Yin R. Metallurgical Process Engineering
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278 Metallurgical Process Engineering
of
'Ivand 'Ihis necessary for evaluating the intensity
of
BF smelting.
80
,--
- - - - - - - - - - - - - - - - -
-----,
I
•
2
•
4
•
6
5 •
•
7
•
8
•
9
•
\I
•
10.
40
L-
-----.J
3.5
,--
- - - - - - - - - - - - - - - - -
-----,
1?
3.0
~
~
2
.
5
·
•
50004000300020001000
2.0
L
O-----,-.,.L-,----,--,L..,----,-,J,...,-----,.,.L-,-------,-,-,-J
BF volume/m'
Fig
.8.25
Calculation ways comparison between two kinds of utilization
coefficient of BFs with different volumes
I- Sanming Steel No.2; 2- Laiwu Steel No.2; 3- Pangang No.3; 4
-R
aahe No.2;
5, 6
-Shou
gang Nos. 2,4; 7, 9
-Wuhan
Steel Nos . 4,5; 8
-Hoo
govens No. 6;
10- Baosteel No.3 ; II
-Sch
welgen No.7
Table 8.17 Comparisons
of
volume utilization coefficient n
v,
furnace hearth
area utilization coefficient
'lh, smelting intensity I" combustion intensity I,
and VIA
ofBFs
with
diff
erent volumes
Sanm ing Laiwu
Pangang Raahe
Shou- Shou-
Wuhan
Hoogovens
Wuhan
Baosteel
Schw
elgen
Item
Steel Steel
(2000) (2000)
gang gang Steel
(Jan.s-Sept.,
Steel
(2000)
(Jan.s-Aug.,
(2000) (2000)
No.3 No.2
(2000) (2000) (2000)
1998)
(2000)
No.3
1999)
No.2 No.2 No.2 No.4 No.4 No .6 No.5 No.1
BF vol·
350 750 1200 1255 1726 2100 2516 2678 3200 4350 4416
ume/m
3
Furnace
hearth
5.2 6.8 8.2 8.0 9.6 10.4 11.2 11.0 12.2 4.0 13.6
diame-
ter/m
Alm
2
21.24 36.32 52.81 50.27 72.38 84.95 98.52 95.03 116.9 153.9 145.27
Ij v
3.40 2.42 2.69 2.78 2.13 2.15 2.12 2.51 2.19 2.29 2.24
It'(m
3
'dr'
Ijh
56.00 49.97 61.1 2 69.50 50.70 53. 15 54. 14 70.73 59.80 64.80 68.10
It'(m
2
'dr'
VIA 16.48 20.65 22.79 24.97 23.85 24.72 25.45 28.18 27.37 28.26 30.40
1,
1.73 1.28
1.33
1.24 1.04 1.1\ 1.09 1.24 1.13 1.05 1.12
It'(m
3
'dr'
1,
28.50 26.43 30.22 30.90 24.85 27.32 27.84 35.0 1 30.96 29.76 34.10
It'(m
2
'dr'
Chapter 8 The Structure and Mode
of
Steel Plant Process
279
2. Effective arrangement
of
energy exchange, enhancing
of
energy conversion
function.
lronmaking process is a major procedure
of
energy consumption in steel manu-
facturing process. Taking some advanced integrated steel plants as example,
ironmaking procedure consumes 68.5%
of
the total energy
of
the whole steel
plant consumption including about 10.1% for the sintering, about 7.1% for coking,
and the balance about 51.4% for BF itself.
Energy saving is very important for BF. Based on optimizing the burden
of
coals and ores, the high blast temperature, oxygen enriched blast, pulverized coal
injection, high top pressure, reducing slag ratio, and intensifying smelting should
be applied comphensively, in order to save energy. However, BF functions should
be further broadened to the area
of
effective energy conversion.
BF is a counter-current bed reactor. Cold ferruginous matter with carbon are
continuously charged into the BF from the top. The descending burdens are
heated up and reduced gradually by the ascending gas, and descend to the soften-
ing zone, the slag has to separate with iron. In the course
of
BF smelting, the
combustion
of
such fuels as cokes, pulverized coals generates a great amount
of
gases, almost more 2t BF gases are produced per tonne hot metal. Apart from the
portion
of
gases (about 35%
of
all the gases produced by BF) consumed for hot
blast stove, there are still a large quantity
of
BF gases to be utilized.
