Yin R. Metallurgical Process Engineering
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28 Metallurgical Process Engineering
Process industries often discharge useful matter, energy, and at the same time
pollutants even toxic substances in the discharging process. In order to solve pol-
lution problems fundamentally caused by the production, such kind
of
industry
needs to develop new green manufacture process (Yin, 2002).
Compared with the production mode
of
process industry, equipment manufac-
turing industry is often characterized by single part production,
of
discrete and
assembly processing mode. Equipment manufacturing industry includes plenty
of
machinery and electric appliance industries, such as automotive industry, aircraft
industry, shipbuilding industry, household appliance manufacturing industry for
TV sets, refrigerators, air-conditioners, washing machines etc. Most
of
products
of
these industries can be directly used by consumers. Their common characteris-
tics are as follows :
• Most
of
raw materials used are products
of
process industry.
• Most
of
products are directly used by consumers for better living conditions.
• Their production process is usually discontinuous or allowed to be discon-
tinuous, even intermittent and pause; the products are usually produced by proc-
essing or assembling details. Their production is often carried through by "dis-
crete mode" .
• The raw materials are processed mainly by physical or mechanical treatments
in such processes and physical changes are observed on them.
• Compared with the process industries, their discharging process is relative
simple, the amount
of
discharged wastes is smaller, the pollution is smaller, and
the pollutants are easier to control and treat.
2.3
Manufacturing
Process
and
Process Engineering
Manufacturing process, also known as "production process" or "process" for short,
often refers to the whole integrated system
of
manufacturing processes especially,
which is made up
of
different procedures and different devices under the condi-
tions
of
industrial production.
The integrated engineering knowledge system, which is made up
of
fundamen-
tal sciences, applied sciences and engineering sciences and related technologies
involved in the abovementioned connotations
of
manufacturing process, is proc-
ess engineenng,
2.3.1 Process and manufacturingprocess
The so-called process can be regarded as the changes
of
things from the initial
state to the final state under given outside conditions. Such changes include
changes at different levels, on different scales and in various structures. The dif-
ference between process and manufacturing process is as follows: process refers
Chapter
2
Process
Manufacturing
Industry
and
Process
Engineering
29
to the general tenn
of
the changes from the initial state to the final state under
given outside conditions, but viewed at an angle
of
space-time, manufacturing
process usually refers to an integrated system
of
large scale or relative large scale
(Lerou,
1996) (Table 2.1). While viewed from operational mechanism, manufac-
turing process often has the function
of
multi-factor integration and the feature
of
multi-level, multi-scale coupling-coordination, which embody in the procedures,
devices and relevant unit operations
of
the manufacturing process. And it also has
the characteristics
of
integrity, complicated structure and complicated phenome-
non as well, it often contains multi-scale phenomena and multi-scale processes,
most
of
which belong to the category
of
complex systems. The most important
feature
of
complex process systems is having the "changing" structure, such
structure is difficult to describe all the phenomena in the process fully by using
the method
of
microscopic analysis; and also can not treated simply with average
parameters as a structureless system. Now, it seems that the more applicable
method is the spatio-temporal multi-scale, which is one
of
the effective methods
to describe the structural features
of
the process at present. Therefore, the manu-
facturing process also possesses performance
of
analysis-integration and integra-
tion-reanalysis-restructuring performance based on the analysis-integration prop-
erty.
Table
2.1
Processes
at
different
level
s andtheir
ranges
of
space-time
scale
(Lerou,
1996)
Process Time scale/s Space scale/m
Molecular/Electronic
<10-
5
< 10-
10
Hydromechanics/Transfer
1O
-
3
~10
1
1O
-
9
~
10
1
Chemical reactions/Catalysis
1O
-
5
~10
3
1O
-
11
~
I0-
2
In metallurgical reactors(device)
1O
-
4
~
10
4
I
0
-
3
~
10
2
At factories(process)
>10
4
> 10
1
With respect to process manufacturing industry, the manufacturing process
often contains the storage, transportation and pretreatment
of
raw materials
and energy, the reaction processes and the processing
of
reaction products,
and it also involves the auxiliary materials and energy supply system con-
nected with reaction process for realizing the functions
of
manufacturing
process. The broadening connotation
of
the manufacturing process can be also
understood generally as the process including the selection, storage and trans-
portation
of
materials and energy, the selection and design
of
products, the
projection and innovation
of
process structure, the control, utilization and
treatment
of
emissions and by-products, the treatment and elimination
of
toxic
and harmful substances, up to the discarding or recovery (recycling)
of
used
products.
