Hot charging drI for Productivity and energy Benefits at ... - Midrex

Hot charging drI for
Productivity and energy
Benefits at Hadeed
By Gary Metius and John Kopfle
Midrex technologies, inc.
IntroDUctIon
The Saudi Iron and Steel Company Ltd. (Hadeed)
has a long history of successful operation of
natural gas-based direct reduction plants and
steelmaking facilities. Hadeed began operations
in 1982 with two MIDREX ® 400 Series Plants
(Modules A/B). A third MIDREX Module,
Module C, was added in 1992, and a fourth
module (HYL) in 1998. Figure 1 shows Modules
A, B and C. Hadeed produces 3.0 - 3.5 Mtpy of
cold DRI (CDRI) from these four modules. All the
DRI is used on-site and supplemented with scrap
steel in a ratio of approximately 70 percent cold
DRI and 30 percent scrap to produce 4.0 - 4.6
Mtpy of steel. Hadeed plays a valuable role in
producing steel for the growth of the Kingdom of
Saudi Arabia and surrounding countries.
moDULe e – tHe worLD’S LarGeSt
In December 2004, Hadeed awarded the contract to the
Consortium Siemens VAI - acting as Consortium Leader -
and Midrex Technologies, Inc. to build the world’s largest
direct reduction module, with a rated capacity of 1.76
Mtpy. Module E features a MIDREX ® Hot Discharge Shaft
Furnace of 7.15 meters inside diameter (the largest
shaft furnace in operation to-date). The main plant
configuration details are listed in Table I. Perhaps the
most significant feature of the facility is the HTS hot
transport system which is a joint development of
Siemens VAI, Aumund Fördertechnik GmbH and Midrex.
This system enables the plant to discharge nearly any
combination of cold DRI and hot DRI simultaneously.
Hot DRI is transported by conveyor directly to the adjacent
meltshop and charged to the EAF.
8
fiGUrE 1 Hadeed Modules A, B, C
tABLE i Hadeed Module E Details
mIDreX module type MEGAMOd (7.15 m id)
Start-up July 2007
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related works sea water pumping, oxide storage/reclaim, Cdri
capacity 1.76 Mtpy (220 tph)
reformer 19 bays (570 tubes)
Products Hot and cold dri
storage/reclaim, Hdri conveying, EAf charging system
target market(s) 100% captive use by Hadeed
DrI cooler Up to 100 percent capacity
Hot transport system Up to 90 percent capacity, transporting at ~ 650º C
oxygen use Approximately 15 Nm 3 /t Hdri
fiGUrE 2 Hadeed Module E
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Get It wHILe It’S Hot
The MIDREX Shaft Furnace is designed to discharge DRI at temperatures
around 700° C into a product discharge chamber (PDC), the same design used
in MIDREX HBI Plants. The PDC accomplishes three functions: depressurization
of the DRI, control of material flowrate, and keeping oxygen out of the system.
Hot DRI (HDRI) is discharged from the PDC into a mechanical conveyor provided
by Aumund. Aumund has significant experience in conveying equipment
and has used the similar designs in other applications worldwide.
The conveyor uses specially designed buckets to transport the HDRI,
as shown in Figure 3. The distance is 95 meters, with a lift of 48 meters.
The MIDREX Plant has an external DRI cooler to produce cold DRI (CDRI)
along with HDRI. CDRI is mainly produced at times when the meltshop is
shutdown. The DR plant can switch from HDRI to CDRI production very
quickly. In practice, some CDRI is always being produced to keep the
cooling system “live.”
Module E is shown in Figure 4 and the inclined covered conveyor leading
to the meltshop can be seen also. This system has several advantages versus
pneumatic transport, including lower investment cost, lower energy and
maintenance costs, and less product breakage. The conveyor is covered
and insulated to minimize temperature loss and prevent oxidation of the
HDRI during transport from the MIDREX Shaft Furnace to the meltshop.
HDRI is fed to two buffer bins above the meltshop, then metered
into the EAF at a controlled rate. The bins are sized to contain at least
one complete charge of HDRI each for the EAF, which facilitates the
transition from continuous DRI conveyance to discontinuous EAF charging.
As one bin is being emptied into the EAF, the other bin is being filled
with fresh HDRI.
