A systematic approach to the synthesis and design of flexible site utility systems

The paper presents a systematic approach for the synthesis of flexible utility systems satisfying varying energy demands. The approach combines benefits of total site analysis, thermodynamic analysis and mathematical optimisation. A thermodynamic efficiency curve (TEC) is developed, which gives an overview of the maximum thermodynamic efficiencies of all possible design alternatives. TEC and hardware composites guide the selection of candidate structures in the superstructure, excluding uneconomic options from the synthesis model. The integration of thermodynamics yields significant reduction in the synthesis model, addresses the impact of variable loads on the unit efficiencies, and enables a compact formulation of the design problem over long horizons of operation. The optimisation is formulated as a multi-period MILP problem that relies on new target models to describe the performance of steam turbines, condensing turbines, gas turbines and boilers. Target models account for the variation of efficiency with unit size, load and operating conditions in a simple, yet accurate way. As a result, these models are capable of accounting for the efficiency trends of realistic units.     

A generalized method for the synthesis and design of reactive distillation columns

Owing to the combination between the reaction operation and the separation operation involved, it is extremely difficult to determine in advance the optimum configuration of a reactive distillation column and this makes process synthesis and design a great challenging task. Currently, no easy-to-use and yet effective methods are available to guide process synthesis and design, restricting considerably the applications and therefore the impacts of reactive distillation columns to the chemical process industry. In this paper, a generalized method is proposed for the synthesis and design of reactive distillation columns in terms of the insights from process intensification. The method is initiated from a simple process design with all feeds of reactants at the middle of the process and all stages as reactive ones. In terms of an economical objective function, it can be evolved into the optimum process design via sequential structure adjustments, including reactive section arrangement, feed stage relocation, feed splitting, and catalyst redistribution. The generalized method proposed is characterized by great simplicity in principle, the capability to tap the full potentials of process intensification, and the high robustness to the initial guess of process configuration as well as the thermodynamic properties of the reacting mixtures separated. Four example systems are employed to evaluate the generalized method proposed and the obtained outcomes demonstrate its effectiveness and applicability to the synthesis and design of various reactive distillation columns.     

Towards a methodology for the systematic analysis and design of efficient chemical processes: Part 1. From unit operations to elementary process functions

A successful intensification of a chemical process requires a holistic view of the process and a systematic debottlenecking, which is obtained by identifying and eliminating the main transport resistances that limit the overall process performance and thus can be considered as rate determining steps on the process level. In this paper, we will suggest a new approach that is not based on the classical unit operation concept, but on the analysis of the basic functional principles that are encountered in chemical processes.A review on the history of chemical engineering in general and more specifically on the development of the unit operation concept underlines the outstanding significance of this concept in chemical and process engineering. The unit operation concept is strongly linked with the idea of thinking in terms of apparatuses, using technology off the shelf. The use of such “ready solutions” is of course convenient in the analysis and design of chemical processes; however, it can also be a problem since it inherently reduces the possibilities of process intensification measures.Therefore, we break with the tradition of thinking in terms of “unit apparatuses” and suggest a new, more rigorous function-based approach that focuses on the underlying fundamental physical and chemical processes and fluxes.For this purpose, we decompose the chemical process into so-called functional modules that fulfill specific tasks in the course of the process. The functional modules itself can be further decomposed and represented by a linear combination of elementary process functions. These are basis vectors in thermodynamic state space. Within this theoretical framework we can individually examine possible process routes and identify resistances in individual process steps. This allows us to analyze and propose possible options for the intensification of the considered chemical process.     

Life Cycle Assessment (LCA) of the biofuel production process from sunflower oil, rapeseed oil and soybean oil

Once ratified the Kyoto protocol, Spain arises the great challenge of reducing the emissions of greenhouse gases. Among the measures proposed is the introduction of biofuels in the market, both for the transport sector and for the production of heat. This paper compares the environmental impact from the production of biofuels whose origin is the oil obtained from sunflower, rapeseed and soybeans. The environmental impact of each production is performed by applying the methodology of life cycle analysis (LCA). The categories where you get a greater impact are land use, fossil fuels, carcinogens, inorganic respiratory and climate change. The cause is mainly due to the processes of seed production. We have also found a significant impact on the drying and preparation processes of the seed as well as the crude soybean oil extracting process. Moreover as the LCA shows production of rapeseed and sunflower has a positive contribution to climate change.     

