Showing papers in "Energy & Fuels in 2008"
TL;DR: Biodiesel is a domestic and renewable alternative with the potential to replace some of the petrodiesel market as mentioned in this paper, which is obtained from vegetable oils, animal fats, or other sources with a significant content of triacylglycerols by means of a transesterification reaction.
Abstract: Biodiesel is a domestic and renewable alternative with the potential to replace some of the petrodiesel market. It is obtained from vegetable oils, animal fats, or other sources with a significant content of triacylglycerols by means of a transesterification reaction. The fatty acid profile of biodiesel thus corresponds to that of the parent oil or fat and is a major factor influencing fuel properties. Besides being renewable and of domestic origin, advantages of biodiesel compared to petrodiesel include biodegradability, higher flash point, reduction of most regulated exhaust emissions, miscibility in all ratios with petrodiesel, compatibility with the existing fuel distribution infrastructure, and inherent lubricity. Technical problems with biodiesel include oxidative stability, cold flow, and increased NOx exhaust emissions. Solutions to one of these problems often entail increasing the problematic behavior of another property and have included the use of additives or modifying the fatty acid compositi...
1,258 citations
TL;DR: The authors reviewed acid and basic heterogeneous catalyst performances for biodiesel production, examining both scientific and patent literature, and concluded that a solid heterogeneous catalysts could reduce its price, becoming competitive with diesel also from a financial perspective.
Abstract: The production of biodiesel is greatly increasing due to its enviromental benefits However, production costs are still rather high, compared to petroleum-based diesel fuel The introduction of a solid heterogeneous catalyst in biodiesel production could reduce its price, becoming competitive with diesel also from a financial point of view Therefore, great research efforts have been underway recently to find the right catalysts This paper will be concerned with reviewing acid and basic heterogeneous catalyst performances for biodiesel production, examining both scientific and patent literature
759 citations
TL;DR: In this paper, the authors proposed an alternative to petroleum-derived fuels and chemicals using renewable energy sources such as biomass, which can also serve as a feedstock for the synthesis of a variety of industrial chemicals and polymers.
Abstract: Alternatives to petroleum-derived fuels and chemicals are being sought in an effort to improve air quality and increase energy security through development of novel technologies for the production of synthetic fuels and chemicals using renewable energy sources such as biomass. In this context, ethanol is being considered as a potential alternative synthetic fuel to be used in automobiles or as a potential source of hydrogen for fuel cells as it can be produced from biomass. Renewable ethanol can also serve as a feedstock for the synthesis of a variety of industrial chemicals and polymers. Currently, ethanol is produced primarily by fermentation of biomass-derived sugars, especially those containing six carbons, whereas 5-carbon sugars and lignin, which are also present in the biomass, remain unusable. Gasification of biomass to syngas (CO + H2), followed by catalytic conversion of syngas, could produce ethanol in large quantities. However, the catalytic conversion of syngas to ethanol remains challenging,...
725 citations
TL;DR: In this article, the main kinetic features of biomass pyrolysis, devolatilization, and the gas phase reactions of the released species are analyzed in a detailed manner.
Abstract: This paper analyzes the main kinetic features of biomass pyrolysis, devolatilization, and the gas phase reactions of the released species. Three complex steps are faced in sequence: the characterization of biomasses, the description of the release of the species, and finally, their chemical evolution in the gas phase. Biomass is characterized as a mixture of reference constituents: cellulose, hemicellulose, and lignin. This assumption is verified versus experimental data, mainly relating to thermal degradation of different biomasses. Devolatilization of biomasses is a complex process in which several chemical reactions take place in both the gas and the condensed phase alongside the mass and thermal resistances involved in the pyrolysis process. A novel characterization of the released species is applied in the proposed devolatilization models. The successive gas phase reactions of released species are included into an existing detailed kinetic scheme of pyrolysis and oxidation of hydrocarbon fuels. Compa...
636 citations
TL;DR: There are many sludge management options in which production of energy (heat, electricity, or biofuel) is one of the key treatment steps as discussed by the authors and the most important options are anaerobic digestion, co-digestion, incineration in combination with energy recovery, coincineration in coal-fired power plants, and co-incining with organic waste focused on energy recovery.
