Showing papers in "Energy & Fuels in 2009"
TL;DR: In this paper, the suggested mechanisms for the wettability modification in the two types of reservoir rocks were discussed both in carbonates and especially in sandstones, and the suggested mechanism behind the wetability alteration promoted by the injected water has been a topic for discussion.
Abstract: Waterflooding has for a long time been regarded as a secondary oil recovery method. In the recent years, extensive research on crude oil, brine, and rock systems has documented that the composition of the injected water can change wetting properties of the reservoir during a waterflood in a favorable way to improve oil recovery. Thus, injection of “smart water” with a correct composition and salinity can act as a tertiary recovery method. Economically, it is, however, important to perform a waterflood at an optimum condition in a secondary process. Examples of smart water injection in carbonates and sandstones are: (1) injection of seawater into high temperature chalk reservoirs and (2) low salinity floods in sandstone reservoirs. The chemical mechanism behind the wettability alteration promoted by the injected water has been a topic for discussion both in carbonates and especially in sandstones. In this paper, the suggested mechanisms for the wettability modification in the two types of reservoir rocks a...
518 citations
TL;DR: The objective of this work is to explore the potential of producing biodiesel fuel from this alga using different biodiesel preparation methods, including oil extraction followed by transesterification (a two-stage method) or direction transesterization of algal biomass (a one- stage method).
Abstract: Producing biofuel from microalgae has gained renewed interest recently. Schizochytrium limacinum is a heterotrophic microalga that is capable of producing high levels of biomass and total fatty aci...
495 citations
TL;DR: In this article, the use of non-edible oils to produce biodiesel is proposed, and the compromise of noninterference between land for energetic and food purposes must be addressed.
Abstract: Though a considerable number of publications about biodiesel can be found in literature, several problems remain unsolved, encompassing economical, social, and technical issues. Thus, the biodiesel industry has come under attack by some environmental associations, and subsidies for biofuel production have been condemned by some governments. Yet, biodiesel may represent a truly competitive alternative to diesel fuel, for which fuel tax exemption and subsidies to energetic crops are needed. Biodiesel must increase its popularity among social movements and governments to constitute a valid alternative of energy source. In this sense, the use of nonedible oils to produce biodiesel is proposed in the present review. Moreover, the compromise of noninterference between land for energetic and food purposes must be addressed. Concerning technical issues, it is important to consider a transesterification optimization, which is missing or incomplete for too many vegetable oils already tested. In most cases, a common...
439 citations
TL;DR: In this paper, the potential for the metal organic framework (MOF) Cu-BTC to selectively adsorb and separate CO2 is considered, and isotherms for CO2, CH4, and N2 were measured from 0 to 15 bar and at temperatures between 25 and 105 °C.
Abstract: The potential for the metal organic framework (MOF) Cu-BTC to selectively adsorb and separate CO2 is considered. Isotherms for CO2, CH4, and N2 were measured from 0 to 15 bar and at temperatures between 25 and 105 °C. The isotherms suggest a much higher working capacity (×4) for CO2 adsorption on Cu-BTC relative to the benchmark zeolite 13X over the same pressure range. Higher CO2/N2 and CO2/CH4 selectivities in the higher pressure range (1−15 bar) and with lower heats of adsorption were also demonstrated. Cu-BTC was observed to be stable in O2 at 25 °C, but its crystallinity was reduced in humid environments. The CO2 adsorption capacity was progressively reduced upon cyclic exposure to water vapor at low relative humidity (<30%), but leveled out at 75% of its original value after several water adsorption/desorption cycles.
393 citations
TL;DR: In this paper, three model compounds were chosen to represent cellulose, hemicellulose, and lignin components in the case of lignocellulosic biomass.
