May 2007 - SIMA

• Dust is generated during handling and
transportation of iron ores, DRI, solid
reducing agents and ash; the latter two
only using alternate sources of reducing
gases, other than natural gas. Typically,
the material handling of an Energiron plant
consists of the iron ore and product
handling systems. These systems include
bins, screening units, coating unit,
conveyors, and transfer stations. Air
pollution caused by dust is minimized by
installing appropriate dust collectors in the
main generation points, typically in trasfer
locations and screening units.
• Flue gases containing the polluting
elements SO x and NO x , are derived from
the combustion systems of the reducing
gas generation units, gas heaters and
rotary kilns. The amount of SO x and NO x
can be decreased in gas based processes
by an adequate control of combustion
operations, and by desulfurization of the
fuel gas stream to be used, both as
process gas (reducing gas) and as fuel.
The process chemistry of each technology
will determine how difficult or how easy this
control will be. In the case of the
Energiron technology, SO x is selectively
eliminated in the CO 2 absorption unit and
NO x is easily controlled by low-NO x type
burners, allowing compliance with even the
strictest standards.
• Suspended solids in the effluents from the
water systems consist mainly of iron oxide
and DRI particles, collected in the wet
systems of the different sections of the
plant. These solids can be dried and
concentrated to be sold or reused as
feedstock in the reduction units.
Environmental Impact
Emissions from Energiron plants are in
accordance with the most stringent environmental
regulations anywhere. This is achieved in large
part due to the process design itself; while other
processes require heat recovery equipment which
tends to increase the NO x levels, the Energiron
Process is efficient by design due to its process
configuration and heat recovery systems.
Depending on the type of plant, heat recovery
systems consists of:
• With external reformer - the efficiency is
achieved by generation of steam, which is
required for natural gas reforming and for
CO 2 stripping. Prior to end-using, the steam
is used in some steam turbines for power
co-generation, reducing significantly
electricity consumption.
• With “in-situ” reforming, the steam required
in CO 2 stripping is generated in the top gas
heat recuperator.
Thus, while achieving high overall thermal
efficiency in the plant, there is no significant need
for preheating the combustion air in the reformer
or in the heater to high temperatures, thus
eliminating the possibility of high NO x generation.
For other DR processes, this is not the case and
the choice between decreasing thermal efficiency
or installing expensive de-NO x units remains.
The tables summarize the environmental impact
of Energiron plants, comprising solid wastes,
emissions to the air and water, and noise. These
levels comply with the strict standards imposed in
such areas as the USA, Saudi Arabia, Malaysia
and other nations with the most modern
environmental standards, including new standards
proposed but not yet enacted.
Tenova HYL together with Danieli has been
working on a project for a plant of 1.6 million tpy
capacity being built for GHC in Abu Dhabi, where
environmental controls are also among the
strictest anywhere. Still, the values achieved are
well within the requirements for compliance.
Table I
Solid Wastes (kg/ton DRI)
Recycled Dumped Total
• Dust collected 3.20 - 3.20
• Iron oxide fines - 26.70 26.70
• DRI cooling losses - 6.45 6.45
• Others 0.25 0.35 0.60
MAY-2007/34