DIOXFREE – POWDERED ACTIVATED CARBON INJECTION (ACI) SYSTEM TO CONTROL EAF'S DIOXIN AND MERCURY EMISSION BY ALDO GIACHERO SILVIA TOSATO
ABSTRACT Mainly depending on the charged scrap quality, Electric Arc Furnace (EAF) steelmaking plants can be a source of dioxins and mercury emission to air. Emission limits at the stack and pollution prevention practices for the control of these pollutants are currently governing steel plants in Europe and USA, and are expected to become more restrictive, as general awareness increases and BATs become available. Polychlorinated-dibenzo-p-dioxins (PCDD) and polychlorinated-dibenzofurans (PCDF), commonly referred to as “dioxins”, are a family of chlorinated hydrocarbon compounds, some of which are classified as toxic for humans by the United Nations Environment Programme (UNEP). Mercury is a heavy metal defined by UNEP as a global threat to human and environmental health. Dioxins are unintentionally formed in the EAF Steelmaking process and emitted to the air through the stack. The most common source of mercury in the EAF is the contaminated scrap. Today new emission control technologies are available for the control of dioxins and mercury: DIOXFREE is a powdered Activated Carbon Injection (ACI) system, installed in some European EAF plants, to remove, by means of the adsorption process, dioxins and mercury from the flue gasses, ensuring the compliance with the most severe emission limits that cannot be respected only by implementing pollution prevention practices.
KEYWORDS: Air, Emission, Mercury, Hg, Dioxin, PCDD, PCDF, Powdered Activated Carbon, PAC, ACI, Injection, Adsorption, EAF, Fume, Dedusting, Steelmaking
ALDO GIACHERO Product Manager – TTF, Genova, Italy SILVIA TOSATO Environment Regional Specialist – Dalmine SpA, Dalmine (Bergamo), Italy
1
1
INTRODUCTION
PCDD and PCDF are two of the twelve Persistent Organic Pollutants (POPs) included in the Stockholm Convention [14] by the United Nations Environment Programme (UNEP), as they persist in the environment, accumulating in the soil through atmospheric deposition and resisting to all forms of environmental degradation. In the Steel Industry, the Electric Arc Furnace (EAF) plants are considered to be a significant contributor to such pollutant emission due to the use of steel scrap potentially contaminated with organic substances (chlorinated plastics, paints, oil etc). During the steel melting process, dioxins/furans can be formed in the EAF and in the fume treatment plant from related chlorinated precursors or via De Novo Synthesis then released into the atmosphere with the treated fume. Mercury is still used today in a wide range of products, including batteries, paints, switches, electrical and electronic devices, thermometers, blood-pressure gauges, fluorescent and energysaving lamps, pesticides, fungicides, medicines, and cosmetics. As reported in the Global Mercury Assessment 2013 by the United Nations [1], once used, many of the products and the mercury they contain enter waste streams. While mercury in landfills may slowly become re-mobilized to the environment, waste that is incinerated – or melted, in the case of scrap – can be a major source of atmospheric mercury. Steel plants and in particular the electric arc furnaces are recognized as a significant source of mercury emissions right after the Coal-fired Power Plants, which represent the biggest source of mercury emissions in the atmosphere. The EU Member State Authorities are prescribing increasingly more stringent standards emission limits for the Steelmaking Plants: this called the main steel producers to find technical solutions to control the emission of these kinds of pollutants in their EAF mills.
2
PCDD – PCDF
Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), commonly referred to as Dioxin/Furans, are tricyclic, aromatic compounds formed by two benzene rings connected by two oxygen atoms in polychlorinated dibenzo-p-dioxins and by one oxygen atom and one carbon-carbon bond in polychlorinated dibenzofurans and the hydrogen atoms of which may be replaced by up to eight chlorine atoms. There are in total 75 PCDD congeners and 135 PCDF congeners. The physical–chemical properties of these compounds are affected by their chlorination level.
