metals
Article
Fundamental Study on Electric Arc Furnace Steelmaking with
Submerged Carbon Powder Injection with CO2-O2 Mixed Gas
Jianjun Li 1,2 , Guangsheng Wei 3,4, * and Chengjin Han 3
1
2
3
4
*
National Engineering Research Center of Continuous Casting Technology, China Iron & Steel Research
Institute Group, Beijing 100081, China
Metallurgical Corporation of China Co., Ltd., Beijing 100028, China
School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing,
Beijing 100083, China
Liaoning Academy of Materials, Shenyang 110000, China
Correspondence: weiguangsheng@ustb.edu.cn
Abstract: The technology of submerged carbon powder injection with CO2 and O2 mixed gas
(SCPI-COMG) is a new type of powder injection technology. It can increase the molten bath carbon
content and improve the molten steel quality by injecting carbon powder directly into the molten
steel with CO2 and O2 mixed gas. To optimize the process parameters of this novel technology,
the mechanism of this technology and the effect of SCPI-COMG on EAF steelmaking were investigated
in this study. Based on an induction furnace experiment, the effects of molten bath carburization and
fluid flow on the scrap melting were analyzed. A mathematical model of the axis of gas jets in liquid
steel was built to analyze the impact behaviors of gas jets in liquid steel. Based on the results of this
theoretical model, for a gas jet in liquid steel, with α ≥ 20◦ , the horizontal inject distance decreases
with α increasing and with 0◦ ≤ α ≤ 20◦ , the horizontal inject distance increases with α increasing.
Finally, based on the newly built materials and energy balance model of EAF steelmaking with
SCPI-COMG, the influences of the gas-solid parameters on the EAF steelmaking technical indexes
were also analyzed.is very useful for optimizing the process parameters of EAF steelmaking with
SCPI-COMG. The results of this study are very useful to optimize the process parameters of EAF
steelmaking with SCPI-COMG of Gas Jet in Liquid Steel.
Citation: Li, J.; Wei, G.; Han, C.
Fundamental Study on Electric Arc
Furnace Steelmaking with Submerged
Keywords: electric arc furnace steelmaking; submerged gas-solid jet; jet impact characteristics;
material and energy modeling
Carbon Powder Injection with CO2 -O2
Mixed Gas. Metals 2023, 13, 1602.
https://doi.org/10.3390/
met13091602
Academic Editor: Henrik Saxen
Received: 24 July 2023
Revised: 23 August 2023
Accepted: 11 September 2023
Published: 15 September 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
1. Introduction
Nowadays, the electric arc furnace (EAF) steelmaking has been widely adopted
for steel production on a worldwide scale and demonstrates great potential for development because EAF steelmaking can produce steel products flexibly with lower CO2 emissions, which is very helpful in promoting recycling and utilization of scrap resources [1–3].
Recently in China, a large number of EAFs have been newly built, including ordinary AC
EAF, Consteel EAF, EAF Quantum and so on. It can be predicted that EAF steelmaking will
play a more and more important role in steelmaking and more and more steel grades will
be produced by the EAF steelmaking process [4–6]. Therefore, the control and promotion
of the quality of molten steel will be of great importance for EAF steelmaking.
Compared with converter steelmaking, high-quality steel production is always a key
issue and challenge in EAF steelmaking because it is very difficult to produce molten steel
with low phosphorous content, low nitrogen content and low oxygen content in an EAF [7–9].
In EAF steelmaking, the weakened molten bath reaction kinetics conditions make it hard
to remove the phosphorus from the molten steel [10]. Due to the lack of a carbon source by
scrap charging, the carbon and oxygen reaction is considerably insufficient in the molten
bath, which leads to the lack of CO bubbles. As a result, metallurgical problems occur,
Metals 2023, 13, 1602. https://doi.org/10.3390/met13091602
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Metals
13, 1602
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2023,2023,
13, 1602
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the as
molten
bath, difficulty
which leads
the lack of
CO bubbles.
As aserious
result, metallurgical
such
the great
intonitrogen
removal
and the
peroxidationproblems
of molten
occur,
such
as
the
great
difficulty
in
nitrogen
removal
and
the
serious
peroxidation
steel [11,12]. Generally, carbonaceous materials are charged into the EAF to
increase theofcarmolten
steel
Generally,
carbonaceous
areHowever,
charged into
the EAF
to inbon
content
of [11,12].
the molten
steel, such
as pig ironmaterials
and coke.
pig iron
is produced
crease
the
carbon
content
of
the
molten
steel,
such
as
pig
iron
and
coke.
However,
pig
by blast furnaces and the process is of high energy consumption, which is bad for iron
green
is produced[13].
by blast
furnaces
is ofon
high
consumption,
which
bad
steelmaking
Coke
would and
floatthe
upprocess
and burn
theenergy
surface
of the molten
bathisduring
green steelmaking
Coke would
floatis up
and
burn
on the surface
thefor
smelting
process and[13].
its utilization
ratio
very
low.
Therefore,
based of
onthe
themolten
powder
bath
during
the
smelting
process
and
its
utilization
ratio
is
very
low.
Therefore,
based
injection technology, the technology of submerged carbon powder injection with CO2on
and
powder injection technology, the technology of submerged carbon powder injection
O2the
mixed
gas (SCPI-COMG) was proposed and developed, which injects carbon powder
with CO2 and O2 mixed gas (SCPI-COMG) was proposed and developed, which injects
directly into the molten steel with CO2 and O2 mixed gas (shown in Figure 1) [14,15].
carbon powder directly into the molten steel with CO2 and O2 mixed gas (shown in Figure
Firstly, the method of delivery of carbon powder directly into the molten steel significantly
1) [14,15]. Firstly, the method of delivery of carbon powder directly into the molten steel
improves the carbon pick-up of the molten steel. Secondly, the gas flow rate of the subsignificantly improves the carbon pick-up of the molten steel. Secondly, the gas flow rate
merged injection is about 300 to 600 Nm3 /h and the3 stirring of the EAF molten bath can be
of the submerged injection is about 300 to 600 Nm /h and the stirring of the EAF molten
noticeably enhanced. In industrial application research, the metallurgical effects have been
bath can be noticeably enhanced. In industrial application research, the metallurgical efimproved significantly in EAF steelmaking with SCPI-COMG. Wei et al. [16] used water
fects have been improved significantly in EAF steelmaking with SCPI-COMG. Wei et al.
model
experiments
andexperiments
numerical simulations
performed
to performed
investigatetothe
flow field
[16] used
water model
and numerical
simulations
investigate
characteristics
in
the
EAF
metal
bath
under
combined
blowing,
considering
two
merged
the flow field characteristics in the EAF metal bath under combined blowing, considering
nodules
and
two
oven
wall
oxygen
lands.
However,
as
a
novel
method,
the
mechanism
two merged nodules and two oven wall oxygen lands. However, as a novel method, the
of mechanism
this technology
and
the effect and
of SCPI-COMG
on EAF steelmaking
haveprocess
not been
of this
technology
the effect of SCPI-COMG
on EAF process
steelmaking
clear,
which
is
very
useful
to
optimize
the
process
parameters
of
EAF
steelmaking
with
have not been clear, which is very useful to optimize the process parameters of EAF
SCPI-COMG.
steelmaking with SCPI-COMG.
