Showing papers in "Energy & Fuels in 2013"
TL;DR: In this paper, the adsorption of methane on a dry, organic-rich Alum shale sample was studied at pressures up to ∼14 MPa and temperatures in the range 300-473 K, which are relevant to gas storage under geological conditions.
Abstract: Shale gas is becoming an increasingly important energy resource. In this study, the adsorption of methane on a dry, organic-rich Alum shale sample was studied at pressures up to ∼14 MPa and temperatures in the range 300–473 K, which are relevant to gas storage under geological conditions. Maximum methane excess uptake was 0.176–0.042 mmol g–1 (125–30 scf t–1) for the temperature range of 300–473 K. The decrease in maximum methane surface excess with increasing temperature can be described with a linear model. An isosteric enthalpy of adsorption 19.2 ± 0.1 kJ mol–1 was determined at 0.025 mmol g–1 using the van’t Hoff equation. Supercritical adsorption was modeled using the modified Dubinin–Radushkevich and the Langmuir equations. The results are compared with absolute isotherms calculated from surface excess and the pore volumes obtained from subcritical gas adsorption (nitrogen (78 K), carbon dioxide (273 and 195 K), and CH4 (112 K)). The subcritical adsorption and the surface excess results allow an upp...
444 citations
TL;DR: In this paper, spontaneous imbibition of aqueous and oleic phases in several dry organic shale samples selected from two wells drilled in the Horn River basin was measured, and it was found that the impulsive water intake is due to the additional driving force provided through water adsorption by clay minerals.
Abstract: We measure spontaneous imbibition of aqueous (deionized water and KCl solutions of various concentrations) and oleic (kerosene and iso-octane) phases in several dry organic shale samples selected from two wells drilled in the Horn River basin. We find that the imbibition rate of aqueous phases is much higher than that of oleic phases even when plotted versus scaling dimensionless time, contrary to capillary-driven imbibition models. The observed difference is more pronounced in samples with higher clay content. The results suggest that the excess water intake is due to (1) the additional driving force provided through water adsorption by clay minerals, and (2) the enhancement of sample permeability through adsorption-induced microfractures.
432 citations
TL;DR: In this paper, the effect of nanofluids on wettability alteration was investigated by contact angle and imbibition tests, and it was shown that designed nanoftluids could significantly change the wettabil...
Abstract: Wettability alteration can occur at different stages during the producing life of a reservoir. Oil recovery from oil-wet reservoirs can significantly be increased by altering its wettability from an oil-wet to a strongly water-wet condition. Chemical agents such as surfactants are known as wettability modifiers in oil-wet systems. More recently, nanofluids prepared by dispersing nanoparticles in several liquid agents have been considered as potential wettability modifiers. In this work, the effectiveness of alumina-based nanofluids in altering the wettability of sandstone cores with an induced oil-wet wettability was experimentally studied. Eight nanofluids with different nanoparticles concentration, ranging from 100 ppm to 10000 ppm, were prepared by dispersing alumina nanoparticles in an anionic commercial surfactant. The effect of nanofluids on wettability alteration was investigated by contact angle and imbibition tests, and it was shown that designed nanofluids could significantly change the wettabil...
388 citations
TL;DR: In this article, a defect model based on low-temperature oxygen non-stoichiometry data is formulated and extrapolated to higher temperatures more relevant to thermochemical redox cycles.
Abstract: A thermodynamic and experimental investigation of a new class of solar thermochemical redox intermediates, namely, lanthanum–strontium–manganese perovskites, is presented. A defect model based on low-temperature oxygen non-stoichiometry data is formulated and extrapolated to higher temperatures more relevant to thermochemical redox cycles. Strontium contents of x = 0.3 (LSM30) and x = 0.4 (LSM40) in La1–xSrxMnO3−δ result in favorable reduction extents compared to ceria in the temperature range of 1523–1923 K. Oxidation with CO2 and H2O is not as thermodynamically favorable and largely dependent upon the oxidant concentration. The model is experimentally validated by O2 non-stoichiometry measurements at high temperatures (>1623 K) and CO2 reduction cycles with commercially available LSM35. Theoretical solar–fuel energy conversion efficiencies for LSM40 and ceria redox cycles are 16 and 22% at 1800 K and 13 and 7% at 1600 K, respectively.