Abstract: Bio-oil (product liquids from fast pyrolysis of biomass) is a complex mixture of oxygenates derived from the thermal breakdown of the biopolymers in biomass. In the case of lignocellulosic biomass, the structures of three major components, cellulose, hemicellulose and lignin, are well-represented by the bio-oil components. To study the chemical mechanisms of catalytic hydroprocessing of bio-oil, three model compounds were chosen to represent those components. Guaiacol represents the large number of mono- and dimethoxy phenols found in bio-oil derived from soft- or hardwood, respectively. Furfural represents a major pyrolysis product group from cellulosics. Acetic acid is a major product from biomass pyrolysis, derived from the hemicellulose, which has important impacts on the further processing of the bio-oil because of its acidic character. These three compounds were processed using a palladium or ruthenium catalyst over a temperature range from 150 to 300 °C. The batch reactor was sampled during each te...
361 citations
TL;DR: A comprehensive review of the literature on catalytic conditioning of biomass-derived syngas can be found in this paper, with an emphasis on tar destruction and steam reforming catalysts.
Abstract: Thermochemical conversion of biomass to create fuels and chemical products may be achieved through the gasification route via syngas. The resulting biomass-derived raw syngas contains the building blocks of carbon monoxide and hydrogen as well as undesired impurities, such as tars, hydrocarbons, hydrogen sulfide, ammonia, hydrogen chloride, and other trace contaminants. These impurities require removal, usually through catalytic conditioning, to produce a quality syngas for end-use synthesis of liquid fuels, such as mixed alcohols and Fischer−Tropsch liquids. In the past decade, significant research attention has been focused on these catalytic processes. This contribution builds on previous reviews and focuses on capturing the work on catalytic conditioning of biomass-derived syngas that have been performed since the Dayton review in 2002, with an emphasis on tar destruction and steam reforming catalysts. This review organizes and discusses the investigations of catalytic conditioning of biomass-derived ...
354 citations
TL;DR: In this article, Ru/C was used in hydrogenation of levulinic acid to produce γ-valerolactone, and the reaction pathway for the hydrogenation was proposed.
Abstract: Ru/C catalyst was used in hydrogenation of levulinic acid to produce γ-valerolactone. The conversion rate and the selectivity of levulinic acid to γ-valerolactone with Ru/C as catalyst were higher than those with Pd/C, Raney nickel, and Urushibara nickel. The optimum preparation conditions of γ-valerolactone by hydrogenation of levulinic acid catalyzed by Ru/C were as follows: temperature at 130 °C, hydrogen pressure at 1.2 MPa, dosage of catalyst at 5.0% (based on the mass fraction of levulinic acid), the solvent being methanol, and a reaction time of 160 min. The conversion rate of levulinic acid to γ-valerolactone was found to be 92%, and the selectivity of γ-valerolactone was 99%. The surface structure variations of the fresh and used catalysts were characterized by XRD and XPS. Furthermore, the reaction pathway for the hydrogenation of levulinic acid was proposed.
348 citations
TL;DR: In this article, the 1 H and 13 C NMR spectra were integrated over spectral regions to quantify classes of carbon and hydrogen atoms in each bio-oil sample, and DEPT spectra are used to quantify by protonation, and the number of the carbon atom in each of those classes was used to give further information on the types of molecules that are found in the biooil.
Abstract: NMR spectroscopy, including 1 H, 13 C, and DEPT spectra, was used to characterize fast-pyrolysis oils from numerous energy crops and other agricultural feedstocks. The bio-oils studied were produced from switchgrass, alfalfa stems, corn stover, guayule (whole plant and latex-extracted bagasse), and chicken litter. The 1 H and 13 C NMR spectra were integrated over spectral regions to quantify classes of carbon and hydrogen atoms in each bio-oil sample. DEPT spectra were used to quantify by protonation, and the number of the carbon atoms in each of those classes was used to give further information on the types of molecules that are found in the bio-oil. The NMR spectra of the bio-oils varied greatly. The percentage of carbons and protons in the upfield regions of the NMR spectra tracked with the energy content of the bio-oil as well as the feedstock type, but there was no such consistent trend for the aromatic content. Degrees of branching in the aliphatic portions of the bio-oils were inferred from percentages of CH1 ,C H2, and CH3 groups. Aromatic portions were found to be extremely complex, with substituted aromatic carbons outnumbering unsubstituted aromatic carbons >2:1 in most cases. Fully substituted carbons represented 27-37% of all the carbons in the sample.
