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Records added in 2018
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Showing records 997 to 1021 of 1025. [First] Page: 1 37 38 39 40 41 42 Last
A Dynamic Optimization Model for Designing Open-Channel Raceway Ponds for Batch Production of Algal Biomass
Soumya Yadala, Selen Cremaschi
July 30, 2018 (v1)
Keywords: algae cultivation, batch production, Dynamic Modelling, harvest period, mathematical programming, parameter optimization, raceway pond design
This work focuses on designing the optimum raceway pond by considering the effects of sunlight availability, temperature fluctuations, and harvest time on algae growth, and introduces a dynamic programing model to do so. Culture properties such as biomass productivity, growth rate, and concentration, and physical properties, such as average velocity, pond temperature, and rate of evaporation, were estimated daily depending on the dynamic behavior of solar zenith angle, diurnal pattern of solar irradiance, and temperature fluctuations at the location. Case studies consider two algae species (Phaeodactylum. tricornutum and Isochrysis. galbana) and four locations (Tulsa, USA; Hyderabad, India; Cape Town, South Africa; and Rio de Janeiro, Brazil). They investigate the influences of the type of algae strain and geographical location on algae biomass production costs. From our case studies, the combination of I. galbana species grown in Hyderabad, India, with a raceway pond geometry of 30 cm... [more]
Gaussian Mixture Model-Based Ensemble Kalman Filtering for State and Parameter Estimation for a PMMA Process
Ruoxia Li, Vinay Prasad, Biao Huang
July 30, 2018 (v1)
Keywords: ensemble Kalman filter, expectation maximization, Gaussian mixture model, particle filter, polymethyl methacrylate, state and parameter estimation
Polymer processes often contain state variables whose distributions are multimodal; in addition, the models for these processes are often complex and nonlinear with uncertain parameters. This presents a challenge for Kalman-based state estimators such as the ensemble Kalman filter. We develop an estimator based on a Gaussian mixture model (GMM) coupled with the ensemble Kalman filter (EnKF) specifically for estimation with multimodal state distributions. The expectation maximization algorithm is used for clustering in the Gaussian mixture model. The performance of the GMM-based EnKF is compared to that of the EnKF and the particle filter (PF) through simulations of a polymethyl methacrylate process, and it is seen that it clearly outperforms the other estimators both in state and parameter estimation. While the PF is also able to handle nonlinearity and multimodality, its lack of robustness to model-plant mismatch affects its performance significantly.
A Continuous Formulation for Logical Decisions in Differential Algebraic Systems using Mathematical Programs with Complementarity Constraints
Kody M. Powell, Ammon N. Eaton, John D. Hedengren, Thomas F. Edgar
July 30, 2018 (v1)
Subject: Optimization
Keywords: complementarity constraints, differential algebraic equations, dynamic optimization, orthogonal collocation
This work presents a methodology to represent logical decisions in differential algebraic equation simulation and constrained optimization problems using a set of continuous algebraic equations. The formulations may be used when state variables trigger a change in process dynamics, and introduces a pseudo-binary decision variable, which is continuous, but should only have valid solutions at values of either zero or one within a finite time horizon. This formulation enables dynamic optimization problems with logical disjunctions to be solved by simultaneous solution methods without using methods such as mixed integer programming. Several case studies are given to illustrate the value of this methodology including nonlinear model predictive control of a chemical reactor using a surge tank with overflow to buffer disturbances in feed flow rate. Although this work contains novel methodologies for solving dynamic algebraic equation (DAE) constrained problems where the system may experience... [more]
Surrogate Models for Online Monitoring and Process Troubleshooting of NBR Emulsion Copolymerization
Chandra Mouli R. Madhuranthakam, Alexander Penlidis
July 30, 2018 (v1)
Keywords: acrylonitrile butadiene rubber (NBR), artificial neural networks, dynamic optimisation, emulsion copolymerization, inverse modeling, surrogate modeling
Chemical processes with complex reaction mechanisms generally lead to dynamic models which, while beneficial for predicting and capturing the detailed process behavior, are not readily amenable for direct use in online applications related to process operation, optimisation, control, and troubleshooting. Surrogate models can help overcome this problem. In this research article, the first part focuses on obtaining surrogate models for emulsion copolymerization of nitrile butadiene rubber (NBR), which is usually produced in a train of continuous stirred tank reactors. The predictions and/or profiles for several performance characteristics such as conversion, number of polymer particles, copolymer composition, and weight-average molecular weight, obtained using surrogate models are compared with those obtained using the detailed mechanistic model. In the second part of this article, optimal flow profiles based on dynamic optimisation using the surrogate models are obtained for the product... [more]
