Search

Insights from the venerable Trouton's Rule have been used to guide the development of an applied-thermodynamic method for the estimation, correlation, and evaluation of pure-component vapor pressure. Trouton's Rule very simply and succinctly states that the entropy of vaporization of fluids at their normal boiling point is a constant (≈10.5 times the gas constant). Detailed evaluation of the data for many families of chemical compounds reveals the subtle patterns of departures from the rule, and facilitates the development of a useful new correlation. Several examples are presented to demonstrate the value of the new correlation to estimate, correlate, extrapolate, and evaluate vapor-pressure data, and to understand the patterns of vapor-pressure behavior. The methodology provides a guide for the development of thermodynamic correlations, and the resulting correlations are expected to be useful for the practice of applied thermodynamics. [ABSTRACT FROM AUTHOR]

Intermediate components tend to accumulate near the middle of a distillation column in many chemical and petroleum separations. Their accumulation may lead to off-spec products, corrosion, plugging, or periodic cycling. The most common method of removing these intermediate components is by taking them out in one or more side draws. The addition of such side draws may not go far enough to achieve the desired product specs. If the side-draw approach fails, the expensive addition of additional towers may be required. The question of whether a side draw is sufficient to remove the accumulating intermediate components or whether additional columns are needed depends on the relative volatilities of the intermediate components at tower conditions. Often, there is a high degree of uncertainty in the model used for correlation of the phase equilibrium of these components. The Margules Uncertainty Analysis method is valuable in analyzing these situations and in guiding engineers to the rational solution. The case analyzed here is an acetonitrile + water separation tower with t-crotonaldehyde and propionitrile as the intermediate components. There are uncertainties in the correlation of the volatilities of these intermediate components in this system. In light of these uncertainties, our analysis addresses the question of whether the tight product specs can be achieved in one tower with a side draw or whether more than one tower is needed. The analysis shows that depending on the product specs and the tolerance for a high reflux ratio, there would be situations where one can be certain that one tower will work, while in other cases more than one tower is needed to ensure achievement of the required product specs. The analysis enables quantification of the risk of the single-column solution--specifically the quantification of confidence limits. [ABSTRACT FROM AUTHOR]

This paper continues application of the Margules-based phase-equilibrium uncertainty method to systems with weak and strong deviations from Raoult's law. The method was developed in order to provide practicing engineers with an intuitive and easily applicable method to quantitatively relate process-design uncertainties to uncertainties in correlated physical properties, specifically nonideal phase equilibrium. The methodology has been used in several case studies: (1) a propylene + propane superfractionator for which small changes in correlated relative volatilities have a large effect on the design of the distillation column; (2) a dehexanizer column that separates a mixture containing many close-boiling hydrocarbon components; (3) a distillation train that separates the acetone + chloroform + benzene ternary mixture, which contains one maximum-boiling azeotrope; and (4) separation of the water + 1-butanol binary mixture, which has a heterogeneous azeotrope. The present work applies the methodology to the purification of ethyl acetate from a ternary mixture with ethanol and water. This purification step occurs in the production of ethyl acetate via esterification of acetic acid with ethanol, and the process design is complex because the ethyl acetate + ethanol + water ternary mixture exhibits a liquid-liquid region and four azeotropes. [ABSTRACT FROM AUTHOR]