It
might be
said that the biggest output
of
BF is the gas, instead
of
hot metal reflecting BF's
fundamental attribute
of
mass-energy conversion. BF gases have chemical energy,
thermal energy as well as kinetic energy. The BF gas kinetic energy comes from
the kinetics
of
blast and fuel combustion. Therefore, the usage
of
BF gas should
include thermal, chemical (for instance, steams generating, electricity) and kinetic
energy (like electricity generating by top pressure recovery turbine), so as to make
full use
of
the energy.
Actually, the
hot
metal
produced
by
SF
is
also
one
of
the
modes
of
mass-energy
conversion.
The
temperature
and
[C], [Si], [S]
contents
of
hot
metal
will all
have
an
impact
on
the
efficiencies
of
mass-energy
conver-
sion
in
the
following
steelmaking
process,
such
as
the
scrap
usage
effi-
ciency,
amount
and
recovery
rate
of
BOF
gas
,
the
consumption
of
flux ma-
terials
in
steelmaking
and
slag
quantity.
Meanwhile,
the
slag
ratio
of
BF
smelting
also
reflects
the
process
of
mass-energy
conversion
.
Producing
cements
with
SF
granulating
slag
is
favorable
for
reducing
energy
con-
sumption
and
environmental
load
of
the
whole
society
as
compared
with
common
cement
manufacturing
process
.
Slag
thermal
energy
may
also
be
utilized
.
Of
course,
this
does
not
mean
encouraging
BF to
increase
slag
quantity,
but
on a
whole,
to
make
use
of
beneficiated
materials
should
be
encouraged
to
reduce
slag
ratio.
Great attentions must be given to how to give full play to mass-energy conver-
280
Metallurgical Process Engineering
sion functions, particularly function
of
energy conversion. For instance, the issues
about TRT power generation with BF top pressure, generating power by BF gas-
stream boiler-steam turbine, by BF gas-gas turbine, and by waste heat boiler-
steam turbine must all be considered. These are worthy to investigate under con-
ditions both
of
large integrated steel plants and many smaller BF steel plants in
China.
3. Continuous operation and process continuation
ofBF
ironmaking.
In the discussion
of
the basic characteristics
of
BF operation, it was mentioned
that the BF process has the natures
of
continuous production process (countercur-
rent, continuous moving reaction bed operation) and the batch iron tapping (or
batch iron ladle transporting). Therefore, the essence and core
of
BF natures are
its continuity. This is very much noteworthy.
If
the time- space scale enlarged,
people would have a new and in-depth cognition
of
operation continuity and
process continuation for BF ironmaking.
From the perspective
of
time scale
of
BF process, the continuity
of
BF smelting
is first reflected in smooth running
ofBF
and corresponding delay ratio (particularly
the unscheduled delay ratio) or calendar operation rate, the annual BF calendar op-
eration time should reach
255
~360
days by the aid
ofa
series
of
technical and man-
aging measures. So, the BF delay ratio should not be higher than
1.3%
~
1.5%,which
would deal with a series
of
related measures for smooth running, particularly the
equipment reliability and BF operation expert system. While the time scale
of
BF
operation further broadens, it would surely deal with the BF campaign of a genera-
tion. In the 21st century, the target
of
the generation campaign
of
a new large BF
should be set at
20
~25
years, the small or medium BF should be
12
~
15 years. So,
technical measures, like usage
of
soft water, water treatment technique, copper cool-
ing stave, top charging system, wall gunning technologies, refractory for furnace
hearth and bottom, must be strengthened accordingly.
