Circored® is a two stage fluidized bed process, reducing iron ore fines directly without prior
agglomeration, that operates at low reduction temperatures using pure hydrogen as the reducing
gas. The hydrogen is produced by means of natural gas reforming, but hydrogen from sources
other than a steam reformer, e.g. from water electrolysis, can also be used. The first reduction
stage is a circulating fluidized bed (CFB), the second reduction stage a fluidized bed (FB)
reactor. To heat up the fine grained DRI product to briquetting temperature a flash heater is
applied.
Key steps in the Circored® process:
• Preheating of iron ore fines in a CFB at approximately 850-900°C
• Fast prereduction step in a further CFB at 630°C to 65-75% metallization
• Final reduction in an FB at 650°C to 93-95% metallization
• Flash heater to achieve briquetting temperatures of about 700°C.
The offgas from the recycle cyclone of the CFB reduction reactor passes through a process gas
heat exchanger and a multiclone for the recovery of part of the dust particles, which is recycled
into the flash heater. The offgas is then scrubbed and quenched simultaneously for the final
removal of dust and water produced during reduction.
To recover the scrubber dust, we have developed a microgranulation process, in which the ultra
fine particles are agglomerated to microgranules with the addition of a binder to an average size
of about 350 µm. No additional heat hardening equipment is required as the hardening of the
granules takes place in the preheating section of the Circored plant. Microgranulation could also
be applied in case ultra fine ores, such as pellet feed, have to be processed.
The cooled and cleaned process gas is recompressed and subsequently preheated in gas fired
heaters to a temperature of approximately 750°C before being reintroduced into the reduction
reactor system. The hot charging option allows the produced DRI to be fed directly without
briquetting into the EAF.
The Circored-EAF route emits only about 50% of the CO2 emitted by the conventional blast
furnace-oxygen converter route, assuming hydrogen generation by conventional steam
reforming. If both, hydrogen, generated by water electrolysis, and electrical power for the EAF,
would be based on renewable energy, CO2 emissions could be decreased by up to 90%.
• HBI production: 65 t/h
• Ore feed (wet basis): 1.65 t/t HBI
• Natural gas consumption: 350 Nm³/t HBI
o For hydrogen production: 260 Nm³/t HBI
o For heating purposes: 90 Nm³/t HBI
• Electrical energy consumption 137 kWh/t HBI (incl. hydrogen plant).
To minimize specific ore consumption we have developed a microgranulation process, which
would decrease ore consumption nearly to the theoretical minimum.