Aqueous amines, as the most mature carbon capture technology, are subject to high energy and cost penalties due to the large water content in their formulations. Emerging technologies are in demand to enable a transition to a low-carbon global economy. However, rigorous process modeling and techno-economic analyses are limited for emerging carbon capture technologies. Here, four CO 2 -Binding Organic Liquids (CO 2 BOLs), all water-lean solvents were presented as promising options towards energy-effective and low-cost carbon capture from point sources. Rigorous solvent property and process models were developed in Aspen Plus for a coal-fired power plant with CO 2 BOL-based carbon capture unit. Techno-economic analyses were conducted in 2018 US pricing basis. The results suggest that water-lean formulations can minimize water condensation and vaporization, leading to a 36% energy saving compared with aqueous amines. Indeed, these CO 2 BOLs can capture up to 97–99% CO 2 from coal fired plant. The estimated carbon capture cost is about $40/tonne CO 2 at 90–97% carbon capture rate, about 12–23% less expensive than the conventional aqueous amine technology. The comparison between these CO 2 BOLs showed that in addition to vapor liquid equilibrium and kinetics (key properties for aqueous solvents), viscosity, volatility, and hydrophobicity, also have strong impacts on the performance of water-lean solvents. The methods presented in this work can be used to evaluate other emerging carbon capture technologies, while the results linking costs and performance of carbon capture solvents with their properties. Further, this work identifies research directions and targets for further reductions in total costs of capture from either cost or energy perspectives for these leading water-lean solvents. [Display omitted] • Developed process models for four water-lean point-source carbon capture solvents. • Conducted techno-economic comparison and provided cost breakdowns for different solvents. • Water-lean solvents can enable up to 36% energy saving for carbon capture. • Water-lean solvents can enable about 12–23% reduction in carbon capture cost. [ABSTRACT FROM AUTHOR]

This paper extends application of the Margules-based phase-equilibrium uncertainty method to a system exhibiting a heterogeneous azeotrope. The author developed the method in order to provide practicing engineers with an intuitive and easy-to-apply procedure to quantitatively relate process-design uncertainties to uncertainties in correlated physical properties, specifically nonideal phase equilibrium. The methodology was first applied to two case studies(1) a propylene-propane superfractionator for which small changes in correlated relative volatilities have a large effect on the design of the distillation column; and (2) a dehexanizer column that separates a mixture containing many close-boiling hydrocarbon componentsand demonstrated that the proposed method provides quantitative insight into the effect of property uncertainties for both these diverse process designs and helps to quantify the safety factors that need to be imposed upon the design. In a subsequent study, the methodology was applied to a distillation train that separates the acetone-chloroform-benzene ternary mixture, which contains one maximum-boiling azeotrope, and showed that the approach quantifies the effect of property uncertainties on utility consumption and also identifies limits on operating variables (specifically minimum recycle flow). In this paper, the Margules perturbation method is applied to the separation of the water + 1-butanol binary mixture. The application is complex because this binary exhibits liquid-liquid equilibrium and forms a minimum-boiling azeotrope, and the typical separation scheme includes a decanter as well as two distillation columns. Further, the chosen activity-coefficient model is unable to correlate the data within measurement uncertainty. Nevertheless, the methodology is demonstrated to provide useful quantitative estimates of the design uncertainty resulting from the combined measurement/model phase-equilibrium uncertainty. [ABSTRACT FROM AUTHOR]

The family of Gibbs-Helmholtz equations connect phase and chemical equilibrium with enthalpy and volume. This family of equations is one of the most useful--yet unappreciated and poorly understood--mathematical relations in chemical thermodynamics. This paper rigorously derives several variants of the Gibbs-Helmholtz equation that are applicable to chemical process technology, and evaluates their use for educational and industrial purposes. The focus of the contribution is the manner in which fundamental chemical thermodynamics contributes to the industrial practice of process technology. Some rigorous thermodynamic equations are more useful than others in particular applications of chemical process technology. The paper also studies the early historical development of the Gibbs-Helmholtz equation. [ABSTRACT FROM AUTHOR]

