2. Environmental governance and Taiwan’s EAF steel industry
2.2 Environmental issues and mitigating technologies
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allowed to cool and solidify) according to the company’s or clients’ preferred specifications.
Before the 1960s, most steel firms poured the molten medal into permanent molds, one-by-one.
Thanks to modern metallurgy techniques, a more popular method today called continuous casting works by pouring metal from a ladle through a vertical gas-tight refractory tube and into a “tundish,” a special reservoir that allows the steel to continue to flow vertically at a controlled rate through parallel gas-tight refractory tubes before reaching water-cooled copper molds. With only the outer shell solidified, the steel is then pressed on a curve under a system of rollers and water sprays until it emerges horizontal as a parallel series of long strands of a particular size and width (different configurations exist with specialized machinery) and a mechanized torch cutter cuts each strand to size. This method saves on energy and water as well as reduces emissions.
The European Commission’s 2013 BAT report states that 90% of global steel is cast using the continuous method, which includes every EAF facility in Taiwan.
2.2 Environmental issues and mitigating technologies
The following paragraphs tackle the six main environmental issue areas associated with EAF steel production as well as the industry-standard environmental technology used to combat these problems (i.e., potential targets for EMS development). Generally speaking, the six
environmental issue areas at stake are as follows: waste management, air pollution (including greenhouse gas (GHG) emissions), energy consumption, water use and spatial planning. With the exception of spatial planning, all these areas are included in the Best Available Techniques Reference Document for Iron and Steel Production published by the European Commission, which is the basis for the survey data I collected. These areas, however, are not equally important with respect to their levels of environmental impact. According to Ioana and Balescu (2009) and several of my interviewees, the main ecological issues with EAF steel production have to do with powder collection (waste management) and harmful gas control (air pollution). The following paragraphs will explore these environmental issues one by one as well as the industry standards and technologies used to mitigate their negative impact on the environment, beginning with the topic of waste management.
Waste management in EAF facilities targets industrial byproducts such as powders and slag. Tay Joo Hwa, researcher from the School of Civil and Structural Engineering at Nanyang Technological University in Singapore, describes industrial waste management as a process of at
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least five (and sometimes six) steps.10 The first stage involves a collection process. On a comprehensive scale, waste collection may be as complex and technology-based as specialized filtration devices that capture particles of a certain size as they are expelled through a drain or vent, or it can be as simple as office trash collection. The next phase involves storage of waste.
Waste will accumulate in storage units until it is ready or able to move to the next stage. The third stage of the waste management process depends on whether or not a company processes its waste on-site. If the company has the capital and technical expertise necessary to process on-site, then the next stage is waste treatment. If not, then the waste in storage must be transported elsewhere for treatment; this is the case in Taiwan, where organizations like the Taiwan Steel Union Co. are charged with treating hazardous EAF dust.11 After waste treatment, Hwa labels the final two stages “disposal” and “control.” The most environmental form of disposal is
through recycling and re-use; some of the mineral elements in EAF dust can be extracted and put to use in other industries as raw materials (through processes discussed later), as in magnetic metals from iron oxide dust. The control stage is rather vague in Hwa’s report, but the term suggests maintenance, planning and care for the sites (e.g., landfills) where waste disposal occurs. Figure 1 illustrates the waste management process.
Figure 2: The waste management process
Source: Hwa, 2001
The biggest waste management hurdle EAF firms must tackle involves the prodigious amounts of powder, or dust, the industry generates. The release of airborne powder occurs at every stage of the EAF process, from loading to evacuation, and about 20 kilograms of powder is released per ton of steel (Boyanov & Baev, 2009). The fine powder contains a variety of heavy
10 Hwa, J.T. (2001). Integrated report. In Hazardous Waste Management Policies and Practices in Asian Countries. Tokyo: Asian Productivity Organization.
11 A 1999 amendment to the Waste Disposal Act called on SME firms to create their own waste disposal organizations and cooperate in waste management.
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metals, including chromium, nickel, zinc, lead and more. Although heavy metals are naturally occurring in the environment, the higher concentrations of these substances through human industry make these substances highly toxic in the human body and surrounding environment.