System for carbon
powder injection
Submerged injector
Electric Arc
Furnace
CO2-O2
Carrier gas &
Carbon powder
Ar / CO2
Gas for preventing clogging
Gas for cooling injector CH4 /Ar / CO2
Figure
The
systemofofsubmerged
submergedcarbon
carbon powder
powder injection
injection with
2 mixed
gas
in in
EAF.
Figure
1. 1.
The
system
withCO
CO2-O
gas
EAF.
2 -O
2 mixed
InIn
this
study,
carriedout
outtotounderstand
understandand
and
analyze
this
study,some
somefundamental
fundamentalstudies
studies were carried
analyze
thethe
mechanism
Aninduction
inductionfurnace
furnaceexperiment
experiment
mechanismofofEAF
EAFsteelmaking
steelmaking with
with SCPI-COMG.
SCPI-COMG. An
was
carried
investigate
the
mechanismofofscrap
scrapmelting
meltingbybymolten
moltenbath
bathcarburization
carburizawas
carried
outout
to to
investigate
the
mechanism
tion
and molten
bath flow.
fluid To
flow.
To analyze
the impact
behaviors
of gas
the gas
jetliquid
in liquid
and
molten
bath fluid
analyze
the impact
behaviors
of the
jet in
steel,
steel, a mathematical
the axis
of the
liquidsteel
steelwas
was built.
built. The
a mathematical
modelmodel
of theofaxis
of the
gasgas
jet jet
in in
liquid
Thematerials
materials
and
energybalance
balance model
model of
with
SCPI-COMG
was was
built built
to study
the
and
energy
of EAF
EAFsteelmaking
steelmaking
with
SCPI-COMG
to study
ofof
thethe
gas-solid
parameters
on the
EAFEAF
steelmaking
technical
indexes.
theinfluence
influence
gas-solid
parameters
on the
steelmaking
technical
indexes.
Mechanismfor
forImproving
ImprovingScrap
Scrap Melting
Melting by Molten
2. 2.
Mechanism
Molten Bath
BathCarburization
Carburization
2.1.
Experimental
Platform
2.1. Experimental Platform
InIn
order
totostudy
scrap melting
meltingby
bymolten
moltenbath
bathcarbucarburorder
studythe
themechanism
mechanismfor
for improving
improving scrap
ization
with
thethe
SCPI-COMG
technology,
Figure 2
rization
with
SCPI-COMG
technology,the
theexperimental
experimentalplatform
platform was
was built as Figure
2 shows,
which
includes
a mediumfrequency
frequencyinduction
induction furnace,
furnace, aa buffer
2 2
shows,
which
includes
a medium
buffervessel
vesselwith
withNN
cylinders,a afixing
fixingdevice,
device,aaPt-Rh-Pt
Pt-Rh-Pt thermocouple,
thermocouple, an
cylinders,
an infrared
infraredradiation
radiationthermometer
thermometer
and
a computer.InInthis
thisstudy,
study,the
thediameter
diameter of the steel
was
and
a computer.
steel bar
barused
usedfor
forthe
theexperiment
experiment
was
mm.The
TheCC content
content of
about
0.45%.
Melting
bathsbaths
with with
different
C contents
2020
mm.
ofthe
thebar
barwas
was
about
0.45%.
Melting
different
C conandand
different
stirring
intensities
were were
used used
to study
the influence
of C content
and melt
tents
different
stirring
intensities
to study
the influence
of C content
and
melt flow on the melting of steel scrap. Physical changes such as weight changes and
microstructural changes of the steel bar inserted in the bath were monitored and analyzed.
The experimental program is shown in Table 1.
Metals 2023, 13, 1602
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flow on the melting of steel scrap. Physical changes such as weight changes and micro3 of 15
structural changes of the steel bar inserted in the bath were monitored and analyzed.
The
experimental program is shown in Table 1.
Figure2.2.Experimental
Experimentalplatform
platformfor
forscrap
scrapmelting
meltinganalysis.
analysis.
Figure
Table1.1.The
Thecomposition
compositionofofmolten
moltenbath
bathwith
withdifferent
differentCCcontent.
content.
Table
Label
Label content
High carbon
w(C)%
w(Si)% w(Mn)%
w(P)%
w(S)% Gas Flow Rate
w
w
w
w (P)%0.036
w (S)% 0.015Gas Flow
Rate
4.030 (Si)%0.640(Mn)%0.310
3.0 L/min
(C)%
Highcarbon
carbon
content 4.030
3.010 0.6400.620 0.310 0.3200.036 0.037
3.0 L/min
High
content
0.015 0.016 3.0 L/min
Highcarbon
carbon
content 3.010
2.100 0.6200.630 0.320 0.3300.037 0.037
3.0 L/min
High
content
0.016 0.015 3.0 L/min
High
carbon stirring
content
2.100
0.015 0.016 3.0 L/min
Weaker
3.010 0.6300.620 0.330 0.3200.037 0.037
3.0 L/min
Medium
stirring
Weaker
stirring
Medium
stirring
Stronger
stirring
Stronger stirring
3.030 0.6200.580 0.320 0.3600.037 0.0330.016 0.014 3.0 L/min
5.0 L/min
3.010
3.030
0.014 0.017 5.0 L/min
2.980 0.5800.610 0.360 0.3500.033 0.034
7.0 L/min
2.980
0.610
0.350
0.034
0.017
7.0 L/min
2.2. Analysis of Experimental Results
2.2. Analysis
of Experimental
The melting
process ofResults
scrap consists of three stages: the iron coagulating stage, the
The melting
process stage,
of scrap
three stages:
the iron
coagulating
stage,
carburizing
and melting
andconsists
the fullofboiling
stage [17–19].
The
iron coagulating
the
carburizing
and
melting
stage,
and
the
full
boiling
stage
[17–19].
The
iron
coagulating
stage occurs initially after the steel bar’s immersion into the molten bath. The large temstage
occurs
initially
after the
immersion
into
thecauses
molten
bath.
Themolten
large
perature
gradient
between
the steel
steel bar’s
bar and
the molten
pool
some
of the
temperature
gradient
between
steel bar
andsteel
the bar.
molten
causes some
the molten
metal to freeze
quickly
on thethe
surface
of the
Thepool
carburizing
and of
melting
stage
metal
freeze quickly
the melting
surface of
steel
carburizing
and melting
stagecaris
is theto
controlling
unit on
of the
of the
scrap
in bar.
EAFThe
steelmaking.
During
this stage,
the
controlling
unit
of
the
melting
of
scrap
in
EAF
steelmaking.
During
this
stage,
carbon
bon from the molten metal penetrates the surface of the scrap, thus accelerating the scrap
from
the process.
molten In
metal
penetrates
the surface
of the scrap,
thus
accelerating
the scrap
melting
the full
boiling stage,
the temperature
of the
molten
bath is larger
than
melting
process.
In
the
full
boiling
stage,
the
temperature
of
the
molten
bath
is
larger
than
the steel melting point and the scrap melting rate is very faster.
the steel
meltingthe
point
and the scrap
melting
rate
is very faster.
