Steelmaking is an incredibly dirty business. Each tonne produced produces about 2 tonnes of carbon dioxide. Because the industry produces about 2 billion tons of steel each year, that’s a lot of CO2 that enters the atmosphere – in fact, about 7% of all global emissions. This makes finding ways to make green steel vital to controlling global warming.
The problem is that the traditional way of steel production – heating iron in a blast furnace – has existed for centuries. It uses a lot of energy both to heat the contents inside the furnace and to convert the coal into coke, which then reacts with the iron ore and converts it into pig iron ingots. Part of that energy comes from electricity, but much of it comes from the combustion of methane, which is often mistakenly referred to as “natural gas”.
ArcelorMittal is one of the largest steel producers in the world. It is trying to reduce carbon emissions from steel production by replacing green hydrogen with coke. This eliminates significant emissions from coke production, but still requires huge amounts of electricity for the rest of the process.
RWE, one of Germany’s largest electricity producers, and ArcelorMittal signed a memorandum of understanding this week. Under the agreement, they will work together to develop, build and operate offshore wind farms and hydrogen plants that will supply the renewable energy and green hydrogen needed to produce low-emission steel in Germany. The plan is to replace coal with wind energy and green hydrogen as the main source of energy in steel production at ArcelorMittal’s steel plants in Germany.
Reiner Blaschek, CEO of ArcelorMittal Germany, says: “ArcelorMittal Germany is embarking on a radical transition to ensure that our CO2 reduction targets are met, which means that the energy used to produce steel will have to be clean energy. The partnership we announced today with RWE is significant for several reasons. it will provide us with the renewable, affordable electricity and green hydrogen we need to produce low-emission steels while remaining competitive in the global marketplace. It also offers vital security in the supply chain, integrating energy and hydrogen supply into our business. ” New offshore wind farms will be located in the North Sea.
Boston Metal skips the step of green hydrogen
Boston Metal is a spinoff of MIT located in Woburn, Massachusetts. Unlike most steelmakers, it wants to skip the green hydrogen step and move directly to carbon-free steel production using what it calls the molten oxide electrolysis process, which uses electricity to separate oxygen from iron ore, a critical step in the steelmaking process. “The advantage we have is that it’s a one-step process that directly electrifies steel production,” says Adam Rauwerdink, vice president of business development for Boston Metal. Canary Media.
“You don’t realize when you look at your landscape how embedded and rooted it is [steel] is in society, ”said Chathurika Gamage, Climate Intelligence Manager at the nonprofit research organization RMI. “Everything we do, the buildings we are in – it provides structural stability, literally, to all these spaces.”
“The decarbonisation of the iron and steel industry basically means the decarbonization of the blast furnace,” says Zhiyuan Fan, a research associate at the Center for Global Energy Policy at Columbia University. “If you solve the blast furnace [issue]half of your problem is gone. ”
A fan team in Colombia published a study last year comparing several strategies for decarbonizing steel and found that electrification is the key to reversing emissions. The more the process can use clean electricity instead of burning coal and other fossil fuels, the easier it will be to reduce emissions. “We know how to decarbonize the grid better than we know how to decarbonize the blast furnace,” adds Fan.
“Ten or 20 years ago the mesh wasn’t clean, so it didn’t make any sense and there was no demand for a greener version of steel, but now both are available,” Rauwerdink says.
Reducing the cost of making steel
Doing something in the lab is very nice, but being able to expand the technology to produce millions of tons of green steel is something else entirely. Boston Metal thinks it has the answer.
Electrolysis has been a key part of aluminum production for more than 100 years. Boston Metal’s molten oxide electrolysis process applies this technique to iron, which requires higher temperatures. Electrolysis of aluminum takes place at temperatures just below 1,000 degrees Celsius, while electrolysis of iron requires about 1,600 ° C, which is a temperature far warmer than molten lava.
For starters, iron ore is melted by heat produced from electricity. It is then placed in a cell structured almost like a giant battery. At the top, the anode provides an electric charge. It receives an electric charge at the bottom of the cathode. In between, the charge flows through the electrolyte, which in this case is a bath for burns of molten material. The electrolyte contains various elements related to oxygen, including aluminum, silicon and calcium.
