- Email: [email protected]
Recent advances in industrial process optimisation
Journal of Cleaner Production 13 (2005) 1369e1373 www.elsevier.com/locate/jclepro
Editorial
Recent advances in industrial process optimisation 1. Introduction Both well developed countries and the majority of the world’s population living in the developing countries, some of them developing enormously fast and requiring escalating amounts of natural resources and consuming larger and larger share of energy, are becoming increasingly concerned with the impact of their industrial production on the environment and therefore upon the quality of life for all humans. Growing numbers of our society are increasingly aware of the dynamic interconnections and interdependencies of humans with all of the other species. Unless our industrial, economic, political and social systems work increasingly in harmony with the basic ecological systems and the systems that govern them, we will all disappear from this blue planet. This is one of the reasons why both the academic and scientific communities are urged to deliver cleaner, more eco-efficient solutions which are ecologically and economically sound, at the same time, and therefore, have the potential to contribute to sustainability of our societies. As a response to this need, various scientific and research conferences are being held to encourage the cross-fertilisation among people of many nations about the progress, problems and challenges they are experiencing in their quest for developing and implementing cleaner production programmes that contribute to the short and long-term sustainability of their societies. The series of conferences on ‘‘Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction’’ (PRES) is one such opportunity for cross-fertilisation. It was established originally to address issues relevant to process integration in connection with the thermal efficiency of various processes, but it has now been expanded to focus increasingly upon cleaner production, sustainable consumption and sustainability issues. The organisers of the PRES conferences are proud to attract delegates from numerous countries world-wide providing a friendly platform for fast and efficient spreading of novel ideas, processes, procedures and policies. 0959-6526/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.jclepro.2005.05.019
This special issue of Journal of Cleaner Production is the third in a series developed from selected papers of the PRES conferences. The previous issues, based upon papers from PRES conferences were published recently [1,2]. The PRES conference is also collaborating with other well-known journals (see e.g. [3e5]); however, the collaboration with the Journal of Cleaner Production (JCP) is the most intensive as the conference’s main topics are very coherent with those of JCP’s readership. PRES’03 was held, for the first time, outside the European continent. The PRES organisers were very pleased to accept the invitation from the Canadian Society for Chemical Engineering and Chemical Institute of Canada. Consequently, PRES’03 was held jointly with the 53rd Canadian Chemical Engineering Conference e CSChE 2003 in Hamilton, Ontario, Canada. The Canadian organisers led by Andrew Hrymak and Roland Anderson contributed enormously to the success of PRES conference. Delegates from more than 50 countries participated, despite the scary situation just after 9/11. Logically, PRES’03 had a strong North American continental participation; however, Europeans, Asians and Africans were also actively engaged. 2. Overview of the papers included in this issue For this Special Issue of the Journal of Cleaner Production, 11 documents representing various aspects of this field and related inputs are included. The internationality of PRES is reflected by the fact that competitively selected researchers from 13 countries e Belgium, Canada, Germany, Greece, Malaysia, Ireland, Italy, Poland, Romania, South Africa, Spain, Switzerland and the United Kingdom authored the papers for this issue. 3. Three main thematic groups The first part of this Special Issue deals with various aspects of improvement in management of water and
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Editorial / Journal of Cleaner Production 13 (2005) 1369e1373
wastewater. It is very interesting to note the very rapid changes and the diverse approaches and applications that are being tested and implemented to provide enough good quality water for both the growing world population and for the expanding agriculture and industry. It is increasingly clear that this is directly related, at least in part, to minimisation of the consumption of water in industry and to the minimisation of wastewater as well. The second part of this issue deals with some specific issues of cleaner production in: pulp and paper mills, production of synthetic natural gas from wood, cleaner sugar production and the removal of harmful NOx. The final part is devoted to important management, LCA and recycling problems: to long-range planning and design of supply chain and ECO-Design of Reuse and Recycling Networks. 3.1. Water and wastewater The first paper, authored by Thoko Majozi from the Republic of South Africa, was titled, ‘‘An effective technique for wastewater minimisation in batch processes’’ [6]. He presented a continuous-time mathematical formulation for freshwater and wastewater minimisation in multipurpose batch industrial plants. The minimisation of wastewater production is achieved through the implementation of numerous recycle and reuse opportunities. A superstructure that entails all the possible recycle and reuse possibilities is used as the basis for the formulation. Initially, the formulation disregards scheduling which forms the basis for the inherent time dimension in water-using batch facilities. This necessitates a priori specification of starting or finishing times, given the duration for each water-using operation. The formulation is then extended to embed wastewater minimisation within an established scheduling framework. This extension, which is a true representation of a practical environment, allows the time dimension to be captured by specifying duration instead of starting and finishing times. In both forms, the formulation is applicable to batch facilities with or without reusable water storage tanks and can readily be extended to multiple contaminant media, although this will be the subject of another publication. Fixing the outlet concentration and the contaminant mass load for the each water-using operation in the absence of central reusable water storage, initially renders the formulation of a nonconvex mixed integer nonlinear program (MINLP) which is linearised exactly to yield a convex mixed integer linear program (MILP). On the other hand, allowing the outlet concentration to vary within predefined bounds while fixing both the water requirement and the contaminant mass load, yields an MINLP formulation for which global optimality cannot be guaranteed in complex problems. The developed formu-