354 citations
TL;DR: In this paper, the authors investigated how feedstock and pyrolysis conditions affect biochar characteristics, and investigated two woo-woo conditions, i.e., feedstock, pyrolysine, and carbon dioxide, for C sequestration and soil improvement.
Abstract: Biochar has been increasingly used as a method for C sequestration and soil improvement. To understand how feedstock and pyrolysis conditions affect biochar characteristics, we investigated two woo...
271 citations
TL;DR: In this paper, the effect of adding graphene nanoplatelets (GNPs) as thermally conductive nanofillers was investigated experimentally, and the composite PCM samples were prepared by dispersing GNPs in liquid eicosane at various loadings.
Abstract: Alkanes and their mixtures (paraffins) have widely been used as phase change materials (PCMs) for low-to-medium temperature thermal energy storage. Among the various alkanes, eicosane, with a nominal melting temperature of 37 °C, has emerged in energy-storage-based passive thermal management technologies, for electronics for example. In an effort to increase the thermal conductivity of eicosane, the effect of adding graphene nanoplatelets (GNPs) as thermally conductive nanofillers was investigated experimentally. The composite PCM samples were prepared by dispersing GNPs in liquid eicosane at various loadings (0, 1, 2, 5, and 10 wt.%) without any surfactants. Thermal conductivity of the composite PCM samples in their solid phase was then measured by means of the transient plane source technique at elevated temperatures from 10 to 35 °C. Latent heat of fusion and melting point of the samples were also characterized using a differential scanning calorimeter. It was shown that for the highest loading examine...
245 citations
TL;DR: In this article, an improved methodology of an electrically heated tube (1 mm i.d.), i.e., applying the variable reactor tube length to carry on thermal cracking of supercritical hydrocarbon aviation fuels as the electric current heating maintains constant, was proposed to experimentally obtain detailed information on the local concentration and temperature along the microchannels of a heat exchanger.
Abstract: Regenerative cooling with hydrocarbon aviation fuels on board is taken as a promising technology for the thermal management system of next-generation aircraft. An improved methodology of an electrically heated tube (1 mm i.d.), i.e., applying the variable reactor tube length to carry on thermal cracking of supercritical hydrocarbon aviation fuels as the electric current heating maintains constant, was proposed to experimentally obtain detailed information on the local concentration and temperature along the microchannels of a heat exchanger. For the first time a series of experimental data on detailed local chemical compositions of cracked hydrocarbon fuel along the cooling microchannels were reported under supercritical conditions (5 MPa, 680–700 °C), and the calculated thermodynamic properties, velocity, and residence times along the tube were also reported. A modified molecular reaction model consisting of 18 species and 24 reactions was developed to predict thermal cracking of hydrocarbon aviation fue...
245 citations
TL;DR: In this article, the authors address the question of timing of low salinity brine injection and the added benefit of polymer injection, and the main results are the oil recovery efficiencies of these two different flooding modes.
Abstract: Recently, low salinity brine injection has been given a great interest as a technique for enhanced oil recovery (EOR) by waterflooding. Varying experimental results have been reported in the literature, from many promising results to limited or no effects of low salinity. The application of low salinity water in combination with other established EOR processes (e.g., surfactant flooding and polymer flooding) is of great interest. The combined processes involve dampening capillarity to avoid trapping of mobilized oil, reducing residual oil saturation (Sor), and altering frontal stability and sweep. In this article, we address the questions of timing of LS injection and the added benefit of polymer injection. Secondary-mode (at initial water saturation) and tertiary-mode (after seawater residual oil saturation) low salinity waterflooding experiments were performed on outcrop Berea sandstone core material. The main results are the oil recovery efficiencies of these two different flooding modes. These results...
