Asphaltene precipitation causes several problems during crude oil production, transportation, and refinery processes. Therefore, finding an inhibitor to prevent or delay asphaltene precipitation is ...of paramount importance. In this work, effects of TiO2, ZrO2, and SiO2 fine nanoparticles in organic-based nanofluids have been investigated to study their potential for stabilizing asphaltene particles in oil. To this end, polarized light microscopy has been applied to determine the onset of asphaltene precipitation by titration of dead oil samples from Iranian crude oil reservoirs with n-heptane in the presence of nanofluids. Results show that rutile (TiO2) fine nanoparticles can effectively enhance the asphaltene stability in acidic conditions and act inversely in basic conditions. It was found that the required amount of n-heptane for destabilizing the colloidal asphaltene is considerably higher in presence of TiO2 nanofluids at pH below 4. The FTIR spectroscopy indicates changes in n-heptane insoluble asphaltene when acidic TiO2 nanofluid is used as inhibitor. According to the results obtained by FTIR spectroscopy, TiO2 nanoparticles can enhance the stability of asphaltene nanoaggregates through formation of hydrogen bond at acidic conditions. This is while other materials used in this experiment, as well as the TiO2 nanoparticles in basic conditions, are unable to form any hydrogen bond – hence their incapability to prevent asphaltene precipitation. Dynamic light scattering (DLS) measurements also have been performed to explain the mechanism of asphaltene precipitation in the presence of nanoparticles.
Wettability alteration is an important method to increase oil recovery from oil-wet carbonate reservoirs. Chemical agents like surfactants are known as wettability modifiers in carbonate systems. ...However, the effectiveness of these agents can be increased by the addition of chemicals such as polymers, ionic materials, and nanoparticles. The impacts of nanoparticles on the wettability of carbonate systems have not been reported yet, and it is still in its infancy. In this work, the effect of ZrO2-based nanofluids on the wettability alteration of a carbonate reservoir rock was experimentally studied. Several nanofluids were made composed of ZrO2 nanoparticles and mixtures of nonionic surfactants. The effect of nanofluids on the wettability of carbonate samples were investigated by measuring the contact angles, and it was shown that designed nanofluids could significantly change the wettability of the rock from a strongly oil-wet to a strongly water-wet condition. Scanning electron microscopy (SEM) images and X-ray Diffraction (XRD) data verify adsorption of nanoparticles on the rock and formation of nanotextured surfaces. Moreover, this paper reports the quick imbibitions of ZrO2 nanofluids into oil-wet core plugs saturated with stock tank oil. The results show that a considerable amount of oil can be quickly recovered by free imbibitions of the nanofluids into the core plugs. A theoretical approach is also presented to explain the wettability alteration by formation of composite nanotextured surfaces.
The present study reports on a green method for the fabrication of wound dressing loaded with Pistacia atlantica extract. The oil was extracted from P. atlantica plant using a solvent extraction ...process. The UV–vis spectroscopy showed that the phenolic compounds existed in the P. atlantica oil (PAO). The result of the antioxidant activity with the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay illustrated an IC50 value of 7.26 mg/ml, which indicated that the PAO was a significant source of natural antioxidants. Then, the PAO-loaded polyvinyl alcohol (PVA)-sodium alginate (SA) nanofibres were successfully produced using the electrospinning process. The results of field emission scanning electron microscopy showed that the addition of the PAO to the polymer solution increased the diameter of the fabricated nanofibres, while the optimum blending concentration of the PAO for obtaining the maximum scaffold stiffness was almost 1.5% (w/v). The physical properties of the fabricated nanofibres were evaluated using Fourier transform infrared spectroscopy, X-ray diffraction technique, and thermogravimetric-derivative and thermogravimetric analysis. The results showed that the PAO was bonded to the structure of the PVA/SA nanofibres, and the crystallinity, as well as the thermal stability of the fabricated nanofibres increased due to this attachment. In addition, the experiments showed that the PAO concentration in the structure of the fabricated nanofibres played a major role in the drug release rate, and increasing the PAO concentration from the optimum value decreased the controlled release of the drug. Last, based on the two-film theory, a mass transfer model was developed to predict the PAO released from the fabricated wound dressing.
•The P. atlantica oil was extracted with high antioxidant and healing properties.•The nanofibers loaded oil extract with optimum concentration were electrospun.•P. atlantica extract acts as a natural cross-linker and strengthens the nanofibers.•The extract release followed the developed model of two-film mass transfer.