lation is applied to a published literature example as well as to case studies involving production scheduling. A similar problem for dealing with batch processes from a different angle was studied by a group of Malaysian authors, Dominic Chwan Yee Foo, Zainuddin Abdul Manan and Yin Ling Tan from, Universiti Teknologi Malaysia in Skudai, Johor in their article titled, ‘‘Synthesis of maximum water recovery (MWR) networks for batch processes’’ [7]. Their work is based upon application to batch processes, of the well established Pinch Analysis and Process Integration that was designed for use in continuous processes[8]. Substantially, less work has been done on water minimisation problems for batch process systems. The authors present a two-stage procedure for the synthesis of an MWR network for a batch process system, covering both mass transfer-based and non-mass transfer-based water-using processes. The first stage of the synthesis task is to locate the minimum utility targets (freshwater feed and wastewater generation) using a new numerical technique called the time-dependent water cascade analysis (WCA) technique [9]. This technique, which was originally developed for continuous water network analysis has been extended into batch water network systems. In the second stage, a new tool called the timee water network is introduced to synthesis the MWR network to achieve the established utility targets. This new network representation has an advantage of clearly depicting the time-dependent nature of a batch water network. This paper shows that through appropriate adjustments, both minimum utility targeting and network design techniques from continuous processes can be extended into batch water-using systems. Two different process scenarios were analysed, i.e. network with and without water storage systems. The third paper dealing with water and energy simultaneously is from Ireland. Theodore Zhelev authored, ‘‘Water Conservation through Energy Management’’ [10]. The objective of his paper is the simultaneous management of two important industrial resources e energy and water. It addresses a class of industrial processes where heat transfer is accompanied by mass transfer (water evaporation and condensation) with special attention where the transfer of heat is a limiting stage. These processes are considered in integration with all related processes and subsystems. More specifically, the set of processes and subsystems include cooling systems, systems of contact economizers for flue gas energy recovery, scrubbers, direct steam heaters, driers, related systems of coolers and the heat exchanger network. The proposed preliminary design procedure is based upon concepts and tools related to an advanced Pinch technology specially modified for consideration of simultaneous heat and mass transfer. The manipulated parameters include process latent and sensible heat loads and system’s structural changes with
Editorial / Journal of Cleaner Production 13 (2005) 1369e1373
efficiency criteria allowing sacrifice of quantity for quality of performance. Two specific procedures allow targeting of maximum flue gas energy recovery and minimum temperature of cooling water, providing guidance to structural design and system operation. The application of proposed methodology is designed to achieve water conservation through minimisation of water evaporation losses. Its significance is demonstrated through three industrial applications (a power station, a brewery and a tissue factory). The fourth paper focuses upon an application of recently very popular genetic optimisation algorithm. Vasile Lavric, Petrica Iancu and Valentin Plesu, researchers from Belgium and Romania submitted a document titled, ‘‘Genetic Algorithm Optimization of Water Consumption and Utilization System Topology’’ [11]. The Genetic Algorithm Optimisation (GAO) approach that they employ was used for generation of a best water network topology with a minimum freshwater usage, complying, at the same time, with all constraints. An optimal water network could be seen as an oriented graph, starting from unit operations with no contaminant at entrance, each unit operation ‘‘i’’ receiving streams from possibly (but not inevitably) all previous operations ‘‘j’’ only ( j Z 1, 2.i ÿ 1), and sending streams to probably (but not necessarily) all next operations ‘‘j’’ ( j Z i C 1, i C 2.N ). The mathematical model describing the unit ‘‘i’’ is based upon total and contaminant species mass balances, together with the input and output constraints. The GAO uses each internal flow as a gene, defining a chromosome from all these flows. The constraints are to comply with during the population generation, by simply eliminating those individuals outside the feasible domain. The individuals can interbreed according to their frequency of selection, using the one-point crossover method. The objective function is the reduction of the total freshwater consumption. Comparisons with the results of water pinch and mathematical programming methods are made. In the discussion of the pros and cons of this approach the authors highlight the classes of problems where application of this approach is beneficial. The second group of papers starts with a Canadian contribution from Montre´al and Edmonton. Michal Dabros, Michel Perrier, Fraser Forbes, Martin Fairbank and Paul Stuart submitted a paper titled, ‘‘ModelBased Direct Search Optimisation of the Broke Re-Circulation System in Newsprint Mill’’ [12]. Their work explores the dynamic modelling of the papermaking section of an integrated newsprint mill and the subsequent application of two direct search methods in a proof-of-concept optimisation study of broke recirculation strategies. The effect of the current broke recirculation policy on the mixed pulp properties at the paper machine head boxes was quantified using the dynamic simulation and an objective function which
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reflected the rate of change in measurable (flow, consistency and temperature) and immeasurable (total dissolved solids and fibre length distribution) parameters. Again a Genetic Algorithm as in the previous paper and the Nelder-Mead simplex methods were then linked dynamically to the simulation and used to find improved ways of re-circulating broke pulp. The profile of the changes to the broke ratio was modelled using a quadratic function and a second order transfer function; as a result the coefficients of these functions were optimised. An implementation study of the optimised operating strategy has been recommended to the newsprint mill. It is expected that by reducing variability at the paper machine headbox, the overall machine stability will increase, effectively leading to a lower sheet breakage frequency. Achieving this goal, in the real process, increased the mill’s productivity and noticeably reduced its negative environmental impacts. The following contribution deals with a paper mill as well. Xavier Turon, Jalel Labidi, Jean Paris from Girona, Spain and Montre´al, Canada in their paper ‘‘Model-Based Direct Search Optimisation of the Broke Re-Circulation System in Newsprint Mill’’ [13] used a process simulation of a high-grade coated paper mill to carry out a process integration study. Data necessary to calibrate and validate the simulation developed with Cadsim PlusÒ software were obtained by: measurements, samples analysis and estimations through partial and local mass balances. The simulation was designed to permit grade changes to reproduce variations in mill operations. The simulation was used to support process studies to optimise water and raw material’s consumption and to evaluate results obtained by mathematical optimisation. Different scenarios were studied in order to evaluate the feasibility and the effects of process redesign of the mill operation. A Genetic Algorithm was again used for optimisation. Satisfactory solutions which reduce water consumption and fibre losses were implemented into the process simulation to evaluate their technical feasibility. Alexis Duret, Claude Friedli, Franc¸ois Mare´chal from Swiss Federal Institute of Technology, Lausanne explored diverse ways of wood gasification in their paper ‘‘Process design of Synthetic Natural Gas (SNG) production using wood gasification’’ [14]. The process design of a 10e20 MWth Synthetic Natural Gas (SNG) production process from wood was performed. Combining process modelling and process integration techniques, this study proceeded via the following stages: (i) thermodynamic modelling: mass, energy balances and simulation of the wood gasification, the machination and the purification units; (ii) process integration that identifies the energy saving opportunities and prepares a thermo-economic optimisation. They demonstrated that the process can transform wood into pipeline quality methane with a thermal efficiency of
