FRRo - I+D+i - Artículos en Revistas

Permanent URI for this collectionhttp://48.217.138.120/handle/20.500.12272/1297

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Author: search.filters.author.Scenna, Nicolás JoséEnd date: 2019

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Now showing 1 - 10 of 13
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    Optimal design of a two-stage membrane system for hydrogen separation in refining processes.
    (2018-10-31) Arias, Ana Marisa; Mores, Patricia Liliana; Scenna, Nicolás José; Caballero, José Antonio; Mussati, Sergio Fabián; Mussati, Miguel Ceferino
    This paper fits into the process system engineering field by addressing the optimization of a two-stage membrane system for H2 separation in refinery processes. To this end, a nonlinear mathematical programming (NLP) model is developed to simultaneously optimize the size of each membrane stage (membrane area, heat transfer area, and installed power for compressors and vacuum pumps) and operating conditions (flow rates, pressures, temperatures, and compositions) to achieve desired target levels of H2 product purity and H2 recovery at a minimum total annual cost. Optimal configuration and process design are obtained from a model which embeds different operating modes and process configurations. For instance, the following candidate ways to create the driving force across the membrane are embedded: (a) compression of both feed and/or permeate streams, or (b) vacuum application in permeate streams, or (c) a combination of (a) and (b). In addition, the potential selection of an expansion turbine to recover energy from the retentate stream (energy recovery system) is also embedded. For a H2 product purity of 0.90 and H2 recovery of 90%, a minimum total annual cost of 1.764 M$·year−1 was obtained for treating 100 kmol·h−1 with 0.18, 0.16, 0.62, and 0.04 mole fraction of H2, CO, N2, CO2, respectively. The optimal solution selected a combination of compression and vacuum to create the driving force and removed the expansion turbine. Afterwards, this optimal solution was compared in terms of costs, process-unit sizes, and operating conditions to the following two suboptimal solutions: (i) no vacuum in permeate stream is applied, and (ii) the expansion turbine is included into the process. The comparison showed that the latter (ii) has the highest total annual cost (TAC) value, which is around 7% higher than the former (i) and 24% higher than the found optimal solution. Finally, a sensitivity analysis to investigate the influence of the desired H2 product purity and H2 recovery is presented. Opposite cost-based trade-offs between total membrane area and total electric power were observed with the variations of these two model parameters. This paper contributes a valuable decision support tool in the process system engineering field for designing, simulating, and optimizing membranebased systems for H2 separation in a particular industrial case; and the presented optimization resultsprovide useful guidelines to assist in selecting the optimal configuration and operating mode.
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    Membrane-based processes: optimization of hydrogen separation by minimization of power, membrane area, and cost.
    (2018-11-12) Mores, Patricia Liliana; Arias, Ana Marisa; Scenna, Nicolás José; Caballero, José Antonio; Mussati, Sergio Fabián; Mussati, Miguel Ceferino
    This work deals with the optimization of two-stage membrane systems for H2 separation from off-gases in hydrocarbons processing plants to simultaneously attain high values of both H2 recovery and H2 product purity. First, for a given H2 recovery level of 90%, optimizations of the total annual cost (TAC) are performed for desired H2 product purity values ranging between 0.90 and 0.95 mole fraction. One of the results showed that the contribution of the operating expenditures is more significant than the contribution of the annualized capital expenditures (approximately 62% and 38%, respectively). In addition, it was found that the optimal trade-offs existing between process variables (such as total membrane area and total electric power) depend on the specified H2 product purity level. Second, the minimization of the total power demand and the minimization of the total membrane area were performed for H2 recovery of 90% and H2 product purity of 0.90. The TAC values obtained in the first and second cases increased by 19.9% and 4.9%, respectively, with respect to that obtained by cost minimization. Finally, by analyzing and comparing the three optimal solutions, a strategy to systematically and rationally provide ‘good’ lower and upper bounds for model variables and initial guess values to solve the cost minimization problem by means of global optimization algorithms is proposed, which can be straightforward applied to other processes.
