外文翻译---更有效益地使用不锈钢电弧炉炼钢渣作为水泥原料及其重金属掺入量的风险分析

Baosteel Technical ResearchVolume 3, number 4, December 2009 , page 14Beneficial use of stainless steel EAF slag as composite cement admixture and its heavy metals leaching risk analysisWANG Ruyi , CHEN Ronghuan and SHI LeiEnvironment & Resources Division, Research Institute, Baoshan Iron & Steel Co., Ltd., Shanghai 201900, ChinaAbstract: This study analyzes the feasibility of using stainless steel electric arcfurnace ( EAF ) slag as composite cement admixture and the risk of leaching-out of heavy metals. The results show that the stain less steel EAF slag, mainly made up of Ca2SiO4, Ca3Mg(SiO4)2, some Cr-containing minerals and in small particle size, is easily ground and has cementitious activity. EAF slag, w hen used as cement admixture, can be added with a maximum percentage of 32%. It can meet the strength requirements of the standard P·C 32.5 cement When the mixingpercentage is decreased to 25%, the strength o f the cement can be increased to that of P·C 42.5 cement Other main quality indexes of composite cement such as the setting time and stability, also satisfy standard requirements. The results also show that most o f the heavy metals in the stainless steel EAF slag exist in a stable speciation. The concentration of heavy metals that leach out from the stainless steel EAF slag and the composite cement products is far lower than the standard limit of hazardous wastes. The m a in heavy metal chromium, exists as less hazardous trivalent chromium. Therefore, the risk of heavy metals leaching out from the stain less steel EAF slag is low. The internal expo sure index (IR) and the external exposure index (Iγ) of the stainless steel EAF slag are both lower than 1. 0, satisfying the standard requirements of the state for the radionuclides of building materials. Therefore,stainless steel EAF slag can be safely used as admixture to produce composite cement Key words: stainless steel EAF slag; composite cement admixture; heavy metal; risk of leaching out1 IntroductionThe annual stain less steel slag output has topped 3 Mt in China, and how to effectively process the slag has become an emerging issue. The chemical and mineral compositions of stain less steel slag are similar to those of Portland cement and blast furnace (BF) slag, which are conventionally used as the raw material for cement Therefore, it is believed that stain less steel slag can be used as a raw material for cement Since stainless steel slag contains chromium oxide and other heavy metals, its effect on the environment should be clarified when it is used as a resource. In this study, stainless steel electric arc furnace (EAF) slag, with the biggest output and highest chromium content in stainless steel slag, was the main focus of research. By testing the chemical and mineral compositions, the radioactivity, the cementitious activity, the heavy metal leaching toxicology and the performance of the composite cement the feasibility of the use of stain less steel EAF slag as composite cement admixture and the risk o f heavy metals leaching out were analyzed, in order to provide grounds for using stainless steel slag as a safe resource.2 Material and methodsThe stain less steel EAF slag w as sampled from the Baosteel Stainless Steel Business Unit It was the tailings of molten stainless slag from an EAF after water immersion, cooling, crashing, grinding, and gravity and magnetic separation. The chemical and mineral compositions of the stainless steel EAF slag were determined using an X-ray fluorescence spectrometer ( referred to as XRF, Model SRS 3400, produced by BRUKER AXS GMBH, Germany) and an X-ray diffractometer( referred to as XRD , Model D /max 2550X, produced by Rigaku Co.,Japan) . The contents of Cd , Cr, Cu, Ni Ba , Pb , and Zn in the slag sample were analyzed by ICP-OES ( Optima 2100DV, produced by Perk in Elmer Inc., USA ) , while the contents of As and Hg were analyzed by AFS ( XGY1012, produced by the Institute of Geophysical and Geochemical Exploration, the Chinese Academy of Geological Sciences, China ), after aquaregia digestion. The concentration of Cr (VI) in the leachate was determined by Dipehenylcarbohydrazide Spectrophoto-metry .The leaching toxicity of the slag samples was determined according to the Test method standard for leaching toxicity of solid wastes. the horizontal vibration extraction procedure(GB 5086. 2--1997) and theToxicity Characteristics Leaching Procedure ( referred to as TCLP, USA ). The speciation of heavy metals in the slag samples was analyzed by the sequential extraction procedure according to the Tessier A and Wan X method. Internal andexternal exposure indexes were determined accord ing to the state standard, the Limit of radionuclides in building materials ( GB 6566- 2001).The cementitious activity test of the EAF slag was determined according to the Test method for the activity of industrial waste slag used as cement mixing materials (GB 12957). The compressive and bending strength of the cement were determined according to the Test method for cement mortar strength (ISO) (GB/T 17671-1999). The consistency, setting time and soundness of the cement were determined according to the Test methods for the water consumption, setting time and the stability of the normal consistency of Portland cements (GB/T 1346-2001).3 Results and discussion3. 