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57.9% based on the Lower Heating Value (LHV). The process integration study showed that the heat surplus of the process can be used to almost satisfy the mechanical work required by the process; only 7% of the mechanical needs will have to be from an external source. An Italian group from Giuseppe Vaccari, Giulio Sgualdino, Elena Tamburini, Giorgio Pezzi, Piercarlo Citterio, Roberto Verardi and Krzysztof Urbaniec from Poland submitted a paper titled, ‘‘ New eco-friendly proposal for the crystallization of beet raw juice’’ [15]. Their work focuses upon different strategies with the objective of completely eliminating the traditional calcocarbonic purification process by addressing the wellknown problems related to the utilization of lime and the production of carbonation sludge. As a result of their research, they proposed: (i) the direct crystallization of raw juice, (ii) the crystallization of micro filtered raw juice, and (iii) the chromatographic separation of the raw juice. In all cases, they utilized the cooling crystallization technique. To complete the picture of the possible solutions to be adopted for the elimination of the traditional purification process, they comprehensively evaluated laboratory tests and pilot plant results for processing raw juice via the following steps: (i) micro-filtration and softening of the raw juice; (ii) first cooling crystallization with the objective of obtaining commercial white sugar; (iii) chromatographic separation of the run-off of the first crystallization step; (iv) decolourization of the extract (rich-sugar fraction); and (v) cooling crystallization with the objective of obtaining commercial white sugar and recycling of the previously produced sugar. The results obtained, as well as the proposed flow-sheet and a comparison with the previous strategies, are presented and discussed. Natassa Dalaouti and Panos Seferlis from Chemical Process Engineering Research Institute in Thermi e Thessaloniki developed novel ways to remove harmful NOx emissions that are addressed in their paper titled, ‘‘Design sensitivity of reactive absorption units for improved dynamic performance and cleaner production: The NOx removal process’’ [16]. The reactive absorption of nitrogen oxides from gas streams has received extensive attention due to stringent environmental regulations that govern this pollutant. The operating and environmental specifications of the process have to be met within the context of process disturbances. A study of the effect of different column design configurations and control structures on the disturbance rejection properties of the NOx removal system was performed. Their work provided a useful and powerful tool for the efficient control of NOx emissions not only through the fine-tuning and monitoring of the implemented control system but also through the selection of the proper absorber configuration and operating mode for the unit. The proposed method combines the benefits
of an accurate and detailed modelling of the complex reactive absorption process of NOx removal and the results of a systematic controllability analysis to guarantee smooth operation, efficient disturbance rejection and consequently a cleaner production process. The third group of papers begins with an article from Imperial College of Science and Medicine, London, authored by Andre Hugo and Stratos Pistikopulos, titled, ‘‘Environmentally Conscious Long-Range Planning and Design of Supply Chain Networks’’ [17]. The article includes a mathematical programming-based methodology for the explicit inclusion of life cycle assessment (LCA) criteria as part of strategic investment decisions related to the design and planning of supply chain networks. By considering the multiple environmental concerns together with the traditional economic criteria, the planning task is formulated as a multi-objective optimisation problem. Over a long-range planning horizon, the methodology utilizes mixed integer modelling techniques to address strategic decisions involving the selection, allocation and capacity expansion of processing technologies and assignment of transportation links required to satisfy the demands at the markets. At the operational level, optimal production profiles and flows of material between various components within the supply chain are determined. As such, the formulation presented combines the elements of the classical plant location and capacity expansion problems with the principles of LCA to develop a quantitative decisionsupport tool for environmentally conscious strategic investment planning. Fundamental to the overall approach is the formulation of an appropriate environmental performance objective to guide strategic decisionmaking. For this task, a recently developed method of impact assessment, the Eco-Indicator ’99 method, was incorporated within the quantitative LCA model. The last document was submitted by Pinar Erol and Jorg Tho¨ming from University of Bremen in Germany, titled, ‘‘ECO-Design of Reuse and Recycling Networks by Multiobjective Optimisation’’ [18]. An ECO-optimised reuse of process liquors addresses the financial gain and the effective use of resources. In processes that have a potential for process liquor recovery, the optimisation of economic and minimisation of environmental burdens can be realised by an ECO-optimal design of the reuse and recycling network (RRN). In this document, a procedure for synthesizing such an RRN for a metal finishing process is presented. The simultaneous analysis of environmental impacts sensitivity (SAEIS) based on a superstructure approach, combined with multi-objective optimisation is performed by mixed integer nonlinear programming (MINLP). This allows an ‘‘ECOeECO’’ trade-off i.e. total annualised cost and environmental impacts are minimised simultaneously. By varying the weighting factor, different RRN alternatives were generated. In the metal finishing case study, applying
Editorial / Journal of Cleaner Production 13 (2005) 1369e1373
the ECO-Design by multi-objective optimisation was combined with LCA-tool as a hybrid approach: thereby different RRN alternatives were received by varying the weighting factor for the representative impact score and the cost in the objective function. A replacement of either the standard or closed-loop systems by an openloop system will result to be the most environmentally benign alternatives and with a reasonable return from investment.
