The aim of the present study was to investigate biosurfactant-producing culturable bacteria inhabiting the coast of the Arabian Sea at Karachi. Overall, 15 seawater samples were collected from the Arabian Sea coast of Karachi. Isolation, characterization, and screening for 89 biosurfactant-producing bacterial strains were conducted through 8 conventional screening tests. Through GSP agar plate method 22 strains were found to be Pseudomonas aeruginosa and Gram reaction revealed 70% of the isolates to be gramnegative. Furthermore, 24% of the isolates showed hemolytic activity, 44% exhibited positive results for oil-spreading test, 54% showed emulsification to at least 1 of the 3 hydrocarbons tested, BATH assay results indicated maximum adhesion for hexane, 52.8% produced positive results for CTAB agar plate assay, drop-collapse activity was found in 84% of the isolates, and emulsification assay revealed highest emulsification for xylene. Findings revealed none of the isolates to be negative for every screening test conducted, while only one gram-negative isolate, DGHE65, identified as Pseudomonas aeruginosa, was positive for all the tests for biosurfactant production. Results indicate that these isolates have potential for future environmental friendly applications such as bioremediation and industrial biotechnology.
Ammonia (NH3) is an important chemical in several fields, such as agriculture, pharmaceutical, material, and chemicals manufacturing. However, NH3 is a toxic gaseous pollutant and NH3 release results in environment pollution. Minimizing NH3 emission is of great significance for solving NH3-related environmental issues and promoting the reuse of NH3 resources. Ionic liquids (ILs) are energy-saving gas absorbents, because of their low vapor pressure, good chemical stability, and high NH3 solubility. The recent research progress of conventional, functionalized ILs and novel IL-based materials and solvents for NH3 separation was summarized. The effects of anions and cations on NH3 absorption capacity, as well as the absorption mechanism of ILs, were discussed in detail in this Review. The simulated dynamic parameters of NH3–IL systems including mass diffusivity, heat- and mass-transfer coefficient were also discussed. In addition, this Review summarized the industrial application achievement of ILs in NH3 separation and recovery from NH3-containing tail gas, which spans from simulation, pilot plant to industrial applications. Finally, the research trends in NH3 separation by IL-based systems were proposed based on existing research.
The efficient capture of carbon dioxide (CO 2 ) has industrial, economic, and environmental significance. Here, CO 2 capture performance in terms of CO 2 /CH 4 selectivity for the zeolitic imidazolate framework (ZIF-8) is enhanced by impregnation of 1-nbutyl-3-methylimidazolium dicyanide [BMIM][DCA]. The preparation of ionic liquids (ILs)/ZIF-8 composites, their comprehensive characterization, and the impact of IL impregnation are all investigated. The crystal structure and morphology of ZIF-8 remained intact even after the impregnation of ILs, according to X-ray diffraction and scanning electron microscopy studies. The infrared spectroscopy known as Fourier transform infrared spectroscopy determines the interaction between ILs and ZIF-8 in the composite. The isotherm fitting was also performed by dual site Langmuir models, which showed good agreement with the experimental results. The CO 2 /CH 4 selectivity results demonstrated that the ideal selectivity for the IL-impregnated ZIF-8 composite has five times higher selectivity than pristine ZIF-8 at 0.05 bar which is the highest reported selectivity. The normalized selectivity of this type of IL/ZIF-8 composite is also higher. This study suggested that the IL/MOF composite with a tunable structure have a strong potential for enhanced acid gas separation performance to meet the environmental challenges.
In this paper, a two-level finite element method for Oseen viscoelastic fluid flow obeying an Oldroyd-B type constitutive law is presented. With the newly proposed algorithm, solving a large system of the constitutive equations will not be much more complex than the solution of one linearized equation. The viscoelastic fluid flow constitutive equation consists of nonlinear terms, which are linearized by taking a known velocity b(x), and transforms into the Oseen viscoelastic fluid flow model. Since Oseen viscoelastic fluid flow is already linear, we use a two-level method with a new technique. The two-level approach is consistent and efficient to study the coupled system which contains nonlinear terms. In the first step, the solution on the coarse grid is derived, and the result is used to determine the solution on the fine mesh in the second step. The decoupling algorithm takes two steps to solve a linear system on the fine mesh. The stability of the algorithm is derived for the temporal discretization and obtains the desired error bound. Two numerical experiments are executed to show the accuracy of the theoretical analysis. The approximations of the stress tensor, velocity vector, and pressure field are P1-discontinuous, P2-continuous and P1-continuous finite elements respectively.
