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1.
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2.
  • Holst, LE, et al. (författare)
  • Investigation of peat pyrolysis under inert gas atmosphere
  • 1991
  • Ingår i: Fuel. - : Elsevier BV. - 1873-7153 .- 0016-2361. ; 70:9, s. 1017-1022
  • Tidskriftsartikel (refereegranskat)abstract
    • Seven Swedish peats of different degrees of humification were pyrolysed in a thermobalance at pressures in the range 1.0-4.0 MPa. The formation kinetics of the pyrolysis products were determined using the non-isothermal evaluation method. The sample size used was 1.0 g and the heating rate was 10 K min-1. Gas production was analysed by gas chromatography and the components were CO2, C2H4, C2H6, CH4 and CO. The tar and char production were measured after the experiment by weighing. The experiments showed that gas production was slightly increased, at the expense of tar production, with increasing pressure, indicating some thermal cracking. The kinetic parameters, i.e. pre-exponential factor, k0, and activation energy, E(a), were unaffected by the pressure.
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3.
  • Wang, Wuyin, et al. (författare)
  • The kinetics of the reaction of hydrogen chloride with fresh and spent Ca-based desulfurization sorbents
  • 1996
  • Ingår i: Fuel. - : Elsevier BV. - 1873-7153 .- 0016-2361. ; 75:2, s. 207-212
  • Tidskriftsartikel (refereegranskat)abstract
    • The absorption of hydrogen chloride by spent desulfurization sorbents containing calcium carbonate, calcium oxide and calcium hydroxide was investigated. The experiments were carried out in a fixed-bed reactor in two temperature ranges: 423-523 K for slaked lime and 673-873 K for limestone and quicklime. The spent Ca-based sorbents can still react with hydrogen chloride, and after calcining and slaking they even show the same reactivity as pure Ca(OH)(2). A model combining both fixed-bed reactor and shrinking-core model was derived. The activation energy of the surface reaction between hydrogen chloride and limestone was determined to be 84 kJ mol(-1) at 673-873 K. The pore diffusion activation energy was 11 kJ mol(-1) for limestone at 673-873 K, 29 kJ mol(-1) for CaO at 673-873 K and 12 kJ mol(-1) for slaked lime at 423-523 K.
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4.
  • Bellais, Michel, et al. (författare)
  • Pyrolysis of large wood particles : a study of shrinkage importance in simulations
  • 2003
  • Ingår i: Fuel. - 0016-2361 .- 1873-7153. ; 82:12, s. 1541-1548
  • Tidskriftsartikel (refereegranskat)abstract
    • Shrinkage models have been developed and included in a model for the pyrolysis of large wood particles. Shrinkage is modelled in three different ways: uniform shrinkage, shrinking shell and shrinking cylinders. These models and a reference model without shrinkage are compared with experimental data for mass loss versus time during pyrolysis of birch cylinders at different temperatures. In the experiments a wood particle was introduced into a pyrolysis furnace held at constant temperature. The particle mass and volume were recorded using a balance and a video camera. Uniform shrinkage slows down the pyrolysis whereas shrinking shell and cylinder models enhance the pyrolysis rate. The effect was sufficiently small to be neglected given the uncertainty about some wood physical properties.
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5.
  • Nordin, Anders, et al. (författare)
  • NO reduction in a fluidized bed combustor with primary measures and selective non-catalytic reduction a screening study using statistical experimental designs
  • 1995
  • Ingår i: Fuel. - 0016-2361 .- 1873-7153. ; 74:1, s. 128-135
  • Tidskriftsartikel (refereegranskat)abstract
    • Screening experiments were carried out to study the reduction of NO emissions from a 20 MW circulating fluidized bed (CFB) boiler, equipped with an installation for selective non-catalytic reduction (SNR). The influence of both primary measures and SNR were evaluated, using 25-1 and 25-2 fractional factorial designs for the two fuels, crushed peat and wood waste, respectively. Polynomial models were deducted from statistical analysis of the experiments, and a good agreement between models and measured data was obtained. The evaluation showed that, by using a designed experimental procedure, CFB operating conditions yielding an NO reduction of 60-80% could be identified, with both primary measures and the SNR being of approximately equal importance. Most important factors for the NO reduction were air:fuel ratio, the amount of NH3 added, the load and the fraction of lower secondary air; but the reduction is also influenced by small interaction effects. A discussion of the use of experimental designs for increased understanding and optimization of combustion processes is also given.
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6.