The EAF has a tapping weight of 150 t and the estimated annual output
is 1.40 Mtpy of liquid steel, assuming HDRI is fed at 650° C. The electric
furnace is shown in Figure 5.
fiGUrE 5 siemens VAI Electric Furnace at Hadeed
9
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fiGUrE 3 Aumund Bucket Conveyor system
fiGUrE 4 Hadeed Module E, Hot Transport
Conveyor and Meltshop
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10
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BeneFItS oF Hot DrI cHarGInG
rather than dissipating it to the atmosphere lowers overall
There are two main benefits of hot charging DRI to the EAF: lower emissions two ways. First, the lower electricity demand reduces
specific electricity consumption and increased productivity. The power plant emissions per ton of steel produced. Second, for those
energy savings occur because less energy is required in the EAF to mills employing carbon injection, reduced energy requirements in
heat the DRI to melting temperature. In addition to a lower energy the EAF result in less CO2 given off.
requirement, it also takes less time, thus shortening the overall Ultimately, the most important consideration for the steel-
melting cycle. This allows higher production through a given size EAF. maker is that HDRI charging can enhance profitability. The interest
The rule-of-thumb is that electricity consumption can be shown in hot charging by Midrex clients speaks for itself. Table II
reduced about 20 kWh/t liquid steel for each 100° C increase in
DRI charging temperature. Thus, the savings when
shows MIDREX Plants employing hot charging.
charging at over 600° C are 120 kWh/t or more. An
additional benefit of the electricity savings is a
tABLE ii MIDREX Plants Employing Hot DRI Charging
reduction in electrode consumption, since there is PLant LocatIon Start-UP tyPe SyStem
a linear relationship.
Essar steel Mods i,ii,iii,iV india 1999-2004 Vessels
The increased productivity from HDRI charging
Hadeed E saudi Arabia 2007 Hot Conveyor
is significant. Use of HDRI reduces the tap-to-tap
time, allowing a productivity increase of up to 20
percent versus charging at ambient temperature.
Lion Group
EsisCO
Malaysia
Egypt
2007
2010
Vessels
HOtLiNK
There are also environmental benefits of HDRI
charging. Retaining the sensible heat in the DRI
shadeed Oman 2010 HOtLiNK
reSULtS at HaDeeD
Hadeed has achieved outstanding results in the
Module E MIDREX Plant and EAF. From May 15
through October 28, 2008, with all plant equipment
operating well, the plant produced 873,000 tons,
for an average hourly production rate of 218 t/h.
The availability during that time was 98.5 percent
and there was no downtime from July 27-
October 28, a period of 94 days. Figure 6 shows
daily production during that period.
tONs PEr dAy
6000
5000
4000
3000
2000
1000
rated Capacity
0
May ‘08 June ‘08 July ‘08 Aug ‘08 sept ‘08 Oct ‘08
fiGUrE 6 Hadeed Module E MIDREX Plant DRI
Production May 15-October 28, 2008
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A 48 hour EAF trial with 100 percent hot
DRI was run in May 2008. In June, a
multi-day MIDREX Plant HDRI trial was
performed. Averages of some parameters
during those tests are shown in Table III.
During the HDRI trial, eight days of EAF and
DR plant operation were carefully monitored.
This test was indicative of actual meltshop
operations, covering a full weekly cycle,
including the EAF shell change.
Over time, Hadeed has adjusted DRI
parameters to achieve high productivity
in the meltshop. Specifically, carbon content
has been increased at the expense of
temperature. The June-October period was a
good representation of the DR plant and meltshop
capability because all demonstration
testing was complete, with the plant running
in the normal mode, and with good market
demand. During this time, the DRI feed
to the EAF averaged 95.3 percent metallization,
2.6 percent carbon and about 500° C.
Unfortunately, because of the severe
world economic downturn, the DR plant and
meltshop have been operating at reduced
levels since October.
FUtUre PoSSIBILItIeS
Hadeed has been quite pleased with the performance of Module
E and the use of hot DRI in the EAF and is considering an
additional DR plant. The substantial benefits of DRI temperature
have been shown at Hadeed and at other integrated steel mills
employing direct reduction plus hot charging to the EAF. As an
example, a 17 percent productivity boost, which is possible by hot
charging at 600° C, could be worth an extra $24 to 48 million per
year in profit, depending on the profit margin per ton.
concLUSIonS
Hadeed’s long history of successful DRI and steel production has
continued with MIDREX Plant Module E and the system to transport
hot DRI to the meltshop. The DR plant has produced at rated
capacity for extended periods of time and the EAF performance
using hot DRI has been outstanding.
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tABLE iii Hadeed Meltshop Results Using 100% HDRI
trial 1 trial 2
may 2008 June 2008
dri into EAf
Metallization (%) 95 95.4
Carbon (%) 2.1 1.8
temperature (ºC) 579 599
EAf performance
No. of heats 60 198
Power on time (min.) 40 40
Electricity consumption (kWh/t) 385 398
Oxygen consumption (Nm3 /t) 26 25
Electrode consumption (kg/t) 0.8 -
Productivity (t/h) 188 158
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