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Processes, Volume 1, Issue 2 (September 2013), Pages 30-237

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Research

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Open AccessArticle Density and Viscosity Measurement of Diesel Fuels at Combined High Pressure and Elevated Temperature
Processes 2013, 1(2), 30-48; doi:10.3390/pr1020030
Received: 20 May 2013 / Revised: 24 June 2013 / Accepted: 2 July 2013 / Published: 19 July 2013
Cited by 8 | PDF Full-text (398 KB) | HTML Full-text | XML Full-text
Abstract
We report the measurement of the viscosity and density of various diesel fuels, obtained from British refineries, at elevated pressures up to 500 MPa and temperatures in the range 298 K to 373 K. The measurement and prediction procedures of fluid properties [...] Read more.
We report the measurement of the viscosity and density of various diesel fuels, obtained from British refineries, at elevated pressures up to 500 MPa and temperatures in the range 298 K to 373 K. The measurement and prediction procedures of fluid properties under high pressure conditions is of increasing interest in many processes and systems including enhanced oil recovery, automotive engine fuel injection, braking, and hydraulic systems. Accurate data and understanding of the fluid characteristic in terms of pressure, volume and temperature is required particularly where the fluid is composed of a complex mixture or blend of aliphatic or aromatic hydrocarbons. In this study, high pressure viscosity data was obtained using a thermostatically-controlled falling sinker-type high pressure viscometer to provide reproducible and reliable viscosity data based on terminal velocity sinker fall times. This was supported with density measurements using a micro-pVT device. Both high-pressure devices were additionally capable of illustrating the freezing points of the hydrocarbon mixtures. This work has, thus, provided data that can extend the application of mixtures of commercially available fuels and to test the validity of available predictive density and viscosity models. This included a Tait-style equation for fluid compressibility prediction. For complex diesel fuel compositions, which have many unidentified components, the approach illustrates the need to apply appropriate correlations, which require accurate knowledge or prediction of thermodynamic properties. Full article
(This article belongs to the Special Issue Feature Papers) Print Edition available
Open AccessArticle Scale-Up Design Analysis and Modelling of Cobalt Oxide Silica Membrane Module for Hydrogen Processing
Processes 2013, 1(2), 49-66; doi:10.3390/pr1020049
Received: 24 May 2013 / Revised: 28 June 2013 / Accepted: 26 July 2013 / Published: 5 August 2013
Cited by 3 | PDF Full-text (796 KB) | HTML Full-text | XML Full-text
Abstract
This work shows the application of a validated mathematical model for gas permeation at high temperatures focusing on demonstrated scale-up design for H2 processing. The model considered the driving force variation with spatial coordinates and the mass transfer across the molecular [...] Read more.
This work shows the application of a validated mathematical model for gas permeation at high temperatures focusing on demonstrated scale-up design for H2 processing. The model considered the driving force variation with spatial coordinates and the mass transfer across the molecular sieve cobalt oxide silica membrane to predict the separation performance. The model was used to study the process of H2 separation at 500 °C in single and multi-tube membrane modules. Parameters of interest included the H2 purity in the permeate stream, H2 recovery and H2 yield as a function of the membrane length, number of tubes in a membrane module, space velocity and H2 feed molar fraction. For a single tubular membrane, increasing the length of a membrane tube led to higher H2 yield and H2 recovery, owing to the increase of the membrane area. However, the H2 purity decreased as H2 fraction was depleted, thus reducing the driving force for H2 permeation. By keeping the membrane length constant in a multi-tube arrangement, the H2 yield and H2 recovery increase was attributed to the higher membrane area, but the H2 purity was again compromised. Increasing the space velocity avoided the reduction of H2 purity and still delivered higher H2 yield and H2 recovery than in a single membrane arrangement. Essentially, if the membrane surface is too large, the driving force becomes lower at the expense of H2 purity. In this case, the membrane module is over designed. Hence, maintaining a driving force is of utmost importance to deliver the functionality of process separation. Full article
(This article belongs to the Special Issue Feature Papers) Print Edition available
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Open AccessArticle Dynamic Modeling for the Design and Cyclic Operation of an Atomic Layer Deposition (ALD) Reactor
Processes 2013, 1(2), 128-152; doi:10.3390/pr1020128
Received: 8 June 2013 / Revised: 2 August 2013 / Accepted: 7 August 2013 / Published: 19 August 2013
Cited by 8 | PDF Full-text (516 KB) | HTML Full-text | XML Full-text
Abstract
A laboratory-scale atomic layer deposition (ALD) reactor system model is derived for alumina deposition using trimethylaluminum and water as precursors. Model components describing the precursor thermophysical properties, reactor-scale gas-phase dynamics and surface reaction kinetics derived from absolute reaction rate theory are integrated [...] Read more.
A laboratory-scale atomic layer deposition (ALD) reactor system model is derived for alumina deposition using trimethylaluminum and water as precursors. Model components describing the precursor thermophysical properties, reactor-scale gas-phase dynamics and surface reaction kinetics derived from absolute reaction rate theory are integrated to simulate the complete reactor system. Limit-cycle solutions defining continuous cyclic ALD reactor operation are computed with a fixed point algorithm based on collocation discretization in time, resulting in an unambiguous definition of film growth-per-cycle (gpc). A key finding of this study is that unintended chemical vapor deposition conditions can mask regions of operation that would otherwise correspond to ideal saturating ALD operation. The use of the simulator for assisting in process design decisions is presented. Full article
(This article belongs to the Special Issue Feature Papers) Print Edition available
