Yin R. Metallurgical Process Engineering
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38 Metallurgical Process Engineering
importance with cognition
of
the characteristics
of
manufacturing process, i.e.
complexity and integrity. This is because as compared with functions and per-
formance
of
each unit, the manufacturing process can obtain new function and
performance through changing certain relations among units. However, the dy-
namic operation
of
the process
of
certain structure will present some characteris-
tics under constricted boundary conditions. In the manufacturing process, a cer-
tain
structure and dynamic operation rule can be found in processes at different
levels with a viewpoint
of
engineering science.
2.5 Classification
of
Manufacturing Processes
The manufacturing processes in the process manufacturing industry can be classi-
fied according to the functions
of
the manufacturing process, the structures
of
the
manufacturing process, the modes
of
the running behavior as well.
Of
course
there are still other possible ways to classify (Gruhn, 1983).
2.5.1 Classification according tofunctions
In general, the functions
of
the manufacturing process appear to take following
sorts:
• Function
of
matter transformation. Function
of
matter transformation is re-
ferred to changing the properties and performance
of
the substances by physical,
chemical or biochemical reactions in the manufacturing process.
• Function
of
energy supply, storage, and conversion. In the manufacturing
process, the running
of
the mass flow is proceeded by effecting and supporting
of
energy consumption, so the manufacturing process must be provided with the
function
of
the energy supply, storage, and conversion.
• Function
of
the supply, storage and recycle
of
the auxiliary materials. There is
often a need
of
the input
of
auxiliary materials, e.g. various assistant agents, water,
air, etc., and the supply, storage and even recycle
of
them are also necessary.
• Function
of
the collection, treatment and regulation
of
the information. In the
manufacturing process, the transforming, stocking and operating
of
mass flow,
energy flow are inevitably bring about a lot
of
information, it is necessary to col-
lect, treat and regulate them effectively.
It
is more suitable to classify the units
of
the manufacturing process by the
above process functions; but it is not suitable to indentify the whole manufactur-
mg process.
It
is usually to classify complete manufacturing processes by the main products
or raw materials, and then the name
of
the manufacturing process characteriges its
function. This classification method
of
the manufacturing process is used for a
factory, such as:
Chapter 2 Process
Manuf
acturing Industry and Process Engineering 39
• The chemical industry, including salt chemical industry, coal chemical indus-
try, petroleum chemical industry, silicate chemical industry, etc.
• The metallurgical industry, including iron and steel making industry, alumi-
num processing indusing, copper extraction works, etc.
2.5.2 Classification according to structures
In the manufacturing process at the level
of
factory, the concept
of
the structure is
mainly referred to the modes
of
the "connection". In fact, to understand the con-
cept
of
the structure entirely, it can't be completely limited to the modes
of
the
connect only. The modes
of
the connection among the units
of
the manufacturing
process mainly have some basic forms as follows:
• Series connection;
• Parallel connection;
• Circumambulatory (bypass) connection;
• Feedback connection.
I. Series connection. The series connection often refers to the connection in
which output stream
of
one unit is the input stream
of
next unit in manufacturing
process. Furthermore, as for each unit, mass flow only passes along the running
direction for once. Certainly, in the manufacturing process
of
series connection,
the number
of
the units can be more then two. The series connection is mainly
used to realize the matter transformation incessantly and provides certain condi-
tions for the process. The mode
of
series connection is usually adopted in follow-
mg cases:
• The expected transformation can't be accomplished in one unit in principle.
• The process must be divided into several steps to keep certain limit values
of
process parameters, such as a certain temperature, a certain pressure, etc.
• Multi units are much superior than the single unit for the process.
From this sense, the series connection is usually used for realization
of
the
multistep process.
It is commonly applied to the main process
of
manufacturing
industry. For example, the steel manufacture is a multi step process on viewpoint
of
whole plant level, so the steel manufacturing process as a whole takes series
connection.
Fig. 2.4 shows the mode
of
the series connection, the electric arc furnace (EAF)
route for the long products
of
one-to-one relationship in steel industry is the most
typical. Unit I is an ultra high power EAF; unit IIa ladle furnace (LF); unit III a
billet caster and unit
IV
a bar (wire-rod) rolling mill.
------l
Unit I HUnit II H Unit III H Unit IV
~
Fig
.2.4
The schematic diagram
of
the series connection
40 Metallurgical Process Engineering
The mode
of
the series connection is presented by some other forms
of
the
manufacturing process too, for example:
• Concurrent series connection form, see Fig. 2.5.
-
Unit I
a
Unit
I1
a
UnitIIIa
-
-
Unit I
b
Unit li b
UnitIII
b
-
Fig. 2.5 The schematic diagram of the concurrent connection
This kind
of
concurrent series connection process is embodied in the steel
plants with thin-slab casting process. The process is composed by two 150t ultra
high power EAFs (EAF x 2), two 150t LFs (LF x 2) and two thin-slab casters
(CC x 2). The flow directions
of
the concurrent units in this series connection
process are the same, to make the downstream hot rolling mill operate continu-
ously at full capacity.
