Phase Diagrams in Chemical Engineering: Application to Distillation and Solvent Extraction

Chapter 19Published under CC BY 3.0 licenseAvailable from: http://www.intechopen.com/books/advances-in-chemical-engineering/phase-diagrams-in-chemical-engineering-example-of-distillationInternational audienceA phase diagram in physical chemistry and chemical engineering is a graphical representation showing distinct phases which are in thermodynamic equilibrium. Since these equilibrium relationships are dependent on the pressure, temperature, and composition of the system, a phase diagram provides a graphical visualization of the effects of these system variables on the equilbrium behavior between the phases. Phase diagrams are essential in the understanding and development of separation processes, especially in the choice and design of separation unit operations, e.g. knowledge about high pressure phase equilibria is essential not just in chemical processes and separation operations, but is also important for the simulation of petroleum reservoirs, the transportation of petroleum fluids, as well as in the refrigeration industry. In order to utilize the knowledge of phase behavior it is important to represent or correlate the phase information via the most accurate thermodynamic models. Thermodynamic models enable a mathematical representation of the phase diagram which ensures comprehensive and reproducible production of phase diagrams. The measurement of phase equilibrium data is necessary to develop and refine thermodynamic models, as well as to adjust them by fitting or correlating their parameters to experimental data. Generally the measurement of phase equilibria is undertaken using two categories of experimental techniques, viz. synthetic and analytic methods. The choice of the technique depends on the type of data to be determined, the range of temperatures and pressures, the precision required, and also the order of magnitude of the phase concentrations expected

Vapour-Liquid Equilibria of Ethane and Ethanethiol : Experiments and Modelling

We acknowledge the Scottish Funding Council for providing a travel grant to Dr Waheed Afzal under Northern Research Partnership program. Mr Pascal Theveneau is gratefully acknowledged for his support to adopt experimental setup for this work.Peer reviewedPublisher PD

Experimental Determination of Thermophysical Properties of Working Fluids for ORC Applications

The design and optimization of Organic Rankine Cycle (ORC) require knowledge concerning the thermophysical properties of the working fluids: pure components or mixtures. These properties are generally calculated by thermodynamic and transport property models (thermodynamic or equation of state or correlations). The parameters of these models are adjusted on accurate experimental data. The main experimental data of interest concern phase equilibrium properties (noncritical and critical data), volumetric properties (density and speed of sound), energetic properties (enthalpy, heat capacity), and transport properties (dynamic viscosity and thermal conductivity). In this chapter, some experimental techniques frequently used to obtain the experimental data are presented. Also, we will present some models frequently used to correlate the data and some results (comparison between experimental data and model predictions)

CO 2 Solubility in Hybrid Solvents Containing 1- Butyl-3-methylimidazolium tetrafluoroborate and Mixtures of Alkanolamines

International audienceTo reduce the rate of climate change, feasible and energy-efficient solutions need to be found to capture CO2 at low pressure from flue gas emitted by various industries and energy sectors worldwide. The use of solvents to selectively absorb CO2 is a promising option for CO2 capture. This research investigated the solubility of CO2 in hybrid solvents containing the 1-butyl-3-methyl imidazolium tetrafluoroborate [bmim][BF4] ionic liquid with mixtures of up to three alkanolamine solvents, namely monoethanolamine (MEA), diethanolamine (DEA), and methyl-diethanolamine (MDEA). Gravimetric analysis was used to measure equilibrium CO2 solubility in the hybrid solvents containing various compositions of the above components at CO2 partial pressures of 0.05 MPa to 1.5 MPa and temperatures of 303.15 K to 323.15 K. CO2 solubility in these solvents was benchmarked against pure ionic liquids, as well as conventional alkanolamine solvents, and modeled using the Posey−Tapperson−Rochelle model for the alkanolamines present and the SRK equation of state for the ionic liquid present in the hybrid solvents. It was found that the hybrid solventsachieved significantly higher CO2 solubility at low pressure than pure ionic liquids and conventional alkanolamine solvents. Modeling, however, was found to be less accurate for hybrid systems than data modeled for pure ionic liquid systems

Thermodynamic Study of binary an ternary systems containing CO2 + impurities in the context of CO2 transportation

International audienceCO2 capture transportation and storage, or CO2 capture transportation and utilization, are two ways which should be considered in the industry in order to reduce the emission of CO2. After capture, CO2 is not pure and contain impurities like SO2, NOx, N2, O2 and Ar for example. Two binary systems involving CO2 were studied in this work (CO2 + SO2 at 263.15 and ACCEPTED MANUSCRIPT 333.21 K and between 0.1 and 8.8 MPa and CO2 + NO in at 232.93, 252.98 and 273.15 K, and between 1 and 11.5 MPa ) and two ternary systems (CO2 + O2 + Ar and CO2 + SO2 + O2 (expected composition (0.94/0.03/0.03 mole fractions)) at 253, 273 and 293 K, between 1.9 and 7.6 MPa) were also studied experimentally. The equipment used is based on "staticanalytic" method, taking advantage of two capillary samplers (Rolsi™, Armines' patent). The classical Peng-Robinson equation of state is used to represent the isothermal P, x, y data.