306 citations
TL;DR: In this paper, the authors investigated the possibility to pretreat biomass to produce biochar as a solid biofuel to address the issues of high transport cost and poor biomass grindability, and showed that converting biomass to biochar leads to a substantial increase in fuel mass energy density from ∼10 GJ/ton of green biomass to ∼28 GJ /t of biochars prepared from pyrolysis at 320 °C, in comparison to 26 GJ 2 /t for Collie coal.
Abstract: Biomass as a fuel suffers from its bulky, fibrous, high moisture content and low-energy-density nature, leading to key issues including high transport cost and poor biomass grindability. This study investigates the possibility to pretreat biomass to produce biochar as a solid biofuel to address these issues. Biochars were produced from the pyrolysis of centimeter-sized particles of Western Australia (WA) mallee wood in a fixed-bed reactor at 300 to 500 °C and a heating rate of 10 °C/min. The data show that, at pyrolysis temperatures ≥320 °C, biochar as a fuel has similar fuel H/C and O/C ratios compared to Collie coal that is the only coal being mined in WA. Converting biomass to biochar leads to a substantial increase in fuel mass energy density from ∼10 GJ/ton of green biomass to ∼28 GJ/ton of biochars prepared from pyrolysis at 320 °C, in comparison to 26 GJ/ton for Collie coal. However, there is little improvement in fuel volumetric energy density, which is around 7−9 GJ/m3 in comparison to 17 GJ/m3 o...
283 citations
TL;DR: In this paper, a condensed overview of how Fischer−Tropsch facilities changed during the last 70 years and focusing in particular on the diesel fuel produced is presented. But the authors do not consider the use of diesel fuel in their analysis.
Abstract: Fischer−Tropsch synthesis is technically classified into two categories, the high-temperature Fischer−Tropsch (HTFT) and the low-temperature Fischer−Tropsch (LTFT) processes. The criterion for this classification is the operating temperature of the synthesis, which ranges between 310−340 °C for the HTFT process and 210−260 °C for the LTFT process. A Fischer−Tropsch facility can be divided into roughly three sections, synthesis gas (syngas) generation, FT synthesis, and refining of the synthetic crude (syncrude). Fischer−Tropsch refineries differ regarding the product upgrading, and both transportation fuels and chemicals can be produced. Regarding the FT refinery history, the configuration of each refinery also reflects the requirements of the fuel specification at that time. This paper gives a condensed overview of how Fischer−Tropsch facilities changed during the last 70 years and focuses in particular on the diesel fuel produced. Some conceptual flow schemes are additionally presented with emphasis on ...
279 citations
TL;DR: In this paper, the effect of the fuel reactor temperature on gas composition of a 10 kWth reactor with iron oxide as an oxygen carrier was experimentally investigated with a total 30 h of test was achieved with the same batch of iron oxide oxygen carrier.
Abstract: Chemical-looping combustion of biomass was carried out in a 10 kWth reactor with iron oxide as an oxygen carrier A total 30 h of test was achieved with the same batch of iron oxide oxygen carrier The effect of the fuel reactor temperature on gas composition of the fuel reactor and the air reactor, the proportion of biomass carbon reacting in the fuel reactor, and the conversion of biomass carbon to CO2 in the fuel reactor was experimentally investigated The results showed that the CO production from biomass gasification with CO2 was more temperature dependent than the CO oxidation with iron oxide in the fuel reactor, and an increase in the fuel reactor temperature produced a higher increase for the CO production from biomass gasification than for the oxidation of CO by iron oxide Although the conversion of biomass carbon to CO2 in the fuel reactor decreased with the increase of the fuel reactor temperature, there was a substantial increase in the proportion of biomass carbon reacting in the fuel react
TL;DR: In this article, the ignition of n-heptane, n-decane, N-dodecane, and n-tetradecane has been investigated in a heated shock tube.
