1,721,024 research outputs found
An MPEC formulation for dynamic optimization of distillation operations
Get PDFWe consider the dynamic optimization of chemical processes with changes in the number of equilibrium phases. Recent work has shown that transitions in the number of phases can be modeled as a mathematical program with equilibrium constraints (MPEC). This study generalizes the MPEC to consider dynamic characteristics. In particular, we describe a simultaneous discretization and solution strategy for dynamic optimization problems with complementarity constraints. These discretized problems are then solved with IPOPT-C, a recently developed barrier method for MPEC problems. Our approach is applied to two distillation examples. In the first, we consider the optimal startup of a binary batch distillation problem. In the second, we consider the dynamic operation of a cryogenic column for the separation of natural gas liquids. Both cases demonstrate the effectiveness of the approach on large scale MPEC problems.Fil: Rajendran, Arvind. University of Carnegie Mellon; Estados UnidosFil: Díaz, María Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Biegler, Lorenz Theodor. University of Carnegie Mellon; Estados Unido
Conceptual design of adsorptive recovery of ethane from residue gas stream using Na-ETS-10
No full textThis work provides the conceptual design of a pressure/vacuum swing adsorption cycle for recovering ethane from the residue gas stream (a mostly methane stream) using Na-ETS-10 as the adsorbent. The conceptual design for treating a stream with 2.4% ethane (and the rest methane) evolved from a simple 4-step cycle to more complex configurations which were able to simultaneously improve the ethane purity and recovery. Feed temperature played a key role in the cycle performance in terms of purity and recovery. The minimization of the recompression work of the light product (methane) was achieved by proposing a cycle design which includes a heavy reflux step at high pressure and a further pressure equalization step. Purity values up to 88% ethane with recoveries of 95% and productivities higher than 0.4 mol ethane/m3(ads)s were quantified through the optimization of the operating conditions for the reduced energy-cost adsorption cycle suggesting an alternative for ethane recovery in gas processing plants.Fil: Avila, Adolfo María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; ArgentinaFil: Estupiñan Perez, Libardo. University of Alberta; CanadáFil: Rajendran, Arvind. University of Alberta; Canad
Do adsorbent screening metrics predict process performance? A process optimisation based study for post-combustion capture of CO2
No full textRecent interest in carbon dioxide capture has led to development of hundreds of adsorbents. The selection of the adsorbents and analyzing their performance for a given process is a challenging task. Usually, the expected performances of these adsorbents are evaluated by inspecting the isotherms and using simple adsorbent screening metrics (selectivities, working capacities, figures of merit, etc.). In this work, a process-optimization based approach to screen adsorbents for post-combustion CO2 capture for vacuum swing adsorption (VSA) is presented. Four different adsorbents (Mg-MOF-74, UTSA-16, Zeolite 13X and activated carbon) were chosen as test materials and were subjected to process-optimization studies on a 4-step PSA cycle with light product pressurization (LPP). Two kinds of process optimization studies were performed. The first to maximize purity and recovery and the second to minimize energy consumption and maximize productivity subject to purity/recovery constraints. This study highlights that most commonly used adsorbent metrics do not necessarily rank the performance of the materials at a process scale. It is also shown that the process performance was more sensitive to the affinity of N2 than that of CO2.Fil: Rajagopalan, Ashwin Kumar. University of Alberta; CanadáFil: Avila, Adolfo María. University of Alberta; Canadá. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rajendran, Arvind. University of Alberta; Canad
Process Optimization-Based Adsorbent Selection for Ethane Recovery from Residue Gas
Get PDFThe design and optimization of a pressure/vacuum swing adsorption process for the separation of ethane (C2) from residue gas (2.4 mol% ethane and the rest being methane) is presented. To achieve this, experimental measurements, modelling and optimization tools are developed to characterize the adsorbents, define the cycle configuration, and find the optimal operating conditions for the process. adsorbents from two different families, namely, titanosilicate (Na- ETS-10) and activated carbons are chosen. Experimental high-pressure isotherms were measured and described using a dual-site Langmuir model. A rigorous one-dimensional model is developed to simulate the adsorption process. Three different cycle configurations are proposed and assessed based on C2 purity and recovery. The effect of feed temperature is studied and is shown to have 10 a high impact on the separation. Finally, a multi-objective optimization study is performed to identify the material that offers the best trade-off between the two objective functions: C2 purity and recovery. Among the adsorbents examined, Na-ETS-10 is found to provide best performance with a possibility of obtaining ≈ 76% purity at a recovery of 68%.Fil: Estupiñan Perez, Libardo. University of Alberta; CanadáFil: Avila, Adolfo María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina. University of Alberta; CanadáFil: Sawada, James A.. University of Alberta; CanadáFil: Rajendran, Arvind. University of Alberta; CanadáFil: Kuznicki, Steven M.. University of Alberta; Canad
Development of dynamic column breakthrough for multicomponent adsorption equilibrium and diffusion
No full textPressure and temperature swing adsorption processes are increasingly being designed and optimized computationally. The reliability of these predictions are highly dependent on the quality of the experimental equilibrium and kinetic data used in these simulations. Consistent experimental methodology is fundamental to obtain accurate data. The main aims of this thesis are to provide multicomponent adsorption equilibrium and kinetic data on various adsorbents, to provide recommendations to improve experimental methodology, and finally to use this data for pressure swing adsorption design and optimization. Dynamic column breakthrough is extensively studied in this thesis. This method involves a column packed with an adsorbent of interest that can measure multicomponent equilibrium and kinetics, as well as column dynamics. This thesis examines all three of these aspects in dynamic column breakthrough. A few highlights are described below.
