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Mineral processing unit operation and examples

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UNIT OPERATIONS In mineralprocessing plant, Numerous steps, called unit operations, are involved in achieving the goal of extracting minerals and metals from ores in their purest possible form. These steps include Size reduction. The process of crushing and grinding ores is known as comminution. The purpose of the comminution process is threefold: (1) to liberate valuable minerals from the ore matrix, (2) to increase surface area for high reactivity, and (3) to facilitate the transport of ore particles between unit operations. Size separation.Crushed and ground products generally require classification by particle size. Sizing can be accomplished by using classifiers, screens, or water elutriators. Screens are used for coarse particulate sizing; cyclones are used with fine particulates. Concentration. Physicochemical properties of minerals and other solids are used in concentration operations. Froth flotation, gravity concentration, and magnetic and electrostatic concentration are used exten…

METALLURGICAL EFFICIENCY

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One of the most important and basic concepts in beneficiation plant is metallurgical efficiency. Two terms are commonly used to describe the efficiency of metallurgical processes: recovery and grade. These phenomena are illustrated in the generalized process presented in Figure 1. In above example, 100 tph of ore are being fed into a concentration operation that produces 4.5 tph of concentrate and 95.5 tph of tailings. In upgrading this process, then, 1.0 tph of the desired material, A, is introduced into the unit operation and 0.9 tph (4.5 × 0.2) of this material reports to the concentrate, resulting in 90% recovery (0.9/1.0 × 100). The grade of the mineral, A, has been improved from 1% to 20%. The term percent recovery refers to the percentage of the valuable material reporting to the concentrate with reference to the amount of this material in the feed. Note that obtaining the highest possible recovery is not necessarily the best approach in a concentration process. High recovery wi…

GOALS AND BASICS OF MINERAL PROCESSING

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In the traditional sense, mineral processing is regarded as the processing of ores or other materials to yield concentrated products. Most of the processes involve physical concentration procedures during which the chemical nature of the mineral(s) in question does not change. In hydrometallurgical processing, however, chemical reactions invariably occur; these systems are operated at ambient or elevated temperatures depending on the kinetics of the processes. The lead zinc ore processing in the production of metals is to yield metals in their purest form. Mineral processing plays an integral part in achieving this objective. Figure 1 shows a generalized flow diagram for metals extraction from mining (step 1) through chemical processing. Steps 2 and 3 involve physical processing and steps 5 and 7 involve low-temperature chemical processing (hydrometallurgy).
All four steps are considered part of mineral processing. High-temperature smelting and refining (pyrometallurgy), steps 4 and 6, …

The Slurry Line

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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 connecting them hydraulically! ” • Every slur…

Mobile beneficiation plant system

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In mineral processing plant,modern quarrying, mining, tunnelling and recycling operations the use of mobile process systems is increasing dramatically. Particularly at rock front operations the technique of “moving the process equipment closer to the front end” using mobile crushing and screening units in many cases gives remarkable cost savings. These mobile units represent one or more complete machine functions including materials handling, power supply etc. Advanced process control secures the “intelligence” of the system.
Mobile Crushing and Conveying System Key arguments for mobile equipment vs stationary equipment and damp truck haulage are: • Less hauling – less costs • Less front road maintenance • Less exhaust gas and dust emissions • Improved working safety • Improved flexibility Primary Jaw Crusher + Grizzly Primary Impact Crusher + Grizzly A pre-assembled Ore Concentrating Plant Typical units at approx. 10 t/h capacity 1.Crushing unit Jaw- and cone crusher in closed circuit with a double …

