International Iron & Steel Symposium, 02-04 April 2012, Karabük, Türkiye
HAZARDOUS WASTE GENERATION FROM INTEGRATED IRON AND STEEL PRODUCTION IN TURKEY - EVALUATION OF CLEANER PRODUCTION OPTIONS 1
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N. Cakir , G. Olmez , T. Karanfil , E. Alp , U.Yetis
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Department of Environmental Engineering, Middle East Technical University, Ankara, Turkey, E-mail: u
[email protected] 2 Department of Environmental Engineering and Earth Sciences Clemson University, Anderson, SC 29625, USA, E -mail:
[email protected]
Abstract In this study; with the purpose of evaluating hazardous waste generation form iron and steel industry and the best practices for their management, a site investigation coupled with literature survey was performed. Firstly; a complete material flow analysis was carried out to assess the generation of hazardous wastes from iron and steel industry. Then, types and amounts of hazardous wastes that arise from each process step in steel production were evaluated and hazardous waste generation factors (hwgf) for these wastes were determined. It was found out that there are five different types of hazardous wastes form steel manufacturing of which are sludge from coke oven containing tar, other sludges from coke oven, stack gas treatment sludge, mill scale and flue dust. Among these wastes, flue dust appeared to be major one as it is produced at larger quantities with the high hwgf of 48,5 (kg/ton steel produced) respectively. Secondly; cleaner production options for a better management of these hazardous wastes were evaluated considering the current applications in the pilot plant and also the relevant best available techniques given in the literature. After a detailed assessment of the cleaner production options for the management of the hazardous wastes, three alternatives have been identified as appropriate for the pilot plant which are hydrocyclone use and hot briquetting for zinc containing blast furnace and basic oxygen furnace stack gas treatment sludge and separating mill scale oil with centrifugal force. Keywords: Iron and steel industry; hazardous waste generation; best available techniques; cleaner production options
1. Introduction Iron and steel sector has a very substantial role in Turkish Economy with the share of 10% in Turkey’s total exports in 2010. According to the statistics published by World Steel Association [1], Turkey was the tenth crude steel producer in the world with the production of 29.1 million tones/year in 2 010 and 28.1 million tones/10 months in 2011. Although there was a decrease in the production in 2009 due to the economical crisis in all over the world, Turkish Steel Industry achieved a substantial increase in 2010 of %15.1 [2]. In Turkey; steel is produced by three integrated plants and more than 20 arc furnaces. Integrated iron and steel production that uses iron ore generates large quantity of hazardous wastes through coke making, sintering, iron making (Blast Furnace), steel making (Basic Oxygen Furnace), casting and hot rolling processes. The typical hazardous wastes from the industry include flue gas dust, stack gas treatment sludge and mill scale, all of which are iron based. Environmentally sound management of these wastes is a difficult task due to their huge amount. In the development of an effective and environmentally sound hazardous waste management system for any industrial activity, it is crucial to know the amount and composition of the hazardous wastes generated. The main policy in waste management in developed countries as well as in Turkey, is to apply the waste hierarchy principle. This principle provides a framework for waste disposal practices and defines the following priority order: prevention; re-use; recycling; and disposal. In accordance with this, the Turkish waste legislation requires encouragement to be given to the reuse, recycling and recovery of hazardous wastes. The EU’s Industrial Emissions Directive (2010/75/EU) (former Integrated Pollution Prevention and Control Directive, 96/61/EC) that defines the requirements for the minimization of pollution from various industrial activities necessitates either by reduction of hazardous characteristics or reduction of hazardous waste amount directly by process modifications or end of pipe treatment techniques based on best available techniques (BAT) which are the most effective techniques to achieve a high level of environmental protection. In this context, numerous sectoral reference documents documents (BREFs) have been published by the EU’s IPPC Bureau on BAT to set up an information exchange between industry and Member States regarding BAT. BREFs are the main reference documents used by competent authorities in Member States when issuing operating permits for the facilities that have an important pollution potential in Europe. The new IPPC Directive; Directive Directive; Directive on Industrial Emissions (2010/75/EU) that (2010/75/EU) that has been adopted on November 2010, requires industrial installations to adopt BAT that are defined in BREFs.
