The author's chief interest  in  pilot  plants is as a

means of practical  instruction.  At the Banaras Hindu University a number of pilot plants have been installed 

so as to impart  some  practical Idea of  metallurgical processes to  final  year  students. These pilot plants include a sintering plant, several  small size cupolas,

an LD  converter,  a basic  lined side blown converter, indirect arc furnace & high frequency electric furnaces. The latest addition to this range of pilot plants  is a small scalp Edwards vacuum melting unit.

     In addition to their use  for instructional purposes,

it is hoped, as candidates present themselves, that these plants will be more fully employed in post- graduate  res-earch, which it is felt will be of considerable importance to the development of the iron & steel industry in India. Post-graduate research, which it is felt will be of consi-derable  importance to  the  development of the  iron and steel industry in India. Post-graduate work of this nature must play an important role in the provision of thoroughly trained personnel  for  the  rapidly  growing  industry in

India

Bashforth, G Reginald

Swarup, D

English

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PAPER NO -THE H L,TIONSHIP OF !'ILOT PLANTS TOFULL SC1,LE 0^'ER.,TION :.D. Swarup &G. R. Bashforth,College of Mining and Metallurgy,Banaras Hindu University,VJJt NkSI.6The authorst chief interest in pilot plants is as ameans of practical instructiDn. tit the.Banaras Hindu University anumber of pilot plants have been installldyso- as to impart somepractical Idea of metallurgical- processes to final year students.These pilot plants include a sintering plant ,;several small size cupolas,an L.L converter, a basic lined side blown converter, indirect arcfurnace and high frequency electric furnaces. The latest additionto this range of pilot plants is a small scalp Edwards vacuummelting unit.In addition to their use for instructional purposes,it is hoped, as candidates present themselves,•that these plantswill be more fully employed in post-graduate.resnarch, which itis felt will be of considerable importance in the developmentof the iron and steel industry in India. Post-graduate research,which it is felt will be of considerable importance to the develop-ment of the iron and steel industry in ;India. Post-graduate workof this nature must play an im,.)ortant role in the provision ofthoroughly trained personnel for the rapidly n_ rowii g industry inIndia.Both these ap-ilicati -ns of pilot plants, however,demand a careful consideration of the relationship between theresults obtained thereon and the results which nay be anticipated infull , scale operation . The reducti _ n of plant size .f equentlynecessitates a corresponding reduction of particle size, which mayseriously affect such physical prop rties as porosity , specificgravity and reducticibility. In thermal processes the smallquantity of metal handled may aggravate thermal losges cue toradiation and conduction , whereby time factors are of vitalimportance.The results obtained an pilot sinteringlants j wouldappear to bear a reasonable relationship to those'which can beanticipated on a full scale plant, excent that the smaller surface<ahea should assist more uniform and immediate ignitidn. Since theratio of cross-sectional area to periphery is lower in .lot plantsas compared with full scale ,slants, one might anticipate: a greateramount of fused material as a result of less resistance to thetravel of the sintering zone ?sound the periphery. It would appear(*) Paper for presentation at the Symposium on Pilot Plants inMetallurgical Research and Development - 15th to 18th February, 1960,Jamshed ur.Not to be reproduced in any media . (C) National MetallurgicalLaboratory, Jamshedpur.Doc: P.7.however, that in small scale plants the sides of the ,pan hasfrequently a chilling effect, which tends to increase the percentageof returned fines. In general, as found by Voice, Ling & Gledhill,there is reasonably good correlation between the results obtained on4 lot plants and those obtained-in full scale operation.Rid,gion, Cohen & Lang demonstrate that both heamatite andmagnetite concentrates can be successfully _)elletized on a pilot plantscale, but they do point out that the translation of the process to acommercial scale may introduce problems peculiar to larger units.Much of our existing knowledge concerning distribution ofstock intheblast furnacQ has been derived from experiments on smallscale models, with especial reference to the work of Saunders, & Wild,Wild and Diamond. It must be remembered, however, that this workop small scale models does necessitate a corresponding reduction ofparticle size, which may seriously affect the specific gravity,of thematerials employed, thereby affecting the type of distributionobtained. In recent experiments at Banaras it was found that thebulk density of the coke as it would be charged into the blastfurnace was 281bs. per cu. ft., At when this