Improved thermal model considering hydrate formation and deposition in gas-dominated systems with free water Fuel (IF 4.908) Pub Date : 2018-09-21 Zhiyuan Wang, Jing Yu, Jianbo Zhang, Shun Liu, Yonghai Gao, Hua Xiang, Baojiang Sun
The accurate prediction of temperature is the basis for predicting hydrate formation. Presently available methods for the calculation of temperature distributions in pipelines are based solely on the traditional heat transfer mechanism between the high-temperature fluid in the pipeline and the low-temperature surroundings. The influences of hydrate formation and deposition behaviors on the temperature variation have not been considered in the heat transfer process. Hydrate formation is exothermic, and the hydrate layer formed by the deposition of hydrates has a resistance effect to the heat transfer process. In this study, an improved thermal model for predicting the temperature distribution in gas-dominated systems is proposed. In this model, the influences of hydrate formation and deposition behaviors on the variation in temperature are considered. The model is verified by comparing with experimental data from literature. The transient variation in temperature along the pipeline can be obtained using the model. The simulation results indicate that hydrate formation and deposition have a significant influence on the variation in temperature in the pipeline, and can cause an inhibiting effect on the later hydrate formation. This work adds further insight into the heat transfer process and can serve as useful reference for the accurate prediction of temperature distributions in pipelines.
A comparison of the NaOH-HCl and HCl-HF methods of extracting kerogen from two different marine oil shales Fuel (IF 4.908) Pub Date : 2018-09-21 Jameel S. Aljariri Alhesan, Mohammad W. Amer, Marc Marshall, W. Roy Jackson, Thomas Gengenbach, Ying Qi, Martin L. Gorbaty, Peter J. Cassidy, Alan L. Chaffee
Pretreatment of lignite by acidic bronsted ionic liquid [B(SO3H)mim]OTf for lignite pyrolysis Fuel (IF 4.908) Pub Date : 2018-09-21 Wenhao Yu, Hao Zhang, Zhiping Lei, Hengfu Shui, Shigang Kang, Zhicai Wang, Shibiao Ren, Chunxiu Pan
The effect of pretreatment with acidic bronsted ionic liquid 1-sulfonic acid butyl-3-methylimidazolium trifluoromethanesulfonate ([B(SO3H)mim]OTf) on Shengli lignite (SL) pyrolysis behavior and its pyrolysis products distribution were investigated in this paper. In order to study the mechanism of [B(SO3H)mim]OTf pretreatment on the dissolution of SL, [B(SO3H)mim]OTf treated-SL was also analyzed by the Fourier Transform Infrared Spectroscopy (FTIR), Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFT) and TG-DTG. It is found that the pretreatment temperature and the ratio of [B(SO3H)mim]OTf to SL have a significant impact on the pyrolysis of SL. The pretreatment of SL with [B(SO3H)mim]OTf can not only result in the increase of the yield of total tar and light oil fraction but also improve the quality of tar. After the pretreatment at 200 °C and [B(SO3H)mim]OTf/SL at 1, the tar yield, light fraction content, arenes, and phenolics content in tar is 1.6, 2.4, 6.3 and 3.2 times higher than that from raw SL pyrolysis, respectively. Pretreatment with [B(SO3H)mim]OTf leads to the fracture of the coal network, resulting in the increase of the content of CO and COC bonds and the disruption of hydrogen bonds.
Flow regimes during surfactant flooding: The influence of phase behaviour Fuel (IF 4.908) Pub Date : 2018-09-21 Yara A. Alzahid, Peyman Mostaghimi, Stuart D.C. Walsh, Ryan T. Armstrong
Surfactant flooding is one of the most widely adopted enhanced oil recovery strategies whereby microemulsion is formed in situ during immiscible displacement. It is expected that local equilibrium is achieved during surfactant flooding and that resulting microemulsion phase properties directly influence the flow physics and thus, oil recovery. We consider phase behaviour of a surfactant–oil–water system that can form either Winsor type II−, III or II+ microemulsion. Water, polymer and Winsor type surfactant solutions are injected into oil saturated polydimethylsiloxane microfluidic chips and imaged under continuous flow at various Capillary numbers and Viscosity ratios. Images are analysed for displacement patterns and oil recovery. Flow regimes are explained by considering the equilibrium interfacial tension (IFT) and viscosity of the formed microemulsion phase. Displacement of oil by injected fluids was dominated by capillary fingering at low flow rates. At higher flow rates, type III microemulsion develops viscous fingering while type II− develops stable displacement due to the microemulsion phases being of high and low viscosity, respectively. This report highlights that the difference between stable/unstable displacement during surfactant flooding is influenced by surfactant–oil–water phase behaviour.
Interaction of two drops in the bag breakup regime by a continuous air jet Fuel (IF 4.908) Pub Date : 2018-09-21 Hui Zhao, ZhaoWei Wu, WeiFeng Li, JianLiang Xu, HaiFeng Liu
Fuel atomization characteristics are important in the performance of gasification and combustion. This work concerns the interaction of two drops in a continuous air jet stream. Morphological classifications of interaction modes have been analyzed using high speed camera. Behaviors of drops group and the isolated drop in the airflow are significantly different. Experimental photos show that there are four main interaction modes, which are coalescence mode, puncture mode, side by side mode and no direct contact mode. Influence of dimensionless distance on drops interaction mode is researched. Then the drops interaction regime map is obtained. The model prediction is in good agreement with the experimental results. The total dimensionless breakup time of puncture mode is the longest, then the coalescence mode, and the third the side by side mode. Results present an evaluation of the role of proximity to other drops in affecting the outcome, which are useful in understanding atomization mechanism and improving simulation model.
Accumulation behaviors of methane in the aqueous environment with organic matters Fuel (IF 4.908) Pub Date : 2018-09-20 Zheng Li, Jun Yao, Zhijun Ren, Hai Sun, Lei Zhang, Yongfei Yang, Jintu Fan, Jianlong Kou
Using fieldable spectrometers and chemometric methods to determine RON of gasoline from petrol stations: A comparison of low-field 1H NMR@80 MHz, handheld RAMAN and benchtop NIR Fuel (IF 4.908) Pub Date : 2018-09-20 Melanie Voigt, Robin Legner, Simon Haefner, Anatoli Friesen, Alexander Wirtz, Martin Jaeger
The Research Octane Number (RON) still is the major physical quantity for the characterization of fuels. Spectroscopy and multivariate data analyses have proven themselves alternatives to the traditional CFR motor. Yet, the utilization of handheld or fieldable instruments has been rarely reported rendering the feasibility of fast and simple near-pump RON determination debatable. In this study, the applicability of a handheld Raman and a portable 1H NMR spectrometer in combination with chemometrics is demonstrated on a laboratory sample training set and compared to NIR spectroscopy. Qualitative classification of a fuel sample is achieved through Principal Component Analysis. The performance of the fieldable spectrometers using Support Vector Regression for RON prediction is found at least equivalent to earlier studies with more sophisticated and expensive instruments. The analytical method and the validated qualitative and quantitative models are then applied to samples from gas stations. The goodness of the method is expressed both in terms of computational residual mean squared errors and the common experimental reproducibility and repeatability limits. Depending on the method 40–50% of the samples are predicted within 0.2 and 80–90% with 0.7 RON.
Influence of temperature and gas residence time on the formation of polycyclic aromatic hydrocarbons (PAH) during the pyrolysis of ethanol Fuel (IF 4.908) Pub Date : 2018-09-20 F. Viteri, A. López, Á. Millera, R. Bilbao, M.U. Alzueta
The effect of temperature and gas residence time on the formation of 16 priority PAH from the ethanol pyrolysis, in the 975–1475 K temperature range, has been evaluated. Soot was quantified by weight difference of the collection filter and light gases were measured by gas chromatography and microchromatography. The PAH quantification was done by gas chromatography–mass spectrometry (GC–MS). The toxicity of the effluent was determined by the B[a]P-eq value with the concentration of the PAH found during the experiments. The principal results show that the PAH concentration presents a maximum with the temperature, which is shifted to lower temperatures as the gas residence time increases. The PAH with the highest concentration are: NAPH, ACNY, PHEN, FANTH and PYR, and they are mainly present adsorbed on soot. The highest toxicity, B[a]P-eq, of the effluent was found for the highest residence time, tr(s) = 4168/T (K), particularly on soot.