  • Paulrud, S., et al. (författare)
  • Reed canary-grass ash composition and its melting behaviour during combustion
  • 2001
  • Ingår i: Fuel. - 0016-2361 .- 1873-7153. ; 80:10, s. 1391-1398
  • Tidskriftsartikel (refereegranskat)abstract
    • Spring harvested reed canary-grass (RCG) with various chemical compositions was combusted in a 180 kW boiler. The ash melting behaviour was studied and the ash was analysed. Estimation of melting behaviour was done by ASTM fusion test, a bench-scale fluidized-bed combustion test (5 kW), and by extracting melting behaviours from the ternary phase diagram SiO2-CaO-K2O. The initial melting temperatures seem to be similar for the different samples; however, for low ash content (3-4% DM) higher portions of melt occurred in the lower temperature range <1200°C and for high ash content fuels (5-10%) more melting occurred in a higher temperature range, >1500°C. © 2001 Elsevier Science Ltd. All rights reserved.
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7.
  • Sayan, S., et al. (författare)
  • Methyldecalin hydrocracking over palladium/zeolite-X
  • 2000
  • Ingår i: Fuel. - 0016-2361 .- 1873-7153. ; 79:11, s. 1395-1404
  • Tidskriftsartikel (refereegranskat)abstract
    • Hydrocracking of methyldecalin over Pd/REX has been studied with surface sensitive techniques in the critical temperature range 325-350°C. Results from in situ characterization of adsorbed species, and post-reaction analysis of the catalyst surface by infrared and photoemission spectroscopies, were related to product distributions. The results are discussed in light of quantum chemical calculations of free and catalyst bound intermediates, following ring-opening reactions. Liquid and gaseous products were detected by infrared and UV/Vis spectroscopies. Apparent activation energies of product formation hydrogen consumption, over a broader temperature range, were derived from previous autoclave experiments. An increase in temperature, 325-350°C, results in a shift from preferred cracking products to aromatics, an enhanced level of light hydrocarbon off-gases, and a higher coverage of carbonaceous residues. The increased level of carbonaceous residues is accompanied by a lowered coverage of the reactant, at the surface. The altered product distribution can be characterized by apparent single activation energies, valid from 300 to 450°C. Methane and aromatics show a similar rapid increase with temperature, hydrogen consumption a more timid increase, indicating a reaction limited by diffusion, and cycloalkane production a modest inverse temperature dependence. Fully hydrogenated ring-opening products represent valuable fuel components, but hydrogen deficiency can instead lead to chemisorbed precursors to coke. Our calculations show that cyclohexane, 1,2-diethyl, 3-methyl has a lower heat of formation than the corresponding surface intermediates, but a small enthalpy advantage can easily be countered by entropy effects at higher temperatures. This balance is critical to the formation of preferred products, instead of catalyst deactivation and aromatics. The theoretical results further show that surface intermediates, where the terminating hydrogen is replaced by a C-O bond, have distinct vibrations around 1150 cm-1.
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8.
  • Seferinoğlu, Meryem, et al. (författare)
  • Acid leaching of coal and coal-ashes
  • 2003
  • Ingår i: Fuel. - 0016-2361 .- 1873-7153. ; 82:4, s. 1721-1734
  • Tidskriftsartikel (refereegranskat)abstract
    • Twelve Turkish lignites and the corresponding ashes were leached in sulfuric acid (pH 1.0, 25 oC) for 14 days. Asphaltite from Silopi amended the coals. The conditions mimic treatment in the effluent from bioleaching of sulfidic mineral concentrates, but the results are equally valid for an isolated leaching process. The extended time meant that we approached equilibrium and maximum extraction.The coals have limited neutralizing capacity. H2SO4 (1.0-2.0 l, 1 M) was needed to stabilize 1 kg coal at pH 1.0 (liquid:solid ratio 10:1), but the coal-ashes required 18.0-24.0 l/kg dry solid, which is the neutralizing equivalent to CaO.Leaching of dominant inorganic phases consume acid, but our interest is merely to remove trace elements present as dopants. We removed large fractions of Mg and Mn, but Al, K and Na extractions were limited by the presence of stable minerals and bimetallic oxides. The formation of the latter is driven by combustion at high temperatures. Alumina, normally not stable at pH 1.0, was protected from the effluent by the organic phase in coal. Fe leaching varied and appeared to be a marker for different chemical occurrences in the solids.Cd, V, Zn, U and Th were leached to near 80% from the ashes, but considerably less from the coals. Co and Ni extractions were near 60%, but not always higher from the ashes compared with the coals. Cu yields increase following ashing and reached ca. 60%. Ti, Ba, and Cs were not leached.We suggest that direct acid leaching is of interest to limit the deleterious impact of ash deposits and to recirculate metals from the ash. Ash may partly replace limestone in hydrometallurgical processing, but, more importantly, metal ions extracted from ash may be fed into the metal recovery stages of such processes. It is particularly interesting to leach Co, Cu, Ni and Zn, besides Mn, V and the environmentally hazardous Cd, U and Th. Leaching of whole coals is well motivated for domestic use-lump sizes around 18-50 mm, or slightly smaller, 10 mm, if mandated by practical residence times-where generally no other measures are taken to protect the local environment.