material was reducedto ." to correspond to the size of the pilot plant, the bulk densitywas increased to 34 lbs. x:r cu. ft., thereby altering its relation-ship to the bulk density of the iron ore and limestone used in theexperiments. This feature Would lend to give a completely differentdistribution pattern.Tesch & Hahnel suggest that unfortunately much of the workon distribution in the blast furnace may not reflect the actualConditions which exist, especially since the models employed havesometimes been too small, and due consideration has not been given •to the upwards flow of gases. In small scale work of this natureit is difficult to assess the affect of chemical transformation ofthe gases, reduction :f the oxides, the thermal changes and similarfactors. Perhaps, however, these items are not so vitally_importantin such studies, since the fundamental purpose of these studies is toascertain the distribution of the stock in the upper part of thefurnace as a guide to its possible distribution in the reduction andsmelting zones of the furnace. It is interesting to note, however,that the apparatus employed by these two investigators to studydist:libuti n in the blast furnace consisted of a receiver representingthe top of a blast furn_.ce, which was 41 3" in diameter with aneffective height of 51 7". The bottom of this receiver was perforatedto allow the passa e of blast from an air box located beneath.The difficulties of investigating thermal 7rocesses inpilot plants is demonstratod by the work of Sims & Toy. In theirexperiments, using a 1000 lbs. capacity side -blown basic-linedconverter, they did demonstrate that steel could be produced bysurface blowin _ basic pig iron .with a blast of air. It was , however,necessary to preheat the hearth or converter to 1540°C owing to theheat losses associated with such a small unit.In this pilot plant, which was in fact a small side-blownconverter, they demonstrated the possibility of converting basic pig'iron containing-;:4s 3 : Doc; P.'I.Si. S. P. i1n.•3495 1.10 . 0.035 0.31 .1.95Into blown metal containing:-Si. S. P . I1n..0109 under 0.01 0.015/ 0.015/ 0.06/0.E0.027 0.x35in the course of this refining, the eliminati ;n of impurit;iosresulted in a tem;xr. ature incr: ase o 200°C (1450°C being the Ifbtmetal temper:.ture and 1650°C being the temperature of the blow ifietal)at the same time the tempor,.ture of the hearth or converter had beenincreased 110°C from its initial temiierature'of 1540°C.This work is of .oarticul z interest since it. did demohs-cratethat the conversion of basic )ig iron, containing approximatelyP 0,50%, can be converted into high cuality steel in a basic-lined.aide-blown converter. Commercial scale trials, using 25 to 30 tongof hot metal, corraboratec? the findin,Ys of this °xoerimental work..Fifteen heats of 25/30 tons ca,dacity were made -in a converter linkwith magnesite and two typical results are shown .n Table 1.T,:BLE -Example C. Si. S. P. Yn,1. Hot metal 4.39 0 . 96 0.031 0,223 2,C$.blown -metal 0.015 0.003 0 .019 0.008E. Hot metal 4.46 0 . 70 0.039 0.214 1.58Ladlesam,)le (rim-ming steel ) 0.05 0.05 0. 013 0 . 020 0438ySimilar results have been obtained at the Ba naras HinduUniversity ernleying small scale L-L and basic -lined, side -blownconverters. It has been shown that the relative rates of c'rh.n and,7hosl)horus removal dedends on sl.: ,g conditions and the ;)ressure.oflast or oxygen impingement. Not only is it yossible to produce highb 'grade steel by these methods, but it is also possible to 6e "'hos-k.criseordinary Indian pig iron and by suitable alloy acditions to producea low Dhos ; )hcrus oAg iron, which c^.n be beneficial emoloyod in themanufacture of ingot moulc,s , rolls =. nd Similar ar plic ^tiors.ti survey of pilot ,plant work does appear to stress theimportance of due consider :ti on being given to o lant si.-e whenantici pating the possible translati )n of such results „o full ocale: 4 :Doc: P.7.operation. In some cases the lack of precise control associatedwith large commercial units ag ravate the translatio.:o,n,• whereas inother cases the larger bulk of metal being handled, thereby reducingthermal losses, may simplify such translation. Perhaps the best 'capacity for a pilot plant is the smallest unit which can be operatedcommeroially. It is also surggested that some of these commercialsize pilot plants csuld, in the oresent state of Indian economy,be successfully employed on a commercial basis.klthough some large capacity,. integrated iron and steelplants are essential to national economy, there is also opportunitiesin certain localities for the adoption of smaller, less-mechanisedUnits. The installation of this type of plant would offer thefollowing advantage,:.:-(l)(2)The conueriation of foreign currency.The provision of employment for a largerlabour force.The utilisation of lower grade raw materials.The provision of a media for training:-(a) engineers in the design and construction ofiron and steel works plant and equipment, whichshould also fit them for the better operationand maintenance of such plants.