Material handling is defined as the operation of lifting and shifting . The object of all material handling is the reduction  of  handling   cost, time, storage space, and effort. Mechanised  handling  permits synchronisation of operations,  avoidance of bottlenecks keeping the job on the move and  reduction  of  manual  labour which may be devoted to more useful purpose requiring skill and inte-lligence.Mounting labour costs throughout the world have

also directed attention  to the  expanding importance of mechanised handling in every field of industry

Lahiri, A K

Majumdar, S K

English

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Mass Handling of MaterialsS. K. MajumdarA. LahiriATERI A L handling is defined as the operationM of lifting and shifting . The object of allmaterial handling is the reduction of handlingcost, time, storage space, and effort. Mechanisedhandling permits synchronisation of operations,avoidance of bottlenecks keeping the job on the moveand reduction of manual labour which may be devotedto more useful purpose requiring skill and intelligence.Mounting labour costs throughout the world havealso directed attention to the expanding importanceof mechanised handling in every field of industry.It is not possible to cover comprehensively theMAP OF INDIASHOWING FULL RESEARCH INSTITUTE,COAL SURVEY STATIONS ANDCOAL- FIELDS OF INDIAMr. S. K. Majumdar and Dr. A. Lahiri, Central Fuel ResearchInstitute , lealgora.vast subject of material luutdling in a short article.The present paper deals mainly ok ith transportation,storage and handling mtethods generally employedin coal based industries in Lidia with special referenceto the proposed Central Waslierics of India.Over 5(i " , of the reserve , of India n coal are concen-trated in Bengal and Bihar and about _'S " i, in M.P.Bengal rutd 13iliar together raise nwre t1icin SU"o ofthe country's total production of coal . Nearly allthe coking coal is also raised from these two regions.The outlying coalfields of Madhya Pradesh, Deccan,Orissa, etc . produce only non-coking coals and thosetoo mostly of inferior grades. The industries a re, ingeneral, located far away front the coalfields , speciallythose in the west and south with the result thatcoal has to be transported over long distances toreach the points of constnnption.The common long distance transport in Indiatoday is the railways . Somtc amount is carried byroad also, specially for indnstries located near aboutthe production centres . About 33 , 000 tons is con-veyed to miscellaneous industries iI coastal shipping.Some amount of coal will be despate. hed from theBengal coalfields by boats or barges when the navigablecarnal linking Calcutta with Durgaptir is ready.For far-away consumers , the price of coal is morerelated to transport costs than to its pit headprices. The use of' Iuglter grange coal brings thornrelatively higher returns as in such a case they arerequired to use less coal for obtaining the sameamount of useful heat. Moreover , the use of superiorgrades permits installation of less costly plants andequipment and also recfnires handling machines oflower capacities. On the above grounds it is advisableto distribute coal on a zonal basis so that unlessspecifically required for any coal-based industry,only the consumers at relatively greater distanceswill be allowed to use the relatively superior grades ofcoal. This will also result in reducing the alreadyheavy burden on the ra ilway system.The transport of coal by the railways has beensubsidised to some extent. Freight charge on coalper ton mile is about Bs . 2. 85 against Rs. 5.36for grains.The increasingly deteriorating quality of coalmined per year has called for their upgrading bywashing in large central washerics . There are about850 collieries in India. The production from mostof them does not exceed 600 tons per day each.The economics of coal washing do not, therefore,456 INDIAN CONSTRUCTION NEWSallow installation, of washery in individual collieriesbut require them to be grouped suitably for thepurpose.When the collieries are grouped for the purposeof installing an economically sound washery, it isdesirable to locate it at a place through whichthe raisings of a majority or of all the collieriespass oil their way to the market or industries.Coal may be brought to the washery by meansof mine cars, wagons, road transports, ropeways,belt conveyors, etc. depending upon their respectiveconvenience and other factors. The aim of alllayout should be to minimise the ton mileage or,in other words, the raw coal should be hauled theshortest possible distance.Tile laying out of new lines or roads on anextensive scale requires huge capital apart fromother difficulties. If the coal is moved by wagonson existing tracks, it is convenient to locate thewashery in the base loading stations (marshallii ►gyards) which distribute the empties to the collieriesand despatch the loaded wagons to their destinations.The collieries in India are generally situated withinten miles of the base loading stations. On thebasis of the existing rate structure, the consumerswill have to pay an additional terminal charge of1.75 per ton on account of transport of raw coalto the washery over and above the usual freight.A network of aerial ropeways connecting thecollieries with the washery can be an alternativeto rail transport, but this method of transport willbe equally or perhaps more costly on account ofthe high per cent of