30 Metallurgical Process Engineering
2.3.2 Process engineering
The development
of
process engineering should be supported by the knowledge
system
of
fundamental sciences and technological sciences, and intercrossing
of
the knowledge systems
of
related engineering sciences and engineering technolo-
gies.
From the beginning
of
zo"
century, the study in the process industry has been
carried on mainly on microcosmic scale and at basic level, especially the theoreti-
cal study at the atomic and molecular level/scale
of
unit operations, such as
chemical thermodynamics and reaction kinetics subsequently, etc. Such study
often adopts the methodology
of
abstract and closed studying on small scale, aim-
ing to recognize and reveal the possibility, rationality, effectiveness, limitation
of
the reactions and transformations in various unit operations.
From 1950s, the study on the transport phenomena (Levenspiel, 1962; Szek-
ely,
1971; Geiger, Poirier, 1971) i.e. the study on the heat, mass and momen-
tum transfer and the reaction engineering, had intended to promote the optimi-
zation
of
functions and the rationalization
of
designs in the unit procedures and
devices, based on the understanding
of
the principles
of
unit operations and
with a consideration
of
more physical factors. This is a kind
of
technological
and scientific study
of
medium-scale, aiming to obtain the effectiveness, order-
liness, continuity, compactness, etc.
of
the structure and function
of
unit proce-
dures.
However, till now, the knowledge in the field
of
engineering sciences and en-
gineering technologies for the process industry is not be sufficient for quantita-
tive designing, amplification and regulation
of
the manufacturing processes, and
can't
make a theoretical canal for information technologies enter into these
complex technological processes forthrightly and effectively. Therefore, in or-
der to obtain the effectiveness, orderliness, continuity, compactness, etc. in
various manufacturing processes (production technological processes) totally, it
is necessary to carry out the study on complexity-simplification at level
of
manufacturing process with large scale and whole structure. In some aspects,
such study also contains the study on the complex adaption system. With re-
spect to various process industries, this is the knowledge
of
process engineering;
it can also be said as the learning
of
engineering science and engineering tech-
nology at the level
of
manufacturing process . Certainly, for the integrity, com-
plexity and related functions, structures and modes
of
the objects must be con-
cerned when the process engineering is studied.
of
course, the knowledge
of
the
relevant production, such as knowledge
of
equipment, energy economy, envi-
ronmental protection, information and intelligent technologies, etc. should be
considered inevitably.
Chapter 2 Process Manufacturing Industry and Process Engineering 31
2.3.3 Process engineering and manufacturingprocess
The object
of
the study on the process engineering is the topic in the field
of
engi-
neering sciences and engineering technologies
of
manufacturing process in the
process industry, on the basis
of
transformation
of
material and energy. Process
engineering focuses on the description, simulation, projection, optimization, con-
trol and management
of
manufacturing process. It aims at study on the essence
and the regular operation
of
manufacturing process to improve the process effi-
ciency and facilities, to optimize the production flowsheet, to improve the product
quality, to enhance information and intelligent application, and to eliminate pol-
lutants for environmental protection. In short, it will guide the manufacturing to
improve management and economic benefits at all levels.
The manufacturing process
of
process industry usually consists
of
several proc-
essing steps (procedures, devices or named units). The transfer, the transformation,
or the storage and transportation
of
materials and energy are carried out by these
units. Some
of
those are orderly and controllable, but some others are random,
disordered and difficult to control. But the operation characteristics
of
manufac-
turing process often refers to series operation
of
units in the process, and all the
units are operated integratively and synergistically; it is common that the output
of
the former procedure is the input
of
the next procedure, they link up and buffer-
match each other.
In the manufacturing process, microcosmic change/transformation should be
known for each unit (procedure, equipment, etc.); it can also be allowed to use
the concept
of
"black-box" to characterize. The functions
of
the unit in the
manufacturing process are usually to transform the input into the output, as the
specific functions possessed by the unit. Not only the specific functions pos-
sessed by the unit, but also the interrelationship among the units should be
given the attention, as various units are linked each other through a certain rela-
tionship. The concept
of
"relationship" mentioned here can be understood as
logical relation
of
different forms. The relationship between the input set and
the output set are formed by the relationship /connection between two units.
The entirety
of
all the relationships in the manufacturing process is the structure
of
the manufacturing process. The meaning
of
"entirety"
of
all the relationships
is not only the set
of
units' 'relations' but also includes a definite arrangement
between the units.
