Synthesis of regional networks for biomass and biofuel production Hon Loong Lam
, 2010, dissertation
Abstract: This thesis presents two different approaches to the synthesis of regional networks for biomass and biofuel production and supply: Mathematical Programming and Graph Theoretic approach. The optimisation criterion for both approaches is the maximisation of profit.
The first approach is based on a generic optimisation model of biomass production and supply networks. This superstructure approach is based on a flexible number of network layers: plantation, collection using a pre-treatment, process, and consumption. A Mixed Integer Linear Programming (MILP) model has been successfully developed during this work.
However, the solution of this biomass production network model is very challenging due to the large sizes of the networks and the number of interconnections. The huge number of redundant variables reduces model efficiency (time taken to solve the model and the interpretation of the results). This model when representing very large size networks cannot be solved over a reasonable time even by professional mathematical programming software tools. Several model-size reduction techniques are therefore proposed for the solution of large-scale networks. In particular, methods are proposed for (i) reducing the connectivity within a biomass supply chain network by setting the maximum allowable distance between the supply zones to the collection centres, (ii) eliminating unnecessary variables and constrains to reduce the zero-flows in the full model, and (iii) aggregating the network and hence the synthesis process by merging the collection centres.
The network synthesis is also carried out by P-graph (Process Graph) tools. P-graph is a directed bipartite graph, having two types of vertices — one for operating units and another for those objects representing material or energy flows/quantities. In this procedure, firstly a maximum feasible superstructure for biomass production network is generated from which the optimal structure is then selected by the Branch and Bound method. This graph-based method clearly shows where, how, and what kind of material and energy carriers will be transferred from one supply chain layer to another.
In order to test the efficiency of the model, a small regional renewable network problem was solved using both methods. Their performances were tested and the results confirmed the applicability on a regional scale. The proposed model-size reduction techniques were also tested. A large-scale regional case study was created to demonstrate these techniques. The results are very positive and some suggestions for future work are given in the conclusion.
Keywords: Biomass and bioenergy network synthesis, Model-size reduction
techniques, Mathematical Programming, MILP, P-Graph
Published: 06.01.2011; Views: 2531; Downloads: 85
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The role of computer-aided chemical engineering education within the european Bologna three- cycle study systemZdravko Kravanja
, Jiri Klemeš
, 2011, published scientific conference contribution
Abstract: Universities around Europe are currently adopting the new Bologna three-cycle study system and most of Chemical Engineering departments have already developed new study programs accordingly. In this respect, two main questions have been posed in order to reorganize current chemical engineering study programs: i) which skills and knowledge, common to all chemical engineers, should not be ignored whilst developing new chemical engineer curricula, and ii) which are the other chemical engineering topics, engineering fields, and nonengineering knowledge necessary for engineers to manage those problems of specific current and future (bio)chemical and process related industries. One of the aims of this presentation is to discuss basic learning outcomes, and recommended topics common to all chemical engineers, especially relating to those process systems engineering aspects to be embedded within new study programs requiring the use of computer-aided methods and tools during chemicalengineering education. The uses for these methods and tools will be discussed shortly, among them the development of new computer-aided methods and tools, multimedia internet-based teaching and learning programs, and cyberinfrastrucure-based virtual libraries.
Keywords: Bologna study system, computer-aided education, chemical engineering core curriculum, program outcomes, computer-aided methods and tools
Published: 01.06.2012; Views: 1298; Downloads: 54
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Software tools overview : process integration, modelling and optimisation for energy saving and pollution reductionHon Loong Lam
, Jiri Klemeš
, Zdravko Kravanja
, Petar Varbanov
, 2011, original scientific article
Abstract: This paper provides an overview of software tools based on long experience andapplications in the area of process integration, modelling and optimisation. The first part reviews the current design practice and the development of supporting software tools. Those are categorised as: (1) process integration and retrofit analysis tools, (2) general mathematical modelling suites with optimisation libraries, (3) flowsheeting simulation and (4) graph-based process optimisation tools. The second part covers an assessment of tools which enable the generation of new sustainable alternatives to adapt to the future needs. They deal with waste, environment, energy consumption, resources depletion and production cost constrains. The emphasis of the sustainable process design tools is largely on the evaluation of process viability under sustainable economic conditions, synthesis of sustainable process and supply chain process maintenance and life cycle analysis. Major software tools development and the potential of the research-based tools for sustainable process design task are overviewed in theconcluding part.
Keywords: software tools, process integration, process modelling, process optimisation, energy saving
Published: 01.06.2012; Views: 1192; Downloads: 58
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Targeting energy generation and carbon footprint for waste management and processingPetar Varbanov
, Lidija Čuček
, Jiri Klemeš
, Zdravko Kravanja
, 2012, published scientific conference contribution
Abstract: Waste to Energy (WTE) processing carries a trade-off between energy extractionfrom the waste and the energy for waste management - collection, transport and treatment. Major performance indicators are the Primary Energy Savings (PES), Carbon Footprint (CFP) and especially the cost. This presentation analyses the significance of the factors in this trade-off introducing a new indicator - the Waste Energy Potential Utilisation (WPU). The results indicate that the impact of the logistics and energy distribution can be significant, and distributed WTE architectures can be good candidates for waste processing, subject to further economical and environmental conditions.