Fig. 1: Structural Formula of 2,3,7,8-Tetrachlorodibenzodioxin PCDD and PCDF are almost insoluble and have a low volatility under normal air pressure. They are lipophilic and concentrate in animal and human adipose tissues. Fat solubility as well as vapour pressure have the following attitudes that depend on the rate of chlorination: - The fat solubility increases at a higher rate of chlorination; - The vapour pressure of PCDD and PCDF decreases at a higher rate of chlorination. 2
Congeners with chlorine substitutes in the 2,3,7,8-position, 7 of 75 PCDDs and 10 of 135 PCDFs, are classified as toxic for humans, each one with an assigned toxicity level. The Toxic Equivalency Factor (TEF) shows the toxicity of a special compound in relation to the most toxic substance. Tetrachlorodibenzo-p-dioxin (TCDD) is the reference compound to assign the toxicity equivalent factor for related congeners. DIOXIN CONGENERS PCDD 2,3,7,8 TCDD 1,2,3,7,8 PCDD 1,2,3,4,7,8 HxCDD 1,2,3,7,8,9 HxCDD 1,2,3,6,7,8 HxCDD 1,2,3,4,6,7,8 HpCDD OctaCDD
NATO 1988 TEF 1 0,5 0,1 0,1 0,1 0,01 0,001
FURAN CONGENERS PCDF 2,3,7,8 tetraCDF 2,3,4,7,8 PCDF 1,2,3,7,8 PCDF 1,2,3,4,7,8 HxCDF 1,2,3,7,8,9 HxCDF 1,2,3,6,7,8 HxCDF 2,3,4,6,7,8 HxCDF 1,2,3,4,6,7,8 HpCDF 1,2,3,4,7,8,9 HpCDF OctaCDF
NATO 1988 TEF 0,1 0,5 0,05 0,1 0,1 0,1 0,1 0,01 0,01 0,001
Fig. 2: Dioxin and Furan Congeners TEFs (NATO 1988 TEF values).
3
PCDD/F FORMATION MECHANISM
Dioxin/Furan formation pathways are influenced by different factors, as temperature, the presence of organic precursors, as PCB, PCP, polychlorinated benzenes and diphenylethers, and metal catalysts as copper. A brief description of the main PCDD/PCDF formation mechanisms is synthesized below. Condensation The condensation reaction consists in the condensation of two chlorophenol molecules. Phenolic compounds adsorbed on the dust particle surface are chlorinated to form the precursor, and the dioxins/furans are formed from the breakdown and molecular rearrangement of the precursor. This reaction mostly occurs at temperatures lower than 350°C. Substitution Polychlorinated dibenzodioxins/furans can be formed from none or single halogenated dibenzodioxins and dibenzofurans, by means of the substitution of hydrogen by chlorine in the 2,3,7,8-position with the presence of a metal catalyst. Radical Dioxin/Furan formation involves a radical reaction between simple carbon radicals and chloride radicals under high temperature conditions (Huang & Buekens, 1995). In this reaction organic precursors combust with chlorine compounds at 300°C to 600°C. De Novo synthesis The De Novo Synthesis occurs at a temperature of 250÷450 °C as the formation of dioxins and furans compounds from non-chlorinated materials, with the presence of chlorine compounds and carbon, supported by catalytic reactions with metal. The important start reaction is the formation of chlorine from copper and other metal chlorides with oxygen. The de novo reaction is characterized by its long reaction time. Above 800°C, the pyrolysis (thermal decomposition) and the reaction with oxygen start. At the cool down process dioxins and furans can be reformed by the de novo reaction. These opposite reactions lead to the typical dependence of PCDDs/Fs on the temperature. 3
4
PCDD/F EMISSIONS TO AIR IN EAF STEELMAKING
The range of dioxin/furan emission from EAF steelmaking process is very wide, from 0,04 to 6 μgITEQ/ton liquid steel [5]. These differences in the dioxin/furan emission depend on different types of scrap charge, varying conditions into the EAF resulting from changes in EAF operating practices that could change from heat to heat and plant to plant, different fume cooling and dedusting systems, and different bag filter efficiencies. Correspondingly, concentrations at stack between 0,02 and 9,2 ng-ITEQ/Nm³ have been measured [5]. 4.1
Formation in the EAF
Dioxins/Furans appear to be formed in the EAF process from related chlorinated precursors and via De Novo Synthesis from chemically unrelated compounds such as polyvinyl chloride (PVC) and other chlorocarbons, i.e. by the combustion of non-chlorinated organic matter such as polystyrene, coal and particulate carbon in the presence of chlorine donors. Many of these substances can be contained in trace concentrations in the steel scrap or are process raw materials such as injected coal. The graphite electrodes represent another source of carbon. The environment inside the EAF is constantly varying and can produce conditions that are favourable for dioxin/furan formation. The organic compounds contained in the scrap may be vaporized, cracked, partially or completely combusted. It may be possible to have formation of dioxins/furans in one area of the EAF, while thermal decomposition is taking place in another area, depending on the conditions in the furnace or parts of the furnace during or after charging. The increase in the oxygen concentrations promotes PCDD/F formation. Since the gas contained in the furnace is not homogeneously mixed, not all the PCDD/F formed in the low temperature areas can be thermally decomposed and a portion of them is expected to leave the EAF in the off-gas. 4.2
