Ferenc Friedler

University of Pannonia, Veszprém, Gyulafirátót, Veszprém, Hungary

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Publications (123)167.74 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The P-graph (process graph) framework is an effective tool for process-network synthesis (PNS). Here we extended it to multi-period operations. The efficacy of the P-graph methodology has been demonstrated by numerous applications. The unambiguous representation of processes and the availability of the axioms defining combinatorially feasible structures facilitates the development of efficient algorithms to determine maximal structures, solution structures, and optimal structure for processes. However, it is presumed that single-period operation prevails. It implies that the operating conditions and the load of each operating unit remain unchanged, i.e., steady-state operation. This is usually true for the chemical industry but often not in agriculture or where seasonal effects are important. The current work proposes a multi-period operation wherein the load of operating units varies from period to period to accommodate demand, assuming operating conditions remain steady in each period. A modeling technique is proposed to represent operating units in the multi-period operation. The different periods are connected by “fictitious” streams, which ensures, that the unit is sized properly.
    Computers & Chemical Engineering 05/2015; DOI:10.1016/j.compchemeng.2015.04.037 · 2.45 Impact Factor
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    ABSTRACT: We present a computer-aided methodology for designing sustainable supply chains using the P-graph framework to develop supply chain structures which are then analyzed using cost, the cost of producing electricity, and two sustainability metrics: the ecological footprint and the emergy input. These metrics respectively represent environmental burden in terms of land use and energy resources. The results are the continuation of a research effort between members of the Office of Research and Development (ORD) of the U.S. EPA and the University of Pannonia. In earlier work, the basis of the research, the integration of supply chain design and sustainability were presented. There, the P-graph framework provided a mathematically rigorous procedure for synthesizing optimal and alternative suboptimal networks subject to profitability and ecological footprint criteria. In this work the effort is extended with another sustainability metric, emergy. Emergy, a measure of the energy used up in transformations directly and indirectly to make a product or maintain a service, was assessed for each energy production supply chain. The proposed methodology demonstrates the optimal design of a supply chain which provides electric power and heat to an agricultural region with agricultural wastes that can potentially be recovered as renewable resources. The results of the study indicate that, compared to using electricity from the grid and/or natural gas, renewable energy resources can yield substantial cost reductions of up to 17%, as well as significant ecological footprint and emergy reductions. These results indicate that it is possible to design more sustainable supply chains that are also cost-effective.
    Journal of Cleaner Production 02/2015; 94. DOI:10.1016/j.jclepro.2015.02.011 · 3.84 Impact Factor
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    ABSTRACT: A new modeling technique is presented here for handling multi-period operations in the process-network synthesis (PNS) problem by the P-graph (process graph) framework. The P-graph is both a representation and a methodology. It has been demonstrated by several applications that P-graphs are useful modeling tools in various areas. The unambiguous representation of processes by P-graphs and the availability of the axioms defining the combinatorially feasible structures have facilitated the development of efficient algorithms to determine the maximal structure, the solution structures, and the optimal structure of the network for the process of interest. Until now, it was implicitly assumed that single-period operations prevail. This implicitly means that the operating conditions and the load remain unchanged throughout its operation, i.e., steady-state operation is maintained. This assumption is usually true for the chemical industry, but it may be false in other areas where seasonal effects are important such as agriculture. The current work proposes the use the P-graph framework with multi-period operation wherein the load of operating units may vary from period to period to accommodate the changing demands under the premise that the operating conditions remain steady within each period. Subsequently, a modeling technique is proposed to represent operating units in the multi-period operation. The basic concept is to separately represent the physical body of operating units and the operations themselves in each period. The investment and the operating cost must also be separated for operating units, and we have to make sure that the maximum capacity of the multi-period unit is not violated. Surprisingly, no need to dramatically change or augment the basic structure of the P-graph methodology, e.g. with a new type of multi-period unit, but the already available constituents are adequate. This also demonstrates the generality of the framework. A simple example of evaluating the investment in a single equipment unit applicable is presented. This is followed by a more complex case study on optimal planning of the energy production system appropriate for an agricultural region in Central Europe. Together both illustrate the new modeling technique. Energy production as well as available feedstock vary with the seasons raising a very interesting design problem. Acknowledgement: we acknowledge the support of the U.S. EPA, Office of Research and Development, and the Hungarian State and the European Union under the TAMOP-4.2.2.A-11/1/ KONV-2012-0072.