Actually,
carburization
process
of the
carburizing
and melting stage is the main
process
of the carburizing
and melting
stage is
the main
link.Actually,
Based onthe
thecarburization
iron-carbon phase
diagram,
the iron-carbon
alloy melting
point
is delink.
Based
on
the
iron-carbon
phase
diagram,
the
iron-carbon
alloy
melting
point
is
creased by 78.5 °C with a 1.0% increase in the C content of iron-carbon alloy [20,21]. Thus,
◦ C with a 1.0% increase in the C content of iron-carbon alloy [20,21].
decreased
by
78.5
when the molten bath temperature is higher than the melting point of the carburized layer,
Thus,
when the
molten
batharound
temperature
higher
than the melting
the molten
metal
flowing
it will is
melt
the carburized
layer.point of the carburized
layer, Figure
the molten
metal
flowing
around
it
will
melt
the
carburized
layer. bath carbon con3a,b show the steel bar weight change with different molten
Figure
3a,b
show
the
steel
bar
weight
change
with
different
molten
bath carbon
tent and different molten bath stirring intensity, respectively. As shown
in Figure
3a, the
content and different molten bath stirring intensity, respectively. As shown in Figure 3a,
lower the C content in the melt bath, the heavier the steel bar weight. The mass melting
the lower the C content in the melt bath, the heavier the steel bar weight. The mass melting
rates for the low, medium and high C content baths were 1.19 g/s, 0.96 g/s and 0.79 g/s,
rates for the low, medium and high C content baths were 1.19 g/s, 0.96 g/s and 0.79 g/s,
respectively, for 0 s to 30 s. The mass melting rates were 2.98 g/s, 2.66 g/s and 2.14 g/s for
respectively, for 0 s to 30 s. The mass melting rates were 2.98 g/s, 2.66 g/s and 2.14 g/s
low, medium and high carbon content in the melt pool from 40 s to 55 s, respectively. In
for low, medium and high carbon content in the melt pool from 40 s to 55 s, respectively.
addition to this, this phenomenon is also observed in other time periods. In Figure 3b, the
In addition to this, this phenomenon is also observed in other time periods. In Figure 3b,
weaker the stirring of the bath, the higher the weight of the bars. The mass melting rate is
the weaker the stirring of the bath, the higher the weight of the bars. The mass melting rate
1.06 g/s, 0.1.05 g/s and 0.96 g/s for strong, medium and weak bath agitation from 0 s to 30
is 1.06 g/s, 0.1.05 g/s and 0.96 g/s for strong, medium and weak bath agitation from 0 s
s. The mass melting rate is 3.02 g/s, 2.87 g/s and 2.66 g/s for bottom-blowing gas flow rates
to 30 s. The mass melting rate is 3.02 g/s, 2.87 g/s and 2.66 g/s for bottom-blowing gas
of 7.0 L/min, 5.0 L/min and 3.0 L/min from 40 s to 55 s, respectively. The same phenomeflow rates of 7.0 L/min, 5.0 L/min and 3.0 L/min from 40 s to 55 s, respectively. The same
non also can be found in other time ranges.
phenomenon also can be found in other time ranges.
Metals
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2023,13,
13,1602
1602
4 of 154 of 15
Figure 3. Weight change of the steel bar in molten bath with different C content and different stirring
intensity: (a) different C content; (b) different stirring intensity.
According to the experimental results, the carbon content of the melt bath and the
The
lower the melt bath carbon content, the slower the melt bath stirring, then the slower the
According
to
experimental
carbon content
contentgradient,
ofthe
themelt
melt
bath
andthe
the
According
to the
carbon
of
bath
and
intenscrap melting
rate.
Theexperimental
smaller theresults,
carbonthe
concentration
the
slower
the
carburiintensity
of
the
melt
bath
stirring
have
a
significant
effect
on
the
melting
of
the
scrap.
The
sity of
the meltspeed.
bath stirring
have a intensity
significantof
effect
onstirring
the melting
of the
The convective
lower
zation
reaction
The lower
bath
results
inscrap.
a lower
lower
thebath
melt carbon
bath carbon
content,
the slower
bath
stirring,
then
slowerthe
the
the melt
content,
the slower
the the
meltmelt
stirring,
then
thethe
slower
heat
transfer
coefficient,
whichthe
reduces
the
heat bath
transfer
from
molten
metal
to scrap
scrap. For
scrap
melting
rate.
The
smaller
carbon
concentration
gradient,
the
slower
the
carburimelting rate. The smaller the carbon concentration gradient, the slower the carburization
EAF
steelmaking
with
SCPI-COMG,
the
molten
bath
carbon
content
can
be
effectively
zation
reaction
The lower
intensity
of bath
stirring
results
lowerconvective
convective heat
reaction
speed.speed.
The lower
intensity
of bath
stirring
results
inin
a alower
increased
by
the
direct
carbon
injection
into
the
molten
steel
of
high
temperature
and the
heat
transfer
coefficient,
which
reduces
the
heat
transfer
from
molten
metal
to
scrap.For
ForEAF
transfer coefficient, which reduces the heat transfer from molten metal to scrap.
EAF
steelmaking
with
SCPI-COMG,
the
molten
bath
carbon
content
can
be
effectively
molten
bath stirring
can be noticeably
enhanced
by submerged
injection
with
CO2 and O2
steelmaking
with SCPI-COMG,
the molten
bath carbon
content can be
effectively
increased
increased
by
the
direct
injection
into
thesteel
molten
steeltemperature
of
high
temperature
and
the bath can
mixed
gas,
which
is injection
ofcarbon
largeinto
gasthe
flow
rate.
Therefore,
the
SCPI-COMG
technology
by the
direct
carbon
molten
of high
and the molten
molten
bath
can by
be noticeably
enhanced
by submerged
injection
CO
O2quality
stirring
can stirring
be noticeably
enhanced
by submerged
injection
withWhat
COwith
O22 and
mixed
gas,
shorten
tap-to-tap
time
accelerating
the smelting
of scrap.
is more,
the
of
2 and
mixed
gas,
which
is
of
large
gas
flow
rate.
Therefore,
the
SCPI-COMG
technology
can
whichsteel
is of also
large can
gas flow
rate. Therefore,
the SCPI-COMG
technology
can
shortencontent.
tap-to- The
molten
be improved
by increasing
the melting
down
carbon
shorten
tap-to-tap
time by the
accelerating
the
smelting
of scrap.
Whatthe
is more,
theofquality
ofsteel
tap time
by accelerating
smelting
of bath,
scrap.the
What
is more,
quality
higher
thesteel
carbon
of the
molten
CO
bubbles
in content.
the molten
molten
molten
also content
can be improved
by increasing
the more
melting
down
carbon
The bath and
also
canthe
be improved
by increasing
the melting
down carbon
content. The higher
the carthehigher
better
reaction
kinetics
Hence,
dephosphorization
efficiency
can be
the carbon
content
of the conditions.
molten bath, the
more the
CO bubbles
in the molten bath
and
bon content of the molten bath, the more CO bubbles in the molten bath and the better
improved
the peroxidation
of molten
steel
be reduced. What
is more,
the betterand
the reaction
kinetics conditions.
Hence,
the can
dephosphorization
efficiency
can be more CO
the reaction kinetics conditions. Hence, the dephosphorization efficiency can be improved
improved
and
the peroxidation
of molten
steel
can
be reduced.
