Tubular Ball Mills

1. Introduction

The usual objective of reducing the size of run-of mine ore pieces is to separate the mineral of interest contained in the ore body from associated gangue minerals. As crushing only does not generally liberate a mineral, further size reduction is usually required. This is achieved by grinding the crushed ore in tubular mills or devices such as pan mills or roller-grinder mills. In tubular mills, a grinding media such as steel balls, rods or hard pebbles imparts the forces required for size reduction. On rotating a mill charged with rocks and grinding media, the entire charge rises against the perimeter of the mill in the direction of motion. On reaching a certain height, part of the charge cascades and falls to the bottom of the mill; the other part tends to slip down but soon travels in the direction of motion of the mill. During this process, the media drops repeatedly onto the rock breaking down its size. Some size reduction also takes place due to abrasive forces. As a result of the combined action of repeated impact and abrasion over time, size reduction takes place and given sufficient time the mineral of interest is liberated.

Some tubular mills are specially shaped mills, such as the Hardinge Mill, where only the central portion is cylindrical and the ends are shaped like the frustum of a cone. Straight cylindrical mills, however, are the more common. The grinding medium generally used is in the form of balls, rods or cylindrical media called cylpebs. Both steel and ceramic balls are in use depending on the hardness of the rock. For soft ores, pebbles are added or simply autogenously ground with no medium. Both wet and dry grinding is common. Figure 1 illustrates the grinding action inside a tubular mill.
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Grate discharge ball mill

Assembly drawing of Grate discharge ball mill

The structure of various specifications of ball mill is basically the same, the following is an example of 2700x3600mm grate ball mill produced by Henan Deya Machinery Co., Ltd.

The following figure shows the assembly drawing of 2700x3600mm grate ball mill produced by Henan Deya Machinery Co., Ltd.


2700x3600mm grate ball mill
1.Drum 2. Flange 4. Screw 5. Manhole 7. Quill shaft end cover 8. Combination drum-scoop feeder 9. End cover liner 10. Bearing inner sleeve 11 Dust Cover 12 Quill shaft end cover 13 Grate liners 16 Central liners 17 Bearing inner sleeve 18 Ring gear 19 Pinion 20 Transmission shaft 21 Coupling Joint
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Overflow ball mill

This standard specifies the terms and definitions, technical requirements, test methods, evaluation of overflow ball mill energy consumption and the labeling of energy consumption level for overflow type ball mill for mining. This standard applies to overflow ball mills.

1.Terms and Definitions

What GB/T7679.5 established as well as the following terms and definitions apply to this standard.

1.1 Working conditions
The material to be ground with feed size not more than 12.5mm, sieve rate not less than 80%, and discharge size not more than 0.075mm. The work index of the material is 13kW-h/t, and the universal hardness is f=8~12; the working condition of the overflow ball mill is continuously feeding.

1.2 Energy consumption index
Under the specified standard working conditions, the ratio of the measured power to the processing capacity of the overflow ball mill is expressed in kW-h/t.

1.3 Value of energy saving evaluation
Achieve the energy consumption index value required for energy-saving products.
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The standard of Ball mill and Rod mill

1. Scope

This standard specifies the following scope of ball mills and rod mills, their type and basic parameters, technical requirements, test methods, inspection rules, marking and instructions for use, packaging, transportation and storage.

This standard applies to ball mills and rod mills(Hereinafter referred to as mills) for grinding ores, rocks and other suitable grinding materials of various hardness in wet and dry processes.

2. Type of mills and basic parameters

2.1 Type of mills

2.1.1 Mills are divided into ball mills and rod mills according to different grinding media; ball mills are divided into grate type and overflow type according to discharge form, and grate type ball mills are divided into dry type and wet type. The structure type is shown in Figure 1, Figure 2, Figure 3, Figure 4 and Figure 5 respectively, and this figure does not determine the specific structure. Among them, Figure 1 discharge end cover structure is recommended for grate ball mill with diameter no more than φ3200mm, and Figure 2 discharge end cover structure is recommended for grate ball mill with diameter no less than φ3600mm.
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