39

Analele Universităţii de Vest din Timişoara

Vol. L, 2007

Seria Fizică

THE APPLICATION OF PROCESS INTEGRATION FOR THE RATIONAL

MANAGEMENT OF ENERGY AND EFFLUENT IN INDUSTRIAL COMPLEXES

PREDRAG RAŠKOVIĆ

Faculty of Technology Engineering, Leskovac, Serbia

Abstract Process integration is a system oriented approach to process design of new or retrofitting of existing industrial plants, which applications are focused on resource conservation, pollution prevention and waste management. Some of research institutions reported that “PI is probably the best approach that can be used

to obtain significant energy and water savings as well as pollution reductions for different kind of

industries”. The potential of PI exceeded the results obtained by than traditional audits, based on separate optimization of individual process units. Two key branches of process integration can be recognized as: Energy integration, that deals with the global allocation, generation, and exchange of energy throughout the process and Mass integration that provides a fundamental understanding of the global flow of mass within the process and optimizing the allocation, separation, and generation of streams and species. Specifically, in the past three decades process integration tools are developed for heat integration systems or Heat Exchanger Networks (HENS), mass exchange network (MENS) and reactive mass exchange network (REAMENS), heat-induced separation network (HISENS), energy-induced separation network (EISENS), waste interception and allocation networks (WINS) ,heat-induced waste minimization networks (HIWAMINS) and energy-induced waste minimization networks (EIWAMINS), and membrane separation networks. This paper provides an overview of some of these developments, outlines the major methodology, ideas and objectives, and mark the process integration as an active research area which leads to significant contributions on the engineering principles of integrated systems Keywords: Process integration , process design, CLEANER production.

1. Introduction

In response to the staggering environmental and energy problems associated with

manufacturing facilities, the process industry has recently dedicated much attention and

resources to mitigating the detrimental impact on the environment, conserving resources, and

reducing the intensity of energy usage. In the past decades scientific community has seen

significant industrial and academic efforts devoted to the development of holistic process

design methodologies that target energy conservation and waste reduction from a systems

perspective.

Process Integration (PI) is a new term that emerged in the 80's and has been extensively

used till today to describe certain systems oriented activities related primarily to process

design (Fig. 1.) [1],[2].

40

Fig. 1. The review of academic and commercial PI developers

The working definition of Process Integration within the International Energy Agency

(IEA) was established in Berlin (October 1993):

“Systematic and General Methods for Designing Integrated Production Systems,

ranging from Individual Processes to Total Sites, with special emphasis on the Efficient Use of

Energy and reducing Environmental Effects”.1

Process integration belongs to the scientific field of Chemical engineering which is a

branch of science that handles the processes involved in the conversion of raw materials and

chemicals into more useful products. Beside the use of information from other fundamental

sciences, chemical engineering is the major contributing factor in the development of

industries and not Chemistry. The key difference between these two closely related fields is in

the research approach and goals. The chemist research goal, based on laboratory experiments,

is the simplest way to complete a reaction for creating the required product. However, the

1 Later, this definition has been somewhat broadened: "Process Integration is the common term used for the

application of methodologies developed for System-oriented and Integrated approaches to industrial process plant design for

both new and retrofit applications. Such methodologies can be mathematical, thermodynamic and economic models, methods

and techniques. Examples of these methods include: Artificial Intelligence (AI), Hierarchical Analysis, Pinch Analysis and

Mathematical Programming. Process Integration refers to Optimal Design; examples of aspects are: capital investment,

energy efficiency, emissions, operability, flexibility, controllability, safety and yields. Process Integration also refers to some

aspects of operation and maintenance". More recently, Sustainable Development is included in the definition of Process

Integration.