Atomization characteristics of nano-Al/ethanol nanofluid fuel in electrostatic field Fuel (IF 4.908) Pub Date : 2018-09-20 Shengji Li, Zhu Zhuo, Lanjiao He, Xuefeng Huang
Direct and simultaneous determination of four phenolic antioxidants in biodiesel using differential pulse voltammetry assisted by artificial neural networks and variable selection by decision trees Fuel (IF 4.908) Pub Date : 2018-09-20 Lívia de Souza Schaumlöffel, Jônathan William Vergani Dambros, Pedro Rafael Bolognese Fernandes, Mariliz Gutterres, Clarisse Maria Sartori Piatnicki
Effect of chemical additives on hard deposit formation and ash composition in a commercial circulating fluidized bed boiler firing Korean solid recycled fuel Fuel (IF 4.908) Pub Date : 2018-09-20 Jae Hyeok Park, Dong-Ho Lee, Keun-Hee Han, Jong-Seon Shin, Dal-Hee Bae, Tae-Earn Shim, Jeong Hwan Lee, Dowon Shun
Combustion of SRF (solid recycled fuel) and biomass with potassium (K), sodium (Na), and chlorine (Cl) contents can result in operational problems such as hard deposit formation and convection pass tube corrosion. Two types of commercially available chemical additives, ammonium sulfate [(NH4)2SO4] and borax solution, were examined to elucidate their effect on hard deposit formation and the particle composition of fly ash on the convection pass of a commercial CFBC (circulating fluidized bed combustion) boiler. The addition of ammonium sulfate/borax solution hindered metal chloride formation and reduced the amount of hard deposit formation on the convection pass tubes. Both the alkali and potassium chloride content and the point load hardness of the hard deposit were reduced, while the melting temperature increased according to the borax solution use. When chemical additives were employed, the particle size distribution of the fly ash shifted to coarse particles. In particular, SEM (scanning electron microscopy) images of the fly ash particles revealed the attachments of fine particles to the ash particles. These were assumed to be mineral salts attached to the coarse particles, which increased the overall particle size distribution.
Exploring the potential of reformed-exhaust gas recirculation (R-EGR) for increased efficiency of methanol fueled SI engines Fuel (IF 4.908) Pub Date : 2018-09-20 Duc-Khanh Nguyen, Louis Sileghem, Sebastian Verhelst
Methanol is a promising fuel for spark ignition engines because of its high octane number, high octane sensitivity, high heat of vaporization and high laminar flame speed. To further boost the efficiency of methanol engines, the use of waste heat for driving fuel reforming was considered. This study explores the possibility of the reformed-exhaust gas recirculation (R-EGR) concept for increased efficiency of methanol engines. A simple Otto cycle calculation and a more detailed gas dynamic engine simulation are used to evaluate that potential. Both methodologies point to an enhancement in engine efficiency with fuel reforming compared to conventional EGR but not as much as the increase in lower heating value of the reforming product would suggest. A gas dynamic engine simulation shows a shortening of the flame development period and the combustion duration in line with the expected behavior with the hydrogen-rich reformer product gas. However, the heat loss increases with the presence of hydrogen in the reactants. The improvement of brake thermal efficiency is mainly attributed to the reduction of pumping work. The R-EGR concept is also evaluated for ethanol and iso-octane. As the reforming fraction increases, the efficiency of ethanol and iso-octane fueled engines rises faster than for the methanol engines due to a higher enhancement of exergy in their reforming products. At high reforming fractions, the efficiency of the ethanol engine becomes higher than with methanol. However, if the impact of optimal compression ratio for different fuels are considered, the methanol engine is able to produce a higher efficiency than the ethanol engine.
Simulation and life cycle assessment of synthetic fuels produced via biogas dry reforming and Fischer-Tropsch synthesis Fuel (IF 4.908) Pub Date : 2018-09-20 Zaira Navas-Anguita, Pedro L. Cruz, Mario Martín-Gamboa, Diego Iribarren, Javier Dufour
This article addresses the simulation and life cycle assessment of a biogas-to-liquid plant for the coproduction of synthetic fuels (diesel and gasoline) and electricity. The system comprises a biogas dry reforming process to produce syngas, Fischer-Tropsch synthesis, and a combined-cycle process. A detailed reaction model of the dry reforming process is implemented in the simulation of the system in Aspen Plus®. Inventory data obtained mainly through process simulation are used to evaluate the environmental performance of the system in terms of global warming, cumulative non-renewable energy demand, ozone layer depletion, acidification, and eutrophication. In particular, the life-cycle environmental profile of synthetic biodiesel as the main product of the biogas-to-liquid plant is calculated and compared with that of conventional diesel. Overall, the performance of the synthetic biodiesel product is not found to be environmentally favourable, which suggests the need for further optimising the biogas-to-liquid system to make it competitive with conventional systems. In this sense, biogas production and direct emissions to the air from the biogas-to-liquid plant arise as the main sources of impact.
Laser spectroscopic investigation of diesel-like jet structure using C8 oxygenates as the fuel Fuel (IF 4.908) Pub Date : 2018-09-20 Thomas Raffius, Tamara Ottenwälder, Christian Schulz, Gerd Grünefeld, Hans-Jürgen Koß, Stefan Pischinger
Di-n-butyl ether (DNBE) and n-octanol have very low sooting tendencies in diesel-like combustion, as demonstrated in previous engine studies. This finding is not fully understood for pure DNBE, because it has a very high cetane rating (∼100). In order to investigate the underlying mechanisms, the structure of diesel-type jets is analyzed by a number of optical diagnostics, such as spontaneous Raman scattering (SRS), laser-induced fluorescence (LIF), OH* luminescence imaging, Mie scattering, and shadowgraphy. Pure DNBE and a tailor-made blend of 50% DNBE and 50% n-octanol as well as neat n-heptane are used as the fuel in separate experiments. The jets are probed in a simulated engine-like environment in a high-pressure combustion vessel. In particular, the inner flame structure is analyzed by SRS and LIF. This yields information on the local temperature and the concentrations of O2, CO, and polycyclic aromatic hydrocarbons (PAH). For the first time, O2 is quantitatively detected in the core of a diesel-like flame by resonance-enhanced SRS. Thereby, air entrainment into the inner flame core is assessed. Results show that air entrainment is particularly strong for pure DNBE, explaining its high soot oxidation rate and overall low sooting tendency. High entrainment is primarily attributed to the low heat-release rate of DNBE, which is likely an effect of its high ignitability. Thus, it can be concluded that the high cetane rating of pure DNBE does not only lead to relatively poor pre-combustion mixture preparation and consequently considerable soot formation but seemingly also to particularly strong soot oxidation. Moreover, the jet structure turns out to be very similar for the DNBE/n-octanol blend and neat n-heptane, indicating that the net effect of volatility and fuel oxygenation is weak.
Screening of protic ionic liquids for sugarcane bagasse pretreatment Fuel (IF 4.908) Pub Date : 2018-09-20 Thaynara C. Pin, Pedro Y.S. Nakasu, Silvana Mattedi, Sarita C. Rabelo, Aline C. Costa
Protic ionic liquids have been demonstrated to be a promising alternative for the pretreatment of lignocellulosic biomasses, since they can provide higher enzymatic hydrolysis yields than other commonly used pretreatments. In this study, eleven protic ionic liquid — each one a combination of acetic or sulfuric acid with various amines — were evaluated as pretreatment agents. The highest glucose and xylose yields in the enzymatic hydrolysis were observed using the ionic liquids with acetic acid, and the best performance in the acetate anion group was obtained with N-methyl-2-hydroxyethylammonium acetate, [Me(NH2)(CH2)2OH] [OAc], 72% and 45.9% of glucose and xylose yields, respectively, in 48 h, 10% (w/w) solids loading and enzyme loading of 15 FPU·g−1 bagasse.
Microbial removal of sulphur from petroleum coke (petcoke) Fuel (IF 4.908) Pub Date : 2018-09-20 Nimisha Tripathi, Raj S. Singh, Colin D. Hills
Characterization of pyrolysis products from slow pyrolysis of live and dead vegetation native to the southern United States Fuel (IF 4.908) Pub Date : 2018-09-20 Elham Amini, Mohammad-Saeed Safdari, Jonathan T. DeYoung, David R. Weise, Thomas H. Fletcher
The influence of CO2 on the structure of confined asphaltenes in calcite nanopores Fuel (IF 4.908) Pub Date : 2018-09-20 Sohaib Mohammed, Greeshma Gadikota
The effect of CO2 injection on the structure and transport properties of confined asphaltenes in 6 nm slit-shaped calcite nanopore was studied using molecular dynamics simulations. The difference between asphaltene behavior in confined and bulk fluids in the presence of CO2 were investigated. A higher number of CO2 molecules in confinement influenced the anisotropic distribution of the confined hydrocarbons by displacing the adsorbed hydrocarbons molecules away from the pore surface toward the center of the pore. The van der Waals and electrostatic affinity of toluene and asphaltene with calcite surface decreased with an increase in the CO2 mole fraction. Increase in the number of CO2 molecules in confinement enhanced the tendency of asphaltenes to form aggregates. Further, the diffusivities of hydrocarbons were influenced by the density of injected CO2 and were found to vary anisotropically in the calcite nanopores. The aggregation of asphaltenes in the absence of confinement is faster as opposed to being in confinement. The enhanced adsorption of CO2 to the pore surface reduces the concentration of CO2 in the center of the pore resulting in slower aggregation of asphaltenes in confinement. These results suggest that developing a fundamental understanding of asphaltene behavior in confinement is essential for developing more robust predictions of field-scale observations of asphaltene aggregation.