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It is known that most of the hazardous wastes produced in iron and steel sector can be recycled back to the system again. However due to the hazardous nature of some impurities existing in these wastes, their recirculation may not be possible or may be limited. With the application of BAT, these impurities can be reduced, thus their recycle and or reuse may be possible. Such practices may cause not only a reduction in disposal costs but also may reduce raw material consumption. The objective of this study is to determine the types and amounts of hazardous wastes arising from integrated iron and steel industry in Turkey and evaluate the most suitable BAT for these wastes with the aim of providing better hazardous waste management practices for Turkey in case of integrated iron and steel production. To this end, a pilot plant representing Turkish integrated iron and steel plant was selected and an on-site study was conducted in order to make an inventory of hazardous waste generation and to calculate hazardous waste generation factors. Moreover; using BREF on Iron and Steel Production (for sintering, coke making, blast furnace, basic oxygen furnace and casting) [3], and BREF on Ferrous Metal Processing (for rolling) [4], possible BAT options were identified for the pilot plant in consideration.
2. Methodology The study was carried out in an integrated iron and steel plant having a production capacity of 3.7 million tons/year crude-steel (in 2010) which is representative for Turkey. The study was consisted of four parts presented below. In the first step, a literature review was carried out in order to understand the manufacturing processes and the origin of hazardous wastes. All the unit processes in steel manufacturing were considered, major inputs to and outputs from the processes were identified and detailed process flow diagrams were prepared. During these studies, EU BREF Documents were mostly used. At the second step; a number of technical trips were made to the pilot plant and the processes applied were reviewed considering hazardous waste generation as of primary concern. All the inputs and outputs of each process step in the pilot plant were evaluated and their flowrates were determined. In order to make sure that flowrates gathered from the relevant department are correct; comprehensive mass balance calculations were made. Then, all wastes associated with each processes were identified; their type and quantity, as well as disposal methods were determined. Hazardous waste generation points in the production processes of the plant, how they are formed and which content make them hazardous were determined. With all these information, the wastes generated from the pilot plant were coded using the waste codes listed in Annex 4 to the Regulation for the General Principles of Waste Management (Official Gazette numbered 26927, dated 05.07.2008). Evaluation of hazardous waste generation factors (HWGF) was the third step in the study. After site evaluations, the HWGF were calculated simply by considering the yearly generation rate of each hazardous waste stream and the yearly steel production of the factory. Lastly, after the evaluation of all hazardous waste streams from the plant, potential techniques applicable for the minimization of hazardous waste generation were identified. In doing so; BREF documents were considered as the main references, possible BAT or cleaner production (CP) alternatives were determined; and during technical trips to the pilot plant, applicability of these CP alternatives was discussed with the technical staff of the pilot plant. Finally; BAT or CPs applicable under local conditions for the hazardous waste produced form integrated iron and steel plants were determined.
100207 100213
100211
Sintering
050601 050603
Coking
Basic Oxygen Furnace
Blast Furnace
Casting
Rolling
Pelletization
Figure 1. Flow scheme and HW generation points of integrated iron and steel production
3. Results 3.1. Types and Sources of Hazardous Wastes Generated