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9.
  • Vriesman, Peter, et al. (författare)
  • Biomass gasification in a laboratory-scale AFBG : influence of the location of the feeding point on the fuel-N conversion
  • 2000
  • Ingår i: Fuel. - 0016-2361 .- 1873-7153. ; 79:11, s. 1371-1378
  • Tidskriftsartikel (refereegranskat)abstract
    • The influence of the feeding point on the conversion of fuel-nitrogen (fuel-N) was studied in an atmospheric fluidized bed gasifier. A comparison between feeding into the bed and feeding from the top of the reactor was made for different temperatures and equivalence ratios. Special emphasis was given to the distribution of fuel-N into NH3, HCN and char. The results show no influence of the feeding point on the nitrogen conversion to HCN and on the amount of nitrogen in char. Top feeding, however, results in lower conversion of fuel-N to NH3. The feeding points, and therefore the contact between the fuel particles and the surrounding oxygen-containing gas, as well as the oxygen concentration itself, are of great importance for the formation and destruction of NH3.
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10.
  • Zevenhoven-Onderwater, Maria, et al. (författare)
  • The ash chemistry in fluidised bed gasification of biomass fuels. Part I : Predicting the chemistry of melting ashes and ash-bed material interaction
  • 2001
  • Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 80:10, s. 1489-1502
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper is part I in a series of two describing the modelling of the ash-chemistry of seven biomass fuels under reducing, pressurised conditions in fluidised bed gasification by means of thermodynamic multi-phase multi-component equilibrium (TPCE) calculations. The fuels considered were Salix, a Scandinavian forest residue, Miscanthus, Reed Canary Grass, Eucalyptus, Arundo Donax and Lucerne. The composition and amount of phases have been calculated for the gasification of the fuel as such and in presence of an excess amount of calcite, dolomite, magnesium olivine sand and sand by using TPCE calculations in a temperature interval of 600-900°C and a pressure of 10 bar. It was found that interaction of inorganic compounds released from the fuels with bed material is a prerequisite for the formation of bed agglomerates. The presence of an excess of dolomite decreased the amount of alkali components in the bed, thereby increasing the amount of alkali components volatilised. A silica bed, however, binds most alkali released from the fuel, retaining it in the bed as low melting alkali silicates. The chances of experiencing operating problems due to bed agglomeration may increase hereby significantly. Calculations at atmospheric pressure show that the amounts of melt present will be smaller when compared to pressurised conditions, thereby decreasing the chances of bed agglomeration. In a pressurised gasifier using calcite or dolomite as bed material a small amount of an alkali carbonate rich melt can be expected at temperatures above 620°C with each of the seven biomass fuels fired. In silica-rich cases such as when firing Miscanthus, Reed Canary Grass, Arundo Donax or using a Si-rich bed material a melt can be expected at temperatures above 770°C. The amount of melt is rather high, i.e. 12-100% of the original ash formed. In the case of a magnesium olivine sand bed an alkali melt can be expected at 620°C. At temperatures above 800°C, a silicate melt can form as well. The amount of melt was hi gh, i.e. 60-300% of the original ash formed, showing a significant contribution of the bed material.
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11.
  • Ahmadi, Mozhgan, et al. (författare)
  • Development of a PID based on-line tar measurement method : Proof of concept
  • 2013
  • Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 113, s. 113-121
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, a proof of concept was conducted for an on-line tar analyzer based on photo ionization detection (PID). Tar model compounds (naphthalene, acenaphthene, acenaphthylene, fluorene, indane and indene) were used for the initial investigation of the analysis method. It was found that the analysis method has a high sensitivity and a linear behavior was observed between the PID response and the tar concentration over a wide concentration span. The on-line tar analysis method was successfully validated against the solid phase adsorption (SPA) method using a real producer gas.
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12.
  • Ahmed, Trifa Mohammad, et al. (författare)
  • Emissions of particulate associated oxygenated and native polycyclic aromatic hydrocarbons from vehicles powered by ethanol/gasoline fuel blends
  • 2018
  • Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 214, s. 381-385
  • Tidskriftsartikel (refereegranskat)abstract
    • Emission factors for oxygenated polycyclic aromatic hydrocarbons (OPAHs) and PAHs have been determined from two different fuel flexible light duty vehicles operated at -7 degrees C in the New European Driving Cycle (NEDC) and at +22 degrees C in the Artemis Driving Cycle (ADC). Three different gasoline/ethanol blends, commercially available in Sweden, were tested i.e., gasoline E5, with 5% v/v ethanol and ethanol fuel E85 with 85% v/v ethanol and winter time quality E70 with 70% v/v ethanol, respectively. The results showed greatly increased emissions of both OPAHs and PAHs at cold engine start conditions (-7 degrees C in the NEDC) compared to warm engine start (+ 22 degrees C in the ADC). For the OPAHs, higher average total emission factors were obtained when running on E85 compared to E5 at both cold 2.72 mu g/km vs 1.11 mu g/km and warm 0.19 mu g/km vs 0.11 mu g/km starting conditions with the highest emissions when using E70 at -7 degrees C 4.12 mu g/km. The same trend was found for the PAHs at cold engine start with higher average total emission factors when using ethanol fuel 71.5 mu g/km and 60.0 mu g/km for E70 and E85, respectively compared to gasoline E5 (20.2 mu g/km). Slightly higher average total PAH emissions were obtained when operating at + 22 degrees C with E5 compared to with E85 1.23 mu g/km vs 0.72 mu g/km.