What is more, more CO
bubbles
can
capture
more
nitrogen
from
the
molten
steel.
and the peroxidation of molten steel can be reduced. What is more, more CO bubbles can
Figure3.3.Weight
Weightchange
changeofofthe
the
steel
in molten
bath
with
different
C content
and different
stirring
Figure
steel
barbar
in molten
bath
with
different
C content
and different
stirring
intensity
of(a)
the
meltCbath
stirring
havestirring
a stirring
significant
effect on the melting of the scrap.
intensity:
different
(b)
different
intensity.
intensity:
(a)
different
Ccontent;
content;
(b)
different
intensity.
bubbles can capture more nitrogen from the molten steel.
capture more nitrogen from the molten steel.
3. Impact Behaviors of Gas Jet in Liquid Steel
3. Impact Behaviors of Gas Jet in Liquid Steel
3. Impact Behaviors of Gas Jet in Liquid Steel
InIn
SCPI-COMG,
thecarbon
carbon
powder
injection
is a dilute
and therefore,
SCPI-COMG, the
powder
injection
is a dilute
phase phase
convey,convey,
and therefore,
In
SCPI-COMG,
the
carbon
powder
injection
is
a
dilute
phase
convey,
and
therefore,
thethe
gas
jetjetplays
roleininimpacting
impacting
stirring
the molten
bath.
As4 Figure
gas
playsaa main
main role
andand
stirring
the molten
bath. As
Figure
shows, 4 shows,
the gas jet plays a main role in impacting and stirring the molten bath. As Figure 4 shows,
in order
totoinvestigate
theimpact
impact
behaviors
of jets
gasinjets
in liquid
in EAF steelmaking,
in order
investigate the
behaviors
of gas
liquid
steel insteel
EAF steelmaking,
in order to investigate the impact behaviors of gas jets in liquid steel in EAF steelmaking,
geometricmodel
model of
liquid
steelsteel
was was
built built
on theon
basis
the water
model
thethe
geometric
of gas
gasjets
jetsinin
liquid
theofbasis
of the
water model
the geometric model of gas jets in liquid steel was built on the basis of the water model
experimentresults
results and
and relative
research
[22].[22].
In this
study,
a mathematical
model was
experiment
relative
research
In
this
study,
a
mathematical
model
experiment results and relative research [22]. In this study, a mathematical model was
built was
built to predict the formula of the axis of the gas jet in liquid steel.
built
to predict
the formula
theofaxis
gasliquid
jet insteel.
liquid steel.
to predict
the formula
of theofaxis
the of
gasthe
jet in
Figure 4. Geometric model of the gas jet in liquid steel [23].
Figure
4. Geometric
jetin
inliquid
liquidsteel
steel
[23].
Figure
4. Geometricmodel
modelof
of the
the gas
gas jet
[23].
Metals 2023, 13, 1602
5 of 15
3.1. Assumptions
(1)
(2)
(3)
(4)
The gas jet in liquid steel is regarded as a stable and incompressible fluid.
There are only mass and momentum exchanges between the jet and the surrounding liquid.
The momentum of the gas jet in liquid steel is conserved in the horizontal direction.
The transient variation of the momentum of the gas jet in liquid steel in the vertical
direction is equal to the buoyancy of the jet.
3.2. Theoretical Modeling
As Figure 4 [23] shows, a microelement at the horizontal distance x (h − x) and x + dx
was regarded as a computing primitive, which is vertical to the jet axis. Based on the law
of conservation of mass, the following equation can be obtained.
Cg ρ g Av = ρ g A0 v0
(1)
where A and A0 are the jet sectional area at h − x and the exit of the injector, respectively;
v and v0 are the jet velocity at h − x and the exit of the injector, respectively; ρg is the gas
velocity; due to the entrainment of the jet, the gas jet in liquid steel in the molten bath
would become gas-liquid jet, and therefore, Cg + CL = 1, Cg and CL are the gas and liquid
volume fraction in the jet at h − x, respectively.
The momentum of the gas jet in liquid steel is conserved in the horizontal direction.
The following equation can be obtained.
ρm Av2 cos θ = ρ g A0 v20 cos α
(2)
where α is the angle between the axis of the injector and the horizontal direction; ρm is
the gas-liquid jet density calculated from ρg and ρL ; θ is the angle between the jet axis and
the horizontal direction.
The calculation formula is as follows.
ρ m = Cg ρ g + C L ρ L
(3)
As a result, the following equation can be obtained by combining Equations (1)–(3).
ρL − ρg vx
ρ L − ρm
=
ρm
ρ g v0 cos θ
(4)
The momentum of the gas jet in liquid steel is conserved in the vertical direction.
The following equation can be obtained.
d mvy = Fb
(5)
where m is the mass of the computing primitive at h − x; vy is the velocity component in y
direction at h − x and Fb is the buoyancy of the the computing primitive at h − x.
Fb = (ρ L − ρm ) gAds
(6)
where ds is the axis length of the computing primitive at h − x and it can be calculated by
the following equation.
dx
ds =
(7)
cos α
As a result, the following equation can be obtained by combining Equations (5)–(7).
dvy
d(ln m) (ρl − ρm ) g
+ vy
−
=0
dx
dx
ρm v cos α
(8)
Metals 2023, 13, 1602
6 of 15
Then, the following equation can be obtained by combining Equations (4) and (8).
dvy
ρL − ρg
d(ln m)
g
+ vy
−
=0
(9)
dx
dx
ρg
v0 cos θ
For the convenience of analysis, we have assumed the following dimensionless variables.
xr =
vr =
vy
y
vx
x
, yr = , v xr =
, vyr =
d0
d0
v0
v0
ρ g v20
v
m
, mr =
, Fr 0 =
v0
ρ g A0 v0
(ρ L − ρ g ) gd0
where d0 is the injector exit diameter and Fr’ is the modified Froude. Hence, the following
equations can be obtained.
dvyr
d(ln mr )
1
=0
+ vyr
− 0
dxr
dxr
Fr cos θ
mr =
cos θ
v xr
(10)
(11)
Based on Equations (10) and (11), the following Equation (12) can be obtained by
mathematical transformations.
1
d2 yr
= 0
Fr v xr cos θ
dxr2
(12)
According to the previous report, the following equation can be adopted in this study.
v xr =
K cos α
xr + K
(13)
where K is a constant.
Therefore, the following equation can be obtained by combining Equations (12) and (13).
1 xr + K
d2 yr
=
2
KFr 0 cos2 θ
dxr
(14)
According to the boundary conditions of Equation (14), the mathematical model
to depict the formula of the axis of the gas jet in liquid steel can be obtained.
1
1 3 K 2 sin 2α
0
yr =
x
+
x
+
KFr
x
(15)
r
2 r
2
KFr 0 cos2 θ 6 r
Therefore, for a gas jet in liquid steel, the axis of the jet in the molten steel can be
calculated by Equation (15) on the basis of the installed angle, the submerged depth and
the gas flow rate. For model validation, the theoretical model was also verified by the water
model experiment (Figure 5).