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After a number of technical trips to the pilot plant, detailed process flow diagrams were prepared, flowrates of all the streams were determined, mass balance calculations were made; and on this basis, hazardous waste generation rates were evaluated (results are not presented here). Flow scheme of the pilot integrated iron and steel plant is presented in Figure 1. As seen, the production process is conventional integrated iron and steel production that consists of seven sub-processes; sintering, pelletization, coking, blast furnace, basic oxygen furnace, casting and rolling. There is no peletization unit in the pilot plant as the plant prefers the use of readymade pellets. On-site evaluations in the pilot plant indicated that there are five major hazardous waste streams generated. These wastes are listed in Table 1 with their codes determined based on categorization given in the Annex 4 to the Regulation for the General Principles of Waste Management. Figure 1 presents the processes in which these waste streams are generated. In the “Regulation of General Principals of Hazardous Wastes Management”, hazardous wastes from integrated iron and steel production is listed under the titles of “0506-waste from the pyrolytic treatment of coal” (including coke oven) and “1002-wastes from the iron and steel industry”. Table 1. Hazardous waste types generated in iron and steel production Code
Waste Type
Waste Definition
Waste Origin
Sludge From Coke Oven Containing Tar
Coke Oven
0506 Waste from the Pyrolytic Treatment of Coal 050601
Acid Tars
050603
Other Tars
1002 Wastes from the Iron and Steel Industry 100207
Solid Wastes From Gas Treatment Containing Dangerous Substances
Flue Gas Dust
Blast Furnace
100211
Wastes from Cooling-Water Treatment Containing Oil
Mill Scale
Hot Rolling Mill
100213
Sludges and Filter Cakes from Gas Treatment Containing Dangerous Substances
Stack Gas Treatment Sludge
Sintering, Blast Furnace, Basic Oxygen Furnace
As shown in Figure 1, hazardous wastes entitled “acid tars” and “other tars” are generated from coking process; while wastes from flue gas treatment entitled “solid waste from gas treatment” and “sludge and filter cakes from waste treatment” originate from all three sintering, blast furnace and basic oxygen furnace stages. Casting and rolling stages appear to generate only the hazardous waste stream named “sludges and filter cakes from gas treatment containing dangerous substances”. In the proceeding paragr aphs, each waste is further described in a way that identifies hazardous properties. Acid tars and other tars These wastes arise from coke oven plant during coke oven gas treatment. Coke oven gas includes coke particles and tar, which are removed from coke gas by means of some physical operations. This mixture of coke particles and tar are removed from decanter in sludge form. This hazardous waste has the code 050601 if it contains acid; otherwise its code is 050603. Flue dust and stack gas treatment sludge Blast furnace, basic oxygen furnace and sinter plant top gases contain large amounts of iron dust. Iron dust can be removed from top gases either by dry methods (bag filter, electrostatic precipitator) or by wet methods (scrubber). If gas treatment is by dry methods; collected dust waste is coded as 100207. When wet methods are applied, the collected dust is in the form of a sludge with the code of 100213. Collected dust or gas treatment sludge from sinter plants is hazardous due to its high alkali content, and dusts and sludges from blast furnace and basic oxygen furnace are hazardous due to their high heavy metal content [5]. The heavy metal that exists in these wastes at relatively high concentrations is zinc. In the Literature, it is learned from the technical staff of the plant that the recirculation of sludge from blast furnace and basic oxygen furnace gas treatment may be limited by its high zinc content. Oily mill scale
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During hot rolling, water is used to clean semi-finished product (slab or bloom) from mill scale and to cool it. During these process, water is passed through the rolling machines thus gets contaminated by oil and oily mill scale. Cooling water containing oily mill scale is treated by chemical precipitation, its oil content is removed and then recirculated back to the process for use in cooling towers. Oily mill scale sludge removed from water is a hazardous waste due to its oil content and has the code of 100211. Its recirculation to the system may be limited due to its high oil content.
