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Microalgae continues emerging as a promising feedstock for the development of biorefineries. Since there are numerous possible technologies that can be used to process microalgae and produce a wide variety of products and co-products, it is necessary to develop an efficient approach for the generation and screening of processing technologies. This work introduces a combined methodology for the synthesis and analysis of topological pathways for the processing of microalgae based on main approaches of hierarchical and mathematical programming-based process synthesis. The methodology uses a hierarchical approach that starts with top-level data and focuses attention and effort on the promising pathways integrating various process synthesis and optimization concepts such as forward-backward branching, superstructure optimization, and in-depth analysis for high-priority pathways. A case study is solved for the production of diesel-like fuel from microalgae biomass. [ABSTRACT FROM AUTHOR]

BACKGROUND Bioethanol is a green fuel considered to be a sustainable alternative to petro-derived gasoline. The transport sector contributes significantly to carbon dioxide emission and consequently has a negative impact on the air quality and is responsible for the increase of the greenhouse effect. The availability of environment-friendly and economical fuels is a worldwide priority. The separation process is a significant technology in the production of fuel grade ethanol in terms of both operating and capital costs. In the present work an alternative distillation sequence for bioethanol separation is presented. The steady state performance and the dynamic beavior are analyzed compared with the classical configuration reported in the literature. RESULTS Ethanol-water azeotropic separation represents a challenge for bioethanol purification. Usually a three column sequence is used to obtain fuel grade bioethanol by extractive distillation. In order to reduce bioethanol purification cost a two column separation sequence is proposed. This configuration shows a 10% saving in capital costs together with higher ethanol recovery and better control properties compared with the classical three column sequence. CONCLUSIONS Based on the steady state and dynamic results obtained, the two-column configuration represents a valid alternative to the classical configuration for the separation of bioethanol. © 2014 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Process synthesis and design of plant operation are related topics but current industrial practice solves these problems sequentially. The implication of this sequential strategy may result in design of processing systems which are very hard to control. This paper presents a discussion on drivers for an integrated approach and outlines the challenges in formulation of such a multi-objective synthesis problem. This discussion is viewed in relation to some of the changing trends in the industry. Significant results have been published which in different ways seek to handle the integrated problem. Further, advancements in control algorithms and software have widened the range of feasible operation and control for strongly interconnected production systems. In light of these advances in different areas of the field, recommendations for further research and initiatives for development of an integrated approach are given with focus on how new results on the short term can improve industrial practice. [ABSTRACT FROM AUTHOR]

Chemical processes and their flow-sheets are systems and as with all systems one cannot optimise each part alone and expect to get an optimal process. One also has to take into account the connections and interactions between the parts of the systems in order to achieve the global optimum. In this paper fundamental thermodynamics will be used to show how to achieve an optimal solution. A coal-to-liquids (CTL) process will be used to illustrate the method. The overall material balance for a process will be looked at first. This material balance must include the constraints such as the energy (heat and work) balance and thus must include the feed streams that supply utilities, such as heat and electricity to the process. The best material balance ensures that as much of the feed material ends up in the product. In the examples discussed, focus will be on ensuring that as much of the carbon in the feed as possible ends up in the hydrocarbon product; the carbon from the feed that does not report to the product is emitted from the process as CO 2 which is undesirable for a number of reasons. The resulting overall material balance is then regarded as the process target, since it is the “best” material balance. Furthermore, the manner in which energy (heat and work) is added or removed from a process, affects the material balance by introducing irreversibilities. The greater these irreversibilities are, the further the process operates from the process target, implying that the process produces more CO 2 per mole of product produced. Many processes, such as CTL, require substantial quantities of work to be added. It is shown that this may be done by designing the overall process such that the process itself is effectively a heat engine. Thus heat at high temperature is added in an endothermic, high temperature sub-process (e.g. gasification) and (less) heat is rejected at a lower temperature from an exothermic, low temperature sub-process (e.g. Fischer–Tropsch synthesis). Just as in a heat engine, there is a relationship between the values of the high and low temperatures, the quantities of heat flowing in and out of the sub processes and the amount of work added to the overall process. One can note that any stream has an enthalpy and a temperature and these two together can be used to describe the work content of this stream. The Carnot temperature for each sub-process is defined as the temperature at which the heat added to the sub-process takes with it the work content required by the sub-process. The bigger the difference between the actual operating temperature and the Carnot temperature, the more irreversible the process is and the further away the process operates from the process target. A CTL process has been chosen to apply the methods in order to obtain the process target and the overall material balances for different options. It is shown that there are different ways of arranging the heat engine for CTL, for example indirect or direct liquefaction, and that the direct route has higher carbon efficiency than the indirect route. However it is shown that one can use the ideas in the paper to synthesise a new route for CTL where rather than gasifying to syngas, one gasifies to hydrogen and carbon dioxide followed by the FT synthesis reaction. In this way one can show that this indirect CTL route is nearly as efficient as the direct route. [ABSTRACT FROM AUTHOR]

