Minimills Tenova Web Res

Steel Times International November/December 2013

Minimills

How changes in scrap mix affect Consteel charging of an EAFA description of the various types of scrap available to the EAF operator and howthese affect the performance of a Consteel continuous charging and scrap preheatingconveyor are described. By F Memoli*, J AT Jones*, & F Picciolo**

resulting in damage. If large quantities of densescrap are charged, it may be necessary to oper-ate at lower arc voltage and higher current dur-ing refining in order to ensure that the densematerial is fully melted prior to tapping.

Non-metallic content in scrap leads to dustgeneration in the furnace and increased slagvolume. Gangue also leads to increased slagvolume and increases the requirement for calcicand dolomitic lime additions. In addition, sincefluxes are typically added in the buckets, theslag chemistry will vary throughout the meltingof the charge.

Oil, grease and combustible content in thescrap results in higher energy content in the off-gas stream and, in some cases, will result inhigher VOC content in the off-gas if they arenot fully combusted.

Metallic yield has an important effect on spe-cific energy and raw material consumption.Thus, it is important to ensure that chemicalenergy inputs along with carbon inputs are bal-anced to reduce losses of iron units to the slag.

Layering scrap in the bucket has beendemonstrated to have significant effects onmelting dynamics, thus affecting energy con-sumption. The scrap profile determines electri-cal and chemical energy efficiency. An optimalscrap profile in the bucket affects energy con-sumption by as much as 20kWh/t. In addition,every time the furnace roof is opened to chargescrap, about 10kWh/t of energy is lost due toradiating heat.

Consteel chargingThe Consteel furnace is by its nature both dif-ferent and similar to a conventional EAF. TheConsteel process is continuous, so scrap densi-ty does not affect the number of charges as thescrap is continuously fed into the EAF throughthe side of the furnace. A good Consteel oper-ations is achieved matching energy input toscrap feed-rate. In the early days, that wasachieved by manual control of the scrap feed-rate into the furnace. Nowadays this operationis fully automated, thanks to the weighing sys-tems on the EAF shell, which provides real timeliquid steel weight in the furnace. The key tomaximum throughput in the Consteel is to con-tain the arc in the slag, leading to maximum arc

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*Tenova Core, 100 Corporate Center Drive, Coraopolis, PA, 15108 Tel +1 (412) 262-2240 e-mail [email protected]

**Tenova SpA, Via Monte Rosa 93, Milano, Italy, 20149 Tel +39 (02) 4384.1 e-mail: [email protected]

THE Consteel charged EAF is a very flexibleprocess that can adopt a wide range of scrapmixes in the metallic charge. More than 40plants are currently operating Consteel technol-ogy, producing any kind of steel grades, fromrebar to stainless steel. They are using differenttypes of scrap mixes for their purposes.

Consteel combines preheating the scrapcharge with continuous charging by directingthe off-gas from the EAF through a tunnelthrough which the scrap is slowly conveyed andcharged continuously to the furnace via a sidewall port.

Due to scrap availability country by country,region by region, the Consteel process has toadapt the melting operation to provide the EAFwith the most cost-effective result. In factConsteel units around the world adopt scrapmixes with many types of scrap grades: from thecommon shredded, through HMS#1,HMS#2, plate and structural, Busheling,Bundles, to the less common machine shopturnings, shoveling turnings, heavy turnings,clippings, punchings, HBI, Pig Iron, chargeableingots and ingot butts, foundry steel, hard steel,cast steel, billets, blooms, ladle skull, tundishskull and hot metal. The size of scrap usedvaries from less than an inch to over five feetmaximum dimension, as a result of that, thescrap mix density has a very wide range.

This work discusses scrap mix data collectedin some Consteel plants currently operatingworldwide, and how different scrap gradesaffect the operation, consumption and the qual-ity of liquid steel, whether for rebar or stainlesssteel, and grades between.

