Analysis of residue curve maps of reactive and extractive distillation units

The aim of this work is to focus in the simultaneous analysis of reactive and extractive distillation, including the solvent recovery system. Residue curve maps can provide valuable insights and design assistance for a variety of separation processes, in which reactive distillation has been incorporated. These graphical techniques reveal the sensitivity of design options by giving us a visual representation over the whole composition space and assist the engineer to detect separation constraints. Simulation results show the reaction effect in the diagram topology: existence and position of nodes, saddles and distillation boundaries (separatrices or surfaces). Advanced distillation synthesis and design techniques, which are now supported by available software tools, were used to develop case studies for extractive distillation, entrainer influence in reactive systems and reactive distillation analysis with consecutive and/or competitive reactions.     

Theoretical and experimental study on residue curve maps of propyl acetate synthesis reaction

Residue curve maps (RCMs) of propyl acetate synthesis reaction in the batch reactive distillation process are studied. In order to adapt the model equations of residue curve maps to a practicable heating policy, the theoretical analysis and experimental measurements in this paper are carried out isothermally instead of the autonomous heat policy first introduced by Venimadhavan et al. (A.I.Ch.E. Journal 40 (1994) 1814-1824). The chemical equilibrium constant of this reaction is determined by experiments to be 20 within the temperature range 80-110 °C. Using this equilibrium constant, the RCMs predicted by simulation are in good agreement with the experimental measurements. The results show that there is an unstable node branch emerging from the propyl acetate-water edge, moving toward the chemical equilibrium surface with the increasing Damköhler number (Da), and eventually reaching the quaternary reactive azeotrope when Da→∞. Residue curves are measured with initial compositions around the unstable node, and thus the results verify the existence of this reactive azeotrope. Further bifurcation analysis shows that different heat policies will influence the singular points and topology of kinetically controlled RCMs, but not the cases when Da=0 or Da→∞.     

On the dynamics of distillation processes—III: The topological structure of ternary residue curve maps

The differential equations describing the simple distillation of azeotropic ternary mixtures place a physically meaningful structure (tangent vector field) on ternary phase diagrams. By recognizing that such structures are subject to the Poincaré-Hopf index theorem it has been possible to obtain a topological relationship between the azeotropes and pure components occurring in a ternary mixture. This relationship gives useful information about the distillation behavior of ternary mixtures and also predicts situations in which ternary azeotropes cannot occur.     

双循环法测定等液相组成汽—液平衡数据的研究及其应用

本工作研究了用双循环法测定等液相组成汽-液平衡数据的特点,建立了一种新型的SG—Ⅱ双循环沸点仪,测定了乙醇-正已烷体系15个浓度时的等液相组成数据,并推算了该体系298.15K至328.15K时的等温汽-液平衡、过量自由焓和微分汽化热。     

Evaluation of the local composition model for VLE of binary mixtures of triethylene glycol with methane,water and benzene

This work evaluated the predictive accuracy of the local composition model (LCM) formulation developed by Li et al. (1986) for four binary, vapor-liquid equilibria (VLE) mixtures. The four components comprising these mixtures were benzene, triethylene glycol (TEG), water and methane, while the mixtures examined in this work were the benzene-TEG, water-TEG, methane-TEG and methane-benzene systems. The Khan-Chung-Lee-Starling (KCLS) equation of state developed by Chung et al. (1984) was used with the LCM to predict the VLE behavior of these systems. The accurate results obtained in this work may be applied to the design of natural gas dehydration processes.     

Isobaric vapor–liquid equilibria for mixtures of tetrahydrofuran, 2-propanol, and 2,2,4-trimethylpentane at 101.3 kPa

Vapor–liquid equilibrium (VLE) at 101.3 kPa have been determined for a ternary system (tetrahydofuran + 2-propanol + 2,2,4-trimethylpentane) and its constituent binary systems (tetrahydrofuran + 2-propanol, tetrahydrofuran + 2,2,4-trimethylpentane, and 2-propanol + 2,2,4-trimethylpentane). The activity coefficients of liquid mixtures were calculated from the modified Raoult's law. Thermodynamic consistency tests were performed for all VLE data. The VLE data of the binary mixtures and ternary mixtures were correlated using the Margules, Wilson, NRTL, and UNIQUAC activity-coefficient models. The models with their best-fitted interaction parameters of the binary systems were used to predict the ternary vapor–liquid equilibrium. All VLE data are also used to calculate the reduced excess molar Gibbs free energy g^E/RT and the deviations in the boiling point ΔT. The calculated quantities of g^E/RT and ΔT were fitted to variable-degree polynomials in terms of liquid composition.     