It is widely recognized by experts that the computer-based design of chemical processes depends strongly on the correlated thermodynamic and transport properties, and that the effect of the property uncertainties should be accounted for in the design. The most significant source of property uncertainties on process design comes from the correlations of mixture phase equilibrium. Many approaches to uncertainty analysis have been proposed, but uncertainty analysis is not a routine element of today's industrial practice, mainly because education and awareness are lacking, and the proposed methods are difficult to apply. In order to help rectify the situation, the author developed an intuitive and easy-to-apply phase-equilibrium (specifically, activity coefficient) perturbation method based upon treating the mixture, for the purpose of uncertainty perturbation, as a set of pseudobinaries described by the Margules equation. The approach was applied to two case studies – (1) a propylene-propane superfractionator for which small changes in correlated relative volatilities have a large effect on the design of the distillation column; and (2) a dehexanizer column that separates a mixture containing many close-boiling components – and demonstrated that the proposed methodology provides quantitative insight into the effect of property uncertainties, and helps to estimate the safety factors that should be imposed upon the design. In this paper the Margules perturbation method is applied to the “textbook” separation of an acetone–chloroform–benzene ternary mixture; this case study was proposed in 1996 by Westerberg and Wahnshafft, and was previously studied by Parodi and Campanella. The approach of Parodi and Campanella used different levels of data fitting to identify uncertainties, while the present methodology is to obtain the best fit of the data, and then apply uncertainties based upon estimated combined model uncertainties, which includes experimental uncertainties and any model inadequacies. The purpose of this paper is to further study whether the Margules approach to mixture uncertainty offers insight, and is a useful technique to perform uncertainty analysis. [ABSTRACT FROM AUTHOR]

We have improved the estimation of the solubility of hydrogen and carbon monoxide in a range of linear alcohols and alkanes (between C 4 and C 32 ) by using the method of molecular dynamics (MD) together with experimental data and traditional thermodynamics analysis. The goal of the study was to use a fundamental molecular-based method, after validation, to fill gaps in data in current literature, especially for systems considered challenging for traditional measurement and estimation methods. The simulation system used semi-permeable membranes to mimic actual experimental studies of gas solubility. Our combined analysis of both data and simulation results demonstrated that for higher carbon numbers (C N ) both CO and H 2 individually have similar Henry’s constant values in the two solvents, with H 2 values being roughly 50% higher in both solvents. The data and simulation results were also used to estimate limiting values of the mass-based Henry’s constant for H 2 and CO in the higher alcohols (large C N ). [ABSTRACT FROM AUTHOR]

It is current practice to represent and analyze vapor-liquid equilibrium data through the use of state conditions (temperature and pressure) and phase compositions. However, these representations do not reveal and identify the accuracy of the data for important purposes, such as separation by distillation and this is particularly a problem for the important low-concentration regions. The intent of this editorial is to present the guidelines of the Journal of Chemical & Engineering Data that vapor-liquid equilibrium data should be evaluated through the use of charts and related analyses that bring to light the low-concentration regions, for example, K-values and relative volatilities. [ABSTRACT FROM AUTHOR]

Itis widely recognized by experts that the computer-based designof chemical processes depends strongly on the correlated thermodynamicand transport properties, and the effect of property uncertaintiesshould be incorporated into the design. The most significant sourceof property uncertainties on process design is from the correlationsof phase equilibrium. Many approaches have been proposed, but uncertaintyanalysis is not a routine component of today’s industrial practice,mainly because education and awareness is lacking, and the proposedmethods are difficult to apply. The purpose of this paper is to reporta new approach to uncertainty analysis that is intuitively appealingand easy to apply in process simulation. The proposed approach focuseson activity coefficients and is based upon the simplification that,for the purpose of perturbation, the liquid mixture can be treatedas a set of pseudobinaries described by the Margules equation. Theresulting perturbation in the activity coefficient of component igoes to zero when its mole fraction approaches unity,and also is relatively small when its estimated activity coefficientis close to unity (i.e., near-ideal systems are likely to be modeledmore accurately than highly nonideal systems). In practice, the proposeduncertainty analysis is performed by varying a single parameter foreach component in the mixture. The utility of the proposed uncertaintymethod is demonstrated by application to two problems: (1) a propylene–propanesuperfractionator for which small changes in correlated relative volatilitieshave a large effect on the design of the distillation column, and(2) a dehexanizer column that separates a mixture containing manyclose-boiling components. It is demonstrated that the proposed analysisprovides quantitative insight into the effect of property uncertaintiesand helps to quantify the safety factors that need to be imposed uponthe design. While the proposed method is applied to activity-coefficientmodels, the same idea is applicable to other models such as equationsof state. [ABSTRACT FROM AUTHOR]