Bucket chargingScrap selection plays an important role in anyEAF operations. The characteristics of scrap as density, metallic Fe content, gangue content,oil, grease and non-metallic content haveimportant impacts on the process.

In a bucket charged EAF, scrap densityaffects the number of charges required to pro-duce a heat but also impacts the electrical andchemical energy profiles. Dense scrap can beslower to melt and if aggressive burner and oxy-gen lancing profiles are employed, dense scrapmay deflect the jet back onto the furnace walls

stability and maximum and stable active power.Being a continuous process, the best practice

for scrap charge is always to keep as near con-stant as possible the layer of scrap, in size(height) and grade (mix), in order to have asmooth flow of scrap into the EAF. This con-cept will be described further in the article.

Non-metallic components in the scrap willreport to the dust in the off-gas. The Consteelprocess typically generates about a third lessdust than a conventional bucket charged EAF.The heavier dust is captured in the incomingscrap and is recycled to the furnace.

The high yield in the Consteel process bene-fits from its design. Fluxes, chemical energyinputs and carbon inputs whether in themetallic charge, through injection into the EAFor other must be properly balanced to maxi-mize yield. Consteel operates without any high-ly oxidizing burner flame and the constant flatbath in the EAF helps keep the FeOoxidizing/reducing reactions within the slagitself, so that the proper carbon balancing in theslag can lead to iron recovery and maximisemetallic yield.

Consteel installationsThe total number of Consteel plants to date is45, installed in the United States, China, Italy,Japan, Germany, Greece, Russia, Brazil,Ecuador, South Africa, Morocco, Thailand,Vietnam and South Korea. In addition, threefurther plants are under commissioning orinstallation located in Canada, Mexico andEgypt. The very first Consteel was in Charlotte,North Carolina, USA and started up in 1989and is still in operation.

Today worldwide installed capacity is over40Mt of liquid steel per year, more than a quar-ter have been installed in the past three years,which demonstrates the success and acceptanceof the technology as a reliable and dependentalternative to the conventional bucket chargeEAF (Fig 1).

Consteel installations are characterised by arelatively low installed active power factorwhich increases with heat size (Fig 2). The cor-relation factor between the two parameters isvery high. The data reported in Fig 2 is relevantto the existing installations and show the Active

The Consteel scrap preheater andcontinuous scrap charger

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Power used in a Consteel being on average 0.53times the heat size of liquid steel. That is aremarkable correlation, considering the signifi-cant difference between the various installa-tions in terms of steel grade (from rebar tostainless steel) and scrap mixes. This is perhapsthe most important design difference between aConsteel and a conventional EAF. In UltraHigh Power electric arc furnaces bucketcharged the relationship between active powerand heat size can be as high 1:1. In contrast,Consteel reduces the ratio to 0.5:1.

In an analysis conducted in 2011, relevant tothe importance of the size of the hot heel in aConsteel EAF(1), it was demonstrated that forthose units that keep over 46.5% of metal in theEAF after tapping the productivity is over 2t/hper active MW.

The data in Fig 3 is from a population of 27AC EAF Consteel installations. Data was col-lected from plants that are operating with a pro-ductivity or plant utilization of over 80% of theplant capacity, so that power off time for suchplants is only affected by standard maintenancedelays.

Fig 3 is an updated version of the data. 70%of installations have a specific productivity ofbetween 2.0 and 2.5t/h/MW and all Consteelsthat operate with a hot heel greater than 46.5%of tapping weight have a specific productivityhigher than 2.0t/h/MW.

For a conventional UHP-EAF to reach a spe-cific productivity above 2t/h/MW it has to have

a very powerful transformer, where the activepower vs heat size relationship is over 1:1.Correlating the data in Figs 2 and 3, in theConsteel installations this relation is halved.

Scrap grades charged There are often two main questions regardingthe scrap charge to a Consteel EAF.What are the scrap grades that can be

charged in a Consteel? and

What is the maximum dimension of scrap that can be charged to a Consteel?

