Procedures have been developed to determine the volume, rate and composition (particularly BTEX: benzene, toluene, ethylbenzene and xylenes and PAHs (polycyclic aromatic hydrocarbons)) of gas evolution from moulds and cores prepared with various binders as a means of harmfulness of moulding sands. The rate of gas evolution from green sands with four different lustrous carbon carrier and BTEX content were determined. The gas evolution rates are highest in the range of about 20 to 30 s after contact with molten metal. In practice during the first 200-250 s the total emission of gases generated in investigated samples occurred. The main emitted component from the BTEX group was benzene.Postupci su razvijeni za određivanje volumena, brzine i sastava (posebice BTEX: benzen, toluen, etilbenzen, xilana) i PAH (policiklički automatski hidrokarbonati) plina koji nastaje iz kalupa i jezgri na različitim nosačima u težnji za neškodljivost kalupnih pijesaka. Brzine nastajanja plina iz pripravljenih pijesaka sa 4 različita svijetleća nositelja ugljika i sadržajem BTEX su određeni. Brzine nastajanja plina su najveće u razini 20 do 30 s poslije dodira sa rastopljenim metalom. Praktično, tijekom prvih 200-250 s ostvaruje se ukupna emisija stvorenih plinova u istraživanim uzorcima. Iz BTEX skupine, benzen je glavna emitirajuća komponenta

