Formulating and optimizing a combustion pathways for oil shale and its semi-coke

Enhanced technologies from oil recovery to unconventional fuels - oil shale, oil sands and extra-heavy oil – have in common complex chemical reactions processes. This paper is about the formulation and optimization of the chemical mechanism especially in oil shale and semi-coke combustion. The Levenberg–Marquardt algorithm was used to minimize the error between estimated values and the thermogravimetric data for combustion mechanisms of 4-steps and 3-steps proposed for the oil shale and its semi-coke respectively. The kinetic parameters such as reaction order, pre-exponential factor, activation energy and stoichiometric coefficients that affect drying, pyrolysis, oxidation and decarbonation reactions were estimated with success. The values of activation energies were 54–67 kJ mol^?1 for oil shale drying, 62–65 kJ mol^?1 for pyrolysis reaction, up to 100 kJ mol^?1 for Fixed Carbon (FC) oxidation reaction, and 162–418 kJ mol^?1 for decarbonation reaction. Regarding to the semi-coke combustion, the activation energies were 33 kJ mol^?1 for drying reaction, 211 kJ mol^?1 for oxidation reaction and 291 kJ mol^?1 for decarbonation reaction. The chemical reactions suggest reaction order superior to one, except to the decarbonation reaction at 3 K min^?1. Considering the estimated parameters, as well as a heating rate at 3 K min^?1, an oil shale containing about 20 wt.% of organic matter and 34.6 wt.% of CaCO₃, the species mass fractions formed during combustion process were 3.4 wt.% of FC, 10.6 wt.% of Oil, 3.3 wt.% of HC and 1.8 wt.% of CO. The fraction of CO₂ formed accounts a total of 21.6 wt.%. For a semi-coke containing 3.4 wt.% of FC and 40.6 wt.% of CaCO₃, its combustion formed 2.1 wt.% of CO. The CO₂ fraction from oxidation and decarbonation reactions accounts 10.2 wt.%, considering that the stoichiometric mass coefficient γ = 0.75 in decarbonation reaction.     

Effect of pyrolysis temperature on the composition of the oils obtained from sewage sludge

Sewage sludge was pyrolysed in a quartz reactor at 350, 450, 550 and 950 °C. The pyrolysis oils from the sewage sludge were characterized in detail by means of gas chromatography–mass spectrometry (GC–MS). Changes in the composition of the oils related to the process conditions were assessed by normalizing the areas of the peaks. It was demonstrated that, as the temperature of pyrolysis increased from 350 to 950 °C, the concentration of mono-aromatic hydrocarbons in the oils also increased. Conversely, phenol and its alkyl derivatives showed a strong decrease in their concentration as temperature rose. Polycyclic aromatic hydrocarbons (PAHs) with two to three rings passed through a maximum at a pyrolysis temperature of 450 °C. PAHs with 4–5 rings also presented a major increase as temperature increased up to 450 °C, the concentration at 950 °C being slightly higher than that at 450 °C. Quantification of the main compounds showed that sewage sludge pyrolysis oils contain significant quantities of potentially high-value hydrocarbons such as mono-aromatic hydrocarbons and phenolic compounds. The oils also contain substantial concentrations of PAHs, even at the lowest temperature of 350 °C. The pathway to PAH formation is believed to be via the Diels–Alder reaction and also via secondary reactions of oxygenated compounds such as phenols.     

