The steelmaking process with an electric arc furnace

-global issues (especially global warming) -resource and energy conservation -waste control

This section will explore each of the aforementioned parameters of environmental governance in turn, starting with an in-depth explanation of steel production in an EAF facility.

This information contextualizes environmental investment by positioning it within a paradigm of day-to-day operations and forecasts potential areas for improvement. Next, a detailed look at what is at stake for the industry (i.e., the environmental impacts of EAF) illuminates the broader context of private sector initiatives for EMS development. The final two subsections discuss political/regulatory and social influences on EAF operations. Later, the efficacy of multi-sector influence on actual Taiwanese firms’ EMS development will be explored in the results and discussion sections.

2.1 The steelmaking process with an electric arc furnace

Understanding in detail how EAF facilities produce steel makes it easier to grasp the inputs and outputs of the system and their environmental implications as well as the high level of expertise and capital required to make changes and improvements. As will be explored more thoroughly in the results section, cross-sector friction related to industrial upgrades (particularly when government regulators seek upgrades to older facilities) may result from or be exacerbated by company resentment over a perceived public sector failure to adequately measure the material constraints of an operation. The following section just skims the surface of the intricate industrial process of EAF steelmaking, implicitly drawing attention to the massive levels of sunk costs in particular technologies and existing methods of operation.

The process of producing steel with an electric arc furnace includes five complex phases:

raw material loading and furnace charging, melting and deslagging, refining and alloying, slag handling, and casting. More precisely, the slag handling stage is not strictly a part of the steel-making process, but is actually a waste management task of crucial importance during each production cycle. Figure 1 depicts this production cycle and highlights the stages at which pollution and waste are generated. Section 2.2 describes the production and treatment of emissions and waste in greater detail, including a breakdown of EAF’s solid and gaseous emissions and their respective impact on human and environmental health.

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Figure 1: EAF steel production and pollution/waste generation

First, scrap iron must be collected as a base material (sometimes after undergoing a pretreatment process). This scrap material is often called “ferrous scrap,” and can either

constitute trimmings and discarded pieces from industrial steel molding and production, or it can be end-of-life consumer goods and parts. Sometimes direct reduced iron, or “sponge iron” — pellets of iron ore that were subjected to a fossil fuel-derived gas — may be added at this initial stage as well as “ferroalloys,”⁵ which are concentrated nuggets of iron and some other desirable heavy metal like manganese, aluminum or silicon.

To bring about certain properties in the finished steel, the raw material must be mixed, or alloyed, with other elements at either (or both) the initial furnace loading stage or the

refining/alloying stage. For example, add chromium (a highly toxic chemical) to make steel resistant to oxidation (rusting) — an immensely important feature of many grades of steel used in infrastructure development and transportation and other uses in a variety of climates with strict strength and longevity demands. Add aluminum to remove oxygen from the melted steel and prevent steel “aging” when under strain, add carbon for hardness and strength and add

manganese to improve the mixture’s hot working properties^6฀. These preliminary additives can

5 The symbol for iron in the periodic table is Fe, which comes from the Latin root word for iron, ferrum.

6 See http://www.chasealloys.co.uk/steel/alloying-elements-in-steel/ for a list of common alloys and their properties.

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be collected along with the scrap material^7฀ with the help of magnets or a mechanical claw and placed into an enormous metal “basket,” also known as a charging box, which can be positioned above the kiln. The bottom of the basket will then open to allow the contents to pour into the melting area, “charging” the furnace (often with 50-60% of the prepared scrap at first, adding the rest after successive stages of melting).