If
the space scale
of
BF process continuation enlarged, it would be cer-
tainly thought
of
the related continuation
of
BF-BOF
-CC
-Hot
rolling,
particularly the long route
of
BF
-hot
metal pretreatrnent
-r-BOf
-r-secondary
metallurgy - continuous casting. This would lead to a topic about
BF's
influ-
ence on optimizing interface techiques between ironmaking and steelmaking
as well as steelmaking and continuous casting. The trend
of
further restruc-
turing
of
steel manufacturing process should be taking full advantages
of
the
continuity
of
BF operation to elevate the continuation degree
of
chemical
metallurgical processes and even to solidification. Thus, the"one after an-
other" matches
ofBF
-BOF production capacities, the matching and optimiza-
tion
of
BF iron ladle and the BOF hot metal charging ladle, including the
capacity matching
of
BF iron ladle, BOF hot metal charging ladle and BOF
(for a BOF with more than 150 t, BF iron ladle and the BOF hot metal
amount charging ladle should preferably have the same capac ity as the hot
Chapter 8 The Structure and Mode
of
Steel Plant Process
281
metal charged into the BOF) should be seriously studied. And also attentions to
increase
of
turnover speed
ofBF
iron ladle, particularly the shortening
of
turnover
time
of
empty ladle, as well as rational selection
of
hot metal pre-treatment and its
layout must be paid.
It
appears that the matching "one after another" for
of
BF-
BOF capacities should be based on the minutes scale
of
flow rate but not scale
of
annual production. In the meantime, the drawbacks
of
mixer, the irrationality
of
hot metal pretreatment and transporting with torpedo car, even the unnecessity
of
individual pre-treating station between the BF and BOF would be further judged.
In order to enhance the continuation degree
of
BF
-BOF
-CC
section, the inte-
grated technologies including, matching up one BF with one or two BOFs (de-
pending on BOF tonnage), using one ladle both for BF iron receiving and BOF
hot charging, hot metal pretreating in the steelmaking workshop by simple way
without ladle shifting, hot metal series pretreatment (desulphurization in ladle,
desiliconization and dephosphorization in coverter and then slag cut-oft), as well
as rapid blowing in steelmaking BOF should be practised orderly. These opera-
tions are reflected in a rational layout and the time scheduling diagram in rhythm
and harmony. Such engineering design would certainly raise the level
of
continua-
tion quasi-continuation and compactness to realize the integration
of
cost, quality,
efficiency and benefits.
8.5.3 Principles about engineering design in optimizing steel
plantprocess structure
Since the 1980s, the restructuring
of
most steel plants in the international steel
industry has used continuous casting to connect-coordinate the chemical metal-
lurgical processes with physical processes
of
metallurgy, and generally they tried
their best to use fully continuous casting system to coordinate the production
process
of
the entire steel plant. Therefore, to process optimization
of
steel plant
structure special attentions should be given to the following aspects:
1. To determine the outline
of
product mix
of
each steel plant (not steel com-
pany group) by requirment from the market distribution, market demands and
investment benefit assessment, and then analyzing the rational capacity range
of
modern rolling mills related with producing these products. It is necessary to pay
attention to the rational scale size
of
every hot rolling mill and the compatibility
of
different types
of
mills (for instance, bar mill and wire mill have better com-
patibility, thin strip mills
of
different widths have better compatibility, but no
compatibility between hot strip mill and bar/wire mill, and no compatibility
of
strip mill with seamless tube mill too). The compatibility
of
different kinds
of
mills should deal with the rational selection for BF, BOF or EAF, hot metal treat-
ment, secondary metallurgy and caster, then it influences the product mix and
process structure and rational economic scale.
282
Metallurgical Process Engineering
2. To analyze the capacity
of
caster (including caster type, strand section,
strand numbers) and select the connecting
-matching
relation
of
continuous
caster with hot rolling mills. The coordinating-buffering relations
of
tempera-
ture,
of
time (rhythm) and
of
mass flow, and transporting pattern and ways
must be considered to realize the optimum layout
of
steelmaking
plant-
rolling plant by making full use
of
energy and time based on the principle
of
convenience and rapidity. Generally, to strive for directly link the slab run-out
rolling table or cooling bed run-out line with entry rolling table
of
reheating
furnace in the rolling workshop will take the cranes or other transporting de-
vices away as possible.
