In the future, we need to further reduce CO2 on a global scale, and technology development is key to meeting this need. In the long term, it will be essential to take drastic measures enabled by innovative technologies.
On the other hand, there are various technological issues to be addressed for realizing steelmaking using hydrogen. We will also address these issues.
Outline of Fundamental Blast Furnace – Basic Oxygen Furnace Method
(Source) Nippon Steel Carbon Neutral Vision 2050
https://www.nipponsteel.com/ir/library/pdf/20210330_ZC.pdf
CO2 Emissions from Each Process
- Of domestic CO2 emissions, 15% is emitted from the steel industry.
- To realize carbon neutrality, it is important to reduce CO2 emissions from the ore reduction process.
Breakdown of CO2 emissions from the steelmaking process (t-CO2/t-crude steel)
※図を拡大して見ることができます。
(Source) Revised from “Carbon Trust, International Carbon Flows—Steel (2011)”
Tackling CO2 Reduction [1] (Hydrogen Reduction)
Issue
Carbon reduction is an exothermic reaction, while hydrogen reduction is an endothermic reaction and causes the temperature to drop. Hydrogen must be heated to increase the rate of hydrogen reduction.
|
Conventional blast furnace |
Hydrogen blast furnace and shaft furnace |
Heated gas
(Risk of explosion) |
Air
(No risk) |
Hydrogen
(Carries risk) |
| Blast volume |
Thousands of Nm3/min |
A massive amount of heated hydrogen needs to be injected in addition to the one on the left. |
| Heating method |
Hot stove
(Heat exchange with directly heated firebricks) |
Development of new technology, such as indirect heating, is required to ensure safety
(Heating efficiency needs
to be addressed.)
|
Technology to handle endothermic reactions is required
(Source) Nippon Steel Carbon Neutral Vision 2050 and others
https://www.nipponsteel.com/ir/library/pdf/20210330_ZC.pdf
Tackling CO2 Reduction [2](Expanded Use of Scraps and Reduced Iron)
- Quality constraints caused by copper in scraps and impurities, such as phosphorus, in reduced iron
- Quality constraints caused by the nitrogen contamination
The steel grades manufactured in electric arc furnaces are limited due to these two factors. In particular, it is difficult to manufacture high-grade steel with low-grade raw materials.
Revised from the “23rd research presentation of the Japan Society of Material Cycles and Waste Management (2012) 23_269” by Takehito Hiraki, et al.
Revised from the “Assessment of the Impact of Rising Levels of Residuals in Scraps, Proceedings of the Iron & Steel Technology Conference (2019)” by Jones, A.J.T.
Manufacturing high-grade steel in the EAF process by establishing the technology
to make entrapped elements that are harmful to material quality harmless
(Source) Nippon Steel Carbon Neutral Vision 2050 and others
https://www.nipponsteel.com/ir/library/pdf/20210330_ZC.pdf
Importance of Parallel Efforts
- All of the processes have advantages and problems in terms of achieving CN steelmaking. The technological development of several methods in parallel is needed.
| Advantages |
- Productivity is high.
- Existing facilities are usable.
- Low-grade ore is usable.
- High-grade steel can be produced.
|
|
- CO2 emissions are low.
- Carbon neutrality can be realized if 100% hydrogen reduction is possible.
|
| Problems |
- Coke needs to be replaced with carbon-neutral reducing agent (such as hydrogen and methane).
- The use of CCUS is indispensable.
- The temperature in the furnace becomes lower during hydrogen reduction. Measures are necessary (not established at present).
- Hydrogen cost is high.
|
- Productivity is low.
- Manufacturing of high-grade steel with low-grade materials is difficult.
- Iron sources are insufficient if only scraps are used.
- A carbon-neutral power source is required.
- Power cost is high (in Japan).
|
- It is difficult to use low-grade ore.
- The temperature in the furnace becomes lower during hydrogen reduction. Measures are necessary (not established at present).
- Hydrogen cost is high.
- The method requires high capital investment.
|
(Source) JFE Group Environmental Management Vision 2050
https://www.jfe-holdings.co.jp/investor/zaimu/g-data/jfe/2020/2020-environmental-management-vision210525-01.pdf
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