3, 1602
KFr cos θ  6
Metals 2023, 13, 1602
2
2

Therefore, for a gas jet in liquid steel, the axis of the jet in the molten steel can be
calculated by Equation (15) on the basis of the installed angle, the submerged depth and
7 of 15 by the
the gas flow rate. For model validation, the theoretical model was also verified
water model experiment (Figure 5).
Penetration distance (mm)
400
350
300
250
200
Theoretical model
Water model experiment
150
100
100
120
140
160
180
200
Gas flow rate (NL/min)
Figure 5.5. Comparison
inject
distance
between
the the
theoretical
model
values
and and the
Figure
Comparisonofofthe
thehorizontal
horizontal
inject
distance
between
theoretical
model
values
the water
model
experimentresults.
results.
water
model
experiment
3.3. Analysis of Impact Behaviors of Gas Jet in Liquid Steel
3.3. Analysis of Impact Behaviors of Gas Jet in Liquid Steel
In EAF steelmaking with SCPI-COMG, the injector is under the molten steel level
EAFof
steelmaking
withwhich
SCPI-COMG,
thethe
injector
is profile
under and
the molten
steel level in
in theInrange
500 to 700 mm,
depends on
furnace
the diameter
the
range
of 500 toinjector
700 mm,
depends
the furnace
and thequantity
diameter of the
of the
submerged
exitwhich
is about
12 mm.onTherefore,
the profile
dimensionless
of the submerged
depth
yr is
is about
in the range
of 40
to 60 approximately.
submerged
injector
exit
12 mm.
Therefore,
the dimensionless quantity of the subAccording
experimental
results,
the vertical impact depth reaches 700 mm,
merged
depthto
yrthe
is in
the range of
40 towhen
60 approximately.
the maximum
horizontal
impact distanceresults,
does notwhen
exceedthe
600vertical
mm, which
is much
smaller
According
to the experimental
impact
depth
reaches 700
than
the
actual
diameter
of
the
electric
arc
furnace
melt
pool.
Therefore,
the
actual
melt
mm, the maximum horizontal impact distance does not exceed 600 mm, which is much
pool diameter will not affect the penetration depth of the jet.
smaller than the actual diameter of the electric arc furnace melt pool. Therefore, the actua
Figure 6a [23] shows the axis trajectory of the gas jet in liquid steel with different
melt
poolangles.
diameter
will
affect
penetration
depth
the jet. inject distance
◦ , theof
installed
It can
benot
found
thatthe
with
0◦ ≤ α ≤ 20
horizontal
Figure
6aα [23]
shows The
the change
axis trajectory
of the
gas jetininthe
liquid
increases
with
increasing.
trend is more
obvious
rangesteel
of 0◦ with
to 10◦different
.
◦
installed
It can20be, the
found
that with
0° distance
≤ α ≤ 20°,decreases
the horizontal
distance inWhen
α isangles.
larger than
horizontal
inject
with α inject
increasing.
Hence, inwith
industrial
applications,
installed
angle
is about
10◦ . Certainly,
the effect
creases
α increasing.
The the
change
trend
is more
obvious
in the range
of 0° to 10°
of the installed
anglethan
on the20°,
erosion
the refractory
was
also taken
into account.
When
α is larger
the of
horizontal
inject
distance
decreases
with α increasing
Figure
6b [23] shows
the axis trajectory
of the gas
jet inisliquid
differentthe
gaseffect of
Hence,
in industrial
applications,
the installed
angle
aboutsteel
10°.with
Certainly,
flow
rates.
It
can
be
found
that
the
inject
distance
increases
with
the
gas
flow
rate
increasing.
the installed angle on the erosion of the refractory was also taken into
8 ofaccount.
15
With the same installed angle and the same injector exit diameter, the jet velocity at the exit
Figure 6b [23] shows the axis trajectory of the gas jet in liquid steel with different gas
of the injector could be increased by the larger gas flow rate. Therefore, both the horizontal
flow
rates.
It can
be found
thesubmerged
inject distance
increases with the gas flow rate increasand the
vertical
inject
distancethat
of the
are larger.
ing. With the same installed angle and the same injector exit diameter, the jet velocity at
the exit of the injector could be increased by the larger gas flow rate. Therefore, both the
horizontal and the vertical inject distance of the submerged are larger.
Figure 6.ofAxis
of gas steel
jet in liquid
[23]. (a) Different
installed
angles
= 500 Nm3 /h.
Figure 6. Axis trajectory
gastrajectory
jet in liquid
[23]. steel
(a) Different
installed
angles
withwith
Q =Q 500
◦
(b) gas
Different
flow
rates
flow gas
rates
with
α =with
10°.α = 10 .
Nm3/h. (b) Different
4. Influence of the Gas-Solid Parameters on the EAF Steelmaking Process
Based on the previous studies [24–27], the materials and energy balance model of
EAF steelmaking with SCPI-COMG were built by combining the material balance, the en-
Metals 2023, 13, 1602
8 of 15
4. Influence of the Gas-Solid Parameters on the EAF Steelmaking Process
Based on the previous studies [24–27], the materials and energy balance model of EAF
steelmaking with SCPI-COMG were built by combining the material balance, the energy
balance and the chemical equilibrium (shown in Figure 7). These newly built models were
tested in the case of a commercial 50-ton EAF with SCPI-COMG. The results of the theoretical calculation were in accord with the results of the industrial production (listed in Table 2),
which could demonstrate that the materials and energy balance model was reasonable.
In this study, these two models were employed to investigate the effect of the gas-solid
parameters on the key technical parameters of EAF steelmaking.
Table 2. Comparison between the measured averaged values and the calculated averaged values
of theoretical model.
Label
Carbon Powder
Consumption (kg/t)
Power Consumption
(kWh/t)
O2 Consumption
(Nm3 /t)
001
Calculated
Measured
12.0
11.7
380.9
385.5
27.7
28.3
002
Calculated
Measured
16.0
16.3
369.1
365.3
33.1
34.2
003
Calculated
Measured
20.0
20.1
358.5
356.2
36.3
35.2
004
Calculated
Measured
23.0
22.7
354.7
357.6
39.5
42.6
005
Calculated
Measured
28.0
27.6
350.8
350.2
44.9
43.6
Calculated
Measured
32.0
32.3
348.3
343.2
49.2
47.3
0061602
Metals 2023, 13,
(A)
9 of 15
(B)
Figure 7. The materials and energy balance system model of EAF steelmaking; (A) materials balance
Figure 7. The materials and energy balance system model of EAF steelmaking; (A) materials balance
system model, (B) energy balance system model.
system model, (B) energy balance system model.
4.1. Variation
Variation Tendency
Tendency of
of the
the Molten
Molten Slag
Slag and
andthe
theOff-Gas
Off-GasVolume
Volume
4.1.
Figure 88 shows
shows the
the effect
effect of
of the
the carbon
carbon powder
powder quantity
quantity on
on the
the molten
molten slag
slag in
in EAF
EAF
Figure
steelmaking
with
SCPI-COMG.
The
quantity
of
the
molten
slag
increases
with
the
carbon
steelmaking with SCPI-COMG. The quantity of the molten slag increases with the carbon
powder quantity
quantityincreasing.
increasing.The
Thequantity
quantityof
ofthe
themolten
moltenslag
slagisis82.33
82.33kg/t
kg/t when
when the
the carbon
carbon
powder
powder quantity
and
that
increases
to 89.54
kg/tkg/t
whenwhen
the carbon
powder
quanpowder
quantity isis10
10kg/t
kg/t
and
that
increases
to 89.54
the carbon
powder
tity is 40 is
kg/t.
