2009 March 12. Recycling of steel wires from End of Life Tires IARC 2009

Transcription

1 A new scrap grade for the steel industry Steel wires recycling from End of Life Tires Catherine Clauzade, Benoît HUSSON TISSIER, Philippe RUSSO, Bernard GROS, Aliapur R&D Lyon ArcelorMittal R&D Maizières lès Metz IARC 2009

2 1 Introduction End of Life Tires (ELT): roughly 25million 2.5milliontons per year in U.E. Recycling End of Life Tires is perfectly in agreement with the European Directive 2000/53/EC Tires are made of between 15 and 25% of steel Roughly 180 kt of steel wires,, from grinded recycled Roughly ELT, per year in U.E UE Currently land filled or mixed with other scraps ie i.e. notcorrectly recycled/recovered in steel mills.(see 2 next pictures) 2

3 Bad example of steel wires generated by grinding car tires. Too much rubber is remaining on steel, 15 to 35% in weight 3

4 Bad Bd example of steel t wires generated tdb by grinding truck kti tires. More steel content, compare to car tires, but still too much rubber or other non metallic elements. 4

5 Good example of steel wires generated by grinding truck /car tires. Few non metallic elements. 5

6 1 Introduction (continue) 2007: : ArcelorMittal, Aliapur 1 and Ademe 2 launched a R&D study aiming to create a new scrap grade, from Tires Steel Wires. Main axes of the study : Definition of a sampling method, identification of the parameters explaining the variation in the quality of steel wires. Creation of characterization tests, in order to measure the non metallic content of steel wires. Set up of a compacting mode, in order to easily handle steel wires and to increase its bulk density. To make Industrial trials in some ArcelorMittal s converters and electric arc furnaces. 1) French Company for tires recycling, 2) French Environmental and Energy Agency. 6

7 2 Variation sources of the quality of steel wires Sampling method 7

8 21 Variations due to the origin ii of tires Depending with tires recycling workshop supplying: Trucks tires, car tires or mix Two main differences between car and truck tires : Composition of tires, apart rubber: (next figures) car tires, roughly 15% of steel, plus some textile fibbers, truck tires, roughly 25% of steel, no textile fibbers. Morphology of steel wires: (next pictures) Wires from truck tires are longer and thicker than the ones into car tires. Pieces of rubber, remaining pasted on wires from truck tires, after grinding, are usually bigger. 8

9 Content of tires (Weight %) Materials tires content Car tires (%) Truck tires (%) Rubber Steel wires 15* 25 Textile Total * Including non metallic elements remaining after grinding Main chimical elements into car and truck tires Car tires Truck tires Carbon (C) 68 to 70 % 59 to 66 % Iron (Fe) 11 to 12 % 20 to 27 % Hydrogen (H) 6 to 6,3 63 % 53 5,3 to 6 % Oxygen (O) 3.3 to 3.8 % 1.5 to 2.2 % Silicon (Si) 1.5 to 1.9 % 0.3 to 0.8 % Zinc (Zn) 1.3 to 1.5 % 0.9 to 1.8 % Sulphur (S) 1 to 1.5 % 1.1 to 1.6 % 9

10 Morphology of steel wires steel wires generated by grinding car tires steel wires generated by grinding truck tires Recycling of steel wires from End of Life Tires 10

11 22 Variations due to the grinding processes 2 grinding processes are commonly used to produce rubber powders from granulates. Rotary shears: Successive rotary shears, generate rubber granulates smaller and smaller. Magnetic drums extract steel wires, at each step of the process, then they are gathered and stored together Grinding presses: One or several per grinding line. Consists in crushing with hydraulic roller, rubber granulates into fine rubber powder Crushing generates a friction inside rubber granulate and liberate wires from the rubber 11

12 22 Variations due to the grindingprocesses Grinding with rotary shears The wear of grids and shears, with time, may lead to a degradation of the quality of steel wires generated. Life duration of grids is usually 3 weeks, knifes on rotary shear being changed one or two time per month. As there is no concordance between replacement of grids, knifes and the nature of tires grinded, sampling a representative production should be carried out every day during approximately two months and thus being quite heavy. It shows that the steelmaker, as final consumer, will have to control visually the totality of steel wires deliveries, to validate their homogeneity. 12

13 Rotary shear 13

14 Example of steel wires generated by rotary shears Some grinding workshops are equipped with a specific grinder, which is out of the process, and which is specifically used to clean steel wires fractions extracted at each step of fthe process Such a specific grinder is useful to recover more rubber, lost with the wire fraction, but also generates steel wires with a better steel purity, making the valorisation of wires easier and more profitable. 14

15 22 Variations due to the grindingprocesses Grinding with grinding presses This process seems better for generating really pure products: rubber powder without steel wires, and steel wires with really a few rubber residues content. The investment cost is higher than the previous process. But grinding presses generate savings for the workshop kh as no knifes or grids have to be replaced, which is quite expensive. Furthermore, one grinding press can do the same work as three or four rotary shears. 15

16 Description of a grinding press Example of steel wires generated by grinding presses 16

17 3 Determination of the non metallic content remaining on steel wires rubber textile fibbers 17