Abstract: The ignition of n-heptane, n-decane, n-dodecane, and n-tetradecane has been investigated in a heated shock tube. n-Alkane/air mixtures at Φ = 0.25, 0.5, and 1.0 were studied in reflected shock experiments at 9−58 atm and 786−1396 K. Ignition times were measured using a combination of endwall electronically excited OH emission and sidewall pressure measurements. The measured ignition times are compared to previous data, where available, with good agreement and to several kinetic modeling predictions. The current data and the combination of the current data with previous shock tube and rapid compression machine measurements show that any differences in reactivity for C7 and larger n-alkanes is slight, within the experimental uncertainties, for n-alkane/air mixtures with common carbon content at a large range of temperatures (650−1400 K) and elevated pressures. To our knowledge, the n-tetradecane measurements presented here are the first ignition measurements to be reported for this compound. The complete da...
TL;DR: In this article, a review examines state-of-the-art mid and high-temperature sulfur sorbents that remove hydrogen sulfide (H2S) from coal gasification and may be applicable for use with biomass-derived syngas.
Abstract: This review examines state-of-the-art mid- and high-temperature sulfur sorbents that remove hydrogen sulfide (H2S) from syngas generated from coal gasification and may be applicable for use with biomass-derived syngas. Biomass feedstocks contain low percentages of protein-derived sulfur that is converted primarily to H2S, as well as small amounts of carbonyl sulfide (COS) and organosulfur compounds during pyrolysis and gasification. These sulfur species must be removed from the raw syngas before it is used for downstream fuel synthesis or power generation. Several types of sorbents based on zinc, copper, iron, calcium, manganese, and ceria have been developed over the last two decades that are capable of removing H2S from dry coal-derived syngas at mid- to high-temperature ranges. Further improvement is necessary to develop materials more suitable for desulfurization of biomass-derived syngas because of its hydrocarbon, tar, and potentially high steam content, which presents different challenges as compar...
TL;DR: In this article, solid oxide electrochemical cells with H2O−CO2−H2 mixtures at Ni-YSZ cathode and air at the LSCF-GDC anode were used to produce syngas.
Abstract: Electrolysis was carried out at 700−800 °C using solid oxide electrochemical cells with H2O−CO2−H2 mixtures at the Ni-YSZ cathode and air at the LSCF-GDC anode. (YSZ = 8 mol %, Y2O3-stabilized ZrO2, GDC = Ce0.9Gd0.1O1.95, and LSCF = La0.6Sr0.4Co0.2Fe0.8O3). The cell electrolysis performance decreased only slightly for H2O−CO2 mixtures compared to H2O electrolysis and was much better than for pure CO2 electrolysis. Mass spectrometer measurements showed increasing consumption of H2O and CO2 and production of H2 and CO with increasing electrolysis current density. Electrolyzers operated on 25% H2, 25% CO2, and 50% H2O at 800 °C and 1.3 V yielded a syngas production rate of ∼7 sccm/cm2. The use of electrolytically produced syngas for producing renewable liquid fuels is discussed; an energy-storage cycle based on such liquid fuels is CO2-neutral, similar to hydrogen, and has the potential to be more efficient and easier to implement.
TL;DR: In this article, two global multistep schemes, the two-step mechanism of Westbrook and Dryer (WD) and the four-stage mechanism of Jones and Lindstedt (JL), have been refined for oxy-fuel conditions.
Abstract: Two global multistep schemes, the two-step mechanism of Westbrook and Dryer (WD) and the four-step mechanism of Jones and Lindstedt (JL), have been refined for oxy-fuel conditions. Reference calculations were conducted with a detailed chemical kinetic mechanism, validated for oxy-fuel combustion conditions. In the modification approach, the initiating reactions involving hydrocarbon and oxygen were retained, while modifying the H2−CO−CO2 reactions in order to improve prediction of major species concentrations. The main attention has been to capture the trend and level of CO predicted by the detailed mechanism as well as the correct equilibrium concentration. A CFD analysis of a propane oxy-fuel flame has been performed using both the original and modified mechanisms. Compared to the original schemes, the modified WD mechanism improved the prediction of the temperature field and of CO in the post flame zone, while the modified JL mechanism provided a slightly better prediction of CO in the flame zone.