A series
of
behaviors and events taking place in the manufacturing process are
inevitably accompanied by a lot
of
information. Therefore, process engineering in
the process industry is usually a comprehensive integration system (Fig. 2.2)
of
mass flow, energy flow and information flow, and mass flow itself contains most
part
of
energy flow and information flow.
32 Metallurgical Process Engineering
Manufacturingprocess
0-0-0
-0-0-0
Mass flow Matter flow
Energy flow Energy flow
Informationflow- -
----i
L
J-
-
---
Information flow
0-0
-0
: Process network; 0 :Node: - : Connector
Fig. 2.2 Schematic of concept of process engineering in the manufacturing process
In the process manufacturing industry, specific patterns
of
process engineering
are often expressed by different kinds
of
technological process, in which not only
the input and output
of
materials and energy but also the matter, energy and re-
lated information inside the technological processes occur in the form
of
"flow".
The so-called "flow" may not be used only for fluids (liquids and gases) as fa-
miliar to us. Here, the concept
of
"flow" must not be confined to the flow con-
cerned in hydrodynamics.
It generally refers to the movement (i.e. flow)
of
cer-
tain resources and events among nodes and connectors in a certain network. Here,
again the "network" may correspond to the manufacturing process in the factories
of
process manufacturing industry.
It
can also be embodied by the layout, etc. And
the "node" corresponds to different procedures, devices and reactors in factories
while the "connector" corresponds to transportation route, equipment and lifting
facilities for the materials and energy among various procedures, reactors and
workshops (branch factories) or some pipelines and storage vessels, etc. among
reactors in the production enterprises. However, the "resources" often refer to raw
materials, auxiliary materials, energy supply, equipment, information, etc. And the
"events" generally refer to physical and chemical transformation, conversion,
storage and transportation, process behavior, etc.
The technological properties
of
the manufacturing process are as follows:
• The function
of
the process is to achieve the goal (often a group
of
goals)
of
producing set material or energy conversion.
• Units in the process are the basic processing units for the storage and trans-
portation, transmission or conversion
of
materials and energy.
• The mass flow, energy flow and information flow at input and output points
of
various units in the process are linked up according to certain logical relations.
• The entirety
of
process (manufacturing process system) can be always di-
vided into several sectional processes (subsystems) with specific processing pur-
poses; sectional processes can be further divided into several units, while units
can even be parsed to several unit operations, etc. That means that multi-scale and
multi-level research methods must be used flexibly and skillfully.
• The entirety
of
process has the property
of
comprehensive integration for
various units, sectional processes, and new engineering effects can be occurred,
which is called the "emerge"
of
the nature
of
system in complex sciences, by use
of
the reasonable and skillful comprehensive integration methods/measures; and
this kind
of
engineering effect can also be regarded as formation
of
a certain
Chapter 2 Process Manufacturing Industry and Process Engineering 33
unique or new property.
Thus, the importance
of
the manufacturing process and process engineer-
ing for process industry is evident. At the same time it can be also recog-
nized that the process technology (principle, method, combination and inte-
gration
of
steps) is the soul, and the equipment(device, reactor or apparatus)
is the body, while the products is the embodiment
of
the process operation
(efficiency, effect, benefit). As the manufacturing process shows up the dif-
ferent technico-economic targets for manufacturing industry faced, the
process engineering studies the muti-objectire optimization system under
constraints. Such objective functions
of
optimization include several aspects
as follows:
• Input: optimization
of
raw materials, auxiliary materials, energy, human re-
sources, investment, etc.;
• Output: optimization
of
products, by-products, emissions, cash recovery, etc.;
• In Side process: optimization
of
technical and economical indexes in terms
of
production efficiency, energy utilization, material yield, labor productivity,
equipment operating rate, utilization
of
current funds, etc.
The importance
of
manufacturing process for enterprises
of
manufacturing in-
dustry lies in integrated optimization and comprehensive influence. The manufac-
turing process defines directly on the grade and, quality
of
products, production
efficiency, product cost, delivery rate
of
products, availability
of
resources and
energy, environmental load, linkage
of
eco-industral chains, capital benefits, labor
productivity and other important aspects. Therefore, the manufacturing process is
key solution for enterprises
of
process manufacturing industry to acquire market
comprehensive competitiveness and sustainable development, and it has signifi-
cant correlation with comprehensive influence power on various problems oc-
curred in the process
of
existence and development
of
enterprises
of
process
manufacturing industry (Fig. 2.3).