Prédiction des propriétés thermodynamiques des fluides frigorigènes avec une nouvelle équation d'état cubique à trois paramètres

International audienceTo describe the thermodynamic properties of refrigerant fluids, it is important to use a reliable thermodynamic model able to predict accurate results for both pure compounds and mixtures. In this study, a new three-parameter cubic equation of state is presented, based on the modification of the well-known Patel-Teja equation of state. The new equation of state is associated with the Mathias-Copeman alpha function. By only knowing the acentric factor ω and the experimental critical compressibility factor Z c of pure compounds, it is possible to predict thermodynamic properties for both pure compounds and mixtures by means of the new equation of state. No binary interaction parameter k ij is needed for the prediction of mixture properties. The results obtained with the new equation of state show a good agreement with experimental data for vapor-liquid equilibrium and density properties. The obtained results are particularly satisfying for liquid density, and in the vicinity of the critical point, by comparison with the results obtained using the Peng-Robinson and the Patel-Teja equations of state

Phase Equilibria of Three Binary Mixtures: Methanethiol + Methane, Methanethiol + Nitrogen, and Methanethiol + Carbon Dioxide

International audienceNew vapor-liquid equilibrium (VLE) data for methanethiol (MM) + methane (CH 4), methanethiol (MM) + nitrogen (N 2), and methanethiol (MM) + carbon dioxide (CO 2) is reported for temperatures of (304, 334, and 364) K in the pressure range (1 to 8) MPa. A "static- analytic" method was used for performing the measurements. The objective is to provide experimental VLE data for methanethiol with other natural gas contents at its crude form, for which no data are available in the open literature. The new VLE data for the aforementioned systems have been modeled successfully with the cubic-plus-association equation of state (CPA EoS)

A generalized Kiselev crossover approach applied to Soave–Redlich–Kwong equation of state

International audienceThree different variants of the crossover Soave–Redlich–Kwong equation of state are applied to describe the equilibrium behaviour of 72 common non-associating fluids – 27 hydrocarbons (including the first 10 n-alkanes), 36 halogenated refrigerants, 5 cryogenics (fluorine, oxygen, nitrogen, argon and carbon monoxide) and 4 other industrially important inorganic fluids (carbon dioxide, sulfur dioxide, nitrous oxide and sulfur hexafluoride). The model contains six compound dependent parameters.Two of them (a0 and b of the classical part) are adjusted on the critical experimental temperature and the critical pressure. In a first model denoted as model A, the four remaining parameters are fitted to describe the saturated liquid and vapour densities and vapor pressures as well as PVT data at pressures up to P = 3 × Pc. In the second model (model B), the dispersion softness m is expressed as a function of the acentric factor ω and a relation between two of the crossover parameters is employed; the number of fitted parameters is thus reduced to two. Based on model B, we suggested our final Model C, in which all the parameters can be determined from the critical point, acentric factor or rectlinear diameter. This model is superior to the classical Soave–Redlich–Kwong equation of state because it improves considerably the description of the liquid densities over the whole coexistence region. Contrary to equations of state optimized to reproduce the liquid densities at low temperatures, the crossover equation does not overpredict the critical temperature and pressure. Model C is applied to describe the equilibrium behaviour of two compounds not included in the parameterization, hexafluoropropene (HFO1216) and hexafluoropropene oxide (HFPO)

Prediction of methanol content in natural gas with the GC-PR-CPA model

International audienceProduced reservoir fluids are principally composed of hydrocarbons but contain also impurities such as carbon dioxide, hydrogen sulphide and nitrogen. These fluids are saturated with the formation water at reservoir conditions. During production, transportation and processing ice and/or gas hydrates formation may occur. Gas hydrate and ice formation are a serious flow assurance and inherently security issues in natural gas production, processing and transport. Therefore, inhibitors are usually injected as a hydrate inhibitor and antifreeze. For example, methanol is often used for hydrate inhibition or in some cases during start up, shut down or pipeline plug removal. Therefore impurities, water and methanol usually end up in natural gas conditioning and fractionation units. These units produce end user pipeline gas subject to local specifications and natural gas liquids like ethane, LPG or heaviers. This is why the accurate knowledge of methanol content at different operating conditions is important. In this study, a group contribution model, the GC-PR-CPA EoS (Hajiw et al., 2015) (Group Contribution – Peng-Robinson – Cubic-Plus-Association), is successfully applied for hydrocarbons systems containing methanol. Predictions of phase envelopes of binary systems as well as partition coefficients of methanol in hydrocarbons mixtures are in good agreement with experimental data