TL;DR: In this paper, a new apparatus designed to accommodate three different size volume beds of silica sand particles was used to study gas hydrate formation in the water-saturated sand bed, where a bulk gas phase was present above the bed and gas uptake measurements were carried out during experiments at constant temperature.
Abstract: Gas hydrate formation was studied in a new apparatus designed to accommodate three different size volume beds of silica sand particles. The sand particles have an average diameter equal to 329 μm. The hydrate was formed in the water, which occupied the interstitial space of the water-saturated silica sand bed. A bulk gas phase was present above the bed (gas cap). Gas uptake measurements were carried out during experiments at constant temperature. More than 74.0% of water conversion to hydrate was achieved in all experiments conducted with methane at 4.0 and 1.0 °C. An initial slow growth was followed by a rapid hydrate growth rate of equal magnitude for nearly all experiments until 43−53% of water was converted to hydrate. During the third and final growth stage, the final conversions were between 74 and 98% and the conversion dynamics changed. Independent verification of hydrate formation in the sand was achieved via Raman spectroscopy and morphology observations in experiments using the same sand/water ...
TL;DR: In this paper, magnetic Fe3O4 nanoparticles treated with (3-aminopropyl)triethoxysilane were used as an immobilization material for lipase.
Abstract: In this work, magnetic Fe3O4 nanoparticles treated with (3-aminopropyl)triethoxysilane were used as immobilization material Lipase was covalently bound to the amino-functionalized magnetic nanoparticles by using glutaraldehyde as a coupling reagent with the activity recovery up to 70% and the enzyme binding efficiency of 84% The binding of lipase to the magnetic particles was confirmed by enzyme assays, transmission electron microscopy, X-ray powder diffraction, and Fourier transform infrared spectra Moreover, the immobilized lipase was found to be able to catalyze the transesterification of soybean oil with methanol to produce fatty acid methyl esters (better known as biodiesel) Besides, it was determined that the conversion of soybean oil to biodiesel fuels reached over 90% by the three-step addition of methanol when 60% immobilized lipase was employed Further study showed that the immobilized lipase could be used four times without significant decrease of activity
TL;DR: In this paper, the effect of tetra-n-butyl ammonium bromide (TBAB) and tetra n-bromide ammonium fluoride (tBAF) on the hydrate formation rate, reactor space velocity, and CO2 separation efficiency was studied in a 1 L stirred reactor.
Abstract: Capturing CO2 by forming hydrate is an attractive technology for reducing the greenhouse effect. The most primary challenges are high energy consumption, low hydrate formation rate, and separation efficiency. This work presents efficient capture of CO2 from simulated flue gas (CO2 (16.60 mol %)/N2 binary mixtures) by formation of semiclathrate hydrates at 4.5 and 7.1 °C and feed pressures ranging from 2.19 to 7.31 MPa. The effect of 0.293 mol % tetra-n-butyl ammonium bromide (TBAB) and tetra-n-butyl ammonium fluoride (TBAF) on the hydrate formation rate, reactor space velocity, and CO2 separation efficiency was studied in a 1 L stirred reactor. The results showed the hydrate formation rate constant increased with increasing feed pressure and reached the maximum at 2.82 × 10−7 mol2/(s·J) with TBAB and 8.26 × 10−7 mol2/(s·J) with TBAF. The space velocity of the hydrate reactor increased with increasing feed pressure and reached a maximum of 13.46 h−1 with TBAB and 25.96 h−1 with TBAF. CO2 recovery was about...
TL;DR: In this article, a set of oxygen carrier materials synthesized from manganese oxides mixed with iron, nickel, and silicon oxides are evaluated in terms of their ability to release oxygen and to be regenerated with oxygen and demonstrated methane conversion in a quartz fluidized bed batch reactor at 810, 850 and 900 °C.
