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Journal of Chemical Technology and Metallurgy, 55, 3, 2020

Journal of Chemical Technology and Metallurgy, 55, 3, 2020

JournalJournal of Chemical of Chemical Technology and ,and Metallurgy, 55, 3, 55, 2020, 3, 2020 592-597

NEGATIVE EFFECT OF FERROUS METALLURGY NEW ON THE ENVIRONMENT AND POSSIBLE WAYS TO OVERCOME THEM

Oleg Yu. Sheshukov1,2, Michail A. Mikheenkov1, Ilya V. Nekrasov1,2, Denis K. Yeghiazaryan1,2

1 Institute of Metallurgy of the Ural Branch of the Russian Academy of Sciences, Received 31 October 2019 101, Amundsen str., Ekaterinburg, , 620016 Accepted 16 December 2019 2 Federal State Autonomous Educational Institution of Higher Education «Ural Federal University named after the first President of Russia B.N.Yeltsin», 19, Mira str., Yekaterinburg, Russia, 620002 E-mail: [email protected]

ABSTRACT

The negative impact of new technologies of ferrous metallurgy on the environment, con-sisting in the pollution of toxic technogenic formations as the air basin and groundwater. Without additional involvement of -oxide materials for the implementation of the utilization method is the composition, %: oxidizing refining -60; re- ducing refining slags - 20; limestone waste (lime kiln dust) - 20. During the recycling process with this ratio, the yield of products is, %: (clinker) 82, 18. The possibility of reducing the load on the environment due to the utili-zation of technogenic formations of ferrous metallurgy into valuable marketable products is shown. The developed technology has been industrially tested and can be used to reduce the envi-ronmental stress at the ferrous metallurgy enterprises in the integrated waste-free processing of all iron-containing waste. Keywords: ferrous metallurgy, technogenic formations, new technologies, utilization.

INTRODUCTION system adequate to the system of the new electrometal- Over the past 20 years, the has gone lurgical productions which have appeared in recent years through radical changes. In connection with increased consuming scrap as raw materials; requirements for the products quality, while reduc- - lack of a systematic approach to processing and de- ing the raw materials quality, high-intensity steel melting contamination of new electrometallurgical industries wastes. in superpowerelectric arc (EAF) and methods The technology of high-intensity steel melting in of out-of- steel treatment has become widespread. super-power EAF “came” to the Russia mainly from This led to a change in the ferrous metallurgy technogenic . However, domestic standards for scrap formations structure and its qualitative characteristics. preparation are still lagging behind western standards, In the last century, the most common in ferrous which increase the problem of environmental hazards of metallurgy were converter and open- methods of dusts formed on the basis of evaporated scrap containing steel production. By-products (waste) of such production easily sublimable non-ferrous impurities. were slags and dusts, which storage has always caused In connection with the out-of-furnace treatment problems that are now exacerbated, including due to a methods development requirements for the slags combination of the following factors: composition used in the out-of-furnace treatment have - introduction of high-intensity melting processes changed, and, after that slags have also acquired an of metal heating by especially powerful electric arcs; increased environmental hazard. Thus, relative to the - introduction of high-intensity metal oxidation process- old metallurgical processes (open-hearth and converter es by supersonic oxygen jets in modern electric furnaces; ) the modern electric process looks - absence in Russia of the steel scrap preparation “over-intensified”, leading to the waste generation with