241 citations
TL;DR: In this paper, a 25 L vessel was used as a pretreatment for sewage sludge before incineration, and the composition and properties of the obtained hydrothermal carbonization coal and process water were studied.
Abstract: Hydrothermal carbonization (HTC) of stabilized and non-stabilized sewage sludge was investigated in a 25 L vessel as a pretreatment for sewage sludge before incineration, and the composition and properties of the obtained HTC coal and process water were studied. The observed values for H/C and O/C in HTC coal from stabilized and non-stabilized sewage sludge were shown to be higher than in natural coal and rather close to typical values for cellulose. The upper heating value of the stabilized sewage sludge was increased from 3.4 to 6.5%, and the upper heating value of the non-stabilized sludge was increased from 5.8 to 11.0%, after carbonization. The carbon efficiency ranged from 62 to 71% for stabilized sewage sludge and from 60 to 66% for non-stabilized sewage sludge, and the dry matter (DM) loss after carbonization was 31 and 42% for stabilized sludge and 34 and 44% for non-stabilized sludge. After carbonization, the mechanical dewaterability was increased from 30 to 70% DM content for non-stabilized sl...
236 citations
TL;DR: Anaerobic mono-and co-digestion of kitchen waste, corn stover and chicken manure under mesophilic (37 °C) conditions were conducted in batch mode with the aim of investigating the...
Abstract: Anaerobic mono- and co-digestion of kitchen waste (KW), corn stover (CS), and chicken manure (CM) under mesophilic (37 °C) conditions were conducted in batch mode with the aim of investigating the ...
222 citations
TL;DR: In this paper, the authors investigated the fast hydrothermal liquefaction of green marine alga Nannochloropsis sp. at batch reaction times of 1, 3, and 5 min and set-point temperatures of 300-600 °C.
Abstract: We investigated the fast hydrothermal liquefaction of green marine alga Nannochloropsis sp. at batch reaction times of 1, 3, and 5 min and set-point temperatures of 300–600 °C. We also performed conventional liquefaction for 60 min at the same temperatures. These experiments cover the broadest range of reaction conditions yet reported for algae liquefaction. The biocrude yield obtained for 1 min reaction times, which was only long enough to heat the reactor from room temperature to about half of the set-point temperature (in °C), increased with an increasing set-point temperature to 66 ± 11 wt % (dry and ash-free basis) at a set-point temperature of 600 °C. The biocrude obtained at this condition contains 84% of the carbon and 91 ± 14% of the heating value present in the dry algae feedstock. This biocrude yield and corresponding energy recovery are the highest reported for liquefaction of this alga. For a reaction time of 1 min, as the set-point temperature increases, light biocrude (e.g., hexane solubles...
TL;DR: In this paper, the structural parameters of nine coal samples from a contact metamorphic zone were studied by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD).
Abstract: The structural parameters of nine coal samples from a contact metamorphic zone were studied by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The FTIR spectra parameters composed of CH2/CH3, fa, Hal/Har, and (R/C)u indicate distinguishing features, including increase of aromaticity and the loss of aliphatic and oxygen-containing groups with thermally metamorphic evolution of coal. The XRD analysis shows that magmatic intrusion potentially caused rapid changes of structures in coal. With the decrease of distances from the intrusion rocks, the average lateral sizes (La), stacking heights (Lc), and interlayer spacing (d002) of the crystallite structures of coal range from 22.90 to 37.70 A, 12.90 to 23.30 A, and 3.80 to 3.50 A, respectively. Exponential correlations are observed between structural parameters (fa, d002, La, Lc, Hal/H, (R/C)u, and Aar/Aal) and C/H of the coal, suggesting that the structures of coal are controlled by the degree of contact metamorphism.
TL;DR: In this article, a middle-temperature coal tar and its fractions were characterized by gas chromatography-mass spectrometry (GC-MS) and negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometric (FT-ICR MS) with different ion transmission modes for high and low-mass ions.