3. To analyze and select optimized-coordinated interface techniques among
steelmaking furnace
-secondary
metallurgy
-continuous
caster to realize quasi-
continuous and compact linkage. The coordinating-buffering
of
procedures and
devices, and the tramsversely exchanging
of
running slabs with coordination
among different types
of
casters should be noticed. To optimize the layout (par-
ticularly the locations
of
steelmaking furnace-main refining devices-continuous
casters) in order to improve the optimization, smoothness and coordination
of
steelmaking workshop mass flows is necessary condition.
4. To determine the volumes and sets
of
SFs based on the rational scale and
process structure
of
the steel workshop. (Generally
2
~3
is the target, sometimes I
SF running). Interface technique between SF and SOF based on product mix, and
the layout
of
SF
-hot
metal pretreatment
-SOF
would be fixed to promote the
dynamic-orderliness, quasi-continuation and compactness
of
high temperature
mass flow.
5. On the base
of
above thoughts, to analyze and calculate the longitudinal co-
ordination and transverse compatibility among
SF
-hot
metal pretreatment-
steelmaking - secondary metallurgy - continuous casting - reheating -
continuous rolling in one steel complex. The process rationalization
of
different
types
of
steel products, and the effective production
of
different but compatible
steel products in the same plant would be organized in a structural system with
comprehensive competitiveness. This is a complex design system integrating
market demands, technical progress, economic benefits and environmental bene-
fits.
This proposition,
if
implemented as the technical guidance in manufactaring-
process design, would form the following strategic principles for optimizing:
I) Matching principle
of
mass flow rate in minute scale among procedures or
devices;
2) Stability principle ("convergence") for temperature-time
of
mass flow in the
process;
3) Continuation/quasi-continuation principle
of
mass flow in the process;
4) Principle
of
high efficient conversion and full recovery
of
materials and en-
Chapter 8 The Structure and Mode
of
Steel Plant Process 283
ergy in the process;
5) Compactness principle of time and space in the process;
6) Principle
of
compact and simple for process network structure (general
layout).
8.6
Modern
Steel Plant Models
By studying the control on multi-factor mass flow in a steel plant, discussing
the operation dynamics
of
steel plant and analyzing the steel plant structure,
particularly in consideration of the behavior and phenomena of dissipation in
steel manufacturing process, to minimize matter dissipation, energy dissipation
and time-space dissipation by optimizing multi-factor mass flow in time-space
and efficiency, with observing the characters
of
restructuring
of
different types
of
steel plant in various countries, in addition, to enhance the market competi-
tiveness of steel plant and sustainability in the foreseeable future, the following
steel plant models should be considered or recommen ded.
8.6.1 Large integratedsteel plants
A.
Plant
producing plate
and
strip totally
L Continuous rolling
arge
_Secon~ary
_Thin
slab
castet:....
mill
(0
8
-4
mm
{
converter refimng (x2 strands) . ,
Large Hot metal ( x2) 2.5- 2,8 Mtfa)
SF - pretreat-
( x 2_3) me
,ilt
( mainly Large _ Secondary _ Slab caster _ Wide strip
De-S) converter refining (
x
2,4
hot rolling mill
(x2)
strands)
(2-l2.7/25.4mm,
3.5-5.0 Mt/a)
Rational capacity: 6
-8
Mt/a.
Extension products: Cold-rolled sheets, galvanized plates, tin-coated plates,
color-coated plates, electrical sheets, welded pipes, etc.
B. The comprehensive
product
s type
Large
Slab
Wide strip
BOF
Secondary
caster
rolling mill
(x2)
refining
(x 2,4 strands)
(2-12.7/25.4 mm
4.0- 5.5 Mtla)
Large
Hotmetal
BF
- pretreatment
Profile Rail-structural
(x2- 3)
(mainly De-S)
{ bl
,"
k
steel mill
Medium
caster (0.
6-
I Mtla)
80F
Secondary
(x 2)
refining
Round Seamless pipe
billet - rolling mill
caster
(0.5- 0.7 Mtla)
. Quality barrolling
Billet caster _ mill (¢12
-40/60mm,
(x 1,6strands) 0.8-1 Mt/a)
284
Metallurgical Process Engineering
Rational capacity: 6
-8
Mt/a.
Extension Products: welded pipe, cold rolled sheets, galvanized plates, colored
plates, etc.
