Solubility of vitamin A in supercritical CO2: experimental study and thermodynamic modeling

One of the best methods of extracting Vitamin A, as a helper of the immune body system and vision, was measured in supercritical carbon dioxide (SC-CO2); Mole fractions were gained at practical conditions in which the temperature was in the range of 303–323 K and the pressure range was 90–235 bar, respectively. Moreover, four Equation of States [Soave–Redlich–Kwong, Peng–Robinson, Stryjek–Vera and Dashtizadeh–Pazuki–Taghikhani–Ghotbi (DPTG)] were compared with the experimental data. Also, the mixing rules of Van der Waals (vdW1 and vdW2) selected to correlate the solubility data of vitamin A. The outcomes indicate that each of EOSs coupled with vdW2, as a method of estimating the physicochemical and critical properties, were correlated with the solubility data of vitamin A in SC-CO2 with more accuracy, in comparison with vdW1. Among the cubic EOSs, the DPTG model with vdW2 generated the most suitable correlation with the percentage average absolute relative deviation (Average Absolute Relative Deviation%) of 6.

Pemodelan dan Simulasi Pencairan Gas Alam dengan Persamaan Keadaan Peng Robinson

<p class="E-JOURNALBody">Gas alam merupakan energi <span lang="EN-US">yang </span>ramah lingkungan<span lang="EN-US"> dibandingkan batu</span><span lang="EN-US">bara dan minyak bumi</span>. <span lang="EN-US">Pencairan gas alam memudahkan pengangkutan pada jarak jauh. Tujuan pemodelan dan simulasi pencairan gas alam ini yaitu mengetahui pengaruh temperatur dan tekanan pada masukan kompresor. Simulasi dilakukan secara statis dan dinamis. </span>Metode simulasi pencairan gas alam <span lang="EN-US">menggunakan perangkat </span>Matlab dengan persamaan keadaan Peng Robinson dan aturan campuran (<em>mixing rules</em>). Pemodelan stati<span lang="EN-US">s</span><span lang="EN-US">dilakukan pada t</span>emperatur masukan gas alam 298 K dan tekanan 20 atm. Hasil simulasi menunjukkan gas alam mengalami pencairan pada siklus kedua. <span lang="EN-US">T</span>emperatur gas alam <span lang="EN-US">siklus pertama mencapai 1</span>82 K<span lang="EN-US"> sedangkan </span>kedua 112 K.<span lang="EN-US"> Pemodelan dinamis memvariasikan temperatur masukan kompresor pada komposisi gas alam tetap dan variasi komposisi gas metana pada temperatur masukan kompresor tetap. Hasil menunjukkan semakin tinggi temperatur masukan kompresor</span>,<span lang="EN-US"> semakin tinggi temperatur keluaran kompresor akhir dan <em>throttling valve</em>. Pada variasi komposisi gas metana, semakin besar komposisi gas metana maka semakin rendah suhu keluaran kompresor.</span></p>

Research Method of Phase Behavior in Gas-Crude System and the Application in L Block with HP/HT

This paper provide improved phase behavior models, trying to mitigate the problem that phase behavior of gas-crude system is difficult to describe in L block with low permeability and high water cut in China. This situation leads to a series of problems in CO2 flooding process and lower recovery up to expectations. The models is evaluated to possess both high calculation speed and accuracy compared with existing others. Characteristics of CO2-crude systems had been considered into repulsion-attraction type EOS (equation of state) based on the analysis of repulsion parameter and attraction parameter in EOS, and the improved EOS had been applied in developing calculation method of MMP (minimum miscible pressure). No ideality of CO2-crude systems had been considered into mixing rules of CO2-crude systems based on analysis of mixing rules of repulsion-attraction type EOS. Promotion had also been put into the obtain methods of parameters in phase behavior, including density, viscosity, MMP, critical parameters of plus components etc. All these methods are applied in L Block. The phase behavior models of CO2-crudes system promoted in this paper mainly include EOS, mixing rule and viscosity model and have been applied in CO2 flooding process in T Reservoir. The relative error of density calculation is reduced from 7% ∼ 20% to less than 1%and the modified EOS is applied to predict the MMP of the CO2-crude systems from 8 different blocks in T reservoir. The modified EOS also works well for the relative error of MMP prediction is reduced from 20% ∼ 70% to less than 5%. Compared with the existing mixing rules, the modified mixing rule is with higher calculation speed and accuracy. The relative error of components mole fraction calculation is reduced from 30% ∼ 80% to less than 10%. Compared with the existing viscosity models, there are large improvements of the modified viscosity model in accuracy. The relative error of viscosity simulation is reduced from more than 50% to about 5%. According to the simulation results, C2∼C15 are the key hydrocarbons with positive effect on the miscibility of CO2-crude systems, while C16+ are the key hydrocarbons with negative effect. The recovery of the pilot has increased by 23% by these methods. The improved phase behavior models provided in this paper possess as good performance as existing models in calculation speed, and accustom a big step forward in simulation accuracy. The modified components of the models also partially complete physical meaning in describing phase behavior of CO2-crude system. All the models mentioned above are finally applied in L block with HP/HT and high water cut and obtained an increase in recovery by 19.2%.

Like dissolves like: A first-principles theory for predicting liquid miscibility and mixture dielectric constant

Liquid mixtures are ubiquitous. Miscibility and dielectric constant are fundamental properties that govern the applications of liquid mixtures. However, despite their importance, miscibility is usually predicted qualitatively based on the vaguely defined polarity of the liquids, and the dielectric constant of the mixture is modeled by introducing mixing rules. Here, we develop a first-principles theory for polar liquid mixtures using a statistical field approach, without resorting to mixing rules. With this theory, we obtain simple expressions for the mixture’s dielectric constant and free energy of mixing. The dielectric constant predicted by this theory agrees well with measured data for simple binary mixtures. On the basis of the derived free energy of mixing, we can construct a miscibility map in the parameter space of the dielectric constant and molar volume for each liquid. The predicted miscibility shows remarkable agreement with known data, thus providing a quantitative basis for the empirical “like-dissolves-like” rule.