Abstract: Coal tar has been considered as a potential energy alternative because of dwindling supplies of petroleum. To determine if the coal tar could be refined and upgraded to produce clean transportation fuels, detailed investigation of its composition is necessary, particularly for identifying the acidic components that account for about one-quarter of the weight of the coal tar. A middle-temperature coal tar (MTCT) and its fractions were characterized by gas chromatography–mass spectrometry (GC–MS) and negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with different ion transmission modes for high- and low-mass ions. Analytical results of narrow distillation fractions from FT-ICR MS agreed reasonably well with those from GC–MS, although each technique has its own advantages and disadvantages. In this work, FT-ICR MS was demonstrated to be capable of characterizing small molecules of <100 Da using appropriate operation conditions, thus yielding m...
TL;DR: In this article, a thermodynamic analysis of continuous fuel production by redox cycling of ceria in a single solar reactor under isothermal conditions is presented, and the influence of selected process parameters, including operating temperature, pressure and the effectiveness of heat recovery, on the solar-to-fuel conversion efficiency is determined.
Abstract: A thermodynamic analysis of continuous fuel production by redox cycling of ceria in a single solar reactor under isothermal conditions is presented. Ceria is partially reduced in a sweep gas flow of purified nitrogen and reoxidized with either steam or carbon dioxide to produce hydrogen or carbon monoxide, respectively. The sweep gas and oxidizer flows are preheated by the product gases. The influence of selected process parameters, including operating temperature, pressure, and the effectiveness of heat recovery, on the solar-to-fuel conversion efficiency is determined. For a solar concentration ratio of 3000, typical of state-of-the-art solar dish concentrators, and operating temperature of 1773 K, 95.5% of the available gas-phase heat must be recovered to reach conversion efficiencies of 10% and 18% for hydrogen and carbon monoxide production, respectively, assuming the flow rate of inert sweep gas is equivalent to that in a counter-current flow arrangement of gas and ceria. The efficiency depends stro...
TL;DR: In this article, the ReaxFF molecular dynamics simulation was employed to perform simulation of chemical reactions in pyrolysis of a bituminous coal model with 4976 atoms to examine the nascent decomposition mechanisms and product profiles at temperatures from 1000 to 2000 K over a 250 ps simulation period.
Abstract: Mechanisms investigation of coal pyrolysis will aid efficient and clean coal conversion and utilization. However, coal pyrolysis is a complex process involving myriad coupled reaction pathways such that the deeper understanding of its mechanism is still limited even with state-of-the-art experimental approaches. In this paper, ReaxFF molecular dynamics simulation was employed to perform simulation of chemical reactions in pyrolysis of a bituminous coal model with 4976 atoms to examine the nascent decomposition mechanisms and product profiles at temperatures from 1000 to 2000 K over a 250 ps simulation period. It is found that more than 900 reactions may occur at the temperature 2000 K within the simulation period with a trajectory output interval of 12.5 ps, and a detailed chemical reaction network was obtained by further analysis of the trajectory using a newly created C++ program. The product profile evolution tendency with temperature observed in the simulation agrees well with what was obtained experi...
TL;DR: In this article, a reduced PRF mechanism was proposed for combustion simulations of PRF and diesel/gasoline fuels based on the latest LLNL mechanism, which consists of 73 species and 296 reactions.
Abstract: A reduced PRF mechanism was proposed for combustion simulations of PRF and diesel/gasoline fuels based on the latest LLNL mechanism. The reduced PRF mechanism consists of 73 species and 296 reactions. The major reaction pathways of the detailed mechanism were mostly retained in the reduced mechanism, which ensures its predictive capability, the ability to be extended to other fuels, and the high computational efficiency of the reduced mechanism. The important reaction pathways and reactions in the reduced mechanism are identified and discussed. Furthermore, the reaction rates of two reactions, HO2 + OH = HO2 + O2 and HO2 + HO2 = H2O2 + O2, in the hydrogen submechanism are discussed and updated. The reduced mechanism was validated with measured ignition delays, laminar flame speeds, premixed flame species concentrations, jet stirred reactor and shock tube species profiles, and PRF fuel HCCI and PPCI combustion and diesel/gasoline direct injection spray combustion data. The reduced mechanism predicts well t...
