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Recovery of powdery ferrous waste through pelleting

ADELA SUSANA TODORUT, SOCALICI ANA

Engineering and Management Department

Polytechnic University of Timisoara

5 Revolutiei Street, Hunedoara, postal code 331128ROMANIA

{todorut.adela,virginia.socalici }@fih.upt.ro http://www.upt.ro

Abstract: - In the steel industry, beside of primary products, results amount of powder waste which createsproblems for recovery on the first step, due to in corresponding granulometric composition and on the otherstep due to the content of heavy metals in their composition. The powder waste used in experiments in thispaper it was processed by pelleting process, following a strength process of pellets using a lot of diagrams,modifying the heating time of their. The results of experiments were processed in Excel program, resulting in aseries of graphical and analytical correlations between the diameter of pellets and compressions strength, being

presented for each variant.

Key-Words: wastes,pelleting, powder, compressiveresistance,process, diameter.

1 IntroductionIn steel production flow, economic agents frommetallurgy, generates waste whit iron content inappreciable quantities being continuous andproportional to the achieved production [1].

This quantitiesresult from the current flowsof production is adding to the quantities stored inponds or tailing dumps [4].Due to the large quantityof existing waste and useful component of the Fe,have imposed looking for some ways to manage andrecycle them.[3] Landfill is used increasingly morein the world and in our country [6]

From all the waste generated in the steelindustry, powder wastes have raised problems intheir recovery, due to the grain size compositionnamely the fine scattered being in a big quantity,and on the other hand due to this heavy metals in

their composition [1].

2 Problem FormulationThe powder wastes results from the steel industryare: dust and sludge of agglomeration, furnace dustand sludge, dust and sludge of converter, steelworksdust, mill scale and sludge mill scale.

The methods processing of waste,mentioned above, are used: mechanicalagglomeration processes: briquetting and pelletingand thermal sintering processes: agglomeration and

sintering [4, 5]. It was chosen the way of processing

these wastes very fines which tracks the

transformation of their in innards through

pelleting.This procedure enables the development

of products after recipes that may contain oneor more powder waste. This procedure is simpleand that doesn't involve too many processing costs.In experiments in this paper we have chosen as rawmaterial for processing this following waste:steelworks dust, blast furnace dust, red mud, ashfrom thermal power and it was used bentonite asbinder. Waste has undergone surgery for granulationclassification and using only particles with size lessthan 125 m.

As preparation operations in the processingflow of the pellets are: granulation classification,

dosing and mixing. We have processed pellets byfollowing the recipe presented in fig.1, fig.2, fig.3,fig.4 featuring granulation waste compositions used.

Superior waste recovery metals in

general and in particular small and powdery, isan important issue, because turning them into

products, so in economic goods may lead to arational exploitation of energy resources and

raw materials, thus ensuring the needs of bothhuman society and environmental protection,

major problem at the end of the second

millennium and early third millennium [7].

Mathematical Modelling and Simulation in Applied Sciences

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Fig.1. Component of recipe

Fig.2. Granulation analysis of furnace dust

Fig.3. Granulation analysis of steelworks dust

Fig.4. Granulation analysis of red mud

3 Problem SolutionsFor a more stringent control of exhaust waste forprocessing pellets, previously have been placed in

the oven to remove moisture, for five hours at atemperature of 120C increase the temperaturemaking gradually in these 5 hours.

For the forming of pellets, has been usedwater in a proportion of about 20%, and the additionof binder in this case is 2%.

The pellet was subjected to the sievingprocess, with a site where the diameter of mesh is10 mm. Furtherexperiments took two directions: apart of these pellets have undergone the process ofdrying naturally and the other part has beensubjected to the process of drying in the oven at a

temperature of 100 C.Both parts of pellets dried in oven and dried

naturally were hardened in a furnace with resistance.Aspects from the phase of laboratory experimentsare shown in fig. 5, fig. 6, fig. 7, fig. 8, fig. 9, fig.10.

Fig.5. Drying the mixture

Fig.6. Screening pellets


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Fig.7. Drying pellets

Fig.8. Hardening pellets

Fig.9. Metalized pellets

Fig.10. Metallic pellets tested in compression

For both variants of hardening process wasperformed after five diagrams of hardening, varyingthe heating time and for each version wasdetermined resistance of the pellets depending ontheir diameter.Variant 1: - temperature set for the first attempt is1220C, heating time is 5 hours and the maintenanceis 30 minutes.Heating speed in this case is 244 C/h.

In fig. 11 is shown the diagram heating afterwhich made these strength pellets and in fig. 12 isrestored the compressive resistance variationdepending on the diameter of pellets.

