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Grinding Circuits

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Wet grinding of feed P80 25 - 30 mmto product size P80 0.3 mm to 2 mm (8 Mesh - 48 Mesh)
in open circuit. One of the most common flowsheets for mineral processingplants to wet grind - 25 mm (1") feeds (or finer) to desired product size. Rod mill discharge about. 1 mm (16 Mesh). Single stage ball grinding and single classification circuit The most simple and common (although not the most efficient) circuit to wet grind from max. feed sizes of P80 15 mm and finer to required product sizes. Tend to produce more slimes than multistage grinds and classifying. Autogenous-Single stage For the rare cases where primary AG milling will inherently produce the required product size. (Wet or dry) Autogenous + Crusher For the also not too common cases where critical size pebbles are created and thus inefficient grinding results. With pebble ports in the mill grate and separate crushing of the critical sizes this can be remedied. However, resulting product size must match product requirements. (Wet or …

Selection of Crushers

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In mineralprocessing plant, Knowing the number of crushing stages we can now start to select the correct crusher for each reduction stage. Depending on operating conditions, feed size, capacity, hardness etc, there are always some options. For primary crushers, see below.
Stationary crushers Mobile Crushers Primary Crusher For soft feed (below Mohs5) a horizontal Impactor (HSI) is normally the first option if capacity is not too high. For harder feed there is a choice between a gyratory or a jaw crusher, see below. Rule 1: Always use a jaw crusher if you can, being the most cost effective alternative. Rule 2: For low capacity use jaw crusher and hydraulic hammer for oversize Rule 3: For high capacities use jaw crusher with big intake opening Rule 4: For very high capacities use gyratory crusher Secondary Crusher In a rock crushing circuit, the second stage normally starts to be of importance for control of size and shape. Because of this the jaw crusher, in most cases, is disqualified as seconda…

Crushing of Ore and Minerals

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In these operations the value is achieved at the fine end, say below 100 micron (150 mesh). Normally the size reduction by crushing is of limited importance besides the top size of the product going to grinding. This means that the number of crushing stages can be reduced depending on the feed size accepted by primary grinding stage. 3 stage ore crushing prior to rod mill
Below is an example of gold ore processing crushing section, it is 3 stage crushing prior and the grinding mill is rod mill. Primary crushing is jaw crusher,secondary crushing is cone crusher,tertiary crushing is fine cone crusher. 1-2 stage ore crushing prior to AG-SAG mill Below is two examples of one stage and two stages of crushing and grinding is AG-SAG ball mill. Sinonine technology team

Size reduction –crushing and grinding minerals

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By tonnage this is by far the largest process operation in mineral processing. The goal is to produce rock or (more seldom) mineral fractions to be used as rock fill or ballast material for concrete and asphalt production. Quality parameters are normally strength, size and shape. The size fractions, see below, are priced according to defined size intervals. Main crushing machine including GYRATORY CRUSHER, CONE CRUSHER, JAW CRUSHER, IMPACT crusher etc. Size reduction of ores is normally done in order to liberate the value minerals from the host rock. This means that we must reach the liberation size, normally in the interval 100 – 10 micron, see value curve 1. If the raw material is a single mineral (Calcite, Feldspar a.o.) the value normally lays in the production of very fine powder (filler), see value curve 2. In order to maximise the value in size reduction of rock and minerals, see below, we need both crushing and grinding in various combinations.The grinding machine inckuding bal…

Bulk Weighing and Sampling Techniques in mineral processing

Bulk Weighing Techniques In mineralprocessing plant, Several types of systems are currently in use to determine the weight of bulk commodities shipped or received: _ Truck scales _ Railroad track scales _ Rotary dumper scales _ Hopper scales _ Belt conveyor scales _ Vessel drafting Unlike static weighing devices, such as track scales and hopper scales, a belt conveyor scale is a dynamic weighing device requiring time integration. The material weight in kilograms per meter (or pounds per foot) is integrated with belt travel over a period of time. A belt scale is capable of accurate weighing (down to as low as 0.25% of the scale rating) and is the least expensive of the scale devices listed above. For a more detailed description of bulk solids weighing systems, the published literature should be consulted. An important point to keep in mind is that a weighing system is not simply a scale. A scale is a manufactured piece of equipment, normally statically tested at the plant. Under actual conditio…

