Steel and sustainability: new ideas, better solutions
We need buildings, highways, vehicles, and appliances. They contribute to our comfort, security, and our robust, developed economy. But producing them is also responsible for much pollution and damage to the environment. Manufacturing industries are leading consumers of energy, as well as emitters of carbon-based greenhouse gases.
The steel industry—one of the largest industrial sectors—has been under a lot of pressure recently to reduce emissions and its reliance on coal and coke. The entire industry has been working to overcome this problem, finding new and better ways to reduce emissions, one idea at a time. Four new ideas are electrolysis of iron ore; dry slag atomization; improving blast furnaces with plasma torches; and converting steel plant carbon-monoxide streams into ethanol.
ULCOS: Hlsarna and electrolysis. The Ultra-Low Carbon Dioxide Steelmaking (ULCOS) group is a European consortium of steelmakers and partners aiming to reduce steelmaking CO2 emissions by 50 percent of today’s numbers. To achieve this, they are working on various projects, such as a new ironmaking process, HIsarna.
HIsarna uses a technology based on bath-smelting. It is a combination of coal preheating, partial pyrolysis in a reactor, a melting cyclone to melt ore, and a smelter vessel for final ore reduction and iron production. With the ability to smelt fine iron ores without a pellet or sinter plant, Hlsarna has the potential to achieve very low coal rates through the partial use of alternative fuels, like biomass of natural gas or hydrogen.
ULCOS is also working on the electrolysis of iron ore, something that’s never been done industrially before. This could be a real gamechanger for the industry—green electricity from nuclear, solar, or wind used in an electrolytic circuit to produce pure iron. Carbon-dioxide emissions from the mining and steelmaking route would be only a tiny fraction of today’s values. Unfortunately, this advancement is anywhere from 20 to 50 years away from major industrial implementation. But if it were successful, it would vastly change the world we live in for the better.
Dry slag atomization. Recovering energy from metallurgical slags has often been discussed and studied, but little industrial progress has been made. Ecomaister and Hatch have partnered in the development and implementation of dry slag atomization for the metals industry. A high-volume jet of air directly turns slag into hard spheres, eliminating the need for a hazardous slag yard.
The process uses no water, so issues like scarcity, freezing, explosions, and liquid waste can be avoided. From a CO2 perspective, the best feature of dry slag atomization is its ability to recover a stream of hot air that can be used for power or steam generation. The best candidates for heat recovery are those plants that tap slags continuously or semi-continuously.
Plasma for superheated blast furnace blast air. A blast furnace is a very efficient way to make liquid iron. Unfortunately, most of the energy for reduction comes from coal-based sources. Hatch and Alter NRG have been working to improve on an old idea. During the 1980s, work conducted on electrically based plasma torches to superheat blast furnace hot-blast air was halted due to concerns over torch and refractory reliability. Today, plasma torch and refractory reliability has improved, which makes this old idea a new possibility. Carbon-dioxide emissions are reduced when green electricity substitutes for carbon-based energy in the blast furnace.
From carbon monoxide to ethanol. LanzaTech is trying to change the way carbon is perceived. It’s converting carbon wastes, like steel plants’ carbon-monoxide streams, into ethanol using microbes. These micro-organisms use carbon gases as their primary source of energy for life and product synthesis. The direct conversion of steel plant wastes into useful byproducts, without combustion, is an efficient use of energy streams. With a number of pilot and demonstration plants already in operation, this biotechnology is well on its way to contribute to the environmental sustainability of the steel industry.
Reducing emissions and reliance on coal and coke will help create a better environment for us today and generations to come. Finding alternative fuels and better ways to use those we have now will help us achieve this goal. So will opening our minds to new possibilities. We may be years away from implementing some of these technologies in industry, but we’re moving steadily in the right direction.