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    Cost-based comparison between membrane systems and chemical absorption processes for CO2 capture from flue gas.
    (2019-05-09) Arias, Ana Marisa; Mores, Patricia Liliana; Scenna, Nicolás José; Caballero, José Antonio; Mussati, Miguel Ceferino; Mussati, Sergio Fabián
    An optimization study of membrane-based separation systems for carbon dioxide capture from flue gas of power plants is conducted, considering the possibility of employing up to four stages and using diverse options to create the required driving force. By proposing a superstructure-based model, the number of stages, recycle options, use of feed compression and/or permeate vacuum, driving force distribution along each membrane stage, operating conditions and equipment sizes are simultaneously optimized in order to minimize the total annual cost at high capture ratios and purity targets. Thus, different optimal arrangements are obtained and the total cost is reduced in about 20% compared without employing vacuum. Besides the optimal number of stages diminishes with decreasing purity, but it is independent of the capture ratio. Also, the total cost decreases with the increase of the membrane permeance requiring lower values of operating pressure and membrane areas. Permeance values higher than 2400 GPU lead to lower number of stages and recycles for the same separation target. By contrast, a sensitivity analysis shows that the total cost increases with the increase of the electricity price, capacity factor, and capital recovery factor, which are the more influential parameters in the objective function. Despite new optimal operating and design conditions are obtained when these parameters vary, no modifications in the optimal arrangement are observed.
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    Optimization of the design, operating conditions, and coupling configuration of combined cycle power plants and CO2 capture processes by minimizing the mitigation cost.
    (2017-10-04) Mores, Patricia Liliana; Manassaldi, Juan Ignacio; Scenna, Nicolás José; Caballero, José Antonio; Mussati, Miguel Ceferino; Mussati, Sergio Fabián
    This paper deals with the optimization of the coupling between a natural gas combined cycle (NGCC plant and a post-combustion CO2 capture process by minimizing the mitigation cost – defined as the ratio between the cost of electric power generation and the amount of CO2 emitted per unit of total net electric power generated – while satisfying the design specifications: electric power generation capacity and CO2 capture level. Three candidate coupling configurations, which differ in the place where the steam is extracted from, are optimized using detailed and rigorous models for both the NGCC and the CO2 capture plants. By comparing the mitigation cost of each configuration, the optimal integration configuration and the corresponding optimal sizes and operating conditions of all process units (steam turbines, gas turbines, heat recovery steam generators HRSGs, absorption and regeneration columns, reboilers and condensers, and pumps) are provided. In the computed optimal solution, the steam required by the CO2 capture plant is extracted from both the steam turbine and the HRSG (evaporator operating at low pressure), and the mitigation cost is 90.88 $/t CO2. The optimal solution is compared with suboptimal solutions corresponding to the other two candidate coupling schemes. These solutions are compared in detail regarding capital investment.
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    Development of extrinsic functions for optimal synthesis and design : application to distillation-based separation processes.
    (2019-04-09) Manassaldi, Juan Ignacio; Mussati, Miguel Ceferino; Scenna, Nicolás José; Mussati, Sergio Fabián
    This work deals with the development and implementation of mathematical models in the General Algebraic Modeling System (GAMS) environment for optimization purposes, involving extrinsic functions that are executed outside GAMS from dynamic-link libraries (DLL) implemented in the programming language C. Three DLL libraries are developed to calculate thermodynamic properties: the Raoult's law for vapor-liquid equilibrium, the Non-Random Two-Liquid (NRTL) model, and the Peng–Robinson equation of state. A detailed description on how GAMS and DLL libraries interact is presented. Case studies dealing with the optimal design of multi-component distillation columns with increasing complexity levels are discussed. For the proposed case studies, the obtained results show that the usage of the proposed extrinsic functions allows to significantly enhance the model implementation compared to the traditional model implementation approach, and to considerably reduce the model size as well as the computational time required by the optimization algorithms.
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    A risk– based design of ammonia refrigeration systems in food manufacturing plants.