4. Conclusions We believe that the papers in this Special Issue of Journal of Cleaner Production will be of interest and relevance to a broad range of readers in this field and will bring the PRES Conference series to their attention. The help of all collaborators and the ISC members [19] is gratefully acknowledged, both for actively contributing to the conference and for taking part in the editorial process to develop the papers for official publication within the Journal of Cleaner Production. A special appreciation is expressed to all authors for their contributions. We would like to continue and further develop the mutual collaboration between the Journal of Cleaner Production and the PRES conference the series. The seventh PRES’04 conference was held in Prague, the Czech Republic, again jointly with CHISA 2004 and another Special Issue is being developed. The eighth PRES’05 was held jointly with ICheaP-07 in Taormina, Sicily, Italy and the ninth PRES 2006 will again return to ‘‘golden Prague’’ in August 2006.
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[6] Majozi T. An effective technique for wastewater minimisation in batch processes. Journal of Cleaner Production 2005;13:1374e80. [7] Foo CY, Manan ZA, Tan LY. Synthesis of maximum water recovery network for batch process systems. Journal of Cleaner Production 2005;13:1381e94. [8] Wang YP, Smith R. Wastewater minimization with flow rate constraints. Transactions of the Institute of Chemical Engineers, Part A 1995;73:889e904. [9] Manan ZA, Foo DCY, Tan YL. Targeting the minimum water flow rate using water cascade analysis technique. AIChE Journal 2004;50(12):3169e83. [10] Zhelev TK. Water conservation through energy management. Journal of Cleaner Production 2005;13:1461e70. [11] Lavric V, Iancu P, Plesu V. Genetic algorithm optimisation of water consumption and wastewater network topology. Journal of Cleaner Production 2005;13:1395e405. [12] Dabros M, Perrier M, Forbes F, Fairbank M, Stuart’ P. Modelbased direct search optimisation of the broke re-circulation system in newsprint mill. Journal of Cleaner Production 2005; 13:1406e13. [13] Turon X, Labidi J, Paris J. Simulation and optimisation of a high grade coated paper mill for cleaner production. Journal of Cleaner Production 2005;13:1471e80. [14] Duret A, Friedli C, Mare´chal F. Process design of synthetic natural gas (SNG) production using wood gasification. Journal of Cleaner Production, in press. [15] Vaccari G, Sgualdino G, Tamburini E, Pezzi G, Urbaniec K. New eco-friendly proposal for the crystallization of beet raw juice. Journal of Cleaner Production 2005;13:1414e27. [16] Dalaouti N, Seferlis P. Design sensitivity of reactive absorption units for improved dynamic performance and cleaner production: the NOx removal process. Journal of Cleaner Production, in press. [17] Hugo A, Pisticopoulos EN. Environmentally conscious longrange planning and design of supply chain networks. Journal of Cleaner Production 2005;13:1428e48. [18] Erol P, Tho¨ming J. ECO-Design of reuse and recycling networks by multiobjective optimisation. Journal of Cleaner Production 2005;13:1449e60. [19] PRES’03 website, http://www.dcs.vein.hu/pres03/scientifiComitee. html [accessed 25.02.05].
References [1] Klemesˇ J, Huisingh D. Advances in cleaner production technologies e special issue PRES’01. Journal of Cleaner Production 2004;12:105e9. [2] Klemesˇ J, Huisingh D. Making progress toward sustainability by using cleaner production technologies, improved design and economically sound operation of production facilities. Journal of Cleaner Production 2005;13:451e4. [3] Klemesˇ J. Editorial. Resources, Conservation and Recycling 2003; 37:173e4. [4] Klemesˇ J, Stehlı´ k P. Recent novel heat integration developments: improved operation, multi-period utilities systems, batch process scheduling, pressure consideration, retrofit, cost factors, energy price forecast and industrial case studies. Applied Thermal Engineering 2003;23:1723e8. [5] Klemesˇ J, Friedler F. Recent novel developments in heat integration e total site, trigeneration, utility systems and costeffective decarbonisation. Case studies waste thermal processing, pulp and paper and fuel cells. Applied Thermal Engineering 2005; 25:953e60.