41

simplest mechanism of chemical reaction is not always the optimal one, from economic,

manufacture and environment point of view. The chemical engineer investigates and evaluates

all these mechanisms in order to create the large-scale processes that can accomplish these

tasks and provide the quantity and quality of required products. Inside the wide field of

chemical engineering, process integration can be inlay in process engineering, a part of

chemical engineering which focuses on the design and maintenance of manufacturing

processes and plants (especially chemical processes and plants).

The scientific approach used in process integration can be classified in the group of

Systems Engineering (SE) methods. Systems engineering is a holistic and interdisciplinary

field of engineering that focuses on the development and organization of complex artificial

systems. By this approach one can understand the fundamental features of manufacturing

process and according to this develop better design, management and implementation,

meeting the needs of business and society as a whole. More specific definition of process

integration lead to the field of Process systems Engineering (PSE) (as the name imply system

approach in process engineering) which deals with the overall system behavior and how the

individual units should be combined to achieve optimal overall performance.

Fig. 2. Scientific field of Process Integration

According to the definition of IEA, Process Integration can be described as PSE

systems approaches in space (the whole plant, the entire site, and sometimes even the whole

community), in contrast with Life Cycle Analysis (a systems oriented methodology in time)

and Integrated Process Design (a systems view across scientific disciplines and software

systems)[1].

42

2. Short overview of research tasks, areas and benefits of Process Integration

Process integration is a holistic approach to process design, retrofitting, and operation of

industrial plants, which applications are focused on resource conservation, pollution

prevention and energy management [3]. Generally, the term process integration has meant

integrated and system-oriented planning, operation, optimization and management of

industrial processes. A production plant has been seen as a complex system of several

processes which comprising several unit operations as it is shown Fig. 2. The processes

consist of a large number of material and energy flows is needed between the unit operations

and the processes.

Fig. 3. Areas of Process Integration

Generally speaking PI is concerned to the advanced management of material, energy

and information flows in a production plant and the surrounding community (Fig. 3.) based on

the multi criteria optimisation of the processing systems (Fig. 4.).

Today Process integration can be broadly categorized into Energy integration and Mass

integration. Energy integration deals with the global allocation, generation, and exchange of

energy throughout the process. Mass integration creates the picture of the global flow of mass

within the process and optimizing the allocation, separation, and generation of streams and

species. It has been developed and applied to the environmental and mass processing

problems of the processes.

43

Fig. 4. Objectives of Process Integration

The implementation of PI methods can lead to significant energy savings and waste

reduction (primary wastewater minimization). Some of research centres [4] reported that “PI

is probably the best approach that can be used to obtain significant energy and water savings

as well as pollution reductions for different kind of industries”. Their experience, summarized

for the wide variety of industrial processes (Fig. 5), point out the great potential for improving

the efficiency of large and complex industrial facilities. This potential exceeded the results

obtained by than traditional audits, based on separate optimization of individual process units.

Fig. 5. Energy and water savings potential for different industries.

44

3. CLEANER production and process integration tool

Cleaner Production (CP) presents the preventive environmental approach, aimed to

increase overall efficiency of processes in industry, and to reduce generation of pollution and

waste at source. The concept of CP underlying the comprehensive strategy for solving the

problem at several levels at once based, on “anticipate and prevent” philosophy. Cleaner

Production broadly encompasses the terms like waste minimization, pollution prevention,

cleaner technology, waste reduction, eco-efficiency and source reduction. Recently, the term

‘Cleaner Production’ has been replaced by ‘Sustainable Consumption and Production’ (SCP)

by organizations such as UNEP, UNIDO and UN-Division of Economics and Society. [5]

Since the CP includes measures to conserve raw materials, water and energy and

measures to reduce the pollution Rossiter [6] points out that the philosophies of Cleaner

Production and Process Integration are complementary to each other. Dunn and Bush (2000)

[7] create the CLEANER (acronym of Combining Lower Emissions and Networked Energy

Recovery) production design strategy as the framework for identification of cost-effect waste

reduction and energy conservation process designs. This strategy uses a group of systems

analysis tools and process integration methods to systematically accomplish the design task.