Experimental and theoretical investigation of heat and mass transfer processes during wood pyrolysis

Thermal decomposition of 25.4 mm diameter dry wood spheres is studied both experimentally and theoretically. Wood spheres were pyrolyzed in a vertical tube furnace at temperatures ranging from 638 K to 879 K. Mass loss and temperatures of the sample were measured during pyrolysis. Center temperature measurements showed two distinct thermal events consisting of sequential endothermic and exothermic reactions. A numerical investigation of these endo/exothermic reactions using various pyrolysis kinetics models was conducted to determine the pyrolysis mechanism and the heats of the pyrolysis reactions. A comparison of the experimental and numerical results showed that (i) Contrary to the suggestions in the literature, the contributions of the secondary tar decomposition and lignin decomposition to the center temperature exothermic peak are small. (ii) Exothermic decomposition of the intermediate solid is responsible for the center temperature peak. (iii) The center temperature plateau is caused by the endothermic decomposition of cellulose. (iv) Internal pressure generation was found to be quite important because it controls the pyrolyzate mass transfer and thus affects both the heat transfer and the residence time of the pyrolysis gases for secondary decomposition.Based on the experimental and numerical results, a new wood pyrolysis model is proposed. The model consists of three endothermic parallel reactions producing tar, gas and intermediate solid and subsequent exothermic decomposition of the intermediate solid to char and exothermic decomposition of tar to char and gas. The proposed pyrolysis model shows good agreement with the experiments.Pressure calculations based on the new pyrolysis model revealed that high pressure is generated inside the biomass particle during pyrolysis and sample splitting was observed during the experiments. The splitting is due to both weakening of the structure and internal pressure generation during pyrolysis. At low heating rates, structural weakness is the primary factor, whereas at high heating rates, internal pressure is the determining factor. It is expected that moisture, while not considered in this work will have a similar effect, but at lower temperatures.     

Kinetic model of homogeneous thermal decomposition of methane and ethane

In this paper, the homogeneous decomposition of methane and ethane is modeled in a well stirred flow reactor. The kinetics of this process is represented by a reaction mechanism of 242 reactions and 75 species, based on a mechanism developed for hydrocarbon combustion and soot formation. It is shown that this model correctly predicts the hydrogen yield from pyrolysis in a temperature range of 600–1600 °C, and pressure range of 0.1–10 atm. Furthermore, the effect of temperature, pressure and residence time on the amount of hydrogen produced from the decomposition of methane, ethane, natural gas, and a mixture of methane and argon is studied. The model predicts that the use of ethane or its addition to methane increases the speed of hydrogen production at low temperatures and pressures. The addition of a noble gas like argon also increases the yield of hydrogen at high pressures.     

Investigating the potential for energy,fuel, materials and chemicals production from corn residues (cobs and stalks) by non-catalytic and catalytic pyrolysis in two reactor configurations

The results of thermogravimetric analysis (TGA), non-catalytic and catalytic pyrolysis of corn cobs and corn stalks are reported in this paper. Pyrolysis took place in two different reactor configurations for both feedstocks: (1) fast pyrolysis in a captive sample reactor; and (2) non-catalytic slow pyrolysis and catalytic pyrolysis in a fixed-bed reactor. Experiments were carried out in atmospheric pressure at three temperatures: low temperature (360–380 °C), medium temperature (500–600 °C) and at high temperature (600–700 °C). The results of the experimental study were compared with data reported in the literature. Investigating the potential of corn residues for energy, fuel, materials and chemicals production according to their thermochemical treatment products yields and quality, it can be stated that: (a) corn stalks could be suitable raw material for energy production via gasification at high temperature, due to their medium low heating value (LHV) of pyrolysis gas (13–15 MJ/m³); (b) corn cob could be a good solid biofuel, due to the high LHV (24–26 MJ/kg) of the produced char; (c) additionally, corn cobs could be a good material for activated carbon production after being activated or gasified with steam, due to its high fixed carbon content(～74 wt%); (d) liquid was the major pyrolysis product from catalytic pyrolysis (about 40–44 wt% on biomass) for both feedstocks; further analysis of the organic phase of the liquid products were hydrocarbons and phenols, which make them interesting for chemicals production.     