The main
is thatisthe
ash
content
in the in
carbon
powder
is about
12.4%
quantity
40 kg/t.
The reason
main reason
that
the
ash content
the carbon
powder
is about
and almost
all of the
is removed
into theinto
molten
slag during
steelmaking
process.
12.4%
and almost
all ash
of the
ash is removed
the molten
slag the
during
the steelmaking
In addition,
after the increase
ash content,
order toin
ensure
alkalinity
the slag,
process.
In addition,
after theinincrease
in ashincontent,
orderthe
to ensure
theofalkalinity
lime
other
materials need
to be added
resulting
in anresulting
increase
of
theand
slag,
limeslag-making
and other slag-making
materials
needto
tothe
be slag,
added
to the slag,
theincrease
remaining
slagremaining
amount. slag amount.
in an
in the
Metals 2023, 13, 1602
powder quantity is 10 kg/t and that increases to 89.54 kg/t when the carbon powder quantity is 40 kg/t. The main reason is that the ash content in the carbon powder is about 12.4%
and almost all of the ash is removed into the molten slag during the steelmaking process.
In addition, after the increase in ash content, in order to ensure the alkalinity of the slag,
lime and other slag-making materials need to be added to the slag, resulting in9 of
an15increase
in the remaining slag amount.
Figure 8.
between
the the
quantity
of slag
quantity
of carbon
Figure
8.The
Therelationship
relationship
between
quantity
of and
slagthe
and
the quantity
of powder.
carbon powder.
steelmaking with SCPI-COMG can offer the reference basis data to optimize the cooperative operation between the smelting system and the dust-removal system in EAF
42
150
steelmaking.
40
125
39
off-gas volume
38
100
19
Volume (Nm3)
CO
CO2
41
Gas volume fraction (%)
Metals 2023, 13, 1602
As for the smelting off-gas, the addition of carbon powder and CO2 influences the offAs for the smelting off-gas, the addition of carbon powder and CO2 influences the
gas volume. With the carbon powder quantity increasing, the volume of the off-gas
off-gas volume. With the carbon powder quantity increasing, the volume of the off-gas
increases noticeably (shown in Figure 9). When the carbon powder quantity changed
increases
noticeably
(shown
Figure
9). When
the carbon
powder
from
3 /t to
from 10 kg/t
to 40 kg/t,
the in
total
volume
of off-gas
increased
from quantity
58.87 Nmchanged
3
3
3
3
3
10
kg/tNm
to 40
the total
of off-gas
increased
from
58.87
Nm
to the
147.50
147.50
/h,kg/t,
the volume
ofvolume
CO2 changed
from 22.98
Nm /t
to 61.54
Nm
/t /t
and
vol- Nm /h,
3
3
3 /t 22.98
the
of CO2from
changed
from
Nm
to It
61.54
Nm
/t and
umevolume
of CO changes
10.47 Nm
to 28.31
Nm/t3 /t.
can be
found
thatthe
the volume
volume of CO
3
3
of CO2 increased
by aNm
large
CO post-combustion
ratio,
a large
changes
from 10.47
/t margin.
to 28.31With
Nm the
/t. Itassumed
can be found
that the volume
of CO
2 increased
amount
of CO
dueassumed
to the CO CO
combustion
and meanwhile,
carrier of CO2
by
a large
margin.
With the
post-combustion
ratio,the
a powder
large amount
2 was formed
gas isformed
also a main
CO2combustion
. The volume and
change
of the off-gas
EAFis also a
was
duesource
to theofCO
andcomposition
meanwhile,
the law
powder
carrieringas
10 of 1
steelmaking
with
SCPI-COMG
can
offer
the
reference
basis
data
to
optimize
the
cooperative
main source of CO2. The volume and composition change law of the off-gas in EAF
operation between the smelting system and the dust-removal system in EAF steelmaking.
75
18
10
15
20
25
30
35
40
50
Quantity of carbon powder (kg)
Figure9.9.The
The
relationship
between
the power
consumption
and the
off-gas
and composi
Figure
relationship
between
the power
consumption
and the off-gas
volume
andvolume
composition.
tion.
4.2. Variation Tendency of the Power Consumption
Based on the
above analysis,
the SCPI-COMG
4.2. Variation
Tendency
of the Power
Consumptiontechnology can accelerate the melting
process of scrap by enhancing the carburization of molten steel. Furthermore, a great
Based
on the above
analysis,
technology
can accelerate
the melting
deal of
heat generated
by the
carbon the
andSCPI-COMG
oxygen reaction
can also accelerate
the smeltprocess
of
scrap
by
enhancing
the
carburization
of
molten
steel.
Furthermore,
a
great dea
ing rhythm and reduce power consumption. Figure 10 shows the variation tendency
ofthe
heat
generated
by thewith
carbon
and oxygen
reaction
can
also steelmaking
accelerate the
of
power
consumption
the quantity
of carbon
powder
in EAF
withsmelting
rhythm and On
reduce
powerit consumption.
Figure
10 shows
the variation
tendency
SCPI-COMG.
one hand,
can be found that
the power
consumption
decreases
with of the
the
quantity
of carbon powder
increasing.
Based
on the calculation
a 1 kg/t increase
power
consumption
with the
quantity
of carbon
powder inresults,
EAF steelmaking
with SCPI
COMG. On one hand, it can be found that the power consumption decreases with the
quantity of carbon powder increasing. Based on the calculation results, a 1 kg/t increase
in the quantity of carbon injected into the molten steel by SCPI-COMG would decrease
the power consumption by about 3 to 4 kWh/t. On the other hand, the decrease of powe
Metals 2023, 13, 1602
Metals 2023, 13, 1602
10 of 15
in the quantity of carbon injected into the molten steel by SCPI-COMG would decrease
the power consumption by about 3 to 4 kWh/t. On the other hand, the decrease of power
consumption is gradually reduced with the quantity of carbon powder increasing. The average decrease speed of the power consumption per ton of steel is about 3.6 kWh per kg
carbon powder when the quantity of carbon powder is less than 20 kg/t and that would
become 0.7 kWh per kg carbon powder when the quantity of carbon powder in the range of
30 to 40 kg/t. That is, the effective utilization efficiency of carbon powder decreases as the
quantity of carbon powder increases. With a large injection rate of the carbon powder,
the instantaneous ability to dissolve carbon powder in the molten bath is limited and hence,
a part of the carbon powder escapes directly from the molten steel into the furnace tank
before they are captured by the molten steel. Furthermore, the more carbon powder is
injected, the more carbon escapes into the furnace tank. Hence, the effective utilization
efficiency of carbon powder decreases with more carbon powder. Therefore, the injection
parameters of the SCPI-COMG technology should be adjusted and optimized according
11 of 15
to the actual smelting conditions during the EAF steelmaking process, such as the burden
design, the smelting stage and so on.
Figure 10.
between
thethe
power
consumption
and the
quantity
of carbon
Figure
10. The
Therelationship
relationship
between
power
consumption
and
the quantity
of powder.
carbon powder.