2.3.4 Connotation and targets
of
process engineering
The study
of
process engineering certainly involves chemical and physical
changes
of
matter (raw materials, auxiliary materials, etc.) under the effect and
support
of
energy and information. The contents
of
this study concern the motion
of
mass flow, and chemical and physical transformation, including microscopic
and macroscopic mass flow, as well as energy transfer and conversion, the inter-
actions among materials and energy, etc. All
of
those are
of
different levels and
different scales. In fact, it mainly intends to study the structure
of
the manufactur-
ing process (production technological processes), the analysis and integration
of
its functions and structure or the restructuring optimization based on the inte-
grated optimization. Process manufacturing industry should produce the
34 Metallurgical Process Engineering
Fig.2.3
Relational grade and comprehensive influence power
of
manufacturing process for
process manufacturing industry
qualified, low-price and environmental friendly products, with the advanced tech-
nology, advanced equipment, the interface technigues among them, and also the
rational way
of
transportation and storage. On this basis, the main purpose
of
the
study on process engineering is to establish a green production process
of
high
efficiency, and energy-saving.
It
studies not only the product manufacture func-
tion
of
process, but also the comprehensive functions to widen the manufacture
and the problems regarding the mode, scale, structure, etc.
of
the manufacturing
process and enterprises.
Process engineering mostly deals with heterogeneous systems, however, the
majority
of
which are systems
of
nonlinear complex functions. To reveal the es-
sence
of
these systems and to explore its operation rules are always the goal
of
engineers and scholars as means to realize the innovation, quantization, optimiza-
tion and regulation
of
these engineering systems.
A comprehensive academic discipline was formed step by step with evolution
and enrichment
of
this kind
of
knowledge. The beginning point
of
the study and
exploration on process engineering is to recognize the optimization-integration
problems on the mass flow, energy flow and information flow in the whole tech-
nological process on the level
of
the entirety
of
manufacturing process. The es-
sence and operation rules
of
manufacturing process are helpful to guide produc-
tion operation, engineering design and technical revamping
of
different process
industries, process structure adjustment
of
an enterprise, improvement
of
product
mix, rationalization
of
the production scale, coordination with environment pro-
tection, and the development trend
of
the enterprise/industry in the future, etc.
Chapter 2 Process Manufacturing Industry and Process Engineering 35
As a developing kind of science, the achievements
of
system science, complexi-
ty research, information technology, environment engineering, etc. should be ab-
sorbed and applied into various disciplines on technology, such as chemical engi-
neering, metallurgy, food, and textile industry, etc.. The integration and dissolu-
tion
of
such disciplines must develop different new process sub-disciplines which
are suitable for industries and their manufacturing processes.
The contents
of
the study on process engineering are as follows:
• The function
of
various components (units, procedures, devices, etc.) in pro-
cess system and the relationship among components;
• The direction, path and efficiency
of
the mass flow, energy flow and the cor-
responding information flow in process system;
• The analysis-integration
of
process system and the level structure
of
it;
• The macro-operation dynamics
of
synergetic running in the process;
• The normalization and optimization models
of
the manufacturing process;
• The effect
of
boundary conditions on process running and structure adjust-
ment;
• The process optimization, and the information engineering or intelligence
technology;
• The manufacturing process and the eco-environmental engineering, etc.
2.4 Features of Manufacturing Process
The complexity and entirety should be emphasized specially to describe the gen-
eral characteristics
of
the manufacturing process. They are formed by the variety
of
different unit functions, complicated species and abundant
of
quantity
of
the
units in process, and the diversification
of
the relationships among the interfaces,
etc.
2.4.1 Complexity
of
manufacturingprocess
What is complex? Complex means a problem consisting of various connected
disorder parts. Variousness is often the representation
of
the quantity
of
things,
while disorder represents jumbling and confusion in the species, shapes, level
structures, scales, etc. Therefore, the term "complex" characterizes a great variety
of
puzzled numbers, structures and shapes
of
the components or things.
What is the complexity? The complexity is referred to the representation
of
the
essence
of
events and their operation rules-operation characters. Further more, the
complexity does mainly refer to process systems.
In a complex system, the overall
performance is not equal to the sum
of
partial performances, because the relation-
ship between the overall performance and the partial performances in the "com-
plex system is not a common linear one, and not a relationship
of
simple addition.
36 Metallurgical Process Engineering
In the complexity science, the term "complexity" contains the characteristics
(Holland, 2000) about variety-diversity on one side, and multi-structure levels on
other side.