Investigations on spontaneous imbibition and the influencing factors in tight oil reservoirs Fuel (IF 4.908) Pub Date : 2018-09-20 Wang Jing, Liu Huiqing, Qian Genbao, Peng Yongcan, Gao Yang
Spontaneous imbibition has become a role on the development of tight oil reservoirs. Many oilfield cases have confirmed the validity of soaking to produce oil depending on imbibition. Considerable yield has been recovered from soaking for a period of time after hydraulic fracturing by fracturing fluid. In order to study the spontaneous imbibition and its influencing factors in tight oil reservoir with stimulated reservoir volume (SRV), we first conducted wettability and imbibition experiments with/without surfactant treatment using different tight cores. Then, we established a mechanism model of imbibition including the influencing factors in tight oil reservoirs based on the experiments. The model was also validated using the published results. After that, numerical simulation was employed to study the impacts of some essential factors on the effects of spontaneous imbibition. The results indicate that no matter mixed-wet or water-wet tight cores, water can be spontaneously imbibed into the tight cores, and consequently expel the oil. The wettability alteration agent has slight influence on contact angle and imbibition recovery for the water-wet core, but it has a distinct influence on those of the mixed-wet or oil-wet core. Natural fractures in tight rock can promote the imbibition. The size of the tight rock after hydraulic fracturing is a significant factor of imbibition recovery. Interfacial tension is crucial to imbibition in tight reservoir because capillary force becomes more significant in tight rocks than that in conventional reservoirs. Wettability intensely decides the imbibition recovery, and it is indispensable to add modifying agents to enhance imbibition for mix-wet or oil-wet rocks. The reduction of temperature in tight oil reservoir due to fracturing and huff-n-puff may decrease the recovery by more than 1% after 5–6 cycles.
Characterization and evaluation of synthetic Dawsonites as CO2 sorbents Fuel (IF 4.908) Pub Date : 2018-09-20 Fredrik Lundvall, Georgios N. Kalantzopoulos, David S. Wragg, Bjørnar Arstad, Richard Blom, Anja O. Sjåstad, Helmer Fjellvåg
Performance evaluation of CO2 flooding process in tight oil reservoir via experimental and numerical simulation studies Fuel (IF 4.908) Pub Date : 2018-09-19 Xiang Zhou, Qingwang Yuan, Yizhong Zhang, Hanyi Wang, Fanhua Zeng, Liehui Zhang
In this study, experimental and numerical simulation studies were conducted to enhance oil production in a tight oil reservoir using CO2 injection processes. In experimental studies, three types of CO2 injection experiments—CO2 flooding (continuous CO2 injection process), CO2 flooding coupled with a soaking period, and CO2 flooding coupled with pressure maintenance—were carried out in one-meter-long core plugs to investigate the effect of CO2 flooding schemes on production performance. The properties of light oil–CO2 systems with different CO2 concentrations under different pressures were measured to study the phase behaviors of light oil–CO2 systems. Test results indicate that the CO2 flooding process is the best method to enhance oil recovery in tight formations, showing an oil recovery factor of 38.96% and a CO2 utilization of 10.41 Mscf/STB. In numerical simulation study, the properties of light oil–CO2 systems first were simulated using the WinProp module. Next, the GEM module was applied to implement history-matching studies on experimental results, and good agreement was achieved. Third, a sensitivity analysis was carried out to investigate the effect of parameters on the CO2 flooding process. Finally, upscaling simulation studies were conducted at the field scale to optimize the well pattern and CO2 injection rate to enhance oil recovery in the target reservoir. Important correlations on the effect parameters were generated for predicting the oil production performance in the reservoir with different operations. Among the studied well patterns, the inverted seven-spot well pattern with a CO2 injection rate of 44.28 t/day/well achieved the best production performance in the field study. In the optimized case, the oil recovery factor reached 30.89% with a low CO2 utilization of 5.69 Mscf/STB.
Deep and fast oxidative desulfurization of fuels using graphene oxide-based phosphotungstic acid catalysts Fuel (IF 4.908) Pub Date : 2018-09-19 Azam Khodadadi Dizaji, Babak Mokhtarani, Hamid Reza Mortaheb
Experimental investigation of CO2 injection into coal seam reservoir at in-situ stress conditions for enhanced coalbed methane recovery Fuel (IF 4.908) Pub Date : 2018-09-19 Zhengdong Liu, Yuanping Cheng, Yongkang Wang, Liang Wang, Wei Li
CO2 geological sequestration is an effective method to reduce the concentration of CO2 in the atmosphere. The injection of CO2 into CH4-containing coal seams also named CO2-ECBM (CO2 Enhanced Coalbed Methane Recovery), allows the storage of CO2 and the enhancement of CH4 recovery. Due to complex geological environment of the site, dynamic variation of CH4 and CO2 can hardly be monitored in real time during CO2 injection into coal seams. Therefore, this paper conducted experimental studies were carried out on cuboid coal samples with a size of 300 ∗ 70 ∗ 70 mm via a self-developed experimental device which can simulate in-situ stress and temperature conditions. In the experiment, different adsorbed gases (CH4 and CO2) were applied to determine the variation of permeability values under various load stresses and pore pressures. Results proved that the coal had greater adsorption capacity to CO2 than to CH4. The injected CO2 occupied the original adsorption site of CH4, thus leading to the rapid discharge of CH4. Meanwhile, real-time dynamic monitoring was also performed on gas parameters in coal under different gas injection pressures to obtain variation laws of pore pressure, gas flow rate and concentration at the outlet with the increment of injected CO2. The results reveal that with the increase of injected CO2, pore pressure tended to equilibrium while CH4 flow rate and concentration at the outlet gradually fall to zero. Therefore, CO2 injection into the coal mass can effectively improve the recovery of CH4. In addition, variations of gas flow rate and concentration at the outlet with the displacement ratio of gas volume under different gas injection pressures suggested that the enhancement of gas injection pressure boosted discharge efficiency of CH4 from the coal mass and CO2 consumption. Furthermore, inspired by the competition relationship between engineering efficiency and CO2 consumption, we think a reasonable and effective economic cost model can be established as an effective method to guide the selection of gas injection pressure in the future. Hence, the experimental results have guiding significance for better understanding and application of CO2-ECBM technology.
Estimation of minimum miscibility pressure (MMP) in enhanced oil recovery (EOR) process by N2 flooding using different computational schemes Fuel (IF 4.908) Pub Date : 2018-09-20 Ali Barati-Harooni, Adel Najafi-Marghmaleki, Seyed-Ahmad Hoseinpour, Afshin Tatar, Abdorreza Karkevandi-Talkhooncheh, Abdolhossein Hemmati-Sarapardeh, Amir H. Mohammadi
Parameter estimation of a six-lump kinetic model of an industrial fluid catalytic cracking unit Fuel (IF 4.908) Pub Date : 2018-09-19 Yakubu M. John, Mustafa A. Mustafa, Raj Patel, Iqbal M. Mujtaba
Characteristics comparison of tar from lignite pyrolysis with inherent and simulated moisture for adopting a two-stage gasification process Fuel (IF 4.908) Pub Date : 2018-09-18 Lijuan Zhang, Xi Zeng, Jiale Wang, Fang Wang, Jianling Zhang, Minchen Guo, Cuina Peng, Rongcheng Wu, Guangwen Xu
To utilize low rank coal cleanly and high efficiently, a new fluidized bed two-stage gasification (FBTSG) process, mainly consisting of a FB pyrolyzer and a transport bed gasifier, has been proposed to treat pressurized coal (below 10 mm) with relatively high moisture for the production of clean fuel gas. In this study, a laboratory FB pyrolysis apparatus was adopted to examine the influence of moisture mode on pyrolysis behavior from 600 °C to 900 °C, especially in the yield and property of pyrolysis tar. Two common experimental methods in literatures, namely wet coal with inherent moisture and dried coal with the simulated moisture by introducing steam, were systematically analyzed. Compared to the simulated moisture, inherent moisture in coal can facilitate effectively the generation of tar at 700 °C and 800 °C, and had strong reforming effect on tar conversion to light fraction, leading to more production of light fractions and micro-molecule compounds. All of these differences were much related to the difference in interaction pathway between volatile matter and moisture.
