1. Heat integration between two biodiesel processes using a simple methodAnita Kovač Kralj, 2008, izvirni znanstveni članek Opis: Biodiesel is a clean-burning alternative fuel, produced from domestic, renewable resources. Biodiesel can be blended at any level with petroleum diesel to create a biodiesel blend. It can be used in compression-ignition (diesel) engines with little or no modification. Biodiesel is simple to use, biodegradable, nontoxic, and essentially free of sulfur and aromatics. This paper presents heat integration between two biodiesel processes. Biodiesel can be produced by the esterification of different fatty acids (high and low boiling point) with alcohols. This simple method for heat integration is based on three possible steps. Simultaneous integration between processes can be performed using a stagewise model with a mixed integer nonlinear programming (MINLP) algorithm (step 3), which can include alternatives suggested by pinch analysis of heat transfer between the processes (step 2). The internal integration of individual processes can be performed in step 1. The fraction can be calculated for maximum integration between processes. Integration between the processes can be carried out using all three steps or by the first and third steps or by the last step only, depending on the problems' complexities. This method includes streams of different processes which are heated or cooled using a utility only. The existing heaters and coolers can be left unchanged in their original processes or can be used for integrating heat between processes, with hot and cold utilities being saved. This approach is illustrated by integrating two simulated biodiesel processes.The objective was to maximize additional annual profit for integration between processes by USD8300/a. Ključne besede: chemical processing, biodiesel producing, heat integration, nonlinear programming Objavljeno: 31.05.2012; Ogledov: 1310; Prenosov: 56 Povezava na celotno besedilo |
2. Heat integration in a speciality product processMajda Krajnc, Anita Kovač Kralj, Peter Glavič, 2006, izvirni znanstveni članek Opis: The essence of effective process designing is to use methods which are efficient to engineers in practice and not only to scientists. The proposed design procedure is composed of two steps: conceptual one and optimization one. At the conceptual step, pinch design analysis is used. In the optimization step pinch analysis and mixed-integer nonlinear programming method are applied. In the case study analysed, a speciality product is to beproduced in continuous chemical process with a capacity which causes smallerheat flow rates and needs smaller heat exchanger areas than usual. Therefore, an equation for cost estimation of heat exchangers with areas smaller than 7 m2 was developed and used in the optimization procedure. Using thermodynamic pinch analysis and mathematical programming method, the heat integrated structures were synthesized and compared with the base process flowsheet. Finally, the optimal structure was determined. Ključne besede: načrtovanje procesov, načrtovanje procesov, ekonomska analiza, prenos toplote, optimizacija, chemical process design, economic analysis, heat integration, optimization Objavljeno: 30.05.2012; Ogledov: 1623; Prenosov: 48 Povezava na celotno besedilo |
3. 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: 1927; Prenosov: 70 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: 1735; Prenosov: 57 Povezava na celotno besedilo |
5. Synthesis of non-isothermal heat integrated water networks in chemical processesMiloš Bogataj, Miguel J. Bagajewicz, 2008, izvirni znanstveni članek Opis: This paper presents a new approach for the simultaneous synthesis and optimization of heat integrated water networks. A new superstructure for heat exchanger network (HEN) synthesis is proposed. The procedure is based on mixed integer non-linear mathematical programming (MINLP). Four relevant examples are presented to illustrate various aspects of the proposed approach. Ključne besede: chemical processing, chemical process design, process water networks, water networks, wastewater minimization, heat integration, MINLP, HEN synthesis, superstructures, process synthesis Objavljeno: 31.05.2012; Ogledov: 1422; Prenosov: 70 Povezava na celotno besedilo |