The systems analysis tools are used to examine the design directions for designing the

efficient systems without the need of new unit operations. System analysis tools enable the

identification of good, cost-effective solutions that result in waste reduction and/or energy

conservation via recycle and reuse options. Furthermore, PI design methodologies can be

divided into energy conservation design methodologies and waste reduction design

methodologies. Another classification (present on Fig. 6.), can be addressed as end-of-pipe

methods or in-plant process designs methods.

The first, end-of-the-pipe methods drive more attention to separation and recycling

waste minimization systems. This approach is used to identify cost-effective waste separation

system among many process options. The MEN design task involves identifying cost-effective

network of mass exchangers that optimally transfer undesirable species (pollutant) from a

group of rich (waste) streams to a group of lean (MSA) streams. A single mass exchanger is

defined as a direct-contact, counter current unit such as absorption columns, adsorbers,

extraction units, strippers and ion exchange units. In the case of reactive mass exchange MEN

methodology is extend to REAMEN methodology. Like the MEN, a REAMEN still involves

the use of direct-contact counter-current units; however, this design methodology includes

contact with MSAs that react with the waste constituents.

45

Fig.6. The CLEANER production design strategy

46

Second end-of pipe design methodology, which involves the use of energy-separating

agents (ESA) is the heat-induced separation networks (HISEN). ESA is employed to separate

species via phase change. The process integration task in HISEN is to identify a cost-effective

system to reduce waste through stream heating/cooling. In the case when

pressurization/depressurization units are included within the HISEN task the next task named

as energy-induced separation network (EISEN) is generated (especially in the case of

emission of gases that comprise volatile organic compounds -VOCs) .Membrane separation

networks -MSN is pressure-based systematic design techniques. MSN presents a network of

process units that removes pollutant(s) from streams via the use of membranes and stream

pressurization and/or depressurization. Example technologies targeted by this design approach

are reverse osmosis and pervaporation.

Although end-of-pipe recycle/reuse systems provide an attractive approach for waste

minimization, there may be a greater economic incentive to address pollution prevention from

an in-plant design perspective. One of the reasons is that in-plant modifications are generally

less capital intensive and easier to retrofit within an existing process. The second reason is

that reaction/material substitution usually involves several years of research and development,

and in some cases, could also depend on an invention. Thus, source reduction via in-plant

modifications is an attractive approach towards tackling waste minimization for existing

process plants. The following four strategies are most commonly pursued to address in-plant

reduction of pollutants.

Heat exchanger network synthesis (HENS) presents the most important approach, and

the one that originally gave birth to the field of Process Integration. Principal aspect of HENS

can be found in the fact that most industrial processes involve transfer of heat, either from one

process stream to another process stream (interchanging) or from a utility stream to a process

stream. Consequently, target in any industrial process design is to maximize the process-to-

process heat recovery and to minimize the utility requirements. To meet this goal, industrial

cost-effective HEN (consisting of one or more heat exchangers that collectively satisfy the

energy conservation task), is of particular importance. The single most important HENS

concept is the Pinch Technology discovered independently by Hohmann (71), Umeda et al.

(78-79) and Linnhoff et al. (78-79)[8],[9]. Pinch Technology is originally developed as a tool

for the design of energy-efficient heat-exchange networks during petroleum crises in late

1970s and early 1980s, in response to the sharp increase in the price of energy .From that

time, pinch technology based techniques have found application in a wide range of system

design, including: distillation column profiling, low-temperature process design, batch

47

process integration, emissions targeting and water and wastewater minimization. The concept

has later been expanded into new areas, like Mass Pinch, Water Pinch, Hydrogen pinch, by

using various analogies. The most obvious analogy is between heat transfer and mass transfer,

first recognized by El-Halwagi and Manousiouthakis (1989)[10]. The similarities of these

mechanisms suggested that a design method for heat-exchange networks might be possible to

use for the design of mass-exchange networks.