Thermalgravimetry–mass spectrometry studies on the thermal stability of graphite anodes with electrolyte in lithium-ion battery

Thermal reactions of a lithiated graphite anode in 1 M LiPF₆-ethylene carbonate (EC)/dimethyl carbonate (DMC) (50:50 vol.%) in the temperature range 40–320 °C were investigated by TG–MS analysis. Studies by TG–MS during thermal reactions detected a small exothermic peak around 140 °C due to CO₂ (m/z = 44) evolution, which suggests partial destruction of the SEI formed on the graphite and/or decomposition of the electrolyte through the SEI. In addition, the main exothermic reaction above 280 °C, which is associated with simultaneous evolution of C₂H₄O (m/z = 44), is caused by direct reaction of the lithiated graphite with solvent.     

Conversion of oil shale to liquid hydrocarbons

Oil shale is a complex fossil material that is composed of organic matter and mineral matrix. The thermal decomposition of the organic matter generates liquid and gaseous products. Oil shale is a porous rock containing kerogen, an organic bituminous material. Kerogen is a solid mixture of organic compounds that is found in certain sedimentary rocks. The kerogen can be pyrolyzed and distilled into petroleum-like oil. Oil shale and bituminous materials are suitable for obtaining petroleum-like products. The process designed in this study has the ability to control unwanted volatile materials. The mineral matter is removed from oil shale before pyrolysis. The pyrolysis of the oil shale is performed in a retort. The temperature at which the kerogen decomposes into usable hydrocarbons begins at 300°C, but the decomposition proceeds more rapidly and completely at higher temperatures. Decomposition takes place most quickly at a temperature between 475 and 525°C. Shale oil from oil shale consists of the hydrocarbons: paraffins, olefins, isoparaffins and naphthenes, isoolefins and cycloolefins, monocyclic aromatics, and poly-cyclic aromatics. The nonhydrocarbons are nitrogen, sulfur, and oxygen (NSO) compounds.     

Application of response surface methodology for optimizing transesterification of Moringa oleifera oil: Biodiesel production

Response surface methodology (RSM), with central composite rotatable design (CCRD), was used to explore optimum conditions for the transesterification of Moringa oleifera oil. Effects of four variables, reaction temperature (25–65 °C), reaction time (20–90 min), methanol/oil molar ratio (3:1–12:1) and catalyst concentration (0.25–1.25 wt.% KOH) were appraised. The quadratic term of methanol/oil molar ratio, catalyst concentration and reaction time while the interaction terms of methanol/oil molar ratio with reaction temperature and catalyst concentration, reaction time with catalyst concentration exhibited significant effects on the yield of Moringa oil methyl esters (MOMEs)/biodiesel, p < 0.0001 and p < 0.05, respectively. Transesterification under the optimum conditions ascertained presently by RSM: 6.4:1 methanol/oil molar ratio, 0.80% catalyst concentration, 55 °C reaction temperature and 71.08 min reaction time offered 94.30% MOMEs yield. The observed and predicted values of MOMEs yield showed a linear relationship. GLC analysis of MOMEs revealed oleic acid methyl ester, with contribution of 73.22%, as the principal component. Other methyl esters detected were of palmitic, stearic, behenic and arachidic acids. Thermal stability of MOMEs produced was evaluated by thermogravimetric curve. The fuel properties such as density, kinematic viscosity, lubricity, oxidative stability, higher heating value, cetane number and cloud point etc., of MOMEs were found to be within the ASTM D6751 and EN 14214 biodiesel standards.     

LiFePO4/carbon cathode materials prepared by ultrasonic spray pyrolysis

Small crystallites LiFePO₄ powder with conducting carbon coating can be synthesized by ultrasonic spray pyrolysis. Cheaper trivalent iron ion is used as the precursor. The pure olivine phase can be prepared with the duplex process of spray pyrolysis (synthesized at 450, 550 or 650 °C) and subsequent heat-treatment (at 650 °C for 4 h). The results indicate that the pyrolysis temperature of 450 °C is appropriate for best results. The carbon coating on the LiFePO₄ surface is critical to the electrochemical performance of LiFePO₄ cathode materials of the lithium secondary battery, since the carbon coating does not only increase the electronic conductivity via carbon on the surface of particles, but also enhance the ion mobility of lithium ion due to prohibiting the grain growth during post-heat-treatment. The carbon of 15 wt.% evenly distributed on the final LiFePO₄ powders can get the highest initial discharge capacity of 150 mA h g⁻¹ at C/10 and 50 °C.     