1 The physical and chemical properties of the stainless steel EAF slagTable 1 shows the chemical composition of the stainless steel EAF slag. The slag is mainly made up of CaO, SiO2, Al2O3, MgO, and contains less Fe, more SiO2, a higher concentration of Cr2O3 and some NiO when compared with conventional carbon steel slag. The mineralogical result (Fig.1) indicates that stainless EAF slag contains silicates, i. e., Ca2SiO4, Ca3Mg(SiO4)2, and Cr containing minerals. The chemical and mineral properties o f EAF slag are similar to those of cement suggesting that stainless steel slag can be used as a raw material of cement3.2 The heavy metal content in stainless steel EAF slag and the leaching toxicity of the slagThe heavy metal content in stainless steel EAF slag are shown in Table 4.Cr and Ni were the major components of the slag heavy metal content while there was a small amount of Ba, Cu, Zn and Pb. No Cd, As and Hg was detected.Steel slag may come in contact with rain water or leachate when it is used or processed. The dissoluble matters, such as metal ions and salts, m ay leach from the slag and migrate with the leachate, thus polluting the surrounding water body or soil.The leaching toxicity o f the slag can be evaluated by the standard leaching test Table 5 lists the leaching concentrations of heavy metals by China standard leaching test( GB 5086. 2-1997) and the American standard (TCLP) .Compared with the corresponding limit values for the identification of hazardous waste, the leaching concentrations of heavy metals from stainless steel EAF slag are significantly lower (C r, Ni, Ba, Cu, Pb and Zn) or even undetectable (As, Cd, Hg and Cr).Though the content of Cr and Ni in EAF slag are relatively high( Tab le 4) , its leaching toxicity is low.The speciation distribution of five main heavy metal elements (Cr, Ni ,Ba, Zn and Cu) in EAF slag is shown in Fig. 3. It was observed that the majority of the heavy metals exist as residua ,organic matter-bound and iron /manganese oxide-bound fractions, which are relatively stable and hardly leach from slag. Only a small fraction is watersoluble or carbonate-bound, which may be leached out from slag by water when it is used o r processed. The result also explains the low leaching toxicity o f heavy metals.3.3 The feasibility of using stainless steel EAF slag as composite cement admixtureThe precondition o f using stain less steel EAF slag as cement raw material is that it must have certain cementitious activity ( Fig. 3). The compressive strength of Portland cemen t ( P•I52. 5 ) and the composite cement made up of 30% EAF slag and 70% cement are shown in Table 6. The compressive strength ratio of the two types of cement cured for 28 d is 62. 3%,which satisfies the standard requirements o f the state Pozzolanic materials used as cement admixture(GB /T 2847-1996). It indicates that EAF slag has a certain cementitious activity and can be used as cement admixture. 3.4 The leaching toxicity of composite cement mixed with stainless steel EAF slagCompared with the corresponding limit values for the identification of hazardous waste,the concentrations of heavy metals leached from the two types of the leachate decreased except for Cr. Compared with the leaching results o f raw EAF steel slag, the Cr concentration increase might be the result of the change of the compo site cement size and pH value. Though the concentration of Cr was relatively higher compared with other heavy metals, Cr was not detected in the leachate, so it would bring about little toxic risk .4 Conclusions(1) Stain less steel EAF slag, mainly made up of Ca2SiO4, Ca3Mg(SiO4)2 and some Cr-containing minerals, has a small particle size, is easily ground and has cementitious activity. Both its internal exposure index (IR) and external exposure index (Iγ) meet the standard requirements of the state for the limit of radionuclide in building materials. Therefore, stainless steel EAF slag can be used as composite cement admixture. The composite cement mixed with stainless Steel EAF slag using the max .percentage of 32%, can meet the quality requirements of P•C 32. 5, cement of the lowest strength class.(2) Cr and Ni which are the major heavy metals in stainless steel slag, normally exist in stab le chemical state. The leaching concentration o fall heavy metals of stainless steel EAF slag and its composite cement are far less than the corresponding limits of the identification standard for hazardous wastes. Stainless steel EAF slag can be safely used as admixture to produce composite cement mixed with cement clinkerReferences[1] State Environmental Protection Administration of China. Monitoring and analyzing methods of water and waste water (4th edition)[M]. Beijing : China Environmental Science Press, 2002: 346-349.[2] State Environmental Protection Administration. GB5086. 2- 1997 Test method standard for leaching toxicity of solid wastes horizontal vibration extraction procedure[S]. Beijing: State Environmental Protection Administration, 1997.[3] US Environmental Protection Agency. SW - 846 –Method 1311 Toxicity characteristic leaching procedure[S]. Washing ton DC: US Environmental Protection Agency,1992.[4] Wan X, Wang W, Ye T M, et a l. A study on the chemical and mineralogical characterization of MSWI fly ash using a sequential extraction procedure [J].J Hazard Mater I, 2006, 134(1/3): 197-201.[5] Tessier A, Campbell PGC and Bisson M. Sequential chemical extraction procedure for the speciation of particulate trace metals [J] .Anal Chem, 1979,51( 7 ):844-850.[6] State General Administration o f Quality Supervision, Inspection and Quarantine. GB 6566-2001 limit of radionuclide in building materials[ S] . 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GB5086.3-1996 Identification standard for hazardous wastes-Identification for extraction proceduretoxicity[S].Beijing: China Environmental Science Press, 1996: 1-3.宝钢技术研究第四期，卷3,2009年12月第14页更有效益地使用不锈钢电弧炉炼钢渣作为水泥原料及其重金属掺入量的风险分析王如意，陈荣华，石磊环境和资源划分、研究所、宝山钢铁有限公司、中国上海201900 文摘：本研究讨论和分析采用不锈钢电弧炉熔渣作为水泥原料的可行性，并分析其重金属的掺入的风险和指标。