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Mineral and chemical composition of metallurgical slags

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1 Mineral and chemical composition of metallurgical slags
Iwona JONCZY, PhD Eng. Silesian University of Technology Faculty of Mining and Geology Institute of Applied Geology Gliwice, Poland Mineral and chemical composition of metallurgical slags Oulu,

2 Upper Silesia is one of the best developed regions in Poland.
Rich deposits of metal ores and hard coal have contributed to the extensive development of metallurgy and coal mine industry which started as early as in the Middle Ages.

3 The extensive mining and metallurgical activity carried out over years has brought about changes of the environment. Metallurgy became especially problematic, mainly because of considerable amounts of wastes coming into being during production.

4 For many years metallurgical slags were collected on the dumps.

5 There are propositions:
to apply slag for the production of road aggregate, aggregate for the production of concrete mixtures, as raw material for the production of mineral wool, to return slags to metallurgical processes, to liquidate waste dumps to reclaim the land used for the dumps and to effect their subsequent revitalization.

6 That is why it is important to carry out research on their mineral and chemical composition, which may deliver some information during an economic exploitation of slags, e.g.: connected with new phases forming in metallurgical processes, forms of metal occurrence in slag components, possibilities of metals release from slag components and their migration to the environment.

7 Each type of the slag should be taken individually, we can not make too many generalizations of mineral and chemical composition of the slag. Due to the phase composition, metallurgical slags are one of the most diverse groups of waste materials. Phases, which crystallized in a furnace can be identified with the minerals forming as a result of geological processes. However, their chemical compositions usually are much richer than their natural counterparts.



10 Research methods Chemical analysis Electron probe microanalysis
Microscopic analysis in transmitted and reflected light Scanning microscopy X-ray analysis

Concentration of the elements [Mass%] Al As Ca Fe K Mg 1,99-3,74 2,49 0,20-1,70 0,70 1,83-7,75 6,32 13,40-20,60 16,94 0,22-0,55 0,40 0,73-1,48 1,16 Mn P Pb S Ti Zn 0,05-0,20 0,10 0,03-0,10 0,09 0,50-2,90 1,55 0,98-7,06 5,49 0,14-0,33 0,21 0,62-8,4 3,14 Ranges and mean values are shown for 20 samples of the wastes

Concentration of the elements [ppm] Ag Ba Bi Cd Co Cr Cs Cu Ge 113 480 0,2 84 19 53 9 506 2 Hf In Ir Mo Ni Rb Sb Sc Se 40 3 10 110 39 7 20 Sn Sr Ta Te Th Tl U W V 250 1 0,1 5 58 La Ce Eu Lu Nd Sm Tb Yb Au [ppb] 24 38 0,5 0,9 47 Mean values are shown for 20 samples of the wastes

As [ppm] Ba [ppm] Ca [% ] Cd [ppm] Ce [ppm] Co [ppm] 0,86-10,00 0,1-30,2 0,08-32,70 0,1-7,9 6,1-152,0 0,8-89,6 Cr [ppm] Cu [ppm] Fe [%] K [%] La [ppm] Li [ppm] Mg [% ] 19,1-626,0 0,39-11,30 0,03-2,16 3,1-69,4 6,6-154,0 0,05-4,85 Mn [ppm] Mo [ppm] Na [% ] Ni [ppm] P [%] Pb [ppm] S [%] 0,5-21,9 0,04-0,70 6-278 0,007-0,756 1,5-634,0 0,06-0,23 Sb [ppm] Sn [ppm] Sr [ppm] Ti [%] W [ppm] V [ppm] Zn [ppm] 0,1-19,6 1-104 0,024-0,585 0,6-200,0 1-1000 6, ,0

14 Mineral composition of metallurgical slag
Components formed during the metallurgical processes: glaze, metallic aggregates, oxides and silicates. Secondary phases, which are connected with the crystallization on the dump: calcite, gypsum.

15 Akermanite Ca2Mg[Si2O7] Alite Ca3[O|SiO4] Anorthite Ca[Al2Si2O8] Augite (Ca,Mg,Fe2+,Fe3+,Ti,Al)2[(Si,Al)2O6] Bredigite γ-Ca2[SiO4] Brownmillerite Ca2(Al,Fe)2O5 Calcioolivine α-Ca2[SiO4] Cristobalite SiO2 Diopside CaMg[Si2O6 ] Fajalite Fe2[SiO4] Ferrites CaO-FeO-Fe2O3 Forsterite Mg2[SiO4] Gehlenite Ca2Al[(Si,Al)2O7] Gypsum CaSO4·2H2O Goethite FeOOH Hematite α-Fe2O3 Calcite CaCO3 Quartz Larnite β-Ca2[SiO4] Magnetite Fe3O4 Melilite (Ca,Na)2(Al,Mg)[(Si,Al)2O7] Merwinite Ca3Mg[SiO4]2 Monticellite CaMg[SiO4] Periclase MgO Lime CaO Wustite FeO

16 Electron probe microanalysis
It is a kind of spectroscopy methods. That method permits to observe a small area of the sample and shows a qualitative and quantitative composition of a sample. That analysis shows also distribution of the elements.

17 No. [%] Al2O3 SiO2 MgO CaO FeO MnO TiO2 Cr2O3 ZnO V2O5 SO3 P2O5 1 0,03 59,04 1,01 12,22 27,00 - 0,49 0,02 0,10 2 0,06 60,61 0,86 11,40 26,47 0,43 5 0,84 39,81 57,73 0,05 0,16 0,07 1,20 6 0,95 39,95 56,85 0,11 0,12 1,72 7 2,94 53,80 0,23 1,59 40,92 8 48,90 1,35 0,04 41,45 0,14 0,09 0,39 0,15 7,23 9 62,85 1,24 0,08 35,17 0,36 0,27 10 62,03 35,59 0,19 0,13 0,96


19 Drop of iron surrounded by glaze

20 Metallurgical slag is a byproduct of the smelting process, which could be compared to magmatic processes. Under high temperature minerals crystallize in the correct order. The same order is in magma and in the metallurgical alloy. It should be noted, however, that the minerals in the earth were formed over thousands and millions of years, minerals from metallurgical alloy had short time to formed their structure.

21 Process of their crystallization is often interrupted by the rapid cooling of the slag melt. Therefore, the composition of the slag is dominated by small crystals surrounded by glaze. Well formed crystals, which identification by microscopic examination is possible, are present in small amounts. The chemical composition of phase crystallizing from the slag is often richer than the chemical composition of their natural counterparts.

22 Mineral composition of slags
in transmitted and reflected light during microscopic analysis

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