Comparison of biodiesel production from crude Jatropha oil and Krating oil by supercritical methanol transesterification

This work compared the production of biodiesel from two different non-edible oils with relatively high acid values (Jatropha oil and Krating oil). Using non-catalytic supercritical methanol transesterification, high methyl ester yield (85–90%) can be obtained in a very short time (5–10 min). However, the dependence of fatty acid methyl ester yield on reaction conditions (i.e., temperature and pressure) and the optimum conditions were different by the source of oils and were correlated to the amount of free fatty acids (FFAs) and unsaturated fatty acid content in oils. Krating oil, which has higher FFAs and unsaturated fatty acid content, gave higher fatty acid methyl ester yield of 90.4% at 260 °C, 16 MPa, and 10 min whereas biodiesel from Jatropha oil gave fatty acid methyl ester yield of 84.6% at 320 °C, 15 MPa and 5 min using the same molar ratio of methanol to oil 40:1. The product quality from crude Krating oil met the biodiesel standard. Pre-processing steps such as degumming or oil purification are not necessary.     

Performance evaluation of mixed convection in an inclined square channel with uniform temperature walls

Numerical analyses were performed for the effect of inclined angle on the mixing flow in a square channel with uniform temperature walls (T_w = 30 °C) and inlet temperature (T₀ = 10 °C). Three-dimensional governing equations were solved numerically for Re = 100, Pr = 0.72 and various inclined angles (from ?90° to 90°). Three-dimensional behavior of fluid in a channel was examined for each angle. Thermal performance was evaluated using the relationship between Nusselt number ratio and pressure loss ratio with and without buoyancy induced flow as a parameter of inclined angles. High heat transfer and low pressure loss region was from ?15° to ?60° in thermal performance using mean Nusselt number ratio.     

Preparation,characterization and electrolytic behavior of β-nickel hydroxide

Nickel hydroxide is prepared by neutralizing NiSO₄ solution with 4.8 M NaOH, followed by washing the precipitate and treating the slurry hydrothermally at different temperatures. The parameters varied are: initial nickel concentration; effect of presence of sodium ions during hydrothermal treatment; aging time after hydrothermal treatment. The samples so prepared are chemically analyzed and the physical and electrolytic properties such as tap density, percentage weight loss and discharge capacity are determined. On increasing the temperature from 60 to 160 °C, the discharge capacity increases from 52 to 112 mAh g⁻¹. At 200 °C, the discharge capacity decreases to 94 mAh g⁻¹. Allowing the hydroxide precipitate to age after hydrothermal treatment also causes a decrease in discharge capacity. The presence of excess sodium ions during hydrothermal treatment yields nickel hydroxide with a very low discharge capacity. The maximum discharge capacity of 160 mAh g⁻¹ is obtained for nickel hydroxide prepared under the following conditions: nickel concentration 43 g l⁻¹, neutralizing agent sodium hydroxide, time of hydrothermal treatment 2 h, temperature during hydrothermal treatment 160 °C. XRD patterns and FTIR spectra confirm the precipitate to be β-nickel hydroxide. The sample contains 62.89 wt.% Ni with a tap density of 0.96 g cm⁻³. TG–DTA measurements show a weight loss of 19% with an endothermic peak at 325 °C which corresponds to the decomposition of nickel hydroxide to nickel oxide. The present method of preparing nickel hydroxide through hydrothermal treatment reduces the aging time to 2 h and gives a product with good filtration characteristics.     