Combining On-Line Characterization Tools with Modern Software Environments for Optimal Operation of Polymerization Processes
Navid Ghadipasha, Aryan Geraili, Jose A. Romagnoli, Carlos A. Castor Jr, Michael F. Drenski, Wayne F. Reed
July 30, 2018 (v1)
Keywords: dynamic optimization, free radical polymerization, molar mass distribution, online monitoring, parameter estimation
This paper discusses the initial steps towards the formulation and implementation of a generic and flexible model centric framework for integrated simulation, estimation, optimization and feedback control of polymerization processes. For the first time it combines the powerful capabilities of the automatic continuous on-line monitoring of polymerization system (ACOMP), with a modern simulation, estimation and optimization software environment towards an integrated scheme for the optimal operation of polymeric processes. An initial validation of the framework was performed for modelling and optimization using literature data, illustrating the flexibility of the method to apply under different systems and conditions. Subsequently, off-line capabilities of the system were fully tested experimentally for model validations, parameter estimation and process optimization using ACOMP data. Experimental results are provided for free radical solution polymerization of methyl methacrylate.
Acknowledgement to Reviewers of Processes in 2015
Processes Editorial Office
July 30, 2018 (v1)
Subject: Other
The editors of Processes would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2015. [...]
State Observer Design for Monitoring the Degree of Polymerization in a Series of Melt Polycondensation Reactors
Chen Ling, Costas Kravaris
July 30, 2018 (v2)
Keywords: dead time compensation, degree of polymerization, inter-sample output predictor, nonlinear state observer, polycondensation
A nonlinear reduced-order state observer is applied to estimate the degree of polymerization in a series of polycondensation reactors. The finishing stage of polyethylene terephthalate synthesis is considered in this work. This process has a special structure of lower block triangular form, which is properly utilized to facilitate the calculation of the state-dependent gain in the observer design. There are two possible on-line measurements in each reactor. One is continuous, and the other is slow-sampled with dead time. For the slow-sampled titration measurement, inter-sample behavior is estimated from an inter-sample output predictor, which is essential in providing continuous corrections on the observer. Dead time compensation is carried out in the same spirit as the Smith predictor to reduce the effect of delay in the measurement outputs. By integrating the continuous-time reduced-order observer, the inter-sample predictor and the dead time compensator together, the degree of polym... [more]
Optimum Conditions for Microwave Assisted Extraction for Recovery of Phenolic Compounds and Antioxidant Capacity from Macadamia (Macadamia tetraphylla) Skin Waste Using Water
Adriana Dailey, Quan V. Vuong
July 30, 2018 (v2)
Keywords: antioxidant, bioactive, by-products, macadamia, skin, waste
This study aimed to develop optimal microwave assisted extraction conditions for recovery of phenolic compounds and antioxidant properties from the macadamia skin, an abundant waste source from the macadamia industry. Water, a safe, accessible, and inexpensive solvent, was used as the extraction solvent and Response Surface Methodology (RSM) was applied to design and analyse the conditions for microwave-assisted extraction (MAE). The results showed that RSM models were reliable for the prediction of extraction of phenolic compounds and antioxidant properties. Within the tested ranges, MAE radiation time and power, as well as the sample-to-solvent ratio, affected the extraction efficiency of phenolic compounds, flavonoids, proanthocyanidins, and antioxidant properties of the macadamia skin; however, the impact of these variables was varied. The optimal MAE conditions for maximum recovery of TPC, flavonoids, proanthocyanidins and antioxidant properties from the macadamia skin were MAE ti... [more]
Modeling of the Copolymerization Kinetics of n-Butyl Acrylate and d-Limonene Using PREDICI ®
Shanshan Ren, Eduardo Vivaldo-Lima, Marc A. Dubé
July 30, 2018 (v2)
Keywords: d-limonene, Modelling, n-butyl acrylate, polymerization kinetics
Kinetic modeling of the bulk copolymerization of d-limonene (Lim) and n-butyl acrylate (BA) at 80 °C was performed using PREDICI®. Model predictions of conversion, copolymer composition and average molecular weights are compared to experimental data at five different feed compositions (BA mol fraction = 0.5 to 0.9). The model illustrates the significant effects of degradative chain transfer due to the allylic structure of Lim as well as the intramolecular chain transfer mechanism due to BA.