A. Bobrowski

B. Grabowska

D. Kwaśniewska-Królikowska

M. Holtzer

R. Dańko

S. Żymankowska-Kumon

W. Solarski

English

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437METALURGIJA 51 (2012) 4, 437-440M. HOLTZER, B. GRABOWSKA, S. ŻYMANKOWSKA-KUMON,D. KWAŚNIEWSKA-KRÓLIKOWSKA, R. DAŃKO, W. SOLARSKI, A. BOBROWSKIHARMFULNESS OF MOULDING SANDS WITH BENTONITE AND LUSTROUS CARBON CARRIERS Received – Prispjelo: 2012-02-08Accepted – Prihvaćeno: 2012-04-03Original Scientifi c Paper – Izvorni znanstveni radISSN 0543-5846METABK 51(4) 437-440 (2012)UDC – UDK 621.746:621.742=111M. Holtzer, B. Grabowska, S. Żymankowska-kumon, D. Kwaśniew ska-królikowska, R. Dańko, W. Solarski, A. Bobrowski, AGH University of Science and Technology, Faculty of Foundry Engineering, Kraków, PolandProcedures have been developed to determine the volume, rate and composition (particularly BTEX: benzene, tolu-ene, ethylbenzene and xylenes and PAHs (polycyclic aromatic hydrocarbons)) of gas evolution from moulds and cores prepared with various binders as a means of harmfulness of moulding sands. The rate of gas evolution from green sands with four diff erent lustrous carbon carrier and BTEX content were determined. The gas evolution rates are highest in the range of about 20 to 30 s after contact with molten metal. In practice during the fi rst 200-250 s the total emission of gases generated in investigated samples occurred. The main emitted component from the BTEX group was benzene.Key words: moulding sand, castings, bentonite, foundry.Neškodljivost kalupnih pjesaka sa bentonitom i svijetlećim nositeljima ugljika. Postupci su razvijeni za određivanje volumena, brzine i sastava (posebice BTEX: benzen, toluen, etilbenzen, xilana) i PAH (policiklički auto-matski hidrokarbonati) plina koji nastaje iz kalupa i jezgri na različitim nosačima u težnji za neškodljivost kalupnih pijesaka. Brzine nastajanja plina iz pripravljenih pijesaka sa 4 različita svijetleća nositelja ugljika i  sadržajem BTEX su određeni. Brzine nastajanja plina su najveće u razini 20 do 30 s poslije dodira sa rastopljenim metalom. Praktično, tijekom prvih 200-250 s ostvaruje se ukupna emisija stvorenih plinova u istraživanim uzorcima. Iz  BTEX skupine, benzen je glavna emitirajuća komponenta.Ključne riječi: kalupni pijesak, odljevci, bentonit, ljevarstvoINTRODUCTIONThe assessment of harmfulness of moulding sands applied for casting moulds and cores concerns two ba-sic problems:•  emission of harmful gases during the sands prepa-ration, moulding, pouring, cooling and shakeout of moulds;•  leaching of dangerous substances into the environ-ment from spent foundry sands e.g. during their storage or waste management.Therefore, when assessing the infl uence of the given sand on the environment, these two problems should be taken into account. Only such investigations can pro-vide the total assessment of the moulding sand harmful-ness [1-5].It is expected that the development of binding agents appliedfor moulding and core sands will be more of the evolutional than revolutionary character. Changes will be mainly caused by more and more demanding require-ments within the environment protection domain. Sources of the emission of dangerous substances into the air in the casting production process constitute the typical casting operations (e.g. preparation of mould-ing and core sands, melting of liquid metal, pouring, cooling and shakeout of moulds), as well as the auxil-iary processes (e.g. mechanical treatment, fettling and painting of castings) (Figure 1).In the case of moulding sands with bentonite and ad-ditions of lustrous carbon carriers the main sources of dangerous substances emissions are operations of: pour-ing, cooling, shakeout of moulds and cores making. The emission from these processes constitutes 90 % of the total emission of dangerous compounds (Figure 2).Figure 1  Sources of ferrous foundry HAP (Hazardous Air Pollutants) emission [6]438  METALURGIJA 51 (2012) 4, 437-440M. HOLTZER et al.: HARMFULNESS OF MOULDING SANDS WITH BENTONITE AND LUSTROUS CARBON CARRIERSMOULDING SANDS WITH BENTONITEMoulding sands with bentonite, applied for the pro-duction of moulds for steel or aluminium alloys cast-ings are considered to be ecologic1∗ and not emitting organic compounds. However, after introducing coal dusts, synthetic resins or other lustrous carbon carriers into such sands (which is necessary to obtain the ade-quate surface quality of iron castings, to decrease cast-ing defects and facilitate casting shakeout), they become very harmful for the natural environment as well as they cause harmful working conditions. As the result of a liq-uid metal high temperature infl uence on a moulding sand the compounds containing carbon undergo incom-plete burning or a cracking process, which causes emis-sion of dangerous substances (PAHs). Wastes of spent moulding sands from this technology also contain