Abstract: Treatment of municipal wastewater results worldwide in the production of large amounts of sewage sludge. The major part of the dry matter content of this sludge consists of nontoxic organic compounds, in general a combination of primary sludge and secondary (microbiological) sludge. The sludge also contains a substantial amount of inorganic material and a small amount of toxic components. There are many sludge-management options in which production of energy (heat, electricity, or biofuel) is one of the key treatment steps. The most important options are anaerobic digestion, co-digestion, incineration in combination with energy recovery, co-incineration in coal-fired power plants, co-incineration in combination with organic waste focused on energy recovery, use as an energy source in the production of cement or building materials, pyrolysis, gasification, supercritical (wet) oxidation, hydrolysis at high temperature, production of hydrogen, acetone, butanol, or ethanol, and direct generation of electrical energy by means of specific micro-organisms. Incineration and co-incineration with energy recovery and use of sewage sludge in the production of Portland cement are applied on a large scale. In these processes, the toxic organics are destructed and the heavy metals are immobilized in the ash or cement. The energy efficiency of these processes strongly depends upon the dewatering and drying step. It is expected that these applications will strongly increase in the future. Supercritical wet oxidation is a promising innovative technology but is still in the development stage. With the exception of biogas production, the other biological methods to produce energy are still in the initial research phase. Production of biogas from sewage sludge is already applied worldwide on small, medium, and large scales. With this process, a substantial experience exists and it is expected that this application is getting more and more attention. Besides the increasing focus on the recovery and reuse of energy, inorganics, and phosphorous, there is also an increasing focus to solve completely the problem of the toxic organics and inorganic compounds in sludge. In the assessment and selection of options for energy recovery by means of biological methods, this aspect has to be taken into account.
485 citations
TL;DR: In this article, the authors summarized the decomposition mechanisms and hydrolysis products of cellulose, hemicellulose, and lignocellulosic biomass materials under various conditions in hot-compressed water.
Abstract: Biomass hydrolysis extracts, particularly sugars and other useful derivatives, are important products for further conversion to produce biofuels. The past 2 decades have witnessed significant research and development activities using hot-compressed water for the hydrolysis and conversion of cellulose, hemicellulose, and lignocellulosic biomass materials. This paper summarizes the decomposition mechanisms and hydrolysis products of these materials under various conditions in hot-compressed water. Key factors determining hydrolysis behavior in hot-compressed water are also discussed. Comparisons are made between hydrolysis in hot-compressed water and hydrolysis using other technologies, including acid hydrolysis, alkaline hydrolysis, and enzymatic hydrolysis. Advantages, disadvantages, typical operation conditions, products properties, and applicability are summarized. Key research issues on hydrolysis in hot-compressed water are identified, and future research prospects to further improve the technology ar...
449 citations
TL;DR: In this article, a continuous auger was used to produce bio-oil at 450 °C by fast pyrolysis in a continuously auger reactor, using four feed stocks: pine wood, pine bark, oak wood, and oak bark.
Abstract: Bio-oil was produced at 450 °C by fast pyrolysis in a continuous auger reactor. Four feed stocks were used: pine wood, pine bark, oak wood, and oak bark. After extensive characterization of the whole bio-oils and their pyrolytic lignin-rich ethyl acetate fractions by gas chromatography/mass spectrometry (GC/MS), gel permeation chromatography (GPC), calorific values, viscosity dependences on shear rates and temperatures, elemental analyses, 1H and 13C NMR spectroscopy, water analyses, and ash content, these bio-oils were shown to be comparable to bio-oils produced by fast pyrolysis in fluidized bed and vacuum pyrolysis processes. This finding suggests that portable auger reactors might be used to produce bio-oil at locations in forests to generate bio-oil on-site for transport of the less bulky bio-oil (versus raw biomass) to biorefineries or power generation units. The pyrolysis reported herein had lower heat transfer rates than those achieved in fluidized bed reactors, suggesting significant further impr...
445 citations
TL;DR: In this paper, the authors explored the mechanisms of biogas yield enhancement through solid-state sodium hydroxide (NaOH) pretreatment of rice straw during anaerobic digestion and found that the changes of chemical structures and physical characteristics of lignin, hemicellulose, and cellulose made rice straw become more available and biodegradable.