Fig.11. Diagram of hardening of the pellets

Fig.12. Resistance variation depending on

diameter

Variant 2: - temperature set for the first attempt is1220C, heating time is 4 hours and the maintenanceis 30 minutes. Heating speed in this case is 305C/h. In fig. 13 is shown the diagram heating afterwhich made these strength pellets and in fig. 14 isrestored the compressive resistance variation

depending on the diameter of pellets.


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diameter

Variant 3: - temperature set for the first attempt is1220C, heating time is 3 hours and the maintenanceis 30 minutes.

Heating speed in this case is 406 C/h. Infig. 15 is shown the diagram heating after whichmade these strength pellets and in fig. 16 is restoredthe compressive resistance variation depending onthe diameter of pellets.



diameter

Variant 4: - temperature set for the first attempt is

1220C, heating time is 2 hours and the maintenanceis 30 minutes.Heating speed in this case is 610 C/h. In

fig. 17 is shown the diagram heating after whichmade these strength pellets and in fig. 18 is restoredthe compressive resistance variation depending onthe diameter of pellets.



diameter


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Variant 5: - temperature set for the first attempt is1220C, heating time is 1, 5 hours and themaintenance is 20 minutes.Heating speed in this case is 813 C/h.

In fig. 19 is shown the diagram heating afterwhich made these strength pellets and in fig. 20 isrestored the compressive resistance variationdepending on the diameter of pellets.


Fig.20. Resistance variation depending ondiameter

4 ConclusionThe three types of ferrous powder waste: steelworksdust, dust furnace, red mud are appropriate in termsof granulation processes through pelleting.

Content of carbon (C) from the furnace dustand ashes used as bonding agent with bentonite, hasled to a reduction of oxides of Fe. During thestrength of pellets, the alumina from red mud withbentonite and ashes of the thermo power-station

fulfilled the role of a binder.

The mixture of waste subjected to pelletingprocess behaved well.Concerning the diagrams of pellet was found thatthe best results are obtained when heating,respective the maintenance of the landing, is madebetween 1215-1225 C and for maintaining about 30minutes.

Working on such a diagram, besides thestrength process takes place a reduction in all massof pellets resulting metalized pellets.

Metalized pellets have a similar structure ofsponge iron (fig. 10), pellets tested in compression.Warming pellets up to 1200 C regardless of timeof maintenance in landing does not derive thecorresponding resistance to compression resultsbeing unsatisfying. A heating temperature more than1240 C-1250 C has led to slag pellets. On the

basis of submitted I think the optimal chart ofstrength is presented in fig. 20.Research carried out shows that the waste

can be processed together which from the point ofecological view lead to several storage areasoccupied (dumps, ponds) natural flow.

AcknowledgementsThis work was partially supported by the strategicgrant POSDRU 107/1.5/S/77265,inside POSDRU Romania 2007-2013 co-financed

by the European Social Fund Investing in People.

References:[1] Heput T., Ardelean E., Constantin N Socalici

A., Ardelean M., Buzduga R., Recovery ofsmall and powder ferrous waste, EditurePolitehnica, Timisoara,2011, pp 7-11.

[2] E. Ardelean, M. Ardelean, T. Heput, Researchconcerning the obtaining from industrial wastesof a cover powder used in steel continuouscasting,Advanced Materials Research, vol.23:Materials and Technologies, 2007, pp.329-332.

[3] A. Socalici, T. Heput, E. Ardelean, M.Ardelean, Research regarding using the wastewith carbon content in siderurgical industry,Journal of Environmental Protection endEcology,book 2, 2010, pp. 465-470.

[4] Project no. 31-098/2007: Prevention andfighting pollution in the steel making, energeticand mining industrial areas through therecycling of small-size and powdering wastes,Program PN2 Consortium CO.

Responsible: Prof. dr. eng. Teodor Hepu.


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[5] Socalici, A., Heput, T., Ardelean, E., Ardelean,M., Researches regarding the obtaining ofactive slag by using reactive admixtures

produced from ferrous and basic scrap, The 6thWSEAS International Conference on Energy,

Environment, Ecosystem and SustainableDevelopment, Timisoara, 2010, pp.158- 163

[6] Capatana C., Racoceanu C., Wastes, EditureMatrix Rom Bucuresti, 2003, pp 40.

[7] Socalici A., Heput T., Ardelean E., ArdeleanM.,Researches Regarding the Obtaining ofActive Slag by Using Reactive Admixtures

Produced from Ferrous and Basic Scrap,6thWSEAS International Conference onENERGY,ENVIRONMENT, ECOSYSTEMSand SUSTAINABLE DEVELOPMENT(EEESD '10) - Politehnica University of

Timisoara, Romania October 21-23, 2010, pp158 163.


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