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Open AccessArticle Photochemical Patterning of Ionically Cross-Linked Hydrogels
Processes 2013, 1(2), 153-166; doi:10.3390/pr1020153
Received: 5 June 2013 / Revised: 24 July 2013 / Accepted: 15 August 2013 / Published: 22 August 2013
Cited by 7 | PDF Full-text (421 KB) | HTML Full-text | XML Full-text
Abstract
Iron(III) cross-linked alginate hydrogel incorporating sodium lactate undergoes photoinduced degradation, thus serving as a biocompatible positive photoresist suitable for photochemical patterning. Alternatively, surface etching of iron(III) cross-linked hydrogel contacting lactic acid solution can be used for controlling the thickness of the photochemical [...] Read more.
Iron(III) cross-linked alginate hydrogel incorporating sodium lactate undergoes photoinduced degradation, thus serving as a biocompatible positive photoresist suitable for photochemical patterning. Alternatively, surface etching of iron(III) cross-linked hydrogel contacting lactic acid solution can be used for controlling the thickness of the photochemical pattering. Due to biocompatibility, both of these approaches appear potentially useful for advanced manipulation with cell cultures including growing cells on the surface or entrapping them within the hydrogel. Full article
(This article belongs to the Special Issue Feature Papers) Print Edition available
Open AccessArticle Systematic Sustainable Process Design and Analysis of Biodiesel Processes
Processes 2013, 1(2), 167-202; doi:10.3390/pr1020167
Received: 5 June 2013 / Revised: 27 July 2013 / Accepted: 13 August 2013 / Published: 3 September 2013
Cited by 7 | PDF Full-text (1193 KB) | HTML Full-text | XML Full-text
Abstract
Biodiesel is a promising fuel alternative compared to traditional diesel obtained from conventional sources such as fossil fuel. Many flowsheet alternatives exist for the production of biodiesel and therefore it is necessary to evaluate these alternatives using defined criteria and also from [...] Read more.
Biodiesel is a promising fuel alternative compared to traditional diesel obtained from conventional sources such as fossil fuel. Many flowsheet alternatives exist for the production of biodiesel and therefore it is necessary to evaluate these alternatives using defined criteria and also from process intensification opportunities. This work focuses on three main aspects that have been incorporated into a systematic computer-aided framework for sustainable process design. First, the creation of a generic superstructure, which consists of all possible process alternatives based on available technology. Second, the evaluation of this superstructure for systematic screening to obtain an appropriate base case design. This is done by first reducing the search space using a sustainability analysis, which provides key indicators for process bottlenecks of different flowsheet configurations and then by further reducing the search space by using economic evaluation and life cycle assessment. Third, the determination of sustainable design with/without process intensification using a phenomena-based synthesis/design method. A detailed step by step application of the framework is highlighted through a biodiesel production case study. Full article
(This article belongs to the Special Issue Feature Papers) Print Edition available
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Open AccessArticle A Real-Time Optimization Framework for the Iterative Controller Tuning Problem
Processes 2013, 1(2), 203-237; doi:10.3390/pr1020203
Received: 7 June 2013 / Revised: 1 August 2013 / Accepted: 27 August 2013 / Published: 12 September 2013
Cited by 4 | PDF Full-text (932 KB) | HTML Full-text | XML Full-text
Abstract
We investigate the general iterative controller tuning (ICT) problem, where the task is to find a set of controller parameters that optimize some user-defined performance metric when the same control task is to be carried out repeatedly. Following a repeatability assumption on [...] Read more.
We investigate the general iterative controller tuning (ICT) problem, where the task is to find a set of controller parameters that optimize some user-defined performance metric when the same control task is to be carried out repeatedly. Following a repeatability assumption on the system, we show that the ICT problem may be formulated as a real-time optimization (RTO) problem, thus allowing for the ICT problem to be solved in the RTO framework, which is both very flexible and comes with strong theoretical guarantees. In particular, we propose the use of a recently released RTO solver and outline a simple procedure for how this solver may be configured to solve ICT problems. The effectiveness of the proposed method is illustrated by successfully applying it to four case studies—two experimental and two simulated—that cover the tuning of model-predictive, general fixed-order and PID controllers, as well as a system of controllers working in parallel. Full article
(This article belongs to the Special Issue Feature Papers) Print Edition available

Review

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Open AccessReview Modeling of Particulate Processes for the Continuous Manufacture of Solid-Based Pharmaceutical Dosage Forms
Processes 2013, 1(2), 67-127; doi:10.3390/pr1020067
Received: 31 May 2013 / Revised: 11 July 2013 / Accepted: 26 July 2013 / Published: 19 August 2013
Cited by 8 | PDF Full-text (2395 KB) | HTML Full-text | XML Full-text
Abstract
The objective of this work is to present a review of computational tools and models for pharmaceutical processes, specifically those for the continuous manufacture of solid dosage forms. Relevant mathematical methods and simulation techniques are discussed, as is the development of process [...] Read more.
The objective of this work is to present a review of computational tools and models for pharmaceutical processes, specifically those for the continuous manufacture of solid dosage forms. Relevant mathematical methods and simulation techniques are discussed, as is the development of process models for solids-handling unit operations. Continuous processing is of particular interest in the current study because it has the potential to improve the efficiency and robustness of pharmaceutical manufacturing processes. Full article
(This article belongs to the Special Issue Feature Papers) Print Edition available

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