Abstract: There is intense ongoing worldwide research to develop improved solvents and processes for CO2 capture from flue gas. The number of publications was almost 1000 in 2011, and may be expected to exceed 10,000 by 2020 if exponential extrapolation of the number of past publications is applicable. Applied thermodynamics is a valuable tool to make sense of this vast body of research, and we present three examples of its contribution to CO2-capture process technology. Aqueous-ammonia processes have been proposed as energy-efficient alternatives to traditional alkanolamine process, and early proponents claimed that a significant advantage of the technology is that the CO2 enthalpy of solution is exceptionally low, about −27kJ/mol. A rigorous thermodynamic model with correct speciation estimated that the CO2 heat of solution is closer to about −65kJ/mol, a number that was later confirmed by calorimetric measurements. The thermodynamic model enabled realistic analysis of the chilled-ammonia process, and these results have been supported by subsequent studies by other researchers. Further work on this subject established the rigorous and complete form of the Gibbs–Helmholtz equation, and demonstrated its value in evaluating the consistency between vapor–liquid equilibrium and calorimetric data. Theoretical and experimental studies have been used to find the best solvent for CO2 capture. Some researchers have assumed that the goal is seek solvents with high CO2 capacity and a low enthalpy of solution. This notion was tested by inventing solvents with various properties, the only restriction being that the properties must be thermodynamically consistent. The results have provided insight into the interplay between CO2 absorption and the heat of regeneration (through the Gibbs–Helmholtz equation), and reveal subtle characteristics that may guide the development of future solvents. A promising step-out technology for CO2 capture is “CO2-binding liquids with polarity-swing-assisted regeneration.” Reliable analysis and design of this complex technology requires a thermodynamic model that describes the chemical absorption (i.e., speciation) as well as vapor–liquid–liquid equilibrium. The initial thermodynamic model has enabled useful projections of process performance. The model limitations and the need for future improvements are also discussed. [Copyright &y& Elsevier]

The Gibbs–Helmholtz (G-H) equation connects vapor–liquidequilibrium (VLE) and calorimetric data. If experimental measurementsfor the heat of solution are not available, they may be estimatedthrough the G-H equation. Further, if both VLE and heat-of-solutiondata are available, their mutual thermodynamic consistency can beevaluated through the G-H equation, to develop the most accurate andreliable model. This kind of analysis is particularly useful for chemical-absorptionsystems, such as the capture of CO2using aqueous solutionsof amines, where regeneration energies are significant. In this work,the G-H equation is derived to unambiguously relate the commonly usedform to the rigorous and general form, including for systems wherephase equilibrium is accompanied by chemical reactions in any phase.The effect of approximations and the range of applicability of thecommon G-H equation are first applied to data generated for a simpleVLE system by an equation of state, with different reliability foundfor the vapor and liquid phases. Next, consistency is evaluated formany VLE and calorimetric data for CO2absorption in aqueousMEA (monoethanolamine). It is shown that some VLE and/or calorimetricdata sets are likely to be in error and that the experimental VLEand CO2heat of solution at the highest temperatures arecurrently uncertain. [ABSTRACT FROM AUTHOR]