Jiri Klemesˇ * Centre for Process Integration, CEAS, The University of Manchester, PO Box 88, Manchester M60 1QD, UK Tel.: C44 161 306 4389; fax: C44 161 236 7439. E-mail address: [email protected] Don Huisingh The Center for Clean Products and Clean Technologies at the University of Tennessee, Knoxville, 311 Conference Center Building, Knoxville, TN 37996-4134, USA E-mail address: [email protected] *Corresponding author. Available online 20 June 2005
Editorial
Recent advances in industrial process optimisation 1. Introduction Both well developed countries and the majority of the world’s population living in the developing countries, some of them developing enormously fast and requiring escalating amounts of natural resources and consuming larger and larger share of energy, are becoming increasingly concerned with the impact of their industrial production on the environment and therefore upon the quality of life for all humans. Growing numbers of our society are increasingly aware of the dynamic interconnections and interdependencies of humans with all of the other species. Unless our industrial, economic, political and social systems work increasingly in harmony with the basic ecological systems and the systems that govern them, we will all disappear from this blue planet. This is one of the reasons why both the academic and scientific communities are urged to deliver cleaner, more eco-efficient solutions which are ecologically and economically sound, at the same time, and therefore, have the potential to contribute to sustainability of our societies. As a response to this need, various scientific and research conferences are being held to encourage the cross-fertilisation among people of many nations about the progress, problems and challenges they are experiencing in their quest for developing and implementing cleaner production programmes that contribute to the short and long-term sustainability of their societies. The series of conferences on ‘‘Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction’’ (PRES) is one such opportunity for cross-fertilisation. It was established originally to address issues relevant to process integration in connection with the thermal efficiency of various processes, but it has now been expanded to focus increasingly upon cleaner production, sustainable consumption and sustainability issues. The organisers of the PRES conferences are proud to attract delegates from numerous countries world-wide providing a friendly platform for fast and efficient spreading of novel ideas, processes, procedures and policies. 0959-6526/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.jclepro.2005.05.019
This special issue of Journal of Cleaner Production is the third in a series developed from selected papers of the PRES conferences. The previous issues, based upon papers from PRES conferences were published recently [1,2]. The PRES conference is also collaborating with other well-known journals (see e.g. [3e5]); however, the collaboration with the Journal of Cleaner Production (JCP) is the most intensive as the conference’s main topics are very coherent with those of JCP’s readership. PRES’03 was held, for the first time, outside the European continent. The PRES organisers were very pleased to accept the invitation from the Canadian Society for Chemical Engineering and Chemical Institute of Canada. Consequently, PRES’03 was held jointly with the 53rd Canadian Chemical Engineering Conference e CSChE 2003 in Hamilton, Ontario, Canada. The Canadian organisers led by Andrew Hrymak and Roland Anderson contributed enormously to the success of PRES conference. Delegates from more than 50 countries participated, despite the scary situation just after 9/11. Logically, PRES’03 had a strong North American continental participation; however, Europeans, Asians and Africans were also actively engaged. 2. Overview of the papers included in this issue For this Special Issue of the Journal of Cleaner Production, 11 documents representing various aspects of this field and related inputs are included. The internationality of PRES is reflected by the fact that competitively selected researchers from 13 countries e Belgium, Canada, Germany, Greece, Malaysia, Ireland, Italy, Poland, Romania, South Africa, Spain, Switzerland and the United Kingdom authored the papers for this issue. 3. Three main thematic groups The first part of this Special Issue deals with various aspects of improvement in management of water and
1370
Editorial / Journal of Cleaner Production 13 (2005) 1369e1373
wastewater. It is very interesting to note the very rapid changes and the diverse approaches and applications that are being tested and implemented to provide enough good quality water for both the growing world population and for the expanding agriculture and industry. It is increasingly clear that this is directly related, at least in part, to minimisation of the consumption of water in industry and to the minimisation of wastewater as well. The second part of this issue deals with some specific issues of cleaner production in: pulp and paper mills, production of synthetic natural gas from wood, cleaner sugar production and the removal of harmful NOx. The final part is devoted to important management, LCA and recycling problems: to long-range planning and design of supply chain and ECO-Design of Reuse and Recycling Networks. 3.1. Water and wastewater The first paper, authored by Thoko Majozi from the Republic of South Africa, was titled, ‘‘An effective technique for wastewater minimisation in batch processes’’ [6]. He presented a continuous-time mathematical formulation for freshwater and wastewater minimisation in multipurpose batch industrial plants. The minimisation of wastewater production is achieved through the implementation of numerous recycle and reuse opportunities. A superstructure that entails all the possible recycle and reuse possibilities is used as the basis for the formulation. Initially, the formulation disregards scheduling which forms the basis for the inherent time dimension in water-using batch facilities. This necessitates a priori specification of starting or finishing times, given the duration for each water-using operation. The formulation is then extended to embed wastewater minimisation within an established scheduling framework. This extension, which is a true representation of a practical environment, allows the time dimension to be captured by specifying duration instead of starting and finishing times. In both forms, the formulation is applicable to batch facilities with or without reusable water storage tanks and can readily be extended to multiple contaminant media, although this will be the subject of another publication. Fixing the outlet concentration and the contaminant mass load for the each water-using operation in the absence of central reusable water storage, initially renders the formulation of a nonconvex mixed integer nonlinear program (MINLP) which is linearised exactly to yield a convex mixed integer linear program (MILP). On the other hand, allowing the outlet concentration to vary within predefined bounds while fixing both the water requirement and the contaminant mass load, yields an MINLP formulation for which global optimality cannot be guaranteed in complex problems. The developed formu-