For instance, chronic exposure to hexavalent chromium has been linked to scarring and cancer of the lungs12, and the banning of lead paint, lead pipes and tetraethyl lead (the key additive in leaded gasoline) after industrial lead poisoning incidents (involving brain, kidney and
cardiovascular damage and death) and public health concerns shows the dangers associated with this element. Some EAF facilities can also test positive for arsenic in their waste output. In short, EAF dust is classified as a hazardous waste material because of its potential to leach into the ground and contaminate ground water and soil.
To counteract the negative impact from EAF powders, the global and domestic steel industry has implemented a variety of technology-based systems to a.) capture and filter emissions and b.) store and eventually extract useful components from these powders for reuse and, in some cases, to sell. In cases where extraction is not possible due to a lack of capital or technology and expertise, long-term storage is the only viable option from an environmental standpoint.
Emissions, composed of both gas and airborne EAF powder, are classified according to when they are generated in the steelmaking process. Emissions produced in the furnace during melting are called “primary off-gases” and account for 95% of total emissions — or about 10 times more gas than is produced after melting. Secondary emissions come about during scrap handling, charging and tapping as well as when fumes escape the furnace through the electrode openings or other leakage points. The steel industry at large has developed four main captivation systems (typically used in combination) to manage all steelmaking emissions: a “4th hole” system for primary off-gases as well as a canopy hood, a doghouse system or total building evacuation for secondary off-gases. The 4th hole system captures emissions from the melting stage using an opening in the furnace beside the area where electrodes protrude. Some older facilities still operate with only 4th hole extraction, disregarding secondary emissions collection entirely. A canopy hood can be installed above the furnace, charging area and/or refining area in a partially
12 See Langrrd, S. (1990). One hundred years of chromium and cancer: A review of
epidemiological evidence and selected case reports. American Journal of Industrial Medicine, 17(2): 189-214.
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open-air facility to suck in secondary emissions. The larger the storage capacity of canopy hood systems, the greater their effectiveness in keeping secondary air pollution out of the atmosphere.
However, these systems can be costly and consume power. A doghouse, or furnace enclosure, is a larger structure built over and mostly enclosing the furnace area inside a partially open-air facility. Doghouses passively direct fumes out a single opening to the filters and may also help to reduce noise emissions. A particularly large doghouse can capture emissions from charging as well. Finally, total building evacuation is possible when an EAF facility is totally sealed and fumes are collected from an opening in the roof area before they are filtered and released into the atmosphere. The European Commission recommends total building evacuation to capture the most comprehensive spectrum of emissions, especially those containing harmful PCDD/F.
Figure 3 depicts the three main systems of air pollution collection.
Figure 3: Three air pollution collection systems
Source: European Commissions BAT guidelines adopted 2012
After emissions captivation through one of the systems above, gases undergo filtration, also referred to as purification or abatement. Purification happens when the offending particulate components of emissions are removed either through a wet process using high-energy scrubbers (that entrain particles in wastewater and remove them as sedimentation), a semi-wet process that applies water to off-gasses before filtering them through expensive electrostatic precipitators (machines that negatively charge particles in the air and magnetically attract them to metal plates) or a “dry” method using bag filters made of specially engineered textiles. Relatively low-tech bag filters are used in most EAF facilities around the world, although they are limited by their intolerance to very high temperatures. For this reason, the ducts that connect the gas inputs to the purification system are often cooled by dilution with air or with circulating water.
Importantly, filtration removes most of the heavy metals from industrial off-gas with the exception of mercury, which cannot be eliminated by filtration or electrostatic precipitation. A
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benefit of this popular dry method of pollution control is that it produces no wastewater in need of further treatment.
The extraction of useful heavy metals from collected EAF waste powder occurs thanks to advanced techniques using specialized heat-based processes (pyrometallurgical methods) and chemical solutions (hydrometallurgical methods). According to Boyanov and Baev (2009), zinc is the heavy metal most commonly extracted from EAF powders because zinc-coated galvanized steel is the most common form of scrap metal fed to EAF furnaces. However, the high amounts of halogen (nonmetallic elements that bind with hydrogen to form acids) in the powder can interfere with the extraction of zinc and other useful heavy metals.
One heat-based method of EAF powder refining and heavy metals extraction described in Boyanov and Baev begins with placing the powder in a specialized furnace and heating the mixture to 1200 degrees Celsius, which turns 95% of the chlorine and 59% of the fluorine into a gaseous substance. The Taiwan Steel Union in 1996 began implementing a Waelz Kiln
procedure to process 50,000 tons each year of EAF dust to extract zinc oxides (Cheng, 2003).