It
is not difficult to understand that the nature and operation modes
of
various
manufacturing processes in the process manufacturing industry may be character-
ised by complexity system. There are certain common marks in these manufactur-
ing processes, which are existing and touchable "hidden orders" displayed behind
their complex and diversified even changeful operations.
But it is impossible or not certain to make a complete and accurate explanation
for the performance
of
whole complex system through the understanding
of
the
performances
of
the components-subsystems as procedures or devices. This is the
characteristic
of
the complex system (manufacturing process).
The cognition
of
complexity and complex systems makes people pay attention
to and rethink on the methodology. When problem
of
complex systems like manu-
facturing processes is being studied and solved, there are still some shortcomings
in the methodology
of
reductionism, which has been applied in the scientific and
technological circles for centuries.
It
should be pointed out that the new method-
ology, i.e. holism, must be used simultaneously, although reductionism is still an
important basis.
2.4.2 Integrity
of
manufacturingprocess
In the physical world, wholeness can be divided into several parts, and several
parts can be also integrated to whole in different ways. Whole and part exist as a
couple
of
philosophical category, which represents divisibility and unity
of
objec-
tive matters. The wholeness is the organic-order integration
of
parts, and the parts
are indispensable links
of
the wholeness.
For understanding the manufacturing process, it is obviously that the integrity
of
the manufacturing process must be attached high importance based on the
above cognition
of
the whole and part(units). Especially such a fact should be
seen further from the characteristics
of
static structure and dynamic operation
mode
of
the process systems. As according to the design and structure, the units
(procedures, devices)are always the machines and facilities with the function
of
"body", however, their function running is often influenced by surroundings, by
functions and operation
of
upstream or downstream procedures/devices, There-
fore, the practical operation state or mode changes frequently. So, neither the
units (procedures, devices) are simply regarded as the static machines and facili-
ties, nor the function
of
them is regarded as one or some constant parameters. The
design and construction
of
the manufacturing process should not be separating
and superimposing various units simply and automatically, but unifying and inte-
grating various units orderly to achieve some optimized objective functions ac-
Chapter 2 Process Manufacturing Industry and Process Engineering 37
cording to certain technological ideas (principles, methods, technological routes,
etc.).
It
is not difficult to realize that the functions and efficiency
of
the whole
process are greater than the sum
of
its components when the process system is in
order; but it isjust on the contrary while the process system is in disorder.
With the cognition
of
the relationship
of
"whole and part" in the manufacturing
process, several cognitive problems
of
manufacturing process can be discussed.
There are several aspects should be emphasized as follows when the manufac-
turing process is studied:
• The manufacturing process is an organic, ordered and coordinated wholeness;
it takes large scale and multi-level structure. And the relations among its units
(procedures, devices) are not simple superimposed, unconsolidated, but connected
to each other with matching and coordination. This is the important cutting point
in the study on process engineering. The optimization
of
the manufacturing pro-
cess under certain boundary conditions is based on the analysis-optimization
of
set
of
unit's functions, the coordination-optimization
of
set
of
relationships among
units, and the restructuring-optimization
of
set
of
units. This is the important tar-
get and content
of
the study.
• When the manufacturing process system and its units are operating orderly-
coordinately, the functions and efficiency
of
the whole process should be better
than the sum
of
that
of
its units, even a fully new function and performance
of
process emerged while these units integrated and matched under certain condi-
tions. High attention on this aspect must be paid to optimize the process structure
when the process engineering is studied. Contrarily, when the units are simple
superimposed and stacked, the manufacturing process system operates disorderly,
the function and efficiency
of
the whole process will be worse than the sum
of
that
of
its components, even the failure or partial failure
of
the manufacturing
process system will happen. The task
of
the process engineering is to prevent and
to correct the disadvantageous structure and inefficiency caused by the simple
stacking or superimposing, but to apply engineering technology and engineering
science reasonably in design, manufacture and operation.
• In the manufacturing process, it could not fully cognize and deeply under-
stand its units (procedures, devices) without understanding
of
the integrity struc-
ture and the integrity-coordination operation law
of
the process. The study on the
manufacturing process should not be limited to know the laws
of
manufacture
from the units, but to study the essence
of
structure
of
manufacturing process and
its operation dynamics and the analysis-integration
of
the manufacturing process
at higher level and on larger scale. Just as there is an essential difference between
the study on the human beings as living organism and the study on the human
beings as a simple combination
of
various matter and molecules.
It
is not difficult to understand that using the concepts
of
structure and dynamic
operation rule
to investigate and evaluate the manufacturing process is
of
great