Keywords: waste-to-energy, waste energy potential utilisation, optimisation processing distribution
Published: 10.07.2015; Views: 374; Downloads: 21
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SYNTHESIS OF SUSTAINABLE BIOPROCESSES USING COMPUTER-AIDED PROCESS ENGINEERINGLidija Čuček
, 2013, doctoral dissertation
Abstract: This doctoral dissertation, which consists of four substantive wholes, presents several syntheses of sustainable bioprocesses using computer-aided process engineering. In the first part the synthesis of different integrated processes of ethanol production from the entire corn plant is presented. The synthesis of different processes is in the second part further extended to the simplified and more comprehensive synthesis of bioproducts in the whole production supply chain network. Synthesis is based on the generic optimisation model of biomass production and supply chain networks.
In the third part three methods for sustainable development assessment, suitable for multi-criteria optimisation, are presented: method of sustainability indexes, footprints and combined criteria, such as eco- and total profit. Methods are further upgraded with indirect effects in order to measure the unburdening the environment, associated with the use and replacement of environmentally-harmful products. Methods include the direct, indirect and total impacts on the environment.
In the last part the methodology for reducing a large number of criteria within multi-objective optimisation to a small number of representative criteria is presented. This method is presented on the case of environmental footprints.
Keywords: Biomass energy generation, Supply chain networks, Synthesis of sustainable bioprocesses, Life Cycle Analysis, Sustainability assessment, Multi-objective optimisation, Dimensionality reduction, Representative Objectives Method
Published: 06.05.2013; Views: 1463; Downloads: 189
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SYNTHESIS OF PROCESSES AND PROCESS SUBSYSTEMS FOR ENTIRE LIFETIMEAndreja Nemet
, 2015, doctoral dissertation
Abstract: Economically viable process designs should be, in addition to other criteria, profitable over their entire process lifetimes not only at the present time. An improved process design can be achieved by establishing an appropriate trade-off between product income, raw material, operating costs, and investment. The full lifetime of the processes and future prices have to be considered rather than optimising them on a yearly basis using current prices. Single-period optimisation and synthesis models for processes reflects current prices only. The prices can fluctuate rather quickly and the optimal solution may be very different from one year to the another. Therefore, the traditional superstructural synthesis approach applying a mixed-integer nonlinear programming model was upgraded: i) over time, by considering an entire lifetime, which can be described by a multi-period model and ii) the whole field of variation regarding uncertain future prices. A stochastic approach considering the statistical distribution of price projections over an entire lifetime was used on different case studies instead of the traditional deterministic approach accounting for nominal future price projection. The objective was the maximisation of the expected net present value of a process or the expected incremental net present value of different process subsystem.
The heat exchanger network has been one of the subsystem, which can significantly contribute to operating costs due to savings of external utility consumption. For this subsystem a deterministic and stochastic multi-period mixed-integer nonlinear programming (MINLP) synthesis models have been developed in order to account for future price projections. Considering higher energy prices gives rise to larger initial investments compared to solutions obtained with current prices. However, due to the uncertainties of utility prices' forecasts, retrofitting using an extension of HEN during future years of the lifespan might be a better strategy. The objective is to identify a design that is the most suitable for effective future extensions and preferably with the lowest sensitivity to energy price fluctuations, as there can be various designs featuring similar initial investment. The results supports that it is economically beneficial to consider future utility prices as the incremental investment is not only paid-off but additional savings are achieved.
Process-to-process Heat Integration can also significantly affect the trade-off between investment and operating cost. The aim of Total Site (TS) HEN synthesis was to develop a model synthesis for the TS that, besides many other important features, would also consider future utility prices. Two strategies for TS synthesis have been developed: i) sequential, when HI is performed within a process during the first step and then after a process-to-process HI has been performed, and ii) simultaneous, where the HI is performed within and between processes simultaneously. The second strategy can reveal additional opportunities for heat recovery that might not be identified when applying the first strategy. Comparison of the results obtained at consideration of current utility prices and forecasted utility prices indicates that is worth to account for future utility prices.
The separation processes also consume a significant amount of energy. The synthesis of a distillation column sequence integrated within its heat exchanger network was used as a case study for the separation of a multi-component stream into pure component products by considering future utility prices. This analysis has been performed in order to evaluate the magnitude of the influence of forecasted utility prices. It can be concluded that forecasted utility prices can be beneficial, however, the technical limits of the systems should be carefully observed.
The price fluctuation can also be observed for other prices not only utility prices, e.g. raw material cost, product price, etc
Keywords: future prices, forecasted prices, stochastic optimisation, mathematical programming, Heat Exchanger Network, Total Site, distillation column sequence, methanol production
Published: 04.05.2015; Views: 847; Downloads: 78
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