Vapour-liquid equilibrium of propanoic acid+water at 423.2, 453.2 and 483.2K from 1.87 to 19.38bar. Experimental and modelling with PR, CPA, PC-SAFT and PCP-SAFT

Vapour–liquid equilibrium data were measured for the propanoic acid + water system at 423.2, 453.2 and 483.2 K from 1.87 to 19.38 bar over the entire range of concentrations. An experimental apparatus based on the static–analytical method with sampling of both phases was used with quantitative analysis by GC. The system is highly non-ideal showing azeotropic behaviour. The Peng–Robinson (PR), the cubic plus association (CPA), the perturbed chain statistical associating fluid theory (PC-SAFT) and the PC-polar-SAFT (PCP-SAFT) equations of state modelled the data. Two association sites were assumed for both compounds. A single–binary interaction parameter (kij ) was used in all models, and predictive (kij=0) and correlative (View the MathML source) capabilities were assessed. Available data at 313.1, 343.2 and 373.1 K from the open literature were included in the analysis. PCP-SAFT presented higher predictive and correlative capabilities over the entire temperature range. PC-SAFT in predictive mode was not able to represent the azeotropic behaviour but resulted in the second best correlations. CPA presented a satisfactory balance between the two modes. PR predictions were rather poor but correlations were better than those of CPA, at the expense of a larger kij

Modeling of asphaltene precipitation from n-alkane diluted heavy oils and bitumens using the PC-SAFT equation of state

In this work, the PC-SAFT equation of state was applied to the modeling of asphaltene precipitation from n-alkane diluted heavy oils and bitumens. Liquid-liquid equilibrium was assumed between a dense liquid phase (asphaltene-rich phase) and a light liquid phase. The liquid-liquid equilibrium calculation, in which only asphaltenes were allowed to partition to the dense phase, was performed using an efficient method with Michelsen’s stability test. The bisection or Newton-Raphson method was used to improve convergence. Experimental information of the heavy oils and bitumens, characterized in terms of solubility fractions (saturates, aromatics, resins, and asphaltenes), was taken from the literature. Asphaltenes were divided into fractions of different molar masses using a gamma distribution function. Predictions of the PC-SAFT equation of state using linear correlations of the binary interaction parameters between asphaltene subfractions and the n-alkane were compared with the measured onset of precipitation and the amount of precipitated asphaltene (fractional yield) of the heavy oils and bitumens diluted with n-alkanes. Results of the comparison showed a satisfactory agreement between the experimental data and the calculated values with the PC-SAFT equation

Effects of site dilution on the magnetic properties of geometrically frustrated antiferromagnets

The effect of site dilution by non magnetic impurities on the susceptibility of geometrically frustrated antiferromagnets (kagome and pyrochlore lattices) is discussed in the framework of the Generalized Constant Coupling model, for both classical and quantum Heisenberg spins. For the classical diluted pyrochlore lattice, excellent agreement is found when compared with Monte Carlo data. Results for the quantum case are also presented and discussed.Comment: 5 pages, 3 figure

Proper motions of the HH1 jet

We describe a new method for determining proper motions of extended objects, and a pipeline developed for the application of this method. We then apply this method to an analysis of four epochs of [S~II] HST images of the HH~1 jet (covering a period of $\sim 20$~yr). We determine the proper motions of the knots along the jet, and make a reconstruction of the past ejection velocity time-variability (assuming ballistic knot motions). This reconstruction shows an "acceleration" of the ejection velocities of the jet knots, with higher velocities at more recent times. This acceleration will result in an eventual merging of the knots in $\sim 450$~yr and at a distance of $\sim 80"$ from the outflow source, close to the present-day position of HH~1.Comment: 12 pages, 8 figure

Critical behavior of 2 and 3 dimensional ferro- and antiferromagnetic spin ice systems in the framework of the Effective Field Renormalization Group technique

In this work we generalize and subsequently apply the Effective Field Renormalization Group technique to the problem of ferro- and antiferromagnetically coupled Ising spins with local anisotropy axes in geometrically frustrated geometries (kagome and pyrochlore lattices). In this framework, we calculate the various ground states of these systems and the corresponding critical points. Excellent agreement is found with exact and Monte Carlo results. The effects of frustration are discussed. As pointed out by other authors, it turns out that the spin ice model can be exactly mapped to the standard Ising model but with effective interactions of the opposite sign to those in the original Hamiltonian. Therefore, the ferromagnetic spin ice is frustrated, and does not order. Antiferromagnetic spin ice (in both 2 and 3 dimensions), is found to undergo a transition to a long range ordered state. The thermal and magnetic critical exponents for this transition are calculated. It is found that the thermal exponent is that of the Ising universality class, whereas the magnetic critical exponent is different, as expected from the fact that the Zeeman term has a different symmetry in these systems. In addition, the recently introduced Generalized Constant Coupling method is also applied to the calculation of the critical points and ground state configurations. Again, a very good agreement is found with both exact, Monte Carlo, and renormalization group calculations for the critical points. Incidentally, we show that the generalized constant coupling approach can be regarded as the lowest order limit of the EFRG technique, in which correlations outside a frustrated unit are neglected, and scaling is substituted by strict equality of the thermodynamic quantities.Comment: 28 pages, 9 figures, RevTeX 4 Some minor changes in the conclussions. One reference adde

Multicriteria analysis for retrofitting of natural gas melting and heating furnaces for sustainable manufacturing and industry 4.0

Different retrofitting measures can be implemented at different levels of the industrial furnace, such as refractory layers, energy recovery solutions, new burners and fuel types, and monitoring and control systems. However, there is a high level of uncertainty about the possible implications of integrating new technologies, not only in the furnace but also on the upstream and downstream processes. In this regard, there is a lack of holistic approaches to design the optimal system configurations under a multicriteria perspective, especially when innovative technologies and multi-sectorial processes are involved. The present work proposes a holistic approach to natural gas melting and heating furnaces in energy-intensive industries. A multicriteria analysis, based on criteria and subcriteria, is applied to select the most profitable retrofitting solution using the analytic hierarchy process and stakeholder expertise. The methodology is based on technical indicators, i.e., life cycle assessment, life cycle cost, and thermoeconomic analysis, for evaluating the current state of existing natural gas furnaces. Once the current state is characterized, the methodology determines the potential of efficiency improvement, environmental impact reduction, and cost-savings caused mainly by the implementation of new retrofitting solutions including new refractories, new burner concepts (co-firing), and innovative energy recovery solutions based on phase change materials. Therefore, this methodology can be considered as the first stage that guarantees technical, environmental, and economic feasibility in evaluating the effects of new technologies on the overall system performance