Brief introduction of mineral processing

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Mineral processingmay be comprehensively described as the physical or chemical processing methods or their combinations, which may or may not lead to changes in the physical and/or chemical properties of a mined mineral resource, and which ultimately result in the production of a processed mineral product that can either be ready for use or be better suited for further processing. Mineral processing operations can be grouped into front-end and back-end operations as shown in Figure 1. The front-end operations essentially comprise processes leading to material severance and the back-end operations, to separation of the severed material into two parts – one that is valuable (called the concentrate), and the other that is not (called the tailings). Since most of the mineral processing operations are conducted wet, dewatering forms very much an integral part of the whole scheme. The content of the present chapter consists primarily of the two cited ends which best describe or convey quite…

Mineral Processing Flowsheets

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In mineral processing plant,A general flowsheet involving almost all the unit operations pertinent to mineral processing is shown in Figure 1. The others refer specifically to beach sands,leadzinc mining plant, molybdenum, and the rare earths .
Processing of silica sands provides a good example of the response of minerals to magnetic and electrostatic fields. A generalized flowsheet for separating the mineral constituents of beach sands is shown in Figure 2 . It will be seen that the separation is essentially based on the differences in the magnetic properties and in the electrical conductivity of the various minerals present in the beach sands. The behaviour of some typical beach sand minerals, as for instance magnetite, ilmenite, garnet, monazite, rutile, zircon, and quartz, in respect of their responses towards magnetic and electrostatic separators. A reference is also drawn to Figure 3 which exclusively shows flotation playing the centrally important role in lead–zinc concentration…

Flotation system

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In beneficiation plant, Flotation, like all other separation processes, is imperfect in that simply by applying this process only once, very little separation may be achieved. For example, the underflow from a flotation machine unit may have many hydrophobic particles that have failed to encounter an air bubble, or the overflow may have hydrophilic particles that have simply been caught in the wake of an air bubble or in a collection of hydrophobic particles secured to a bubble. It is, therefore, common practice to operate many cells in complicated series – parallel arrangements, perhaps with adjustment of chemistry at some point. This is necessary because only a limited separation is usually attainable in a single device, and as such there is a need for roughing, cleaning, and scavenging components in a circuit. Generally speaking, roughing is the primary operation, which utilizes a moderate separating force to remove the fully liberated valuables. Scavenging utilizes strong chemistry…

DESIGN OF STORAGE SILOS AND HOPPERS

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In beneficiation plant, In the general field of bulk solids handling, ensuring that both the storage of materials and the movement from storage will be carried out in an effective and efficient manner is essential. However, the flow out of bins and hoppers is well known to be often unreliable; as a result, considerable costs are incurred because of consequential losses in production. Problems that commonly occur in storage bin operation include particle segregation, erratic feeding, flooding, arching, piping, and adhesion to the bin walls—all of which reduce the bin capacity below the values specified by the manufacturer. For example, a poorly flowing material may cause an arch or bridge over the hopper outlet or a stable rathole within the bin (see Figure 1). On the other hand, a very flowable material (dry, fine powder) may become aerated and subsequently fluidize, causing potential flooding problems.
Where flow blockages occur in practice, a common response is to resort to flow-prom…

FILTRATION MACHINE- Batch and Semicontinuous Filters

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In beneficiation plant, Continuous filters tend to be more widely used in the mineral and coal processing field, particularly where large tonnages are involved. This preference reflects the lower capacities of batch or semicontinuous units and the increased labor requirements, both of which result in higher operating costs. However, at low-tonnage plants and under special conditions, these filters can have distinct advantages. Also, where pressure drops must be used that are higher than those obtained by continuous vacuum filters (because of the low cake permeability), the pressure filter may be applicable. For instance, tailings may be filtered to recover water or to dewater them to a high enough solids concentration to allow land disposal. The mineral and coal processing industry use batch and semicontinuous filters of four types: plate and frame filters, recessed plate filters, vertical disk pressure filters with or without sluice discharge, and automatic discharge plate and frame-…

FILTRATION MACHINE- Continuous Filters

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In beneficiation plant, filtration machine can be divided into three modes: continuous, batch and semicontinuous, and clarifying. Each of these modes can be further subdivided. The discussion that follows is limited to those units with significant application in mineral and coal processing. Continuous Filters Continuous filters may be divided into those forming their filter cake against gravity and those forming their filter cake with gravity.
Filters Forming Cake Against Gravity. Disk and drum filters all form cake against gravity. The latter can be further divided into scraper discharge, roller discharge, and continuous-belt drum filters. A disk-type filter contains a series of individual disks mounted on a center barrel. The barrel is held in trunion bearings mounted on either end of the filter tank. The disks are partially submerged in the feed slurry to a standard apparent submergence of about 35%. A higher submergence would require stuffing boxes around the center barrel, a procedur…