To most CleanTechnica readers, perovskites are something used in solar panels to make electricity. Now it appears they may have other uses as well. Researchers at the University of Birmingham in the UK have recently published a report in the Journal of Cleaner Production with this catchy title: Cost effective decarbonisation of blast furnace – basic oxygen furnace steel production through thermochemical sector coupling.
Before we dig into that report, what are perovskites exactly? To find out, I went into the basement here at CleanTechnica world headquarters where we keep important stuff like menus for the executive dining room from 2006, and found an article written by my colleague Tina Casey in 2015 in which she offered this insight.
“Perovskites refer to a class of earth-hued minerals first discovered in the 19th century in the Ural Mountains by Gustav Rose and named after the Russian mineralogist Lev Perovsky, which accounts for the Russian sounding name. They are easily synthesized and their distinctive crystalline structure makes them a perfect match for the development of efficient solar cells.”
While cheaper than silicon (that’s good), they also tend to degrade easily, which means they don’t last very long (that’s bad). Over the past 7 years, however, researchers have made perovskites more stable and more efficient. For some applications, they may now actually outperform silicon-based solar panels. Now back to your regular programming, already in progress.
Perovskites & Blast Furnaces
The scientists at the University of Birmingham, in collaboration with scientists at the University of Science and Technology in Beijing, have discovered that perovskites may have another important use — removing carbon dioxide emissions from mills that use blast furnaces to make steel. Here is the abstract of the study.
“We present here a first-principles study of the sector coupling between a thermochemical carbon dioxide (CO2) splitting cycle and existing blast furnace – basic oxygen furnace (BF-BOF) steel making for cost-effective decarbonisation. A double perovskite, Ba2Ca0.66Nb0.34FeO6, is proposed for the thermochemical splitting of CO2, a viable candidate due to its low reaction temperatures, high carbon monoxide (CO) yields, and 100% selectivity towards CO.
“The CO produced by the TC cycle replaces expensive metallurgical coke for the reduction of iron ore to metallic iron in the blast furnace (BF). The CO2 produced from the BF is used in the TC cycle to produce more CO, therefore creating a closed carbon loop, allowing for the decoupling of steel production from greenhouse gas emissions.
“Techno-economic analysis of the implementation of this system in UK BF-BOFs could reduce steel sector emissions by 88% while increasing the cost-competitiveness of UK steel on the global market through cost reduction. After five years, this system would save the UK steel industry £1.28 billion while reducing UK-wide emissions by 2.9%. Implementation of this system in the world’s BF-BOFs could allow the steel sector to decarbonise in line with the Paris Climate Agreement to limit warming to 1.5 °C.”
Devised by professor Yulong Ding and Dr. Harriet Kildahl from the University of Birmingham’s School of Chemical Engineering, the system could deliver major cost savings while reducing overall emissions. Ding tells Perovskite-Info, “Current proposals for decarbonizing the steel sector rely on phasing out existing plants and introducing electric arc furnaces powered by renewable electricity. However, an electric arc furnace plant can cost over £1 billion to build, which makes this switch economically unfeasible in the time remaining to meet the Paris Climate Agreement. The system we are proposing can be retrofitted to existing plants, which reduces the risk of stranded assets, and both the reduction in CO2, and the cost savings, are seen immediately.”
Under a high concentration of CO2, the perovskite splits CO2 into oxygen, which is absorbed into the lattice, and CO, which is fed back into the blast furnace. The perovskite can be regenerated to its original form in a chemical reaction that takes place in a low oxygen environment. The oxygen produced can be used in the basic oxygen furnace to produce steel.
Cleaning Up Steel Making
The impetus for this research is that steelmaking accounts for about 9% of global carbon emissions. While there are proposals to transition to different technologies that use renewable energy to lower those emissions, the result is a need to replace existing steel mills with new ones — a costly and time consuming process. There are also those who favor carbon capture strategies, which the researchers, using the precise language of scientific reporting, expose as a giant crock of Grade A horse puckey. Seldom does technical writing contain such drollery, which makes it suitable for being reproduced in lightly edited form here.
The iron and steel sector is a major greenhouse gas emitter, releasing up to 9% of global CO2 emissions. Steel is firmly in the category of hard-to-decarbonize sectors due to the inherent carbon-intensive nature of its production. Indeed, more carbon dioxide is released on a weight basis than steel produced, with 1.89 tonnes of CO2 released for every ton of steel produced.
The main reason for this is the use of coking coal as an energy source and structural support, making up a 74% share of the total energy feedstock and accounting for 15% of the total global coal consumption. Nevertheless, the sector must achieve 54% or 90% emissions reduction by 2050 to limit warming to 2 °C and 1.5 °C, respectively. If the currently operational assets are run for their natural 40 year lifetimes, it would constitute entrenched emissions of 65 gigatons of carbon dioxide equivalents.
On an annual basis, the steel industry uses 2 billion tons of iron ore, a billion tons of metallurgical coal, and 575 million tons of recycled steel to produce 1.7 billion tons of crude steel. This requires 32 EJ of final energy.