    (2019-01) Biscotti, Paola Silvina; Reinheimer, María Agustina; Scenna, Nicolás José
    This paper presents a risk-based design procedure of ammonia based refrigeration processes taking into account the allocation of the manufacturing plant and the surrounding environment vulnerability at early stages of process design. In addition, the proposed design framework allows the integration of a process simulator with vulnerability assessment packages. As a case study, the design of the refrigeration system for a surimi manufacturing plant is presented.
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    Optimal life cycle oriented design of a GT + 1PSH HRSG type CCGT power plant.
    (2010) Godoy, Ezequiel; Benz, Sonia Judith; Scenna, Nicolás José
    In the present work, a life cycle oriented approach is used for designing power plants in a way they can satisfy the desired demand along the whole time horizon, while a selected performance indicator of the project is optimized. As case study, optimal design characteristics as well as optimal values of long term operation parameters of a GT + 1PSH HRSG Type CCGT power plant (GT: gas turbine, 1PSH HRSG: 1 pressure with superheater-heat recovery steam generator, CCGT: combined cycle gas turbine) are obtained by means of a multiperiod mathematical model, seeing that the selected performance indicator is maximized. In addition, advantages of the life cycle oriented approach results are discussed when compared with a power plant design obtained by traditional methods.
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    Comparison between conventional and ultrasoundassisted techniques for extraction of anthocyanins from grape pomace. Experimental results and mathematical modeling
    (Elsevier, 2017-03-16) Bonfigli, Mónica Beatriz; Godoy, Ezequiel; Reinheimer, María Agustina; Scenna, Nicolás José
    Conventional and ultrasound assisted extraction of anthocyanins from grape pomace are here analyzed and compared. Mathematical modeling is used firstly to represent the extraction process and determine the associated mass transport parameters, and afterwards, to obtain useful predictions on how the system behaves under different operating conditions. The mathematical model here developed is based on first-principles, in order to more accurately describe the underlying phenomena that govern the extraction process behavior. Extraction of anthocyanins from grape pomace is performed using a hydro alcoholic solution as solvent, and experimental runs at different temperatures were carried out for both conventional and ultrasound-assisted techniques. A good agreement between experimental and computed extraction yields was achieved as the reported statistical parameters indicate. Obtained results highlight the performance differences between both processes, and pinpoint which variables impact the most in the extraction yield.
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    Optimal economic strategy for the multiperiod design and long-term operation of natural gas combined cycle power plants.
    (Elsevier, 2012-08-25) Godoy, Ezequiel; Scenna, Nicolás José; Benz, Sonia Judith
    Optimal power plant designs are achieved by means of a proposed multiperiod non-linear programming formulation that utilizes the net present value as objective function, while construction, operation and dismantling of the generation facility are accounted for. In addition, optimal operative characteristics are also established for each operative time period, in a way that the system constraints are always satisfied. Based on the life cycle oriented economic optimal characteristics, a reduced model is proposed as strategy for simplifying the resolution of the rigorous multiperiod model. Trends in the system behavior are identified, enabling the reduction of the multiperiod formulation into a system of non-linear equations plus additional constraints, which allows easily computing accurate estimations of the optimal values of the design variables as well as the time-dependent operative variables.
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    An optimization model for evaluating the economic impact of availability and maintenance notions during the synthesis and design of a power plant
    (Elsevier, 2017-01-27) Godoy, Ezequiel; Benz, Sonia Judith; Scenna, Nicolás José
    In this paper, we introduce an optimization strategy in order to comprehensively quantify the impact of availability and maintenance notions during the early stages of synthesis and design of a new natural gas combined cycle power plant. A detailed state-space approach is thoroughly discussed, where influence of maintenance funds on each component’s repair rate is directly assessed. In this context, analysis of the reliability characteristics of the system is centered at two designer-adopted parameters, which largely influence the obtained results: the number of components which may fail independently at the same time, and the number of simultaneous failure/repair events. Then, optimal solutions are evaluated as the availability-related parameters and the amount of resources assigned for maintenance actions are varied across a wide range of feasible values, which enable obtaining more accurate and detailed estimations of the expected economic performance for the project when compared with traditional economic evaluation approaches.