• Counter current series connection form, see Fig. 2.6.
===1
Unit I
I.
"Unit"
1===1
Unit
ITT
1==1
UnitIV
1==
Fig. 2.6 The schematic diagram of the counter current connection
This kind
of
counter current series connection process is embodied, for exam-
ple, in the FINMET, the gas-based process for direct reduction iron (DRI or RBI).
The iron-rich lump ore or pellets go in positive-direction, while the natural gas
goes in converse-direction. The flow directions
of
the units in this kind
of
connec-
tion are opposite to take full advantage
of
reduction potential and thermal energy
of
the natural gas (Fig. 2.7).
Air
Natural gas
W
as
h
~
r
ofcirculatinggases
Fig.2.7
The flow chart of the gas-based process of direct reduction iron
Chapter 2 Process Manufacturing Industry and Process Engineering 41
• Jumping connections are shown in Fig. 2.8 and Fig. 2.9. These are varieties
of
the series connection process.
===l
Unit I
Fig
.2.8
The schematic diagram of the concurrent jumping connection
Fig
.2.9
The schematic diagram of the counter current jumping connection
Fig. 2.8 is the concurrent series jumping connection.
It
is embodied in the
steel plants where the technologies
of
ingot casting and continuous casting
coexisted, namely, the steel plants produce steel ingots and continuously cast
blanks at the same time, and there is a need for the steel ingots to be rolled
into blooms or billets
of
different sections in the blooming plant. All the
rolled together with the cast blooms/billets are the semi-products for the fin-
ished products. Only a very small amount
of
cast blooms/billets may be proc-
essed by the blooming mill into more suitable sections and then into to fin-
ished products
rol1
ing mill.
Fig. 2.9 is the counter current series connection process. This form is rare in the
chief process
of
the steel plants, but it can be seen in some heat exchanger sys-
tems.
2. Paral1el connection. In the manufacturing process, the
paral1
el connection
mode is
usual1y
used together with the series connection. The series connection
mode always takes the dominative at factory-level
of
process manufacturing in-
dustry; the parallel connection mode is often the supporting form adopted at the
level
of
procedures or branch factories to enlarge the principal connection. The
paral1el connection modes can be distinguished into three kinds in general(Fig.
2.10), that is the input side paral1elconnection, the output side
paral1
el connection
and the original paral1el connection.
Analysing the functions
of
the
paral1
el units, the paral1el connection mode can
be divided into two kinds, namely, the paral1el connection among same functional
units and the parallel connection among different functional units.
The purposes
of
using the
paral1
el connection mode among same functional
units are as follows:
1) When the extent/capacity
of
a unit can't satisfy the requirements
of
in-
put/output for whole manufacturing process, to improve the extent
of
the process
42
Metallurgical
Proce
ss
Eng ineeri
ng
system, several units
of
same kind parallelly connected to satisfy the demand
of
manufacturing process. It is usually seen in the steel manufacturing process, such
as two BFs or three BOFs operate in parallel, etc.
Unit I
Unit II
a
Unit Il,
(a)
Unit r,
Unit II
(b)
Unit I
Unit
II
a
Unit ll ,
Unit 1lI
(c)
Fig.2.10
Th
e sche matic
diagram
of
the
parall
el
conn
ect
ion
mode
(a) The input side parallel connection mode;
(b) The output side parallel connection mode;
(c) The input and output stream-side parallel connection mode
2) Sometimes, the manufacturing process has to decrease its productivity by
chance; the parallel connection
of
units is adopted to satisfy this requirement:
In this case, one
of
parallel production lines can be stopped. For instance,
several reheating furnaces are normally used in hot rolling mill to heat the
billets; when the market is poor, one reheating furnace is stopped to reduce
the production.
3)
It
is inevitable that some units in the manufacturing process should be
paused for maintenance, inspection or temporary failure, the parallel connection
can ensure the manufacturing process operate continuously. For example, in the
BOF steel shop, the operation mode
of
converters "3 by 2" or "2 by I" is adopted.
4) To ensure the reliability
of
manufacturing process, one line in the parallel
connected can
playa
spare role, to make the production steady and reliable. There
are always spare unit for BF airblast engine, main crane, power resource machine
in the steel plant.
5) To reduce the harm
of
interminence by serious accident on the manufactur-
ing process, only one unit continues taking over the task
of
the manufacturing
Chapter 2 Process Manufacturing Industry and Process Engineering 43
process partly as two units operate normally, This can be often seen at the inte-
grated iron & steel enterprises with the process
of
BF-BOF-hot rolling. The rela-
tive example would not be given here.