Abstract: The biogas yield of rice straw during anaerobic digestion can be substantially increased through solid-state sodium hydroxide (NaOH) pretreatment. This study was conducted to explore the mechanisms of biogas yield enhancement. The chemical compositions of the pretreated rice straw were first analyzed. Fourier transform infrared (FTIR), hydrogen-1 nuclear magnetic resonance spectroscopy ( 1 H NMR), X-ray diffraction (XRD), and gas permeation chromatography (GPC) were then used to investigate the changes of chemical structures and physical characteristics of lignin, hemicellulose, and cellulose. The results showed that the biogas yield of 6% NaOH-treated rice straw was increased by 27.3-64.5%. The enhancement of the biogas yield was attributed to the improvement of biodegradability of the rice straw through NaOH pretreatment. Degradation of 16.4% cellulose, 36.8% hemicellulose, and 28.4% lignin was observed, while water-soluble substances were increased by 122.5%. The ester bond of lignin-carbohydrate complexes (LCCs) was destroyed through the hydrolysis reaction, releasing more cellulose for biogas production. The linkages of interunits and the functional groups of lignin, cellulose, and hemicellulose were either broken down or destroyed, leading to significant changes of chemical structures. The original lignin with a large molecular weight and three-dimensional network structure became one with a small molecular weight and linear structure after NaOH pretreatment. The cellulosic crystal style was not obviously changed, but the crystallinity of cellulose increased. The changes of chemical compositions, chemical structures, and physical characteristics made rice straw become more available and biodegradable and thus were responsible for the enhancement of the biogas yield.
405 citations
TL;DR: The Nafion 117 membrane used in this study was found to be quite permeable to oxygen and the oxygen mass transfer coefficient (OMT) was estimated as 2.80 × 10−4 cm/s and DO = 5.35 × 10 −6 cm2/s, respectively when a 50 mM phosphate buffer was used as the catholyte as discussed by the authors.
Abstract: Proton exchange membranes (PEMs) are one of the most important components in microbial fuel cells (MFCs), since PEMs physically separate the anode and cathode compartments while allowing protons to transport to the cathode in order to sustain an electrical current. The Nafion 117 membrane used in this study is generally regarded as having excellent proton conductivity, though many problems for its application in MFCs remain. We investigated problems associated with Nafion including: oxygen leakage from cathode to anode, substrate loss, cation transport and accumulation rather than protons, and biofouling. It was found that Nafion was quite permeable to oxygen. The oxygen mass transfer coefficient (KO) and the oxygen diffusion coefficient (DO) for Nafion was estimated as KO = 2.80 × 10−4 cm/s and DO = 5.35 × 10−6 cm2/s, respectively when a 50 mM phosphate buffer was used as the catholyte. The MFC with distilled water instead of phosphate buffer showed similar values (KO = 2.77 × 10−4 cm/s, DO = 5.27 × 10−6...
392 citations
TL;DR: In this article, a detailed chemical kinetic mechanism for hydrocarbon oxidation in an atmospheric-pressure flow reactor has been studied experimentally under highly diluted conditions in N2 and CO2, respectively.
Abstract: The oxidation of methane in an atmospheric-pressure flow reactor has been studied experimentally under highly diluted conditions in N2 and CO2, respectively. The stoichiometry was varied from fuel-lean to fuel-rich, and the temperatures covered the range 1200–1800 K. The results were interpreted in terms of a detailed chemical kinetic mechanism for hydrocarbon oxidation. On the basis of results of the present study, it can be expected that oxy-fuel combustion will lead to strongly increased CO concentrations in the near-burner region. The CO2 present will compete with O2 for atomic hydrogen and lead to formation of CO through the reaction CO2 + H ⇌ CO + OH. Reactions of CO2 with hydrocarbon radicals may also contribute to CO formation. The most important steps are those of singlet and triplet CH2 with CO2, while other radicals such as CH3 and CH are less important for consuming CO2. The high local CO levels may have implications for near-burner corrosion and slagging, but increased problems with CO emissi...
