the following equation:

When available, use the Work Index from a grindability test at the desired grind for Wi in equation 9. For equation 11, use either the Work Index from an impact test or a rod mill grindability test, whichever is higher. For equation 12, use the Work Index from a rod mill grindability test, since this more represents the coarse fraction of the feed; if not available then use the ball mill grindability test results.

This factor always applies to low ratios of reduction but its application to high ratios of reduction is not always needed, but should be used for mill size selection whenever Wi from the rod mill and ball mill grindability tests exceed 7.0.

EF7 Low Ratio of Reduction Ball Hill the need to use this factor does not occur very often as it only applies to ball milling when the Ratio of Reduction is less than 6. This shows up particularly in regrinding concentrates and tailings. The equation for this is:

EF8 Rod Milling a study of rod mill operations shows that rod mill performance is affected by the attention given to preparation and feeding a uniform top size feed size to the mill and the care given to maintaining the rod charge. This efficiency factor has not been definitely determined. In selecting rod mills based upon power calculated from grindability tests, the following procedure has been recommended:

EF8 The rod mill feed will be prepared by closed circuit crushing and the rod mill will be in a rod mill-ball mill (or pebble mill) circuit with no intermediate concentration stage so no EF8 factor need be applied. If it were just a rod milling circuit or if there were an intermediate concentration stage between the rod and the mill a 1.2 factor would apply.

Referring to Table V two mills will be required. The preliminary rod mill selection would be a 3.66 meter (12 foot) inside shell 3.46 meter (11.35 foot) diameter inside new shell liners. Referring to Table IX the EF3 (Diameter Efficiency) factor is 0.931.

Referring to Table V the 3.66 m x 4.88 m rod mill with 4.72 m (15.5 ft.) long rods calculates to draw 972 HP when carrying a 40 percent rod charge with a worn-in bulk density of 5606 kg per cubic meter (350 pounds per cubic foot). 1031 HP is required. Therefore, increase mill length by 0.3 meters (1 foot).

Therefore, use two 3.66 meter (12 foot) diameter inside shell 3.46 meter (11.35 foot) diameter inside new shell liners by 5.18 meter (17.0 foot) long overflow rod mills with a 40 percent by mill volume rod charge with 5.02 meter (16.5 foot) long rods.

These mills are required to prepare ball mill feed. With pebble milling the pebble portion of the product does not go thru the rod mill thus the rod mill feed rate is reduced by 30 metric tonnes per hour (6% of 500 metric tonnes per hour).

Therefore, use two 3.66 meter (12 foot) diameter inside shell 3.46 meter (11.35 foot) inside new shell liner by 4.88 meter (16 foot) long overflow rod mills with a 40 percent by mill volume rod charge with 4.72 meter (15.5 foot) long rods.

## rod mill introduction,rod mill working principle

The rods grind the material by tumbling within the mill. To prevent the conditions leading to rod charge tangling, the length to diameter ratio is maintained at 1.4 to 1.6. Rod mills accept feed up to about 50 mm (2 in.) and produce a product in the size range of 3000 to 270 mm (4 to 35 mesh). Compared with other types of rod mill for sale and rent, Zenith's rod mill has more outstanding features

Zenith's rod mill is widely applied in metal and nonmetal mine, water conservancy, glass and construction materials industries, mainly suitable for grinding various ores and rocks and artificial sand-making. As for the mining materials, Zenith's rod mill are used to process the lime stone, hematite, magnetite, cement, coal , silicate, new building material, refractory material, fertilizer, ferrous metal, nonferrous metal and glass ceramics, etc.

The materials spirally and evenly enter the first warehouse of the ball mill along the input material hollow axis by input material device. In this warehouse, there is a ladder scale board or ripple scale board, and different specification steel balls are installed on the scale board. When the barrel body rotates and then produces centrifugal force, at this time, the steel ball is carried to some height and falls to grind and strike the materials. After being grinded coarsely in the first warehouse, the materials then enter into the second warehouse for regrinding with the steel ball and scale board. In the end, the power is discharged by output material board and the end products are competed.

## billet selection and heating of hot rolled wire rod mill

In this Hot Rolled Wire Rod Mill production line because of the close distance between the continuous casting machine and rolling line, the hot billet is used as raw material and hot charging process of continuous casting billet is adopted.

4. The production cycle is shortened by the hot charging process and omitting preheating section. According to the heating system and requirements of different steel grades, the billet is heated to 1050 C ~ 1250 C in the heating furnace. Because the hot charging process of continuous casting billet is adopted in this design, the preheating section in the typical three-stage heating system of preheating, heating and soaking are omitted, and only the heating and soaking section is taken. The billet is heated rapidly in the heating section. The surface temperature of the billet is slightly higher than the tapping temperature, and the homogenization of the billet temperature is completed in the soaking section.

High-pressure water descaling device is used in this design. The heated billet is pushed out by the tapping roller and the oxide scale on the surface is removed by high-pressure water to improve the surface quality of the rolled piece and facilitate the biting of the rolled piece.

The billet is transported from the roller to the roughing mill for rolling. When the rolling mill fails, the clamping shears set in front of the roughing mill will cut off the billet entering the roughing mill, and the slab after the clamping will return to the reheating furnace to keep warm for rolling. A flying shear and a clipping shear are installed behind the roughing mill. According to the technological requirements, the billet is rolled in roughing mill and intermediate rolling mill without torsion and tension.

The billet passes through side loopers and enters four cantilever pre-finishing mills arranged alternately in the horizontal and vertical direction for single-strand no-tension no-twist looper rolling. Finally, the billet enters the finishing mill through the pre-water cooling section, flying shear cutting head and tail, and side looper rolling. Ten 45 degree non-twist finishing mills are used in the finishing mill. High-speed single strand wire rod non-twist micro-tension continuous rolling of the rolled piece into high-precision wire rod is carried out in cantilever tungsten carbide small roll ring.

## estimating the breakage and selection functions for a continuous mill - sciencedirect

Methods for determining the breakage and selection functions for a continuous mill using plant data are discussed. The usual approach for finding the breakage and selection functions has been first to use batch tests to determine the breakage function. Then the selection function has been found by using data from the continuous mill. This may be avoided by using iteration techniques for solving the population balance model grinding equation. The principal methods of solution are discussed. A program using this approach has been developed, and the practicalities of using this approach are discussed.

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