592 Oleg Yu. Sheshukov, Michail A. Mikheenkov, Ilya V. Nekrasov, Denis K. Yeghiazaryan

increased danger. The scale of the hazardous waste ac- materials. On the scale of world production (up to 1.5 cumulation problem is such that in some cases it limits billion tons of steel per year), the self-dispersing slag the possibility of further enterprises development due formation is about 30 million tons. to the lack of space that should be occupied by waste The reason for the refining slag self-disintegration of current production [1, 2]. Often slag dumps can be are polymorphic transformations that occur during located in the city limits, disrupting the landscape and cooling of the main slag mineral-bicalcium silicate withdrawing land resources from the circulation. In Rus- (2CaO·SiO2) and are accompanied by a change in the sia, the total area of dumps reaches tens of thousands of crystal lattice volume. Critical changes in the bicalcium hectares, and the metallurgical enterprises payment for silicate crystal lattice occur during the high-temperature these territories occupation can reach several tens of mil- β-modification of bicalcium silicate conversion into lions of rubles per year. In total, up to half billion tons of a low-temperature γ-modification. Due to the density metallurgical slags have been accumulated in dumps on large difference, the conversion of β-2CaO·SiO2 to the territory of the Russian Federation. At the same time, γ-2CaO·SiO2 is accompanied by an increase in volume the growth rate of dumps is from 3 to 5 % per year [1]. of about 12 %, which to the slag powdering. Another problematic technogenic formation of fer- Realized recycling methods and its limitations rous metallurgy, which appeared in connection with the To solve this problem, many metallurgical enter- rapid development of arc melting of steel, is the EAF prises have organized slag processing shops. The shop dust. Like refining slag, the EAF dust has a powder con- extracts metal from slag dumps, which is used in its dition and cannot be processed by traditional methods own production of steel, cast iron and sinter, extracts used in ferrous metallurgy. non-magnetic masses used in road construction and Due to the lack of processing methods, ferrous met- recultivation of open-cast mines and excavations. The allurgy enterprises are forced to store these technogenic economic effect of steelmaking (Converter, EAF) and formations. Slag from “ladle-furnace” units and dust slag processing consists of the following from EAF have a particle size not exceeding 100 µm. components: It was noted by some researchers [3] that about 80 % l metallurgical enterprise income from sale of dumps of powdered slag particles have the grain size less than processing products and its use in own production; 30 µm. Such particles are easily carried by the wind l reduction of land charges due to reduction of areas over long distances, polluting the soil and dissolving in occupied for slag dumps; ground, sediment and wastewater causing significant l reduction of environmental payments due to en- damage to the environment. vironmental stress reduction; Table 1 shows the harmful components content in l reducing the waste operations cost due to the the ludle-furnace unit slag of one of ferrous metallurgy reduction of distances in their warehousing. enterprises, stored on the enterprise territory, and a com- Due to the new technologies development in ferrous parison of this content with the hygienic standards GN metallurgy, such schemes of slag processing become 2.1.7.2041-06 “Maximum permissible concentrations ineffective, since the slag formed during steel out-of- (MPC) of chemicals in the soil.” furnace treatment does not have a stable crystal structure Table 2 shows the harmful components content in and can self-disintegrates to a powder during storage. the EAF dust of one of ferrous metallurgy enterprises, Due to the powder condition, such slags cannot be stored on the enterprise territory, and a comparison of processed by implemented in the industry schemes [1]. this content with hygienic standards GN 2.1.7.2041- The volume of such self-dispersing slag formation is 06 “Maximum permissible concentrations (MPC) of about 2 % of steel production. That is, with steel produc- chemicals in the soil”. tion in the Russian Federation about 70 million tons of According to the given data, the considered techno- steel per year, up to 1.4 million tons of self-dispersing genic formations contain a significant amount of harmful slags are formed. Moreover, since they are practically components that further aggravate the environment dam- not used in other industries, this volume of raw materi- age. Table 3 shows the annual technogenic formations als is lost and replaced by the extraction of natural raw generation at one of ferrous metallurgy enterprises. 593 Journal of Chemical Technology and Metallurgy, 55, 3, 2020

Table 1. The harmful components content in the ludle-furnace unit slag of one of ferrous metallurgy enterprises and the MPC standards for these components. Component Measure unit Result MPC Standards GN Excess of MPC standards 2.1.7.2041-06 1 2 3 4 5 Vanadium mg/kg 130 ± 10 150,0 No excess

Zinc mg/kg 100 ±10 23,0 The excess of 4.3 times

Copper mg/kg 30 ± 10 3,0 The excess of 10 times

Chrome trivalent mg/kg 1300 ± 60 6,0 The excess of 216 times

Table 2. The harmful components content in the EAF dust of one of ferrous metallurgy enterprises and the MPC standards for these components. Component Measure unit Result MPC Standards GN Excess of MPC standards 2.1.7.2041-06