The WIN synthesis methodology is based on the use of direct-contact mass separating

agents (MSAs) to achieve a specified waste reduction task. By rerouting of in-plant process

streams the designer can identify the optimal location(s) of mass exchangers in cost effective

manner.

The HIWAMIN design technique features the use of indirect-contact, energy separating

agents to intercept the undesirable species and to identify the optimal location( s) of heat

induced separators and heat exchangers. Furthermore, the HIWAMIN design approach

simultaneously addresses the waste minimization and process heat integration (HEN) design

tasks. The EIWAMIN design technique extends the HIWAMIN approach to include the use of

pressurization and/or depressurization devices in addition to heat-induced separators and heat

exchangers to further improve separation efficiencies and the cost effectiveness of the final

design.

Wastewater Minimization Systems presents a design strategy for reuse, regeneration

reuse, and regeneration recycling of wastewater streams that minimizes water usage and

minimizes wastewater discharge. Example technologies targeted by this design approach:

direct recycle opportunities, regeneration, reuse, and recycling opportunities

4. Conclusions

As a result of the environmental and energy challenges facing the process industries,

researchers over the past two decades have focused their attention on reducing environmental

impact, energy usage and conserving material. To achieve these objectives, the focus has

moved from unit-based to wide system-based approach which enables the designer to see “the

big picture first, and the details later”. On that way, it is not only possible to identify the

optimal process development strategy for a given task, but also to uniquely identify the most

cost-effective way to accomplish that task.

In this paper the most important system-based approach -Process integration is

presented. Process integration is described as “a holistic approach to process design,

retrofitting, and operation which emphasizes the unity of the process”, differently to a design

48

approach that optimizes at the unit operation level. After more than a thirty years of practical

use, Process Integration is addressed as one of the best approach that can be used to obtain

significant energy and water savings as well as pollution reductions for different kind of

industries. Recently PI is involved in wider framework of CLEANER production design

strategy, covering the wide range of industrial processes.

One of the main conclusions from this paper is the need for education, training and

dissemination. Looking at the map in Fig. 1, one can conclude that the knowledge of PI tools

is poorly implant in academic and commercial institution in less developed countries, which

suffered from chronically inefficient energy conservation and waste reduction technology. The

review like this has the task to show where the PI methods can be, and have been, used to

provide practical and efficient solutions. This should encourage uptake of the PI methods in

industries where reduced energy costs and pollution standards are still not a primary objective

of the manufacture.

References

1. Gundersen T., Process Integration PRIMER, SINTEF Energy Research, (2000).

2. Gundersen T., A worldwide Catalogue on Process Integration, SINTEF, (2001).

3. Rašković P. Industrial energy system optimization based on heat exchanger network

synthesis, Faculty of Mechanical Eng., Univ. of Nis, Serbia and Montenegro, (2002).

4. Process integration, CANMET Energy Technology Centre (CETC) – Varennes, Canada.

See also http://cetc-varennes.nrcan.gc.ca/en/eb_o.html.

5. See http://www.unepie.org/pc/cp/understanding_cp/home.htm

6. Rossiter, A P, H D Spriggs and H Klee, Apply Process Integration to Waste

Minimisation, Chem Eng Prog, 89 (1), 30 (1993)

7. Dunn, R.F. and Bush, G.E., Using Process Integration Technology for CLEANER

Production, Journal of Cleaner Production, 9,1, 1-23, (2001).

8. Shenoy, U. V. Heat Exchanger Network Synthesis: Process Optimization by Energy and

Resource Analysis. Houston Gulf: Publishing Co., (1995).

9. El-Halwagi, M. M., Pollution Prevention through Process Integration: Systematic

Design Tools, San Diego: Academic Press, (1997).

10. El-Halwagi, M. M. and Manousiouthakis, V., Synthesis of Mass Exchange Networks,

AIChE Journal. 35 (8). 1233-1244, (1989).