TL;DR: In this paper, a co-gasification of switchgrass with coal and fluid coke was performed to investigate the availability of the gasification catalysts to the mixed feedstock, especially alkali and alkaline earth elements, naturally present on switchgrass.
Abstract: Co-gasification of biomass, namely, switchgrass, with coal and fluid coke was performed to investigate the availability of the gasification catalysts to the mixed feedstock, especially alkali and alkaline earth elements, naturally present on switchgrass. Rates of CO2 gasification of the single and mixed materials were measured at temperatures between 750 and 950 °C and atmospheric pressure by thermogravimetry. High interparticle mobility of the catalysts is indicated by a prompt and lasting effect on the mixed feed gasification rate when compared with the separate rates. The switchgrass–coal mixtures show a deactivation (antagonism), attributed to sequestration of the mobile alkali elements by reaction with aluminosilicate minerals in coal to form inactive alkali aluminosilicates, such as KAlSi3O8 and KAlSiO4. Remaining catalytic activity is evident when excess alkali is present in the feed mixture to satisfy the stoichiometric requirements of these deactivation reactions. In co-gasification of switchgras...
TL;DR: In this article, a catalytic-enhanced oil recovery method for Athabasca bitumen recovery through the viscosity reduction mechanism with the aid of trimetallic nanoparticles is presented.
Abstract: Many in situ recovery methods have been developed to extract heavy oil and bitumen from deep reservoirs. The “underground refinery” approach using a nanosize ultradispersed (UD) catalyst is one of the alternatives to surface upgrading that may become the “next generation” of oil sands industry improvement. Water-in-vacuum gas oil microemulsions containing trimetallic (W, Ni, and Mo) ultradispersed colloidal nanoparticles could penetrate inside the porous medium and react with the bitumen. This study is aimed at developing a catalytic-enhanced oil recovery method for Athabasca bitumen recovery through the viscosity reduction mechanism with the aid of trimetallic nanoparticles. In this study, series of experiments were conducted at a pressure of 3.5 MPa, residence time of 36 h, and temperatures from 320 to 340 °C in an oil sands packed bed column. Results of three consecutive categories of hot fluid injection (in the presence or absence of trimetallic nanoparticles) are presented. For the first category, th...
TL;DR: In this paper, a gap appears between the compositional space of asphaltenes and maltenes, in contradiction to the Boduszynski-Altgelt model, and a heavy distillate cut (atmospheric equivalent boiling point of 523-593 °C) is fractionated according to the number of aromatic rings by HPLC-2.
Abstract: Twenty-five years ago, Boduszynski et al. conducted a comprehensive study of heavy oil composition and concluded that crude oil composition increases gradually and continuously with regard to aromaticity, molecular weight, and heteroatom content from the light distillates to non-distillables (the Boduszynski continuum model). Previous exhaustive characterization of heavy vacuum gas oil by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) provided compositional data that strongly supports the continuum model. However, when the molecular formulas obtained by FT-ICR MS for the distillates and asphaltenes from the same parent crude oil are plotted as double bond equivalents (DBE) versus carbon number, a gap appears between the compositional space of “asphaltenes” and “maltenes”, in contradiction to the Boduszynski–Altgelt model. Here, a heavy distillate cut (atmospheric equivalent boiling point of 523–593 °C) is fractionated according to the number of aromatic rings by HPLC-2. The C7-dea...
TL;DR: In this paper, the authors investigated the interfacial behavior of asphaltene molecules at the oil-water interface using molecular dynamics simulations and found that a small amount of the molecules stacked their aromatic planes and formed a nanoscale aggregate, which exhibited an exotic molecular oscillation behavior.