Finally, zinc may be leached through “washing” using a solution of water and Na2CO3
(molecules of sodium carbonate). Washing allows over 75% of the chlorine and less than 20% of the flourine to dissolve into the solution. Some technicians also recommend a preliminary stage of isolating some elements via magnetic separation.
In addition, EAF powders can also be reconstituted in other useful products such as glass-ceramics for use as building materials, road surfacing or refractory materials. With respect to slag, Taiwanese law states that it can be either deposited into specialized industry-use landfills or turned into road pavement. In the right proportions and using the appropriate methods, these waste products can enhance the strength and/or functionality of the recycled end product. Cheng (2003) stresses that EAF dust recycling is “critical” to efforts for cleaner disposal of the
approximately 24,000 tons per year of powder produced by stainless steel facilities in Taiwan, especially since, as a hazardous waste, it cannot be thrown into the nation’s landfills due to concerns over the leaching of heavy metals into soil and groundwater.
In short, while the extraction and/or reuse of useful materials from waste powders is beneficial for the environment and possibly the bottom line of the company that can sell the waste product, companies require either technical specialists to do the job in-house, or else enough capital to spend on getting an outside company to complete the job. A small enterprise
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might lack the resources to get the job done, as was the case in Taiwan until recently.
A 2012 audit, jointly undertaken by the Taiwan Environmental Protection Administration (EPA) and the Industrial Development Bureau (IDB) and published on the EPA website13, summarizes the huge environmental impact of EAF powder disposal in Taiwan. Every year the industry generates between 180 and 220 thousand metric tons of hazardous dust. As most EAF facilities are not equipped with on-site treatment operations, this industrial waste accumulates in storage containers with slag. Unfortunately, because of a general shortage in recycling and treatment centers catering to EAF refuse, the dust from EAF facilities, when aggregated, had totaled over 500,000 tons before help arrived. The EPA and IDB established four new high-capacity treatment facilities in three factories to gradually reduce the buildup and take care of future waste treatment needs.
Lastly, Chou and Fang (2005) highlight the worrisome environmental impact of improper waste disposal in the face of natural disasters. Their research monitored two million tons of steel slag deposited along the coastline in Southern Taiwan between 1984 and 1989, turning the seabed in that area to a mixture of sand and slag (a heavy-metal containing residue from steel production that’s more gravel-like in contrast to EAF powder). Starting from 1990-1995, scientists measured relatively little change to the biological content on the seafloor at the dump site (notably, the site was not monitored during the early years of dumping), but this low-level impact changed gradually with a steady downward trend in crustacean populations ignited by Typhoon Gloria, which struck the study site in July 1996. Thus, in disturbing unstable
collections of stored or dumped industrial waste, natural disasters can exacerbate the initial environmental damage from steel slag and powders. Surprisingly, however, the same group of scientists determined that slag disposal along the coast had positive impacts on communities of fish because it added to the complexity of their habit, providing more total surface area and small hollow areas for lifecycle activities. Notably, these studies mainly counted populations of species and did not take into account the impact of bioaccumulating heavy metals in the health of
animals.
Typhoon Morakot in 2009 also caused disturbances for furnace slag waste disposal in Tainan. This powerful storm hit Chao Hsiang recycling center, leaving some steel waste exposed, and subsequent flooding transferred the waste into the surrounding environment. An
13 http://epq.epa.gov.tw/project/projectcp.aspx?proj_id=1012145674
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EPA deputy minister confirmed that the spill was likely behind chromium levels testing almost three times higher than the legal limit in the rice-producing areas of Houbi (後壁) Township, Tainan.14
The next major environmental issues involve air pollution and concerns over greenhouse gas emissions, two issues that go hand in hand. The gases that predominantly comprise EAF
emissions include the two greenhouse gases carbon monoxide and carbon dioxide as well as sodium oxides and nitrogen oxides (Ioana & Balescu, 2009). In addition, production emits organic matter such as volatile organic compounds, chlorobenzenes, polychlorinated biphenyls, polycyclic aromatic hydrocarbons and polychlorinated dibenzo-p-dioxins and furans. The exact composition of polluting emissions depends on four things: the composition of the scrap metal, management of the melting stage, the refining process, and the length of time required for melting and refining a particular grade of steel. Since these emissions intermingle with the powders detailed in the waste management section, their capture/captivation and filtration process is nearly identical.