377 citations
TL;DR: In this article, 3-aminopropyl-triethoxysilane (APTS)-modified carbon nanotubes (CNTs), granular activated carbon (GAC), and zeolites were selected as adsorbents to study their physicochemical properties and adsorption behaviors of CO2 from gas streams.
Abstract: Carbon nanotubes (CNTs), granular activated carbon (GAC), and zeolites were modified by 3-aminopropyl-triethoxysilane (APTS) and were selected as adsorbents to study their physicochemical properties and adsorption behaviors of CO2 from gas streams. The surface nature of these adsorbents was changed after the modification, which make them adsorb more CO2 gases. Under the same conditions, the modified CNTs possess the greatest adsorption capacity of CO2, followed by the modified zeolites and then the modified GAC. The mechanism of CO2 adsorption on these adsorbents appears mainly attributable to physical force, which makes regeneration of spent adsorbents at a relatively low temperature become feasible. The APTS-modified CNTs show good performance of CO2 adsorption as compared to many types of modified carbon and silica adsorbents reported in the literature. This suggests that the APTS-modified CNTs are efficient CO2 adsorbents and that they possess potential applications for CO2 capture from gas streams.
TL;DR: In this article, the chemical composition of bio-oil is compared with what is known about the compositions of these feedstocks, including switchgrass and alfalfa, by using GC-MS and HPLC.
Abstract: Bio-oils from the fast pyrolysis of switchgrass forage and two sets of alfalfa stems (from two stages of development—bud and full flower stages) have been analyzed by wet-chemical methods, GC-MS, and HPLC. The chemical composition of bio-oil is important because it may give insights into its quality, stability, or suitability for downstream upgrading. Pyrolysis experiments were conducted at 500 °C under a nitrogen atmosphere in 2.5 kg/h fluidized bed reactor. A total of 62 chemical species were positively identified in the liquids. Of the identified compounds, 27 have been quantified. The chemical compositions of the bio-oils are compared with what is known about the compositions of these feedstocks. While the compositions of the bio-oil from the two alfalfa stems were similar, there were numerous differences in the compositions of the alfalfa and switchgrass bio-oils. Noted are the higher levels of nitrogen, water, and aromatic hydrocarbons in bio-oils produced from alfalfa stems than from switchgrass an...
TL;DR: In this article, a liquefaction process was proposed to depolymerize natural biopolymer lignin into a liquid bio-oil with a very low oxygen content, suitable as a blending component to be combined with conventional fossil fuels for motor fuel applications.
Abstract: This paper reports a novel liquefaction process that is capable of depolymerizing the natural biopolymer lignin into a liquid bio-oil with a very low oxygen content, suitable as a blending component to be combined with conventional fossil fuels for motor fuel applications. During the conversion, both depolymerization and removal of oxygen by formation of water occur in a single step. Formic acid serves as both the hydrogen donor and reaction medium in the pyrolysis/solvolysis process. Using an alcohol as cosolvent can improve the liquid yields and H/C ratios. Very little coke (5%) is produced. The liquids produced comprise two easily separable phases, where the lighter organic phase consists mainly of low molecular weight alkylphenols and C8−C10 aliphatics. The process is developed to be combined with ethanol production from lignocellulosic carbohydrates in a biorefinery concept aimed at converting all fractions of the wood into renewably sourced liquid fuels.
TL;DR: In this paper, the authors report on hypergolicity investigations of other fuel-rich anions, especially the dicyanamide anion, and a new path for transitioning these materials into bipropellant applications seems clear.
Abstract: The aim of this paper is to report on hypergolicity investigations of other fuel-rich anions, especially the dicyanamide anion. With the discovery of these ionic liquid hypergols, a new path for transitioning these materials into bipropellant applications seems clear. It is expected that these systems can now be fine-tuned for energy content, performance, and desirable physical properties and that they could replace state-of-art; highly toxic hydrazine and its derivatives
TL;DR: In this article, the authors obtained quantitative data on the release of inorganic elements during wood combustion and investigated the influence of fuel composition, including wood chips from spruce and beech, bark, and fiber board.
