Natural gas based direct steelmaking using melt circulation: technoeconomic feasibility

Abstract

Steelmaking based on natural gas rather than coal is proposed as a logical solution to concerns about climate change and global warming. Highly preheated iron ore fines are fed onto the surface of the molten iron carrier medium in a single loop melt circulation reactor. A thin layer of liquid iron ore is formed and reduction occurs as the molten iron oxide containing melt is transported along the length of the reduction arm countercurrent to natural gas in situ generated reducing gases flowing at high velocity. Issues relating to Kelvin-Helmholtz instability are addressed and detailed consideration is given to soot formation and its subsequent gasification in the bulk gas phase. Key parameters for 1 Mtpa liquid steel are evaluated based on thermal decomposition of methane by convective heat transfer and reduction of ferrous oxide controlled by gaseous diffusion. A breakdown of capital and operating costs indicates the relative importance of key elements.

Towards Zero CO2 Continuous Steelmaking Directly from Ore

“…When this occurs, the immediate chemical reaction given by Eq. [2] converts the charge material containing iron in whatever oxidation state it was initially into a melt in which the iron is present essentially in the ferrous state. The liquid ferrous oxide containing melt floats on the molten iron carrier medium and is transported away from the charge location along with the principal flow of molten iron throughout the whole length of the reduction zone of a closed-loop melt circulation reactor.…”

“…[2], when a preheated charge of iron ore including fines is added to the top of a specially designed crushed ore contactor. When this occurs, the immediate chemical reaction given by Eq.…”

“…Primary attention should be focused on iron melts containing effectively no dissolved carbon. [1,2] To the author's knowledge, no attempt has ever been made to effect continuous steelmaking directly from iron ore employing an essentially carbon-free iron melt with small carbon addition at the very end of the continuous steelmaking process, if this is deemed necessary to meet steel product specification.…”

“…[3] The techno-economic feasibility of direct continuous steelmaking based on natural gas employing melt circulation within a singleclosed loop reactor has already been assessed. [2] A proposed melt circulation arrangement with hydrogen is to be seen as the ultimate solution to zero gas emission continuous steelmaking. According to the internet the world's fourth-largest steelmaker, which accounts for 10 pct of South Korea's carbon emissions, plans to switch to a hydrogen-based steelmaking process from 2021.…”

Generic melt circulation technology for metals recovery

“…On the other hand, naturalgas-based steelmaking using iron-ore fines eliminates the need for any decarburization whatsoever. 11 Refined molten iron is produced directly with carbon transfer to the melt prevented by a thin layer of molten iron oxide. Conventional oxygen steelmaking as such is eliminated and sub-surface nucleation and growth of CO is thus longer an issue.…”