lation is applied to a published literature example as well as to case studies involving production scheduling. A similar problem for dealing with batch processes from a different angle was studied by a group of Malaysian authors, Dominic Chwan Yee Foo, Zainuddin Abdul Manan and Yin Ling Tan from, Universiti Teknologi Malaysia in Skudai, Johor in their article titled, ‘‘Synthesis of maximum water recovery (MWR) networks for batch processes’’ [7]. Their work is based upon application to batch processes, of the well established Pinch Analysis and Process Integration that was designed for use in continuous processes[8]. Substantially, less work has been done on water minimisation problems for batch process systems. The authors present a two-stage procedure for the synthesis of an MWR network for a batch process system, covering both mass transfer-based and non-mass transfer-based water-using processes. The first stage of the synthesis task is to locate the minimum utility targets (freshwater feed and wastewater generation) using a new numerical technique called the time-dependent water cascade analysis (WCA) technique [9]. This technique, which was originally developed for continuous water network analysis has been extended into batch water network systems. In the second stage, a new tool called the timee water network is introduced to synthesis the MWR network to achieve the established utility targets. This new network representation has an advantage of clearly depicting the time-dependent nature of a batch water network. This paper shows that through appropriate adjustments, both minimum utility targeting and network design techniques from continuous processes can be extended into batch water-using systems. Two different process scenarios were analysed, i.e. network with and without water storage systems. The third paper dealing with water and energy simultaneously is from Ireland. Theodore Zhelev authored, ‘‘Water Conservation through Energy Management’’ [10]. The objective of his paper is the simultaneous management of two important industrial resources e energy and water. It addresses a class of industrial processes where heat transfer is accompanied by mass transfer (water evaporation and condensation) with special attention where the transfer of heat is a limiting stage. These processes are considered in integration with all related processes and subsystems. More specifically, the set of processes and subsystems include cooling systems, systems of contact economizers for flue gas energy recovery, scrubbers, direct steam heaters, driers, related systems of coolers and the heat exchanger network. The proposed preliminary design procedure is based upon concepts and tools related to an advanced Pinch technology specially modified for consideration of simultaneous heat and mass transfer. The manipulated parameters include process latent and sensible heat loads and system’s structural changes with
Editorial / Journal of Cleaner Production 13 (2005) 1369e1373
efficiency criteria allowing sacrifice of quantity for quality of performance. Two specific procedures allow targeting of maximum flue gas energy recovery and minimum temperature of cooling water, providing guidance to structural design and system operation. The application of proposed methodology is designed to achieve water conservation through minimisation of water evaporation losses. Its significance is demonstrated through three industrial applications (a power station, a brewery and a tissue factory). The fourth paper focuses upon an application of recently very popular genetic optimisation algorithm. Vasile Lavric, Petrica Iancu and Valentin Plesu, researchers from Belgium and Romania submitted a document titled, ‘‘Genetic Algorithm Optimization of Water Consumption and Utilization System Topology’’ [11]. The Genetic Algorithm Optimisation (GAO) approach that they employ was used for generation of a best water network topology with a minimum freshwater usage, complying, at the same time, with all constraints. An optimal water network could be seen as an oriented graph, starting from unit operations with no contaminant at entrance, each unit operation ‘‘i’’ receiving streams from possibly (but not inevitably) all previous operations ‘‘j’’ only ( j Z 1, 2.i ÿ 1), and sending streams to probably (but not necessarily) all next operations ‘‘j’’ ( j Z i C 1, i C 2.N ). The mathematical model describing the unit ‘‘i’’ is based upon total and contaminant species mass balances, together with the input and output constraints. The GAO uses each internal flow as a gene, defining a chromosome from all these flows. The constraints are to comply with during the population generation, by simply eliminating those individuals outside the feasible domain. The individuals can interbreed according to their frequency of selection, using the one-point crossover method. The objective function is the reduction of the total freshwater consumption. Comparisons with the results of water pinch and mathematical programming methods are made. In the discussion of the pros and cons of this approach the authors highlight the classes of problems where application of this approach is beneficial. The second group of papers starts with a Canadian contribution from Montre´al and Edmonton. Michal Dabros, Michel Perrier, Fraser Forbes, Martin Fairbank and Paul Stuart submitted a paper titled, ‘‘ModelBased Direct Search Optimisation of the Broke Re-Circulation System in Newsprint Mill’’ [12]. Their work explores the dynamic modelling of the papermaking section of an integrated newsprint mill and the subsequent application of two direct search methods in a proof-of-concept optimisation study of broke recirculation strategies. The effect of the current broke recirculation policy on the mixed pulp properties at the paper machine head boxes was quantified using the dynamic simulation and an objective function which
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reflected the rate of change in measurable (flow, consistency and temperature) and immeasurable (total dissolved solids and fibre length distribution) parameters. Again a Genetic Algorithm as in the previous paper and the Nelder-Mead simplex methods were then linked dynamically to the simulation and used to find improved ways of re-circulating broke pulp. The profile of the changes to the broke ratio was modelled using a quadratic function and a second order transfer function; as a result the coefficients of these functions were optimised. An implementation study of the optimised operating strategy has been recommended to the newsprint mill. It is expected that by reducing variability at the paper machine headbox, the overall machine stability will increase, effectively leading to a lower sheet breakage frequency. Achieving this goal, in the real process, increased the mill’s productivity and noticeably reduced its negative environmental impacts. The following contribution deals with a paper mill as well. Xavier Turon, Jalel Labidi, Jean Paris from Girona, Spain and Montre´al, Canada in their paper ‘‘Model-Based Direct Search Optimisation of the Broke Re-Circulation System in Newsprint Mill’’ [13] used a process simulation of a high-grade coated paper mill to carry out a process integration study. Data necessary to calibrate and validate the simulation developed with Cadsim PlusÒ software were obtained by: measurements, samples analysis and estimations through partial and local mass balances. The simulation was designed to permit grade changes to reproduce variations in mill operations. The simulation was used to support process studies to optimise water and raw material’s consumption and to evaluate results obtained by mathematical optimisation. Different scenarios were studied in order to evaluate the feasibility and the effects of process redesign of the mill operation. A Genetic Algorithm was again used for optimisation. Satisfactory solutions which reduce water consumption and fibre losses were implemented into the process simulation to evaluate their technical feasibility. Alexis Duret, Claude Friedli, Franc¸ois Mare´chal from Swiss Federal Institute of Technology, Lausanne explored diverse ways of wood gasification in their paper ‘‘Process design of Synthetic Natural Gas (SNG) production using wood gasification’’ [14]. The process design of a 10e20 MWth Synthetic Natural Gas (SNG) production process from wood was performed. Combining process modelling and process integration techniques, this study proceeded via the following stages: (i) thermodynamic modelling: mass, energy balances and simulation of the wood gasification, the machination and the purification units; (ii) process integration that identifies the energy saving opportunities and prepares a thermo-economic optimisation. They demonstrated that the process can transform wood into pipeline quality methane with a thermal efficiency of
