Steel Sector: Towards Green Sustainability

Steel is at the core of a green economy, in which economic growth and environmental responsibility work hand in hand. The steel industry believes that sustainable development must meet the needs of the present without compromising the ability of future generations to meet their own needs. Within this, a green economy delivers prosperity for all nations, wealthy and poor alike, while preserving and enhancing the planet’s resources.

Steel is essential to the technologies and solutions that meet society’s everyday needs – now and in the future. Steel is central to our current transport systems, infrastructure, housing, manufacturing, agriculture, water and energy supply. It is also critical to the sectors and technologies that will enable and drive a green economy.

Renewable energy, resource-efficient and energy efficient buildings and low carbon transport, infrastructure for fuel efficient and clean energy vehicles – all these depend on steel. In addition, many of the challenges posed by population growth, urbanization, poverty reduction and mitigation of natural disasters can best be met by steel.

Steel’s two key components are iron – one of Earth’s most abundant elements – and recycled steel. Once steel is produced it becomes a permanent resource because it is 100% recyclable without loss of quality and has a potentially endless life cycle. Its combination of strength, recyclability, availability, versatility and affordability makes steel unique. Steel is the most recycled industrial material in the world, with about 600 MT recycled annually, globally. Recycling accounts for significant energy and raw material savings: ~1,400 kg of iron ore, ~740 kg of coal, and ~120 kg of limestone are saved for every tonne of steel scrap made into new steel.

Recycling is especially important in a green economy because it conserves valuable resources and prevents useful materials going to landfill sites as waste. There are two main sources of recycled steel, also called steel scrap: excess material from steel production and downstream manufacturing (pre-consumer scrap), and steel at the end of a product’s life (post-consumer scrap).

All industries cause environmental pollution in some way or the other. Steel industry is no exception to the fact. Steel manufacturing has a variety of impacts on the environment. The main impacts come from the use of energy and raw materials, which result in emissions such as carbon dioxide (CO2), sulphur oxides (SOx), nitrogen oxides (NOx), dust to air as well as water usage and associated emissions.

Globally, more than 60% of the DRI (sponge iron) production is through natural gas, with coal only contributing to 20% of the production. It is also one of the cleaner routes for steel making. Blast Furnace (BF) iron using a carbon source such as coal or coke to generate metallic iron produces CO2 as a byproduct. On the other hand, Natural Gas fueled Direct Reduction plants (DR Plants) make metallic iron by using hydrogen molecules to remove 2/3rd of the oxygen atoms and carbon to remove the remainder. Accordingly, the generation of CO2 is reduced by 68% in DR plants as compared to standard BF iron making. Coupled with an EAF, a DRI plant can reduce CO2 emission significantly, particularly compared to integrated blast furnace/BOF steelmaking. Natural gas, rather than coal or coke oven gas, as a supplemental fuel reduces NOx, SOx and CO2 emissions and allows productivity increase. It is also used as a fuel in reheating furnaces in pellet plants, mills, Ferro Chrome plants, in other agglomeration units like briquette and sinter plants, and even in boilers for raising steam.

Green Hydrogen, ie hydrogen produced from renewable energy has the potential to reduce and replace the demand for fossil fuels, so as to cut greenhouse gas emissions and enhance the sector’s credibility in terms of decarbonization commitments. Research in this direction is on, and various initiatives are being taken by steel producers world-wide.

Transportation of raw materials and finished goods through inland waterways and coastal shipping is also being promoted. In studies comparing rail, truck, and water, shallow-draft water transportation has been proven to be the most energy efficient method of freight transportation for moving bulk raw materials. This mode of transportation is also extremely safe, causing little to no congestion and produce very little air/noise pollution.

Another mode, the slurry pipeline is intended for transportation of iron ore fines after its conversion to iron ore concentrate in slurry form. At present transportation of iron ore lump and fines to iron making units and ports is being mostly done through railways from their respective linked sources. With the steady growth of steel industry there is a tremendous pressure on railway with respect to transportation and evacuation of iron ore lump and fines. To have an alternative to dependency of transporting fines by railways and to reduce the environmental concerns, the advantages of transportation of iron-ore fines by a network of slurry pipelines to pellet plant clusters are well accepted.

Mining of minerals impacts natural resources like land, water, air and forests, hence it is necessary to take a comprehensive view to facilitate the order of land use as per the need of development as well as the need of protecting the forests, environment and ecology. All mining should be undertaken within the parameters of a comprehensive Sustainable Development Framework which will ensure that environmental, economic and social considerations are integrated effectively in all decisions on mines and minerals issues. The guiding principle should be to leave the mining area in an ecological shape which is as good as it was before the commencement of mining or better. Once the process of extraction of a mine is complete, there is a need for scientific mine closure which will not only restore ecology and regenerate bio mass, but also take into account the socio-economic aspects of such closure.

Developments in clean coal technologies have opened new avenues for utilization of coal. The end products of these technologies can provide feedstock for various downstream processes such as chemicals and fertilizers and could also potentially partially replace the well-established sources of energy such as LPG, gasoline and diesel in various applications. Production of syngas is at the core of coal to chemicals process. Syngas can be used to produce methanol, ammonia, dimethyl ether, synthetic natural gas and many other products. Syn gas can be used as a replacement of natural gas in steel production.

The steel industry is moving towards zero waste generation. Steel industry produces waste heat and gas at different stages of steelmaking, which can be recovered to generate power. Blast Furnace gas emitting from the top of the blast furnace has high pressure, which can be routed through a turbine – generator which converts the pressure energy into electric energy.

In a steel plant, the Coke is produced in Coke Ovens for use in iron making. The Coke produced in the Coke Ovens has a temperature of more than 1000degC. In conventional Coke Ovens system, this Coke is cooled to normal temperature by spraying water which evaporates as steam into the atmosphere. In Coke Dry Quenching (CDQ) process, the coke is cooled by passing gas through the coke in a closed chamber. This gas picks up the heat from the coke and becomes hot at the exit of the chamber. The hot gas is then passed through a boiler where it uses the heat for generating steam which in turn is used for generating power through a turbine-generator. Cooled gas is recirculated through the coke chamber.

In the process of Steel manufacturing in an integrated steel plant, waste gases are generated, namely coke oven gas (COG) and Blast furnace gas (BFG) and LD gas (LDG). These gases have significant calorific value. The gases are used as fuel for burning in boilers which produces steam for power generation, as well as process steam.

Iron & Steel Industry generates basically two types of slag namely, Blast Furnace (BF) slag and Steel Melting Shop (SMS) slag such as LD slag, EAF slag and IF slag. In the steel industry, 1 ton of hot metal production generates 0.33 ton of Slag as a by-product. As a result, there are huge stocks of slag lying with many of the steel plants. This slag is often used along with fly ash by cement industry as a replacement for clinker. Substituting clinker with Granulated Blast Furnace Slag (GBFS) allows significant reductions in CO2 emissions. It can also be used as a replacement for river sand, thereby avoiding stone crushing and exploitation of river sand and mountains.

In the backdrop of the aforesaid, it is evident that the Steel Sector is inherently oriented towards being an environment friendly industry, with a leaning towards green sustainability. Emerging environment friendly technologies will lend further credence to the sector. However, only the various stakeholders can ensure that the steel industry remains committed towards the same, so that it is a win-win perspective for one and all, with value creation for the benefit of all.

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(views are personal, and the author acknowledges technical inputs from Mr Deepak Sethia, former PwC, currently with Vedanta Limited)