To the question on scrap grades, the answeris any type of commercial grade of scrap, allinternal recycled scrap and generally all theother types of metallic raw materials that can becharged into a conventional EAF. So in terms ofscrap grades there are absolutely no limitationsor restrictions to the Consteel charge. Even thesmallest Consteel in operation today can chargeany commercial scrap grade and dimension.

To answer the second question, regardingscrap dimension, the sole rule to be taken intoaccount is the distance between the Consteelpan and the electrodes, as shown in Fig 4.

For the Consteel process, thanks to its higheramount of hot heel, it is easier to melt largerpieces of scrap than in a conventional EAF ofthe same size. The right use of the hot heel,combined with good bottom stirring, is one ofthe keys of the performance of Consteel plants.

Having addressed these main two questions,there follows a list of scrap grades most com-monly used in Consteel plants. These are in noway different to the scrap grades normallycharged in any conventional bucket chargedEAF. The codes indicated are relevant to thelatest scrap specification published in theguidelines of Ferrous Scrap by ISRI(3).

Heavy melting steel (HMS)No 1 HMS Steel scrap inch and over in

thickness. Code 200, 201 and 202, individualpieces not over 60 x 24 inches (Fig 5).

No 2 HMS Steel scrap, black and galvanized,1/8 inch and over in thickness, Code 203, 204, 205 and 206, size over 60 x 18 inches.

Fig 6 shows HMS1 and HMS2 charged on aConsteel conveyor on a regular basis. This illus-trates that it is possible to charge the Consteelconveyor with large pieces of scrap. In fact, thewidth of the conveyor in Fig 6 is over 6 feet(1829mm) and some scrap pieces are almost aslong as the width of the conveyor. These aredefined as oversized where specified by theISRI codes 200-202.

The preferred way to charge HMS scrap in amix of scrap types on a Consteel is on the toplayer as this type of scrap of relatively high den-sity and can be heated by the off-gasses comingout of the EAF more effectively. By positioningthe HMS as a top layer, it will be directlyexposed to the stream of gasses and heat will be

November/December 2013 Steel Times International

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Fig 3 Correlation between hot heel as percent tapping size and specific productivity astonnes per hour per active MW

Fig 4 Distance between the Consteel con-necting car pan and the closest electrode inthe EAF

Fig 1 Worldwide cumulative installed capacity in million metric tonsper year from 1989 to 2013

Fig 2 Correlation between heat size (metric tonne) and activePower (MW)

45

40Mtpy

35

30

25

20

15

10

5

0

89 91 93 95 97 99 00 02 04 06 08 10 12 13

180

160

Act

ive

pow

er (

MW

)

Active power = 0.53 heat size

R2 = 0.94

140

120

100

80

60

40

20

00 50 100 150 200 250 300 350

Heat size (t)

2.4

2.2

2.0

1.8

R2 = 0.657

1.6

1.4

Hot heel as a percentage of tapping size [%]

Spec

ific

prod

ucti

vity

[t/

h/M

W]

32% 34% 36% 38% 40% 42% 44% 46% 48%50% 52% 54% 56% 58% 60% 62% 64%66%68% 70%



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transferred to the scrap by radiation and also byconvection, enhancing the heating effect. Intests conducted in a Consteel installation sever-al years ago, the temperature that can bereached is up to 800C on average on the toplayer.

Moreover, this type of scrap is not creating aphysical barrier to the heating gas so heat canpenetrate to the bottom layers of lighter scrap,producing an additional heating effect.

BushelingCode 207, Clean steel scrap, up to 12 inches(250mm) in any dimensions, including new fac-tory busheling.

Bushelings work in a Consteel in almost theopposite way to HMS. They are low density andnot so easy to heat by the off-gasses. In severalanalysis tests and campaigns, it has beendemonstrated that positioning busheling as atop layer on the Consteel charge conveyor cre-

ates a barrier layer against heat penetrating tothe scrap beneath. Busheling tend to reflect theheat. Thus, this scrap must be charged on thebottom of the conveyor and should be coveredwith other types of scrap such as HMS orshredded (Fig 7).