4.3. Effective Utilization and Burning Loss of Carbon Powder
4.3. Effective Utilization and Burning Loss of Carbon Powder
In this paper, the burning loss of carbon powder is defined as the carbon powder
In thisdirectly
paper, with
the burning
carbon
powder
is defined
powder
that
that reacts
CO2 andloss
O2 of
and
this part
of carbon
powderasisthe
notcarbon
captured
by
reacts
directly
CO
2 and
2 and this process
part ofwith
carbon
powder is
not captured
the molten
steel with
during
the
EAF O
steelmaking
SCPI-COMG.
Figure
11 shows by the
the relationship
between
the carbon
powderprocess
burning
lossSCPI-COMG.
and the quantity
of carbon
molten
steel during
the EAF
steelmaking
with
Figure
11 shows the
powder. It can
be found
whenpowder
the quantity
of carbon
powder
is less than
20 kg/t;
relationship
between
thethat
carbon
burning
loss and
the quantity
of carbon
powder.
the
burning
loss
rate
of
carbon
powder
with
O
is
almost
invariable
and
the
burning
2
It can be found that when the quantity of carbon powder is less than 20 kg/t; the burning
loss rate of carbon powder with CO2 decreases gradually with the increasing quantity
loss
rate of carbon powder with O2 is almost invariable and the burning loss rate of carbon
of carbon powder. In this range, with the carbon powder quantity increasing, the proportion
powder with CO2 decreases gradually with the increasing quantity of carbon powder. In
of carbon powder melting into the molten steel decreases and correspondingly, the power
this
range, with
the carbon
quantity
increasing,
consumption
decreases.
Whenpowder
the quantity
of carbon
powderthe
is inproportion
the range ofof20carbon
kg/t topowder
melting
intoburning
the molten
steel
decreases
andwith
correspondingly,
the power
consumption
de40 kg/t, the
loss rate
of carbon
powder
O2 increases gradually
and the
burning
creases.
When
the
quantity
of
carbon
powder
is
in
the
range
of
20
kg/t
to
40
kg/t,
the
burnloss rate of carbon powder with CO2 decreases slightly with the quantity of carbon powder
increasing.
demonstrates
that with
ofgradually
carbon powder
increasing,
ing
loss rateItof
carbon powder
withthe
O2 quantity
increases
and the
burningmore
loss rate of
and more
carbonwith
powder
out from
the molten
into the furnace
tankpowder
withoutincreascarbon
powder
CO2ran
decreases
slightly
withbath
the quantity
of carbon
carburization
and this that
part of
carbon
bypowder
O2 in theincreasing,
furnace tankmore
directly.
ing.
It demonstrates
with
the powder
quantitywas
of burnt
carbon
and more
However,
compared
with
the
carbon
and
oxygen
reaction
in
the
molten
steel
carbon powder ran out from the molten bath into the furnace tank withoutduring
carburization
the steelmaking process, heat generated by the combustion reaction between carbon powder
and this part of carbon powder was burnt by O2 in the furnace tank directly. However,
and O2 in the furnace tank can be utilized by the molten bath. Therefore, the speed
compared
with
the carbon
oxygen
reaction in the molten steel during the steelmaking
of the power
consumption
is and
gradually
reduced.
process, heat generated by the combustion reaction between carbon powder and O2 in the
furnace tank can be utilized by the molten bath. Therefore, the speed of the power consumption is gradually reduced.
Assuming the injection mass ratio CO2:O2 = 5.5; CO2 utilization rate of 80%; 98% O2
utilization rate; CO2 purity is 99%.The burning reaction between carbon powder and O2
and CO2 is as follows:
Metals
2023,
13,13,
1602
Metals
2023,
1602
11 of 15 12 of 15
Metals 2023, 13, 1602
Figure 11.
relationship
between
the carbon
loss
and the quantity
carbon
powder.of carbon
Figure
11.The
The
relationship
between
the powder
carbonburning
powder
burning
loss andofthe
quantity
powder.
Assuming the injection mass ratio CO2 :O2 = 5.5; CO2 utilization rate of 80%; 98% O2
Figure
11. rate;
The CO
relationship
betweenburning
the carbon
powder
burning
and the
o
utilization
purity is 99%.The
reaction
between
carbonloss
powder
and quantity
O
Based on the2 industrial application research, the melting down of carbon 2contents
powder.
and CO2 is as follows:
with different
carbon powder quantities
1 was measured and the corresponding effective
C
+
O2 = CO
utilization ratio of carbon powder melting
into the molten steel was also(16)
calculated
2
Based on the industrial application
research, the melting down of carbon c
(shown in Figures 12 and 13). When the quantity of carbon powder is less than 20 kg/t
Melting down carbon
(%) content (%)
Meltingcontent
down carbon
with
different carbon powder quantities
was
measured and the corresponding
e
+ the
CO2EAF
= 2CO
(17)quantity
the melting down carbon contentCof
molten bath is proportional to the
utilization
ratio ofand
carbon
powder
meltingratio
intoofthe
molten
steel was also
cal
of carbon
theapplication
effective
utilization
powder
Based powder
on the industrial
research, the
meltingcarbon
down of
carbonincreases
contents stably
(shown
inquantity
Figures
12carbon
and 13).
When
thethe
quantity
of
powder
less
Whendifferent
the
powder
iswas
in
range of
20carbon
kg/tcorresponding
to 40
kg/t, it is
can
be than
found
with
carbonofpowder
quantities
measured
and
the
effecthe
melting
down
carbon
content
of
the
EAF
molten
bath
is
proportional
to
theinq
that
with the quantity
of carbon
powder
increasing,
the melting
down
content
tive utilization
ratio of carbon
powder
melting
into the molten
steel was
alsocarbon
calculated
(shown
in
Figures
and
thethe
quantity
of carbon
powder
is less
20 kg/t,
of
carbon
powder
and13).
theWhen
effective
utilization
ratio
of carbon
powder
increases
creases
more
and12more
slowly
and
effective
utilization
ratio
of than
carbon
powder
dethe
melting
down
carbon
content
of
the
EAF
molten
bath
is
proportional
to
the
quantity
creasesthe
correspondingly.
When
quantity of carbon powder is in the range of 20 kg/t to 40 kg/t, it can be
of carbon powder and the effective utilization ratio of carbon powder increases stably. When
that with the quantity of carbon powder increasing, the melting down carbon con
the quantity of carbon powder is in the range of 20 kg/t to 40 kg/t, it can be found that with
creases
and powder
more increasing,
slowly and
the effective
utilization
ratio of
carbon
0.8 more
the quantity
of carbon
the melting
down carbon
content increases
more
and pow
creases
correspondingly.
more slowly
and the effective utilization ratio of carbon powder decreases correspondingly.
0.6
0.8
0.4
0.6
0.2
Measured value
0.4
0.0
0
10
30
20
Quantity of carbon powder (kg/t)
40
0.2
Measured value
Figure 12. The melting down carbon content with different carbon powder quantity in the industria
application.
0.0
0
10
30
20
40
100
Quantity of carbon powder (kg/t)
Measured value
ation ratio (%)
Utilization ratio (%)
Figure 12.
down
carbon
content
with different
carbon powder
inquantity
the indus-in the in
Figure
12.The
Themelting
melting
down
carbon
content
with different
carbonquantity
powder
80
trial
application.
application.
