Supercritical CO2 Extraction of Organic Solvents from Flunisolide and Fluticasone Propionate

In this work, Class 2 and Class 3 solvents contained in two corticosteroids, flunisolide (Fluni) and fluticasone propionate (Fluti), were reduced to a few ppm by supercritical CO2 extraction. The process was carried out at pressures from 80 to 200 bar, temperatures of 40 °C and 80 °C, and at a fixed CO2 flow rate of 0.7 kg/h. The results demonstrated that CO2 density is the key parameter influencing the extraction kinetics and the solvent final residue. In particular, in the range investigated, optimal pressure and temperature conditions for the extraction of residual organic solvents were found working at 200 bar and 40 °C, which corresponds to a CO2 density of 0.840 g/cm3. Operating in this way, total organic solvent residues were reduced from 13,671 ppm and 326 ppm to 12 ppm and 10 ppm for Fluni and Fluti, respectively.

First estimations of gravity wave potential energy in the Martian thermosphere: an analysis using MAVEN NGIMS data

ABSTRACT First estimations of Gravity Wave Potential Energy (GWPE) for Martian thermosphere are reported herein using the height profile of CO2 density derived temperature fluctuations for different Martian seasons during the 33rd Martian year. Explicit diurnal evolution of GWPE (52⁰ to 73⁰ latitude bin) with a post sunset maximum is delineated for summer. The higher values of GWPE are observed during morning, compared to post-midnight (35⁰ to 55⁰ latitude bin) for summer. As latitude increases from 16⁰ to 45⁰, GWPE (1-4 LT bin) is found to be nearly doubled for summer. Further, GWPE estimates in autumn are 6 times higher during night compared to day (-45⁰ to -72⁰ latitude bin) and day time (-53⁰ to -72⁰ latitude bin) GWPE is much lower in autumn compared to spring for all longitudes. Overall, from the available data, southern autumn daytime periods appear better suited for aero-braking operations of Martian landing missions.

A Practical Study on Reducing CO2 Density in Educational Buildings in North-East China

Indoor air quality is a major contributor to the quality of people’s lives. Notwithstanding pollutants that are becoming increasingly prevalent from new building materials, furnishings and consumer products, CO2 density in educational buildings has been identified as a significant issue affecting students’ performance. This paper presents the results of monitored CO2 levels in differing educational facilities in north-east China during the winter period when windows have remained typically always closed to minimise heat loss. The negative impacts of CO2 density is demonstrated to affect students’ decision-making capabilities, and also the relevant Chinese building regulations related to the requirements of indoor air exchange have been reviewed. Finally, this research proffers practical solutions to improve indoor air quality, specifically related to CO2 density in educational buildings.

CO2 EOR Potential in Naturally Fractured Haft Kel Field, Iran

Summary We present results studying the enhanced-oil-recovery (EOR) potential for carbon dioxide (CO2) injection in the naturally fractured Haft Kel field, Iran, on the basis of detailed compositional simulations of a homogeneous single matrix block surrounded by fractures. Oil recoveries from CO2 injection in this idealized model approach 90% for reservoir pressures of 1,400 psia and higher (i.e., at and above current reservoir pressure of 1,500–1,800 psia). It is expected that heterogeneity will reduce recovery on the field scale. This compares with 15–25% recoveries reported for gas-cap expansion and/or injection of hydrocarbon (HC) gas. Fundamentally different recovery mechanisms develop above and below 2,000 psia, the pressure at which CO2 density equals the reservoir-oil density. At lower pressures, CO2 is less dense than reservoir oil and traditional gas/oil gravity segregation results, with a highly efficient process driven by gravity, compositional effects, and interfacial-tension (IFT) gradients that cause capillary-induced oil flow. At pressures greater than 2,000 psia, CO2 density is greater than reservoir-oil density, resulting in an unusual gravity-drainage mechanism whereby CO2 enters the bottom of a matrix block and pushes oil out the sides and top of the matrix block. The effect of several key parameters has been studied in detail—matrix permeability, matrix-block size, matrix/matrix capillary continuity (stacked blocks), and the use of mixtures of CO2 and HC gas. One of the key results is how the rate of recovery differs for combined injection of HC gas and CO2, and how it varies for CO2 injection for different model parameters. EOR results are affected by grid sensitivity. Grid effects have been quantified and compared for different model parameters. Final EOR assessment is made using models in which sufficient grid refinement is used to minimize grid sensitivity.