The goal of this paper is to show how chemical process synthesis and analysis studies can be coupled with experimental heterogeneous catalysis studies to identify promising research directions for the development of strategies for the production of renewable fuels. We study five catalytic biomass-to-fuels strategies that rely on production of platform chemicals, such as levulinic acid and fermentable sugars. We first integrate catalytic conversion subsystems with separation subsystems to generate complete conversion strategies, and we then develop the corresponding process simulation models based on experimental results. Our analyses suggest that catalytic biomass-to-fuel conversion strategies could become economically competitive alternatives to current biofuel production approaches as a result of iterative experimental and computational efforts. [ABSTRACT FROM AUTHOR]

This paper gives the author's perspective on some of the open questions and opportunities in process synthesis focusing on separation systems as the application. Driven by energy and environmental concerns and challenged by introduction of new raw materials, this author anticipates significant advances in: (1) novel approaches that integrate experimental studies and process synthesis activities, and multi-scale and surrogate models for accurately capturing the behavior of these unconventional mixtures, (2) systematic generation of alternatives for processing these mixtures, and (3) global, robust, and stochastic optimization for identifying the optimum alternative. This paper is an extended version of a conference paper ( Cremaschi, 2014 ) presented at the 8th International Conference on Foundations of Computer-Aided Process Design. [ABSTRACT FROM AUTHOR]

Chemical industry is facing global challenges such as the need to find sustainable production processes. Process intensification as part of process synthesis has the potential to find truly innovative and more sustainable solutions. In this paper, a computer-aided, multi-level, multi-scale framework for synthesis, design and intensification of processes, for identifying more sustainable alternatives is presented. Within the framework, a three stage work-flow has been implemented where, in the first “synthesis” stage an optimal processing route is synthesized through a network superstructure optimization approach and related synthesis tools. In the second, “design” stage, the processing route from the first stage is further developed and a base case design is established and analyzed. In the third, “innovation” stage, more sustainable innovative solutions are determined. The application of the framework is illustrated through a case study related to the production of di-methyl carbonate, which is an important bulk chemical due to its multiplicity of uses. [ABSTRACT FROM AUTHOR]

In this paper, we establish a connection between process integration and process intensification. Focusing on processes with material recycle, we use an asymptotic analysis to demonstrate that intensification represents a limit case of tight integration through significant material recycling. Based on this result, we propose a novel avenue for discovering intensification opportunities at the process design stage. Subsequently, we investigate the dynamics and control implications of the transition from process integration to process intensification. We demonstrate that, for the same steady-state performance, the dynamic response of an integrated process is slower than that of its intensified equivalent. Also, we provide a theoretical justification for existing empirical arguments concerning the loss of control degrees of freedom caused by process intensification. The theoretical developments are applied on a reaction–separation–recycle process example. [ABSTRACT FROM AUTHOR]

This paper describes the development and application of a process-group contribution method to model, simulate and synthesize chemical processes. Process flowsheets are generated in the same way as atoms or groups of atoms are combined to form molecules in computer aided molecular design (CAMD) techniques. The fundamental pillars of this framework are the definition and use of functional process-groups (building blocks) representing a wide range of process operations, flowsheet connectivity rules to join the process-groups to generate all the feasible flowsheet alternatives and flowsheet property models like energy consumption, atom efficiency, environmental impact to evaluate the performance of the generated alternatives. In this way, a list of feasible flowsheets are quickly generated, screened and selected for further analysis. Since the flowsheet is synthesized and the operations in the flowsheet designed through predictive models to match a set of design targets, optimal solution of a given synthesis problem is guaranteed. [ABSTRACT FROM AUTHOR]