Systematic retrofit design with Response Surface Method and process integration techniques: A case study for the retrofit of a hydrocarbon fractionation plant

This paper demonstrates the Retrofit Design Approach (RDA) and Response Surface Methodology (RSM) for the retrofit of industrial plants in which assessment of design options for improving existing processes in a site-wide and integrated manner is not straightforward, due to complex design interactions in the process. The design methodology applied in this study is based on the systematic use of a process simulator which is used to identify promising variables through sensitivity analysis. Hence, the most important factors are determined and a reduced model is constructed based on RSM. An optimization framework is then built using the reduced model based on key selected variables, which is optimized to find optimal conditions and performance of the process. This design methodology provides strategic guidelines for determining the most cost-effective design options. The retrofit of a hydrocarbon fractionation plant is presented as an industrial case study. This includes a large number of design options with different process configurations and operating conditions due to the interconnection of distillation columns in sequence and the integrated heat recovery within the plant. The case study results demonstrate the applicability of the proposed approach which is able to effectively deal with a large retrofit problems. This is possible with the aid of process simulation and RSM producing a reduced model which requires considerably less computational effort to solve.     

A combined heuristic and indicator-based methodology for design of sustainable chemical process plants

The current emphasis on sustainable production has prompted chemical plants to minimize raw material and energy usage without compromising on economics. While computer tools are available to assist in sustainability assessment, their applications are constrained to a specific domain of the design synthesis problem. This paper outlines a design synthesis strategy that integrates two computer methodologies - ENVOPExpert and SustainPro - for simultaneous generation, analysis, evaluation, and optimization of sustainable process alternatives. ENVOPExpert diagnoses waste sources, identifies alternatives, and highlights trade-offs between environmental and economic objectives. This is complemented by SustainPro which evaluates the alternatives and screens them in-depth through indicators for profit and energy, water, and raw material usage. This results in accurate identification of the root causes, comprehensive generation of design alternatives, and effective reduction of the optimization search space. The framework is illustrated using an acetone process and a methanol and dimethyl ether production case study.     

A superstructure-based framework for simultaneous process synthesis,heat integration,and utility plant design

We propose a superstructure optimization framework for process synthesis with simultaneous heat integration and utility plant design. Processing units in the chemical plant can be modeled using rigorous unit models or surrogate models generated from experimental results or off-line calculations. The utility plant subsystem includes multiple steam types with variable temperature and pressure. For the heat integration subsystem, we consider variable heat loads of process streams as well as variable intervals for the utilities. To enhance the solution of the resulting mixed-integer nonlinear programming models, we develop (1) new methods for the calculation of steam properties, (2) algorithms for variable bound calculation, and (3) systematic methods for the generation of redundant constraints. The applicability of our framework is illustrated through a biofuel case study which includes a novel non-enzymatic hydrolysis technology and new separation technologies, both of which are modeled based on experimental results.     

A general modular framework for the integrated optimal management of an industrial gases supply-chain and its production systems

A general modular methodology for the simultaneous optimization of the supply-chain network and the production systems of a general industrial gas producer is developed and implemented in a C++ program. The formulation and solution algorithm are specifically designed to be able to work on-line and to determine the optimal assignments of production site output to customer demand in the supply-chain and the corresponding optimal operating conditions for the production plants in integrated fashion. Here, the production network is not simply modelled as a set of product sources, rather the model is detailed enough to allow effective and feasible optimization of the entire system. Moreover, the proposed approach can be easily combined with the rolling horizon technique to mitigate the uncertainties in demand. The modelling strategies, employed for the supply-chain network and the production sites, along with the solution approach, adopted for the resulting optimization problem, are detailed. BzzMath library classes are used to meet the computational efficiency requirements for on-line applications. The effectiveness of the proposed methodology is demonstrated on a case study involving a portion of the real supply-chain and network of production facilities of Linde Gas Italia S.r.l.     