Although carbon is an important alloying component that increases the hardness and strength of steel, this element must be managed and often reduced from the molten metal
mixture. This happens through oxidation, especially via a direct injection system of pure oxygen that combines with the carbon to form carbon dioxide (CO2) and carbon monoxide (CO). Other than these molecules’ significance as greenhouse gases in man-made climate change, CO can also have a direct impact on circulatory system efficiency in people and organisms exposed to the gas, even killing living things by inducing a state of hypoxia (reducing the oxygen carrying capacity of red blood cells) through carbon monoxide poisoning. Although there is little if any lethal risk from these greenhouse gas emissions in EAF plants, even in facilities supplementing their electrical energy with chemical energy via fossil fuel combustion, the inevitability of creating these climate-changing off-gases using current technologies and management
techniques highlights the importance of continual innovation and technological improvement.
Like carbon, sulfur may be considered an impurity in melted steel and excess amounts must be burned away by injecting pure oxygen into the molten metal. An unintended side effect of oxygenation is the creation of sulfur oxides, which impact the environment by dissolving into
14 Chao, V. (2009). Another case of slag contamination found in Tainan. Taipei Times (Nov. 17, 2009)
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atmospheric water vapor and forming photochemical smog and acid rain — industrial byproducts that harm human respiratory health and threaten human infrastructure (by gradually dissolving stone structures) as well as acidify fragile ecosystems and hinder the ability of plants to
photosynthesize. The relatively fewer impurities in scrap material versus iron ore makes EAF facilities relatively minor players regarding SOx emissions in the steelmaking industry; also, their mostly electricity-based power needs tends to reduce overall emissions from fossil fuel combustion. This will be explained in more detail with respect to nitrogen oxides.
Nitrogen oxides (NOx) come in three different forms with respect to steel production:
nitric oxide (NO) nitrogen dioxide (NO2), and nitrous oxide (N2O). NO is by far the most prevalent of the three in EAF steelmaking, comprising as much as 90% of total nitrogen oxide emissions (Chan et al., 2003). These pollutants, together with SOx, are key components of smog and acid rain. The majority of NOx emissions in EAF facilities comes from the high-temperature oxidation of atmospheric nitrogen that gets pulled into the furnace through various openings (especially the passageway for removing slag). Nitrogen may also contaminate the oxygen supply of direct injection equipment, entering the hot furnace this way. Chan et al. (2003) states that the best techniques for nitrogen oxide abatement in steel production involve reducing the levels of nitrogen and oxygen in the furnace, by sealing the furnace and/or purifying the oxygen injection supply.
Other than high-temperature oxidation, two other chemical processes typically result in high industrial NOx emissions and both relate to the burning of fossil fuels. Most EAF facilities worldwide are powered principally from a three-phase utility-based generator, which means that they defer most of their fuel-related NOx production to power companies. However, many EAF furnaces supplement their electrode-based melting unit with oxygen-fueled burners, powered by natural gas. Natural gas combustion does form nitrogen oxides, although its advocates emphasize that it produces fewer overall emissions than the combustion of other fossil fuels like oil and coal.15 In fact natural gas, composed mostly of methane, mostly releases carbon dioxide and water during combustion, but environmentalists often point to the gas-harvesting process of hydraulic fracturing (or “fracking”) as the most worrisome aspect of this substance. Fracking uses pressurized, chemically treated water to break through rock deposits deep beneath the soil and release the odorless gas. This process releases methane — a much more powerful GHG than
15 See http://naturalgas.org/environment/naturalgas/
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carbon dioxide — into the atmosphere, while the chemically treated water can severely pollute groundwater and render valuable freshwater reserves unfit for human consumption.
Also of concern, volatile organic compounds (VOCs) result when “organic” carbon-based substances like solvents and paints are charged to the furnace. Since VOCs have a very low boiling point, they easily convert from a liquid or solid form to a gas. In the environment, VOCs
Also of concern, volatile organic compounds (VOCs) result when “organic” carbon-based substances like solvents and paints are charged to the furnace. Since VOCs have a very low boiling point, they easily convert from a liquid or solid form to a gas. In the environment, VOCs