The environmental, economic, and technical viability of high and low pressure gasification technologies for the production of ammonia from low rank coal was examined. Three cases were developed starting with different gasification technologies (UGI and BGL), leading to different flowsheets, mass and energy balances, and finally heat integration. Environmental and economic analyses were performed on each of the cases. Three further cases were considered for the treatment of CO 2 generated in the process: direct emission, use in urea production, and carbon capture and storage. CO 2 emissions for the base cases were found to be 2.36–3.15 kg CO 2 -e/kg NH 3 , with a low pressure, UGI gasifier based process giving the lowest emissions. All values obtained are higher than the range of 1.25–1.80 kg CO 2 -e/kg NH 3 for natural gas based ammonia plants in Australia. In comparison with 2013 ammonia prices, the cases were found to be similarly economically unviable. At a discount rate of 15%, the break-even prices achieved are in the order of 2.5 times the current prices, at A$1500/t–A$1600/t in most cases. While no overall benefit for a particular case was clear economically or technically, the use of certain technologies gave notable results. The low-pressure UGI gasifiers, after accounting for compression costs, gave an economic benefit over the high-pressure BGL gasifiers. The liquid nitrogen wash unit, when placed before the ammonia synthesis loop, recovered methane that is suitable for power generation. [ABSTRACT FROM AUTHOR]

In the design of distributed wastewater treatment systems with multiple contaminants, it is very important to minimize unnecessary stream mixing to reduce total treatment flow rate as much as possible. A new numerical indicator, total mixing influence potential (TMIP), to reflect the influence of the stream mixing caused by performing a process on the total treatment flow rate of a distributed wastewater system is introduced. In design procedure, the TMIP value is calculated based on pinch principle. The process with the smallest TMIP value will be performed first. The results of a few literature examples show that designs with very low (even minimum) total treatment flow rates can be obtained with the method proposed. In addition, the method proposed is simple and of clear engineering insight. The calculation effort does not increase significantly when the number of streams, contaminants, and/or treatment units increases. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3223-3231, 2015 [ABSTRACT FROM AUTHOR]

The synthesis and design of reactive distillation columns with two reactive sections (RDC-TRS) are attempted for the separations of reacting mixtures with somewhat unfavorable ranking of relative volatilities (RM-SURRV, i.e., two reactants are the light and heaviest components and two products the lightest and heavy ones). With the deliberate arrangement of the two reactive sections, the disadvantages by the unfavorable relative volatility can be substantially alleviated, facilitating consequently the reaction operation and separation operation involved. The separations of a hypothetical quaternary reaction, the esterification of acetic acid with methanol, and the transesterification of butyl acetate with ethanol are employed to evaluate the RDC-TRS. The process is found considerably superior to the reactive distillation column with a single reactive section and this demonstrates its feasibility and effectiveness in the separations of RM-SURRV. The RDC-TRS is found to present comparable or even improved performance in comparison with the reactive distillation column with an external recycle from bottom to reactive section and this corroborates it a potentially competitive alternative for the separations of the RM-SURRV. The RDC-TRS is also highlighted for the other kind of RM-SURRV (i.e., two reactants are the lightest and heavy components and two products the light and heaviest ones). [ABSTRACT FROM AUTHOR]

Refrigeration system holds an important role in chemical/petrochemical processes. The traditional cascade refrigeration system (CRS) used in ethylene plants contains multiple refrigerants working at multiple temperature/pressure levels. In this study, a general methodology is developed for the optimal process synthesis of a CRS based on exergy analysis. This procedure involves four stages: (1) refrigeration system exergetic analysis; (2) optimization model development for simultaneous synthesis of refrigeration system and heat exchanger network (HEN); (3) HEN configuration; and (4) final solution validation. The exergy-temperature chart is used to comprehensively analyze a CRS. A mathematical model is presented to minimize total compressor shaft work of the HEN-considered CRS, where multiple recycling loops satisfying all cooling/heating demands are simultaneously addressed. The optimal solution is examined by rigorous simulations to verify its feasibility and consistency. The efficacy of the developed methodology is demonstrated by a case study of a propylene CRS in an ethylene plant. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2471-2488, 2015 [ABSTRACT FROM AUTHOR]