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57.9% based on the Lower Heating Value (LHV). The process integration study showed that the heat surplus of the process can be used to almost satisfy the mechanical work required by the process; only 7% of the mechanical needs will have to be from an external source. An Italian group from Giuseppe Vaccari, Giulio Sgualdino, Elena Tamburini, Giorgio Pezzi, Piercarlo Citterio, Roberto Verardi and Krzysztof Urbaniec from Poland submitted a paper titled, ‘‘ New eco-friendly proposal for the crystallization of beet raw juice’’ [15]. Their work focuses upon different strategies with the objective of completely eliminating the traditional calcocarbonic purification process by addressing the wellknown problems related to the utilization of lime and the production of carbonation sludge. As a result of their research, they proposed: (i) the direct crystallization of raw juice, (ii) the crystallization of micro filtered raw juice, and (iii) the chromatographic separation of the raw juice. In all cases, they utilized the cooling crystallization technique. To complete the picture of the possible solutions to be adopted for the elimination of the traditional purification process, they comprehensively evaluated laboratory tests and pilot plant results for processing raw juice via the following steps: (i) micro-filtration and softening of the raw juice; (ii) first cooling crystallization with the objective of obtaining commercial white sugar; (iii) chromatographic separation of the run-off of the first crystallization step; (iv) decolourization of the extract (rich-sugar fraction); and (v) cooling crystallization with the objective of obtaining commercial white sugar and recycling of the previously produced sugar. The results obtained, as well as the proposed flow-sheet and a comparison with the previous strategies, are presented and discussed. Natassa Dalaouti and Panos Seferlis from Chemical Process Engineering Research Institute in Thermi e Thessaloniki developed novel ways to remove harmful NOx emissions that are addressed in their paper titled, ‘‘Design sensitivity of reactive absorption units for improved dynamic performance and cleaner production: The NOx removal process’’ [16]. The reactive absorption of nitrogen oxides from gas streams has received extensive attention due to stringent environmental regulations that govern this pollutant. The operating and environmental specifications of the process have to be met within the context of process disturbances. A study of the effect of different column design configurations and control structures on the disturbance rejection properties of the NOx removal system was performed. Their work provided a useful and powerful tool for the efficient control of NOx emissions not only through the fine-tuning and monitoring of the implemented control system but also through the selection of the proper absorber configuration and operating mode for the unit. The proposed method combines the benefits
of an accurate and detailed modelling of the complex reactive absorption process of NOx removal and the results of a systematic controllability analysis to guarantee smooth operation, efficient disturbance rejection and consequently a cleaner production process. The third group of papers begins with an article from Imperial College of Science and Medicine, London, authored by Andre Hugo and Stratos Pistikopulos, titled, ‘‘Environmentally Conscious Long-Range Planning and Design of Supply Chain Networks’’ [17]. The article includes a mathematical programming-based methodology for the explicit inclusion of life cycle assessment (LCA) criteria as part of strategic investment decisions related to the design and planning of supply chain networks. By considering the multiple environmental concerns together with the traditional economic criteria, the planning task is formulated as a multi-objective optimisation problem. Over a long-range planning horizon, the methodology utilizes mixed integer modelling techniques to address strategic decisions involving the selection, allocation and capacity expansion of processing technologies and assignment of transportation links required to satisfy the demands at the markets. At the operational level, optimal production profiles and flows of material between various components within the supply chain are determined. As such, the formulation presented combines the elements of the classical plant location and capacity expansion problems with the principles of LCA to develop a quantitative decisionsupport tool for environmentally conscious strategic investment planning. Fundamental to the overall approach is the formulation of an appropriate environmental performance objective to guide strategic decisionmaking. For this task, a recently developed method of impact assessment, the Eco-Indicator ’99 method, was incorporated within the quantitative LCA model. The last document was submitted by Pinar Erol and Jorg Tho¨ming from University of Bremen in Germany, titled, ‘‘ECO-Design of Reuse and Recycling Networks by Multiobjective Optimisation’’ [18]. An ECO-optimised reuse of process liquors addresses the financial gain and the effective use of resources. In processes that have a potential for process liquor recovery, the optimisation of economic and minimisation of environmental burdens can be realised by an ECO-optimal design of the reuse and recycling network (RRN). In this document, a procedure for synthesizing such an RRN for a metal finishing process is presented. The simultaneous analysis of environmental impacts sensitivity (SAEIS) based on a superstructure approach, combined with multi-objective optimisation is performed by mixed integer nonlinear programming (MINLP). This allows an ‘‘ECOeECO’’ trade-off i.e. total annualised cost and environmental impacts are minimised simultaneously. By varying the weighting factor, different RRN alternatives were generated. In the metal finishing case study, applying
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the ECO-Design by multi-objective optimisation was combined with LCA-tool as a hybrid approach: thereby different RRN alternatives were received by varying the weighting factor for the representative impact score and the cost in the objective function. A replacement of either the standard or closed-loop systems by an openloop system will result to be the most environmentally benign alternatives and with a reasonable return from investment.