Formation in the Fume Dedusting System
The EAF Fume Dedusting System operational conditions may be favourable for De Novo Synthesis formation of dioxins/furans: the thermal profile of the fume treating process strongly affects the generation of these organic compounds. The EAF off-gas is cooled down to reach the required filter inlet temperature, which usually must be lower than 130 °C; part of the dioxins/furans contained in the fume condenses and is adsorbed by dust particles that are separated in the bag filter. Condensation starts in the 125÷60 °C range with the higher chlorinated dioxins and increases very rapidly as the temperature drops. The lower chlorinated furans are the last to condense, which explains why they often constitute the majority of the congeners observed in EAF emission tests. Several variations of the fume temperature at the filter inlet, typically in the 50÷125 °C range, occurring during each tap-to-tap time, lead to changes in the PCDD/F adsorption/desorption equilibrium. When the temperature rises, the dioxin/furan vapor phase fraction in the fumes gets higher resulting in higher concentrations at the stack. The PCDD/F formation, their vapor/solid phase ratio and their adsorption/desorption equilibrium are strongly affected by the temperature; this must be carefully taken into account in the choice of the system to be installed for the dioxins and furans emission control in EAF plants. It is insufficient to provide the Fume Dedusting System with a fast quenching unit in order to minimize the residence time of the fume in the De Novo Synthesis temperature range: the low temperatures of the EAF off-gas (150÷500 °C) during some phases of the process, e.g. during scrap charging or first step of melting, lead to the formation of dioxins and furans in the system upstream
4
of the quenching section: these formed PCDDs/Fs flow in the fume stream without encountering the condition for the thermal decomposition. To solve the above mentioned problems, a post combustion should be provided to maintain the fume temperature upstream of the fast-quenching above 850 °C, in order to perform the PCDD/F thermal decomposition and avoid reformation. This solution is confirmed to be very expensive in terms of energy consumption and cannot guarantee the complete compliance with the emission limits required by the Authorities. The experience of several European steel companies shows that a completely reliable control on the dioxin and furan emission is achievable only by means of the installation of a system suitable to operate efficiently during all the EAF plant process phases.
5
MERCURY EMISSIONS TO AIR IN EAF STEELMAKING
In the EAF steelmaking, different grades of scrap metal are recycled: this material is contaminated by the presence of chemical substances and thus various root sources of emissions are plausible. The most common source of mercury comes from scrap obtained by old motor vehicles containing mercury switches. Nonetheless, other sources have to be considered too: mercury coming from nonautomobile scrap can be a significant portion of total mercury present in the charge, and it is not removed by the switch removal program. Scrap quality is the most influencing factor for mercury emission from EAF facilities, but also other raw material should be considered as mercury sources: according to a study by the Swedish Environmental Research Institute, fluorspar (CaFâ‚‚) contains 1,1 ppm of mercury [11]. Other raw materials contain up to 0.2 ppm of mercury, as per a more recent investigation by the Norwegian steel plant of Mo i Rana in 2004. Based on an addition of 150 kg of fluorspar per heat, the concentration of 0.2 ppm of mercury from the raw material becomes 0.3 gram of mercury per heat [4]. The following diagram shows the mercury content of various raw materials involved in the EAF steel melting process.