The low density of busheling is not an issueprovided it is correctly positioned and it is cur-rently being charged at several Consteel plants,in particular those producing high quality steelgrades. Busheling and also even lower densityscrap such as turnings, can make up 50% of thecharge.

BundlesCode 208 and 209, No1 bundles weighing notless than 75lb/cft (1201kg/m3)

While a bundle is a cleaner metallic scrap, itis more difficult to melt, being less porous andmore compact than heavy scrap or bushlings(Fig 8a & b). Whether to use it or not does not


Fig 8 a & b Bundles (a) No 1 (b) No 2

Fig 5 Heavy Melting Scrap Nos 1 & 2 Fig 6 HMS 1 & 2charged on aConsteel conveyor inthe USA

Fig 7 Busheling inthe plant of ORIMartin, Italy

depend on the EAF charge method, it is more adecision relevant to the scrap quality mix, thesteel grades to be produced and so on. SomeConsteel plants are charging high percentagesof bundles for that reason.

In a Consteel conveyor, bundles are chargedby positioning pieces at a certain distance fromeach other, so that when they arrive into thefurnace and are submerged into the hot heelthey melt quickly by convection in the liquidsteel.

A general understanding is that large bundlesmay constitute a problem and small bundles arepreferred, as problems with big bundles arewell-documented as: blow-back of oxygen if abundle should fall in front of a burner (but thatcan happen for any type of large plate scrap);poor melting efficiency (smaller scrap pieces arealways better than large scrap pieces, in partic-ular when there is not enough hot heel); andthe risk of breaking an electrode when a bundlecaves in on an electrode.

Most melt shops try to minimise the use oflarge bundles by using busheling and alternativeiron units (pig iron, DRI, HBI) to achieve thedesired residual levels in the steel.

For a moderately large conventional EAF something between 100 and 200t heat size running a steel mix aiming for 0.12% Cu orlower as a residual element, especially on a sin-gle bucket charge furnace, the problem is main-ly related to scrap density. To achieve such cop-per levels, many bundles have to be used if pigor other scrap substitute are not charged. It isthen not possible to charge all bushelingbecause of the large volume these occupy. Butusing bundles can create cave-ins. The regularbundle size is 3ft x 2ft x 2ft, (90cm x 60cm x60cm) but these are getting harder to find asmany balers in the US now make 2.7ft x 2.7ft xvariable 3-4ft (81cm x 81cm x 90-120cm).



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Using a larger bundle size may, however,increase power requirements and incidents ofelectrode breakages.

This is where Consteel comes in to help: bun-dles can be placed on the charge conveyor inthe desired amount and travel to the EAF with-out mayor issues of causing electrode break-ages. At the same time, busheling which aregenerally more affordable than bundles canbe charged as well without any problem, sincelow density in the scrap mix is corrected by theConsteel technology by means of adjusting thespeed of scrap on the conveyor.

Shredded scrap and clippingsShredded scrap (Code 210 and 211) has anaverage density of 50 to 70 pounds per cubicfoot (8001121kg/m3) and Code 212 has anaverage density of 60 pounds per cubic foot(961kg/m3) (Fig 9).

Shredded scrap is the scrap grade generallyconsidered very easy to charge in both aConsteel and in the conventional bucket chargeEAF. Similar to heavy melting scrap, shreddedis a type of scrap that is easier to heat with offgasses as the heat of the off gas from the EAFcan permeate the charge on the conveyor andreach the bottom layers of the scrap, enhancingthe heating effect of the Consteel heating tun-nel. Shredded is charged on a Consteel bymeans of standard crane magnets or grapples,and more recently it is also charged directly bybelt conveyor, as happens, for example, in someConsteel installations in North and SouthCarolina and elsewhere.

