How does a Double Roll Crusher works - Mineral Processing For more mineral processing videos visit my YouTube Channel: http://www.youtube.com/hsrivastav2011/videos Description: Roll crushers, or crushing rolls, are still used in some mills, although they have been replaced in most installations by cone crushers. They still have a useful application in handling friable, sticky, frozen, and less abrasive feeds, such as limestone, coal, chalk, gypsum, phosphate, and soft iron ores. Jaw and gyratory crushers have a tendency to choke near the discharge when crushing friable rock with a large proportion of maximum size pieces in the feed. The mode of operation of roll crushers is extremely simple, the standard spring rolls consisting of two horizontal cylinders which revolve towards each other. The set is determined by shims which cause the spring-loaded roll to be held back from the solidly mounted roll. Crushing rolls Unlike jaw and gyratory crushers, where reduction is progressive by repeated pressure as the material passes down to the discharge point, the crushing process in rolls is one of single pressure. Roll crushers are also manufactured with only one rotating cylinder, which revolves towards a fixed plate. Other roll crushers use three, four, or six cylinders. In some crushers the diameters and speeds of the rolls may differ. The rolls may be gear driven, but this limits the distance adjustment between the rolls; and modern rolls are driven by V-belts from separate motors. Multi-roll machines may use rolls in pairs or in sets of three. Machines with more than two rolls are, however, rare in modern mills. The great disadvantage of roll crushers is that, in order for reasonable reduction ratios to be achieved, very large rolls are required in relation to the size of the feed particles. They therefore have the highest capital cost of all crushers. Peripheral speeds vary between about 1 ms -1 for small rolls, up to about 15 ms -1 for the largest sizes of 1800 mm diameter upwards. Smooth-surfaced rolls are usually used for fine crushing, whereas coarse crushing is often performed in rolls having corrugated surfaces, or with stub teeth arranged to present a chequered surface pattern. "Sledging" or "slugger" rolls have a series of intermeshing teeth, or slugs, protruding from the roll surfaces. These dig into the rock so that the action is a combination of compression and ripping, and large pieces in relation to the roll diameter can be handled. Their main application is in the coarse crushing of soft or sticky iron ores, friable limestone, coal, etc., rolls of 1 rn diameter being used to crush material of top size 400 mm. Wear on the roll surfaces is very high and they often have a manganese steel tyre, which can be replaced when wom. The feed must be spread uniformly over the whole width of the rolls in order to give even wear. One simple method is to use a flat feed belt of the same width as the rolls. Since there is no provision for the swelling of broken ore in the crushing chamber, roll crushers must be "starvation fed" if they are to be prevented from choking. Although the floating roll should only yield to an uncrushable body, choked crushing causes so much pressure that the springs are continually "on the work" during crushing, and some oversize escapes. Rolls should therefore be used in closed circuit with screens. Choked crushing also causes interparticle comminution, which leads to the production of material finer than the set of the crusher. For full working theory of roll crusher read the book: Mineral Processing Technology An Introduction to the Practical Aspects of Ore Treatment and Mineral Recovery, by Barry A. Wills, Tim Napier-Munn
What are thickeners & how do they work - Mineral Processing For more mineral processing videos visit my YouTube Channel: http://www.youtube.com/hsrivastav2011/videos Description: The thickener is used to increase the concentra- tion of the suspension by sedimentation, accompa- nied by the formation of a clear liquid. In most cases the concentration of the suspension is high and hindered settling takes place. Thickeners may be batch or continuous units, and consist of rela- tively shallow tanks from which the clear liquid is taken off at the top, and the thickened suspen- sion at the bottom. The feed slurry enters the feed well tangentially through the feed pipe. The feed slurry is pumped or fed by gravity to the thickener and shall have the energy to aid mixing of flocculant solution with it. The feed well is sized adequately to take care of the venting of the entrapped air in the feed slurry. The de-aerated and flocculated feed is then discharged through the annular gap formed between the feed well and the deflector plate at a predetermined velocity into the main body of the thickener. This ensures the distribution of flocculated feed radially in one plane across the full thickener area, aiding proper separation of solid liquor. As the solids settle down, the scrappers of rotating rakes scrap the solids towards the underflow cone for withdrawal. Liquor component raises to the upper part of the thickener to flow into the overflow launder.
How does a Gyratory Crusher Works - Mineral Processing In this video we will see what are the basic features of a Gyratory Crushers. Gyratory Crusher are used in Mineral Processing Industry for size reduction of Run off Mine (ROM) materials to size which eases their transportation. For more mineral processing videos visit my YouTube Channel: http://www.youtube.com/hsrivastav2011/videos
How does a Jaw Crusher Work - Mineral Processing LIKE, SHARE & Subscribe.. The distinctive feature of this class of crusher is the two plates which open and shut like animal jaws (Grieco and Grieco, 1985). The jaws are set at an acute angle to each other, and one jaw is pivoted so that it swings relative to the other fixed jaw. Material fed into the jaws is alternately nipped and released to fall further into the crushing chamber. Eventually it falls from the discharge aperture. Jaw crushers are classified by the method of pivoting the swing jaw (Figure 6.3). In the Blake crusher the jaw is pivoted at the top and thus has a fixed receiving area and a variable discharge opening. In the Dodge crusher the jaw is pivoted at the bottom, giving it a variable feed area but fixed delivery area. The Dodge crusher is restricted to laboratory use, where close sizing is required, and is never used for heavy-duty crushing as it chokes very easily. The Universal crusher is pivoted in an intermediate position, and thus has a variable delivery and receiving area. for more details regarding jaw crusher read Mineral Processing Technology An Introduction to the Practical Aspects of Ore Treatment and Mineral Recovery, by Barry A. Wills, Tim Napier-Munn
How does a Hammer Mill Works - Mineral Processing LIKE, SHARE & Subscribe. Description: Hammer mill- The hammers are made from manganese steel or, more recently, nodular cast iron, containing chromium carbide, which is extremely abrasion resistant. The breaker plates are made of the same material. The hammers are pivoted so that they can move out of the path of oversize material, or tramp metal, entering the crushing chamber. Pivoted hammers exert less force than they would if rigidly attached, so they tend to be used on smaller impact crushers or for crushing soft material. The exit from the mill is perforated, so that material which is not broken to the required size is retained and swept up again by the rotor for further impacting. This type of machine is designed to give the particles velocities of the order of that of the hammers. Fracture is either due to the severity of impact with the hammers or to the subsequent impact with the casing or grid. Since the particles are given very high velocities, much of the size reduction is by attrition, i.e. breaking of particle on particle, and this leads to little control on product size and a much higher proportion of fines than with compressive crushers. The hammers can weigh over 100 kg and can work on feed up to 20 cm. The speed of the rotor varies between 500 and 3000rev min -~. Due to the high rate of wear on these machines (wear can be taken up by moving the hammers on the pins) they are limited in use to relatively non-abrasive materials. They have extensive use in limestone quarrying and in the crushing of coal. A great advantage in quarrying is in the fact that they produce a very good cubic product. Hammer mills have been used by Australian coking coal producers to prepare coke oven feeds (0.125-6 mm). To assist in the beneficiation of coke oven feeds, recent work has led to the development of a model of the swing hammer mill (Shi et al., 2003). The energy-based model comprises a mechanistic model for the mill power draw and a perfect mixing mill model with a dual-classification function to describe the operation of the hammers and underscreen. The model is able to accurately predict the product size distribution and power draw for given hammer mill configurations (breaker gap, under-screen orientation, screen aperture) and operating conditions (feed rate, feed size distribution, and coal breakage characteristics).