Abstract:

Scope

Hatch’s presentation will focus on technologies to eliminate fossil fuel requirements for steam generation in integrated steel mills. The role of various technologies including waste heat recovery, thermal energy storage, and electric boilers will be discussed and compared in terms of CapEx, OpEx, Footprint, and GHG emissions against conventional boilers.

Methodology

The Hatch Thermal team will utilize experience from recent steel mill projects, relationships with major technology providers, recent Hatch surveys of steam decarbonization technologies, and open literature to provide an overview of current and future trends and capabilities.

Waste heat recovery from Electric Arc Furnaces, Reheat Furnaces, Direct Reduced Iron, and other sources is essential to reducing GHG emissions by utilizing energy that would otherwise be wasted. This includes both new installations and retrofitting existing facilities, and how these waste heat sources can be combined with thermal energy storage, electric boilers, and conventional boilers to satisfy the requirements of the steel mill while reducing emissions and OpEx.

Results & Conclusions

Currently, many integrated steel mills utilize by-product gases (Coke Oven Gas, Blast Furnace Gas, Basic Oxygen Gas) for steam and power generation. Natural gas is the most common additional fuel used to supplement fuel generation, but other fuels (e.g. fuel oil) can also be utilized.
As steel mills move towards Net-Zero targets, steam is a “low-lying fruit” to reduce overall GHG emissions from the plant.
Traditionally, many waste heat recovery sources exist, but the economics were not favorable when compared to conventional by-product fuel and natural gas fired boilers. As the cost of GHG emissions has increased, waste heat recovery for steam generation has become more attractive.
Issues arise with matching supply and demand of steam when utilizing waste heat recovery sources, and generally redundant sources of steam are required to bridge the gap when waste heat recovery sources are not available.
There are new and upcoming technologies for thermal energy storage for steam generation, which utilize a thermal medium such as checkered brickwork (similar to Blast Furnace Stoves) to be charged electrically using renewable grid supply, and discharged to produce hot air into a heat recovery boiler (Heat Recovery Steam Generator). These technologies can be coupled with waste heat recovery boilers to reduce reliance on natural gas systems
The Net Present Value of waste heat recovery boilers, electric boilers, and conventional natural gas boilers varies depending on region, commodity prices, carbon tax, and the steel mill’s GHG targets. A steam model can be utilized to compare these technologies, capturing all key costs and assumptions, and finding the best fit for a specific steel mill's needs.
The integration of waste heat recovery, thermal energy storage, and electric boilers has the potential to provide a steam system with zero direct emissions for steel mills while satisfying the needs of all steam users.

Keywords: Integrated Steel Mills, Steam, Waste Heat Recovery, Electric Boilers, Thermal Energy Storage

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Dr. Rafat Hirmiz