Smart water injection is one of the engineering techniques to enhance oil recovery (EOR) from carbonate and sandstone reservoirs that have been widely used in recent decades. Wettability alteration ...and IFT are among the essential and influential mechanisms that can be mentioned to achieve EOR. One of the critical issues in the field of EOR is the effect of reservoir ions on the formation and stability of the emulsion. Investigating the role and performance of these ions during EOR processes is of significant importance. These processes are based on smart water injection and natural production. In this research, stability was investigated and formed during the injection of different concentrations of anionic and cationic surfactants, respectively alpha olefin sulfonate (AOS) and cetrimonium bromide (CTAB), into a water-oil emulsion with a volume ratio of 30-70. Considering the droplet diameter distribution and the flow speed of separation by centrifugation, the optimal concentration level has been investigated in both surfactants. Based on the results, the highest stability and emulsion formation occurred in the presence of AOS surfactant. Then different concentrations of CaCl
, MgCl
, and NaCl salts were added in optimal concentrations of both surfactants. The formation and stability of the emulsion was checked by examining the distribution of the droplet diameter and the separation flow rate. AOS anionic surfactant had the most stability in the presence of MgCl
salt, and better performance in stability of the emulsion was obtained. The maximum number of droplet diameters in the optimal concentration for AOS and CTAB surfactant systems is 1010 and 880, respectively, and for binary systems of AOS surfactant and MgCl
, CaCl
and NaCl salts, it is 2200, 1120 and 1110, respectively. Furthermore, for the CTAB binary system in the presence of MgCl
, CaCl
, and NaCl salts, it is 1200, 1110, and 1100, respectively. The stability of the emulsion of salts in the presence of both AOS and CTAB surfactants was MgCl2 > CaCl
> NaCl.
Hydrothermal liquefaction (HTL) is a green technology for biocrude production from algae. The global reaction kinetic, component additivity model (CAM), and response surface methodology (RSM) of HTL ...from high-lipid microalgae (Aurantiochytrium sp.) were evaluated. Lipids, proteins, and carbohydrates of the microalgae cell reacted at different rates and produced the aqueous phase, bio-oil, and gas phase in the kinetic model. Performing global kinetic modelling, understanding the reactions, and the performance of algae for biofuel production by HTL were the main ideas and novelty behind this work. Also, the predictive ability of bio-oil yield was examined by kinetic, CAM, and RSM approaches. MATLAB was utilized to solve the system of ordinary differential equations and calculate the optimum values for Arrhenius kinetic parameters by minimizing the least-square differences between model and experimental yields. R-squared of 0.997 showed that the global kinetic modelling provides a great prediction of bio-oil yields. Activation energies were calculated at 32.31, 38.50, and 46.99 kJ/mol for the conversion of lipids, proteins, and carbohydrates to bio-oil. Furthermore, a maximum bio-oil yield of 53.43 wt% was predicted at 800 K in 2 min. Also, the result of bio-oil prediction by global kinetic modelling compared to CAM and RSM equations. In comparison with the CAM model, the RSM equations showed better adaption with the bio-oil yield at 350 °C and 40 min. However, the kinetic model had the best potential for bio-oil predicting yields of Aurantiochytrium sp. because of the minimum mean absolute error of 2.078%.
Economic estimation of an environmental-friendly biomethanation process based on economic values of consumed and produced gases would be a unique attitude. In this paper, time and space dependent ...concentration profiles of components involved in a batch process, designed for biomethanation, were predicted through a mass transfer modelling. The reaction terms used in the modeling required bio-kinetic parameters of μ
max
, m, k
L
, Y
C/L
, Y
X/L
, and
Y
P/L
which were globally optimized via a predefined algorithm using some experimental data as 0.0987 day
1
, 0.1374 day
1
, 1.5422 mole m
−3
, 1.3636, 0.0183, 0.0908. Upon model verification, process income was calculated for a long-term scenario under a variety of factors and maximized through response surface methodology. The maximum income achieved was $-0.4/m
3
bioreactor. A term carbon subsidy was considered in the income equation in order to find a break-even income for subsidy value of $363/ton CO
2
. Sensitivity analysis revealed that the amount of carbon subsidy directly influenced the selection of low or high levels of some process parameters to make the process profitable. In addition, it was found that pressure and liquid volume were the most important factors to achieve maximum income when $30 and $300/ton CO
2
carbon subsidy were allocated to the process, respectively.