Abstract: Combustion of wood for heat and power production may cause problems such as ash deposition, corrosion, and harmful emissions of gases and particulate matter. These problems are all directly related to the release of inorganic elements (in particular Cl, S, K, Na, Zn, and Pb) from the fuel to the gas phase. The aims of this study are to obtain quantitative data on the release of inorganic elements during wood combustion and to investigate the influence of fuel composition. Quantitative release data were obtained by pyrolyzing and subsequently combusting small samples of wood (∼30 g) at various temperatures in the range of 500–1150 °C in a laboratory-scale tube reactor and by performing mass balance calculations based on the weight measurements and chemical analyses of the wood fuels and the residual ash samples. Four wood fuels with different ash contents and inorganic compositions were investigated, including wood chips from spruce and beech, bark, and fiber board. The results showed a high release of Cl ...
TL;DR: In this paper, a sustainable esterification process based on catalytic reactive distillation is proposed for biodiesel production, where metal oxide solid acid catalysts are used to find catalysts that are active, selective, and stable.
Abstract: The properties and use of biodiesel as a renewable fuel as well as the problems associated with its current production processes are outlined. A novel sustainable esterification process based on catalytic reactive distillation is proposed. The pros and cons of manufacturing biodiesel via fatty acid esterification using metal oxide solid acid catalysts are investigated. Finding catalysts that are active, selective, and stable under the process conditions is the main challenge for a successful design. The best candidates are metal oxides such as niobic acid, sulfated zirconia, sulfated titania, and sulfated tin oxide. Rigorous process simulations show that combining metal oxide catalysts with reactive distillation technology is a feasible and advantageous solution for biodiesel production.
TL;DR: In this article, single, binary, ternary, and quaternary mixtures of canola (low erucic acid rapeseed), palm, soybean, and sunflower (high oleic acid) oil methyl esters (CME, PME, SME, and SFME, respectively) were prepared, and important fuel properties were measured, such as oil stability index (OSI), cold filter plugging point (CFPP), cloud point (CP), pour point (PP), kinematic viscosity (40 °C), lubricity
Abstract: Single, binary, ternary, and quaternary mixtures of canola (low erucic acid rapeseed), palm, soybean, and sunflower (high oleic acid) oil methyl esters (CME, PME, SME, and SFME, respectively) were prepared, and important fuel properties were measured, such as oil stability index (OSI), cold filter plugging point (CFPP), cloud point (CP), pour point (PP), kinematic viscosity (40 °C), lubricity, acid value (AV), and iodine value (IV). The fuel properties of SME were improved through blending with CME, PME, and SFME to satisfy the IV ( 6 h) specifications contained within EN 14214, the biodiesel standard from the European Committee for Standardization. SME was satisfactory according to ASTM D6751, the American biodiesel standard, with regard to OSI (>3 h). The CFPP of PME was improved by up to 15 °C through blending with CME. Statistically significant relationships were elucidated between OSI and IV, OSI and saturated fatty acid methyl ester (SFAME) content, OSI and CFPP, CFPP and IV, and CFPP...
TL;DR: In this paper, the results of the study of a new oxygenate synthesized from crude glycerin as a biodiesel additive were presented. And the results reveal that new acetal (2,2-dimethyl-1,3-dioxolan-4-yl)methyl acetate not only improves biodiesel viscosity but also meets the requirements established by diesel and biodiesel fuels by the European and American Standards (EN 14214 and ASTM D6751, respectively) for other important parameters, such as flash point and oxidation stability, that have not
Abstract: The biodiesel production increase in the last few years has led to an overproduction of glycerin, the main byproduct of this industry. To avoid a glut in the glycerin market, many researchers are exploring new uses for this product. One of the most promising research areas is the use of glycerin-based additives to improve biodiesel properties. In this context, this paper presents the results of the study of a new oxygenate synthesized from crude glycerin as a biodiesel additive. The obtained results reveal that new acetal (2,2-dimethyl-1,3-dioxolan-4-yl)methyl acetate not only improves biodiesel viscosity but also meets the requirements established by diesel and biodiesel fuels by the European and American Standards (EN 14214 and ASTM D6751, respectively) for other important parameters, such as flash point and oxidation stability, that have not been studied before with previous acetals. The comparison study between this new acetal and the known additive glycerol triacetate (triacetin) demonstrates that th...