The purposes
of
using the parallel connection mode among different functional
units are as follows:
I) The various products from one manufacturing process must be processed
separately; it usually appears in chemical manufacturing processes. Such kind
of
example is existed in steel plants as well. For example, there are several continu-
ous casters for the production
of
billets, slabs or rounds with sections in a steel-
making plant, and then they are processed by wire/rod rolling mill, strip rolling
mill or seamless tube mill separately.
2) In some systems
of
the manufacturing process, the different raw materials
for next unit should be prepared separately, and the preparation units operate in
parallel connection mode. For example, in the iron-making process, the functions
of
sintering section, palletizing section, coking section and coal pulverizing sec-
tion are different from each other, these units with different functions operate in
parallel connection mode in one BF shop.
3. Circumambulatory connection (bypass connection). This is a connection
close to the concurrent series connection practically, see Fig. 2.11.
Fig.2.11 The schematic diagram of the circumambulatory (bypass) connection
The circumambulatory connection mode is often seen in the manufacturing
process. For example, in the steel-making process, there are many modes
of
transportation connection between CC casters and reheating furnaces some-
times. When the slabs are hot direct charged and rolled, the slabs enter into
hot rolling mill directly bypassing stocking yard and reheating furnace. Nev-
ertheless, when the slabs are cold or even hot charged, the blanks should enter
into reheating furnace at least, or even the stocking yard, and then into hot
rolling mill to roll into products; this is the circumambulatory connection in
various degrees.
4. Feedback connection. Generally speaking, feedback connection is used
for the recycle
of
material or energy in the manufacturing process. The recy-
cle
of
material is good for improving the utilization and yielding rate; while
the recycle
of
energy is to recover the energy, from the residual and waste
heat, backwards to the manufacturing process, to improve the utilization rate
of
energy.
Usually,two or more units are included in a feedback connection, see Fig. 2.12.
44 Meta llurgical Process
Engineering
C
:.
Unit I
.1
Unit II
Fig. 2.12 The simple schematic diagram of the feedback connection
There are many feedback cycle connection forms
of
material and energy in the
manufacturing process
of
the steel industry. For example, the crops and scraps
from rolling plant are returned to the steel-making plant; the scales from rolling
plant are supplied to steel-making plant and sintering plant; the BOF slag can be
used for the sintering; the power generated by using the COG and BFG can be
supplied to whole plant; the recycled waste heat; circulating water, etc. can be
used also; see Fig. 2.13 and Fig. 2.14.
Hot metal pretreatment
Sludge Crops and scraps
Fig
.2.13
The diagram of the feedback connection
of
iron resource among units
in steel manufactu ring process
Fig.2.14
The feedback connection
of
energy/material in steel man ufacturing process
2.5.3 Classification according to production running modes
As a function of time the matter output of products is the important operation
characteristics
of
manufacturing process. Accordingly, sometimes the manufactur-
ing processes could be classified by the character
of
the output of product flow as
• continuous manufacturing process,
• quasi-continuous manufacturing process, and
• batch manufacturing process.
1. The operation features
of
continuous manufacturing process. In the process
Chapter 2 Process Manufacturing Industry and Process Engineering 45
manufacturing industry, the operation characteristics
of
the continuous manufac-
turing process could be expressed as follows. The output
of
finished products
of
certain characteristics doesn't change with time significantly within a certain
time-interval, this kind
of
manufacturing process belongs to continuous. It should
be pointed out that the numerical value
of
the output
of
finished products in the
continuous manufacturing process may have some changes in different time-
intervals. This variation is always realized by the change
of
surrounding condi-
tions or operation loads, or caused by the change
of
operation loads due to the
change
of
external conditions.
The continuous manufacturing process couldn't be implemented wholly and
thoroughly in steel plants, though it can be realized in some enterprises
of
chemi-
cal industry. However, the continuous operation has been realized in certain de-
gree in some unit systems
of
the steel manufacturing process. For instance, the BF
ironmaking process is actually a subsystem
of
continuous operation.
2. The operation features
of
quasi-continuous manufacturing process. In the
process manufacturing industry, the quasi-continuous manufacturing process
could be characterised as follows. The output
of
finished products gets fluctua-
tions and some undulations with time in a certain time-interval, neverthelss, the
average value can be used to represent the output
of
the process. This kind
of
manufacturing process belongs to the quasi-continuous. If many units are con-
nected and matched together or some operated in the cyclic mode, then the
change
of
operation state
of
these units will make output
of
manufacturing proc-
ess fluctuate with time even pause. This kind
of
manufacturing process can be
also viewed as quasi-continuous process.
The BF-BOF-hot rolling process in steel plants basically belongs to quasi-
continuous process, but some units in which belong to batch process.