Numerical study of steam methane reforming over a pre-heated Ni-based catalyst with detailed fluid dynamics Fuel (IF 4.908) Pub Date : 2018-09-18 Dmitry Pashchenko
Spray morphology transformation of propane, n-hexane and iso-octane under flash-boiling conditions Fuel (IF 4.908) Pub Date : 2018-09-18 Yanfei Li, Hengjie Guo, Zhifu Zhou, Zhou Zhang, Xiao Ma, Longfei Chen
Spray collapse has been widely observed under both flash-boiling and non-flash-boiling conditions when multi-hole gasoline direct injection (GDI) injectors with compact nozzle configurations were used. The main objective of this study is to further understand the collapse mechanisms by using liquids with appreciably different properties (propane, n-hexane and iso-octane). The tests were carried out in a constant volume vessel with ambient pressures ranging from 0.6 bar to 11.0 bar and fuel temperatures from 30 °C to 110 °C. Flashing propane sprays presented a non-collapse feature under elevated-ambient-pressures but flash-boiling conditions. By close-up examination of flashing propane sprays over a wide range of liquid temperatures and ambient pressures, it was found that there should be an ambient pressure threshold between 1.0 and 3.0 bar between the collapsed and the non-collapse sprays for propane. The spray collapse occurred as the ambient pressure is below the threshold. The non-collapse feature for flashing propane sprays under the ambient pressures beyond the threshold was attributed to the prohibition of nucleation and bubble growth under elevated ambient pressures.
A novel fuel containing glycerol triacetate additive, biodiesel and diesel blends to improve dual-fuelled diesel engines performance and exhaust emissions Fuel (IF 4.908) Pub Date : 2018-09-18 Eivaz Akbarian, Bahman Najafi
Declining petroleum sources and increasing demands for energy and emissions characteristics of fossil fuels combustion lead investigations to clean, available and low-cost energy resources. Dual-fuelled diesel engine by NG as main fuel and biodiesel blend as pilot fuel can be an appreciate idea to reduce engine emissions and using renewable source of fuel. The main aim of present study is to use the blend of glycerol triacetate (GT) additive and biodiesel to reduce emissions and to improve fuel cost of dual-fuelled diesel engine by natural gas as main fuel. Tests performed on dual fueled, constant speed (1500 rpm) diesel engine by two levels of biodiesels (B5, B20) with three levels of GT additives (3%, 5%, 7%) and neat diesel fuel as pilot fuel and four levels of pilot fuel to gaseous fuel (20%, 30%, 40%, 50%). Based on results, using B5A3 as pilot fuel decreased NOx emission by 24% in pilot-to-gaseous (P/G) fuel ratio of 50%. Using B20A3 as pilot fuel significantly reduced PM emission, such that in P/G ratio of 20% it was 85% lower than that of diesel as pilot fuel. CO emission was found to be 72% lower than that of diesel as pilot fuel in case of using B5A7 as pilot fuel in P/G ratio of 20%. Using B5 as pilot fuel in P/G ratio of 20% reduced CO2 emission by about 8% compared to that of diesel as pilot fuel. UHC emission had been increased slightly using biodiesel and GT additive rather than diesel pilot fuel. It was also observed that in the P/G ratio of 40% using B5 fuel, the GP cost was 0.22 $/kWh which is about 15% lower than that for diesel pilot fuel.
Computational modeling of pulverized coal fired boilers – A review on the current position Fuel (IF 4.908) Pub Date : 2018-09-18 G. Sankar, D. Santhosh Kumar, K.R. Balasubramanian
Computational modeling of pulverized coal fired boilers has made considerable advances in the past 5 decades. Modeling the furnace of a coal-fired boiler is a complex task. Even though bulk of the heat transfer to the furnace water walls is by radiation, it is complicated by the presence of ash and other tri-atomic gases that participate in radiation. It is also necessary to accurately capture the kinetics of the devolatilization, char combustion and volatile combustion processes. The phenomenon of fluid flow is equally important since considerable amount of turbulence is involved. Any model developed for the prediction of critical performance parameters like furnace outlet gas temperature and pollutant emission levels will need to capture this multifarious nature of combustion inside a boiler furnace. While computationally expensive CFD codes are available in plenty, researchers have also developed simpler but effective reactor network models. This review explains the current research position in the computational modeling of pulverized coal fired boilers from the following perspectives i) Coal combustion modeling ii) Radiation modeling iii) Overall furnace model development.
Comparison of air and oily bubbles flotation kinetics of long-flame coal Fuel (IF 4.908) Pub Date : 2018-09-18 Songjiang Chen, Xiuxiang Tao, Shiwei Wang, Longfei Tang, Quanzhou Liu, Lulu Li
This paper focuses on the difference in kinetics of air and oily bubbles flotation of long-flame coal. Six flotation kinetic models were taken to fit the air and oily bubbles flotation results by the software MATrix LABoratory. The findings indicated that the conventional flotation was greater than the oily-bubble flotation in flotation rate in the early stage, and these two flotation processes exhibited different variation laws in cumulative concentrate yield with flotation time. Additionally, it was found that the classical first-order model could provide an excellent fit to the experimental data for the conventional flotation, yet all the studied kinetic models showed a great deviation in fitting to oily-bubble flotation data. Consequently, an improvement for flotation kinetic models was conducted by subtracting the delay constant in the oily-bubble flotation to attain an excellent fitting. Finally, the delay constant for the oily-bubble flotation was determined to be about 0.7500 min, while the improved classical first-order model was found to give the best fit to the oily-bubble flotation data. This study may contribute to a better understanding of the oily-bubble flotation characteristics.
A novel approach for solving nonlinear flow equations: The next step towards an accurate assessment of shale gas resources Fuel (IF 4.908) Pub Date : 2018-09-17 Yashar Bezyan, Mohammad Ebadi, Shahab Gerami, Roozbeh Rafati, Mohammad Sharifi, Dmitry Koroteev
As ultra-tight porous media that include organic contents, shale gas resources are technically known as complex systems having various mechanisms that impact storage and flow. The slippage, Knudsen diffusion, the process of desorption, an adsorbed layer that affects apparent permeability, and solute gas in kerogen are recognized to be the most important ones. However, simultaneous effects of multi-mechanism flow and storage, and influences of scattered organic contents on shale gas flow behaviour are not well-understood yet.According to the mass conservation law, a basic mathematical model has been developed to investigate, step-by-step, the effects of different changes that are introduced, and examine whether patterns of how kerogen is distributed affect the production plateaus. The discretization of the second-order nonlinear Partial Differential Equation (PDE) that is evolved results in a certain number of nonlinear simultaneous algebraic equations, which are conventionally solved with the application of Newton’s method. To overcome the inherent difficulties of the initial guess, the derivations, and the inversion of the Jacobian matrix, a new application of Particle Swarm Optimization (PSO) as a nonlinear solver was applied to extract the anticipated pressure profile for each step in time outside the bounds of the reference equations.The results show that not only can the PSO effectively meet the required criteria, but also it performed faster than conventional techniques, especially in cases with a larger number of grids that encompass more phenomena. It was further revealed that the insertion of a multi-mechanism apparent permeability model in which the pore radius is also a pressure-dependent parameter causes the lower rate of production. A higher level of production has been recorded after including storage terms of adsorption and solute gas in kerogens. Although different patterns of kerogen distribution have finally overlapped, the different taken trend of each production profile underlines the impact of kerogen distribution as an important parameter within the procedure of history matching.
Effect of CO2 atmosphere and presence of NOx (NO and NO2) on the moist oxidation of CO Fuel (IF 4.908) Pub Date : 2018-09-17 María Abián, Ángela Millera, Rafael Bilbao, María U. Alzueta
The role of CO2 on the moist oxidation of CO in the CO-NO and CO-NO2 systems is analyzed from both experimental and modelling points of view, under flow reactor conditions, at atmospheric pressure, over the temperature range of 700–1400 K and at fuel-rich (λ = 0.5) and fuel-lean (λ = 2) environments. Sensitivity and reaction rate analyses were used to identify the role of CO2 in this process. Additionally, the effect of the presence of NO and NO2 on CO oxidation is considered. Results indicate significant differences in combustion characteristics between CO oxidation in a 0% or 25% CO2 atmosphere, in the presence of both NO or NO2. In particular, at high temperatures, either NO or NO2 promote the CO oxidation in CO2 atmosphere, through a specific NO-NO2 interconversion system, which is catalysed by the CO2 presence. However, in the 1075–1150 K range and independent of the CO2 atmosphere, the CO oxidation is strongly inhibited by NO2 presence. The effect of CO2 and NOx presence on CO conversion is quite similar for both O2 levels.