Abstract: We have investigated the interfacial behavior of asphaltene molecules at the oil–water interface using molecular dynamics simulations. Oil precipitants and solvents are represented by heptane and toluene, respectively. It was found that asphaltenes are preferably distributed in the oil phase in the case of pure toluene, whereas they accumulate at the oil–water interface for pure heptane. Interestingly, the interfacial tension (IFT) of the interfacial system containing a small amount of asphaltene molecules is close to that of a pure heptane–water system, while the IFT of the system containing a large amount of asphaltene molecules is much reduced, ∼12 mN/m. Further, it was shown that the reduced IFT results from a complete asphaltene film formed at the oil–water interface when asphaltenes are abundant. In addition, it was found that a small amount of asphaltene molecules stacked their aromatic planes and formed a nanoscale aggregate, which exhibited an exotic molecular oscillation behavior of asphaltene m...
TL;DR: The Boduszynski model as discussed by the authors proposes a continuous progression in petroleum composition (molecular weight, structure, and heteroatom content) as a function of the atmospheric equivalent boiling point.
Abstract: Molecular characterization of asphaltenes by conventional analytical techniques is a challenge because of their compositional complexity, high heteroatom content, and asphaltene aggregate formation at low concentrations. Thus, most common characterization techniques rely on bulk properties or solution-phase behavior (solubility). Proposed over 20 years ago, the Boduszynski model proposes a continuous progression in petroleum composition (molecular weight, structure, and heteroatom content) as a function of the atmospheric equivalent boiling point. Although exhaustive detailed compositional analysis of petroleum distillates validates the continuum model, the available compositional data from asphaltene fractions supports the extension of the continuum model into the nondistillables only indirectly. Asphaltenes, defined by their insolubility in alkane solvents, accumulate in high-boiling fractions and form stable aggregate structures at low parts per billion (ppb) concentrations, far below the concentration...
TL;DR: An experimental and numerical study on laminar flame characteristics of methane oxy-fuel mixtures highly diluted with CO2 was conducted using a constant volume chamber and CHEMKIN package as mentioned in this paper.
Abstract: An experimental and numerical study on laminar flame characteristics of methane oxy-fuel mixtures highly diluted with CO2 was conducted using a constant volume chamber and CHEMKIN package. The effects of high CO2 dilution on combustion chemical reaction, flame instability, and flame radiation of CH4/CO2/O2 mixtures were studied. The laminar burning velocities of CH4/CO2/O2 mixtures decrease with the increase of the CO2 fraction. CO2 directly participates in the chemical reaction through the elementary reaction OH + CO = H + CO2 and inhibits the combustion process by the competition of the H radical between the reverse reaction of OH + CO = H + CO2 and the reaction H + O2 = O + OH. This effect is more obvious for highly diluted CO2 in the case of CH4/CO2/O2 mixtures. CO2 suppresses the flame instability by the combined effect of hydrodynamic and thermal-diffusive instabilities. The radiation of CH4 oxy-fuel combustion is much stronger than that of CH4/air combustion mainly because of the existence of a lar...
TL;DR: In this paper, a fast pyrolysis study on lignin and macroalgae (nonconventional biomass) and wood and straw (conventional biomasses) was carried out in a pyro-lysis centrifugal reactor at pyrolynomial temperature of 550 °C.
Abstract: A fast pyrolysis study on lignin and macroalgae (nonconventional biomass) and wood and straw (conventional biomass) were carried out in a pyrolysis centrifugal reactor at pyrolysis temperature of 550 °C. The product distributions and energy recoveries were measured and compared among these biomasses. The fast pyrolysis of macroalgae showed a promising result with a bio-oil yield of 65 wt % dry ash free basis (daf) and 76% energy recovery in the bio-oil while the lignin fast pyrolysis provides a bio-oil yield of 47 wt % daf and energy recovery in bio-oil of 45%. The physiochemical properties of the bio-oils were characterized with respect to higher heating value (HHV), molecular mass distribution, viscosity, pH, density, thermal behaviors, elemental concentrations, phase separation, and aging. The lignin and macroalgae oil properties were different compared to those of the wood and straw oils with respect to carbon and oxygen contents, HHV, thermal behaviors, and mean molecular weight. The HHV of wood, str...