Sulfonic-functionalized heteropolyacid–silica nanoparticles for high temperature operation of a direct methanol fuel cell

Sulfonic-functionalized heteropolyacid–SiO₂ nanoparticles were synthesized by grafting and oxidizing of a thiol-silane compound onto the heteropolyacid–SiO₂ nanoparticle surface. The surface functionalization was confirmed by solid-state NMR spectroscopy. The composite membrane containing the sulfonic-functionalized heteropolyacid–SiO₂ nanoparticles was prepared by blending with Nafion^® ionomer. TG–DTA analysis showed that the composite membrane was thermally stable up to 290 °C. The DMFC performance of the composite membrane increased the operating temperature from 80 to 200 °C. The function of the sulfonic-functionalized heteropolyacid–SiO₂ nanoparticles was to provide a proton carrier and act as a water reservoir in the composite membrane at elevated temperature. The power density was 33 mW cm⁻² at 80 °C, 39 mW cm⁻² at 160 °C and 44 mW cm⁻² at 200 °C, respectively.     

Effect of orange peel oil on ethanol production by Zymomonas mobilis

The effect of orange peel oil on ethanol production by the ethanologenic bacterium Zymomonas mobilis was investigated. Orange peel oil was added in various amounts to determine its effects on ethanol production. Fermentation of model sugar solutions was conducted at 30 and 37 °C. The minimum orange peel oil concentration that inhibited ethanol production by Z. mobilis was determined after 24, 48, 72 and 96 h for both temperatures. Minimum inhibitory orange peel oil concentrations for ethanol production at 30 °C were 0.05% after 24 h, 0.10% after 48 h, 0.15% after 72 h, and 0.20% after 96 h. Minimum inhibitory orange peel oil concentrations for ethanol production at 37 °C were 0.05% after 24 h, 0.10% after 48 h, and 0.20% after 72 h. Orange peel oil did not inhibit ethanol production after 96 h at a temperature of 37 °C.     

Transport properties of ultra-low concentration CuO–water nanofluids containing non-spherical nanoparticles

CuO–water nanofluids were prepared from non-spherical CuO nanoparticles by dispersing them in water through the aid of ultrasonication along with the use of Tiron as dispersant. Thermal conductivity enhancements of 13% and 44% have been obtained with 0.016 vol% CuO–water nanofluids at 28 °C and 55 °C respectively, which could be attributed to the high aspect ratio and Brownian motion of nanoparticles. Correlations have been developed to predict the influence of temperature (28–55 °C) and nanoparticles volume concentration (<0.016 vol%) on relative viscosity and thermal conductivity ratio. The results indicate the potential of this nanofluid for thermal management applications.     

Proton conduction in ceria-doped Ba2In2O5 nanocrystalline ceramic at low temperature

Sintered pellets of Ce-doped Ba₂In₂O₅ (BIC) were prepared from nanopowders. The electrical conductivities were measured using ac impedance spectroscopy under different atmospheres and temperatures. The electrical conductivity of sintered BIC was found sensitive to environmental humidity when the temperature was below 300 °C. However, in the presence of hydrogen, the electrical conductivities were independent of water content in the range of 0–30 vol%. The electrical conductivities of BIC were significantly affected by the presence of hydrogen in a temperature range of 100–300 °C. The estimated protonic transference number and the measured open circuit voltage suggested the existence of electronic conduction. The coefficient of thermal expansion of BIC is 11.2 × 10⁻⁶ K⁻¹ from 25 to 1250 °C.     

Development of PVA based micro-porous polymer electrolyte by a novel preferential polymer dissolution process