Impact of HVO blends on modern diesel passenger cars emissions during real world operation Fuel (IF 4.908) Pub Date : 2018-09-17 Ricardo Suarez-Bertoa, Marina Kousoulidou, Michael Clairotte, Barouch Giechaskiel, Jukka Nuottimäki, Teemu Sarjovaara, Laura Lonza
Experimental investigations of oxyfuel burner for cement production application Fuel (IF 4.908) Pub Date : 2018-09-15 Francisco Carrasco, Simon Grathwohl, Jörg Maier, Johannes Ruppert, Günter Scheffknecht
The production of cement is one of the CO2 intensive processes, due to the inherent formation of CO2 in the calcination process by decomposition of limestone which is additional to the CO2 generated from fuel combustion. Carbon capture and storage technologies have been seen as a promising way to comply with CO2 reduction targets. As part of the objectives of the Horizon 2020 project CEMCAP, the retrofitting of key parts of the equipment of a conventional cement plant to oxyfuel combustion are investigated. The present study reports the results of several combustion tests employing a downscaled commercial kiln burner to determine its adequacy for oxyfuel operation mode. The investigations were carried out in the 500 kWth top-fired combustion facility at University of Stuttgart, which was previously adapted for these tests, including the installation of an electric preheating system to rise secondary gas temperature up to 800 °C. Fuel used is a German pre-dried lignite previously milled to required fineness in a separate location. A variety of in-flame measurements are performed at a dozen of ports located at different distances from burner outlet in order to characterize combustion behavior in each firing mode. It was observed that under oxyfuel mode additional parameters in burner configuration like total oxygen concentration and oxygen distribution in primary and secondary gas are key variables to adjust flame formation and obtain similar results as in conventional air firing.
Prevention of lean flame blowout using a predictive chemical reactor network control Fuel (IF 4.908) Pub Date : 2018-09-15 Saurabh Gupta, Philip Malte, Steven L. Brunton, Igor Novosselov
Optimization of efficiency and pollution control for gaseous species and particulate matter are common to any combustion system. Combustor lean blowout (LBO) is a concern for aircraft safety and for land-based gas turbines designed to operate at lean equivalence ratios to achieve better fuel efficiency and to limit NOx emissions. This paper provides an experimental demonstration of model-based control applied to a laboratory jet-stirred reactor (JSR) approaching LBO. The approach uses (1) combustor temperature measurements, coupled with (2) the calculation of free radical concentrations in the reactor using a real-time chemical reactor network (RT-CRN) model as the reactor approaches LBO, which in turn (3) are used by a predictive control algorithm to achieve stable combustion. The RT-CRN represents the combustor as three perfectly stirred reactors (PSRs) in series with a recirculation pathway; the model inputs include real-time measurements of temperature and mass flow rates of fuel and air. In a series of experiments, the combustor is operated on a premixed methane-air mixture; after achieving stable combustion, the air flow rate is increased beyond the stable air-fuel ratio either as a step function or by ramping up linearly. The predictive RT-CRN control algorithm calculates the distribution of hydroxyl (OH) radicals in the free jet, impinging jet, and recirculation regions of the JSR in near real-time (∼1 s delay), and determines the leanest stable state based on the OH uniformity in the combustor. As the OH shifts towards the recirculation region, the reactor approaches LBO, if this condition is detected the control algorithm injects additional fuel; reactor stabilization is achieved within a 5–15 s time frame. Although this proof-of-concept demonstration is performed for LBO control in a JSR with ceramic walls, the control methodology is applicable to other types of high-intensity recirculation stabilized combustors.
Comparative study of fuel-N and tar evolution in chemical looping combustion of biomass under both iG-CLC and CLOU modes Fuel (IF 4.908) Pub Date : 2018-09-15 A. Pérez-Astray, I. Adánez-Rubio, T. Mendiara, M.T. Izquierdo, A. Abad, P. Gayán, L.F. de Diego, F. García-Labiano, J. Adánez
Chemical looping combustion (CLC) processes combined with CO2 sequestration and sustainable management of biomass represent a promising BioEnergy with Carbon Capture and Storage (BECCS) technology. One of the aspects to be considered in the combustion of biomass is the formation of NOx and the possible existence of tar in the gaseous product stream. The advantage of the CLC technology compared to other CO2 capture technologies is that only fuel-N contributes to nitrogen oxides formation. Moreover, scarce information is available about tar formation in CLC. Thus, this work focuses on these two aspects and compares the results obtained when two different chemical looping combustion modes are used, namely In Situ Gasification Chemical Looping Combustion (iG-CLC) and Chemical Looping with Oxygen Uncoupling (CLOU). Important differences were observed depending on the combustion mode. In both cases most of the fuel-N appeared as N2 in the fuel reactor. However, in iG-CLC more than 94% of the nitrogen measured in the fuel reactor was N2 independently of the biomass used. These percentages under the CLOU mode were lower. In this case, low amounts of N2O were also detected, although it decreased to almost zero at 850 °C. In the air reactor, NO was found and its concentration remained below the legal limit for NOx emissions in power installations with all the types of biomass tested and operating modes. Tar species and concentrations found at the fuel reactor outlet stream were different under the two combustion modes. About 2.5–3.7 g/Nm3 total tar could be found at 980 °C burning under iG-CLC mode, mostly naphthalene. On the contrary, insignificant tar amounts were found in CLOU.
Novel route of synthesis of ultra-small Au nanoparticles on SiO2 supports Fuel (IF 4.908) Pub Date : 2018-09-15 Y. Kotolevich, O. Martynyuk, S. Martínez-González, H. Tiznado, A. Pestryakov, M. Avalos Borja, V. Cortés Corberán, N. Bogdanchikova
A novel route to prepare monodispersed 1–2 nm gold nanoparticles (NPs), based on the use of extremely small SiO2 NPs (2–4 nm) as a support and increasing their metal-support interaction with surface modifier oxides is presented. The influence of modifier (La, Ce and Fe oxides) and modification method (impregnation (i) or direct synthesis (s)) on the formation of ultra-small Au NPs and their structural and electronic properties was studied. The samples were characterized by N2 adsorption (BET), FTIR of adsorbed CO, XRD and HR-TEM methods, and tested for the catalytic selective oxidation of 1-octanol. Preparation of monodispersed Au NPs with 1 nm diameter was successfully achieved for all the modified samples studied, with exception of Au/Ce/SiO2-i, where CeO2 was not homogeneously distributed. The Au NPs have high degree of monodispersity and are stable when treated in H2 up to 300 °C. Formation of these Au NPs depended on the strong interactions between the cationic gold complex precursor and the surface of modified SiO2 NPs. Modifiers changed electronic properties of supported gold; favoring the formation and stabilization of Auδ+ states, which are probable gold active sites of selective liquid-phase oxidation of alcohols in redox catalytic processes. 1-octanol oxidation was used as a model reaction for oxidation of fatty alcohols obtained during biomass transformation. The best performance for 1-octanol oxidation was found for gold nanoparticles supported on the ultra-small SiO2 modified cerium oxide by impregnation method. The relative order of activity was: AuCeSiO2-i > AuFeSiO2-i ≫ AuLaSiO2-i ≈ AuLaSiO2-s > AuSiO2 > AuFeSiO2-s≫ AuCeSiO2-s. The obtained results open the possibility of further development of high-performance catalysts for conversion of secondary products of biomass processing into valuable chemicals.
Evaluation of gaseous and solid products from the pyrolysis of waste biomass blends for energetic and environmental applications Fuel (IF 4.908) Pub Date : 2018-09-15 Despina Vamvuka, Stelios Sfakiotakis, Olga Pantelaki
An industrial swine sludge and its blends with agricultural wastes from the oil industry were pyrolyzed in fixed bed and TG-MS units. Gaseous species were quantitatively analysed and the energy potential was evaluated. The biochars produced at different temperatures were characterized by physical and chemical analyses. Leaching experiments of biochar mixtures through soil predicted their suitability for soil amendment, as well as their environmental impact. The Higher Heating Value of the gases was found to be satisfactory for the energy requirement of pyrolysis units. Alkali metals Na and K and alkaline earth metal Mg were leached in high amounts through the soil, increasing the pH of the extracts and decreasing the leachability of heavy metals, which were below legislation limits. Biochars examined could be used as liming agents or for soil amendment providing plant nutrients. The waste materials examined could be valorized for energy and agronomic processes.