Integrated Process Design and Control of Cyclic Distillation Columns
Seyed Soheil Mansouri
July 30, 2018 (v1)
Keywords: Cyclic Distillation, Driving Froce, Process Control, Process Design, Process Intensification
Integrated process and control design approach for cyclic distillation columns is proposed. The design methodology is based on application of simple graphical design approaches, known from simpler conventional distillation columns. Here, a driving force approach and McCabe-Thiele type analysis is combined. It is demonstrated, through closed-loop and open-loop analysis, that operating the column at the largest available driving force results in an optimal design in terms of controllability and operability. The performance of a cyclic distillation column designed to operate at the maximum driving force is compared to alternative sub-optimal designs. The results suggest that operation at the largest driving force is less sensitive to disturbances in the feed and inherently has the ability to efficiently reject disturbances.
Petroleum coke and Natural gas-To-Liquids Aspen Plus Simulation
Ikenna J Okeke, Thomas A Adams II
July 19, 2018 (v1)
Keywords: Aspen Plus, Fischer-Tropsch Synthesis, Integrated Reforming, Petroleum Coke
Six Aspen Plus simulation files for the conversion of petroleum coke and/or natural gas to liquid fuels (synthetic gasoline and diesel) are presented. The base simulation files were designed with carbon capture and sequestration (CCS) technology with the corresponding plant without CCS.

The processes may include various technologies such as petcoke gasification, integrated gasification and autothermal natural gas reforming, gas cleaning, water gas shift reaction, MDEA based carbon capture, Claus process, FT synthesis, and other processing steps.

The six processes are: PSG_CCS (petcoke standalone gasification with CCS), PSG_No_CCS (petcoke standalone gasification without CCS), PG-INGR_CCS (petcoke gasification integrated natural gas reformer with CCS), PG-INGR_No_CCS (petcoke gasification integrated natural gas reformer without CCS), PG-ENGR_CCS (petcoke gasification external natural gas reformer with CCS), PG-ENGR_No_CCS (petcoke gasification external natural gas reformer with... [more]
LAPSE Stakeholder Report 2018
LAPSE Interessenter Rapport 2018
Thomas A. Adams II
July 16, 2018 (v1)
Subject: Other
Keywords: LAPSE, Stakeholder report
This is the LAPSE stakeholder report for 2018, including news, new features, and the plan for the next year.
Dette er det LAPSE interessenter rapport for 2018, inkludert nyheter, nye funksjoner, og planen for neste år.
Transforming Instruction to Chemical Product Design
Ka M Ng, Warren D Seider
July 11, 2018 (v1)
Subject: Education
Keywords: Innovation, Product Design, Teaching Assessment, Technology Platforms
This paper describes the progress of our efforts to lead the CACHE (Computer Aids for Chemical Engineering Education) Task Force in transforming from chemical process design toward chemical product design. Through CACHE, we are coordinating the development of a library of product-design case studies. Beginning with preliminary product designs created previously over several semesters, we are arranging for faculty experts, knowledgeable in the underlying technology platforms, to work with student groups to enrich the product designs. Over a 3-year period, a collection of approximately 25 case studies is being prepared. This article describes the research envisioned as innovative product designs are created, both egarding applications of new technologies, and product design evolution/evaluation; and in advancing strategies for teaching product design. The anticipated use of these case studies in departments worldwide for design courses taught by similar technology experts, just a few in... [more]
Deterministic Global Optimization with Artificial Neural Networks Embedded
Global deterministische Optimierung von Optimierungsproblemen mit künstlichen neuronalen Netzwerken
Artur M Schweidtmann, Alexander Mitsos
October 15, 2018 (v2)
Subject: Optimization
Artificial neural networks (ANNs) are used in various applications for data-driven black-box modeling and subsequent optimization. Herein, we present an efficient method for deterministic global optimization of ANN embedded optimization problems. The proposed method is based on relaxations of algorithms using McCormick relaxations in a reduced-space [\textit{SIOPT}, 20 (2009), pp. 573-601] including the convex and concave envelopes of the nonlinear activation function of ANNs. The optimization problem is solved using our in-house global deterministic solver MAiNGO. The performance of the proposed method is shown in four optimization examples: an illustrative function, a fermentation process, a compressor plant and a chemical process optimization. The results show that computational solution time is favorable compared to the global general-purpose optimization solver BARON.