In this study, several strategies to upgrade lignocellulosic biorefineries for production of value-added chemicals are systematically generated and evaluated with respect to economic and sustainability objectives. A superstructure-based process synthesis approach under uncertainty integrated with a sustainability assessment method is used as evaluation tool. First, an existing superstructure representing the lignocellulosic biorefinery design network is extended to include the options for catalytic conversion of bioethanol to value-added derivatives. Second, the optimization problem for process upgrade is formulated and solved for two different objective functions: i ) maximization of operating profit (the techno-economic criterion); and ii ) minimization of the sustainability single index ratio (the sustainability criterion). These results indicate first that there is a significant potential of improvement of operating profit for biorefineries producing bioethanol-derived chemicals (247 MM$/a and 241 MM$/a for diethyl ether and 1,3-butadiene, respectively). Second, the optimal designs for upgrading bioethanol (i.e. production of 1,3-butadiene and diethyl ether) performed also better with respect to sustainability compared with the petroleum-based processes. In both cases, the effects of the market price uncertainties were also analyzed by performing quantitative economic risk analysis and presented a significant risk of investment for a lignocellulosic biorefinery (12 MM$/a and 92 MM$/a for diethyl ether and 1,3-butadiene, respectively). The multi-product biorefinery presented a more robust and risk-aware upgrading strategy considering the uncertainties that are typical for a long-term investment horizon. [ABSTRACT FROM AUTHOR]

This paper investigates the production of liquid transportation fuels from municipal solid waste (MSW). A comprehensive process synthesis superstructure is utilized that incorporates a novel mathematical model for MSW gasification. The production of liquid products proceeds through a synthesis gas intermediate that can be converted into Fischer–Tropsch hydrocarbons or methanol. The methanol can be converted into either gasoline or olefins, and the olefins may subsequently be converted into gasoline and distillate. Simultaneous heat, power, and water integration is included within the process synthesis framework to minimize utilities costs. A rigorous deterministic global optimization branch-and-bound strategy is utilized to minimize the overall cost of the waste-to-liquids (WTL) refinery and determine the optimal process topology. Several case studies are presented to illustrate the process synthesis framework and the nonconvex mixed-integer nonlinear optimization model presented in this paper. This is the first study that explores the possibility of liquid fuels production from municipal solid waste utilizing a process synthesis approach within a global optimization framework. The results suggest that the production of liquid fuels from MSW is competitive with petroleum-based processes. The effect that the delivered cost of municipal solid waste has on the overall cost of liquids production is also investigated parametrically. [ABSTRACT FROM AUTHOR]

The possible structural changes of a non-sharp quaternary distillation configuration are considered. For the reference configuration composed of four columns, different alternatives are generated following the process intensification principle to reduce the number of equipment units. The intensified systems with three or two columns are obtained, including the dividing wall columns. Simulator Aspen Plus V8.0 was used to design and simulate all the systems for a hydrocarbon mixture. The intensified structures showed relevant energy savings compared to the reference case. The most promising alternatives were optimized by means of the differential evolution (DE) method minimizing the total annual cost (TAC). It was observed that the intensified systems were able to reduce both the energy consumption and the number of equipment units. The best intensified system has a TAC of 11.98% lower than the optimized reference case. [ABSTRACT FROM AUTHOR]

An algorithm-based method for synthesis of hydrometallurgical processes using limited amounts of experimental data is presented. The method enables simultaneous selection and sequencing of unit operations and optimization of operating parameters. An ant colony optimization (ACO) based algorithm is used to identify the most economic process alternative in an iterative manner. Key performance indicators are used for comparison of candidate processes: a purification performance index measures purity improvement and a separation cost indicator is used as an objective function in process optimization. Computational times were reduced significantly with the suggested method compared to an algorithm which evaluates all the possible process options. The practical applicability of the method to hydrometallurgy is demonstrated by investigating zinc recovery from argon oxygen decarburization dust with two alternative leaching methods and recovery of lanthanides from nickel metal hydride (NiMH) batteries. In the first zinc recovery process, 150 min normal batch leaching with 0.5 M H 2 SO 4 is used, and in the other one 270 min batch leaching with H 2 SO 4 is done by controlling the pH (> 3.0). In both cases the leachate is extracted with D2EHPA at pH 4.27, and stripped with circulating solution from zinc electrolysis. For lanthanides recovery the algorithm suggested a process in which the raw material is leached with 1.3 M HCl, the leachate is extracted with D2EHPA at pH 2.2, organic phase is stripped with 2.0 M HCl and 99% pure Ln-oxalates are precipitated with oxalic acid at pH 0.6. Compared to previously suggested process for the same raw material, the algorithm suggests operating the leaching step such that higher selectivity is achieved by sacrificing some yield. [ABSTRACT FROM AUTHOR]