Shredded is indeed a type of scrap that fitsthe charging mode of a Consteel very well. Itcan be accommodated in the charge conveyor

(as it accommodates itself in any bucket) fillinggaps and creating a continuous layer of metalliccharge. The crane operator can use shredded tocomplete the charge of previously chargedscrap of different type or can use shreddedalone, filling the conveyor to the target chargingheight.

As can be appreciated in Fig 10, for thisstudy some specific data has been collected indetermine the correlation between the percent-age of shredded scrap and total energy con-sumption (electrical + chemical mainly decar-burisation reactions happening in the liquidsteel during supersonic oxygen injection).

The data has been collected from a group ofsimilar N American steel plants below 100t heatsize and all producing similar steel grades,mostly rebar, in three-phase AC furnaces.

The data reported in Fig 10 represent aver-ages from long campaigns from one month tosix months, so the number of heats that havebeen analysed is in the range of several thou-sands.

This correlation, even if not reaching valuesthat can lead to a definitive conclusions, is stillhigh for the steel industry. Nevertheless, itshould be always remembered that a correlationdoes not imply causation.

The reality is that cause and effect can beindirect, or due to confounding variables, andso the assumption of causation is false when theonly evidence available is a simple correla-tion(4). Thus the fact that a higher percentageof scrap indicates a lower total consumption ofenergy should not be directly interpreted as acause.

The trend indicated in the graph shows thatfor every percentage point of shredded scrap in

the mix from 0% to 20% there is a decrease oftotal energy consumption of between 0.15% to0.20%, and when the shredded percentageincreases from 20% to 40% the decrease ofelectrical energy is less pronounced at 0.10% to0.15%. At over 40%, for every additional per-centage point of shredded in the mix, thedecrease of energy consumption is only 0.05%.

So even if the correlation indicates thatincreasing the shredded in the mix provides acertain benefit in terms of energy consumption,the effects are not so dramatic to indicate thatshredded should be the preferred scrap gradeto be used in a Consteel. On the contrary, it iswell understood that for some steel grades, con-sidering the amount of undesired residuals inshredded, its percentage in the mix should belimited, as happens for any EAF.

Punching and plate scrapCode 234, punching or stampings, plate scrap,and bar crops is material cut to 12 inches (30cm)and shorter and at least 1/8 inch in thickness orpunching or stampings under 6 inches (15cm) indiameter and any gauge (Fig 11).

This material in the Consteel has a behaviourin the middle between busheling and HMS.Depending on the thickness and the density, itmay heat up readily in the Consteel tunnel, butif the plate covers scrap beneath, it will create aprotective layer. So it should always be used inthe middle or bottom of the conveyor.

TurningsCode 219 and 220, machine shop turnings,Code 221 222, shoveling turnings; Code 245,246 and 247, alloy free turnings. Code 251,short, heavy steel turnings (Fig 12).

Fig 11 Punching and plate scrap Fig 12 Turnings

Fig 9 Shredded scrap Fig 10 Correlation between percentage of shredded scrap and totalenergy

1.08y = 0.150x2 - 0.212x +1.040

R2 = 0.6861.06

1.04

1.02

1

0.98

0.96

0.940% 10% 20% 30% 40%

Percentage of scrap in the charge mix of rebar Consteel plants

Tota

l ene

rgy

cons

umpt

ion

norm

alis

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50% 60% 70%



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In a Consteel system, thanks to the continu-ous flat bath conditions throughout all of theheat stages, and also thanks to the fact that theincoming material melts by immersion in theliquid heel, there are no limitations on theamount of pig iron that can be charged perheat. The maximum decarburisation rate can bemaintained throughout all the heat and theelectric arc efficiency is not affected by its highdensity. In addition, the increase of the averagescrap mix density enables a lower conveyorspeed, which leads to longer scrap residencetime in the tunnel with benefits in terms ofheating the charge.

Several Consteel units with a need for cleanmetallic raw material, regularly use a high per-centage of pig iron (about 25%) without havingany issue with decarburisation delays and min-imising the oxygen consumption thanks to theFeO-C relation being much closer to equilibrium.