Future directions in process and product synthesis and design
Mariano Martín, Thomas A. Adams II
June 25, 2018 (v1)
Keywords: Future Directions, LAPSE, Process Design, Product Design, PSE Technology Tree
We present an overview of the current state-of-the-art of the field of chemical process and product synthesis and design. In this talk, we outline some of the most interesting new challenges and directions for the field, including: new pushes for including renewable energy into chemical systems, related issues with energy storage, the move toward flexible and unsteady-state chemical processes, the considerations of uncertainty into the design process, new advances in specialty processes, process intensification, modularization, and more. Also, we announce and present the PSE Technology Tree Wiki, a community-based encyclopedia for the PSE community that organizes concepts into a technology tree. We also announce and present LAPSE: the Living Archive for Process Systems Engineering, a new open-data / open-access repository for the PSE community, which contains unique and innovative features designed to foster better dissemination of research, easy access to open models and simulations,... [more]
A new approach to the identification of high-potential materials for cost-efficient membrane-based post-combustion CO2 capture
Simon Roussanaly, Rahul Anantharaman, Karl Lindqvist, Brede Hagen
June 22, 2018 (v1)
Keywords: Attainable Region, Carbon Dioxide Capture, gas separation membranes, post-combustion, property maps
Developing “good” membrane modules and materials is a key step towards reducing the cost of membrane-based CO2 capture. While this is traditionally being done through incremental development of existing and new materials, this paper presents a new approach to identify membrane materials with a disruptive potential to reduce the cost of CO2 capture for six potential industrial and power generation cases. For each case, this approach first identifies the membrane properties targets required to reach cost-competitiveness and several cost-reduction levels compared to MEA-based CO2 capture, through the evaluation of a wide range of possible membrane properties. These properties targets are then compared to membrane module properties which can be theoretically achieved using 401 polymeric membrane materials, in order to highlight 73 high-potential materials which could be used by membrane development experts to select materials worth pushing towards further development once practical conside... [more]
Application of a Two-Level Rolling Horizon Optimization Scheme to a Solid-Oxide Fuel Cell and Compressed Air Energy Storage Plant for the Optimal Supply of Zero-Emissions Peaking Power
Jake Nease, Nina Monteiro, Thomas A. Adams II
June 19, 2018 (v1)
We present a new two-level rolling horizon optimization framework applied to a zero-emissions coal-fueled solid-oxide fuel cell power plant with compressed air energy storage for peaking applications. Simulations are performed where the scaled hourly demand for the year 2014 from the Ontario, Canada market is met as closely as possible. It was found that the proposed two-level strategy, by slowly adjusting the SOFC stack power upstream of the storage section, can improve load-following performance by 86% compared to the single-level optimization method proposed previously. A performance analysis indicates that the proposed approach uses the available storage volume to almost its maximum potential, with little improvement possible without changing the system itself. Further improvement to load-following is possible by increasing storage volumes, but with diminishing returns. Using an economically-focused objective function can improve annual revenue generation by as much as 6.5%, but no... [more]
Technical challenges in operating an SOFC in fuel flexible gas turbine hybrid systems: Coupling effects of cathode air mass flow
Nor Farida Harun, David Tucker, Thomas A. Adams II
June 19, 2018 (v1)
Keywords: Cathode air mass flow, Cyber-physical simulations, Fuel cell gas turbine hybrid, Fuel composition changes, Open loop characterization, Solid Oxide Fuel Cells
Considering the limited turndown potential of gasification technologies, supplementing a fuel cell turbine hybrid power system with natural gas provides flexibility that could improve economic viability. The dynamic characterization of fuel composition transients is an essential first step in completing the system identification required for controls development. In this work, both open loop and closed loop transient responses of the fuel cell in a solid oxide fuel cell (SOFC) gas turbine (GT) hybrid system to fuel composition changes were experimentally investigated using a cyber-physical fuel cell system. A transition from methane lean syngas to methane rich gases with no turbine speed control was studied. The distributed performance of the fuel cell was analyzed in detail with temporal and spatial resolution across the cell.