TL;DR: In this article, a green chemistry route, Mn3O4/amorphous carbon nanoparticles have been synthesized, and the X-ray diffraction patterns reveal the Hausmannite tetragonal structure of the synthesized Mn 3O4 particles.
Abstract: Via the green chemistry route, Mn3O4/amorphous carbon nanoparticles have been synthesized. Dextrose was used as the reducing agent, and starch was used as the capping agent. The X-ray diffraction patterns reveal the Hausmannite tetragonal structure of the synthesized Mn3O4 particles. EDAX analysis confirms the presence of carbon and stoichiometry of Mn3O4. Morphological studies reveal the nanospherical nature of the synthesized particles. The FTIR spectra confirm the presence of Mn–O bonds. Mn3O4/AC 500 exhibits highest specific capacitance of 522 F g–1 at a specific current of 1 A g–1, when measured from the charge–discharge process. This value is superior to previous reports on Mn3O4 nanoparticles as an electrode for supercapacitors. Higher energy density of 58.72 W h kg–1 could be observed for Mn3O4/AC 500, which is higher than lead acid batteries and comparable to those for the nickel hydride batteries. These results indicate that Mn3O4/AC 500 is a promising electrode for supercapacitor applications.
TL;DR: In this article, the hygroscopicity of prepared torrefied pellets was evaluated in a humidity chamber by measuring the moisture uptake rate of control and Torrefied samples.
Abstract: Torrefied pellets, a transportable renewable energy source, have a higher energy density than the regular wood pellets (control pellets). The quality of torrefied pellets is determined mainly by the density, hardness, and the hygroscopicity or moisture uptake. In this study, the density and the hardness of torrefied pellets were systematically examined by using torrefied samples prepared at different conditions in a press machine. The hygroscopicity of prepared torrefied pellets was evaluated in a humidity chamber by measuring the moisture uptake rate of control and torrefied pellets. The results showed that the density and the hardness of torrefied pellets mainly depended on the densification die temperature and the weight loss of torrefied samples. To make strong torrefied pellets of high density and low moisture uptake from 30 wt % weight loss torrefied samples, a die temperature of 230 °C or above was needed. Preconditioning torrefied samples to a moisture content of ∼10% can improve the quality of to...
TL;DR: In this paper, the authors examined stacked oil reservoirs in an oilfield in Saudi Arabia using simple predictions from the Flory-Huggins-Zuo equation of state (FHZ EoS), with its foundation in the Yen-Mullins model.
Abstract: Many studies have indicated that asphaltenes have two hierarchical nanocolloidal species, the nanoaggregate and the cluster of nanoaggregates. These two species, along with the dominant molecular architecture of asphaltenes comprise the Yen–Mullins model of asphaltenes. Delineating different nanocolloidal species is a challenge, and moreover, elucidating their corresponding practical importance is a necessity in this applied science. Moreover, it is necessary to continue testing this asphaltene nanoscience model especially for crude oils, as opposed to simply asphaltene solutions in laboratory solvents. Both the validity and applicability of this model are addressed by observing gravitational gradients of asphaltenes in black oil and mobile heavy oil columns in oilfield reservoirs. In this paper, we examine stacked oil reservoirs in an oilfield in Saudi Arabia using simple predictions from the Flory–Huggins–Zuo equation of state (FHZ EoS), with its foundation in the Yen–Mullins model. The extraordinary fi...
TL;DR: In this article, the authors identify chemicals that can be added to the injection water that can induce imbibition into an originally mixed-wet, tight, fractured sandstone reservoir.