Fig.3: Parts per million of mercury in EAF-related materials [4] 5
In the Nordic steel mills continuous measurement of mercury emissions was implemented in the years following these studies, but a consistent correlation between raw materials input and emission peaks has not yet been demonstrated. 5.1
Mercury in the EAF’s Flue Gas
In the case of Mercury, in general, things get more complicated than for PCDD-F case, and for the EAF very few full-scale tests results are available. Based on the theory and on tests carried out for Coal Fired Power Plants we can assume the following: There are 3 forms of Mercury-based pollutants: elemental Hg (Hg⁰), particulate Hg (Hgp) and reactive (divalent) gaseous mercury (Hg2+) [2-3], each one with different chemical characteristics and behavior. The determination of these three forms of mercury in the flue gas is called the speciation of mercury. Emissions from steelmaking have historically been believed to be comprised of approximately 80 % Hg0, 5 % HgP and 15 % Hg2+ [4]. For this reason, injecting a sorbent material upstream of the Bag Filter, efficient in capturing gaseous mercury in the Hg⁰ form at lower temperatures (50-120 °C), is the most effective way to achieve the required mercury abatement. The following table provides an overview of the specific emission factors that can be used as reference for the emission floor assessment in USA and Europe: SOURCE
EMISSION FACTOR
EPA: AP42 – 2009
0,000110 [lb/ton]
IPPC: EUR 25521 EN 2013
NOTES
55 [mg/tls] (*)
0,000004 [lb/ton]
2 [mg/tls]
Minimum value
0,000400 [lb/ton]
200 [mg/tls]
Maximum value
(*) “tls”: metric tons of liquid steel
Fig.4: EU – US Mercury Emission Factors Comparison 6
RULES
Mercury and dioxin emission limits at the stack are currently governing steel plants in Europe, but not steel plants in the US. Yet in Europe those limits are expected to become more restrictive as general awareness increases and BATs (Best Available Techniques) become available to the industry [5]. It has to be noted that the U.S. Environmental Protection Agency (EPA) rule in force today is based on pollution prevention [6-7]. Such rule requires eliminating mercury at the source: scrap proceeding from motor vehicles has to be decontaminated from mercury switches before it can be melted in EAF facilities. Future revisions could lead to mercury stack emission limit and continuous emission monitoring requirements in the US. European Best Available Techniques for EAF Steelmaking Facilities are: Mercury • BAT for the electric arc furnace (EAF) process is to prevent mercury emissions by avoiding, as much as possible, raw materials and auxiliaries which contain mercury. • The BAT-associated emission level for mercury is < 0,05 mg/Nm³. Dioxin (PCDD-PCDF) • The BAT-associated emission level for Polychlorinated Dibenzodioxins/Furans (PCDD/F) is <0.1 ngI-TEQ/Nm³. 6
7
DIOXFREE: POWDERED ACTIVATED CARBON INJECTION SYSTEM
DIOXFREE is a Powdered Activated Carbon (PAC) injection system, with process specificities and design features leading to the achievement of the required abatement efficiency together with the minimization of the PAC injection. 7.1
PROCESS DESCRIPTION
The basic principle under which the PCDD/F control is performed is the adsorption: this term means the attachment of molecules (in this case PCDDs/Fs, Mercury, PAH and other pollutants) to the surface of a solid. To obtain an efficient adsorption, the following requirements need to be satisfied: - Sorbent must have large surface areas; - Sorbent must have micropores; - Sorbent chemical characteristics must be considered especially for the case of mercury control; - Good contact time for an efficient separation (a good distribution in the flow is mandatory); - The sorbent dosage must be regulated according to the fumes variable conditions. To reach the required results the following factors have been considered in the design: the system operates using PAC as adsorbent material; each PAC particle has an extremely large surface area (surface