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13.
  • Alemahdi, Nika, et al. (författare)
  • The effect of 2-ethyl-hexyl nitrate on HCCI combustion properties to compensate ethanol addition to gasoline
  • 2020
  • Ingår i: Fuel. - : Elsevier BV. - 1873-7153 .- 0016-2361. ; 270
  • Tidskriftsartikel (refereegranskat)abstract
    • Stable HCCI combustion requires a proper level of fuel reactivity. This study shows that adding ethanol as a renewable fraction to low octane gasoline decreases the reactivity of the gasoline, while adding 2-ethyl hexyl nitrate (2-EHN) can enhance the reactivity of the blend and counter the effect of ethanol.The experimental apparatus consisted of a modified CFR engine for HCCI combustion equipped with two port fuel injectors and an intake air heater. Gasoline blended with ethanol (10% v/v) was used as the base fuel. Different percentages of 2-EHN (0.25%, 0.50%, 1%, and 2.5%) were added to the base fuel as an ignition improver. The blends were tested at operating points defined for HCCI number at two different engine speeds (600 and 900 rpm) and three different intake temperatures (50, 100, and 150 °C) to investigate the effect of 2-EHN on the auto-ignition behavior of the fuel.Combustion, emissions, and performance parameters of HCCI combustion of the blends were measured. The presence of 2-EHN in the blends improved the auto-ignitability of the blends in a nonlinear manner. It was also found that 0.25% of 2-EHN can compensate for the effect of ethanol on the required compression ratio and remove the quenching effect of ethanol on low temperature heat release. The results show that for the same fuel, a higher compression ratio is needed to maintain the combustion phasing constant at a higher engine speed.
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14.
  • Andersson, Jim, et al. (författare)
  • Co-gasification of pyrolysis oil and black liquor for methanol production
  • 2015
  • Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 158, s. 451-459
  • Tidskriftsartikel (refereegranskat)abstract
    • One alternative to reduce the motor fuel production cost and improve the operational flexibility of a black liquor gasification (BLG) plant is to add pyrolysis oil to the black liquor feed and co-gasify the blend. The objective of this study was to investigate techno-economically the possibility to increase methanol production at a pulp mill via co-gasification of pyrolysis oil and black liquor. Gasifying a blend consisting of 50% pyrolysis oil and 50% black liquor on a wet mass basis increases the methanol production by more than 250%, compared to gasifying the available black liquor only. Co-gasification would add extra revenues per produced unit of methanol (IRR > 15%) compared to methanol from unblended BLG (IRR 13%) and be an attractive investment opportunity when the price for pyrolysis oil is less than 70 €/MW h. The economic evaluation was based on a first plant estimate with no investment credit for the recovery boiler and a methanol product value volumetric equivalent to conventional ethanol, both these conditions will not applicable when the technology has been fully commercialized.
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15.
  • Andersson, Robert, et al. (författare)
  • Effect of CO2 in the synthesis of mixed alcohols from syngas over a K/Ni/MoS2 catalyst
  • 2013
  • Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 107, s. 715-723
  • Tidskriftsartikel (refereegranskat)abstract
    • An unsupported K-Ni-MoS2 catalyst for higher alcohol synthesis from syngas (H-2/CO) has been studied during 360 h on stream. It shows a gradual increase in activity with time on stream and some possible reasons for this are discussed in the paper. The main focus of this paper was to study the on the effect of CO2-containing syngas, relative CO2-free syngas under identical reaction conditions and identical inlet H-2 and CO partial pressures (340 degrees C, 100 bar, GHSV = 6920 ml/(g(cat) h)). The effect of increased partial pressure of H-2 and CO was also studied, and to a minor extent also the effect of changed gas hourly space velocity (GHSV). Under the studied conditions, addition of CO2 was found to greatly decrease total product yield, while the selectivities to alcohol and hydrocarbons (C%, CO2-free), respectively, were unchanged. CO2 addition, however, led to a great change in the distribution within the alcohol and hydrocarbon groups. With CO2 added the methanol selectivity increased much while selectivity to longer alcohols decreased. For hydrocarbons the effect is the same, the selectivity to methane is increased while the selectivity to longer hydrocarbons is decreased. It has earlier been shown that product selectivities are greatly affected by syngas conversion level (correlated to outlet concentration of organic products, i.e. alcohols, hydrocarbons etc.) which can be altered by changes in space velocity or temperature. This means that alcohol selectivity is decreased in favor of increased hydrocarbon selectivity and longer alcohol-to-methanol ratio when syngas conversion is increased. At first it might be thought that the selectivity changes occurring when CO2 is present in the feed, just correlate to a decreased organic product concentration in the reactor and that the selectivities with CO2-containing and CO2-free syngas would be identical under constant concentration of organic products in the reactor. However, CO2-addition studies where space velocity was varied showed that significantly lower alcohol selectivity (mainly ethanol selectivity) and increased hydrocarbon selectivity (mainly methane) were found at similar organic outlet concentrations as when CO2-free syngas was feed. Comparing addition of extra H-2 or extra CO, it was found that a high H-2/CO ratio (H-2/CO = 1.52 tested in our case) favors maximum product yield, especially methanol formation, while a lower H-2/CO ratio (H-2/CO = 0.66 tested in our case) leads to higher yield of higher alcohols simultaneously minimizing hydrocarbon and methanol formation.