Evaluation of biomass residue: 1. Briquetting waste paper and wheat straw mixtures

Studies have demonstrated that waste paper and wheat straw or their mixtures can be compressed to a relative density greater than unity, and stabilized at that density without binder material. A reduction in the volume of the material also provides a technological benefit, so the material could be transported and stored more economically than is possible at present. The effects of the briquetting pressure on the density, moisture content, and bending and compressive strengths of the briquettes were determined at six different pressures of 300, 400, 500, 600, 700 and 800 MPa. The optimum moisture contents and compressive strengths were found to be respectively 18.0% and 38.2 MPa for waste paper, 22.0% and 22.4 MPa for wheat straw, and 18.0% and 32.0 MPa for a 20.0% by weight of waste paper and straw mixture. The effect of the temperature and time on the briquette density of wheat straw was examined.     

Measurement and modelization of VLE of binary mixtures of propyl acetate,butyl acetate or isobutyl acetate with methanol at pressure of 0.6 MPa

The vapor–liquid equilibrium of binary mixtures of propyl acetate,butyl acetate and isobutyl acetate with methanol has been determined at a constant pressure of 0.6 MPa.Results have been modeled with the Peng–Robinson equation,a traditional cubic equation of state widely employed in chemical industries,as well as with the perturbed-chain statistical associating fluid PC-SAFT theory of Gross–Sadowski.By correlation of the binary interaction parameters of these equations,the measured vapor–liquid equilibrium data can be accurately predicted.Thus,this work shows that these models are able to represent the experimental data for systems with associating compounds via hydrogen bonding.     

Simultaneous modeling of VLE,LLE and VLLE of CO2 and 1, 2, 3 and 4 alkanol containing mixtures using GC-PPC-SAFT EOS

A polar version of the group contribution PC-SAFT equation of state (GC-PPC-SAFT; Tamouza et al., 2004; NguyenHuynh et al., 2008) combined with a method for correlation/prediction of binary interaction parameters k_ij (NguyenHuynh et al., 2008) is here applied to model vapor–liquid, liquid–liquid and vapor–liquid–liquid phase equilibria of CO₂ + alkanol mixtures simultaneously.A cross-association interaction between CO₂ and alkanol had to be taken into account to model/predict the mixtures equilibria accurately. The cross-association parameters were evaluated using the so-called CR1 mixing rules supported by ab initio computations.Extensive prediction tests on CO₂ + alkanol mixtures involving linear and branched alkanols are carried out. The results obtained showed that in most cases, the correlation and prediction calculations are qualitatively and quantitatively satisfactory: the overall deviations on liquid phase and vapor phase are respectively ΔX = 3–4% and ΔY = 1–2%.     

Composition and oxidative stability of soybean oil in mixtures with jojoba oil

Improvement of the oxidative stability of soybean oil (SBO) by blending with jojoba oil (JO) was investigated. SBO in the presence of 5, 10, 15 and 20 wt‐% of JO was subjected to accelerated storage at 60 °C. Peroxide values (PV), anisidine values (AV), UV absorption characteristics (K₂₃₂ and K₂₇₀ values), and headspace volatiles were determined to monitor the oxidative stability of oil samples. JO was effective in reducing the formation of hydroperoxides and volatile compounds in SBO. The effect was remarkable in SBO/JO blends containing 15 and 20% JO, which showed significant reductions in PV, AV and volatile content with respect to pure SBO. The increased oxidative stability of SBO/JO blends could not be attributed to JO tocopherols, since the addition of JO to SBO significantly reduced the tocopherol content of SBO. Besides the tocopherol content and unsaturation degree of SBO and JO, the effect of the JO ester structure on the oxidative stability of the blends is discussed. The enhanced chemical and flavor stabilities of SBO/JO blends with respect to pure SBO may make a significant contribution to improve the shelf life of SBO by reducing the deterioration reactions related to lipid peroxidation.     