Abstract: Chemical-looping with oxygen uncoupling (CLOU) is a developing technology, which allows for inherent separation of carbon dioxide during combustion of gaseous and solid fuels. In contrast to the related chemical-looping combustion technology (CLC), where gaseous or gasified fuels react directly with oxygen carrier materials, CLOU utilizes oxygen carriers capable of releasing gaseous oxygen, provided appropriate thermal conditions exist in the fuel reactor, whereupon fuel reacts with the released oxygen. The oxygen carriers are thereafter regenerated by oxidation in the air reactor. In this work, a set of oxygen carrier materials synthesized from manganese oxides mixed with iron, nickel, and silicon oxides are evaluated in terms of their ability to release oxygen and to be regenerated with oxygen and in terms of demonstrated methane conversion in a quartz fluidized bed batch reactor at 810, 850, and 900 °C. The results demonstrate that two Mn/Fe oxygen carriers and one Mn/Ni oxygen carrier have both oxygen release characteristics and high reactivities with methane.The Mn/Fe oxygen carrier synthesized at 1100 °Cwas additionally shown to have an increasing methane conversion on a long-term basis, which opens for a possibility to use Mn/Fe oxygen carriers in time-extended large-scale chemical-looping operations.
TL;DR: An effective method for producing high density fuel candidates from pinenes is provided in this article, where the authors use MMT-K10 as an efficient catalyst for the reaction, although significant amounts of p-cymene and camphene produced as byproducts limit the overall yield to about 80%.
Abstract: An effective method for producing high density fuel candidates from pinenes is provided. MMT-K10 is an efficient catalyst for the reaction, although significant amounts of p-cymene and camphene produced as byproducts limit the overall yield to about 80%. Nafion is also an excellent catalyst for pinene dimerization and was capable of producing dimers in up to 90% yield. Pinene dimers synthesized with these heterogenous catalysts have a density and net heat of combustion comparable to JP-10. It is emphasized that this abstract is provided to comply with the rules requiring an abstract that will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope of the claims.
TL;DR: In this article, an iron oxide-based particle can maintain good reactivity for more than 100 reduction−oxidation (redox) cycles in a thermogravimetric analyzer.
Abstract: The syngas chemical looping (SCL) process coproduces hydrogen and electricity. The process involves reducing metal oxides with syngas followed by regeneration of reduced metal oxides with steam and air in a cyclic manner. Iron oxide is determined to be a desired oxygen carrier for hydrogen production considering overall properties including oxygen carrying capacity, thermodynamic properties, reaction kinetics, physical strength, melting points, and environmental effects. An iron oxide based particle can maintain good reactivity for more than 100 reduction−oxidation (redox) cycles in a thermogravimetric analyzer (TGA). The particle exhibits a good crushing strength (>20 MPa) and low attrition rate. Fixed bed experiments are carried out which reaffirm its reactivity. More than 99.75% of syngas is converted during the reduction stage. During the regeneration stage, hydrogen with an average purity of 99.8% is produced.
TL;DR: In this paper, a wide range of refractory dopants (Si, Ti, Cr, Co, Zr, and Ce) were used to synthesize calcium-oxide-based refractor for carbon dioxide capture.
Abstract: The present study deals with the design and development of novel calcium-oxide-based refractory sorbents synthesized by flame spray pyrolysis (FSP) for carbon dioxide capture. The FSP-derived sorbents inherently exhibit very large CO2 uptake capacity in the present investigation. Sorbents derived from conventional wet chemistry, possessing identical composition, were synthesized and evaluated. A wide range of refractory dopants (Si, Ti, Cr, Co, Zr, and Ce) were employed, aiming at developing sorbents with good mechanical strength. Among all of the doped CaO sorbents, Zr-doped CaO was found to exhibit the best CO2-capture performance under identical conditions of operation. To study the effect of Zr in depth and find out the optimal concentration of Zr needed in the CaO matrix, a series of Zr-incorporated CaO sorbents were synthesized by varying the relative composition of Zr in the CaO base matrix. The present studies suggest that Zr/Ca in the 3:10 atomic ratio results in the formation of the most robust ...