A micro-porous polymer electrolyte based on PVA was obtained from PVA–PVC based polymer blend film by a novel preferential polymer dissolution technique. The ionic conductivity of micro-porous polymer electrolyte increases with increase in the removal of PVC content. Finally, the effect of variation of lithium salt concentration is studied for micro-porous polymer electrolyte of high ionic conductivity composition. The ionic conductivity of the micro-porous polymer electrolyte is measured in the temperature range of 301–351 K. It is observed that a 2 M LiClO₄ solution of micro-porous polymer electrolyte has high ionic conductivity of 1.5055 × 10⁻³ S cm⁻¹ at ambient temperature. Complexation and surface morphology of the micro-porous polymer electrolytes are studied by X-ray diffraction and SEM analysis. TG/DTA analysis informs that the micro-porous polymer electrolyte is thermally stable upto 277.9 °C. Chronoamperommetry and linear sweep voltammetry studies were made to find out lithium transference number and stability of micro-porous polymer electrolyte membrane, respectively. Cyclic voltammetry study was performed for carbon/micro-porous polymer electrolyte/LiMn₂O₄ cell to reveal the compatibility and electrochemical stability between electrode materials.     

Coconut oil extraction by the traditional Java method: An investigation of its potential application in aqueous Jatropha oil extraction

A traditional Java method of coconut oil extraction assisted by paddy crabs was investigated to find out if crabs or crab-derived components can be used to extract oil from Jatropha curcas seed kernels. Using the traditional Java method the addition of crab paste liberated 54% w w^?1 oil from grated coconut meat. Oil extraction using crab paste carried out under controlled temperatures and in the presence of antibiotics showed that enzymes from crab played a dominant role in liberating oil from grated coconut meat and aqueous J. curcas kernel slurries when incubated at 30 °C or 37 °C. However, at higher temperature (50 °C), thermophilic bacterial strains present inside crabs played a significant role in the extraction of oil from both oilseeds tested. A thermophilic bacterial strain isolated from crab paste and identified based on 16s rRNA sequence as Bacillus licheniformis strain BK23, when added as starter culture, was able to liberate 60% w w^?1 oil from aqueous J. curcas kernel slurry after 24 h at 50 °C. Further studies of BK23 and extraction process optimization are the challenges to improve Jatropha oil extraction yield and process economy.     

Acid-catalyzed production of biodiesel from waste frying oil

The reaction kinetics of acid-catalyzed transesterification of waste frying oil in excess methanol to form fatty acid methyl esters (FAME), for possible use as biodiesel, was studied. Rate of mixing, feed composition (molar ratio oil:methanol:acid) and temperature were independent variables. There was no significant difference in the yield of FAME when the rate of mixing was in the turbulent range 100 to 600 rpm. The oil:methanol:acid molar ratios and the temperature were the most significant factors affecting the yield of FAME. At 70 °C with oil:methanol:acid molar ratios of 1:245:3.8, and at 80 °C with oil:methanol:acid molar ratios in the range 1:74:1.9–1:245:3.8, the transesterification was essentially a pseudo-first-order reaction as a result of the large excess of methanol which drove the reaction to completion (99±1% at 4 h). In the presence of the large excess of methanol, free fatty acids present in the waste oil were very rapidly converted to methyl esters in the first few minutes under the above conditions. Little or no monoglycerides were detected during the course of the reaction, and diglycerides present in the initial waste oil were rapidly converted to FAME.     

Nanostructured PbO materials obtained in situ by spray solution technique for Li-ion batteries

This paper describes a systematic study of the effect of various spray pyrolysis parameters, such as temperature, solution concentration and solution flow rate on the morphology, crystallization process, crystal size, specific surface area and electrochemical performance of in situ prepared α-PbO spherically agglomerated nano-structured powders. Different analytical methods such as XRD, SEM, TEM, BET gas sorption specific surface area measurements and electrochemical tests were performed. Crystallites in the range of 20–120 nm and easily dispersed powders were reproducibly prepared by optimization of the spray conditions. An increase of the temperature from 600 to 800 °C was found to lead to a three times increase in the average crystal size, from 31 to 102 nm. An increase of concentration from 0.15 to 0.5 M dramatically suppresses the crystal size from 127 to 25 nm. The BET surface area of sprayed PbO powders is increased up to 6.6 m² g⁻¹. For such PbO powders applied as anode materials in Li-ion batteries, we have managed to retain a reversible capacity above 60 mAh g⁻¹ beyond 50 cycles.