3.2. Hazardous Waste Generation Factors (HWGF) For all hazardous wastes produced in the pilot plant, HWGFs (in kg/ton steel produced) were calculated by dividing yearly generated hazardous waste amounts by yearly steel production. The results are presented in Table 2. As shown, the highest specific hazardous waste generation (or HWGF) is for “stack gas treatment sludge with the code of 100213”, generated f rom sintering, blast furnace and basic oxygen furnace units; and the lowest hazardous waste generation is from coke oven as “sludge containing tar” (coded 050603). “Stack gas treatment sludge” is generated at high rates from the units indicated above, because the plant mostly applies wet methods for flue gas treatment. In sinter plant and in blast oxygen furnace, flue gas treatment is only by wet methods whereas in blast furnace both wet and dry methods are used. The second highest HWGF was estimated for the flue gas dust from blast furnace as 8 kg/ton steel produced. On the other side, the generation rate for “mill scale” waste from the hot rolling stage was evaluated as 4.2 and 7.9 kg/ton steel, for bloom and slab, respectively. The distribution of hazardous waste generation among different waste types is shown in Figure 2. Based on the HWGF estimated for individual hazardous wastes, specific total hazardous waste generation for the pilot plant was estimated as 69 kg/tones steel. When the steel production of the pilot plant in the year 2010 is considered, the yearly hazardous waste generation appears as 255,000 tones of which 70 % is stack gas treatment sludge. The remaining 30 % is distributed between other four types of wastes. When hazardous waste produced at different production steps were compared, it is seen that the coke oven is with the smallest share while sintering, blast furnace and basic oxygen furnace are responsible for the highest generation (Table 2). Table 2. Hazardous Waste Generation Factors
Code
Waste
HWGF(kg/ton steel produced) Not produced in the pilot plant
050601 Sludge from Coke Oven 050603
0.42
100207
Flue Dust from Blast Furnace
8
100211
Mill Scale from Rolling
100213
Sludge from the treatment of stack gases from Sintering, Blast Furnace, Basic Oxygen Furnace
48.5
TOTAL
69.02
4.2 ( for bloom) 7.9 (for slab)
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Flue dust 12%
Seri 1, Sludge from coke oven containing tar, 0.42, 1%
Seri 1, Mill scale (bloom), 4.2, 6% Seri 1, Mill scale (slab), 7.9, 11%
Seri 1, Stack gas treatmen t, 48.5, 70%
Figure 2. Hazardous waste generation by type
3.3. Cleaner Production Options As presented above, all production steps in the iron and steel industry produce a vast amount of hazardous waste that requires special care. To solve this problem or to minimize the pollution from hazardous wastes, a series of possible cleaner production options that will result in significant reductions in the release of hazardous wastes were identified based on the BAT options evaluated from the literature and from the field study (Table 3). The following paragraphs introduce these cleaner production options with their expected benefits.
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Table 3. Cleaner Production Options Cleaner Production Options CP1
Target Waste Stack gas treatment sludge and flue dust
Process introduction
Process Use of hydrocyclone following blast furnace and basic oxygen furnace stack gas treatment process
Reducing Zn content of sludge or dust
Benefit/s Reduce iron containing hazardous waste amount Increase iron containing hazardous waste amount to be recycled to the sinter plant. Recovery of this valuable metal from this hazardous waste. Reducing iron containing hazardous waste amount to be disposed Increasing iron containing hazardous waste amount to be recycled to the sinter plant. Recovery of this valuable metal from this hazardous waste. Reducing iron containing hazardous waste amount to be disposed Increasing iron containing hazardous waste amount to be recycled to the sinter plant. Reducing iron containing hazardous waste amount to be disposed Increasing iron containing hazardous waste amount to be recycled to the sinter plant. Reducing iron containing hazardous waste amount to be disposed Increasing iron containing hazardous waste amount to be recycled to the sinter plant. Reducing iron containing hazardous waste amount to be disposed Increasing iron containing hazardous waste amount to be recycled to the sinter plant.
CP2
Stack gas treatment sludge and flue dust
Hot briquetting of stack gas treatment sludge following basic oxygen furnace stack gas treatment process
Reducing Zn content of sludge or dust
CP3
Stack gas treatment sludge
Using Unpainted/ungalvanized scrap in basic oxygen furnace
Reducing Zn content of sludge
CP4
Oily mill scale from hot rolling mill
Heating of oily mill scale from hot rolling mill
Reducing oil content of mill scale
CP5
Oily mill scale from hot rolling mill
Solvent utilization to separate oil and mill scale
Reducing oil content of mill scale
CP6
Oily mill scale from hot rolling mill
Separating mill scale oil with centrifugal force
Reducing oil content of mill scale