Precipitation in solutions containing mixtures of synthetic anionic surfactant and soap. I. Effect of sodium octanoate on hardness tolerance of sodium dodecyl sulfate

The effect of sodium octanoate (SO) and pH on the precipitation of sodium dodecyl sulfate (SDS) with calcium (hardness tolerance) in water was investigated. SO can exist as octanoate anion (O⁻) or as the protonated nonionic fatty acid (HO) with the HO/O⁻ ratio increasing with decreasing pH. At intermediate pH levels, SO or SO/SDS systems are composed of mixtures of anionic and nonionic surfactants, resulting in enhancement of micelle formation due to nonideal mixed micelle formation. Above the critical micelle concentration (CMC), the highest hardness tolerance at each pH level occurs at a mole ratio of 80∶20 SDS/SO due to synergism in the SDS/SO mixtures. This synergism also results in an increase in hardness tolerance of SDS with decreasing pH above the CMC.     

Neural and Hybrid Neural Modeling and Control of Fed‐Batch Fermentation for Streptokinase: Comparative Evaluation under Nonideal Conditions

Fermentations involving competition between two or more kinds of cells under nonideal conditions show complex profiles that are sensitive to the extra‐cellular environment. These fermentations therefore require accurate and rapid on‐line data acquisition and control. However, both on‐line measurements and modelling are difficult and expensive for large bioreactors, thus limiting the usefulness of model‐based control. While neural networks offer an alternative, they require extensive training and can be difficult to optimize for large arrays. Hybrid networks combining a few neural networks with some mathematical equations offer a good compromise. The possibility of using a hybrid model for simulation‐cum‐control has been examined here for the fed‐batch production of streptokinase. Under noideal conditions, hybrid neural models outperformed both mathematical models and arrays of neural networks, thus suggesting their viability for large‐scale fermentation monitoring and control.     

Modeling of Heat and Mass Transport in Two-Phase Media by Considering Liquid Pressure

A new model to describe heat and mass transport during drying of two-phase media is proposed. The medium is considered as a two continuous immiscible phases on which the method of volume averaging is applied in order to derive continuum equations for multiphase systems. The liquid flow is induced by a pressure gradient which cannot be deduced from the capillary pressure like in a triphasic medium. Numerous authors avoid this problem by introducing a phenomenological law binding the pressure to the volume fraction of the liquid phase. In the obtained model, the pressure is calculated from the solid mass conservation in such a way that transport phenomena depend notably on the rheological behavior.     

A study of liquid molar volumes for some pure halogenated hydrocarbons and their binary mixtures

Liquid volume data have been measured at compressed liquid conditions for four pure refrigerants, CCl₃ F, CCl₂ F₂, CHClF₂ and C₂ Cl₂ F₄, and three mixtures, CCl₂ F₂/CCl₃ F, CCl₂ F₂/C₂ Cl₂ F₄, and CHClF₂/C₂ Cl₂ F₄. A comparison of measured data and data reported in the literature with calculated data by three methods is presented. The three methods are the Thomson-Brobst-Hankinson correlation, and two equations of state according to Carnahan-Starling-de Santis and Lee-Kesler-Plöcker. In general the Thomson-Brobst-Hankinson correlation shows a smaller deviation from experimental data than the two equations of state examined.     

Oxidation of Magnesiowustite Single Crystals: II, Dependence on Temperature, Oxygen Pressure, and Crystal Composition

Single crystals of magnesiowustite (Mg,Fe)O containing up to 79 at.% Fe were prepared, and the proportions of ferrous and ferric ions were determined by chemical analysis. The rate of oxidation of individual crystals was studied at temperatures from 1000° to 1100°C and oxygen partial pressures of 2 × 10⁻¹ to 3 × 10⁻⁶ atm. The reaction follows an equation based on diffusion through a product layer. The rate constant varies with temperature according to the Arrhenius relation, and activation energies range from 52 kcal/mole with 13 at.% Fe to about 17 to 20 kcal/mole when Fe atoms occupy one third or more of the cation positions. The rate constant is independent of oxygen partial pressure within the pressure range studied. Spectrographic measurements show that Fe in magnesiowustite occupies mainly octahedral sites, but some tetra-hedral positions appear to be occupied. The mechanism of the oxidation reaction is considered.     

Pressure gradient and liquid film thickness in co-current upwards flow of gas/liquid mixtures: Application to film-cooler design

Expressions have been developed for pressure gradient and liquid film thickness in upwards annular co-current flow of gas and liquid in the absence of disturbance waves and droplet entrainment. Experimental measurements of pressure gradient have been made with various phase flow rates, tube diameters and physical properties of the liquid. The results have been correlated in terms of the equivalent sand-roughness of the liquid film.     