Abstract: In fractured reservoirs, the efficiency of water flood is governed by spontaneous imbibition of water into oil-containing matrix blocks. When the matrix is oil-wet or mixed-wet, little oil can be recovered by imbibition. The objective of this work is to identify chemicals that can be added to the injection water that can induce imbibition into an originally mixed-wet, tight, fractured sandstone reservoir. Several surfactants were evaluated for their aqueous stability at the reservoir temperature and salinity. Contact angles were measured on a clay-rich sandstone. Spontaneous imbibition tests were conducted on the reservoir rocks. It is shown that the use of dilute (0.1 wt %) anionic surfactant solution with a large number of ethoxy groups can alter the wettability from oil-wet toward more water-wet conditions on the mineral plates. Incremental oil recovery as high as 68% original oil in place is obtained through spontaneous imbibition experiments performed on tight (∼10 μD) oil-wet/mixed-wet sandstone res...
TL;DR: In this article, asphaltene deposits were generated in metal capillaries by heptane addition to crude oils, and it was found that deposition is caused by submicrometer aggregates.
Abstract: Asphaltenes are a solubility class of petroleum crude oil that can destabilize and deposit in both upstream and downstream processes. In this study, asphaltene deposits were generated in metal capillaries by heptane addition to crude oils, and it was found that deposition is caused by submicrometer asphaltene aggregates. Deposits were generated at heptane concentrations above and significantly below the instantaneous onset point. Analysis of the results reveals that the governing factor controlling the magnitude of asphaltene deposition is the concentration of insoluble asphaltenes present in a crude oil-precipitant mixture and the instantaneous onset point is irrelevant to the deposition process. Electron microscopy images of the deposits represent the first images and confirmation of arterial growth in laboratory generated asphaltene deposits. The axial deposit profile was found to be highly nonuniform. In addition, deposits formed shortly after when oil and heptane mix, revealing that the destabilizati...
TL;DR: In this paper, the effects of process parameters including pressure, reaction temperature, holding time, and feedstock particle size on the yield and properties of the solid products of the typical Norwegian biomass fuels were investigated within the temperature window of 175-225 °C.
Abstract: Wet torrefaction of typical Norwegian biomass fuels was studied within the temperature window of 175–225 °C, using a benchtop autoclave reactor of 250 mL in volume from Parr Instrument. Two types of local biomass fuels were employed as feedstock, Norway spruce (softwood) and birch (hardwood). Effects of process parameters including pressure, reaction temperature, holding time, and feedstock particle size on the yield and properties of the solid products were investigated. It appears that birch wood is more reactive and produces less solid products than spruce wood in the same wet torrefaction conditions. Increasing pressure above the saturated vapor pressure of water enhances the torrefaction rate. Both reaction temperature and holding time have significant effects on solid product yield and fuel properties of wet torrefied biomass. The yield of solid products is slightly reduced with decreasing feedstock particle size. The ash content of biomass fuel is significantly reduced by wet torrefaction. In addit...
TL;DR: In this paper, different numbers of peaks from three to as many as five curves with combined Lorentzian and Gaussian bands were fitted for the spectra, and Raman parameters were compared with soot oxidative reactivity.
Abstract: Soot crystalline structure was evaluated for four soot samples and one carbon black using Raman parameters obtained from first-order Raman spectra. For this work, different numbers of peaks from three to as many as five curves with combined Lorentzian and Gaussian bands were fitted for the spectra, and Raman parameters were compared with soot oxidative reactivity, in order to investigate the correlation between the Raman parameters and the oxidative reactivity for each curve-fitting method. Among these methods, the combination of three Lorentzian-shaped bands at about 1200 (D4), 1360 (D1), and 1580 cm–1 (G), and one Gaussian-shaped band at about 1500 cm–1 (D3), which is designated as 3L1G, shows the most consistent results for various Raman parameters with respect to soot oxidative reactivity; amorphous carbon fraction, crystallite size, and distribution of crystallite size are in good agreement with soot oxidative reactivity. Also, crystallite sizes from several empirical formulas using Raman spectroscop...