Fluids And Solids Handling Technology Engineering Essay
Slurry is by and large defined as a thick suspension of solids in liquid. In a commercial slurry grapevine system we deal with assorted composings of slurries at changing distances. The grapevine building techniques for a coal slurry grapevine are about the same for a conventional grapevine.
In a slurry grapevine system H2O is used as the chief conveyance medium. The ore is normally assorted with H2O by 50 % such that the slurry can be worked by the pumps and can be transported between the assorted phases.
Slurries are divided into two groups harmonizing to their different features ; non-settling and settling slurries. In non-settling slurries, the all right atoms form a stable homogeneous mixtures exhibiting increased evident viscousness. This all right particles causes the slurry to act in a instead unusual manner than a normal liquid and are termed as non-Newtonian. On the other manus, settling slurries are formed by thick atoms signifiers an unstable mixture. The atoms have higher erosion belongingss and organize the bulk of slurry applications. They are termed as heterogenous slurries.[ 1 ]
Section ( a )
The maps of slurry conveyance can be composed into three major parts which are ;
Dewatering of slurry
Ore suppression and grinding
Figure 1: Ore Oppressing Process In order for the mineral to be used more rationally, it must be processed and crushed into different sizes such that they can be worked upon by the staying parts of the grapevine system. The oppressing procedure can cut down the size of the ore by 8 inches or less holding decrease ratios of 4 to 10. The size of the ores depends upon the system demands runing from 150mm to less than 1mm in size. These crushed atoms can be farther grinded into smaller atoms ( up to micro metres in size ) such that they can be mixed with the working fluid, holding decrease ratios of 50 to 100. Sometimes by merchandises are added into the system so that the wet content can be retained in the system.coal crusher work rule
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Figure 2: Cyclone centrifuge They are typically used to divide the crushed atoms to a needed size. They use the action of centrifugal force created by a digressive recess. The digressive recess produces a whirl in the system and the heavier atoms are collected on the underside and the igniter particles flight on the top called the whirl. The size of the atoms to be spectated depends on the diameter of the cyclone. Larger the diameter, larger the atom size. Thus cyclones are used in the grapevine system so that the needed partial size of the ore to be worked upon can be obtained. It is of import that the system is harder than the merchandise conveyed otherwise even the presence of little per centums of extremely scratchy stuffs will do terrible wear in the system.Cyclone Centrifuge
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Figure 3: A Centrifugal slurry pump Usually for long grapevines the Piston stop positive supplanting pump are used. These pumps are robust, dependable and have great public presentation while working with slurryaa‚¬a„?s in a grapevine. It is a positive supplanting pump that uses the combination of a gum elastic or thermoplastic stop and a non-return cheque valves to pump the fluid. One of the chief advantage is that the pumping Chamberss and the slurry being pumped are non in contact with any close adjustment rotary sliding seals. There is no demand to utilize variable velocity drivers or motors because the capacities are varied within the pumps range. They can develop force per unit areas up to 125 pounds per square inchs when high suction lifts are required. Normally a power supply of 15MW is required to present power to these pumps. The discharge of the pump can be shut off at any clip for long periods of clip with no harm. Fluid force per unit area alleviation valves or force per unit area control devices are non normally needed as pump discharge force per unit area can be no higher than the air force per unit area. They are self-priming with suction lifts up to 20 pess and more and can pump highly high barbarous fluids. These pumps can be submerged in fluids, even caustic fluids. They can work with immense scope of fluids, even those which are organic and caustic. hypertext transfer protocol: //img.directindustry.com/images_di/photo-g/hard-metal-centrifugal-slurry-pump-20610-2262577.jpg
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The stuff of the pipe should be well much harder than the conveyed stuff such that there is no wear and tear. Their hardness should be greater than the stuff slurry. The pipes are made up of stuffs from high strength low metal steels to bimetallic and metallurgical bonded stuffs. These stuffs are normally enhanced even more to run into the system demands of the grapevine. Debasing the steel can better the strength and wear opposition, for illustration adding high degrees of C and manganese additions the tensile strength of mild steel by 70 % and the wear opposition by 20 % . Other debasing stuffs include chrome, nickel, V etc. The pipe diameter used should be such that the minimal slurry speed needed to forestall solid subsiding is achieved.
Figure 4: Slurry Handling System including slurry keeping armored combat vehicle, slurry pump and slurry grapevine
A figure of valves and adjustments are used in the system which overcomes obstructions and interruptions in the system. Dump pools might besides be used to pin down the slurry when interruptions and obstructions are needed to be tackled. The pipe stuff microstructure can be modified by cold working ( produces stronger and rougher stuff ) and by heat treating ( better profile than cold working and is done by fire or by initiation hardening ) . However the addition in material hardness decreases its malleable belongings and increases its crispness, therefore by slaking the interior of the surface of the pipe by intensive slaking engineering the needed hardness can be obtained. The outer surface will be still malleable which an advantage because it allows the easiness of transit.
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The interior bed of the pipe can be improved by run alonging it with a bed of wear tiles which are made up of stuffs that are harder than the pipe stuff. They can be cast as rings and layered inside the pipe. Depending on the atom size and form, every bit good as the belongings to absorb impact energy, gum elastic and high ductile polymers can be used to line the inside bed of the pipe. Sometimes double walled pipes are besides used in a grapevine system. It consists of a pipe holding two distinguishable stuffs, a high tensile strength outer pipe covering a hard-boiled inner pipe. This produces system in which the outer aa‚¬E?shellaa‚¬a„? absorbs the impacts of the interior pipe. However the hardened bed is non bonded to the outside pipe, and can do a plugging obstructor. This is tackled by utilizing bimetallistic pipes which rely on a metallurgical bond between two distinguishable chemical sciences. The interior pipe stuff can be selected depending on the slurry being conveyed. The outer pipe can be selected by sing force per unit area capacity, lastingness and weld ability.
Dewatering of Slurry
At the discharge of a slurry grapevine it is indispensable to take the H2O so that the transported stuff can be worked with. It can be done automatically by utilizing filter imperativenesss, screens and extractors. Screening is normally used as the efficiency of dewatering depends on the atom size distribution. In the instance of coal, two phase cyclones are used for dewatering. The underflow from the cyclones is collected in a extractor to cut down the residuary moister content by 17 to 20 % . Hydro cyclones are besides used in some instances. Thermal drying is normally the last measure of the dewatering procedure.
Section ( B )
Section ( degree Celsius )