Diffusion of solvent gas in heavy oil and bitumen is essential in solvent-based heavy oil recovery. The pressure decay technique used for prediction of gas diffusion coefficient in heavy oil ignores ...the role of changes in gas compressibility factor and oil swelling. In this work, a numerical approach is proposed to model gas diffusion in bitumen from pressure decay data which includes all complexities due to oil swelling and gas compressibility factor. The proposed model was solved using differential quadrature element-incremental method. Results showed that changes in gas compressibility factor and swelling factor are significant and cannot be overlooked while interpreting pressure decay data. For diffusion of gas in bitumen, swelling was more significant at upper sub-layers adjacent to the gas phase. Also, swelling is more pronounced in the upper bitumen layers in contact with gas and stabilizes at later times when the gas concentration reaches equilibrium at the interface.
In the last two decades, researchers have attempted to use environmentally friendly pigments and porous nanostructures as sensitizers and semiconductors in dye-sensitized solar cells (DSSCs), ...respectively. In this study, the pigments were extracted from black plums (Syzygium cumini) to increase the biocompatibility of the DSSCs. The UV–vis spectroscopy of the extracted solution revealed the existence of anthocyanin pigments. The cyclic voltammetry measurement showed that the pigment energy levels were suitable for electron transfer to the TiO2 semiconductor, and the pigment electrochemical properties were also comparable with the commercial synthetic pigments. The dynamic light scattering experiment and zeta potential measurement illustrated that the size and electrostatic potential of the pigments were 0.3 nm and ±5 mV, respectively. These data confirmed the potential of the pigments for the diffusion into the porous structure of the TiO2 semiconductor and attraction as a shell layer on its surfaces. Besides, the TiO2 pastes were produced with seven different methods and characterized using XRD, SEM, and BET experiments. The results showed that the morphology, particle size, porosity, and surface area of the produced nanostructures were different in each method. Finally, the pastes were coated on the glass, sensitized with the extracted natural pigments, and used in the fabricated DSSCs. The efficiency of the cells was evaluated in the range of 0.027%–0.256% using the sun simulator technique. The results showed that the optimum particle size of the TiO2 semiconductor was around 25.6 nm which had been formed in the sixth method of the paste preparation.
Biomass (especially algae) is a renewable energy source that can be a great alternative to fossil fuels. Wet algal biomass converts into products such as solid, aqueous, and gaseous phases as well as ...biocrude in hydrothermal liquefaction (HTL). The aim of this work was to provide detailed exergy analyses of the production of biocrude from
Nannochloropsis
sp. by HTL. Physical and chemical exergy of the HTL products, exergy losses, exergy efficiency, and exergy distribution of the HTL process were determined in this research. The highest exergy loss and the lowest efficiency values obtained for the heat exchanger were 65,856.83 MJ/hr and 66.64%, respectively, which was mainly caused by the irreversibility of the heat transfer process. Moreover, the HTL reactor had high efficiency (99.9%) due to the complex reactions that occurred at high temperature and pressure. Also, the optimum operating conditions of the reactor were obtained at 350 °C and 20 MPa by using sensitivity analysis. The high overall exergy efficiency of the process (94.93%) indicated that HTL was the most effective process for the conversion of algae. In addition, the exergy recovery values of the overall exergy input values in the HTL process for biocrude, as well as the aqueous, solid, and gas phases, were nearly 74.88%, 18.42%, 0.86%, and 0.76%, respectively. Exergy assessment provides beneficial information for improving the thermodynamic performance of the HTL system.
A major part of world hydrocarbon resources is located in fractured reservoirs. The identification of fractured reservoir parameters is essential for their optimal production. The Warren-Root model ...is one of the most fundamental models for fluid flow in fractured reservoirs. The simplified assumption of the Warren-Root model is not applicable for a finite reservoir, and transition zone cannot be detected in finite fractured reservoirs. In this study, the significance of the fractured reservoir boundary effect in the Warren-Root equation is investigated. Also, the numerical solutions of the Warren-Root model are proposed for all types of boundary conditions. Results show that in some cases, it is impossible to diagnose the transition zone in fractured reservoirs from dimensionless curves due to the transition zone and boundary effect interference. This interference is specifically observed in finite fractured reservoirs and it is a function of the interprosity parameter (λ) and reservoir dimensionless radius (r
De
). This functionality is presented and discussed in the cases of constant production rate and constant pressure production conditions. The proposed equations are applicable to all types of boundary conditions.
