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Results validate JetBOx’ EAF injection system
Steelmaking
Results validate
JetBOx EAF
injection system
Rigorous user trials and permanent installations have confirmed the
benefits of the JetBOx chemical energy and oxygen injection system
for electric arc furnaces
As previously featured in Steel Times For more than three years now, electric
arc steelmakers have had access to the
innovative JetBOx chemical energy and
oxygen injection system. Developed by oxy-
fuel burner specialist Process Technology
International (PTI; www.pticombustion.com) and
marketed jointly by PTI and Air Products PLC
2

(www.airproducts.co.uk), JetBOx brings a range of
benefits to EAF operation. Typically, JetBOx users
find they can increase production rates while
reducing electricity consumption per tonne of steel
by around 9%. Electrode consumption is reduced,
and injection of carbonand optionally filter
dustbecomes more efficient (see tables).
With more than 20 electric arc furnaces (EAFs)
worldwide now fitted with JetBOx systems,
there is plenty of hard evidence to support
these claims. Two of the most recent come from
German steelmaker Stahlwerk Thüringen (SWT;
www.stahlwerk-thueringen.de) and Dongkuk Steel
of Korea (www.dongkuk.co.kr).
A full JetBOx installation at Dongkuk Steel
Dongkuk Steels Inchon Works is located near
Seoul, South Korea. The company has a 100-tonne
DC EAF rated at 62 MW, and until August 2002
annual production was 869,000 tonnes.
The original combustion equipment included four
sidewall oxy-fuel burners located around the
periphery of the EAF, one EBT burner located above
the tapping hole, a slag door burner mounted
above the slag door, and a slag door lance
manipulator with a door burner and oxygen lance.
In August 2002 the combustion system was
upgraded. The existing slag door manipulator
was removed, and the four sidewall burners
were replaced by four JetBOxes. Each JetBOx
is equipped with a burner/oxygen injector. Each
injector has a supersonic oxygen injection capacity
of 42 m
3
/min (1,500 SCFM) and a maximum firing
rate of 4.5 MW for chemical energy introduction
by combusting LNG. Two of the JetBOxes are
used to inject carbon for building foamy slag and
recovering FeO.
achieved without reducing the yielda problem
SWT had previously experienced when trying to
increase oxygen input via the slag door lance.
Since the trial, the JetBOx has become a standard
part of the chemical energy package at SWT. The
unit has reduced electrical energy consumption
and improved chemical energy efficiency,
slag foaming consistency and refractory life
of the adjacent EBT area, says the melt shop
superintendent at SWT.
Other installations worldwide
The Dongkuk Steel and SWT installations are some
of the latest success stories in a larger series. The
collaboration between PTI and Air Products Europe
began in November 2000, with the installation
of Europes first JetBOx system on a 130-tonne
furnace at the Huta Zawiercie steelworks in
Poland.
Following their successful co-operation on the
Huta Zawiercie project, PTI and Air Products PLC
agreed to market the new technology across
Europe, the Middle East and North Africa. Since
that time JetBOx technology has spread further,
with installations in the USA, Asia and Europe.
JetBOx development continues; the latest JetBOx
design, for instance, includes two lances for solids
injection, allowing filter dust or other solids to be
injected as well as carbon.
JetBOx technology has been successfully applied
to smaller furnaces too. One example is Courtice
Gerdau, a Canadian steelmaker with a 38 t EAF.
Here, two JetBOxes replaced two sidewall burners
and a slag door lance manipulator. The installation
has cut power consumption by 10% and also
reduced power-on time. These benefits were
achieved with no increase in the consumption of
oxygen or natural gas, clearly demonstrating the
significantly better chemical energy efficiency
provided by JetBOx.
Steel Times
Steelmaking
Results validate JetBOx
EAF injection system
Rigorous user trials and permanent installations have confirmed the benefits of the
JetBOx chemical energy and oxygen injection system for electric arc furnaces
Before the JetBOx system was installed, Dongkuk
Steel was already achieving good performance
figures: electricity consumption was 375 kWh/
tonne and power-on time was 38 minutes. With the
JetBOx system, electricity consumption has fallen
to 336 kWh/tonne (a reduction of 39 kWh/tonne, or
10.4%). The power-on time has fallen by 4.1 min,
to 33.9 min, enabling Dongkuk Steel to achieve 32
heats per day instead of 2829 as previously.
There have also been significant improvements in
electrode consumption and bottom electrode life.