to weight ratio > 400 m²/g) with micropores, which helps it to easily adsorb gaseous pollutants. Different kinds of PAC are available on the market, so the choice must be done considering the process characteristics. Chemically embedded activated carbon (specifically sulphur, chlorine, bromine) enhances the uptake of mercury: this solution is sometimes adopted in coal combustion facilities, depending by the chemical composition of the flue-gas. The contact between PAC and gaseous PCDDs/Fs is very strong when the fumes pass through the dust cake accumulated on the fabric bags, so it is very important to ensure a good PAC distribution on the whole filtering surface. A CFD model is usually developed to improve the distribution of activated carbon taking into account the plant peculiarities. 7.2
PCDD-F MEMORY EFFECT
The high levels of PCDD and PCDF concentrations contained in the fume from the EAF during the period of operation without proper abatement, previous to the installation of the PAC Injection System, can be responsible for a contamination of the clean side of the Fume Dedusting System including all the elements downstream of the fabric bags. The DIOXFREE installation leads to the abatement of vapour phase dioxins and furans contained in the fume upstream of the fabric bags. Downstream of the filtering elements, the adsorption/desorption equilibrium depending on the temperature variations can often lead to the PCDD/F desorption from the contaminated elements to the cleaned fume, affecting the expected abatement performances. This effect is called Memory Effect and should be considered during a short period of regular plant operation subsequent to the start-up phase, after which the clean side contamination will be removed. 7.3
SYSTEM DESCRIPTION
Pac Storage Silo The PAC (Powdered Activated Carbon) storage is performed by means of a 50 m³ capacity silo complete with hopper, discharge and dosing systems. The PAC is pneumatically unloaded from a bulk truck transport trailer with the truck’s compressor and hoses and then charged into the silo. The silo is equipped with fluidization nozzles and a vibrating bottom to prevent powder bridge 7
formation. A feeder delivers the activated carbon to a rotary valve and the PAC is pneumatically conveyed as a dilute phase mixture to the injection point. The silo shall be equipped with pulse jet type vent filter, suitable for air dedusting during filling operations and all the devices that make its conformity with ATEX standards. Injection System The PAC is pneumatically conveyed into the fume duct. The injection system is constituted by the following items: - Dosage Regulation Unit, able to perform a multi-way dosage that gives the system the necessary versatility to achieve the maximum efficiency in all working conditions with the lowest PAC consumption (operational cost optimization). - PAC Blowing Unit and conveying system. - Injection Unit: thanks to the CFD analysis the nozzles system configuration can be customized on a case-by-case basis in order to obtain the best distribution of the PAC on the filter bags. - The Carbon content in the dust collected by the bag filter should not exceed 5% in order to avoid the risk of self-ignition in the dust hoppers. Control Room A suitable continuous weighing and feeding system has been adopted to optimize PAC dosage according to the different process parameters. The dosage can be set to a fixed quantity [kg/h] or variable according to parameters as fume temperature [°C] and flow-rate [mg/Nm³]. These functions can be carried out positioning a remote programmable logic controller (PLC) complete with an interface panel arranged with the needed selections. The system can be easily monitored remotely to check in real time all process variations and possible unexpected system arrests.
FUME DUCT PAC STORAGE SILO
INJECTION SYSTEM
CONTROL ROOM
Fig. 5: ACI System Typical Arrangement
8
8
TENARIS DALMINE PLANT ACI INSTALLATION
DIOXFREE technology was pioneered by Tenaris Dalmine.
