Peter Glavič

Retrofit of complex and energy intensive processes II: stepwise simultaneous superstructural approach

Simultaneous parameter and structural optimization of an existing complex and energy intensive continuous process have been studied using rigorous models. The method that was recently developed to sequentially optimize retrofits has been extended to a stepwise simultaneous superstructural approach, using available process simulators and optimization software capabilities. An extended procedure has been employed for retrofits using a three-step approach: (i) generation of a process superstructure by pinch analysis; (ii) formulation of a mixed integer nonlinear programming (MINLP) model and its simplification into a relaxed nonlinear programming (NLP) model; (iii) simultaneous optimization, first by a process simulator and than by the NLP algorithm. Pinch analysis offers alternative retrofit designs for postulating the superstructure. An advantage of the relaxed NLP formulation over the MINLP one is that it can be easily generated. Poor local optima due to nonlinear interconnections between alternative solutions have been avoided by applying a direct search complex algorithm using the simulator. The approach has been illustrated by maximizing the annual profit of an existing methanol plant. The optimal solution yields additional savings of 5.17 MUSD per annum (6.75% of the total income) which is 6.5 times the savings obtained by the earlier sequential optimization method.

Technological choices for sustainability

Framing the Issue of Sustainability.- Science and Sustainability: who knows best?.- Sustainability: Ecological, Social, Economic, Technological, and Systems Perspectives.- US EPA/Academia Collaboration for a Green Engineering Textbook For Chemical Engineering.- Innovative Industrial Ecology Education Can Guide Us to Sustainable Paths.- The sustainable industrial development: reality and vision.- Sustainable Pathways.- Clean technologies for wastewater management in seafood canning industries.- Kinetic Analysis of Aerobic Composting of Tobacco Industry Solid Waste.- Preventative Measures in Production from the Point of Sustainability.- Environmetric strategies to classify, interpret and model risk assessment and quality of environmental systems.- Carbon storage: the economic efficiency of storing CO2 in leaky reservoirs.- An Integrated Computer Aided System for Generation and Evaluation of Sustainable Process Alternatives.- Pollution prevention and environmental management systems - tools to obtain a sustainable development.- Sustainability Metrics.- Technology sensitive indicators of sustainability.- Metrics for supply chain sustainability.- Quantifying technological aspects of process sustainability: a thermodynamic approach.- Defining and Measuring Macroeconomic Sustainability - The Sustainable Economy Indices.- Environment as a factor of national competitiveness in manufacturing.- Indicators for sustainable energy development from a negentropic perspective.- Sustainability indicators for anticipating the fickleness of human-environmental interaction.- Measuring Sustainability - Index of Balanced Sustainable Development.- Evaluating the Environmental Friendliness, Economics and Energy Efficiency of Chemical Processes: Heat Integration.- Eco-efficiency reporting exemplified by case studies.- Interpolation for creating hydrogeological models.- Indicators of Sustainable Production.- Remote Sensing as a Tool for Achieving and Monitoring Progress Toward Sustainability.- Summary of Panel Discussions.

Total site: wastewater minimization: Wastewater reuse and regeneration reuse

Abstract Analysis of technological wastewater streams in a refinery and petrochemical complex was carried out. Wastewater flowrates, temperatures, pH and pollutant contents were measured. Regarding the characteristics of the individual waters, possible connections between water outflows from the processes or process units and potential water consumers were determined. Possibilities to reduce the flowrate of technological wastewater with wastewater reuse or preliminary regeneration and reuse were found. The consumption of fresh water could be lowered by 11.2 m 3 /h, reducing the treatment system load and prolonging its residence time by 7%. The payback period for the changes proposed in the petrochemical plants is 6 months with annual savings of US

Heat integration of reactors—I. Criteria for the placement of reactors into process flowsheet

27 630. The payback period for the changes proposed in the refinery is 11 days with annual savings of US

Cost targeting for HEN through simultaneous optimization approach: a unified pinch technology and mathematical programming design of large HEN

15 500.