The equilibrium loading of each species in a multicomponent mixture can be calculated from a dynamic column breakthrough experiment. This is most commonly done with a ternary gas mixture for a binary equilibrium measurement: the column is initialized with an inert gas (such as helium), and then replaced with a binary mixture of adsorbates. After the experiment is finished, a transient mass balance can be solved to yield an equilibrium loading for each species in the mixture. However, a ternary adsorption breakthrough experiment (two adsorbates and one inert) on a highly selectively system, will often yield erroneous equilibrium data for the weaker component. This is in part due to the measurement of effluent flow, and part due to the long experimental times that accumulate error in the transient mass balance. It was found that a desorption breakthrough experiment, performed after a desired multicomponent adsorption experiment, yielded more accurate data with less associated error for the weaker species. This is due to the relatively short experimental time for the weaker component to desorb, minimizing the accumulation of error in the mass balance. The stronger component can be calculated from the adsorption breakthrough experiment. The combined elution profile yields the binary equilibrium data at a given composition, temperature and total pressure. The error associated with the adsorption mass balance of the weaker component can also be bypassed by performing true binary experiments without an inert (only the two adsorbates of interest). These experiments are performed by saturating the column with one adsorbate of interest, and then performing an adsorption breakthrough experiment with a binary mixed-adsorbate system. This methodology still requires two sets of experiments to obtain a single binary pairing, but avoids error due to roll-up.
Dynamic column breakthrough is usually performed with tens to hundreds of grams of adsorbent. This sample size creates a large signal change in the effluent mole flow measurement, reduces loading variation from heterogeneous samples, and minimizes effects due to the extra-column volume. However, nothing in the transient mass balance excludes measurement on milligram sized samples. This thesis provides recommendations to build a milligram-scale dynamic column breakthrough apparatus to obtain accurate and precise unary and binary equilibrium data. While some aspects of milligram-scale experimentation are complicated, overall the milligram-scale operation offered many more benefits. These included shorter experimental times, near-isothermal operation, a much simpler effluent flow calibration, as well as being able to test as-synthesized and crystalline adsorbents. This apparatus was tested with mixtures of dry gases on various adsorbent materials. This thesis provides quantitative data for unary and binary adsorption equilibrium, and qualitative trends for multicomponent kinetics, from dynamic column breakthrough experiments on milligram quantities of adsorbent
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Process Optimization Based Selection of Adsorbents for Post-combustion CO2 Capture
No full textRecent interest in carbon capture has led to development of 100s of adsorbents. The selection of the adsorbents and analyzing their performance for a given process is a challenging task. Usually, the expected performances of these adsorbents are evaluated by inspecting the isotherms and using simple screening metrics (selectivities, working capacities, figures of merit), whereas very few claims are made based on process-scale studies. In this work, we present a systematic approach to screen adsorbents for post-combustion CO2 capture which accounts for the complexities associated with the process and gives an overall picture of the adsorbent performance for the chosen process using a pressure swing adsorption (PSA) cycle model coupled with a genetic algorithm based optimization with an objective to maximize purity/recovery and maximize productivity/minimize energy. Simulation experiments have been set up using Zeolite 13X as the base case and hypothetical adsorbents with constant henry selectivity and fixed CO2/N2 isotherms. It was found for adsorbents with a selectivity of 365 (corresponding to 13X), for 90% CO2 recovery, the weakly and strongly adsorbing adsorbents are able to achieve a purity of 95% and 80%, respectively. For adsorbents with a selectivity of 365 satisfying the purity/recovery constraint, the weakly and strongly adsorbing adsorbent utilizes 120 and 180 kWh/tonne CO2 captured, respectively. For the experiments set up in this work we show that post-combustion CO2 capture is not a CO2 capture problem, but a N2 removal problem.Fil: Rajagopalan, Ashwin Kumar. University of Alberta; CanadáFil: Perez, L. E.. University of Alberta; CanadáFil: Avila, Adolfo María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina. University of Alberta; CanadáFil: Rajendran, Arvind. University of Alberta; Canadá65th Canadian Chemical Engineering ConferenceCalgaryCanadáCanadian Society for Chemical Engineerin
Screening tools for adsorption based post-combustion CO2 capture
No full textSolid-sorbent based CO2 capture holds the promise for reducing energy consumption for post-combustion CO2. The efficacy of a particular sorbent is judged based on simple screening metrics such as selectivity, working capacity or combinations of these. Recently, our group used process optimization to demonstrate that these metrics are poor indicators of sorbent performance at a process scale as they do not take into account the complexities of the process. Hence, the natural question to ask is ?How best to screen solid sorbents by also taking into account process design??. In this presentation, we discuss two approaches to answer this question. The first one is based on rigorous optimization based on detailed models that takes into account heat and mass transfer effects, cycle configuration, process limitations, etc. This approach provides the trade off between energy consumption and productivity. While being rigorous they are computation intensive and not amenable for screening hundreds of materials. The second approach is the development of equilibrium based models that take into account the key aspects of process operation but avoid the complexities of heat and mass transfer. These models are simple and can be solved with minimal computation effort. We show that they provide correct ranking of the materials. These studies provide some counter-intuitive results which can be valuable for designing new solid-sorbents.Fil: Rajagopalan, Ashwin Kumar. University of Alberta; Canadá. Eidgenossische Technische Hochschule zurich (eth Zurich);Fil: Pauw, R. D.. University of Alberta; Canadá. Vrije Unviversiteit Brussel; BélgicaFil: Avila, Adolfo María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina. University of Alberta; CanadáFil: Rajendran, Arvind. University of Alberta; Canadá66th Canadian Chemical Engineering ConferenceQuebecCanadáChemical Institute of Canad
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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