Ore material size control

In beneficiation plant, With size control we understand the process of separating solids into two or more products on basis of their size. This can be done dry or wet. neither crushers nor grinding mills are too precise in their size reduction job and a lot of size fractions are misplaced. By using optimum size control the result can be improved both regarding capacity, size and particle shape.
Size Control by Duties
To prevent undersize in the feed from blocking the next size reduction stage(scalping)
To prevent oversize from moving into the next size reduction or operation stage(circuit sizing)
To prepare a sized product (product sizing)
Size Control by Methods
In mineral processing practices we have two methods dominating size control processes:-Screening using a geometrical pattern for size control.
-Classification using particle motion for size control.


Screens
Performance of screens will fall back on three main parameters:
Motion – Inclination – Screening Media
Screen Motions
Screening by Stratification
By building up a material bed on a screen deck the material will stratify when the motion of the screen will reduce the internal friction in the material. This means that the finer particles can pass between the larger ones giving a sharp separation.



Screening by free fall
If we use the double inclination used for stratification (from 10-15 up to 20-30 degrees) we are in free fall, meaning that no particle layer can build up on the screen deck. The particles will now be sized directly via the screening media, giving a higher capacity, (or a more compact installation), but also less sharpness in separation. Optimal use when a large amount of fines shall be removed fastly.
Screen Types
There are many types of screens, but they can be reduced to the four types shown below. Of these types approx.80 % used worldwide are of type single inclination, stratification screens. The other are of type double, triple or multiple inclination, where screening by stratification and free fall are combined for different applications.
Single inclination
• Stratification screen

• Circular (15 deg.)
• Linear 0-5 (deg.)
• Still the leader in selective screening
Double inclination
• Free fall
• Compact - high capacity paid for by lower selectivity
• Typical in circuit screening
Triple inclination
• Combine capacity and selectivity
• Typical control screen for advanced product fractions
Multiple inclination (banana screen)
• Effective ”Thin-layer” screen
• Popular in coal and metallic mining
Selection of Screening Media
Selection of the correct size and type of screen is important. Equally important is the selection of the screening media. This refers not only to a correct aperture related to the ”cut size ”, but also to the wear in operation of these screens. Below a short selection guide to screening media can be found.
Rubber or Polyurethane?

What type of panel

What thickness?
General rule for min. Thickness
What hole size? (Inclined deck)
General guideline for wire mesh:
Required product size plus 5 – 10%
General guideline for PU panels:
Required product size plus 15 – 20%

General guideline for rubber panels:
Required product size plus 25 – 30%

What type of hole?
Particle Size – Mesh or Micron?
Sinonine technology team

评论

发表评论

此博客中的热门博文

Mineral froth flotation

图片
Sinonine deeply know that in a beaker of water, if air is introduced from the bottom, air bubbles are produced  and rise to the surface of the water as the density of an air bubble is much less than that of water (Figure.1 A). Similarly air bubbles also rise if air is introduced in a pulp containing mineral particles. If a mineral particle of high density adheres to the air bubble, the air bubble along with the mineral particle rises to the surface because the apparent density of the air bubble and the adhered mineral particle is less than that of water. If many mineral particles are adhered to the air bubble, still the air bubble rises to the surface as the apparent density of the air bubble and adhered mineral particles is less than that of water due to the relatively large volume of the air bubble Figure 1 B). This concept is the basis for froth flotation operation. To use this concept or phenomenon, the following are required: 1 Method to make the mineral particles adhere to
阅读全文

The motion of the charge in a ball mill

图片
The distinctive feature of ball mills is the use of loose crushing bodies, which are large, hard, and heavy in relation to the ore particles, but small in relation to the volume of the mill, and which occupy slightly less than half the volume of the mill. Due to the rotation and friction of the mill shell,the grinding medium is lifted along the rising side of the mill until a position of dynamic equilibrium is reached, when the bodies cascade and cataract down the free surface of the other bodies, about a dead zone where little movement occurs, down to the toe of the mill charge (Figure 1). Figure1. Motion of charge in a ball mill The speed at which a mill is run is important, since it governs the nature of the product and the amount of wear on the shell liners. For instance, a practical knowledge of the trajectories followed by the steel balls in a mill determines the speed at which it must be run in order that the descending balls shall fall on to the toe of the charge, an
阅读全文

The Slurry Line

图片
Slurry pumps are important being the energy source in all hydraulic systems for slurry handling. However, the slurry pumps are mainly just energy converters in the systems (converting electric energy to hydraulic flows). Equally important is to design “the slurry line” with the correct sizing of hoses (or pipes) including • Hose lay-out geometry (vertical and horizontal) needed for the transportation job • Hose material giving resistance to the wear and to the chemical environment • Hose diameter enabling maximum efficiency of the slurry system SLURRY OPERATIONS Grinding Classification Separation Sedimentation Mechanical dewatering Hoses are for slurry handling what conveyor belts are for dry materials handling. Simple products – which just have to maintain their functions. Otherwise the process flow will be interrupted and the up-time is gone. There is just one rule for lay-outs of slurry hoses and pipes, but a golden one. “ Never use sharp bends when co
阅读全文