Dramatic changes in fuel cell system post combustor thermal output or “thermal effluent” resulting from anode composition changes drove turbine transients th... [more]
Blackout! Classroom Edition
Jake Nease, Thomas A. Adams II
December 12, 2019 (v2)
Subject: Education
Keywords: Classroom Workshop, Electricity Grid, Energy Markets, Game Theory, Open Source, Video Game
Blackout! Is a classroom game (suitable for middle school and up to and including university students) which simulates open electricity markets. Up to eight players compete on the open market to build power plants, bid on sale prices, and deliver the most electricity to their customers. Demand changes each turn (one simulation hour) over the course of a day. The game helps to teach about the trade-offs between different kinds of power plants, such as cost (capital cost vs. operating cost), reliability (thermal vs. renewables), flexibilty (such as base-load vs. peaking power), and so on. The current version includes wind, solar, nuclear, coal, and natural gas based power plants. Also included in this submission are sample workshop materials (i.e. instructional slides) useful in a classroom setting. Please see also the linked academic research article discussing the statistical outcomes of using the game with middle and high school students.

An article in Chemical Engineering Educatio... [more]
Space-constrained purification of dimethyl ether through process intensification using semicontinuous dividing wall columns
Sarah E. Ballinger, Thomas A. Adams II
June 12, 2018 (v1)
Keywords: Aspen Plus, Dimethyl Ether, Dividing wall column, Mobile Plant, Plant-on-a-truck, Process Intensification, Semicontinuous Distillation, Simulation
In this work, a distillation system is designed to purify dimethyl ether (DME) from its reaction by-products in the conversion of flare gas into a useful energy product. The distillation equipment has a size constraint for easy transportation, making process intensification the best strategy to efficiently separate the mixture. The process intensification distillation techniques explored include the dividing wall column (DWC) and a novel semicontinuous dividing wall column (S-DWC). The DWC and the S-DWC both purify DME to fuel grade purity along with producing high purity waste streams. An economic comparison is made between the two systems. The DWC is a cheaper method of producing DME however the purity of methanol, a reaction intermediate, is not as high as the S-DWC. Overall, this research shows that it is possible to purify DME and its reaction by-products in a 40-foot distillation column at a cost that is competitive with Diesel.
Comparison of CO2 Capture Approaches for Fossil-Based Power Generation: Review and Meta-Study
Thomas A. Adams II, Leila Hoseinzade, Pranav Bhaswanth Madabhushi, Ikenna J. Okeke
June 19, 2018 (v2)
Keywords: Carbon Capture, Carbon Dioxide Sequestration, CO2 membrane, IGCC, oxyfuels, Post-combustion capture, Pre-combustion capture, Solid Oxide Fuel Cells
This work is a meta-study of CO2 capture processes for coal and natural gas power generation, including technologies such as post-combustion solvent-based carbon capture, the integrated gasification combined cycle process, oxyfuel combustion, membrane-based carbon capture processes, and solid oxide fuel cells. A literature survey of recent techno-economic studies was conducted, compiling relevant data on costs, efficiencies, and other performance metrics. The data were then converted in a consistent fashion to a common standard (such as a consistent net power output, country of construction, currency, base year of operation, and captured CO2 pressure) such that a meaningful and direct comparison of technologies can be made. The processes were compared against a standard status quo power plant without carbon capture to compute metrics such as cost of CO2 emissions avoided to identify the most promising designs and technologies to use for CO2 emissions abatement.