Stainless Ni-pigA Consteel unit that produces more than300kt/y of stainless steel (3- series), charges its60t furnace with 100% Nickel-pig iron, a rawmaterial with the physical characteristics of theregular pig iron plus a high content of nickel(up to 14%), as shown in Fig 14. Thanks to thismetallic charge, the conversion costs are signif-icantly lower than when using stainless steelscrap, especially in those countries where theavailability of the stainless scrap is limited. Sucha dense charge mix completely without scrapcannot be handled by conventional EAFs, bothregarding electrical energy transfer and refrac-tory related issues, as well as due to decarburi-sation constraints.

Another example of a high amount of pigiron charge in a Consteel is the case ofVallourec & Sumitomo Tubos do Brasil (VSB)

that has been designed with a nominal scrapmix that has about 40% of pig iron(5).

Other scrap and raw materialsOther types of scrap generally charged on aConsteel conveyor include: Plate and structural steel; Internal returns such as billet crops, bloom

and forge crops, axle, slab, heavy plate and heavy forge crops;

Bar crops and plate scrap, forgings, bits, jars,tool joints;

Steel castings, chargeable ingots and ingot butts, foundry steel;

Hard steel cut, automotive steel consisting ofrear ends, crankshafts, drive shafts, front axles, springs, gears.

Optimised scrap charge Considering what has been said for each mainscrap category, a few simple guidelines can beindicated to optimise the charge of scrap ontothe Consteel conveyor.

There are charging rules also for the con-ventional bucket charge EAF, but these are def-initely different from those that will optimisethe Consteel process in terms of heating effi-ciency and in terms of the melting process.

The 3-D guidelineScrap materials can be categorised followingthree main parameters density, dimensions anddirtiness:

Density: the less dense the scrap is, the morereadily will it increase its temperature in theheating tunnel, so very light scrap is generallycharged on the lower layers of the conveyor,with high density scrap on top, to achieve directheat radiation and convection from the hotgasses. This will avoid melting the light scrap onthe conveyor and will enhance the heatingeffect and the average temperature of the scrapon the conveyor.

Dimension: as for the density, also dimensionplays a role in the heating time for a piece ofscrap. Large pieces of scrap tend to heat-upmore slowly than small pieces, and that is whylarge pieces of scrap (which are also usuallymore dense) are placed in the top layers of theconveyor, while small pieces would be on thebottom. This general consideration though hasto be seen in connection with the other majorguideline of evenness for scrap height on theconveyor, as described below.

Dirtiness/Cleanliness: clean scrap, bushelingsfor instance, produces a mirror effect on heat-ing, deflecting light/radiation and create a pro-tective layer of scrap against heat transfer. Thedirtier the scrap, the better it is for heating. So


The use of turnings in electric steelmakinghas always been very limited, due to the verylow density of this type of scrap and the issuesarising from the high content of oil and otherflammable components that create difficultieswith bucket charge. With the introduction ofConsteel technology, such issues have beenresolved.

A very important matter is avoiding turningsbeing exposed to the hot gasses in Consteel asturnings tend to melt if directly in the stream ofthe hot flue gasses, and melting can block theflow of scrap in the tunnel. So turnings must becharged on the bottom of the conveyor, thencovered with other scrap. Turnings will thenproceed steadily throughout the heating tunnel,increasing in temperature by conduction fromscrap heated above, until the turnings enter theliquid heel in the EAF where they melt rapidlydue to their very large surface area.

In test campaigns carried out in Italy, entiresequences of heats were conducted with over50% of turnings in the charge with no issue onthe heating operation, nor tap to tap time. Infact the low density is not a problem for theConsteel. The lower is the density the faster willbe the charging speed. In fact scrap can travelup to 8m/min on the conveyor, and dependingon the conveyor cross section, the flow rate ofscrap into the furnace will always meet the EAFproductivity requirements.