Second, the scrap materials are melted by lowering a graphite (made almost entirely of carbon atoms) electrode or group of electrodes 200-300 millimeters above the scrap, suspended in the furnace. With a massive input of electricity, these electrodes conduct an electrical current that can vary between 42,000 and 50,000 amps⁸ (compare that to a major home appliance that registers about 60 amps at most), generating an ongoing, ultra-hot plasma discharge from the head of the electrode and connecting with the head of the electrode beside it to form an “arc,” or

“u” shape approaching 3,000 degrees Celsius (and also producing a persistent, very loud crackling noise during the early stages of melting). As the melting process continues, the

electrodes descend deeper into the scrap, often accompanied by an increase in power. To protect the furnace from radiation from the electrodes, many EAF firms simultaneously inject oxygen and carbon into the liquid metal at this stage, which in part transforms into carbon monoxide bubbles and a foam slag that also helps distribute the heat energy more efficiently as it shields the furnace walls from excessive damage⁹. The furnace itself is a refractory-lined vessel (coated with an alkaline material, like calcium oxide and magnesium oxide, with an extremely high melting point) that is typically equipped with water-cooled panels. The electrodes may also come equipped with a water-cooled system.

Before the heating process is fully complete, typically limestone and/or dolomite (a kind of

“flux,” to use the industry jargon) will be added to the mixture at temperatures around 1,600 degrees Celsius to produce slag, a waste product. Between 50 and 120 pounds (about 23-54 kilograms) per ton of steel is required. Lime is particularly adept at reducing the sulfur,

7 It is perhaps most common, however, to add ferroalloys later, during the refining stage, to minimize the amount of valuable additives lost during deslagging.

8 An amp, or ampere, is a measurement of the amount of electrical charge, i.e. the number of electrons, passing a particular point in a circuit within a specific time period, with 6.241 x 10¹⁸ electrons per second constituting one amp.

9 Injection of oxygen at this point has even more benefits such as thinning overall levels of carbon (decarburization) and removing sulfur and phosphorus.

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phosphorus and silica from the molten metal. Slag is the result of these undesirable components binding with the limestone/dolomite additive and rising to the top of the heated mixture. Slag not only minimizes impurities in steel, it can also form a kind of thermal blanket to minimize heat loss during melting. After a while, the top layer of undesirable slag is poured out when the furnace tilts to the side and/or it gets raked off the melted steel during “deslagging.” The creation and removal of different types of slag (designed to remove different undesirable elements) may happen several times depending on the grade and type of steel being produced. Importantly, the removal of slag into a pot or directly onto the ground below the furnace results in the production of dust and fumes, the latter of which is pulled into an exhaust system.

Third, the furnace tilts to pour the molten steel into a preheated container called a “ladle,”

where it is refined. Refining is a process of making a metal more pure (rather than changing its fundamental, chemical characteristics), for instance, by removing sulfur, phosphorus and excess carbon and/or dissolved gases like nitrogen and hydrogen from the molten steel. Steel refining alone can be conceptualized as a number of specialized steps — at different “ladle treatment stations” based on the technological and steel grade-specific capabilities of an EAF facility — and often involves the removal of oxygen in the latter stages, i.e. via a process of chemical deoxidation, adding fluxes and deslagging, or sometimes vacuum degassing. The refining stage is also a key point to add ferroalloys to enhance certain properties of the steel and further deplete its oxygen content chemically. Also, inert gases are injected into the ladle to stir the mixture and achieve an adequate level of homogenization, and ladle furnace equipment reheats the finished mixture to the appropriate temperature for casting.

Through successive stages of creating and removing slag, a process of slag handling and processing must be initiated to manage this kind of waste. If slag has been collected into a specialized pot, it must cool and solidify there (often with the help of water sprays). Some companies treat slag with silica, alumina and boron to make it easier to deal with. If slag was poured onto the floor, after it solidifies is must be crushed, collected and moved to a storage area with shovel loaders or excavator vehicles. Eventually this substance will be further crushed and processed and can be made into either material for construction (particularly road-building) or lime fertilizer. In Taiwan, independent off-site facilities must be contracted to handle slag treatment — except in the case of Dragon Steel, a China Steel subsidiary.

Finally, the liquid metal is evacuated from the ladle and casted (poured into molds and

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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.