The coproduction of liquid transportation fuels and C6C8 aromatics from the thermochemical conversion of biomass and natural gas (BGTL+C6_C8) is investigated in this article. An optimization-based process synthesis framework incorporating multiple synthesis gas conversion technologies, such as Fischer-Tropsch synthesis or methanol conversion, is described. Production of aromatics can proceed through several technologies, such as naphtha reforming and aromatization of hydrocarbons via a metal-promoted H-ZSM-5 catalyst. This is the first article in the literature to incorporate an aromatics complex for the coproduction of liquid fuels and C6C8 petrochemicals within a rigorous process synthesis and deterministic global optimization framework. The optimal process topologies across several case studies are discussed and the results indicate that the coproduction of aromatics with liquid fuels can significantly increase the profitability of these refineries. © 2015 American Institute of Chemical Engineers AIChE J, 2015 2014 American Institute of Chemical Engineers AIChE J, 61: 831-856, 2015 [ABSTRACT FROM AUTHOR]

Thermal membrane distillation (TMD) is an emerging separation method which involves simultaneous heat and mass transfer through a hydrophobic semipermeable membrane. Traditionally, studies of this technology have focused on the performance of individual modules. Because of purity and recovery requirements, multiple TMD modules may be used in various configurations including series, parallel, and combinations. Furthermore, there may be a need to reroute streams from one module to another or to recycle a stream to the same unit. The objective is to develop a systematic approach to synthesize an optimal TMD network. A structural representation is developed to embed potential configurations of interest. A mathematical formulation is developed to transform the design problem into an optimization task that seeks to minimize the cost of the system. Two case studies are presented to illustrate the applicability of the developed approach and its merit over conventional design scenarios. © 2014 American Institute of Chemical Engineers AIChE J, 61: 448-463, 2015 [ABSTRACT FROM AUTHOR]

Zero wastewater discharge (ZWD) networks are targeted and designed in this work by an analytical approach not requiring graphical constructions. The approach is based on three fundamental equations that entail the following requirements for ZWD: (1) the system water loss is entirely made up by freshwater; (2) the net system contaminant load equals the regeneration load; and (3) the net below-pinch contaminant load is picked up by the minimum regenerated water and freshwater. The Unified Targeting Algorithm (UTA) is used to determine the minimum regeneration flowrate and identify the pinch concentration. Necessary conditions are established for pinch jumps and for ZWD feasibility in terms of the maximum post-regeneration outlet concentration. Importantly, continuous targeting is possible over the entire feasible ZWD range through two elegant formulas, wherein (1) the regeneration flowrate is inversely proportional to the concentration reduction during regeneration and (2) the pre-regeneration concentration decreases linearly with post-regeneration concentration provided the pinch is held by the same point. The Enhanced Nearest Neighbors Algorithm (NNA) is utilized to systematically synthesize ZWD networks over the entire ZWD range and ascertain the network topology valid within sub-ranges. Case studies, including one for a paper mill and another for an alumina plant, are presented to illustrate the versatility of the approach in generating superior practical designs for ZWD networks involving fixed contaminant-load and fixed flowrate processes with and without water loss. [ABSTRACT FROM AUTHOR]

It was shown in an earlier work by us that entropy generation and energy (hot utility or cold utility) consumption of isothermal, isobaric reactor networks depend only on the network's inlet and outlet stream compositions and flow rates and are not dependent on the reactor network structure, as long as the universe of realizable reactor units and network outlet mixing units are either all endothermic interacting with a single hot reservoir, or all exothermic interacting with a single cold reservoir, respectively. It is shown that when the universe of realizable reactor/mixer units, of isothermal, isobaric, continuous stirred tank reactor networks, consists of both endothermic units interacting with a single hot reservoir and exothermic units interacting with a single cold reservoir, the network's net (hot minus cold) utility consumption depends only on the network's inlet and outlet stream compositions and flow rates (and does not depend on the network's structure). In contrast, the network's entropy generation depends on the network's inlet and outlet stream compositions and flow rates, and the network's hot utility (or cold utility) consumption. The latter, in general, depends on the network structure, thus making entropy generation also, in general, depend on network structure. Thus, the synthesis of isothermal, isobaric reactor networks, with fixed inlet and outlet stream specifications, is equivalent to the synthesis of minimum hot (or cold) utility consuming such networks. The Infinite DimEnsionAl State-space conceptual framework is used for the problem's mathematical formulation, which is then used to rigorously establish the above equivalence. A case study involving Trambouze kinetics demonstrates the findings. © 2014 American Institute of Chemical Engineers AIChE J, 61: 103-117, 2015 [ABSTRACT FROM AUTHOR]