C.
Flat
product
s
and
th
eir
extension
products
type
Thin slab casting-rolling mill
{
( x
2 strands) (0.8-4 mm,2.5-Z.8 Mt/a)
Large Hotmetal Large Secondary
BF - Pretreatment convert
er-
refining Plate mill
( x 2) (mainly De-S) ( x 3) slabcaster (3300 _4200 mm
(x 1,1strand) 1- 1.2 Mtla) ,
Rational capacity: 3.5
-4
Mt/a.
Extension products: welded pipe, cold rolled plates, galvanized plates, colored
plates, UOE pipes, etc.
D. Mixed type
Large Hot metal Large Secondary Thin slab casling-rouing miu
BF p retreatment
-c
onverter- - refining - (2 strands) (1-4mm,2.S
-2
.8
MtJa)
(x 2) (mainlyDe-S) (x 2)
LScrap EAF Secondary
(Hot metal
rrr'{ x
I)-refining-
co-char
ge)
( x I )
Rational capacity: 3.5
-3
.8 Mt/a.
Extension products: welded pipes, cold-rolled plates, galvanized plate, color-
coated plates, etc.
E. Super-large type of strips (e
xpandable
type in the future,
and
possible for
producing medium or heavy plates is reserved)
SI b
Strip rolling mill
a caster _.
__
. (1.2-1 2.5 mm
Super- Large S d
{(
2strandS) 3-
35
Mtla)
I
SF-
total hot metal_ BOF _ econ ary .
arge pretreatment
(3)
refining Wide strip hot rolling
(x 2) x Slab caster
(x 2,4 strands) mill (2 - 25.4 mm,
"De-S,De-Si ,De-P" 5- 5.6 Mt/a)
Rational capacity: 8
-9
Mt/a.
Extension products: cold-rolled sheets, galvanized plates, color-coated plates,
welded pipes, electrical sheets, large welded H-section steel.
Chapter 8 The Structure and Mode
of
Steel Plant Process
285
8.6.2 Steelplants with small or medium
BF
A. Specializing long
products
type
Hot bar rolling
De-S Billetcaster
__
mill
(I/>
12- 40 mm.
e. Smaller Argon { (x
I)
0.6,0.8,1 Mt/a)
Small or
ror part .
medium
BF-
of
-converter-blowl~g
High speed wire
(x2-4)
hot
(x2-3)
and
"':'lre
. mill(1/J5.5-16mm,
metal feeding BIllet caster 0.4 _ 0.5 mt/a,
(x
I)
0.7 - 0.8 Mt/a)
Rational capacity:
1.2
~
1.8 Mt/a.
B. Specializing medium plate type
Small or Large or
medium
BF--
Hot me!al . medium
(x
2-4)
pre-desulfurization BOF
( x I)
Rational capacity: I
~
1.2 Mt/a.
C. Comprehensive
products
type
Medium plate
rolling mill
Secon~ary
__
Slab
__
(4.5-50mm
,
refining caster 3300- 4200 mm,
1-
J.2 Mt/a)
Small or
medium
BF
(x
2-4)
De-S for
part
of
hot
metal
Large or Slab Medium plate
medium Secondary .
mill(4.5
~50mm
BOF
--
refining
--ca:~er
--2600~3300mm:
( x I)
()
0.6~1
Mt/a)
Bar rolling mill
-[
(1/J
12
-40mm,
Argon . 0.6 - I Mt/a)
Smallre blowing BIllet
BOF
--and
~ire--
ca
xs~r
Wire high
c-2) feeding
()
speed mill
(1/>5.5
-16mm,
0.4 - 0.7 Mt/a)
Rational capacity:2.1
~
2.
7 Mt/a.
8.6.3
EAF
process steelplants
A. Long
products
type
1.
EAF
__
serceofinndl'nagry
__
Billet caster
(
xl)
(xl)
(x 1)
Rational capacity:
0
.8
~
1.0 Mt/a.
Bar continuous
rolling mill
(carbon steel, low-alloy
steel 1/>12-40 mm)
286
Metallurgical Process Engineering
EAF
Secon~
ary
Billet caster Wire high speed mill
2.