Beech wood gasification in a dense and fast internally circulating fluidized bed Fuel (IF 4.908) Pub Date : 2018-09-15 Sebastien Pecate, Sid Ahmed Kessas, Mathieu Morin, Mehrdji Hemati
This study deals to improve the understanding of biomass thermo-chemical conversion in a dense and fast internally circulating fluidized bed. The experimental rig used in this study ran either as a dense fluidized bed or as a fast internally circulating fluidized bed. The effect of operating parameters, such as bed temperature (ranging from 750 to 850 °C), steam gas velocity (between 3 and 9.5 times the minimum fluidization velocity of bed material), steam to biomass mass ratio (ranging from 0.7 to 5.6 kg.kg−1) and biomass shape (sawdust and pellets) is investigated in both dense and fast internally circulating fluidized bed with olivine as bed material. In addition, the effect of bed material nature (olivine and sand) is also studied. Results indicated that syngas composition is strongly dependent on steam to biomass mass ratio. Moreover, it was found that syngas yield is favored by rising bed temperature and steam to biomass mass ratio while it is disadvantaged when fluidizing gas velocity increases. In addition, a greater syngas yield was obtained with olivine particles, compared to sand particles. The effect of bed material circulation flow rate was also investigated in fast internally circulating fluidized bed. Results showed that an increase in this parameter leads to a lower syngas yield. Finally, the experimental results presented in this paper were compared to ones reported in the literature and a good agreement was found.
Bioethanol production from various lignocellulosic feedstocks by a novel “fractional hydrolysis” technique with different inorganic acids and co-culture fermentation Fuel (IF 4.908) Pub Date : 2018-09-15 Archana Mishra, Sanjoy Ghosh
Methane number measurements of hydrogen/carbon monoxide mixtures diluted with carbon dioxide for syngas spark ignited internal combustion engine applications Fuel (IF 4.908) Pub Date : 2018-09-15 German J. Amador Diaz, Lesme M. Corredor Martinez, Juan P. Gomez Montoya, Daniel B. Olsen
A comprehensive analysis of the autoignition tendency of binary mixtures of hydrogen and carbon monoxide diluted with carbon dioxide is carried out in this paper. Methane Number (MN) measurements of these mixtures were performed by using a method analogous to the standard method for Octane Number (ON) measurement. The experimental MNs ranged from 46.0 to 139.1 according to experimental data. These results are compared with the MNs calculated by programs released for natural gas MN estimations. A comparative analysis concluded that these programs are not suitable to calculate MN of syngas. A method to isolate the effect of carbon dioxide on the autoignition tendency of binary mixtures of hydrogen and carbon monoxide is proposed. Results reveal that increments of carbon dioxide concentration in the mixtures, exponentially increase the MN of the mixtures. At low carbon dioxide concentration, the MN of the ternary mixtures can be approximated by the MN of their equivalent binary mixtures of hydrogen and carbon monoxide. Based on this observation, the MNs of coal gases reported in the literature are estimated.
Active phases and reaction performance of Mo improved Ni/Al2O3 catalysts for thioetherification Fuel (IF 4.908) Pub Date : 2018-09-15 Zhibing Shen, Ming Ke, Ling Lan, Peng He, Shengrong Liang, Juntao Zhang, Hua Song
Characteristics and stability of biofuels used as drop-in replacement for NATO marine diesel Fuel (IF 4.908) Pub Date : 2018-09-15 Jinxia Fu, Scott Q. Turn
Catalytic hydrothermal conversion diesel (CHCD-76), synthesized isoparaffin (SIP-76), and hydroprocessed renewable diesel (HRD-76) have been produced in sufficient quantity and supplied to the U.S. Navy for blending with traditional marine diesel NATO F-76. The present work investigates the storage and oxidation stabilities of DSH-76, CHCD-76, and their blends with F-76. Chemical composition and physicochemical properties of these two biofuels, including viscosity, density, peroxide value, heat of combustion, acid number, and phase behavior, were determined using required ASTM methods. ASTM D4625 and D5304 methods were employed to investigate the long-term storage stability of these two biofuels and theirs blends with F-76. ASTM D5304 method was also modified to investigate the oxidation process of these fuel samples. In addition, ASTM D2274 tests were conducted to investigate oxidation stability of the neat and blended fuel samples. The influence of long-term storage and oxidation on fuel physicochemical properties was investigated based on ASTM methods. SIP-76 and CHCD-76 were found have superior storage and oxidation stability in comparison with petroleum F-76. This is also the first report on storage and oxidation stability of SIP-76 and CHCD-76.
Detailed parametric investigation of dry gasification oxy-combustion power cycle using ASPEN Plus simulations Fuel (IF 4.908) Pub Date : 2018-09-15 Ashitosh Darekar Dattatray, Vidyasagar Shilapuram
Dry gasification oxy-combustion (DGOC) power cycle is a novel, zero-emission power production scheme. This work presents the detailed parametric study of various process performance variables namely gasifier temperature, gasifier pressure, fraction of recycle gas from combustor, molar gasification agents ratio, different type of sorbents on the process performance measured in term of product gas quality and quantity, total heat generated for power production and sulfur removal efficiency using the ASPEN Plus simulator. Various sorbents namely CaCO3, Fe2O3, MnO, CuO are considered for this study. Results shows that different sorbents posses different behavior. Temperature has significant affect on the DGOC performance. Fe2O3 is not a suggested sorbent in DGOC. CuO appears to be good sorbent in terms of temperature in the gasifier required or energy input required to the gasifier, and sulfur removal efficiency. MnO appears to be good sorbent in terms of syngas quality and total heat generated which was used to produce power by DGOC cycle.
CO2 injection in coal: Advantages and influences of temperature and pressure Fuel (IF 4.908) Pub Date : 2018-09-15 Yinbo Zhou, Zenghua Li, Ruilin Zhang, Gongzhong Wang, Hong Yu, Guangzhong Sun, Liang Chen
Coalbed methane (CBM) recovery and CO2 storage have always been important topics of study for clean energy utilization and environmental governance. To enhance CBM recovery, CO2/N2 injection is applied in coal mining, especially CO2 injection enhanced coalbed methane (CO2-ECBM). CO2 injection not only improves the production of CBM but also helps to reduce the greenhouse effect. As there are differences between CO2 injection and N2 injection, the advantages of CO2 should be studied in depth. The adsorbed methane accounts for more than 80% of total methane, and the amount of variation adsorbed methane is the key to CO2/N2 injection. In this paper, the desorption rate of adsorbed methane, the replacement ratio and the residual mixed gas content are discussed to evaluate the effect of CO2/N2 injection. After CO2/N2 injection, the desorption rate of adsorbed methane could be enhanced. The results also show that CO2 injection is better than N2 injection for enhanced coalbed methane (ECBM) recovery; however, the residual mixed gas content could be increased after CO2 injection. Moreover, anthracite (QC) could be more suitable for CO2 injection because of the value of replacement ratio. The influences of temperature and injection pressure are also empirically studied. Increasing both temperature and pressure could not significantly enhance the desorption rate of adsorbed methane significant. Increasing the temperature could reduce the residual mixed gas content; however, it is difficult to induce ECBM recovery with increasing temperatures. Increasing the injection pressure could cause a slight increase of the desorption rate of the adsorbed methane; however, higher injection pressure corresponds to greater economic cost. Thus, the most suitable injection pressure is twice as much as the initial pressure of methane.
Molecular dynamics simulations of natural gas-water interfacial tensions over wide range of pressures Fuel (IF 4.908) Pub Date : 2018-09-15 Wenhui Li, Zhehui Jin
Natural gas-water interfacial tension (IFT) plays an important role in gas production and transportation as well as hydrate formation. While experiments can measure IFT from macroscopic perspective, the interfacial phenomena remain less clear at molecular level. In this work, we use molecular dynamics (MD) simulations to study hydrocarbon-water IFT up to 5000 bar at various temperature conditions. At each temperature, we study the IFT of C1-H2O system, C1 + C2 mixture-H2O system, C1 + C3 mixture-H2O system, and C1 + C2 + C3 mixture-H2O system. We find that IFTs decrease with increasing temperature at low pressure conditions, while the differences become insignificant at high pressures. Addition of C2 and C3 can lower IFT in line with the previous experimental findings, while C3 has a more pronounced effect than C2. However, after a certain pressure, IFT becomes similar for various hydrocarbon mixture-H2O systems. As pressure further increases, IFT gradually increases. At low and intermediate pressures, hydrocarbons can form adsorption layers on gas-water interfaces but become less significant at high pressures. We find that IFT decreases when the relative adsorption obtained from density distributions is positive but increases for negative relative adsorption at high pressures. This finding agrees well with previous molecular simulation work on C1-water interfacial tension. At low and intermediate pressures, relative adsorption becomes more significant when the heavier components (C2/C3) are added, resulting in a more pronounced IFT reduction effect. Our study provides fundamental understandings about the interfacial phenomena between hydrocarbon and water, and important insights into the energy prospection and flow assurance problems.