This work presents a comprehensive classification of the different methods and procedures for integrated synthesis, design and control of chemical processes, based on a wide revision of recent literature. This classification fundamentally differentiates between “projecting methods”, where controllability is monitored during the process design to predict the trade-offs between design and control, and the “integrated-optimization methods” which solve the process design and the control-systems design at once within an optimization framework. The latter are revised categorizing them according to the methods to evaluate controllability and other related properties, the scope of the design problem, the treatment of uncertainties and perturbations, and finally, the type the optimization problem formulation and the methods for its resolution. [ABSTRACT FROM AUTHOR]

In this paper, several methodologies of integrated design are proposed and applied to the design of wastewater treatment plants and their control system, focusing on the activated sludge process, within a novel multiobjective framework. The scope of the problem considers both fixed plant layout and plant structure selection by defining a simple superstructure. The control strategy chosen is a linear Model Predictive Controller (MPC) with terminal penalty. The evaluation of the controllability has been performed using norm based indexes, and the robustness conditions for different uncertainty sources have been considered, in the frequency and time domains. The optimization strategies used are based on the integration of stochastic and deterministic methods, as well as genetic algorithms. The presented methodologies and their application to wastewater treatment plants can be considered as an illustrative example in the universe of integrated design techniques presented in the Part I article of this series. [ABSTRACT FROM AUTHOR]

In this paper a multi-level, multi-scale framework for process synthesis-intensification that aims to make the process more sustainable than a base-case, which may represent a new process or an existing process, is presented. At the first level (operation-scale) a conceptual base case design is synthesized through the sequencing of unit operations and subsequently analyzed for identifying process hot-spots using economic, life cycle and sustainability metrics. These hot-spots are limitations/bottlenecks associated with tasks that may be targeted for overall process improvement. At the second level (task-scale) a task-based synthesis method is applied where one or more tasks representing unit operations are identified and analyzed in terms of means-ends for generating intensified flowsheet alternatives. At the third level (phenomena-scale) a phenomena-based synthesis method is applied, where the involved phenomena in various tasks are identified, manipulated and recombined to generate new and/or existing unit operations configured into flowsheet alternatives that target the tasks associated with hot-spots. Every lower-scale or higher-level, generates more alternatives than their corresponding larger-scale. Those alternatives that are able to address the identified hot-spots therefore give innovative and more sustainable process designs that otherwise could not be found from the larger-scales. In this paper, membrane-based operations identified through this framework are highlighted in terms of extension of the combined intensification-synthesis method and its application to generate membrane-based operations. Also, application of the framework is illustrated through a case study involving the production of methyl acetate where membrane-based intensified operations play a major role in determining more sustainable process design alternatives. [ABSTRACT FROM AUTHOR]

The sequential design method (SDM) is a recently introduced distillation column design method based on the correspondence between the simple column and the alternative sequences design parameters. It can be defined as a method that combines the alternatives generation step with the design procedure. The Multi-Objective Differential Evolution (MODE) algorithm instead, is based on the minimization or maximization of a defined objective function; it is a strong method that allows the evaluation of a large number of alternatives. The SDM is characterized by a poor control of the error propagation among the sequences, the MODE algorithm by a high computational time. It was obtained that a proper combination of the methods allows the compensation of the drawbacks of the stand-alone procedures. For the case study considered, when the MODE algorithm is initialized with the SDM, a 39% reduction of the computational time was observed. If the combination between the methods is realised at the beginning of the design procedure, the reduction of the computational time was of about 28%. The time reduction was due to a narrower initialization of the MODE algorithm with the parameters obtained applying the SDM. Moreover, when some overestimated design values where used to initialize the MODE algorithm, it is still possible to identify a configuration very close to the optimum. [ABSTRACT FROM AUTHOR]