TL;DR: Field pennycress (Thlaspi arvense L.) oil is evaluated for the first time as a feedstock for biodiesel production in this paper, achieving 82 wt % yield by a standard transesterification procedure.
Abstract: Field pennycress (Thlaspi arvense L.) oil is evaluated for the first time as a feedstock for biodiesel production. Biodiesel was obtained in 82 wt % yield by a standard transesterification procedur...
TL;DR: An overview of the work performed at the Energy research Centre of The Netherlands (ECN) on tar measurement, tar prevention, tar cracking, and tar removal can be found in this paper.
Abstract: Biomass gasification at temperatures below 1300 °C yields producer gas with a range of heavy hydrocarbons. These compounds, collectively known as tar, cause fouling and emission problems in equipment using the producer gas. This paper gives an overview of the work performed at the Energy research Centre of The Netherlands (ECN) on tar measurement, tar prevention, tar cracking, and tar removal. Much of the work has been performed in cooperation with partner institutes and industry. Measurement techniques discussed are the tar guideline, solid-phase adsorption (SPA) method, and tar dew point analyzer. On the subject of tar prevention, the effects of operating conditions, fuel composition, and bed materials in fluidized-bed gasifiers are covered. Tar cracking results are presented for catalytic materials, high-temperature treatment, and the use of plasma. ECN research on tar removal involves among others the development of the water-based GASREIP system and the oil-based OLGA technique.
TL;DR: In this paper, Boek et al. studied the nanoaggregation of one resin and two asphaltene structures, generated by an updated quantitative molecular representation (QMR) technique, in toluene and heptane.
Abstract: Molecular dynamics simulation techniques have been used to study the nanoaggregation of one resin and two asphaltene structures, generated by an updated quantitative molecular representation (QMR) technique (Boek, E. S., Yakovlev, D. S., and Headen, T. F. Energy Fuels, manuscript submitted), in toluene and heptane. Analysis of the simulation trajectories, to yield the separation of asphaltene or resin pairs, over a 20 ns simulation has been used to investigate aggregation dynamics. The structure of aggregates has been investigated by the calculation of the asphaltene−asphaltene and resin−resin radial distribution functions, g(r), and the average angle between the polyaromatic planes as a function of separation. We calculate, for the first time, the asphaltene−asphaltene potential of mean force (PMF) from the g(r) and separately by a constraint force method. In general, it is observed that the asphaltenes form dimers and trimers in both toluene and heptane. Once formed, the dimers and trimers can separate ...
TL;DR: In this article, the influence of pyrolysis pressure on product yield from wheat straw pyrotechnics was examined in a tubular reactor at different pressures with a constant flow rate of nitrogen (50 cc/min) at a temperature of 500 °C.
Abstract: The main objective of this work was to examine the influence of pyrolysis pressure on product yield from wheat straw pyrolysis. The experiments were performed in a tubular reactor at different pressures (10, 20, 30, and 40 psi) with a constant flow rate of nitrogen (50 cc/min) at a temperature of 500 °C. During pyrolysis, the products obtained are oil, gas, and char. The maximum oil yield was 37.6%, obtained at high pressure (40 psi). Liquid product was analyzed using gas chromatography/mass spectrometry (GC−MS). The percentage of bio-oil compounds increased as operating pressure increased. The major components present in the bio-oil were phenols, methoxyphenols, and substituted methoxyphenols such as eugenol and vanillin. The gas products were mainly CO, H2, CO2, CH4, C2H4, C2H6, C4H10, and C3’s. Char characteristics were measured using scanning electron microscopy (SEM) and ultimate analysis. Van Krevelen diagram shows that the chars obtained from wheat straw pyrolysis have very less H: C and O: C ratio...