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16.
  • Andersson, Robert, et al. (författare)
  • Higher alcohols from syngas using a K/Ni/MoS2 catalyst : Trace sulfur in the product and effect of H2S-containing feed
  • 2014
  • Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 115, s. 544-550
  • Tidskriftsartikel (refereegranskat)abstract
    • Two types of experiments have been performed related to the higher alcohol synthesis from syngas over a K-Ni-MoS2 catalyst which beforehand has been operated for 1000 h on stream in sulfur-free syngas. In the first experimental part, sulfur-free syngas was used as feed and the condensed liquid product was found to contain 67 ppmw sulfur, while the sulfur concentration in the gas was 19 ppmv. The gas phase was found to contain mainly COS and H2S, while the liquid phase contained methanethiol (13.8 ppmw S), ethanethiol (10.6 ppmw S), dimethyl sulfide (21.3 ppmw S), ethyl methyl sulfide (12.2 ppmw S), unidentified sulfur compounds (7.9 ppmw S) together with some dissolved COS (0.5 ppmw S) and H2S (1.2 ppmw S). In the second experimental part, the effect of feeding syngas containing 170 ppm H2S compared to a sulfur-free syngas was studied, while all products were carefully monitored online. The presence of H2S in the syngas was found to increase CO conversion, but the largest change was found in product selectivity. The hydrocarbon selectivity greatly increased at the expense of alcohol selectivity, while the alcohol distribution shifted towards longer alcohols (increased C2+OH/MeOH ratio). From product yields it became clear that most of the increased CO conversion with H2S in the feed was due to increased methane formation (and CO2 formation due to the water-gas shift reaction). The presence of H2S in the feed greatly increased the concentration of all sulfur compounds. Together with COS, formation of thiols (methanethiol and ethanethiol) was especially favored by the presence of H2S. The thioether concentration also increased, however, to a much lower extent.
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17.
  • Andersson, Viktor, 1983, et al. (författare)
  • Alkali desorption from ilmenite oxygen carrier particles used in biomass combustion
  • 2024
  • Ingår i: Fuel. - 0016-2361 .- 1873-7153. ; 359
  • Tidskriftsartikel (refereegranskat)abstract
    • Oxygen-carrying fluidized bed materials are increasingly used in novel technologies for carbon capture and storage, and to improve the efficiency of fuel conversion processes. Potassium- and sodium-containing compounds are released during biomass combustion and may have both negative and positive effects on conversion processes. Ilmenite is an important oxygen carrier material with the ability to capture alkali in the form of titanates. This is a desirable property since it may reduce detrimental alkali effects including fouling, corrosion, and fluidized bed agglomeration. This study investigates the interactions of alkali-containing compounds with ilmenite particles previously used in an industrial scale (115 MWth) oxygen carrier aided combustion system. The ilmenite samples were exposed to temperatures up to 1000 °C under inert and oxidizing conditions while the alkali release kinetics were characterized using online alkali monitoring. Alkali desorption occurs between 630 and 800 °C, which is attributed to loosely bound alkali at or near the surface of the particles. Extensive alkali release is observed above 900 °C and proceeds during extended time periods at 1000 °C. The release above 900 °C is more pronounced under oxidizing conditions and approximately 9.1 and 3.2 wt% of the alkali content is emitted from the ilmenite samples in high and low oxygen activity, respectively. Detailed material analyses using scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were conducted before and after temperature treatment, which revealed that the concentrations of potassium, sodium and chlorine decrease at the outermost surface of the ilmenite particles during temperature treatment, and Cl is depleted to a deeper level in oxidizing conditions compared to inert. The implications for ilmenite-ash interactions, oxygen carrier aided combustion and chemical looping systems are discussed.