TL;DR: In this paper, the evolution of bio-oil obtained from the fast pyrolysis of Mallee woody biomass as a function of temperature between 350 and 580 °C was reported.
Abstract: This paper reports the evolution of the composition of bio-oil obtained from the fast pyrolysis of Mallee woody biomass as a function of temperature between 350 and 580 °C. Several analytical techniques were used to quantify bio-oil composition. For the volatile components, the results obtained by gas chromatography−mass spectrometry and Karl Fischer titration agree very well with those obtained by thermogravimetric analyses. However, for the heavy components, especially lignin-derived oligomers, synchronous UV-fluorescence spectroscopy and thermogravimetric analysis give more reliable results than the precipitation in cold water. Our results indicate that the accuracy of the precipitation methods to quantify lignin-derived oligomer in bio-oil is limited by the relatively large amounts of small oligomers remaining soluble in a metastable form in cold water. A maximum in the yield of lignin-derived oligomers was observed between 450 and 500 °C. In fact, most of the increases in the yield of bio-oil with in...
TL;DR: In this article, a single-particle reactor provided drying, pyrolysis and reaction rate data from poplar particle samples with sizes ranging from 3 to 15 mm, and the authors provided a comprehensive analysis of entrained-flow biomass particle combustion processes.
Abstract: This investigation provides a comprehensive analysis of entrained-flow biomass particle combustion processes. A single-particle reactor provided drying, pyrolysis, and reaction rate data from poplar particle samples with sizes ranging from 3 to 15 mm. A one-dimensional particle model simulates the drying, rapid pyrolysis, gasification, and char oxidation processes of particles with different shapes. The model characterizes particles in three basic shapes (sphere, cylinder, and flat plate). With the particle geometric information (particle aspect ratio, volume, and surface area) included, this model can be modified to simulate the combustion process of biomass particles of any shape. The model also predicts the surrounding flame combustion behaviors of a single particle. Model simulations of the three shapes agree nearly within experimental uncertainty with the data. Investigations show that spherical mathematical approximations for fuels that either originate in or form aspherical shapes during combustion...
TL;DR: Sodium hydroxide (NaOH) was used to pretreat corn stover in solid state at ambient temperature to improve biodegradability and anaerobic biogas production as mentioned in this paper.
Abstract: Sodium hydroxide (NaOH) was used to pretreat corn stover in solid state at ambient temperature to improve biodegradability and anaerobic biogas production. Four NaOH doses of 4%, 6%, 8%, and 10% on...
TL;DR: In this article, the influence of fuel−ash composition on residual ash and slag behavior was determined in a commercial under-fed pellet burner installed in a reference boiler, and continuous measurements of O2, CO, CO2, HCl, SO2, and total particle matter mass concentrations were determined in the exhaust gas directly after the boiler.
Abstract: Limited availability of sawdust and planer shavings and an increasing demand for biomass pellets in Europe are pushing the market toward other, more problematic raw materials with broader variation in total fuel ash content and composition of the ash forming elements as well as in their slagging tendencies. The main objective in the present work was therefore to determine the influence of fuel−ash composition on residual ash and slag behavior. Twelve different biomass pellets were used: reed canary grass (two different samples), hemp (two different samples), wheat straw, salix, logging residues (two different samples), stem wood (sawdust) as well as spruce, pine, and birch bark. The different pellet qualities were combusted in a commercial under fed pellet burner (20 kW) installed in a reference boiler. Continuous measurements of O2, CO, CO2, HCl, SO2, and total particle matter mass concentrations were determined in the exhaust gas directly after the boiler. The collected slag deposits, the corresponding ...
TL;DR: In this article, a woody biomass (Jack pine sawdust) in sub/near-critical water without and with catalysts (alkaline earth and iron ions) has been investigated at temperatures of 280-380 °C.
