Abstract
The global demand for decarbonized steel production requires a shift away from blast furnaces
toward hydrogen-based direct reduction. Fluidized Bed Reactors (FBR) offer the advantage of using
iron ore fines directly, and industrial processes such as Circored are already available. However, to
meet industrial production rates, atmospheric operated reactors, or only slightly pressurized ones,
require excessively large cross-sectional areas, leading to high capital expenditures. A high pressure
FBR presents a solution to this bottleneck. By operating at elevated pressures, the gas density
increases, allowing for a significantly higher mass flow of the gaseous reducing agent while operating
in the circulating or bubbling fluidized bed regimes at reasonable cross-sections. This allows for a
dramatic reduction in reactor footprint while maintaining high metallization rates.
The current work, in the scope of EU- Horizon ZEROSTEEL project, presents the mechanical design
and commissioning strategy of a novel pressurized FBR. The reactor designed for operation at
temperatures and pressures up to 850 °C/15 barg, utilizing a 50 mm inner diameter bed. In addition,
the unit is capable of operating with Hydrogen (H 2 ), Argon (Ar), and steam via an integrated
generator, allowing for precise control over inlet gas composition and reductant gas oxygen potential
(H 2 /H 2 O ratio), which in turn influences reduction kinetics. The partial pressure of oxygen, p O2 , of the
outlet gas can be measured to understand the ongoing reduction process in the FBR. Process
simulations demonstrate the impact of pressurization on throughput: while the designed reactor is
limited to < 1 kg/h of iron ore per batch at atmospheric pressure (from a fluidization point of view),
simulations indicate that operating at 10 bar and 700 °C allows for a continuous reduction rate of 7
kg/h within the same geometry. Batch experiments at a capacity of 0.5 kg / batch can also be realized
in the same unit.
The plant operation chain is presented in terms of the solid path (high-pressure solids feeding
system, pressurized FBR, overflow collection chamber as well as the setting for continuous probe
sampling) and the FBR off-gas path (high temperature filtration unit, a post combustion-chamber,
cooler and pressure control methodology). Preliminary commissioning results with use of two
Brazilian concentrates of varying impurity levels are discussed from the point of metallization and
undesired particle sintering tendency. The reactor is currently under construction, with
commissioning scheduled for February 2026.