1 2 3 4 5 Vanadium mg/kg 3481 ± 870 150,0 The excess of 23 times

Arsenic mg/kg 193 ± 94 2,0 The excess of 96 times

Nickel mg/kg 138 ± 48 4,0 The excess of 34 times

Lead mg/kg 917 ± 229 32,0 The excess of 28 times

Antimony mg/kg 24,2 ± 12,1 4,5 The excess of 5,4 times

Chrome trivalent mg/kg 1078 ± 216 6,0 The excess of 180 times

Table 3. Annual technogenic formations generation at one of ferrous metallurgy enterprises.

Technogenic formation Waste code Waste Waste generation according to the hazard class per year, tons Federal classification catalogue of wastes Waste of limestone, dolomite and chalk in 23111203404 4 1513,3 powder and dust, low-hazard Non-polluted ferrous metal gas cleaning dust 36123101424 4 10532,9 (EAF dust) Scale from scrap 35121000000 4 6763,2 Refining slags of out-of-furnace steel treatment 35121000000 4 11084,9 (LF slag) Slag of steel production (slag of EAF) 35121000000 4 109208,0 The scale of the rolling production 35150100000 5 11378,9

594 Oleg Yu. Sheshukov, Michail A. Mikheenkov, Ilya V. Nekrasov, Denis K. Yeghiazaryan

Proposed recycling method and recycling calcula- phosphorus from the metal into the slag, while in the tion results conditions of oxidative melting, a significant amount The most problematic technogenic formations in of iron oxides also passes into the slag. RRS ensure the the given list and requiring urgent solutions for disposal removal of sulfur from the metal into the slag due to are gas cleaning dust and refining slag. The issue of the interaction of sulfur with CaO. These technological recycling or transfer of hazardous waste into inactive features of themetallurgical slags formation ensure the forms is especially relevant for them. The disintegration formation of their specific chemical and mineralogical of the hardened slag with the formation of tiny particles compositions [5 - 7]. Table 4 shows the chemical com- leads to a slag particles surface sharp increasing. The position of typical ORS and RRS formed at the ferrous slag particles disintegration from a size of 10 cm to metallurgy enterprises. small particles of about 100 µm leads to a thousand-fold According to the phase analysis data, the following increase in their reaction surface. Therefore, the LF slag phases are recorded in ORS: vustite (FeO), magnetite disintegration leads to a thousand-fold intensification of (Fe3O4), mervinite C3MS2 (3CaO·MgO·2SiO2) and lar- the harmful components transition from the slag particles nite β-C2S (high-temperature modification of bicalcium free surface into the environment. To prevent such con- silicate, β-2CaO·SiO2). RRS have three main phases - tamination, it is necessary to prevent slag disintegration mayenite C12A7 (12CaO·7Al2O3), periclase MgO and by stabilizing its crystal structure. The results of refining shennonite γ-C2S (low-temperature modification of bi- slags stabilization are described in our previous work [4]. calcium silicate γ-2CaO·SiO2). The phases amounts are: Another practical method of such wastes danger re- ducing is the components transfer into a non-hazardous ORS - 20,4 % FeO; 24,1 % Fe3O4; 15,9 % C3MS2; 38,15 form by reducing melting. This method is relevant not % β-C2S; 1,45 % the rest; only for ferrous waste, but also for non-ferrous metallur- gy, where dumps of chromium, vanadium and other slags RRS - 37,2 % C12A7; 12,5 % MgO; 41,4 % γ-C2S; of ferroalloy production are accumulated. Non-ferrous 8.9 % the rest. have a lower affinity for oxygen than iron, so when Such phase and chemical composition of ferrous melting non-ferrous metals are recovered and change into metallurgy slags (significant amount of iron oxides in cast iron, acquiring an environmentally safe state. ORS and significant amount of calcium oxide in RRS) Slags of ferrous metallurgy can be conditionally contributed to the hypothesis and development of the divided into two groups: slags of oxidizing and reduc- method for simultaneous processing of these slags to ing refining. Oxidizing refining slags (ORS) are formed obtain several valuable commodity products [8]. during the conversion of cast iron and steel smelting In accordance with this method, all technogenic in EAF, and reducing refining slags (RRS) are formed formations of ferrous metallurgy, listed in Table 3, can in LF and vacuum units. ORS ensure the removal of be involved in processing with the obtaining of several

Table 4. The chemical composition of typical oxidative and reducing refining slags formed at the ferrous metal- lurgy enterprises.