4. Conclusions We believe that the papers in this Special Issue of Journal of Cleaner Production will be of interest and relevance to a broad range of readers in this field and will bring the PRES Conference series to their attention. The help of all collaborators and the ISC members [19] is gratefully acknowledged, both for actively contributing to the conference and for taking part in the editorial process to develop the papers for official publication within the Journal of Cleaner Production. A special appreciation is expressed to all authors for their contributions. We would like to continue and further develop the mutual collaboration between the Journal of Cleaner Production and the PRES conference the series. The seventh PRES’04 conference was held in Prague, the Czech Republic, again jointly with CHISA 2004 and another Special Issue is being developed. The eighth PRES’05 was held jointly with ICheaP-07 in Taormina, Sicily, Italy and the ninth PRES 2006 will again return to ‘‘golden Prague’’ in August 2006.
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[6] Majozi T. An effective technique for wastewater minimisation in batch processes. Journal of Cleaner Production 2005;13:1374e80. [7] Foo CY, Manan ZA, Tan LY. Synthesis of maximum water recovery network for batch process systems. Journal of Cleaner Production 2005;13:1381e94. [8] Wang YP, Smith R. Wastewater minimization with flow rate constraints. Transactions of the Institute of Chemical Engineers, Part A 1995;73:889e904. [9] Manan ZA, Foo DCY, Tan YL. Targeting the minimum water flow rate using water cascade analysis technique. AIChE Journal 2004;50(12):3169e83. [10] Zhelev TK. Water conservation through energy management. Journal of Cleaner Production 2005;13:1461e70. [11] Lavric V, Iancu P, Plesu V. Genetic algorithm optimisation of water consumption and wastewater network topology. Journal of Cleaner Production 2005;13:1395e405. [12] Dabros M, Perrier M, Forbes F, Fairbank M, Stuart’ P. Modelbased direct search optimisation of the broke re-circulation system in newsprint mill. Journal of Cleaner Production 2005; 13:1406e13. [13] Turon X, Labidi J, Paris J. Simulation and optimisation of a high grade coated paper mill for cleaner production. Journal of Cleaner Production 2005;13:1471e80. [14] Duret A, Friedli C, Mare´chal F. Process design of synthetic natural gas (SNG) production using wood gasification. Journal of Cleaner Production, in press. [15] Vaccari G, Sgualdino G, Tamburini E, Pezzi G, Urbaniec K. New eco-friendly proposal for the crystallization of beet raw juice. Journal of Cleaner Production 2005;13:1414e27. [16] Dalaouti N, Seferlis P. Design sensitivity of reactive absorption units for improved dynamic performance and cleaner production: the NOx removal process. Journal of Cleaner Production, in press. [17] Hugo A, Pisticopoulos EN. Environmentally conscious longrange planning and design of supply chain networks. Journal of Cleaner Production 2005;13:1428e48. [18] Erol P, Tho¨ming J. ECO-Design of reuse and recycling networks by multiobjective optimisation. Journal of Cleaner Production 2005;13:1449e60. [19] PRES’03 website, http://www.dcs.vein.hu/pres03/scientifiComitee. html [accessed 25.02.05].
References [1] Klemesˇ J, Huisingh D. Advances in cleaner production technologies e special issue PRES’01. Journal of Cleaner Production 2004;12:105e9. [2] Klemesˇ J, Huisingh D. Making progress toward sustainability by using cleaner production technologies, improved design and economically sound operation of production facilities. Journal of Cleaner Production 2005;13:451e4. [3] Klemesˇ J. Editorial. Resources, Conservation and Recycling 2003; 37:173e4. [4] Klemesˇ J, Stehlı´ k P. Recent novel heat integration developments: improved operation, multi-period utilities systems, batch process scheduling, pressure consideration, retrofit, cost factors, energy price forecast and industrial case studies. Applied Thermal Engineering 2003;23:1723e8. [5] Klemesˇ J, Friedler F. Recent novel developments in heat integration e total site, trigeneration, utility systems and costeffective decarbonisation. Case studies waste thermal processing, pulp and paper and fuel cells. Applied Thermal Engineering 2005; 25:953e60.
Jiri Klemesˇ * Centre for Process Integration, CEAS, The University of Manchester, PO Box 88, Manchester M60 1QD, UK Tel.: C44 161 306 4389; fax: C44 161 236 7439. E-mail address: [email protected] Don Huisingh The Center for Clean Products and Clean Technologies at the University of Tennessee, Knoxville, 311 Conference Center Building, Knoxville, TN 37996-4134, USA E-mail address: [email protected] *Corresponding author. Available online 20 June 2005