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18.
  • Andrae, Johan C. G. (författare)
  • Development of a detailed kinetic model for gasoline surrogate fuels
  • 2008
  • Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 87:10-11, s. 2013-2022
  • Tidskriftsartikel (refereegranskat)abstract
    • A detailed chemical kinetic model to describe the autoignition of gasoline surrogate fuels is presented consisting of the fuels isooctane, n-heptane, toluene, diisobutylene and ethanol. Model predictions have been compared with shock tube ignition delay time data for surrogates of gasoline over practical ranges of temperature and pressure, and the model has been found to be sensitive to both changes in temperature and pressure. Moreover, the model can qualitatively predict the observed synergistic and antagonistic non-linear blending behaviour in motor octane number (MON) for different combinations of primary reference fuels (PRFs) and non-PRFs by correlating calculated autoignition delay times from peak pressures and temperatures in the MON test to experimental MON values. The reasons for the blending behaviour are interpreted in terms autoignition chemistry.
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19.
  • Anerud, Erik, et al. (författare)
  • Fuel quality of stored spruce bark - Influence of semi-permeable covering material
  • 2020
  • Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 279
  • Tidskriftsartikel (refereegranskat)abstract
    • Bark is a by-product of the sawmilling and pulp industries that is produced year-round. It is mainly used as a fuel, making its storage unavoidable due to seasonal variation in energy demand. Storing bark can lead to high energy losses but can also increase its fuel quality, e.g. by reducing its moisture content (M) and increasing its net calorific value (Q). Covering wood chip stacks with semi-permeable fabric sheets can improve fuel quality and reduce dry matter losses (DML) during storage. The objective of this study was, therefore, to evaluate the effect of similar coverage during storage on the fuel quality and energy recovery of stored bark. Two bark stacks of 1000 and 1400 m(3) were established, with half of each stack being covered with a water-resistant, vapour-permeable fabric. The temperature, M, and Q were measured in each stack immediately after construction and after three and seven months of storage. Additionally, the DML, total accessible energy, and economic value of each stack were calculated at the same time points.The combined changes in fuel quality and DML reduced the amount of accessible energy by 13.7% in the uncovered parts but increased that in the covered parts by 0.6%. The economic value of the covered parts was unchanged after storage whereas that of the uncovered parts was reduced by 14%. Covering bark stacks with semi-permeable fabric during storage could thus increase the profitability of bark fuel supply chains.
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20.
  • Azuara, Manuel, et al. (författare)
  • Influence of pressure and temperature on key physicochemical properties of corn stover-derived biochar
  • 2016
  • Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 186, s. 525-533
  • Tidskriftsartikel (refereegranskat)abstract
    • This study focuses on analyzing the effect of both the peak temperature and pressure on the properties of biochar produced through slow pyrolysis of corn stover, which is a common agricultural waste that currently has little or no value. The pyrolysis experiments were carried out in a fixed-bed reactor at different peak temperatures (400, 525 and 650 degrees C) and absolute pressures (0.1, 0.85 and 1.6 MPa). The inert mass flow rate (at NTP conditions) was adjusted in each test to keep the gas residence time constant within the reactor. The as-received corn stover was pyrolyzed into a biochar without any physical pre-treatment as a way to reduce the operating costs. The properties of biochars showed that high peak temperature led to high fixed-carbon contents, high aromaticity and low molar H:C and O:C ratios; whereas a high pressure only resulted in a further decrease in the O:C ratio and a further increase in the fixed-carbon content. Increasing the operating pressure also resulted in a higher production of pyrolysis gas at the expense of water formation.
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21.
  • Bach Oller, Albert, et al. (författare)
  • Co-gasification of black liquor and pyrolysis oil at high temperature : Part 2. Fuel conversion
  • 2017
  • Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 197, s. 240-247
  • Tidskriftsartikel (refereegranskat)abstract
    • The efficiency and flexibility of the BL gasification process may improve by mixing BL with more energy-rich fuels such as pyrolysis oil (PO). To improve understanding of the fuel conversion process, blends of BL and PO were studied in an atmospheric drop tube furnace. Experiments were performed in varying atmosphere (5% and 0% CO2, balanced by N2), temperature (800–1400 °C), particle size (90–200 μm and 500–630 μm) and blending ratio (0%, 20% and 40% of PO in BL on weight basis). Additionally, pine wood was used as a reference fuel containing little alkali. The addition of PO to BL significantly increased the combined yield of CO and H2 and that of CH4. BL/based fuels showed much lower concentration of tar in syngas than pine wood. Remarkably, the addition of PO in BL further promoted tar reforming in presence of CO2. Unconverted carbon in the gasification residue decreased with increasing fractions of PO. Small fuel particles showed complete conversion at 1000 °C but larger particles did not reach complete conversion even at T = 1400 °C.