capital costs. It may beeconomical to connect a limited number of collieriesif their cumulative production is sufficient to permitinstallation of all economical washery. The centralwashery at Kargali, for instance, has been plannedto wash coals from two collieries, viz. Kargali andJoint Boka,ro. The washery has been installed onthe railway yard of the Kargali colliery. The coalfrom the Bokaro colliery situated at a distance ofabout two miles is brought to the washery by meansof a bi-cable ropeway of about 250 tons per hour capacity.The wagons generally used for the transportationof coal carry 22 tons each. The modern trend intransportation is to use bigger trucks and wagonswith higher payloads in order to minimise handlingcosts as well as to increase the road or track capacities.Each of the wagons which will be used to transportcoal to the steel plants will be designed to have acarrying capacity of 56 tons 10 cwt. The presenttrain load of about 1,500 tons will thus be increasedto 3,000 tons.A steel plant with a yearly production capacity ofone million tons requires about 5,000 tons of superiorgrade coking coal per day. On the basis of thequality of the coal available, this can be obtained bywashing about 5,000 tons of R.O.M. coal of the typeat present being raised. The existing wagons with apayload of 22 tons and the eight-wheeler bogie wagonswith it payload of 56 tons will be used to transport coalfrom collieries to the washery and from the washeryto the steel plants respectively. Correspondingly, awashery with an installed capacity of 8,000 tons perday will have to handle about 360 and 100 wagonsof the two types respectively.The receiving and despatching sections of thewashery will work in all the three shifts of a daywhile the other sections will work mainly in twoshifts or even one. The incoming loaded wagons willbe pulled from their standage in sequence by car haulson to wagon tipplers designed to unload 40 wagonsper hour. The wagons will then be pushed out fromthe tipplers by car retarders in order to enable themto roll down to their respective standage. Thenon-standard and covered wagons will be unloadedmanually on some adjoining inclined ramp. The unloa-ded coal will roll down the ramp on to a belt conveyorwhich will convey them to the hoppers installedunderneath the wagon tipplers. The coal receivedby the hopper will be conveyed continuously by meansof belt conveyors to the storage area or direct tothe washery after being crushed to some predeterminedsize.Most of the washeries in India will produce threeproducts, viz. clean coal, middlings and rejects. Themiddlings will be utilised either for power generationor for tice manufacture of household coke. For shorterdistance of travel, specially if the power plant orthe soft coke installations are located at a site adjacentto the washery ; belt conveyor is the most appropriatemeans of transportation, for longer distances ropewaywill be more convenient. For these reasons themiddlings from the Kargali washery are being trans-ported to the Bokaro Thermal Power Station, locatedat a distance of about five miles, by means of amonocable ropeway.It is desirable to instal the thermal power stationsalongside the central washories to minimise transport,storage, and blending costs. On these considerationsit has been decided to instal a thermal power stationof 125 nn1\' capacity alongside the Dugda centralwashery to consume the middlings to be producedin the washery. Similar integration has been achievedat Kargali and will be clone at Durgapur, where therewill be a washery at the steel plant itself. In all thesecases, the power stations are designed for high ashand powdered coal firing so that they can handlethe var•ing and inferior quality of by-product fuelsproduced at the washery.The possibility of hydraulic transportation of largequantities of coal to great distances is being consideredeverywhere these clays. Hydraulic transportation isbeing used to some extent for transportation. of coal fromthe pit bottom to the surface as well as to conveythe washery rejects from the washery to the dumpinggrounds. Recently, the Pittsburgh Consolidation CoalCo. of the United States have built a pipe line totransport coal from the preparation plant at Cadizto a thermal power station at East Lake, Ohio, adistance of 110 miles. The coal will be delivered atthe rate of 150 (short) tons per hour through a 10"pipe line in the form of a slurry consisting of a mixtureof coal and water in the proportion of 50 : 50.AUGUST1959 4S7General arrangement plan of central coal washery at Dugda.It is well known that the quality- of coal beingmilted in India is deteriorating progressively eachyear. Increased mochanisation of mining methodswill further increase the proportion of refuse in thecoal mined. If the rejections from a. washery amountsto 101" of the feed on an average, then a washerydealing in 2.5 million tons of coal per year willproduce 250,000 tons of rejects. Along with middlings itmay be three times the quantity. This will require notonly conveying equipment for transportation but alsoconsiderable storage space to dump the rejects produ-ced by a washery during its life time. Generally beltconveyors, ropeway and dumping cars fire used fortheir transportation. Sometimes they are pumpedto the storage around directly as produced alongwith the water.Bulldozers, scrapers, trucks etc. are generallyemployed for levelling, spreading, compacting andsealing in