All these results were obtained without increasing
the consumption of oxygen and LNG (Table 1).
A JetBOx trial at Stahlwerk Thüringen
To get full benefit from a JetBOx installation, the
furnace should have enough JetBOxes to supply
all the necessary oxygenas at Dongkuk Steel.
However, installations using fewer JetBOxes can
be valuable in showing the value of the JetBOx
concept, and such was the case with SWT.
SWT is part of the Arcelor Group. At its plant
at Unterwellenborn, Germany, SWT produces
almost 900,000 tonnes/year of steel, mainly long
products for the construction industry. The EAF
plant, which was commissioned in the mid-1990s,
consists of a 120-tonne DC EAF, ladle furnace and
continuous casting machine.
Until last year the furnace had one slag door
water-cooled lance, a slag door burner and six air-
oxy-fuel burners around the furnace shell. In May
2002 a single JetBOx unit was installed. This unit,
which subsequently enabled one of the existing
sidewall burners to be eliminated, delivers about
half of the lancing oxygen and the majority of the
injected carbon that was previously supplied solely
by the slag door lance.
After a trial period lasting around 3.5 months (two
refractory campaigns), the JetBOx installation
was declared a success. Key indicators of this
success (Table 2) included a cut in electrical
energy consumption, reduced power-on time and
increased oxygen input while maintaining the
efficiency of oxygen use. All these measures were Table 1: Performance data for Dongkuk Steel, before and after the JetBOx conversion
Performance measure
Before JetBOx
After JetBOx
Change
Electricity (kWh/tonne)
375
336
39
Power-on time (min)
38.0
33.9
4.1
Tap-to-tap time (min)
51.5
46.5
4.0
Oxygen (Nm
3
/tonne)
42
42
0
LNG (Nm
3
/tonne)
5
5
0
Carbon (kg/tonne)
14
17
+3
Pig iron (%)
1112
78
4
Electrode (kg/tonne)
1.30
1.20
0.10
Bottom electrode (heats)
1,0001,200
1,500
+400
Heats per day
2729
3032
+3
Table 2: Performance data for Stahlwerk Thüringen (SWT), before and after replacement of a two
burners with a single JetBOx
Performance measure
Before JetBOx
With one JetBOx
Change
Electricity (1600°C tapping
temperature) (kWh/tonne)
368
356
12
Power-on time (min)
39.4
39.1
0.3
Oxygen (Nm
3
/tonne)
25.7
29.0
+3.3
LNG (Nm
3
/tonne)
6.5
6.9
+0.4
Carbon (kg/tonne)
5.2
5.5
+0.3
Active oxygen (ppm)
773
751
22
Tapping carbon (%)
0.05
0.05
0
Figure 1: Dongkuk Steel: the user interface of the JetBOx control system, showing how the four JetBOx
units are positioned around the furnace wall Figure 2: Stahlwerk Thüringen (SWT): installation of the JetBOx unit mounted on a new water-cooled panel. The No.6 burner, visible here to the left of the
JetBOx, was later eliminated as a result of the JetBOx installation
© Air Products and Chemicals, Inc. 2003
*Air Products PLC, Hersham Place, Molesey Road, Walton-on-Thames, Surrey KT12 4RZ, UK, Internet www.airproducts.com. Contact: Shawn Lainchbury.
Behind the performance benefits of the JetBOx
chemical energy and oxygen injection system
is a relatively simple idea: moving oxy-fuel
burner/injectors further into the furnace increases
penetration of the oxygen jet. By making oxygen
use more efficient, this reduces electricity
consumption. It also brings other benefits such as
better control of carbon injection and foamy slag
formation, and reduced electrode consumption.
For all oxy-fuel burners and lances, the challenge
is to keep the velocity and focus of the oxygen jet
high enough to provide good penetration through
the slag and into the molten steel beneath. Higher
jet velocity means faster decarburisation and more
efficient use of oxygen.
With conventional burners and lances mounted in
the sidewalls of the furnace, the supersonic jet of
oxygen has to travel a considerable distance
typically around 1,750 mmbefore it strikes the
molten metal. Over this distance it loses as much
as 30% of its velocity, and this greatly reduces the
penetration of the jet.
Past attempts to solve this problem have focused
on maintaining jet velocity, for example by
increasing the flow of oxygen. This approach
has drawbacks: apart from increasing oxygen
costs, excessive use of oxygen can cause panel
flashback and inc