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22.
  • Bach Oller, Albert, et al. (författare)
  • Co-gasification of black liquor and pyrolysis oil at high temperature : Part 1. Fate of alkali elements
  • 2017
  • Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 202, s. 46-55
  • Tidskriftsartikel (refereegranskat)abstract
    • The catalytic activity of alkali compounds in black liquor (BL) enables gasification at low temperatures with high carbon conversion and low tar and soot formation. The efficiency and flexibility of the BL gasification process may be improved by mixing BL with fuels with higher energy content such as pyrolysis oil (PO). The fate of alkali elements in blends of BL and PO was investigated, paying special attention to the amount of alkali remaining in the particles after experiments at high temperatures. Experiments were conducted in a drop tube furnace under different environments (5% and 0% vol. CO2 balanced with N2), varying temperature (800–1400 °C), particle size (90–200 µm, 500–630 µm) and blending ratio (0%, 20% and 40% of pyrolysis oil in black liquor). Thermodynamic analysis of the experimental cases was also performed.The thermodynamic results qualitatively agreed with experimental measurements but in absolute values equilibrium under predicted alkali release. Alkali release to the gas phase was more severe under inert conditions than in the presence of CO2, but also in 5% CO2 most of the alkali was found in the gas phase at T = 1200 °C and above. However, the concentration of alkali in the gasification residue remained above 30% wt. and was insensitive to temperature variations and the amount of PO in the blend. Thermodynamic analysis and experimental mass balances indicated that elemental alkali strongly interacted with the reactor’s walls (Al2O3) by forming alkali aluminates. The experience indicated that adding PO into BL does not lead to alkali depletion during high temperature gasification.
  •  
23.
  • Baina, Fabiola, et al. (författare)
  • Extended operability of a commercial air-staged burner using a synthetic mixture of biomass derived gas for application in an externally fired micro gas turbine
  • 2015
  • Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 150, s. 664-671
  • Tidskriftsartikel (refereegranskat)abstract
    • Biomass gasification converts solid biomass into a gaseous fuel that is more versatile and can be used in many applications. However, biomass gasification gas contains some contaminants and inert compounds. The contaminants can cause several problems in the downstream equipment and undesirable emissions while the inert compounds can affect the lower heating value of the gas. Because of these characteristics, there have been difficulties in finding a conversion technology using biomass gasification gas for heat and power generation. In this regard, externally fired gas turbines open a possibility for this combustible gas since due to its configuration, combustion takes place outside the conventional gas turbine cycle. For this reason, combustion studies of biomass derived gas are important. In this work the operability of a commercial air-staged natural gas burner is shown in terms of CO, UHC, and NOX emissions using a synthetic mixture of biomass gasification gas. Two fuel gas mixtures simulating the composition of biomass gasification gas are injected in the combustor. Each fuel gas contains different injection rates of benzene in order to represent tars and to understand their effect on the combustion performance. Additionally, the equivalence ratio is varied in a range of lean conditions in order to find an optimum operation point for the burner studied. The results showed that the presence of polyaromatic hydrocarbons such as benzene reduced the CO concentrations in the exhaust gas while it increased the concentrations of unburned hydrocarbons (UHC) at equivalence ratios lower than 0.68. Additionally, NOX emissions showed a relatively constant trend over the range of equivalence ratios studied for both fuels. It was also observed that NOX emissions increase with the addition of benzene in the fuel gas. An optimum point with regards CO and UHC concentrations was found for the fuels tested.
  •  
24.
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25.
  • Binti Munajat, Nur Farizan, et al. (författare)
  • Correlation of laminar flame speed and lean blowoff limit with the fuel composition of gasified biomass
  • Ingår i: Fuel. - 0016-2361 .- 1873-7153.
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • The composition of the product gas produced from a biomass gasification process varies largely depending on several operational factors. The present study gathers the combustion information of different fuel mixtures that resemble the wide range of product gases from biomass gasification process. Two combustion parameters that are laminar flame speed, SL and lean blowoff limit, ERblowoff have been studied as functions of the content of H2 in the fuel mixture as well as the ratios of CO/H2, hydrocarbons/H2 and diluents/H2. From the plotted graphs, mathematical correlations between the parameter studied and the component of the gas mixture have been derived. The equations developed can be used to calculate the laminar flame speed and blowoff equivalent ratio for a wide range of gasified biomass. The graphs show that the H2 content and diluents/H2 ratio have the greatest influence on the laminar flame speed of the gas mixture and higher effect compared to the influence by the ratio of CO/H2 and hydrocarbons/H2. For the lean blowoff limit, the descending order of influence is the ratio of diluents/H2, H2 content and the ratio of CO/H2. While no importance on the lean blowoff limit is observed for the ratio of hydrocarbons/H2.
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26.