Fig. 6: DIOXFREE Installation
Fig. 7: Tenaris Dalmine EAF Dedusting System: Flow Sheet The installation of the package for the 140 t/h EAF took a total of five months in which design, supply and assembly were completed. The system went into operation two years ago, and has been in continuous service since then. 9
Main Plant Data: Electric Arc Furnace: Tap to tap: Fume Treatment Plant: Preheating Station: Installation: Injection: PAC: Mean PAC Granulometry: PAC Silo: Injection System: Dosage: PAC Flow Rate: PAC Concentration in fume: Selectable 3-ways Dosage:
140 t/h 40 min 2 filtering units (primary and secondary fumes + 2 LF) scrap heating provided by primary fumes operating for primary fumes plant 750.000 m³/h upstream bag-filter high surface to weight ratio 20 µm 50 m³ capacity pneumatic conveyor in dilute phase micro-dosage in continuous regulation 10 ÷ 100 kg/h 20 ÷ 100 mg/Nm³ 1) Fixed PAC concentration in the fumes 2) Variable PAC concentration according to fume temperature 3) Fixed PAC flow rate Fig. 8: Main Plant Data
Previous to the installation, several PAC injection tests were carried out injecting the activated carbon into the duct upstream the bag filter with variable dosage, ranging from 40 to 130 mg/Nm³. The dioxin/furan abatement performances resulted in emissions at stack ranging from 0,02 to 0,1 ng-ITEQ/Nm³, depending on the quantity of injected PAC and process conditions. To ensure the best PAC distribution on the whole filtering surface, a Computational Fluid Dynamics (CFD) model were developed in order to improve the PAC distribution in the fume flowing to the bag filter sections: adsorbent particles were tracked using the Discrete Particle Modelling (DPM) method. The Bag Filter is divided in two units as represented in Fig. 9: CFD model shows the PAC particles path to the filter bags in the different configurations. After the analysis the injection system was optimized according to the configuration leading to the best distribution.
Fig. 9: CFD Model
10
8.1
SAFETY
DIOXFREE system has been designed in compliance with the EU directives 1999/92/EC and 94/9/EC, concerning explosion protection measures to guarantee the highest possible level of safety in areas where combustible dusts or gases are or may be present. PAC injection system has been conceived to prevent the formation of explosive atmospheres but considering the possibility of a dust cloud presence, suitable devices have been installed both to avoid explosion and to contain its effects. 8.2
ABATEMENT PERFORMANCES
After the start-up, several performance tests were carried out in heavy operating conditions of the EAF with various running conditions of the Fume Cooling and Dedusting plant. The PAC injection is automatically adjusted according to the fume temperature and performed values of dioxin/furan concentration at the stack always resulted below the limits required by the Authorities. In the following graph the measured values and trends of dioxin/furan concentration at the stack, with and without PAC injection, are compared. The blue points represent all the measurements taken after the DIOXFREE start-up. Red points are related to the previous tests without PAC injection.
Fig. 10: PCDD/F Abatement Performances In order to represent the real effect of activated carbon injection, the reported values are those obtained after the increase by 50% of the primary fume filtering capacity, so all the values refer to comparable plant operating conditions. Each plotted point represents the PCDD/F average concentration and temperature detected during an 8 hours sampling time. It is to be noted that, considering the EAF process, an average fume temperature of 85 째C includes several periods during which the temperature reaches 120 째C. 11
The value higher than 0,1 ng-ITEQ/Nm³ at 85°C was measured less than 2 months after the start-up of the system, while the value of 0,1 ng-ITEQ/Nm³ at 86°C was measured about one year later. In both cases the EAF was operating in heavy condition, so the PCDD/F concentration difference between these two values can be explained as a consequence of the memory effect occurring in the first period of operation of the system. In all the other cases the dioxin/furan abatement performances led to concentrations in the 0,02÷0,1 ng-ITEQ/Nm³ range, in line with the more stringent emission limits that could be imposed in the future. DIOXFREE is performing PCDD/F abatement leading to emissions at the stack much lower than the limits required by the Authorities. An important aspect to be considered is that, as showed in Fig. 7, the Tenaris Dalmine EAF primary and secondary fume control have two dedicated dedusting units and not only one dedusting system as usual in the EAF steelmaking plants. Considering that almost the total amount of generated PCDD/F flows through the primary fume line, the concentration of PCDD/F referred to the total amount of off-gas captured by the two dedusting units (and not only to the primary system flowrate) is still lower. The installation of DIOXFREE system led to the significant reduction of PCDD/F emission, as well as mercury, PCB and PAH. In the following table the pollutant concentrations at the primary stack are compared for two years pre and post dedusting plant improvement investments.