Abstract: Direct liquefaction of a woody biomass (Jack pine sawdust) in sub/near-critical water without and with catalysts (alkaline earth and iron ions) has been investigated at temperatures of 280–380 °C. Heavy oils with a high caloric value of 30–35 MJ/kg (much greater than that of the crude wood sample used) were obtained, along with water soluble oils with a caloric value of 19–25 MJ/kg. The yields of heavy oil and total oil products tended to maximize in the temperature range of 280–340 °C for all the liquefaction operations regardless of the presence of a catalyst or the type of catalyst. All the catalysts tested, i.e., Ca(OH)2, Ba(OH)2, and FeSO4, were found effective for enhancing the formation of heavy oil products at 280–340 °C, while they significantly promoted the formation of gas and water at >340 °C. The yield of heavy oil in the operation at 300 °C for 30 min was improved significantly from around 30% without catalyst to greater than 45% by Ba(OH)2. The maximum yield of total oil products reached 51...
TL;DR: In this article, the affinity of SO42−, Ca2+, and Mg2+ toward the surface of reservoir limestone cores at temperatures ranging from room temperature to 130 °C was evaluated.
Abstract: Seawater is characterized as an enhanced oil recovery (EOR) fluid for hot, fractured chalk oil reservoirs because it is able to modify the wetting conditions and improve the displacement of oil. The chemical mechanism for the wettability alteration has been described previously, and it was verified that Ca2+, Mg2+, and SO42− played an important role because of their reactivity toward the chalk surface. Chalk, which is purely biogenic CaCO3, consists of fragmentary parts of calcite skeletons produced by plankton algae known as coccolithophorids, and it is believed to have a more reactive surface than ordinary limestone. To validate seawater as an EOR fluid also for limestone and dolomite, the affinities of these ions toward the rock surfaces must be evaluated. The present paper describes some preliminary experimental studies of the affinity of SO42−, Ca2+, and Mg2+ toward the surface of reservoir limestone cores at temperatures ranging from room temperature to 130 °C. The results confirmed that the ions in...
TL;DR: In this article, two-step thermochemical cycles for splitting CO2 with Zn/ZnO and FeO/Fe3O4 redox pairs using concentrated solar energy are considered.
Abstract: Two-step thermochemical cycles for splitting CO2 with Zn/ZnO and FeO/Fe3O4 redox pairs using concentrated solar energy are considered. Thermogravimetric-based kinetic analyses were performed for the reduction of CO2 to CO with Zn and FeO. Both reactions are characterized by an initial fast interface-controlled regime followed by a slow diffusion-controlled regime, which are described using a shell−core kinetic model. In the interface-controlled regime, a power rate law is applied with apparent activation energies 113.7 and 73.4 kJ mol−1, and corresponding reaction orders 0.339 and 0.792, for the Zn/CO2 and FeO/CO2 systems, respectively. In the diffusion-controlled regime, limited by the ion mobility through the oxide shells, the apparent activation energies are 162.3 kJ mol−1 for Zn/CO2 and 106.4 kJ mol−1 for FeO/CO2. Additional reaction mechanisms above the Zn melting point for Zn/CO2 reactions are postulated.
TL;DR: In this article, supported CaO/MgO catalysts were used as the catalyst of the transesterification of rapeseed oil with methanol, and the results of comparative experiments and catalyst characterization, such as XRD, CO2-TPD, BET, and AAS, showed that the activity of CaO catalyst is associated with their alkalinity.
Abstract: Supported CaO/MgO catalysts were used as the catalyst of the transesterification of rapeseed oil with methanol The supported catalyst showed a higher activity than pure CaO and was easily separated from the product mixture The results of comparative experiments and catalyst characterization, such as XRD, CO2-TPD, BET, and AAS, showed that the activity of CaO catalysts is associated with their alkalinity The preparation method of this catalyst was optimized, and furthermore, the reaction parameters were investigated With the CaO/MgO catalyst so obtained, the conversion of rapeseed oil reached 92% at 645 °C The supported basic catalyst was found to be easily contaminated by the gaseous poisons in air, such as O2, CO2, and H2O, and as a result, a thermal treatment was required before the reaction to activate the catalyst
TL;DR: In this article, both experimental and mathematical modeling approaches are employed to study the combustion characteristics of a single biomass particle ranging in size from 10 µm to 20 mm, and different subprocesses such as moisture evaporation, devolatilization, tar cracking, gas-phase reactions, and char gasification are examined.