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CP 1. Hydrocyclone Use It is a method to reduce zinc content of blast furnace and basic oxygen furnace flue dust or sludge. By means of hydrocyclone use, following blast furnace and basic oxygen furnace stack gas treatment process, a zinc-rich and a zinc-poor sludge can be separated from each other. The zinc is mainly present in very small particles. In this method, small particles containing high zinc collected in overflow, where low zinc containing large particles collected in underflow. The sludge from the underflow is sent to the sinter plant to be reused in the system. The high zinc containing sludge from the overflow is stored or landfilled. It may be sent to zinc recovery facilities according to its zinc content. CP 2. Hot Briquetting This method is for zinc problem as well. In this method dust is physically shaped as cylindrical briquettes and sent to basic oxygen furnace. Recycling dust progressively enriches the zinc concentration. When the dust briquettes have reached to a certain level, it will be sent to zinc recovery. By means of this method, zinc content of the dust can be reached to 20-25%. CP 3. Using Unpainted/Ungalvanized Scrap The reason behind the zinc content of the dust form BOF is galvanized and painted scrap utilized. Using unpainted or ungalvanized scrap provides low zinc containing sludge or dust. However during the discussion with the technical staff of the pilot plant it is learned that to obtain unpainted or ungalvanized scrap in Turkey is almost impossible. For this reason this method is not suitable for conditions in Turkey. CP 4. Heating of Oily Mill Scale If the oily mill scale is heated up to 800°C, oil will be volatilized, clean mill scale is left. However this is an energy consuming method and may cause emission problems. This method is not economically and environmentally feasible. CP 5. Solvent utilization To separate oil and mill scale from each other, solvent may be used. However this method generates waste water containing solvent and oil. This method is not economically and environmentally feasible. CP 6. Separating mill scale oil with centrifugal force This is a method planned to be applied in the pilot plant. The working mechanism of the separation machine is centrifugation. Oil and mill scale is separated from each other by centrifugal force. Screening of the cleaner production or BAT options from the technical, environmental, economic feasibility and difficulty of implementation perspectives by a group of experts from the plant revealed that only three of the options ripe for implementation: hydrocyclone use and hot briquetting for Stack gas treatment sludge, and flue dust; separating mill scale oil with centrifugal force for oily mill scale. In the consideration of above-mentioned explanations, it can be mentioned that although there are plenty of methods for all hazardous wastes from integrated iron and steel production (except for the ones from coke oven), only some of them are economically and environmentally feasible and suitable under local conditions. In other words there are 3 different BAT to be applicable for the pilot plant and also for other integrated iron and steel plants in Turkey. However considering waste generation factors of their related hazardous wastes, among these 3 alternatives hydrocyclone use and hot briquetting are more substantial for the pilot plant.
4. Conclusions The outcomes presented in this paper are a result of a comprehensive study which aims to evaluate the types and amounts of hazardous wastes of an integrated iron and steel plant representative for Turkey. Based on the evaluations carried out in the pilot study, it was determined that the major hazardous wastes from iron and steel manufacturing are; stack gas treatment sludge that may originate from sintering, blast furnace, basic oxygen furnace and flue gas dust from blast furnace. However, other hazardous waste streams; mill scale from rolling and sludge from coke oven cannot be overlooked as these two wastes are also produced at large quantities. It was concluded that specific hazardous waste generation in steel manufacturing in Turkey is about 69 kg/ton steel based on the data gathered from the pilot plant. Furthermore, it was estimated that stack gas treatment sludge account for 70 % of this total hazardous waste generation. I. an assessment of the cleaner production options for the management of the hazardous wastes from iron and steel industry and their applicability to the pilot plant has revealed that three alternatives are appropriate for the pilot plant from the economic, technical, and environmental feasibility perspectives. these are the use of
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hydrocyclone and hot briquetting for stack gas treatment sludge and flue dust and separating mill scale oil from hot rolling mill with centrifugal force. however considering waste generation factors of their related hazardous wastes, two of them which are hydrocyclone use and hot briquetting were determined to be more substantial for the pilot plant.
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World Steel Association, Steel Statistical Yearbooks 2000 to 2011, retrieved from http://www.worldsteel.org/statistics/statistics-archive.htmlon 12.01.2012 Turkish Steel, A world leader in steel production, retrieved from http://www.turkishsteel.eu/index.php?option=com_content&view=article&id=4&Itemid=5on 12.01.2012 European Commission, 2001, IPPC Best Available Technique Reference Document on Production of Iron and Steel European Commission, 2001, IPPC Best Available Technique Reference Document on Ferrous Metal Processing T.C. Çevre ve Orman Bakanlığı, LIFE HAWAMAN Projesi Tehlikeli Atıkların Sınıflandırılması Klavuzu Cilt 2, 2009
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