Preferential adsorption of nickel porphyrin to resin to increase asphaltene precipitation Fuel (IF 4.908) Pub Date : 2018-09-15 Masoumeh Mousavi, Shahrzad Hosseinnezhad, Albert M. Hung, Ellie H. Fini
This paper incorporates a multi-scale approach to evaluate the contribution of nickel porphyrin to the aggregation and precipitation of asphaltenes in a medium of solvent/precipitator. This study provides an in-depth understanding of the role of metalloporphyrins in the complex matrix of petroleum/bitumen. Density functional theory (DFT) calculations and laboratory experiments were performed to examine the changes in physicochemical and rheological properties of a selected bituminous structure when doped with Ni octaethylporphyrin (NiOEP). Based on the DFT results, light and small assemblies of asphaltene-resin (in the limit of a single asphaltene molecule) are easily attracted to NiOEP. This in turn may help establish the role of a metal center as a nucleating agent promoting formation of small nanoaggregates in solution. Our experiment results using size-exclusion chromatography and rheological analysis of bitumen doped with NiOEP indicate an increased number of small-size nanoaggregates, as evidenced by a reduction in large molecular size (LMS) and a reduction in the polydispersity index. The latter is indicative of the formation of uniform particle size within the matrix after being doped with NiOEP. The modeling results further show that in larger nanoaggregates, asphaltene-asphaltene intermolecular interactions are too strong to allow an asphaltene core to be affected by NiOEP. In such cases, small resin molecules surrounding asphaltenes show preferential adsorption to NiOEP and take distance from the original nanoaggregates, reducing nanoaggregates’ overall size. This was in line with UV–Vis absorption spectroscopy of a NiOEP-doped solution of bitumen showing that at least 95% of the added NiOEP remained in the maltenes portion containing resin, while only a trace amount of NiOEP was found in the asphaltenes. Considering the role of resins in stabilizing asphaltene aggregates, their departure can promote precipitation of asphaltene nanoaggregates. The latter was also evidenced by TLC-FID chromatography measurement, showing a substantial increase in asphaltene extracts in NiOEP-doped specimens compared to a control sample.
Revision of country specific NCVs and CEFs for all coal categories in Indian context and its impact on estimation of CO2 emission from coal combustion activities Fuel (IF 4.908) Pub Date : 2018-09-15 P. Sarkar, S.G. Sahu, S. Bhattacharya, A. Mukherjee, M. Kumar, A.K. Adak
This paper highlighted the need for periodic change in country specific NCVs and CEFs of solid fuels. Accepted India specific NCV/CEF values of coking coal, non-coking coal and lignite were worked out during the India’s Initial National Communication’2004 taking 1994 as the base year. Those values continued to be in use in CO2 estimations done by sectoral/national/international agencies and also in estimations related to India’s Second National Communication’2012 to UNFCCC. In present investigation fresh estimations taking base year as 2007 were done considering large numbers of relevant post 2006 coal-quality data for each Indian coal category and as a result NCV of non-coking and coking coal diminished by 6.6% and 2.1% respectively. The changes happened due to cumulative effect of slow changing quality of coking, non-coking coals and their grade-wise production pattern over the years. Using new NCV-CEF values, reduction of CO2 emission by 53.4 Tg, solid fuel (coal and lignite) emission by 5.4%, total fossil fuel emission by 3.8%, sectoral emissions by 2.7%–5.9% were observed. The relevance of new NCV-CEF values were examined in present context and the new values should be used for accurate estimation of CO2, which indicates energy efficiency and clean use of coals.
Measurements and modeling of PAH soot precursors in coflow ethylene/air laminar diffusion flames Fuel (IF 4.908) Pub Date : 2018-09-14 A. Jerez, J.J. Cruz Villanueva, L.F. Figueira da Silva, R. Demarco, A. Fuentes
New experimental and numerical results of a laminar ethylene-air co-flow non-premixed flame are compared, in terms of soot volume fraction and temperature, and of polycyclic aromatic hydrocarbons (PAH) distributions. Measurements involved UV-excited laser induced incandescence (properly calibrated), planar laser induced fluorescence (PLIF), and deconvoluted two-color pyrometry. In order to evidence soot and PAH, the comparison of prompt and delayed detection is carried out at four spectral detection wavelengths (340, 400, 450 and 550 nm). Numerical results are obtained using a detailed gas-phase chemical kinetics mechanism considering 94 species and 719 reactions, and a sectional soot model, together with a statistical narrow band correlated K (SNBCK) wide band model to account for radiation. Computed PAH, grouped by their number of rings, is found to exhibit a good correlation with experimental PLIF results at different spectral detection wavelengths. In particular, it is shown that 340 and 400 nm fluorescence signals indicate the presence of one up to four-ringed computed PAH, whereas the interpretation of measurements at larger wavelengths is found to be elusive, due to soot signal overlap. Furthermore, an interplay between temperature decrease, soot volume fraction increase and radiative heat transfer distribution with increasing fuel flow rate is also demonstrated.
Experimental study on the load response rate under the dynamic combined combustion of PC coal and CFB coal in a CFB boiler Fuel (IF 4.908) Pub Date : 2018-09-14 Zhongyuan Liu, Suxia Ma, Xiongfeng Pan, Jun Chen
Exploration of the pyrolysis chemistry of 1,1-diethoxybutane: A flow reactor and kinetic modeling study Fuel (IF 4.908) Pub Date : 2018-09-14 Meirong Zeng, Yuyang Li, Wenhao Yuan, Yan Zhang, Jiuzhong Yang, Fei Qi
1,1-Diethoxybutane is a promising next-generation biofuel and this work reports the first study for its pyrolysis chemistry. Pyrolysis of 1,1-diethoxybutane was investigated in a flow reactor at 0.04 and 1 atm using synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). A series of oxygenated and hydrocarbon products, including several radicals, were detected and their mole fractions were evaluated. A detailed kinetic model of 1,1-diethoxybutane, including 253 species and 1577 reactions, was developed and validated against the present experimental data. Modeling analyses including the rate of production analysis and sensitivity analysis were performed to reveal the crucial consumption pathways of 1,1-diethoxybutane, as well as the formation and consumption pathways of intermediates and products. The H-abstraction reactions of 1,1-diethoxybutane play a key role in fuel consumption. The intra-molecular elimination reactions and unimolecular CC or CO dissociation reactions of 1,1-diethoxybutane make minor contributions to fuel consumption. The sensitivity analysis also shows that the fuel consumption reactions have large sensitivities to 1,1-diethoxybutane. Further β-CC and β-CO scission reactions closely connect the consumption of six fuel radicals and the formation of most oxygenated products. The observation of high mole fractions of C1–C4 acids and aldehydes demonstrates the structural features of 1,1-diethoxybutane. Besides, several hydrocarbon products, such as C2–C4 alkenes, benzene and its precursors, were detected, some of which, such as propene, are also produced from the consumption reactions of fuel radicals. Besides, hydrocarbon products can also be produced from the combination reactions of small species, such as the combination reactions of C3 species to produce benzene and the combination reaction of allyl and methyl to produce 1-butene. The low benzene production ability of 1,1-diethoxybutane implies its low sooting tendency compared with fossil-derived transportation fuels.