Similarity Solutions of Marangoni Convection Boundary Layer Flow with Gravity and External Pressure

This study is focused on a steady dissipative layer, which is generated by Marangoni convection flow over the surface resulted from an imposed temperature gradient, coupled with buoyancy effects due to gravity and external pressure. A model is proposed with Marangoni condition in the boundary conditions at the interface. The similarity equations are determined and approximate analytical solutions are obtained by an efficient transformation, asymptotic expansion and Pade approximant technique. For the cases that buoyancy force is favorable or unfavor-able to Marangoni flow, the features of flow and temperature fields are investigated in terms of Marangoni mixed convection parameter and Prantl number.     

Synthesis and characterization of functional copolymer of Linalool and vinyl acetate: A kinetic study

Linalool (LIN) and vinyl acetate (VA) were copolymerized by benzoyl peroxide (BPO) in p‐xylene at 60°C for 90 min. The system follows nonideal kinetics: R_pα[I]^0.6[LIN]^1.2[VA]^1.1. It results in the formation of alternating copolymer as evidenced from reactivity ratios as r₁ (VA) = 0.01, r₂ (LIN) = 0.0015, which have been calculated by Kelen–Tudos method. The overall activation energy is 82 kJ/mol. The FTIR spectrum of the copolymer shows the presence of the band at 3425 cm^?1 due to alcoholic group of LIN and at 1641 cm^?1 due to >C?O group of VA. The ¹H‐NMR spectrum shows peaks at 7.0–7.7 δ due to hydroxy proton of LIN and at 1.0–1.4 δ due to acetoxy protons of VA. ¹³C‐NMR spectrum of copolymer shows peaks at 167 ppm due to acetoxy group and at 75–77 ppm due to C? OH group. The Alfrey–Price Q–e parameters for LIN has been calculated as Q₂ = 1.24 and e₂ = 3.11. The copolymer is highly thermally stable and has a glass transition temperature (T_g) of 85°C, evaluated from DSC studies. The mechanism of copolymerization has been elucidated. This article also reports measurement of Mark–Houwink constants in THF at 25°C by means of GPC as α = 0.8 and K = 3.0 × 10^?4 dl/g. The thermal decompositions of copolymer are established with the help of TGA technique. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1134–1143, 2004     

Composition and Performance of Styrene-Isoprene-Styrene (SIS) and Styrene-Butadiene-Styrene (SBS) Hot Melt Pressure Sensitive Adhesives

Styrenic block copolymers are widely used in HMPSA formulations, with tackifier resins and oil plasticizer. Although most commercial formulations are based on SIS, mixtures of SIS and SBS are also used to reduce cost. However, the use of SBS is restricted because it generally leads to decrease in tack. In this work, pure SIS and SBS and a SIS/SBS mixture were used in formulations with aliphatic, aromatic, aliphatic hydrogenated, and aliphatic-aromatic copolymer resins, at three different oil contents, according to a 3^3–1 factorial design. Interaction effects among the components were evaluated, showing a strong dependence of the HMPSA final properties on the combination of resin/rubber used. It was found that a blend of aliphatic and aromatic resins is the best tackifier for SIS, while for SBS the best choice is an aromatic-aliphatic copolymer. These results were explained in terms of specific compatibility, which was correlated to the polarizability of the material.     

An oscillatory pressure sintering of zirconia powder: Densification trajectories and mechanical properties

The densification trajectories and mechanical properties of zirconia ceramics obtained by oscillatory pressure sintering (OPS) process were investigated, during the sintering process an oscillatory pressure was applied at three stages. Current results indicated that at intermediate stage the oscillatory pressure revealed a favorable improvement of mechanical properties compared with conventional hot pressing (HP) and pressureless sintering (PS) procedures, while the enhancement was not obvious at initial stage. When the oscillatory pressure was applied at final stage, the OPS specimens exhibited the highest bending strength and hardness of 1455 ± 99MPa and 16.6 ± 0.31GPa compared with the PS and HP specimens. Considering the high elastic modulus and Moiré patterns observed in the OPS specimen, the oscillatory pressure applied at intermediate and final stages was detected to facilitate the sliding of grain boundary, plastic deformation of monolithic grains, the removal of pores and the strengthening of atomic bonds.