TL;DR: The spatially explicit multi-echelon mixed integer linear program (MILP) modeling framework described in part 1(1) of this work has been extended by including environmental issues along with the traditional economic ones within a more comprehensive multi-objective optimization tool.
Abstract: In developing an optimization framework to assist in the design process of biofuel systems, the economic effectiveness of the supply network should not be adopted as the sole criterion to focus on. In fact, there has recently been growing attention in including environmental concerns at the strategic level of supply chain management. In this part 2, the spatially explicit multi-echelon mixed integer linear program (MILP) modeling framework described in part 1(1) of this work has been extended by including environmental issues along with the traditional economic ones within a more comprehensive multi-objective optimization tool. The economics have been assessed by means of supply chain analysis techniques, focusing on biomass cultivation site locations, ethanol production capacity assignment and facilities location, as well as transport system optimization. The environmental performance of the system has been evaluated in terms of greenhouse gas (GHG) emissions, by adopting a well-to-tank (WTT) approach to...
TL;DR: The regenerable solid amine sorbents investigated in this article exhibit acceptable CO2-capture performance for both dry and humidified CO2 gas streams in simulated flue gas streams.
Abstract: Solid amine sorbents were prepared using mixtures of linear and branched primary, secondary, and tertiary amines These amines were immobilized within polystyrene (PS)-, silicon dioxide (SiO2)-, or polymethylmethacrylate (PMMA)-based substrates at various weight ratios Testing was conducted in various reactor systems, where the reactive water required for the capture of carbon dioxide (CO2) was tracked during the adsorption/desorption cycles by mass spectrometer gas analysis The water management for these sorbents was quantified and used to assess the technical feasibility of the operating conditions for the capture of CO2 from simulated flue gas streams In addition, the heats of reaction and performance capture loading capacities of these sorbents were also determined by differential scanning calorimetry (DSC) and thermogravimetric analyses (TGAs), respectively, in both dry and humidified CO2 gas streams The regenerable solid amine sorbents investigated in this study exhibit acceptable CO2-capture lo
TL;DR: A screening of Fe and Mn-based ores and industrial products was made in order to identify suitable low-cost materials that could be used as oxygen carriers in chemical-looping combustion (CLC) as mentioned in this paper.
Abstract: A screening of Fe- and Mn-based ores and industrial products was made in order to identify suitable low-cost materials that could be used as oxygen carriers in chemical-looping combustion (CLC). A laboratory fluidized bed reactor system, simulating chemical-looping combustion by exposing the sample to alternating reducing and oxidizing conditions, was used. Fifteen grams of each material with a particle size of 125−180 μm was exposed to a flow of 450 mLn/min of either methane or syngas (50% CO, 50% H2) during reduction. During the oxidizing phase to a flow of 1000 mLn/min, 5% O2 in nitrogen was used. All materials had a high reactivity with syngas. Some materials such as the Mn-based Colormax and the Fe-based Glodskal had also a high reactivity with methane making them possible candidates for CLC with gaseous fuel. Some of the materials, especially the Mn-based ones, showed poor mechanical stability and poor fluidizing properties. Roughly half of the Fe-based materials, but only one of the Mn-based materi...
TL;DR: In this paper, the authors examined the ash characteristics of some agricultural crops and residues and found mixtures of fuels and additives that can form the basis for production of fuel pellets with minimal problems.
Abstract: In the process of creating sustainable heat and power production systems it is important to find alternative, renewable fuels that are carbon dioxide neutral. Preferably these fuels should be domestic, thus diminishing the need for transportation. One option could be to use existing residues from local agriculture and food production. Development of combustion methods suitable for such residues is presently being pursued by a number of companies. Because many biomass fuels have compositions that makes them inclined to cause ash sintering problems and emissions of acid gases, there may be a need for the use of additives to decrease such problems. The aim of this work was to examine the ash characteristics of some agricultural crops and residues and to find mixtures of fuels and additives that can form the basis for production of fuel pellets with minimal problems. The work is focused on biomass fuel pellets for small-scale grate-fired combustors. Three additives (limestone powder, kaolin, and sodium bicarb...