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Non-geological hydrogen storage for fossil-free steelmaking

Time: Fri 2022-04-08 14.00

Location: Kollegiesalen, Brinellvägen 8, Stockholm

Video link: https://kth-se.zoom.us/j/66521083318

Language: Swedish

Subject area: Chemical Engineering

Doctoral student: Joakim Andersson , Energiprocesser

Opponent: Professor Simon Harvey, Chalmers tekniska högskola

Supervisor: Universitetslektor Stefan Grönkvist, Energiprocesser

QC 2022-03-10

Abstract

In the last half-century, global steel use has increased more than threefold and further growth is expected, particularly in developing economies. However, steelmaking is currently responsible for 7% of the global net carbon dioxide (CO2) emissions, and any substantial further optimization of existing processes that utilize fossil fuels for iron ore reduction is infeasible. Therefore, steelmaking must change for climate change mitigation targets to be achievable. Hydrogen (H2) steelmaking using H2 produced via electrolysis is one way forward. A challenge is the substantial electricity demand of electrolysis. H2 storage may lower the electricity cost of electrolysis by allowing a larger share of H2 to be produced when the electricity price is low. Existing experience with large-scale H2 storage is limited to salt caverns and the construction of such caverns requires suitable geological formations, which are neither ubiquitous nor well-distributed. However, geologically-independent H2 storage technologies have not previously been evaluated for integration with H2 steelmaking. This is the aim of this thesis. H2 storage technologies were reviewed and liquid H2 carriers were identified as the most techno-economically feasible non-geological options. Out of these liquid carriers, methanol (CH3OH) was found particularly promising for H2 steelmaking due to the low heat demand of its dehydrogenation, its low-cost storage, and the high technological readiness of plants for both its production and dehydrogenation. A complete CH3OH-based H2 storage concept was developed, including processes for CO2 and heat supply. Its ability to reduce the H2 production cost in a H2 steelmaking process was evaluated via a deterministic optimization method based on historical electricity prices. Results indicate that CH3OH-based storage may be competitive with geological storage options, especially for cases with long-duration electricity price patterns.  The option to also sell off accumulated CH3OH from the storage was investigated. Such steel and CH3OH co-production may improve storage utilization and reduce the risk of investment into H2 storage as it allows for profitability to be reached under a more diverse set of electricity market conditions.

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