(x
I)
--
refinmg
--
( x 1)
--
(carbon steel, low-alloy
( x 1) steel
rp5
.5- 16/22mm)
Rational capacity:
O.4
~
O
.
7 Mt/a.
B.
Strip
type
Secondary
EAF
__
refining
__
Thin slab continuous casting_ rolling mill
(x
I,
( x 2)
(x
2) ( x 2 strands) thickness 1- 8 mm)
Rational capacity:
1.6
~2
.2
Mt/a.
Extension products: cold-rolled sheets, galvanized plates, color-coated plates,
welded pipes, etc.
C. M
edium
pl
ate
type
EAF
( x
I)
Secondary
refining
__
Slab caster
(
x2
) (
xl
)
(3300- 4200 mm(x I),
Mediumplate miIl
4.5-
50mm)
Rational capacity:
O
.
8
~
1Mtla.
D. Seamless pipe type
l EAF
__
Secondary
__
Round billet caster Seamless pipe
(1/>
:::;;:
140 mm)
.
(x
I) refining ( x I) rolling mill
Rational capacity:
O
.
5
~O
.7
Mt/a.
2 EAF
__
Secondary
__
Round billet caster Seamless pipe
(I/>
<140 mm)
. (> I) refining ( x I) rolling mill
Rational capacity:
O
.
1
2
~O
.
20
Mt/a.
E. Alloy steel long
products
type
Alloy steel bar rod tandem
{
Alloy steel bloom ca
ster-
rolling mill
EAF
S
d
(xl)
(rjlI6
-75mm,0
.5-0.8Mtla)
econ ary
1.
( x I) - refining Fast forging machine
Ingot casting
-{
(20- 30ktla)
(or cast bloom+ESR) Precision forging machine
(30- 40 ktla)
EAF Secondary Alloy steel biJIetcaster
2.
(x
I) - refining
--
(x
I)
Alloy bar/wire
rolling mill
(rjl16
- 75 mm/rp5.5- 22 mrn,
0
.5-
0.7 Mtla)
Chapter 8 The Structure and Mode of Steel Plant Process
287
F. Stainless steel plate type
1 EAF
---.f..onverte.!....-
Vacuum _ Slab
caster_
Steckel mill
.
(xl)
(xl)
refining
(x
l) (thickness2-8/12.7mm)
Rational capacity:
O.8
~
1 Mt/a.
Extension products: cold-rolled stainless thin sheets and their deep processing
products
EAF Converter Vacuum
2.
(x
I) -
(x
I) - refining
Slab caster Hot strip rolling mill
(x
1) - (thickness
2-12.7
mm)
Rational capacity: 1
~
1.5 Mt/a.
Extension products: cold-rolled stainless sheets and deep processing metals.
In conc1ussion, steel plant restructuring should be guided by the following as-
pects:
• Market orientation; product mix should be determined according to market
demands (particularly for the regional markets);
• The region, where the plant is situated, should have comparable and location
advantages in market, transportation, resources, energy, etc.;
• The steel plant should be well equipped with rational scales and advanced
manufacturing processes for different kinds
of
steel products;
• Coordination-optimization among procedures and devices inside the mass
flow
of
the manufacturing process;
• For different types
of
steel products, consideration should be given to the
compatibility
of
the transverse flow between casters and mills;
• Optimizing the match numbers
of
caster and mill to each other;
• The number
of
BF should not be too many (normally, 2 to 3 is suitable), the
number
of
steel making workshops should not be more than 2, which would fa-
cilitate the optimization
of
railway transporting network;
• Togive play to the energy conversion function
of
a steel manufacturing proc-
ess in order to make full use
of
energy;
• To give play to the environment friendly function
of
steel plants, so as to
build up eco-industrial chains based on the local conditions.
8.6.4 Steelplant
and
consolidatedsteel corporation (group)
Steel plants have entered a restructuring and industrial upgrading era. As far
as an individual steel plant is concerned, there should be a rational economic
scale.
If
a steel plant's scale is smaller than that scale, it would never be able
to produce quality, and low-cost products with modern technologies and
equipment, nor to gain profit. However, for the scale
of
an individual steel