There are currently two main methods of steel production — the blast furnace-basic oxygen furnace (BF-BOF) route accounting for 71% of production, and natural gas-based direct reduction of iron followed by an electric arc furnace (DRI-EAF) making up the other 29%. First, iron ore is reduced to metallic iron in the blast furnace or direct reduced iron before being converted to steel by reducing the carbon content in the metal in the basic oxygen furnace or electric arc furnace.
There are a few technologies that are being researched to decarbonize the steel industry. The first option is to close the old BF-BOFs and replace them with DRI-EAFs. If the EAF is powered by renewable electricity, it has the potential to save 1.5 Gt of CO2 emissions annually. However, a DRI-EAF plant costs between $1.1 and $1.7 billion to build, which combined with the stranded assets of the old BF-BOF plant, makes this switch economically unfeasible in the short time period needed to meet the Paris Climate Agreement.
A second option is to increase the scrap recycling rate. Steel is already one of the most recycled materials, with an 84% recycling rate in 2017. In 2019, 32% of all inputs were scrap. Scrap recycling results in a 90% reduction of CO2 emissions and 70% energy savings compared with virgin iron ore in a BF-BOF. Additionally, each tonne of scrap steel reused displaces 1400 kg of iron ore, 740 kg of coal and 120 kg of limestone. The proportion of scrap steel in the input can be up to 100% in an EAF while 20–25% is currently the maximum input for a BF-BOF. It is expected that the share of scrap in inputs could increase to 46% by 2050 and although this is not sufficient to decarbonize the sector alone, it could result in significant CO2 emissions reduction.
Another decarbonization option is to use hydrogen for the direct reduction of iron (HDRI), followed by EAF. If renewable electricity is used to power an electrolyzer to make green hydrogen, this could dramatically reduce emissions. However, this requires new DRI plants to be built to replace BF-BOFs and has a Technological Readiness Level (TRL) of 5–7, meaning the technology has been demonstrated but is not industrially operational. The TRL allows for consistent comparisons of the maturity of different technologies, with a scale of 1–9 where 9 is the most mature and has been proven in the operational environment.
It has been estimated that a carbon price of $67/tCO2eq would be needed to enable HDRI to produce steel at the same price as a traditional blast furnace, provided there is sufficient low cost renewable electricity. Additionally, reducing iron with hydrogen is less efficient at lower temperatures than carbon monoxide, with the reduction from Fe2O3 to Fe3O4 occurring more readily under CO.
Conversely, the reduction of Fe3O4 to Fe at higher temperatures occurs more readily under hydrogen. Modelling suggests that hydrogen-based DRI could reduce emissions in the EU steel industry by 35% at current grid emission levels while requiring 3.72 MWh per tonne of liquid steel produced. For reference, BF-BOF uses 3.48 MWh/t. The cost of hydrogen production remains prohibitive [emphasis added].
A related technology is a natural gas-powered DRI with carbon capture, use and storage (CCUS), which also has a TRL of 5–7. Although several methods of CCUS have been demonstrated and a few industrial CCUS facilities are operational, the cost is expected to be $100 per ton of CO2 for capture and $160 per ton for transport and storage by 2030, with costs falling moderately by 2050. Given the extremely high emissions from iron and steel facilities, large CCUS plants would be required but emissions reductions are estimated to be between 20 and 80%.
Finally, another proposed solution is iron ore electrolysis, which has a TRL of 6. This technique is already used on a large scale for the manufacture of aluminium, so the technology has been proven on an industrial scale. Optimization of the electrodes and electrolyte are needed for the efficient reduction of iron.
In summary, steel production accounts for 9% of global CO2 emissions and must be rapidly decarbonized to limit warming to 1.5 °C. 70% of existing iron and steel facilities rely on the extremely energy intensive and emission heavy BF-BOF route. Most of the current methods of decarbonising this sector rely on the phase-out of these BF-BOF plants and the implementation of lower carbon methods such as EAF and DRI plants. This will be extremely costly.
This paper proposes another way to decarbonize the sector, namely by coupling a thermochemical carbon monoxide plant with a BF-BOF facility creating a closed carbon loop to produce steel…..This paper aims to demonstrate the first principal calculations of coupling a thermochemical carbon dioxide splitting cycle with a steel production facility for cost-effective steel decarbonisation.
Now, I could be wrong, but that is some of the most in your face scientific reporting I have ever come across. Usually, such writing falls into the MEGO category that might be force fed to terrorists to induce them to reveal their secrets.
The upshot of this study is simply this: We have to drastically lower the carbon emissions and we need to do it soon. We know how to do this in a way that works and is cost effective. All these other ideas floating about sound very nice in the laboratory but they are not practical, real world solutions and cost way too much to be practical.
I can’t say I have ever enjoyed a scientific article quite so much as I did this one. This is good old fashioned “tell it like it is stuff.” Bravo!
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