Hydroisomerization of n-dodecane over bi-porous Pt-containing bifunctional catalysts: Effects of alkene intermediates’ journey distances within the zeolite micropores Fuel (IF 4.908) Pub Date : 2018-09-14 Yadong Zhang, Dong Liu, Zhuowu Men, Ke Huang, Yijun Lv, Ming Li, Bin Lou
Quantitative evaluation of the impacts of drilling mud on the damage degree to the permeability of fractures at different scales in coal reservoirs Fuel (IF 4.908) Pub Date : 2018-09-13 Xiaoming Ni, Zedong Liu, Jianping Wei
The current study aimed to investigate the degree of pollution from drilling mud on different scales of fractures in coal reservoirs. Drilling mud for field utilization was prepared in the laboratory and different scales of fractures were generated in coal and rock samples before and after being polluted by the drilling fluid and observed using scanning electron (SEM) and an optical microscope. Using Monte Carlo modelling, the networks of the millimeter (mm), micron- and nano-meter sized fractures, before and after pollution were separately determined. After programming, seepage models of mm, micron- and nano-meter sized fractures were separately constructed using Matlab software. The degrees of pollution of the drilling fluid on the different scales of fractures were calculated according to the seepage principle and compared with the measured permeability of the polluted boreholes. The micron- and nano-sized fractures were more sensitive to drilling fluids compared to the mm-sized and larger fractures. When the original permeability of the coal reservoir was low, different scales of fractures were all greatly polluted by drilling fluids, macroscopically showing high damage to permeability of the coal reservoir. However, when the original permeability of coal reservoir was large, the pollution degrees of micron, and nano-sized fractures failed to be macroscopically observed, having insignificant influences on the permeability of the coal reservoir. The results showed that the combination of the Monte Carlo method and the Matlab numerical simulations can more distinctly reflect the pollution degrees of the drilling fluids on different scales of fracture compared to traditional methods that have been used to test the permeability of coal reservoirs before and after pollution.
Oxidation of n-hexane in the vicinity of the auto-ignition temperature Fuel (IF 4.908) Pub Date : 2018-09-13 R. Mével, F. Rostand, D. Lemarié, L. Breyton, J.E. Shepherd
The present study examines the possibility of inerting flammable mixtures (making the mixtures non-explosive/non-flammable) using a long duration thermal process close to but below the auto-ignition temperature. Experiments were performed in a stainless steel cell and a Pyrex cell. A Mid-IR FTIR spectrometer, a UV–vis spectrometer and several IR laser diodes were employed to monitor the gas-phase composition. Experiments were performed for n-hexane-air mixtures with Φ = 0.67–1.35. The temperature and pressure were T = 420–500 K and P = 37–147 kPa. Experiments were performed over period of up to 7200 s. At temperatures close to 420 K, the chemical activity is characterized by a slow and constant reaction rate. At temperatures close to 500 K, the reaction proceeds in two-phases: 1) rapid production of CO2, CO and carbonyls, identified as hydroperoxy-ketones, followed by 2) a period of slower production of CO2 and H2O and consumption of hydroperoxy-ketones. At the end of the thermal treatment, the possibility of igniting the mixtures using a large hot surface (representative of low-temperature ignition source) and a stationary concentrated hot surface (representative of high-temperature ignition source) was tested. The low-temperature flammability was verified by rapidly increasing the temperature of the test cell wall whereas the high-temperature flammability was verified by turning on a glow plug. The inerting strategy seems effective in preventing the low-temperature ignition but high-temperature ignition was always observed. .
Experimental analysis of nanofuel additives with magnetic fuel conditioning for diesel engine performance and emissions Fuel (IF 4.908) Pub Date : 2018-09-13 Rashmi Rekha Sahoo, Animesh Jain
This paper presents an experimental work for the realization of the concept including nanofuel application to a single cylinder diesel engine, with and without magnetic fuel conditioning at various locations on fuel line. With the effect of magnetic field, ionization takes place and declustering the hydrocarbon fuel molecules for better atomization of the fuel and mixing the fuel-air mixture to enhance the combustion, which improves the fuel economy. CuO nanofuel was prepared by 0.5% CuO (wt./wt.) mass fraction nanoparticles blended with diesel fuel by means of a mechanical homogenizer and an ultrasonicator. Physicochemical properties of CuO nanofuel were measured and compared with neat diesel fuel. Their stability characteristics were analyzed under static conditions. The effects of the CuO nanoparticles on the engine performance and emissions were also investigated with permanent magnet of field strength 3000 Gauss. Mounting permanent magnets in fuel line enhanced fuel properties such as it aligned and oriented hydrocarbon moleculesfor better atomization of fuel, which results better emission of engine.The experimental analysis revealed that CuO nanofuel has improved performance and emission characteristics. The engine test results with magnetic fuel conditioning showed that, the CuO nanofuel has better mechanical efficiency of 7%, reduction in BSFC by 6% and reduction in 13% and 19% for CO2 and NOx emissions respectively, compared to diesel fuel. As a whole, CuO nanofuel with magnetic fuel conditioning have pronounced effect on enhancing the brake thermal efficiency and reducing the harmful pollutants of the compression ignition engine.
Study on the combustion characteristics and ignition limits of the methane homogeneous charge compression ignition with hydrogen addition in micro-power devices Fuel (IF 4.908) Pub Date : 2018-09-13 Qian Wang, Yan Zhao, Fan Wu, Jin Bai
Based on the single process of free piston in micro HCCI free piston power device, the parameters such as the combustion characteristics of methane hydrogenation homogeneous charge compression ignition, the free piston movement process, the ignition time of the mixture gas, the changes of temperature and pressure in micro-combustion chamber, and the power capability of the device are compared and analyzed by combining the experiment method with the numerical simulation method. The experimental results are basically consistent with the numerical results. The research shows: when the initial equivalence ratio is 0.5, the blending of hydrogen can widen the ignition limit of mixed fuel, advance the ignition time of the mixture gas and reduce the starting energy needed for the device. At the same time, adding hydrogen to methane will reduce the maximum temperature and the maximum pressure of the micro-combustion chamber, make the burning flame more stable and alleviate the detonation phenomenon of the combustion of mixture gas. However, the addition of hydrogen to methane will result in the decrease of the final speed of the free piston, the increase of the time required for a single stroke, the decrease of the power capacity of the device, and the indicator thermal efficiency is also reduced. Only the proper hydrogen blending ratio can be used to expand the combustion boundary and improve the reliability of the combustion process while ensuring the capability of the micro power device.
Numerical analysis of knock combustion with methanol-isooctane blends in downsized SI engine Fuel (IF 4.908) Pub Date : 2018-09-13 Hongqing Feng, Jianan Wei, Jing Zhang
Methanol is a promising fuel to suppress knock for improving engine compression ratio. In this study, knock combustion was simulated in a downsized spark engine with different methanol-isooctane blends. The pressure and temperature evolution profiles of these mixtures during knocking were obtained and showed that knock here originated from the intensive interaction between pressure wave and the heat released from auto ignition, which leaded to some other hot-spots. While using 5% methanol, the intensity of chemical reactions was reduced sharply comparing with that of pure isooctane, which lowered the heat release rate and successfully reduced the intensity of knock. The reactions below temperature of 950 K gradually become slower with methanol content increasing to 10% and 15%. However, the accelerated reactions made fuel consumed faster once it exceeded this certain temperature limit, which leaded a slight increase in knock intensity. The outcome of this work is potentially useful for comprehending the knock process of methanol.
A review of the current progress of CO2 injection EOR and carbon storage in shale oil reservoirs Fuel (IF 4.908) Pub Date : 2018-09-13 Bao Jia, Jyun-Syung Tsau, Reza Barati
CO2 injection is a promising method to rejuvenate the shale oil reservoirs after the primary production. In this work, we comprehensively reviewed the CO2 injection enhanced oil recovery (EOR) and carbon storage related literature in shales over the past decade. The aspects reviewed include description of major shale reservoirs producing oil and the necessity to perform EOR, selection of injection scheme, models applied to simulate gas injection, oil recovery mechanisms for different types of gas, molecular diffusion and its laboratory measurement, nanopore effect, adsorption effect on carbon storage and transport, laboratory work of gas injection in shale cores, pilot tests, and economic evaluation. Advanced models in recent years applied to simulate these processes were introduced in details, such as the traditional dual continuum model, the embedded discrete fracture model (EDFM). Heterogeneity effect and upscaling algorithm on the shale oil recovery performance were discussed. Molecular diffusion, as an important flow and oil recovery mechanism, was described regarding its definition, empirical correlation and laboratory measurement with consideration of the porous media effect which is crucial for accurate modeling result. Recovery mechanisms by carbon dioxide, methane and nitrogen were compared at the molecule and pore levels. Pros and cons of different types of gas were evaluated as well. Pore confinement caused by the extremely tiny pores in the organic matter, along with the capillary and adsorption effects were discussed, and approaches to take them into account of the model were addressed. Core-scale gas injection experiments on shales from various institutions were described, and the results were compared. Outcomes of recent pilot tests in the Eagle Ford, and the Bakken formations were summarized, and finally, economic considerations were provided for the feasibility of gas injection in shale oil reservoirs.
Pinewood pyrolysis occurs at lower temperatures following treatment with choline-amino acid ionic liquids Fuel (IF 4.908) Pub Date : 2018-09-12 Manuel Brunner, Hua Li, Zhezi Zhang, Dongke Zhang, Rob Atkin
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