100
60
Measured value
80
40
20
60
0
10
20
30
Quantity of carbon powder (kg/t)
40
M
0.0
10
30
20
Quantity of carbon powder (kg/t)
40
12 of 15 in the in
Figure 12. The melting down carbon content with different carbon powder quantity
application.
100
Measured value
Utilization ratio (%)
Metals 2023, 13, 1602
0
80
60
40
20
0
10
20
30
Quantity of carbon powder (kg/t)
40
Figure 13. The rate of carbon powder melting into the molten steel with different carbon powder
quantity in the industrial application.
4.4. Effect of CO Post-Combustion on the Power Consumption
In EAF steelmaking, a large amount of CO is generated during the smelting process and these CO gas contains massive chemical latent heat, which is useful to reduce
the smelting energy consumption [28,29]. Actually, it is significant to enhance the CO postcombustion and improve the energy utilization rate of CO post-combustion. Figure 14a,b
show the relationship between the power consumption and the CO post-combustion ratio and the relationship between the power consumption and the energy utilization rate
of CO post-combustion, respectively. In Figure 14a, the energy utilization rate of CO postcombustion is assumed as 42%. With the CO post-combustion ratio increasing, the power
consumption decreases. A 1% increase in the CO post-combustion ratio would decrease
the power consumption by 0.76 kWh/t. In Figure 14b, the CO post-combustion ratio is
assumed as 55%. And with the energy utilization rate of CO post-combustion increasing,
the power consumption decreases. A 1% increase in the energy utilization rate of CO postcombustion would decrease the power consumption by 1.6 kWh/t. In EAF steelmaking
with SCPI-COMG, the quantity of carbon powder injected into the EAF steelmaking system
is far more than that in traditional EAF steelmaking. Hence, the utilization and optimization of CO post-combustion is of greater importance. Generally, the CO post-combustion
includes CO post-combustion in foaming slag and CO post-combustion in free space [30,31].
With CO post-combustion in free space, the heat generated by the reaction between O2
and CO above the molten bath is transformed into the molten slag layer by radiation and
convection and then the heat is transformed from the molten slag layer to molten steel.
In this heat transfer process, the energy utilization rate is only about 20% to 40%. With CO
post-combustion in foaming slag, the heat generated is directly transformed into molten
steel from the molten slag layer, which improves the efficiency of energy utilization noticeably. Therefore, in EAF steelmaking with SCPI-COMG, it is very important to enhance
the CO post-combustion, especially the CO post-combustion in foaming slag, to increase
the energy utilization rate and reduce the power consumption.
Metals 2023, 13, 1602
radiation and convection and then the heat is transformed from the molten slag layer to
molten steel. In this heat transfer process, the energy utilization rate is only about 20% to
40%. With CO post-combustion in foaming slag, the heat generated is directly transformed into molten steel from the molten slag layer, which improves the efficiency of energy utilization noticeably. Therefore, in EAF steelmaking with SCPI-COMG, it is very
13 of 15
important to enhance the CO post-combustion, especially the CO post-combustion
in
foaming slag, to increase the energy utilization rate and reduce the power consumption.
Figure 14.
14. The
Therelationship
relationshipbetween
betweenthe
thepower
power
consumption
and
post-combustion
parameFigure
consumption
and
thethe
COCO
post-combustion
parameters.
ters.
(a)post-combustion
CO post-combustion
(b) Energy
utilization
CO post-combustion.
(a)
CO
ratio. ratio.
(b) Energy
utilization
rate ofrate
COofpost-combustion.
5.
5. Conclusions
Conclusions
Some
carried
outout
to understand
the mechanism
of EAF
Somefundamental
fundamentalstudies
studieswere
were
carried
to understand
the mechanism
of steelEAF
making
with
SCPI-COMG.
An
induction
furnace
experiment
was
carried
out
to
investigate
steelmaking with SCPI-COMG. An induction furnace experiment was carried out to inthe
mechanism
of scrap melting
bymelting
molten by
bath
carburization
and fluid flow,
The mathvestigate
the mechanism
of scrap
molten
bath carburization
and fluid
flow,
ematical
model
of
the
axis
of
the
gas
jet
in
liquid
steel
was
built
to
analyze
the
impact
The mathematical model of the axis of the gas jet in liquid steel was built to analyze
the
characteristics
of gas jetofingas
liquid
and
the and
materials
balance balance
model and
energy
impact characteristics
jet insteel,
liquid
steel,
the materials
model
andbalance
energy
model
EAF steelmaking
with SCPI-COMG
were builtwere
and built
testedand
to study
influence
balanceofmodel
of EAF steelmaking
with SCPI-COMG
testedthe
to study
the
of
the
gas-solid
parameters
on
the
EAF
steelmaking
process.
influence of the gas-solid parameters on the EAF steelmaking process.
In the EAF steelmaking process using the SCPI-COMG, the carbon content of the melt
bath and the intensity of the melt bath stirring have a significant effect on the melting
of the scrap. The lower the melt bath carbon content, the slower the melt bath stirring, then
the slower the scrap melting rate. The smaller the carbon concentration gradient, the slower
the carburisation reaction speed. The lower intensity of bath stirring results in a lower
convective heat transfer coefficient, which reduces the heat transfer from molten metal
to scrap.
The mathematical model built to depict the formula of the axis of the gas jet in liquid
steel can well predict the axis trajectory of the gas jet in liquid steel. Based on the results
of this theoretical model, for a gas jet in liquid steel, with α ≥ 20◦ , the horizontal penetration
distance decreases with α increasing and with 0◦ ≤ α ≤ 20◦ , the horizontal penetration
distance increases with α increasing. Especially in the range of 0◦ to 10◦ , the change trend
is more obvious.
The materials and energy balance model of EAF steelmaking with SCPI-COMG
was in accord with the industrial application. Based on the results of these two models,
it can be found that with the carbon powder quantity increasing, the power consumption decreases, the quantity of the molten slag increases and the off-gas volume increases.
When the quantity of carbon powder is more than 20 kg/t, the effective utilization efficiency of carbon powder decreases as the quantity of carbon powder increases. The CO
post-combustion is useful to reduce the smelting energy consumption in EAF steelmaking.
Hence, with SCPI-COMG, it is very important to enhance the CO post-combustion, especially the CO post-combustion in foaming slag, to increase the energy utilization rate and
reduce the power consumption.
Author Contributions: The contributions of the authors are as follows: J.L.: Conceptualization,
Methodology, Project administration, Writing—Original Draft. G.W.: Conceptualization, Methodology, Writing—Review and Editing, Supervision. C.H.: Writing—Review and Editing, Supervision,
Software, Validation. All authors have read and agreed to the published version of the manuscript.
Funding: This research was funded by the National Nature Science Foundation of China
(No. 52274313, No. 52293392, No. 52004023 and No. 52074024) and Key R&D Projects of Jiangxi
Province 20214BBG74005.
Metals 2023, 13, 1602
14 of 15
Data Availability Statement: No new data were created or analyzed in this study. Data sharing is
not applicable to this article.
Conflicts of Interest: The authors have no relevant financial or non-financial interests to disclose.
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