PRE POST POLLUTANT IMPROVEMENTS IMPROVEMENTS YEAR (*) YEAR (*) PAH (Bohorneff series) [μg/Nm³] 3,76 0,14 Hg [mg/Nm³] 0,0036 0,0016 PCB tot. [μg/Nm³] 0,23 0,01
Fig. 11: Pollutants concentration pre and post improvement (*) All concentration values are referred to a common flow rate reference value. This environmentally-effective solution allows Tenaris Dalmine to meet the highest air emission standards and to continuously improve the level of environmental protection. Tenaris Dalmine experience shows that DIOXFREE is an easy-to-use tool, designed to maximize the PCDD/F abatement with the lowest use of resources (PAC and utilities) and with a plant operational cost of approximately 0,23 €/tsteel. The full compliance with the more stringent emission limits required by the Authorities is guaranteed thanks to the great operational flexibility of the system.
12
REFERENCES 1. UNEP, 2013. Global Mercury Assessment 2013: Sources, Emissions, Releases and Environmental Transport. UNEP Chemicals Branch, Geneva, Switzerland, pp. 26, 65 – 67, 228. 2. W. Schroeder, et al.; Atmospheric mercury—An overview; Atmospheric Environment, Vol. 32, Issue 5, Mar. 1998, Pages 809–822 3. L. Poissant, et al,; Atmospheric mercury speciation and deposition in the Bay St. François wetlands; Journal of Geophysical Research. Vol. 109, Issue D11, 16 June 2004. 4. D. Roseborough, et al.; Mercury Emissions from Steelmaking: A Review, Jernkontorets Forskning D825, May 30, 2008 5. Commission Implementing Decision of 28 February 2012 establishing the best available techniques (BAT) conclusions under Directive 2010/75/EU of the European Parliament and of the Council on industrial emissions for iron and steel production; Official Journal of the European Union; Mar. 8, 2012 6. Emission Factor Documentation for AP-42, Section 12.5.1, Iron and Steel Production, Steel Minimills, Final Report; U.S. Environmental Protection Agency; April 2009 7. Environmental Protection Agency 40 CFR Part 63; National Emission Standards for Hazardous Air Pollutants for Area Sources: Electric Arc Furnace Steelmaking Facilities, Final Rule; Federal Register; Vol. 72, No. 248; Dec. 28, 2007 8. Environmental Protection Agency; 2008 National Emissions Inventory, version 2, Technical Support Document, June 2012, pp. 25 – 26. 9. Environmental Protection Agency 40 CFR Parts 60 and 63, Reconsideration of Certain New Source Issues: National Emission Standards for Hazardous Air Pollutants From Coal- and Oil-Fired Electric Utility […]; Federal Register, Vol. 78, No. 79; Apr. 24, 2013 10. Eric Stuart, Environment & Energy Issues Impacting U.S. EAF Steelmaking Sector, AIST Italy Steel Forum 2012, Castellanza, Italy; Oct. 18, 2012, pp. 7 – 8. 11. K.E. Kulander: Report No. T880076, IVL Swedish Environmental Research Institute, Stockholm, Sweden, Jan. 1988 12. CEI EN 61241-10 (2007) Classification of Areas Where Combustible Dusts Are or May Be Present. Milano Italy CEI. 13. Stockholm Convention Secretariat (2001) Stockholm Convention On Persistent Organic Pollutants - Annex C. 14. Canadian Council Of Ministers Of The Environment (2003) Canada-Wide Standard for Dioxins and Furans: Steel Manufacturing Electric Arc Furnaces. 15. Aldo Giachero, Francesco Memoli; Powdered Activated Carbon Injection System to Control Mercury Emission; Industrial Heating Magazine, August 2013.
13