Kobe Steel, Ltd. (KOBELCO) has successfully demonstrated technology that can reduce CO2 emissions from blast furnace operations by approximately 20% by combining the Midrex’ HBI technologies and the blast furnace operations of Kobe Steel. The demonstration test was conducted for a month at a large blast furnace (4,844 m3) of the Kakogawa Works in Hyogo Prefecture, Japan, in October 2020.
The quantity of CO2 emissions from the blast furnace is determined by the reducing agent rate (RAR)—the coke rate (determined by the quantity of coke used in blast furnace) plus the pulverized coal rate (determined by the quantity of pulverized coal injected into blast furnace). Coke is carbon fuel made from coal. RAR is thus the quantity of carbon fuel used in blast furnace ironmaking.
In the demonstration test, it was verified that RAR could be stably reduced from 518 kg/tHM (ton of hot metal) to 415 kg/tHM by charging a large amount of hot briquetted iron (HBI) produced by the MIDREX Process. (Earlier post.)
Hot briquetted iron (HBI) is direct reduced iron (DRI) in a briquetted form. Since hot DRI is not suitable for long-distance transportation, it is pressed into a compact solid (briquette) upon being discharged from the reduction furnace.
Kobe Steel’s new solution is designed to optimize upstream and downstream processes to make the DRI process and overall operations even more efficient. This new method achieved the world’s lowest coke rate of 239 kg of coke per ton of hot metal—a 2.5x improvement over conventional methods using pre-reduced iron.
The reduction in the amount of coke used, however, makes it more difficult to maintain the stability of gas flows and the temperature of the molten iron within the blast furnace, which must be maintained at about 2,700 degrees Fahrenheit, with minimal fluctuations. AI technology is used to predict gas flows and the temperature of the molten iron. For example, the AI is designed to predict the molten iron temperature five hours into the future.
The results indicate that this technology can reduce CO2 emissions by approximately 20% compared to a conventional method.
CO2 reduction cost using this technology is calculated as follows:
((a)-(b)-(c)/ The quantity of CO2 reduced (d)) + Equipment cost + Other costs
where (a) is (the quantity of HBI charged × HBI unit price), (b) is (the quantity of iron ore reduced × iron ore unit price), and (c) is (the quantity of reductant reduced × reductant unit price).
The value of (c) equals (the quantity of coke reduced × coke unit price) + (the quantity of pulverized coal reduced × pulverized coal unit price). The quantity of CO2 reduced (d) equals (the quantity of reductant reduced × CO2 emission factor). Relative typical raw material unit prices are: HBI > coke > iron ore > pulverized coal.
Kobe Steel says it will keep improving this CO2 reduction solution technology while further reducing CO2 emissions and achieving lower costs for CO2 reduction.
Midrex Technologies, Inc. is Kobe Steel’s wholly owned subsidiary in the US. The MIDREX Process is the leading direct reduced iron (DRI) making process, which produces approximately 80% of the world’s direct reduced iron with natural gas (approximately 60% of the world’s direct reduced iron at large). The MIDREX Process uses natural gas as the reductant and pellets made of iron ore as the source of iron to make DRI through the reduction process in the shaft furnace. There are more than 90 MIDREX modules worldwide.