Modeling and simulation of an integrated steam reforming and nuclear heat system
Leila Hoseinzade, Thomas A. Adams II
June 12, 2018 (v1)
Keywords: Dynamic Modelling, Integrated Systems, Methane Reforming, Nuclear Heat, Simulation, Syngas
In this study, a dynamic and two-dimensional model for a steam methane reforming process integrated with nuclear heat production is developed. The model is based on first principles and considers the conservation of mass, momentum and energy within the system. The model is multi-scale, considering both bulk gas effects as well as spatial differences within the catalyst particles. Very few model parameters need to be fit based on the design specifications reported in the literature. The resulting model fits the reported design conditions of two separate pilot-scale studies (ranging from 0.4 to 10 MW heat transfer duty). A sensitivity analysis indicated that disturbances in the helium feed conditions significantly affect the system, but the overall system performance only changes slightly even for the large changes in the value of the most uncertain parameters.
Techno-economic comparison of Acetone-Butanol-Ethanol fermentation using various extractants
Giancarlo Dalle Ave, Thomas A. Adams II
June 12, 2018 (v1)
Keywords: Acetone, Butanol, Cost of CO2 Emissions Avoided, Ethanol, Extraction, Fermentation, Technoeconomic Analysis
This work compares various chemicals for use as extractants in second-generation Acetone-Butanol-Ethanol fermentation on economic and environmental bases. Both non-toxic and toxic extractants are considered in this study. The combinative extractive-distillation separation process was modelled using a combination of Microsoft Excel 2013, MATLAB 2015 and Aspen Plus v8.8. Separation trains were designed and optimized for each extractant to best take advantage of extractant properties. Upstream units considered in this analysis include: biomass (switchgrass) solids processing, biomass pre-treatment and saccharification, and fermentation. Downstream processes considered include utility generation and wastewater treatment. The cost of CO2 equivalent emissions avoided (CCA) was used as the metric to compare the environmental impact of each process as compared to conventional petroleum-based gasoline. The economic and environmental best extractant is shown to be 2-ethyl-hexanol with a minimum... [more]
Techno-economic comparison of Acetone-Butanol-Ethanol fermentation using various extractants
Giancarlo Dalle Ave, Thomas A. Adams II
June 12, 2018 (v1)
Keywords: Acetone, Butanol, Cost of CO2 Emissions Avoided, Ethanol, Extraction, Fermentation, Technoeconomic Analysis
This work compares various chemicals for use as extractants in second-generation Acetone-Butanol-Ethanol fermentation on economic and environmental bases. Both non-toxic and toxic extractants are considered in this study. The combinative extractive-distillation separation process was modelled using a combination of Microsoft Excel 2013, MATLAB 2015 and Aspen Plus v8.8. Separation trains were designed and optimized for each extractant to best take advantage of extractant properties. Upstream units considered in this analysis include: biomass (switchgrass) solids processing, biomass pre-treatment and saccharification, and fermentation. Downstream processes considered include utility generation and wastewater treatment. The cost of CO2 equivalent emissions avoided (CCA) was used as the metric to compare the environmental impact of each process as compared to conventional petroleum-based gasoline. The economic and environmental best extractant is shown to be 2-ethyl-hexanol with a minimum... [more]
Direct Steam Generation Concentrated Solar Power Plant with a Decalin/Naphthalene Thermochemical Storage System
Haoxiang Lai, Thomas A. Adams II
November 20, 2018 (v2)
This study presents the design and analysis of a new integrated direct steam generation (DSG) concentrated solar power (CSP) plant with a decalin/naphthalene thermochemical storage system. Model simulations were performed in accordance to historical hourly solar radiation data over a year, using a combination of Aspen Plus v10, MATLAB 2016b, and Microsoft Excel VBA. It was found that the proposed plant feasibly stored and discharged energy, based on the solar radiation and chemical storage availability, to maintain base-load power productions (250 MW or 120 MW) with an overall efficiency of 14.6%. The effectiveness of the designed storage system was found to be comparable to a molten salt storage system which is currently used in existing CSP plants. The proposed integrated DSG CSP plant with a decalin/naphthalene thermochemical storage system shows promise for being an alternative to existing CSP plants.
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