the storage yards. Special care is takento compact and store then where there is a dangerof spontaneous ignition.Coal storageCoal-based industries require storage provisions forthe following reasons :(C1 To even out fluctuations in the rate of flowof coal (a) front the mine itself (Ll fromthe transportatiom v"tem.To pray the some degree of blending of theroil feed and pug ile a steady fund to theprociiringr plaant.The central washeri.es using coals from a numberof collieries recloin' storage fawilities for two to fourdays' requirement while poo cr pla its, coke ovensancf steel plant: require the provision for a month'srequirement. Bunkers or bins are generally employedas they are free flowing. The discharging gatesof large bunkers are operated l,v hydraulic, pneu-matie or electric mechanism. In order to facilitatesmooth dischm'ge, bunkers or bins are providedwith vibrating unloaders or chain conveyors. Theyare sometimes provided with remote controls andindicators in order to facilitate loading and unload-ing from a central point.The trend today is to have large opell storageson ground specially for »a^heries, colic ovens andpower plants. Both stacking and reclamation arecarried out by means of long belt conveyorsmounted on gantries. Staclking belts are providedwith travelling tipplers and shuttle conveyors. Oneend of the stacking conveyor is installed underthe receiving hopper while the other end is laidout in the storage y-a1'4 1. l'hc stackers are459 INDIAN CONSTRUCTION NEWSROR5A0[fe3 3: OI5TIP NOMAFT'70300- 36 GOStorage arrangement for Durgapur coke ovens.sometimes provided with adjustable swinging booms topermit uniform distribution in the storage bin as%vel1 as to rrrinirnisc degradation of the materialdischarged.Dumping and reclamation on plane ground arecarried out by industrial trucks, draglines, hull-dozers, power yshovels, grabs mounted on crawlers,gantries, etc.Coal can also be stacked inside V-shaped chan-nels constructed above ground from dirt or earthheaps. The inclination of the sides are designed tohave smooth gravity flow towards the bottom.('oal is discharged through a number of gates atthe, bottom of the channels down to a system ofbelt conveyors installed inside reinforced cementconcrete tunnels erected underneath the storageground. The sides of the storage channels mayrequire pitching to prevent erosion or subsidence.This system of stacking and reclamation hasample scope of blending, and hence it is suitablefor storing coal for washeries receiving widely vary-ing qualities of raw coal from a number ofcollieries. It is suitable for only relatively smallstorage and it is rather costly.In storing coal for longer periods special careis taken to prevent spontaneous ignition which maylead to huge loss.PreparationCrushing, screening and blending constitute some78900-of the major items of handling and preparationplants. In a washery the raw coal may have tobe crushed and screened to produce a number ofsize fractions which may require individualwashing. Each washing unit may again producetwo or more products which may have to becombined and stored in suitable bins before finaldisposal. All these call for considerable amount ofconveying.The present day tendency is to have the washe-ries designed to have gravity flows as far aspracticable. In general the materials are conveyedby belt convenors or vibrating and other types offeeders. The incoming loads are given a movementin the direction of the belt conveyors by meansof suitable chutes in order to prevent degrada-tion, spillage as well as datnage to the conveyorbelts. Bucket elevators and scraper conveyor'sare used to a limited extent, specially wherethe available space is limited. Sometimesthe washing medium serves as carrier for theproducts.When a combination of conveyors are used forthe conveying of coal, it is desirable to have themcoupled to it sequence operation control to preventsudden accumulation of material in any sectiondue to a breakdown in it.It may be pointed out in this connection thatthe cost of conveying equipment of all types in awashery generally amounts to about 300, of thetotal cost of a. washery.AUGUST 1959 459119i sca IA10^L(N4c4 ¢ nl ! II Ii II 11 ii II-Ia0'RR NcY^arPlli C4!tY[IGE(a^. ^. C01_^VIA o MAA15111 52EArrangement of stacking and reclaiming in the ground storage.BlendingFor the efficient and smno(atlr operation of washingunits, the feed should be traded and l ► lendeclproperly so that there are no large variations inthe raw material feed. Blending is also practisedin coke ovens for obtaining standard nnetallurgicalcoke from non-standard coals. In either arse avariety of handling equipment is necessary. Forthis purpose, coal is loaded by shuttle or trippingCollvepors into unrtti-cnlJrlru-trnelrt hies. unloadingit sinrultaneonsly on to tb bank eouvevur leading toa blending in;(c•Icine. 1•arialcle speed feeders aremost .tritable for this purpose as they allow adjust_meat in the rates of unloading from the differentbins and so adjusting, the com p osition of the blend.Blending is mmMr:dly prec•cded 1(^y crushing and sc•ree-n-ing. for both of Nv1 ( ieh a variety ttf apparatus is availablefrom which a selection van he made tc( suit the particularneeds either of the install a tion or the raw nurterial.460 INDIAN CONSTRUCTION NEWS

Mass Handling of Materials

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Mass Handling of Materials

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