some of these substances, which can render diffi cult their storing or reusing. Approximately 70-80 % of iron castings are currently produced in moulding sands with bentonite [8] and prob-ably this tendency will be maintained in the world during the next years. Therefore the world companies, produc-ing mixtures for the foundry industry, as well as the re-search institutions are performing intensive investiga-tions attempting to develop coal-containing additions, which could substitute traditional coal dusts. Such com-panies as: S&B Industrial Minerale (Germany), Süd-Chemie (Germany), ZGM Zębiec S.A. (Poland), should be mentioned. It is also possible to apply the technology of oxidising harmful substances, the so-called Advanced Oxidation Process [9-10], or to introduce into moulding sands additional substances neutralizing, to a signifi cant degree, the harmful compounds [6]. * Sands with bentonite, without coal dust additions, are not always with-out organic compounds. Using core sands with organic binders causes that organic compounds evolving due to high temperatures can concen-trate in these sands.EXPERIMENTAL PROCEDUREInvestigations of the gases emission were performed according to the original method developed in the Fac-ulty of Foundry Engineering, AGH UST [4, 11]. The schematic presentation of the experimental stand is given in Figure 3. A sample of the investigated moulding sand of a roll shape of dimensions Φ 50 x 50 mm, compacted by a moulder’s rammer stroke, is poured with liquid cast iron of a temperature of 1 400 oC. Gases emitting from the sample - after pouring it with liquid metal - are led by means of a steel pipe via the drying system and the cap-sule with active carbon into a tightly sealed container with liquid, from which they push out the liquid. The weight of displaced liquid was measured as a function of time. Gases from the BTEX group (benzene, toluene, ethylbenzene and xylenes) are adsorbed on active car-bon. The tested sample was heated rapidly to a tempera-ture of 1 400 oC at the surface and then relatively slow inside, to a temperature of 900 oC. In such a system all tested samples are passing through a temperature range: 400-900 oC, in which the majority of volatile substances is emitted. The whole mould is made of green sand. The active carbon layer with adsorbed organic substances is extracted in carbon disulphide. The analysis is carried out by the gas chromatography method with the application of the fl ame-ionising detector (FID).The gases emission measurements were performed for four green sands with different lustrous carbon car-rier originated from 4 various producers from the EU countries. The total gas emission, kinetics of this emis-sion and the content of the BTEX compounds in the emitted gases were estimated. RESULTS AND DISCUSSIONSThe obtained results are presented in Table 1. The emissivity of gases from green sands and the BTEX content, is presented in Figure 4 a, b, c; 5. The results obtained for the moulding sand with the ENVIBOND binder, developed by the S&B Industrial Minerals Ger-many, where additions of microcrystalline graphite and natural zeolite were applied, are added for comparison [12]. The kinetics of the emission of gases from the tested moulding sands, expressed for 1 g of the sand, is presented in Figure 6. Melting Metallics3 %Pouring, Coolingand ShakeoutMetallics 1 %Core/Mold MakingOrganics 2 %Melting Organics4 %Pouring, Coolingand Shakeout 90 %Figure 2  The pouring, cooling and shakeout operations contribute the most emissions in a green sand casting facility [7]Figure 3  Scheme of stand of measurement of gas volume and BTEX emission 439METALURGIJA 51 (2012) 4, 437-440M. HOLTZER et al.: HARMFULNESS OF MOULDING SANDS WITH BENTONITE AND LUSTROUS CARBON CARRIERSTable 1 Gases emission from moulding sand No. Gasesvolume/ dm3/kgmouldingsandGases emission/ mg/kg moulding sandMaximum velocityof emission,dV/dt/ cm3/g·sB T E X1 19,5321,37average20,45254,69231,69243,199,577,098,330,060,070,0650,390,320,350,1642 19,11 386,73 9,76 0,13 1,19 0,1563 24,73 166,64 3,02 0,05 0,29 0,2364 22,19 370,85 15,52 0,06 0,47 0,1755 20,92 128,65 15,43 0,52 3,40 0,5*B – Benzene, T – Toluene, E – Ethylbenzene, X – Xylene*  In this case a little diff erent way of leading gases from the sample was applied, which could infl uence the process kinetics (higher resistances during fl ow), but should not infl uence the total amount of gases emitted neither their composition.The losses on ignition (LOI) and volatile parts (VP) contents are certain indicators of the organic additions content in moulding sands with bentonite. The smaller LOI and VP in sands, the smaller is also the emission of gases during the processes of pouring, cooling and shakeout of moulds [7]. CONCLUSIONS The performed investigations of gases emissivity from moulding sands with bentonite, containing various additions of