It is well noted that a high percentages ofturnings are not suitable for all steel grades.From a cost stand point, it is recommended toincrease as much as possible the percentage ofturnings, as these are a very inexpensive scrapsource and so permit the plant to reduce itsaverage cost for metallic raw materials.

Pig IronThe main purpose of charging pig iron in theEAF is to dilute the residuals contained in theregular scrap to the target requested by thesteel grade to be produced.

In addition to that, the pig iron providesmore chemical energy thanks to its high carbonand silicon content, as well as keeping a higherlevel of tapped carbon. Thanks to its high den-sity (approx 3.6t/m3) it allows a decrease in thetotal scrap charge with possible benefits interms of filling the EAF and reducing the num-ber of buckets per heat (Fig 13).

Due to its high carbon content and high den-sity the amount of pig iron that can be chargedinto a conventional EAFs should be well bal-anced taking into account the effects of its highdensity on the electrical energy transfer effi-ciency and the maximum obtainable decarburi-sation rate.

Fig 13 Pig Iron charge in a Consteel Fig 14 High Ni pig for stainless production

Fig 15 The three defining parameters forscrap on a conveyor


dirty scrap tends to be positioned on the toplayers of the conveyor.

Hence, considering the three axis diagram inFig 15, the centre of the axis will define a typeof scrap of low density, small dimension andvery clean (turning, busheling). The more thescrap to charge is close to the centre of the axis,the deeper it should be on a Consteel conveyor.

Evenness for scrap heightA guideline of the same importance, if not moreso, is relevant to how even and constant the toplayer of scrap is on the charge conveyor.Maintaining a constant scrap height on thecharge conveyor permits the automationprocess to perform at its best.

An EAF equipped with Consteel always sitson load cells that read the weight of the liquidsteel inside the furnace in real time. One of thestandard methods of operation of the Consteelforesees the calculation of the specific energyconsumption in real time, by dividing the totalenergy input and the actual weight.

The level 2 control indicates to the furnaceautomation the correct profile of specific ener-

gy consumption that the furnace should have ateach moment of the melting process, in orderto optimise the steel temperature and moreimportantly the slag conditions, which are cru-cial to ensure the arc is covered to protect therefractories and maximise the active power andpower factor.

Changes in density on the Consteel conveyorwill produce variations in the real-time specificenergy consumption calculated, and theautomation will then change the conveyorspeed accordingly to maintain the target valueof specific consumption.

By its nature the Consteel process is a contin-uous process and the steadier are the opera-tional parameters (electrical energy input, oxy-gen flow, charging rate), the better will be theresult of the heat.

Variations of scrap density on the conveyorhappen because of two factors: changes in thedensity of the scrap and potential unevencharge of scrap along the conveyor scrapcharged leaving holes in between, or waves ofhigher piles of scrap.

Scrap charge methodology is as important in

Consteel as much as it is in a bucket charge, soin order to reduce the variations of density andto achieve better operational results, plantsusing Consteel instruct their crane operators tocharge the conveyor evenly. The typical type ofscrap that is used to fill the gaps is shredded.

References1 F Memoli, et al, The Evolution of Preheating andthe Importance of Hot Heel in Supersized ConsteelSystems, Iron & Steel Technology, Jan 2012, pp 70-782 W Sanwu, et al , Application of Hot Metal Chargingfor 90t Consteel- EAF at SGIS, ConsteelInternational Symposium Proceedings, MetallurgicalIndustry Press, Beijing, 2004, pp 39-41 3 Scrap Specifications Circular 2013, Institute ofScrap Recycling Industries Inc (ISRI), 2012, pp 16-184 web URLhttp://rationalwiki.org/wiki/Correlation_does_not_imply_causation5 Lus Gustavo de Oliveira Amaral Mello et al , VSBoperates first Consteel EAF Meltshop in Brazil,Metallurgical Plant and Technology, Verlag StahleisenGmbH, Dsseldorf, 03/2012, pp 40-47


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