Abstract: Biomass is one of the important renewable energy sources. Biomass fuels exhibit a range of chemical and physical properties, particularly size and shape. Investigations of the behavior of a single biomass particle are fundamental to all practical applications, including both packed and fluidized-bed combustion, as well as suspended and pulverized fuel (pf) combustion. In this paper, both experimental and mathematical modeling approaches are employed to study the combustion characteristics of a single biomass particle ranging in size from 10 µm to 20 mm. Different subprocesses such as moisture evaporation, devolatilization, tar cracking, gas-phase reactions, and char gasification are examined. The sensitivity to the variation in model parameters, especially the particle size and heating rates, is investigated. The results obtained from this study are useful in assessing different combustion systems using biomass as a fuel. It helps to clarify the situations where the thermally thin and thermally thick case...
TL;DR: In this paper, FeIII-containing ionic liquids (ILs) were used as effective extractants for the desulfurization of a model oil containing dibenzothiophene (DBT).
Abstract: FeIII-containing ionic liquids (ILs), prepared from the reaction of anhydrous FeCl3 and imidazolium chloride ([imidazolium]Cl), were used as effective extractants for the desulfurization of a model oil containing dibenzothiophene (DBT). The amount of DBT extracted increased with an increasing molar ratio of FeCl3/[imidazolium]Cl. The ability of the ILs to extract DBT seems to be attributed to the combined effects of Lewis acidity and fluidity of ILs.
TL;DR: In this article, a method was developed to introduce ammonia into the intake manifold and to inject diesel fuel or biodiesel directly into the cylinder to ignite the mixture, which was proven successful in a multicylinder, turbocharged diesel engine.
Abstract: This study demonstrated the feasibility of ammonia combustion in compression-ignition diesel engines. Ammonia combustion does not produce carbon dioxide, a known greenhouse gas that contributes to global warming. Using this idea, a method was developed to introduce ammonia into the intake manifold and to inject diesel fuel or biodiesel directly into the cylinder to ignite the mixture. This dual-fuel approach was chosen because ammonia has a high resistance to autoignition. This approach was proven successful in a multicylinder, turbocharged diesel engine. The system developed required only a slight modification of the intake to implement the ammonia fuel line. The existing diesel fuel injection system remained unchanged. A liquid ammonia tank was used for fuel storage, and a high pressure relief valve regulated the ammonia flow rate. Engine combustion phasing (e.g., ignition) was controlled by diesel fuel injection. Both experiments and chemical kinetic studies were carried out for different diesel/ammoni...
TL;DR: In this paper, three oxygen carriers for chemical-looping combustion and chemicallooping reforming have been investigated in a small circulating fluidized-bed reactor, where the conversion of natural gas into products was 96−100% depending on oxygen carrier and experimental conditions.
Abstract: Three oxygen carriers for chemical-looping combustion and chemical-looping reforming have been investigated in a small circulating fluidized-bed reactor. N2AM1400 was produced by freeze granulation with MgAl2O4 as a support material and had a NiO content of 20%. Ni18-αAl was produced by impregnation onto α-Al2O3 and had a NiO content of 18%. Ni21-γAl was produced by impregnation onto γ-Al2O3 and had a NiO content of 21%. Over 160 h of operation has been recorded. The conversion of natural gas into products was 96−100% depending on oxygen carrier and experimental conditions. For chemical-looping combustion, N2AM1400 and Ni21-γAl provided poor selectivity toward CO2 and H2O while Ni18-αAl initially showed very high selectivity, which declined as a function of time. For chemical-looping reforming, operating the reactor at the desired process parameters, which was a fuel reactor temperature of 950 °C and an air factor of 0.30, was possible with all of the tested oxygen-carrier materials. When only natural gas was used as fuel, there was significant formation of solid carbon in the fuel reactor for Ni18-αAl and Ni21-γAl. Adding 30% steam or CO2 to the fuel removed or decreased the carbon formation. During the course of the experiments, N2AM1400 and Ni18-αAl retained their physical and chemical structure, while Ni21-γAl displayed a significant reduction in porosity but remained highly reactive.