* ** Slag CaO SiO2 Al2O3 FeO MgO MnO Cr2O3 P2O5 S Мo Кact ORS 15,0- 6,4- 2,5- 19,7- 4,2- 4,3- 1,2- 0,14- 0,05- 1,5- 0,4- 31,1 19,2 8,0 53,2 10,1 8,8 2,4 0,47 0,27 2,15 0,41 RRS 38,7- 8,7- 16,6- 0,3- 4,7- 0,08- 0,03- 0,05- 0,24- 1,8- 1,2- 59,0 20,3 38,8 2,2 12,1 5,3 0,34 0,15 2,6 2,2 2,7

*Мo= (CaO+MgO)/(SiO2+Al2O3); ** Кact = Al2O3/SiO2 Table 5. The resulting cast iron chemical composition, wt.%. С Mn Si P S 3,13 1,26 0,109 0,036 0,021

595 Journal of Chemical Technology and Metallurgy, 55, 3, 2020

Table 6. The calculation of the waste recycling annual balance. Material Content Annual Annual Annual lack/surplus Amount, The total amount in the recycling, waste for recycling, ton that can be of materials that blending, ton generation Lack Surplus involved in can be recycled in wt.% (calculated on the recycling, this way on 100% enterprise, ton LF slag ton utilization) ton/year % Limestone waste 17 9422,1 1513,3 7908,8 0 0 9422,1 11,2 Slag of steel 63 34917,4 109208,0 0 74290,6 0 34917,4 41,5 production (EAF slags) Gas cleaning 0 0 10532,9 0 10532,9 10532,9 10532,9 12,5 dust (EAF dust) Refining slags of 20 11084,9 11084,9 0 0 0 11084,9 13,1 out-of-furnace steel processing (LF slag) Scale from the 0 0 11378,9 0 11378,9 11378,9 rolling 11378,9 13,5 Scrap scale 0 0 6763,2 0 6763,2 6763,2 6763,2 8,0 Total 100 55424,4 150481,2 7908,8 102965,6 28675 84099,4 100

Table 7. The environmental effect calculation of proposed technogenic formations processing method implementation. Criterion Quantitative indicators per 1 ton Effect per 1 ton Portland cement clinker Cast iron Portland Cast iron Existing Developed Existing Developed cement technology technology technology technology clinker CO2 emissions, t including: from firing clinker (limestone) 0,57 0,09 0,05 0 0,48 0,09 from burning 0,73 0 1,9 0,27 0,73 1,63 The dust emissions, wt. % 6,4 0,5 0,95 0,5 5,9 0,45 Consumption of natural mineral resources, t. including: limestone 1,5 0,2 0,118 0 1,3 0,118 clay 0,15 0 0 0 0,15 0 the iron mixture 0 0 1,75 0 0 1,75 coke 0,2 0 0,52 0,075 0,2 0,445 gypsum 0,05 0,05 0 0 0 0 Water consumption 0,86 0 0 0 0,86 0 Thermal energy 3306,0 505,0 4001,0 612,0 2801,0 3389,0 consumption, MJ Electricity consumption 105,0 15,7 115,0 21,0 89,3 94,0

valuable commodity products (cast iron, Portland ce- % C3A, 3,8 % MgO, which meets the requirements of ment clinker and zinc oxide) for a single technological GOST 31108 “General construction Cements. Techni- cycle. The Portland cement clinker obtained in this way cal conditions». The yield of by this method with modular characteristics KN - 0,92, s - 2,3, p - 1,7 depends on the content of iron oxides in ORS. Since contained clinker phases: 51,3 % C3S, 30,1 % C2S, 10,7 the increase in the cast iron yield increases the process 596 Oleg Yu. Sheshukov, Michail A. Mikheenkov, Ilya V. Nekrasov, Denis K. Yeghiazaryan