An automated and compact multiphase flow meter (MPFM) tested offshore Saudi Arabia has accurately measured three-phase flow rates under existing field operating flow conditions. An extensive eight-month field test in the Safaniya field was conducted from October 1999 to June 2000 utilizing over 350 well tests under varying operating conditions. A meter was installed on an offshore test barge, so that individual wells could be tested in series with traditional test barge methods. For these trial tests, the total liquid rate ranged from 1300 to 12000 barrels per day, the GOR ranged from 150 to 350 SCF/STB and the water cut ranged from 0 to 50%. The results show that over 90% of the wells tested were within +/- 10% of test barge results for all liquid, oil and water cut measurements. While gas measurements were determined to be within +/- 15% in 75% of the wells tested. As a result of this favorable field test and other economic considerations, a multiphase flow meter is recommended for installation on all Safaniya Field existing offshore platforms. Project installation designs for the first five meters have been completed and plans are being made to install them beginning in early 2002. Introduction The Safaniya Field, which is the largest offshore oil field in the world, has a wide variety of offshore platforms. These platforms differ in physical size and vary from single well to eight-well configurations. For accurate reservoir management, each well is individually rate tested to monitor well performance and to provide data for field allocation and planning purposes. The wells are presently being tested by two barges, which are equipped with testing facilities. These barges are approaching obsolescence and require extensive maintenance to maintain the current testing schedule. In addition, numerous offshore platforms are located in areas that are inaccessible to the barges and cannot be easily tested. The barges are also prevented from testing wells approximately one third (1/3) of the time each year due to adverse weather conditions. Furthermore, well testing requirements for the Safaniya field are increasing dramatically due to higher water cuts as the field matures, more wells being drilled, and fluctuations in the field production requirements. As a result of the inefficiency and limitations of the test barges, a multi-phase flow meter was successfully field-tested as an alternative to the use of the test barges. Multiphase flow meters will provide the Safaniya field with more frequent tests and considerable economical savings in the long run. Meter Description The Fluenta multiphase meter 1900VI trial tested in Safaniya field is the latest multiphase flow meter produced by Roxar in Norway. This meter measures oil, gas and water rates without separation of the production stream, and calculates flow rates for actual and standard conditions. The multiphase meter determines oil, gas and water fractions from the capacitance, inductance readings and gamma densitometer measurements. Each component's velocity, or mass flow rate, is determined from cross correlation or venturi measurements. There are five main components to the MPFM:Capacitance sensor;Inductance sensor;Venturi;Gamma densitometer; andPressure and temperature sensors (see Fig. 1). A detailed discussion of each meter component and underlying operating principles can be obtained from the vendor, if interested.
In this paper, we present a stabilized lowest equal-order mixed finite element (FE) method for the Oseen viscoelastic fluid flow obeying an Oldroyd-B type constitutive law. To approximate the velocity, pressure, and stress tensor, we choose lowest equal-order FE triples p1-p1-p1 dg respectively. It is well known that these elements don't satisfy the inf-sup (or LBB) condition. Owing to the violation of the essential stability condition, the system became unstable. To overcome this difficulty, a standard pressure stabilization term is added to the discrete variational formulation, which ensures the well-posedness of the FE scheme. The existences and uniqueness of the FE scheme are derived. The desired optimal error bound is obtained. Three numerical experiments are executed to illustrate the validity and efficiency of the numerical method. The stabilized method provides attractive computational advantages, such as simpler data structures, parameter-free, no calculations of higher-order derivatives, and fast solver in simulations.
In this paper, a novel theoretical model has been developed to obtain focal points of temperatures in helium cooled ceramic breeder (HCCB) blanket system of China Fusion Engineering Test Reactor (CFETR). The main objective of the paper is to develop a theoretical-computational model for safety of blanket system, structure stress analysis and feasibility design. The theoretical-computational model was developed and verified by computational techniques using C++/MATLAB program and later with thermo-hydraulic system codes, i.e. RELAP5 and THEATRE. Mathematical model was developed for the thermal conductivity in HCCB blanket system and heat conduction model by using numerical technique. This model was then transferred to C++/MATLAB program and developed a program for calculating the thermal contact temperature of HCCB region. The calculated temperature values were then compared with RELAP5 and THEATRE codes for the accuracy of theoretical model. The preliminary thermal-hydraulic simulation results indicate that the maximum temperature on the first wall (FW) satisfies the design allowable limit and that the cooling channels were designed accurately. The results obtained from these analyses are very close to the experimentally defined values depicting the accuracy of theoretical and simulation results. The calculated results can be applicable to other tokamak devices like CFETR, ITER and JET as well.
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