3,997 research outputs found
Extending Batch Extractive Distillation Thermodynamic Feasibility Insights to Continuous for Class 1.0-2 Case A
The feasibility of batch and continuous extractive distillation analysis for the separation azeotropic mixtures is addressed. Based on batch feasibility knowledge, batch and continuous separation feasibility is studied under reflux ratio and entrainer flow-rate for a working example ternary system acetone-chloroform-benzene, which belonging to the 1.0-2 class case (a). Possible feasible regions are determined by finding the feasible points based on continuous methodology, they show minimum and maximum feed ratio as a function of the reflux, and a lower bound for the reflux ratio. Later on, simulations verified the feasibility of calculating results based on theoretical methodolog
From batch to continuous extractive distillation using thermodynamic insight: class 1.0-2 case B
A systematic feasibility analysis is presented for the separation azeotropic mixtures by batch and continuous extractive distillation. Based on batch feasibility knowledge, batch and continuous separation feasibility is studied under reflux ratio and entrainer flow-rate for the ternary system chloroform-vinyl acetate-butyl acetate, which belongs to the class 1.0-2 separating maximum boiling temperature azeotropes using a heavy entrainer. How information on feasibility of batch mode could be extended to the feasibility of continuous mode is then studied, possible feasible regions are determined by finding the feasible points based on continuous methodology, they show minimum and maximum feed ratio as a function of the reflux, and a lower bound for the reflux ratio. Results are validated by simulation
Extractive distillation: recent advances in operation strategies
Extractive distillation is one of the efficient techniques for separating azeotropic and low-relativevolatility mixtures in various chemical industries. This paper first provides an overview of thermodynamic insight covering residue curve map analysis, the application of univolatility and unidistribution curves, and thermodynamic feasibility study. The pinch-point analysis method combining bifurcation shortcut presents another branch of study, and several achievements have been realized by the identification of possible product cut under the following key parameters: reflux ratio, reboil ratio, and entrainer-feed flow rate ratio. Process operation policies and strategy concerning batch extractive distillation processes are summarized in four operation steps. Several configurations and technological alternatives can be used when extractive distillation processes take place in a continuous or batch column, depending on the strategy selected for the recycle streams and for the main azeotropic feeds
Impact of surface roughness on diffusion of confined fluids
Using event-driven molecular dynamics simulations, we quantify how the self
diffusivity of confined hard-sphere fluids depends on the nature of the
confining boundaries. We explore systems with featureless confining boundaries
that treat particle-boundary collisions in different ways and also various
types of physically (i.e., geometrically) rough boundaries. We show that, for
moderately dense fluids, the ratio of the self diffusivity of a rough wall
system to that of an appropriate smooth-wall reference system is a linear
function of the reciprocal wall separation, with the slope depending on the
nature of the roughness. We also discuss some simple practical ways to use this
information to predict confined hard-sphere fluid behavior in different
rough-wall systems
Composition and concentration anomalies for structure and dynamics of Gaussian-core mixtures
We report molecular dynamics simulation results for two-component fluid
mixtures of Gaussian-core particles, focusing on how tracer diffusivities and
static pair correlations depend on temperature, particle concentration, and
composition. At low particle concentrations, these systems behave like simple
atomic mixtures. However, for intermediate concentrations, the single-particle
dynamics of the two species largely decouple, giving rise to the following
anomalous trends. Increasing either the concentration of the fluid (at fixed
composition) or the mole fraction of the larger particles (at fixed particle
concentration) enhances the tracer diffusivity of the larger particles, but
decreases that of the smaller particles. In fact, at sufficiently high particle
concentrations, the larger particles exhibit higher mobility than the smaller
particles. Each of these dynamic behaviors is accompanied by a corresponding
structural trend that characterizes how either concentration or composition
affects the strength of the static pair correlations. Specifically, the dynamic
trends observed here are consistent with a single empirical scaling law that
relates an appropriately normalized tracer diffusivity to its pair-correlation
contribution to the excess entropy.Comment: 5 pages, 4 figure
Cofinement, entropy, and single-particle dynamics of equilibrium hard-sphere mixtures
We use discontinuous molecular dynamics and grand-canonical transition-matrix
Monte Carlo simulations to explore how confinement between parallel hard walls
modifies the relationships between packing fraction, self-diffusivity, partial
molar excess entropy, and total excess entropy for binary hard-sphere mixtures.
To accomplish this, we introduce an efficient algorithm to calculate partial
molar excess entropies from the transition-matrix Monte Carlo simulation data.
We find that the species-dependent self-diffusivities of confined fluids are
very similar to those of the bulk mixture if compared at the same,
appropriately defined, packing fraction up to intermediate values, but then
deviate negatively from the bulk behavior at higher packing fractions. On the
other hand, the relationships between self-diffusivity and partial molar excess
entropy (or total excess entropy) observed in the bulk fluid are preserved
under confinement even at relatively high packing fractions and for different
mixture compositions. This suggests that the partial molar excess entropy,
calculable from classical density functional theories of inhomogeneous fluids,
can be used to predict some of the nontrivial dynamical behaviors of fluid
mixtures in confined environments.Comment: submitted to JC
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