profitability, it is advisable to involve all ma- waste, ORS, RRS and EAF dust to obtain valuable terials (scale, dust of arc furnaces) in addition to slags in commodity products. the processing, while a significant amount of zinc oxide accumulates in the dust captured during such processing. REFERENCES Without additional involvement of iron-oxide materials for the implementation of the method is the 1. A.V. Kaplan, T.V. Davydova, O.A. Gribkov, Ensuring composition, %: ORS - 60; RRS - 20; Limestone waste economic efficiency of metallurgical plants slag dumps (lime kiln dust) - 20. During the recycling process with restoration, Metallurg, 6, 2011, 86-88, (in Russian). this ratio, the yield of products is, %: slag (clinker) 82, 2. N.S. Anashkin, S.I. Pavlenko, Open-hearth slags cast iron 18. The resulting cast iron chemical composi- and their use in metallurgy and other industries of tion is shown in Table 5. Table 6 shows the calculation the national economy: textbook, Novosibirsk, SB of the waste recycling annual balance in this way. RAS, 2006, (in Russian). The analysis of the calculation results shows that 3. B.L. Demin, Yu.V. Sorokin, E.N. Shcherbakov, V.A. the amount of waste lime is not enough. The lack of Toporov, A.I. Stepanov, R.Ya. Sharafutdinov, A.V. lime is 7908.8 tons/year. This amount can be compen- Murzin, Technical solutions for processing of self- sated by limestone non-condensate screenings formed disintegrating slag, Ferrous metallurgy, 12, 2012, when sifting limestone before firing. Excess of EAF 63-70, (in Russian). slag, which cannot be processed by this method, is 4. O.Yu. Sheshukov, M.A. Mikheenkov, I.V. Nekrasov, 74290.6 t/year. Scale and EAF dust can be involved D.K. Egiazaryan, A.A. Metelkin, O.I. Shevchenko, in processing to produce cast iron. As a result of such Issues of steelmaking production refining slag uti- processing, 43203.3 tons/year of clinker and 20459 lization: monograph, Nizhny Tagil, NTI (branch) tons/year of cast iron will be obtained. With the correct Urfu, 2017, (in Russian). rational production organization scale and EAF dust 5. L.I. Leontiev, O.Yu. Sheshukov, M.A. Mikheenkov, should be melted separately from the slag, directly A.I. Stepanov, M.V. Zuev, Technological features on the cast iron, since the introduction of iron-oxide of processing of AEF and LF slag into building materials in the slag charge causes a shift in the clinker materials and experience of utilization of refining oxide composition and requires adjustment. Therefore, slag, Steel, 6, 2014, 106-109, (in Russian). melting of iron-oxide materials for cast iron and slag 6. M.A. Mikheenkov, O.Yu. Sheshukov, I.V. Nekrasov, materials for cast iron and clinker should be carried out D.K. Egiazaryan, D.A. Lobanov, Giving steelmak- in separate units. To ensure complete oxide materials ing slag properties of mineral binders, Steel, 3, 2016, processing for cast iron the melting unit productivity 65-69, (in Russian). should be 5 t/h, and for cast iron and clinker - 10 t/h. 7. L.I. Leontiev, O.Yu. Sheshukov, V.S. Tsepelev, Table 7 shows the environmental effect calculation of M.A. Mikheenkov, I.V. Nekrasov, D.K. Egiazaryan, proposed technogenic formations processing method Technological features of steelmaking slag process- implementation. ing into building materials and products, Building materials, 10, 2014, 70-73, (in Russian). CONCLUSIONS 8. M.A. Mikheenkov, O.Yu. Sheshukov, I.V. Nekrasov, The developed technology has been industrially A method for processing steelmaking waste to pro- tested and can be used to reduce the environmental duce Portland cement clinker and cast iron, Patent stress at the ferrous metallurgy enterprises in the in- 2629424 of Russian Federation, 2017, Bulletin No tegrated waste-free processing of all iron-containing 25, (in Russian).

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