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2. Process integration of a steam turbineAndreja Goršek, Peter Glavič, 2003, izvirni znanstveni članek Opis: Cogeneration consists of combined production of electricity and heat using only one 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 streams exist can be achieved by direct integration of steam turbine with them. Hot reactor utility was used instead of fuel to produce electricity and steam for further process heat requirements. A thermodinamics oriented approach to identify and preliminary design 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 return period of less than 3 months, showing that the investment in cogeneration could be of interest for this plant. Ključne besede: process energetics, efficient energy use, process industry, cogeneration systems, acrylic acid, technological processes Objavljeno: 01.06.2012; Ogledov: 1214; Prenosov: 79 Povezava na celotno besedilo |
3. Multi-criteria optimization in a methanol processAnita Kovač Kralj, Peter Glavič, 2009, izvirni znanstveni članek Opis: Opportunities for additional profit in retrofits depend very much on the existing plant structure, its parameters and energy system. Combined production of heat flow rate, power and chemical products can improve process efficiency. This paper presents an application of the nonlinear programming (NLP) optimization techniques, including increased chemical product output, heat integration and electricity cogeneration by changing amount flow ratios of raw material, and modifying the separation and reaction systems. The existing NLP model has been extended with basic chemical kinetics, including the effects of changing raw material flow rate ratios on product yield. A case studied methanol plant was optimized using the NLP model developed earlier by including an additional flow rate of hydrogen (H2), decreasing flowrate of high-pressure steam in crude methanol recycling, and increasing methanol production by 2.5%. The potential additional profit from the cogeneration and additional methanol production was estimated to be 2.51 MEUR/a. Ključne besede: chemical processes, methanol, simultaneous optimization, NLP, cogeneration, flow rate ratios Objavljeno: 01.06.2012; Ogledov: 1366; Prenosov: 80 Povezava na celotno besedilo |
4. H2 separation and use in fuel cells and CO2 separation and reuse as a reactant in the existing methanol processAnita Kovač Kralj, Peter Glavič, 2007, izvirni znanstveni članek Opis: Fuel-cell efficiencies yield substantial reductions in the emissions of climate-change gases and promise an end to exclusive reliance on carbon fuels for energy. Fuel cells, CO2 reuse, process heat integration, and open gas turbine electricity cogeneration can be optimized simultaneously, using a nonlinear programming (NLP) algorithm. The simplified NLP model contains equations of structural and parametric optimization. This NLP model is used tooptimize complex and energy-intensive continuous processes. This procedure does not guarantee a global cost optimum, but it does lead to good, perhaps near-optimum, designs. The plant, which produces methanol, has a surplus of hydrogen (H2) and CO2 flow rates in purge gas. H2 is separated from the purge gas by an existing pressure swing adsorption (PSA) column. Pure H2 can be usedas fuel in fuel cells. CO2 can be separated from the outlet stream (purge gas) by a membrane or absorption system (absorber and regenerator) or an adsorption system and reused as a reactant in a reactor system. Therefore, theproduct yield can be increased and CO2 emissions can be reduced, simultaneously. CO2 emissions can then be reduced at the source. The retrofitted process can be operated within existing parameters. Using a methanol process as a case study, the CO2 emission flow rate can be reduced by4800 t/a. The additional electricity cogeneration in the gas turbine and in fuel cells and additional flow rates of the raw material could generate an additional profit of 2.54 MEUR/a. Ključne besede: chemical processing, methanol production, optimization, nonlinear programming, CO2 reuse, fuel cells, heat integration, energy cogeneration Objavljeno: 31.05.2012; Ogledov: 1818; Prenosov: 60 Povezava na celotno besedilo |
5. Optimization of a gas turbine in the methanol process, using the NLP modelAnita Kovač Kralj, Peter Glavič, 2007, izvirni znanstveni članek Opis: Heat and power integration can reduce fuel usage, CO2 and SO2 emissions and, thereby, pollution. In the simultaneous heat and power integration approach and including additional production, the optimization problem is formulated using a simplified process superstructure. Nonlinear programming (NLP) contains equations which enable structural heat and power integration and parametric optimization. In the present work, the NLP model is formulated as an optimum energy target of process integration and electricity generation using a gas turbine with a separator. The reactor acts as a combustion chamber of the gas turbine plant, producing high temperature. The simultaneous NLP approach can account for capital cost, integration of combined heat and power, process modification, and additional production trade-offs accurately, and can thus yield a better solution. It gives better results than non-simultaneous methods. The NLP model does not guarantee a global cost optimum, but it does lead to good, perhaps near optimum designs. This approach is illustrated by an existing, complex methanol production process. The objective function generates a possible increase in annual profit of 1.7 M EUR/a. Ključne besede: chemical processes, methanol, simultaneous optimization, NLP, cogeneration, gas turbine Objavljeno: 31.05.2012; Ogledov: 1558; Prenosov: 74 Povezava na celotno besedilo |
6. Energy saving and modifications in the methanol process, using the NLP model optimizationAnita Kovač Kralj, Peter Glavič, 2006, objavljeni znanstveni prispevek na konferenci Opis: The opportunities for additional profit depend very much on the existing plant and energy system. Heat and power integration can reduce fuel usage in chemical processes. Nonlinear programming contains equations which enable structural and parametric optimization. The NLP model is formulated using an optimum energy target of process integration and electricity generation using a gas turbine with separator. The reactor acts as a combustion chamber of the gas turbine plant, producing a lot of energy. The simultaneous NLP approach can account for capital cost, integration of combined heat and power, process modification and additional production of trade-offs, and can thus yield a better solution. The combined production of electricity, heat and chemical products can lead to better process efficiency. The methanol plant was optimized using a mathematical nonlinear programming model by including an additional flowrate of hydrogen in crude methanol recycle and increasing the methanol production by 2,5%. The electricity can be generated in methanol recycle using a gas turbine. The total additional profit is 2,5 MEUR/a. Ključne besede: chemical engineering, methanol production, simultaneous process optimization, nonlinear programming, cogeneration, product increase Objavljeno: 30.05.2012; Ogledov: 1765; Prenosov: 21 Povezava na celotno besedilo |
7. Design of the optimal total site heat recovery system using SSSP approachAndreja Goršek, Peter Glavič, Miloš Bogataj, 2006, izvirni znanstveni članek Opis: Site expansions or changes in production capacities are usually related with changes of utilities demands andžor utility system design. Despite several available and well established techniques for process synthesis and integration, very often, changes in process designs are made on the basis of intuition and experiences of engineers. In this paper possibilities of rational energy consumption and energy integration in an existing site for production of specialty chemicals were studied. On the basis of real process parameters and computer simulation results energy integration was re-examined.Total site analysis using modified Site Sink Source Profiles, which gives a profound insight into the site utility system configuration, heating-cooling demands and cogeneration design was performed. The existing site was found to be very well designed. With only few modifications additional 9% of hot utilities and 5% of cold utilities savings are possible. Ključne besede: chemical engineering, process design, optimization, heat integration, cogeneration, pinch method, energy retrofit Objavljeno: 30.05.2012; Ogledov: 2032; Prenosov: 73 Povezava na celotno besedilo |