(b) metallurgists and operatives in the basic artand science of iron and steel manufacture, and itssubsequent mechanical treatment.$rrall Scale Commercial 'lants:The authors suggest that these -,llants should have anannual capacity of 140,000 tons of pig iron, oroduced in hand-chargedblast furnace , having; hearth diameters of 10'0". The design of Suchfurnaces is based on similar furnaces which were employed inStaff ordihiro , U.K. until comparatively recently for the productionof high grade and special pig iron from relatively low grade rawmaterials . The reductio n in mechanisation would reduce the capitalcoat of these furnaces, but would entail a higher labour cost, whichis not a serious f_-a_ture in the present state of Indian economy. 'These furnaces have a bosh diameter of 1410 and a heightof 601011, which would permit the employment of a lower grade rawmaterial. Furnaces of this design mif;ht be of particular interestin districts whore lignite coke is available, or where a limited.amount of imported coking-coal can bo blended with local non-cokingcoals, such as Southern India, Rajasthan and certain parts of MadhyaPradesh. This wi(',or cispersion of the industry possesses obviousnational advantas-es.t, blast furnace of this capacity should be capable, 'operatin , on hot blast , of -)reducing 200 tons per day, and the'idealunit would e two furnaces with a combined annual capacity of 140,000^^1 ra •' 1 M fS wi '1 "' 11q•5:Doc: P.7.tons . This hot metal would be stored in drum type metal mixersfor subsequent conversion into steel in basic-lined, -side-blownconverters.Harrisof, Newell & Hartley have demonstrated the'hihrates of productivity and the high quality of steel which can beobtained in the acid-lined side-blown converter operating with oxygenenriched blast. At the conclusion of this paper they forecast thatthis :practice will find increasing application for bulk ingot-steelproduction. One limitation of the process which they describe,however, is its inability to refine phosphoric pig iron, but Sims & 'Toy have shown that this difficulty can be overcome by the employmentof a basic lining. This fact has been confirmed by pilot plantwork at Banaras Hindu University.One great advantage of the side-blown converter, asshown by Fassotte, is the fact that most of the carbon is burntto carbon dioxide, whereby the maximum heat from the eliminationof that element is achieved. As compared with the L-D converter,the Kaldo converter or the Rotor furnace, the side-blown converteroffers the additional advantage of the more ready adjustment at theangle of blast impingement and the thickness of the slag, both factorsaffecting the relative rates of carbon and phosphorus elimination.b low pressure of impingement and a thick slag covering favours theelimination of phosphorus; whilst a higher blast pressure and athinner slag covering, which can be readily obtained by rotating theconverter to an angle of 45° from the vertical, a:ccoieratesdedarburisation.The capacity of the converter is 10/15 tons, which witha blowing time of 30 minutes per heat, should give a productivity rateof 15 tons/ converter/ hour. It follows that two converters operatinga five-day week at an availability of only 70% would produce:-15 x 24 x 5 x 2 x 0.70 = 2 ,520 tons per week.They would, therefore, be able to consume the output of pig ironfrom the two 10'0" d iamrtter, hand-charged blast furnaces recommended.The overall capacity of the plant has been influenced by theanticipated consumption of oxygen, which it will be noted would beaceomodated by an oxy en p?lnnt capable of producing 50 tons per day.It is further recommended that the steel should either becast into 6" to 9" square ingots for subsequent treatment in a 28"rolling mill, or continuously cast into 9" square billets in acontinuous casting machine which is similar to the machine incommercial production at Cail in France. In b,th casesthe productof the first stage would be further rolled in smaller millsaccording to the local market requirements.It is estimated that the capital cost of a plantof this type par ton of annual output would be about 60% of thecapital cost of a more conventional and more highly mechanisedplant oar ton of annual output. It is not suggested that thistype of plant should completely replace the more mecl-anised6 : Doc; P.7.and large integrated iron and. steel works, but it is consideredthat plants of this type anc cayacity wouY be of national benefitin certain districts as a.means of utilisini* lower grade, localraw materials anr'. meeting local' demands for iron and steel, therebysaving transport costs. They would also ;)rovic'e an excellent mediafor the traininz; of iron and steel works personnel.ISKB.

The Relation of Pilot Plants to Full Scale Operation

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The Relation of Pilot Plants to Full Scale Operation

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