Design of Batch Versus Continuous Processes: Part I: Single-Purpose Equipment

Abstract Thermodynamic analysis of reactors and their heat integration into the overall process is presented. The practical energy balance of a reactor can be divided into four items: reaction enthalpy is produced or consumed, reaction enthalpy is transferred to or from the reacting fluid, heat is interchanged between the reacting fluids, and heat is exchanged with the environment. This division enables the separation of the reactors from the heat exchangers network. The last three items can be integrated into the process profile and the first one is drawn separately as a reactor profile (chemical utility) on the temperature/enthalpy diagram. The appropriate placement of exothermic reactors is above the pinch, while the appropriate placement of endothermic reactors is below the pinch. The reactor profile can be matched with the process profile by changing the process structure (number and volume of reactors, heat exchangers network, the pressure of boilers) and reactor parameters (feed temperature and composition, degree of conversion, pressure, heat interchange and exchange, contacting etc.).

Optimization of ethanol fermentation process design

Abstract This paper describes the simultaneous optimization of process flowsheets and their heat exchanger networks (HENs) using rigorous models and detailed cost functions. An optimization procedure is proposed by which tradeoffs between oprating plus capital costs of a process and utility plus capital costs of their heat integrated HENs are simultaneously taken into account. The procedure relies on a direct search optimization method to reduce the effects of nonconvexities and to enable real large-scale industrial problems with a large number of streams to be solved. A special match-dependent cost targeting formula for HEN is introduced to adjust HEN capital costs to different construction characteristics. A Discrete Complex Algorithm (DCA) is proposed for direct search optimization in a reduced feasible region defined over sets of discretized decision variables. The direct search results in a final HEN design. A simple, yet very robust, nonlinear programming (NLP) optimization model is developed to design HEN with practically any number of streams using the same capital cost function for HEN as in the direct search. The whole optimization procedure is illustrated by the optimization of an existing large-scale chemical process at increasing levels of simultaneity ranging from the sequential to the simultaneous HEN optimization.

Process integration of a steam turbine

Complex design procedures for a continuous and for a single product batch plant were compared. Production rate, process structure and energy integration which influence desision-making about continuous or batch operating mode, were considered. The final conclusion after applying economic analysis to all variants with single-purpose equipment is that a continuous plant with recycles after energy integration is more profitable than a batch one for all capacities, unless special reasons exist why reactors should be operated the batch way. An example calculation for a process which is planned to produce a specialty product with three reactions is used to compare the net present worth of continuous and discontinuous operation modes.

A simple method for systematic synthesis of thermally integrated distillation sequences

Abstract The ethanol fermentation process using molasses as the feedstock has been studied. The process alternatives, compared to the original fermentation process described in the literature, have been modeled using single and double distillation columns. Short-cut and rigorous models for the distillation column were compared and their influence on the process economics indicate the rigorous model to be more exact, the short-cut model to be faster and more convenient for comparative analysis of finding the optimal process structure. The process with the single distillation column was shown to be the optimal variant requiring the lowest equipment and utilities cost. Estimated net present worth value for the single column was 29.6 MUSD and for the double columns 27.1 MUSD. A heat pump use was found to be a possible option for heat integration. The span of temperatures in distillation columns was confirmed to be the decisive factor for the economy of heat pump use. The pay back time was more than 5 years. Thermal integration reduced the total annual costs by 27% as compared to the basic process scheme.

Design of Batch Versus Continuous Processes: Part III: Extended Analysis of Cost Parameters

Cogeneration consists of combined production of electricity and heat using fuel which allows remarkable energy savings in comparison with a system producing electricity and heat separately. The possibilities for integrating a cogeneration system with chemical processes has been studied in this paper. Improvement in the systems where high temperature process streams exist can be achieved by direct integration of steam turbine with them. A hot reactor stream was used instead of fuel to produce electricity and steam for further process heat requirements. A thermodynamics oriented approach to identify a cogeneration plant that completely satisfies process heat and power demand is highlighted. Pinch analysis with extended grand composite curve enables rational choice of utilities. The acrylic acid process was used to illustrate the procedure proposed. Economic attractiveness based on payback time and net present worth indicated that the steam turbine based cogeneration system would yield a return period of less than 3 months, showing that the investment in cogeneration could be of interest for this plant.