    14 AIChE Annual Meeting; 11/2014
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    ABSTRACT: Glycerol is a waste by-product from the transesterification involved in biodiesel synthesis. Converting it to high value-added products can ease its over-supply. This can be accomplished by reforming glycerol into high purity hydrogen for which nickel-based catalysts are most often deployed. Nevertheless, the coexistence of both acidic and basic active sites renders it difficult to gain in-depth understanding of its reaction pathways. Exhaustive identification of feasible pathways allows us to design a Ni catalyst, thereby facilitating the practical implementation of glycerol steam reforming. The current contribution explores nineteen reaction steps, including the most abundant intermediates derived from glycerol, based on a dual-active site mechanism adapted from Cheng et al. (2011). Six independent pathways and twenty-one acyclic pathways have been generated through a graph-theoretic method based on P-graphs within one second on a PC (Pentium 4, CPU 3.06 GHz, and 1 GB RAM). This makes it possible to establish a kinetic model via analysis based on the Langmuir-Hinshelwood formalism, thereby providing a platform for rational catalyst design. Reference: K.C. Cheng, Y. F. Say, and A. A. Adesina, Catalysis Today 178 (2011) 25-33.
    13 AIChE Annual Meeting; 11/2013
  • Ferenc Friedler, Ka Ming Ng
    11/2013; DOI:10.1016/j.coche.2013.10.008
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    ABSTRACT: A method and software are proposed for optimal building-evacuation-route planning in terms of identifying evacuation routes and scheduling of evacuees on each route. First, the building-evacuation routes are represented by a P-graph, which gives rise to a time-expanded process-network synthesis ( ) problem that can be algorithmically solved by the P-graph framework. In the proposed method, each location and passage in the building is given by a set of attributes to be taken into account in the evacuation-route planning. The evacuation time is calculated as a minimum cost of the corresponding . In addition to the globally optimal solution, the P-graph framework provides the n-best sub-optimal solutions. The validity of the proposed method is illustrated by two examples.
    Fire Safety Journal 10/2013; 61:338-347. DOI:10.1016/j.firesaf.2013.09.023 · 1.06 Impact Factor
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    ABSTRACT: Methodology and computer aid are proposed for designing sustainable supply chains in terms of sustainability metrics by utilizing the P-graph framework. The methodology is an outcome of the collaboration between the Office of Research and Development (ORD) of the U.S. EPA and the research group led by the creators of the P-graph framework at the University of Pannonia. The integration of supply chain design and sustainability is the main focus of this collaboration. A recent extension to the P-graph framework provides a mathematically rigorous procedure for synthesizing the complete set of Pareto optimal networks subject to multiple objectives and constraints, which include profitability and sustainability in the proposed methodology. Specifically, to evaluate the sustainability of a given process under construction including its supply chain, sustainability metrics are incorporated into the design procedure. The proposed methodology and the software are demonstrated with the optimal design of a supply chain for providing heat and electric power to an agricultural region with relatively limited land area where agricultural wastes can potentially be recovered as renewable resources. Possible sources of heat and electricity included electricity from the Hungarian grid, and heat and electricity generated from natural gas, corn, corn silage, grass silage, or wood or some combination of these sources. Each supply chain was ranked according to cost, and assessed environmental impacts using the ecological footprint (representing land use burden), and emergy (representing energy resource burden). Decisively feasible supply chains were found with cost variations of +2% to -17% compared to “business as usual” scenarios, i.e., using only natural gas and electricity from the Hungarian grid. For these supply chains, the sustainability profile as represented by the ecological footprint varied from +8% to -78%, and the emergy results ranged from -54% to -93%. Most importantly, it appeared feasibly possible to design supply chains for heat and electricity generation which were both cheaper and more sustainable than the supply chain currently in use.