A methodology for the sustainable design and implementation strategy of CO2 utilization processes

This work presents a systematic methodology that has been developed for the design of sustainable CO₂ utilization processes that can mitigate CO₂ and also guarantee profitability. First, the three-stage methodology, evaluation criteria and applicable tools are described. Especially, the process design and analysis is discussed as only limited amounts of process data is available for determining the optimal processing path and in the third stage the issue of implementation strategy is considered. As examples, two CO₂ utilization methods for methanol production, combined reforming and direct synthesis are considered. Methanol plants employing such methods are developed using synthesis-design and simulation tools and their evaluation indicators are calculated under various implementation strategies. It is demonstrated that integrating or replacing an existing conventional methanol plant by a combined reforming method represents a sustainable solution. Additionally, producing methanol through direct hydrogenation is a promising way to convert CO₂ when cheap H₂ feeds are available.     

Energy, water and process technologies integration for the simultaneous production of ethanol and food from the entire corn plant

This paper presents simultaneous integration of different technologies such as the traditional dry-grind process to obtain ethanol from grain with the gasification of the corn stover followed by either syngas fermentation or catalytic mixed alcohols synthesis. The optimal integrated process when using the entire corn plant (18 kg/s of grain and 10.8 kg/s of stover) is the one in which the dry-grind technology to process corn grain is integrated with the catalytic path for the corn stover due to the improved integration of energy, requiring only 17 MW of energy, 50 MW of cooling and 1.56 gal/gal of freshwater, for an ethanol production cost of 1.22 $/gal. However, the production cost decreases as we only use stover to produce ethanol, while the grain is used for food due to the lower cost of the stover and the more favorable energy balance of the ethanol production process from gasification.     

An energy systems engineering approach for the design and operation of microgrids in residential applications

A distributed energy system refers to an energy system where energy production is close to end use, typically relying on small-scale energy distributed technologies. It is a multi-input and multi-output energy system with substantial energy, economic and environmental benefits. However, distributed energy systems such as micro-grids in residential applications may not be able to produce the potential benefits due to lack of appropriate system configurations and suitable operation strategies. The optimal design, scheduling and control of such a complex system are of great importance towards their successful practical realization in real application studies. This paper presents a short review and an energy systems engineering approach to the modeling and optimization of micro-grids for residential applications, offering a clear vision of the latest research advances in this field. Challenges and prospects of the modeling and optimization of such distributed energy systems are also highlighted in this work.     

On the integration of CO2 capture with coal-fired power plants: A methodology to assess and optimise solvent-based post-combustion capture systems

Amine and other liquid solvent CO₂ capture systems capture have historically been developed in the oil and gas industry with a different emphasis to that expected for fossil fuel power generation with post-combustion capture. These types of units are now being adapted for combustion flue gas scrubbing for which they need to be designed to operate at lower CO₂ removal rates - around 85-90% and to be integrated with CO₂ compression systems. They also need to be operated as part of a complete power plant with the overall objective of turning fuel into low-carbon electricity.The performance optimisation approach for solvents being considered for post-combustion capture in power generation therefore needs to be updated to take into account integration with the power cycle and the compression train. The most appropriate metric for solvent assessment is the overall penalty on electricity output, rather than simply the thermal energy of regeneration of the solvent used.Methodologies to evaluate solvent performance that have been reported in the literature are first reviewed. The results of the model of a steam power cycle integrated with the compression system focusing on key parameters of the post-combustion capture plant - solvent energy of regeneration, solvent regeneration temperature and desorber pressure - are then presented. The model includes a rigorous thermodynamic integration of the heat available in the capture and compression units into the power cycle for a range of different solvents, and shows that the electricity output penalty of steam extraction has a strong dependence on solvent thermal stability and the temperature available for heat recovery. A method is provided for assessing the overall electricity output penalty (EOP), expressed as total kWh of lost output per tonne of CO₂ captured including ancillary power and compression, for likely combinations of these three key post-combustion process parameters. This correlation provides a more representative method for comparing post-combustion capture technology options than the use of single parameters such as solvent heat of regeneration.     