Experimental data have served two critical roles in chemical process technology: (1) by providing the definitive quantitative basis to evaluate competing processes, to optimize designs, and ultimately to guarantee plant performance; and (2) by guiding the form and structure of applied-thermodynamics correlations. This paper first presents two representative applications to highlight the role of thermodynamic and transport properties in chemical process technology: ammonia recovery from syngas using water as solvent, and design of a caustic-guard system to eliminate small residual concentrations of SO2 from a gas stream. These applications illustrate the first role of experimental data. The paper next studies the second role by examining the historical contribution of experimental data-over two centuries— in guiding the development of key concepts and correlations, such as Henry's law (1802), group-contribution methods (Kopp, 1842), Raoult's law (1878), second-virial-coefficient correlation (Berthelot, 1907), surface-tension correlation (Macleod, 1923), the use of one property to estimate another (Othmer, 1940), cubic equations of state (Redlich and Kwong, 1949), electrolyte systems (van Krevelen, 1949), acentric factor (Pitzer, 1955), and highly accurate equations of state (Span and Wagner, 2003). The analysis reveals that careful, accurate, and wide-ranging experimental data have identified the patterns of the underlying phenomena. [ABSTRACT FROM AUTHOR]

Abstract: Examples are used to illuminate ways in which applied thermodynamics is being successfully deployed in chemical technology and the challenges that need to be overcome. Nitric-acid plant modeling was very difficult two decades ago because of the complexity of the thermodynamic properties and the need to describe kinetic and mass-transfer limitations in the process equipment. This complex process and other similar processes are routinely modeled today thanks largely to advances in applied thermodynamics. In fact, applied thermodynamics is an established cornerstone of chemical engineering. Excel is an effective tool for custom applications and teaching since most scientists and engineers use it regularly. We demonstrate that the Excel add-in for Aspen Properties facilitates the creation of useful custom applications (e.g., analysis and understanding of flammability limits and analysis of pressure variation in batch reactors) – usually within a few hours – enabling big improvements in education and wide deployment of chemical technology. Modern software enables modeling of complex processes – and highlights the challenging areas. This point is elucidated through a promising process for hydrogen production via thermochemical water splitting: the sulfur iodine cycle. The sulfuric acid decomposition section of this process can be simulated accurately, but other sections (acid generation and hydrogen iodide decomposition) illustrate the difficulty of modeling phase behavior, particularly liquid-phase immiscibility, in complex electrolyte systems. The difficulties arise from model inadequacies as well as a lack of fundamental data. However, these difficulties will likely be overcome soon mainly through new data, but also through advance in molecular-thermodynamic models. Property estimation and data regression have progressed as independent silos for the development of applied thermodynamic models. We discuss the seminal contribution of a recent proposal that combines a segment-based NRTL model with a few (3–4) solubility measurements for a target solute to develop a predictive method for the solubility of this solute in most solvents and solvent mixtures of interest. This proposal creates an effective and efficient work process for solvent selection in the pharmaceutical and specialty chemical industries. The paper concludes by summarizing challenges that remain for the future use of applied thermodynamics in chemical technology. [Copyright &y& Elsevier]

Thermodynamic properties have always played essential roles in the engineering of chemical products and in the processes that manufacture them. Further, contemporary and future chemical technologies depend more than ever on property model formulation and application. This work explores how properties are utilized in process and product engineering, including opportunities and constraints of current property models, the current status of data availability and needs, and the interplay of data and models. Several case studies are given to illustrate underlying concepts, strategies for development, and methods of application to some industrial systems. [ABSTRACT FROM AUTHOR]

Scientific projects frequently involve measurements of thermophysical, thermochemical, and other related properties of chemical compounds and materials. These measured property data have significant potential value for the scientific community, but incomplete and inaccurate reporting often hampers their utilization. The present IUPAC Technical Report summarizes the needs of chemical engineers and researchers as consumers of these data and shows how publishing practices can improve information transfer. In the Report, general principles of Good Reporting Practice are developed together with examples illustrating typical cases of reporting issues. Adoption of these principles will improve the quality, reproducibility, and usefulness of experimental data, bring a better level of consistency to results, and increase the efficiency and impact of research. Closely related to Good Reporting Practice, basic elements of Good Research Practice are also introduced with a goal to reduce the number of ambiguities and unresolved problems within the thermophysical property data domain. [ABSTRACT FROM AUTHOR]