    2013 AIChE Spring National Meeting; 05/2013
  • Miguel Bagajewicz, Ferenc Friedler
    Industrial & Engineering Chemistry Research 01/2013; 52(1):1-4. DOI:10.1021/ie3034009 · 2.24 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The present work proposes a computer-aided methodology for designing sustainable supply chains in terms of sustainability metrics by utilizing the P-graph framework. The methodology is an outcome of the collaboration between the Office of Research and Development (ORD) of the U.S. EPA and the research group led by the creators of the P-graph framework at the University of Pannonia. The integration of supply chain design and sustainability is the main focus of this collaboration. The P-graph framework provides a mathematically rigorous procedure for synthesizing optimal and alternative suboptimal networks subject to multiple objectives and constraints, which include profitability and sustainability in the proposed methodology. Specifically, to evaluate the sustainability of a given process under construction including its supply chain, sustainability metrics are incorporated into the design procedure. The proposed methodology is demonstrated with the optimal design of a supply chain for providing heat and electric power to an agricultural region with relatively limited land area where agricultural wastes can potentially be recovered as renewable resources. The objective functions for optimization comprise the profit and the ecological footprint. The results of the study indicate that, compared to using electricity from the grid and/or natural gas, using renewable energy resources can yield substantial cost reductions of up to 5%, as well as significant ecological footprint reductions of up to 77%. It may, therefore, be possible to design more sustainable supply chains that are both cost-effective and less environmentally damaging.
    Industrial & Engineering Chemistry Research 11/2012; 52(1):266–274. DOI:10.1021/ie3013264 · 2.24 Impact Factor
  • Mate Barany, Botond Bertok, L T Fan, Ferenc Friedler
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    ABSTRACT: The determination of reaction pathways is one of the most important functions that should be performed in exploring the kinetics of catalyzed chemical reactions or biochemical reactions, the latter being generally catalyzed by enzymes. It is proven that the terms, "type-I extreme pathway" and "structurally minimal pathway", both introduced to characterize the kinetics of a catalyzed reaction are equivalent. These two terms are based on two distinct methodologies, one mainly rooted in convex analysis and the other in graph theory. The equivalence promises further even more effective methods for reaction-pathway identification by synergistic integration of existing ones.
    Bioprocess and Biosystems Engineering 11/2012; DOI:10.1007/s00449-012-0847-5 · 1.82 Impact Factor
  • Ferenc Friedler, Ka Ming Ng
    11/2012; 1(4):418–420. DOI:10.1016/j.coche.2012.10.005
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    ABSTRACT: The formation of HBr has long been widely regarded as proceeding via a chain-reaction pathway comprising the initiation step, activated catalytically, thermally, electrically, photonically or collisionally, the propagation steps, and termination step. In recent years, however, it has been recognized that this chain-reaction pathway or mechanism does not give rise to stoichiometrically closure, thereby violating the axiomatic laws of mass conservation and stoichiometric constraint of chemical reactions. Proposed herein is a novel chain-reaction mechanism involving the activation of hydrogen in addition to that of bromine to initiate the chain. By resorting to the mathematically rigorous, graph-theoretic algorithmic method based on a unique bipartite graph, P-graph (process graph), two stoichiometrically feasible independent pathways and one acyclic combined pathway have been obtained from this novel chain-reaction mechanism. The algorithmic method deployed is based on the two sets of axioms, one being the set of 6 axioms of feasible reaction pathways and the other being the set of 7 axioms of combinatorially feasible networks, and graph representation of reaction steps in terms of P-graphs.
    12 AIChE Annual Meeting; 10/2012
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    ABSTRACT: A collaboration consisting of the Office of Research and Development (ORD) of the U.S. EPA and the research group led by the founders of the P-graph framework at the University of Pannoniahas developed a methodology for designing sustainable supply chains based on an optimization using the p-graph framework constrained by integrated sustainability indicators and engineering costs. The result was a powerful methodology for designing cost-effective and environmentally sustainable supply chains. We illustrated the methodology with a prototype supply chain designed to produce heat and electricity for a generic district in Hungary. Possible sources of heat and electricity included electricity from the Hungarian grid, and heat and electricity generated from natural gas, corn, corn silage, grass silage, or wood or some combination of these sources. Twenty-one different supply chains, each capable of producing 18 TJ per year of heat and 7.2 TJ per year of electricity were found. Each supply chain was ranked according to cost, and assessed environmental impacts using the ecological footprint (representing land use burden), and emergy (representing energy resource burden). Decisively feasible supply chains were found with cost variations of +2% to -17% compared to “business as usual” scenarios i.e. using only natural gas and electricity from the Hungarian grid. For these supply chains, the sustainability profile as represented by the ecological footprint varied from +8% to -78%, and the emergy results ranged from -54% to -93%. Both comparisons were done in contrast to the conventional natural gas/electricity from the Hungarian grid. Most importantly, it appeared feasibly possible to design supply chains for heat and electricity generation which were both cheaper and more sustainable than the supply chain currently in use.