A combined method for the design and optimization of intensified distillation systems

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.     

A methodology for the simultaneous design and control of large-scale systems under process parameter uncertainty

This work presents a simultaneous design and control methodology for large-scale systems. The approach is based on the identification of an uncertain model from a first-principle process model. Using the identified uncertain model, a Structured Singular Value (SSV) analysis is used to estimate the realizations in the disturbance set that generates the worst-case variability and constraint violations. Then, simulations of the first-principle process model are performed with the critical disturbance profile as input to estimate the actual worst-case output variability and the worst-case variations in the process constraints. Since the proposed methodology is formulated as a nonlinear constrained optimization problem, it avoids the computationally expensive task of solving dynamic optimization problems, making it suitable for application to large-scale systems. The proposed methodology was tested on the Tennessee Eastman process to show that a redesign of the major process units in the process could significantly reduce the costs of this plant.     

Process systems engineering: From Solvay to modern bio- and nanotechnology.: A history of development, successes and prospects for the future

The term Process Systems Engineering (PSE) is relatively recent. It was coined about 50 years ago at the outset of the modern era of computer-aided engineering. However, the engineering of processing systems is almost as old as the beginning of the chemical industry, around the first half of the 19th century. Initially, the practice of PSE was qualitative and informal, but as time went on it was formalized in progressively increasing degrees. Today, it is solidly founded on engineering sciences and an array of systems-theoretical methodologies and computer-aided tools. This paper is not a review of the theoretical and methodological contributions by various researchers in the area of PSE. Its primary objective is to provide an overview of the history of PSE, i.e. its origin and evolution; a brief illustration of its tremendous impact in the development of modern chemical industry; its state at the turn of the 21st century; and an outline of the role it can play in addressing the societal problems that we face today such as; securing sustainable production of energy, chemicals and materials for the human wellbeing, alternative energy sources, and improving the quality of life and of our living environment. PSE has expanded significantly beyond its original scope, the continuous and batch chemical processes and their associated process engineering problems. Today, PSE activities encompass the creative design, operation, and control of: biological systems (prokaryotic and eukaryotic cells); complex networks of chemical reactions; free or guided self-assembly processes; micro- and nano-scale processes; and systems that integrate engineered processes with processes driven by humans, legal and regulatory institutions. Through its emphasis on synthesis problems, PSE provides the dialectic complement to the analytical bent of chemical engineering science, thus establishing the healthy tension between synthesis and analysis, the foundation of any thriving discipline. As a consequence, throughout this paper PSE emerges as the foundational underpinning of modern chemical engineering; the one that ensures the discipline's cohesiveness in the years to come.     

A methodology for simultaneous process and product design in the formulated consumer products industry: The case study of the detergent business

In this work we present a mathematical optimization based methodology for simultaneous formulae and process design in the consumer product business applied to the case of the laundry detergent. The design of a new detergent is formulated as a modified pooling problem including process, performance, processability and environmental constraints. This new features add a number of nonlinearities related to the modeling of the different aspects of the process and customer acceptance. The problem becomes a multiobjective optimization problem that is solved using the ?-constraint method with global optimization techniques to minimize of the environmental impact while minimizing the production cost for a couple of case studies. As future work, further process, product and legal constraints can be added to make the problem more realistic.     

A systematic framework for the design,simulation and optimization of personalized healthcare: Making and healing blood

We review the key building blocks of a design framework for modeling and optimizing biomedical systems under development in the Biological Systems Engineering Laboratory and the Centre for Process Systems Engineering at Imperial College. The framework features the following components: (i) in vitro environment, where model parameters can be obtained and new setups can be tested; (ii) in silico environment, including a simulation module for representing relevant physical or biological processes, and an optimization module, for calculating improved in vitro or in vivo outcomes; (iii) in vivo environment, from which organ and patient-specific parameters are collected and which can also implement personalized suggestions for improved outcomes. Two applications in the area of healthy and diseased blood are thoroughly discussed to exemplify the framework's characteristics. We discuss progress in the different areas and the way in which they are connected and finally propose a hybrid in vitro/in silico/in vivo platform.