Feeding and Conveying

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Feeding In a mineralprocessing plant, Feeders are necessary whenever we want to deliver a uniform flow of dry or moist fractions of rock or minerals.
Generally they are categorised by the size of material to be fed, see below. Primary Feeders Capacity:700 - 5000 t/h apron feeder Capacity 300 - 1200 t/h, vibrating feeder
“In circuit” feeders Wobbler feeders Feeding and scalping - when things get sticky! Conveying belt Conveyors are selected from 4 key parameters: • Tonnage • Size of material • Inclination • Distance We also must consider wear in operation and the environment (dust, heat, oil or chemicals etc) Conveyor belts Although the conveyor structure is important, most of the conveying work falls back on the conveyor belt, exposed to the material. Flat belts are dominating, conveying up to a lifting or lowering angle of approx. 18°. Depending on duty the belts are reinforced with different materials (Polyester/ Polyamide, Aramid fibres or mesh net Steel Cords) in 2-5 plies, protected by a top cover…

Storage Buffering in mineral processing plant

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In mineral processing plant,Buffer storage is some time called “the key to processing”, meaning that without a proper storage throughout a continuous rock or mineral process, production uptime will be gone. Storage in operation The main purpose of storage is to smooth out: • Different production rates (cont.cyclic) • Shift variations • Interruptions for repair • Size variations • Flow variations • Variations in mineral value (metal content etc.) Storage of rock (1)
A matter of material flow (retention time),see below the crushing system of lead zinc ore processing: Storage of ore and minerals (2) A matter of material flow (retention time) and blending Sinoninetechnology team

Coolers and heat recovery

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In mineral processing plant, the temperatures of discharged products from thermal processing are high. In order to lower that temperature, or to recover some heat, or both, coolers are used. Most of the coolers are inversely working dryers, however, with a higher capacity per installed unit. Coolers of rotating drum type Normally there are three basic designs: •Air Swept Coolers built similar as a counter flow direct heat rotary dryer, where hot gasses are replaced with ambient air •Water cooled shell coolers where the drum shell is cooled with water or is submerged in a pool of water. •Water tube coolers having the same design as a steam tube dryer, where the steam is replaced with cool water Coolers of fluid bed type The principles of fluid bed can be used also for cooling purposes. In this case the fluid bed is cooled by internal water pipes. Ash Cooling
Circulating Fluidized Bed Boiler Coolers and heat recovery Thermal processing is a question of limiting the energy input for each part of the …

Thermal processing

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In mineralprocessing plant, Dewatering by using Tube Presses represents the highest energy level of mechanical upgrading of minerals. If further upgrading is required we have to use thermal processing. Thermal processing is normally classified according to operating temperature. Thermal low ( 100-200° C) Used for drying - evaporating of liquids from solids - drying Type of equipment • Direct Heat Rotary Dryers • Indirect Heat Rotary Dryers • Steam Tube Dryers • Indirect Heat Screw Dryers (Holo-FliteR) • Fluid Bed Dryers Thermal medium (850 -950°C) Used for calcining, clay swelling, limestone burning and foundry sand burn out Type of equipment • Direct Heat Rotary kilns • Indirect Heat Rotary kilns • Vertical Kilns • Fluid bed Kilns Thermal high (1300-1400°C) Used for pelletizing of iron ore concentrates and petroleum coke calcining Type of equipment • Direct heat rotary kiln Thermal processing basics Thermal processing is expensive. This means that lowest input in calories/ton is the key issue. With raisi…

Mechanical Dewatering by Pressure

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In mineral processing plant,As particles get finer the resistance against removing water increases. Gravity dewatering can no longer be used. We have to use pressure. By creating a differential pressure Δp across a cake of solids, liquid can be removed by
Compression “Dewatering by compression means replacing the liquid in a cake with particles” Through blow Dewatering by through-blow means replacing the water in a cake with air” For vacuum filters air-through blow is used For vertical plate pressure filters either compression or a combination of compression and air through-blow is used For Tube Presses either compression or a combination of compression and airpurge is used. The Tube Press also enables cake washing. Drum Vacuum Filters Vacuum filtration is the simplest form of “through blow” dewatering. A pressure differential created by a vacuum applied to the inside of the filter drum causes air to flow through the filter cake thereby displacing the contained water. The solids are retained on…