    12 AIChE Annual Meeting; 10/2012
  • Botond Bertok, Mate Barany, Ferenc Friedler
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    ABSTRACT: The primary aim of process-network synthesis, or PNS in short, is to determine the best process network achieving a desired goal, e.g., producing a set of desired products or satisfy demands. PNS has a long history, and numerous methods for executing it are available. Its acceleratedly increasing importance can be attributed to the need to respond to the rapid emergence of new technologies and fast changes in the economic environment. It is highly desirable that any corporation be able to ascertain if a new technology is viable for its business as well as to assess if its current technology remains sustainable in the changing environment. Herein, a novel method and software for PNS are proposed for generating, optimizing, and analyzing alternative process designs at the conceptual level. The method is illustrated by synthesizing alternative process designs with different network structures for the production of butanol, ethanol, and acetone from grains. Furthermore, the sustainability of the resultant process designs is analyzed. This is executed by varying the payout period and the production rate, i.e., load.
    Industrial & Engineering Chemistry Research 10/2012; 52(1):166–171. DOI:10.1021/ie301155n · 2.24 Impact Factor
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    ABSTRACT: The current work reveals a methodology that provides an adequate basis to portray and model supply chains mathematically and formally as well as to synthesize optimal and alternative supply scenarios algorithmically while taking into account structural redundancy. The proposed methodology is based on the combinatorial foundations of algorithmic process synthesis or more specifically on the P-graph framework. A biodiesel supply network involving blending and transportation serves as an illustrative example. A novel algorithm generates the mathematical model and alternative solutions to increase reliability of supply scenarios. Major steps of the generation are the structure generation and estimation of reliability of a supply scenario.
    Industrial & Engineering Chemistry Research 10/2012; 52(1):181–186. DOI:10.1021/ie301393d · 2.24 Impact Factor
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    ABSTRACT: An effective strategy comprising two phases is proposed to determine the thermodynamically dominant pathways in a metabolic network of a given phenotype, involving several metabolic reactions. In the first phase, stoichiometrically feasible metabolic pathways are exhaustively identified through the flux balance analysis and the graph-theoretic method based on P-graphs. In the second phase, thermodynamically dominant pathways are selected from these stoichiometrically feasible metabolic pathways on the basis of the Gibbs free energy change of reaction. The proposed strategy’s efficacy is demonstrated by applying it to two E. coli models: one is for maximal acetate and ethanol production, and the other is for maximalpoly(3-hydroxybutyrate) production.
    Industrial & Engineering Chemistry Research 07/2012; 52(1):222–229. DOI:10.1021/ie300652h · 2.24 Impact Factor
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    ABSTRACT: A reaction-pathway identification procedure has two distinct phases. The first phase enumerates exhaustively the feasible candidate pathways, and the second phase identifies the ultimate feasible pathway or pathways among them. Probably the most efficient way to execute the first phase is to algorithmically generate the networks of feasible candidate pathways from a predefined set of plausible elementary reactions. The available algorithmic methods for this purpose can be roughly grouped into two major classes, one based on graph theory and the other on linear algebra. Both classes of methods consider any chemical reaction system as a network of elementary reactions, thereby implying that the two classes are interrelated. This paper studies the linear algebraic concept termed direct mechanism introduced in the mid-eighties and the graph-theoretical concept termed structurally minimal pathway introduced two decades later. Herein, it has been formally proven that the two concepts are equivalent.