lustrous carbon carriers and different kinds of bentonite, indicated that the volumes of emitted gases are within the range: from 19,1 dm3 to 24,7 dm3 ex-pressed for 1 kg of the moulding sand. As expected, the main emitted component from the BTEX group was benzene. However, within the investigated moulding sands there are signifi cant differences in the benzene content in emitted gases; e.g. sand No. 2 emits two times more benzene than sand No. 3, in spite of the fact that the volume of the gases emitted from sand No. 2 is 25 % smaller than from sand No. 3. Thus, from the point of view of the casting quality, sand No. 2 is better since it emits less gases and the velocity of their emission is much lower; for sand No. 2 v = 0,156 cm3/g·s, while for sand No. 3 the maximum velocity v = 0,236 cm3/g·s. However on account of the environment hazard, due to the carcinogenic benzene emission, moulding sand No. 2 is more dangerous. Therefore LOI and VP content can Benzene01002003004001 2 3 4 5Number of sampleGasemission/mg/kgmouldingsandToluene04812161 2 3 4 5Number of sampleGasemission/mg/kgmouldingsandEtylbenzene + Xylene00,511,522,533,51 2 3 4 5Number of sampleGasemission/mg/kgmouldingsandEtyobenzeneXylenea)b)c)Figure 4  The content of BTEX in gases emitted from moulding sands05101520250 100 200 300 400 500 600 700 800 900Time / sGasesvolume/cm3 /gSample 1Sample 2Sample 3Sample 4Figure 5 Gases volume emitted from moulding sands00,060,120,180,240 100 200 300Time / sVelocityofgasesemission/cm3 /gsSample 1Sample 2Sample 3Sample 4Figure 6 Kinetics of gases emission from moulding sands440  METALURGIJA 51 (2012) 4, 437-440M. HOLTZER et al.: HARMFULNESS OF MOULDING SANDS WITH BENTONITE AND LUSTROUS CARBON CARRIERSbe only indicators of the volume of the gases emitted from the given sand, but these indicators are not provid-ing any information concerning the chemical composi-tion of gases. In practice, during the fi rst 200-250 s the total emis-sion of gases generated in investigated samples oc-curred, and later on the emission level was quite mini-mal. The gas evolution rates are highest in the range of about 20 to 30 s after contact with molten metal.The developed method of measuring the gases emis-sion from moulding sands is characterized by a high repeatability of results, and the applied system of sam-pling (gas drying system, fi lters for catching dusts, etc.) warrants the correctness of the performed measure-ments. However, one should be aware, that the mould-ing sand is a mixture of a high degree of heterogeneity and therefore local differences in the composition can occur, which can infl uence the obtained results. Conditions created during experiments can be con-sidered extreme, in respect to the investigated moulding sand, very close to the ones to which the core in the mould is subjected, however much more drastic than in the case of the mould. Thus, it can be assumed that the measured emission values are maximum values, which can occur under the real conditions in the foundry. The study was performed within the Project No. 07-0016-10/2010 from NCBiR.REFERENCES1. P. Johansson, Alternative materials for civil engineering foundations and road construction, Foundry Trade Journal 6 (2004), 180-181.2. J. Orkas, Benefi cial Re-use of foundry surplus sands in the composting process, Fonderie Fondeur d’aujourd’hui 215 (2002), 34-40.3. P. Nayström, J. Lemkow, J. Orkas, Waste foundry sand - a resource in composting and soil production, Foundry Tra-de Journal 6 (2004), 188-189.4. M. Holtzer, R. Dańko, Theory and practice in reclamation and management of used moulding and core sands (Mono-graph), Komisja Odlewnictwa PAN. Ed. J. Szajnara, Ka-towice-Gliwice (2009), 133-152.5. J. Dańko, M. Holtzer, Methods of limitation of waste from foundry processes and methods of their management. WN “AKAPIT”, Kraków, 2010.6. G.R. Crandell, J.F. Schifo, G. Mosher, AFS Transactions 6-31 (2006), 1-17.7. V.S. LaFay, S. Neltner, D. Carroll, D. J. Couture, Modern Casting 10 (2010), 27-29.8. V.S. LaFay, S.L. Neltner, C. Grefhorst, AFS Transactions 117 (2009), 807-823.9. A. Baliński, Transactions of the Foundry Research Institu-te 3 (2010), 1-5.10. C.R. Głowacki, G.R. Crandell, F.S. Cannon, R.C. Voigt, AFS Transactions 111 (2003), 579-598.11. W. Solarski, J. Zawada, J.L. Lewandowski, Przegląd Od-lewnictwa 47 (1997) 7-8, 234-239. 12. C. Grefhorst, W. Senden, R. Ilman, O. Podobed, V. Latoya, W. Tilch, Proceedings, 69th World Foundry Congress, Hang-zhou China, 2010, Part II Technical Session, 703-709. Note:  The responsible translator for English language: “ANGOS” Translation Offi ce, Kraków, Poland 

Neškodljivost kalupnih pjesaka sa bentonitom i svijetlećim nositeljima ugljika

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Neškodljivost kalupnih pjesaka sa bentonitom i svijetlećim nositeljima ugljika

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