18 3 Determination of the non metallic content A necessary conditionbefore envisaging to recycle such products in electric arc furnaces or converters, for steelmaker to be confident. The non metallic elements, remaining on the wires, are rubberand sometimes textile fibbers, Constitute at 80% of carbon, the remaining being sulphur, oxygen, hydrogen and zinc. During this study, several operating modes to determine the nonmetallic content on wires, have been investigated. 18

19 31 Determination of the nonmetallic content Appropriates Operating Modes tested, Air pycnometer: A laboratory equipment, used to determine the true volume of a product, assuming air as a perfect gas (PV = nrt) (next picture) Determination of the true densityof the tire wire sample, compared to steel and rubber densities, gives the amount of rubber remaining on the steel wires. More accurate than the acidic dissolution, as carry out the measurement is 1kg samples (following second picture) Repeatability and reproducibility of this operating mode have been validated. 19

20 Air pycnometer 20

21 Samples of 1kg, prepared for air pycnometer measurement 21

22 32 Determination of the non metallic content Appropriates Operating Modes tested, Pyrolysis: yoyss: A thermal reaction without oxygen, and thus which does not oxidize steel. By heating, at 500 C, 1kg of steel wires for 1h Reproducibility of this operating mode has also been validated. See next pictures... 22

23 Pyrolysis 23

24 Sample 1kg, after pyrolysis 24

25 33 Comparison of results between the 2 metallic content determination operating modes (% by weight) Non metallic content sample n 1 sample n 2 sample n 3 Pycnometry (%) Pyrolysis (%) Pycnometry tends to overvalue (+ 1 to +1.5%) the non metallic content remaining of wires, compared to pyrolysis, but: Pycnometry and pyrolysis are: accurate enough, fast operating modes, So are very convenient, to determine the non metallic content on steel wires. 25

26 4 Industrial trials with steel wires loading Identificationofkindsofsteel of of steel wires available 26

27 41 Steel wires generated by rotary shears They cannot be loaded din a steel lfurnace at that t state tt : 20%, of rubber remaining, generally more. low bulk density, between 0.1 and 0.2 kg/dm 3. Grinding workshops using rotary shears should invest in a dedicated rotary shear in order to purify the steel wires fraction (see next 2 pictures): As an example, the case of a German grinding plant, producing steel wires containing 10% of non metallic materials, with a bulk density of 0.25 kg/dm 3, The investment in a rotary shear, specially dedicated to purify wires generated, made possible to reduce non metallic content at less than 3%, and to increase bulk density up to 0.8 kg/dm 3 27

28 Steel wires generated by rotary shears before additional cleaning after additional cleaning 28

29 42 Loading of steel wires generated by grinding gp presses, in a converter Recycling of steel wires from End of Life Tires 1.29

30 Steel wires generated by grindingpresses Such a product usually has a non metallic content of 2 4% and a low sulphurcontent. It should be interesting for converters. Many trials have been followed during this study, the recommended consumption being 2 3t of steel wires per scrap charge. Chemical content of such wires has been determined by pilot melting Fe C Mn P S Si Al Ni Cr Cu Mo Zn SiO 2 LOI ,85 LOI = Loss of ignition 30

31 Steel wires generated by grinding presses Two advantage for steel wires generated by grinding press: An high iron content (94.9%) compared to steel wires from rotary shears. A low metallic residuals content (Cu, Sn, Cr, Ni, Mo) compared to other scrap grades But because of its morphology, very small size, loading steel wires from grinding gpress into the scrap basket is time consuming (loss of productivity). The solution with bundling: (next 2pictures) So one producer is already delivering bundles: 50 x 25 x 25 cm, 25kg While trials are being done to get smaller bundles: 15.5 x 12.5 x 11cm, 5.3kg 31

32 Compaction of steel wires generated by grinding presses 50 x 25 x 25 cm, 25kg 32

33 Compaction of steel wires generated by grinding presses 15.5 x 12.5 x 11cm, 5.3kg 33

34 5 Conclusions Valorisation of steel wires generated by grinding End of Life tires is possible and viable ibl for steel industry: Variation sources of quality have been identified, making possible to improve setting of devices used to grind tires Operating mode to characterize the quality of steel wires quality have been established Steel makers have now the possibility to control and force theirproviders to respect quality criteria wanted: Commercial agreements have to be established between grinding workshops and purchasers, based on this technical knowledge A market price of steel wires has to be set, depending on scrap market price, which is unfortunately, as for every raw material, much fluctuating. 34

35 5 Conclusions A new scrap grade for the steel industry Definition : Steel wires from grinded End of Life Tires Chemical analysis: High Fe content, Low Cu content Elément % Fe 95 C 3,3 Mn 0,48 Si 0,27 P 0,02 S 0,06 Cu 0,067 Ni 0,067 Cr 0,048 Mo 0,019 Zn 0,06 H 0, O 0,1 35

36 5 Conclusions A new scrap grade for the steel industry Other characteristics: Bulk product: Size 0.5 to 20cm Density d 0.8 Characterization by Pycnometry or Pyrolysis Bundles: Size to be precised after trials. Same analysis as bulk. Cautions against wet: To warehouse under shelter, upon clean floor. Masking for transportation 36

37 Thank you for your attention Recycling of steel wires from End of Life Tires 1.37