The classification
of
manufacturing processes according to the running modes
of
products mentioned above is just in terms
of
the time-characteristic factor
of
the manufacturing process. But the continuity
of
manufacturing process are af-
fected not only by the time-characteristic factor.
It
will be further discussed in the
following chapters.
3. The operation feature
of
batch manufacturing process. The operation feature
of
the batch manufacturing process is that the products are output in batches, pe-
riodically. Such operation is shown by some units in the manufacturing process
of
steel industry. Whatever steelmaking furnace possesses typical feature
of
batch
operation, even the output form
of
the hot continuous rolling mill is
of
batch type
when it is viewed with longer time scale.
2.5.4 Classification according to technologicalfeatures
The classification modes
of
manufacturing processes could be detailed further
46 Metallurgical Process Engineering
when they are classified by the technological features
of
the manufacturing proc-
ess. Interms
of
the technologies, they are always classified by extent
of
the opera-
tion temperature and pressure
of
the process. Therefore, the manufacturing proc-
esses can be classified as follows:
• High temperature and ultra-high temperature process;
• Intermediate temperature process;
• Room temperature process;
• Low temperature and ultra-low temperature process;
• Ultra-high pressure process;
• High pressure process;
• Intermediate pressure process;
• Atmospheric pressure process;
• Low pressure and vacuum process.
When the manufacturing processes are classified by extent
of
the operation
temperature and pressure, these two factors can be combined for the classification
sometimes, such as the high temperature-atmospheric pressure process, the high
temperature-vacuum process, the high pressure-high temperature process, the
room temperature-atmospheric pressure process, etc. The advantage
of
this kind
of
classifying is that the feature
of
equipment and the state
of
the technological
operation could be understood obviously; especially the protection requirements
of
the materials which are bound to be used and the manufacturing process could
be warned. Such classification mode
of
manufacturing processes is often paid
attention by the circles
of
engineering technicians.
References
Gruhn G (1983) System Verfahren Stechnikl (the upper volume). Translated by Lu Zhen-
wei. Chemical Industry Press. Beijing: 39-51
Geiger G H, Poirier 0 R (1973) Transport phenomena in metallurgy. Addison-Wesley Pub.
Co. London
Holland J H (1995) Hidden order: Adaptation builds complexity. Addision-Wesley, New
York
Lerou J L, Ng K M (1996) Chemical reaction engineering: A multi-scale approach to a
multi-objective task. Chem.Eng.Sci. 51(10): 1595-1614
Levenspiel 0 (1972) Chemical reaction engineering. 2nd ed. John Wiley & Sons,
New
York
Szekely J (1971) Rate phenomena in process metallurgy. Wiley Interscience,
New
York
Yin R Y (2002) Energy-saving, clean production, green manufacturing and sustainable
development
of
steel industry. Iron and Steel 37(8): 1-8 (in Chinese)
Zhu G F (2003) Chinese manufacturing in the globalization era. Social Science Academe
Press, Beijing: 235 (in Chinese)
Chapter 3
Engineering
Science
in Steel
Manufacturing
Process
The knowledge systems
of
metallurgy/engineering disciplines comprise three levels, i.e.
fundamental science, or the solution
of
problems on the molecular or atomic scale;
technological science, or the solution
of
problems on the scale
of
procedures, and de-
vices; and engineering science, or the solution
of
manufacturing process problems on
the system level as well as problems
of
coordinating and optimizing the relationships
between each procedure and device. The development
of
the metallurgy began with re-
search on the atomic/molecular scale, and gradually expanded to research on the scale
of
technological science and up to research on the scale
of
overall integrated processes.
Metallurgical process engineering focuses mainly on engineering research on the mac-
roscopic scale.
From the viewpoint
of
technical processing, the steel manufacturing process is a
manufacturing system that consists
of
many procedures
of
different characteristics and
functions. From the viewpoint
of
its physical essence, the process is a multi-factor "flow"
that operates in a dynamic and orderly manner in accordance with given "program
s"
and
within a complex network structure. This is an open, irreversible process, or in other words,
a process
of
matter and energy converting and dissipating
The human being has been using ironware and firing iron ores with charcoal to
iron products for thousands
of
years. There is a long history from reducing iron
ores to puddling wrought-iron, to melting pig iron, further to steelmaking by hot
metal. Hammering the cast ingots into forged steel and afterward improving its
performance by a simple heat treatment also passed through a long period. As a
whole, ferrous metallurgy belonged to ironsmiths' workmanship b
ef
ore the mid-
nineteenth century. The yield, the quality, the production efficiency and the prod-
uct cost depended on natural conditions, especially on smith masters' workman-
ship and their organizing ability. Since the mid-nineteenth century, the manufac-
ture of liquid steel in bulk quantities has been turned up from the workmanship.
R. Yin, Metallurgical Process Engineering
© Metallurgical Industry Press, Beijing and Springer-Verlag Berlin Heidelberg 2011