    Journal of Mathematical Chemistry 05/2012; 50(5). DOI:10.1007/s10910-012-9974-0 · 1.27 Impact Factor
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    ABSTRACT: Hitherto, no attempt has been made to identify exhaustively feasible pathways for any mechanism of a given reaction catalyzed by a catalyst with multiactive sites. Two stoichiometically exact and definitely feasible mechanisms have been proposed to date for the hydrogenation of ethylene to ethane on biactive-site or triactive-site platinum catalysts. One comprises seven elementary reactions, and the other comprises eight elementary reactions; nevertheless, both mechanisms involve competitive as well as noncompetitive adsorption. Any of these mechanisms gives rise to a multitude of feasible catalytic pathways. The present work exhaustively identifies such feasible pathways by resorting to the inordinately efficient graph-theoretic algorithm based on P-graphs (process graphs). The efficacy of this algorithm has been amply demonstrated by successfully deploying it for several catalysts with single-active sites, but has never been deployed for catalysts with multiactive sites as in the current work. The availability of exhaustively identified feasible pathways for both mechanisms renders it possible to stipulate that the hydrogenation of chemisorbed chemisorbed C2H5 is the rate-controlling step: This step is contained in either mechanism.
    Industrial & Engineering Chemistry Research 02/2012; 51:2548-2552. DOI:10.1021/ie200718w · 2.24 Impact Factor
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    ABSTRACT: The efficient management of renewables to reduce utilisation of energy sources with high impact on the environment (e.g. fossil fuels) is a widely studied research topic. The core of the complexity for this kind of planning and operational problems is the variety and variation on both the supply and demand side. In a typical case study both high and low temperature heat, and electricity demands are present and they vary through the time. This study applies mathematical programming for the rescheduling of the operations in order to minimise the utility consumption. It reduces the impact on the environment by exploiting an inherent flexibility of the processes on the demand side. Some operations can be shifted in time if the site has enough of a certain resource in stock. An example is the milling of wheat at a storehouse (production of flour) or the washing of laundry at a hotel (clean towels). A flexible operation can be rescheduled; however, the size of the stock implies a limitation for the shifting in time. The optimal solution of the operational level can depend on the design parameters. A retrofit sensitivity analysis has been done, where the optimal schedule was identified for different design conditions.
    15th International Conference on Process Integration, Modelling and; 01/2012
  • Tibor Holczinger, Mate Hegyhati, Ferenc Friedler
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    ABSTRACT: Heat integration of continuous processes is a widely studied research area, where many approaches have been developed to minimize cold and hot utility usage. Batch processes require additional consideration for the planning of the heat exchanger network: since the flows are not always present in the system, their timing has to be considered as well. Both heat integration and scheduling of batch processes are highly complex, their combination is expected to be even higher. Several papers have already addressed the integrated problem in the last decade (Majozi, 2006, Chen and Chang, 2009, Halim and Srinivasan, 2011). Adonyi et. al. (2003) has presented an algorithm to minimize the utility usage for a given time horizon. Their approach assumed, however, that heat exchangers are present for all of the hot-cold stream pairs. Moreover, each hot or cold stream was allowed to be matched with only one hot or cold stream, respectively, further heat demands of the stream had to be satisfied from utilities. The aim of this work is to present an extension of Adonyi et. al.'s approach by allowing the streams to have heat exchanges with multiple other streams. The newly presented approach also takes into account the limitation on the number of available heat exchangers and their scheduling.
    15th International Conference on Process Integration, Modelling and; 01/2012

Publication Stats

1k Citations
167.74 Total Impact Points

Institutions

  • 1995–2015
    • University of Pannonia, Veszprém
      • • Department of Computer Science and Systems Technology
      • • Faculty of Information Technology
      Gyulafirátót, Veszprém, Hungary
  • 2012
    • Lands Department of The Government of the Hong Kong Special Administrative Region
      Hong Kong, Hong Kong
  • 1992–2011
    • Kansas State University
      • • Department of Grain Science and Industry
      • • Department of Chemical Engineering
      Kansas, United States
  • 2006
    • University of Pretoria
      • Department of Chemical Engineering
      Pretoria, Gauteng, South Africa
  • 2005
    • The University of Manchester
      • Centre for Process Integration
      Manchester, England, United Kingdom
  • 2002
    • Polytechnic University of Catalonia
      • Department of Chemical Engineering (EQ)
      Barcino, Catalonia, Spain
  • 1993–1995
    • Hungarian Academy of Sciences
      • Systems and Control Lab
      Budapeŝto, Budapest, Hungary