According to Boston Metal, the process works even with low-quality iron ore, which is cheaper and more abundant than higher-quality ore, which has less impurities. “Some other technologies that are evolving [to manufacture] green steel needs super-premium grades of ore, ”says Rauwerdink. “We can take advantage of all the richer types of ores, which is key to the development of technology in the long run.”
Another advantage of electrolysis of molten oxide compared to direct reduction of iron is its efficiency. By abolishing the hydrogen step, MOE puts energy directly into steel production, eliminating temporary phases in which energy can be lost. MOE requires higher temperatures than hydrogen-based production, which eats to its advantage, but even if this is taken into account, MOE still becomes more efficient.
Fan, a green steel expert in Colombia, estimates that making green steel using green hydrogen requires at least 30% more energy than MOE – and maybe even 50% to 60% more. “By skipping these different processes, you can actually achieve many efficiency improvements,” he says.
The road to scale
A commercial factory can produce several million tons of steel a year. Working continuously, Boston Metal’s first demonstration cell will produce less than 100 tons of steel a year, so the company has a long way to go. “It’s just about aggregating those cells, and the proof is in the pudding how much that can increase,” said Gamage of RMI.
Volume is important in the steel business, but so is the ability to use capital-intensive systems that have already been built. Green hydrogen has an advantage on this front because it is compatible with the process of direct reduction of iron, which is already used on a commercial scale with natural gas. It is relatively easy to replace natural gas with hydrogen. That’s why large steelmakers like SSAB and ArcelorMittal have focused on green hydrogen for their short-term plans.
“We’re in class here,” Fan said. “If we want to fully decarbonise by 2050, we need to think about replacing production units in the next 10 or 20 years. If the MOE was not commercially available at the time, it simply missed the window. ”
Boston Metal is working on a larger demonstration cell at its headquarters in Woburn, Massachusetts, which will be able to produce several hundred tons of steel a year. Once the design is perfected, multiple cells can be built in the same plant and then potentially lined up by the hundreds, which is common in aluminum smelters.
“Because it’s a modular technology, the path to scaling will be pretty fast,” Rauwerdink says. “It’s like having a wind turbine and demonstrating five turbines, and then when it’s successful, building 100 or 200 for a commercial plant. It is the same approach for us. Then we don’t have to go back and redesign a cell that is 100 times bigger. “
The need for electricity without emissions
Boston Metal technology will need electricity produced from low-carbon sources to reduce carbon emissions in steel production. “The future of steel production really depends on clean electrification,” Gamage said.
Steel production equipment tends to be in constant operation for months, and changing the chemical composition of the metal itself requires a lot of energy, so if the process is electrified, a huge amount of electricity will be needed. Boston Metal says its technology uses 4 megawatt-hours of electricity to produce 1 ton of steel. That’s enough to power the average U.S. home for more than four months.
According to Columbia’s steel decarbonisation research, replacing all of the world’s blast furnaces with MOE production processes would require an amount equivalent to nearly 20% of global electricity consumption in 2018. That means the steel industry would become one of the largest electricity consumers on the planet.
But replacing all steel production with direct reduction of iron to hydrogen could require even more electricity. This means that there is no way to address the climate impacts of steel without installing a huge amount of clean electricity production, while ensuring that the grid is ready for reliable movement of all that extra electricity.
“You’re going to have to boost your network at speeds not planned by utilities and network operators,” said Thomas Koch Blank, senior director of RMI’s breakthrough technology program. And that should be done on a “program of 10 to 15 years.”
The development of new decarbonisation technology is sometimes seen as at odds with the application of established solutions such as renewable energy, but in many circumstances these challenges are one and the same. Green steel is a great example.
“For us or for green hydrogen, you will need clean energy,” Rauwerdink said, “so all the work that goes on cleaning the grid allows for solutions like ours.”
As demand for green steel grows, multiple solutions will be needed to satisfy the world’s appetite for steel without overloading the atmosphere or electricity grid. Koch Blank emphasizes that both electrolysis of molten oxide and direct reduction of iron to hydrogen promise to decarbonize the steel industry and are worth pursuing. “After all, I would be surprised if there is not enough space on the market for both technologies,” he said.
Green hydrogen has been getting a lot of attention in the press lately because it promises ways to significantly reduce carbon emissions from industrial processes such as steel and cement production. But it depends entirely on access to clean, reliable and affordable electricity. The path to zero-emission building materials is clear, but achieving this will require a significant rethinking of renewable energy and the way it is distributed in the electricity grid in each country.
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