  • Binti Munajat, Nur Farizan, et al. (författare)
  • Influence of water vapour and tar compound on combustion of simulated gasified biomass
  • Ingår i: Fuel. - 0016-2361 .- 1873-7153.
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • Gasification is a thermo‐chemical process which converts biomass fuel into a gaseous mixture, gasified biomass, which can be used in various prime movers. For heat and power generation, using gasified biomass in a combustion device, for example, can give lower undesired emission compared to direct combustion of solid biomass. However, with regards to its variety in composition and lower heating value, the combustion behaviour of gasified biomass may differ from natural gas. The main objective of this study is to investigate the influence of water and tar compound on the combustion of simulated gasified biomass, which mainly contains CO, H2, CH4, CO2, N2. The combustion tests are conducted at atmospheric pressure in a premixed combustor. At a fixed input thermal load, CO and NOx emission levels, combustion temperature, and blowoff characteristics of gasified biomass are observed while varying the volume fraction of water (H2O) or benzene (C6H6) vapours in the fuel mixture. With low H2O level in the fuel mixture, the combustion temperature is almost constant, while NOx emission is decreased compared to dry gasified biomass. On the contrary, the combustion temperature decreases and NOx emission is almost constant at higher H2O content. A temperature limit was observed where CO emission could be maintained at low concentration. The blowoff limit was shifted to higher equivalence ratio. The blowoff temperature was first slightly decreased at lower H2O level and raised when H2O level is further increased. With the content of C6H6, the combustion temperature and NOx emission enhanced, while CO emission was reduced. The blowoff occurs at slightly higher equivalence ratio and temperature compared to gasified biomass without C6H6. The study shows that the presence of H2O and C6H6 in gasified biomass may give positive effects on the emission characteristics during combustion, but also that there are limits for these effects.
  •  
27.
  • Bjurström, Henrik, et al. (författare)
  • Unburned carbon in combustion residues from solid biofuels
  • 2014
  • Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 117:Part A, s. 890-899
  • Tidskriftsartikel (refereegranskat)abstract
    • Unburned carbon (UC) in 21 combustion residues from solid biofuels has been examined using several methods of analysis (including LOI and TOC) as well as micro-Raman spectroscopy. The concentration of unburned carbon in the residues varied over an order of magnitude and in several samples accounted for about 10% of the ash mass. It was observed that TOC had a poor correlation to organic carbon, especially for fly ashes. LOI at all tested temperatures showed a better correlation than TOC to the organic carbon content, whereas the TOC is better correlated to elemental carbon. LOI550 gave a larger variation and a less complete mobilisation of unburned carbon than LOI at 750 or 975 °C did, but at the highest temperature metal oxidation was notably affecting the mass balance to the extent that some samples gained mass. For this reason, and of the temperatures tested, LOI750 seem to be the most stable indicator for organic remains in the incineration residuals. Most of the unburned carbon is elemental, and only slowly degradable, so the potential emissions of organic compounds from ashes should not be assessed by using a TOC test. The structure of the detected elemental carbon in UC is similar to that of activated carbon, which indicates a potentially large specific surface. This should be borne in mind when assessing the environmental impact of using ash for different purposes, including use as a construction material. Field studies are needed to verify the actual impact as it may depend on environmental conditions.
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28.
  • Bozaghian Bäckman, Marjan, et al. (författare)
  • Bed material performance of quartz, natural K-feldspar, and olivine in bubbling fluidized bed combustion of barley straw
  • 2024
  • Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 364
  • Tidskriftsartikel (refereegranskat)abstract
    • The present study investigates how three different silicate-based bed materials behave in bubbling fluidized bed combustion of a model agricultural residue with respect to ash composition, namely barley straw. Quartz, natural K-feldspar, and olivine were all used in combustion at 700 °C, and the resulting layer formation and bed agglomeration characteristics were determined. Based on this, a general reaction model for bed ash from agricultural residues was proposed, taking into account the reactivity of the different silicates investigated towards the main ash-forming elements K, Ca, and Si. The proposed reaction model links bed material interaction with K-rich bed ash to the degree of polymerization of the silicate bed material, where addition reactions occur in systems with high polymerization, predominately in quartz, and substitution reactions dominate for depolymerized silicates such as K-feldspar and olivine.
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29.
  • Cao, Wenhan, et al. (författare)
  • Release of potassium in association with structural evolution during biomass combustion
  • 2021
  • Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 287, s. 1-9
  • Tidskriftsartikel (refereegranskat)abstract
    • A mechanistic understanding of potassium release is essential to mitigate the potassium-induced ash problems during biomass combustion. This work studies the effects of operational condition on the potassium release and transition during the combustion of wheat straw, and elucidate the release potential of potassium associated with the structural change of biomass particles. The combustion tests were carried out in a laboratory-scale reactor, working in a wide range of temperatures and heating rates. It was found that the combustion of biomass sample at a temperature up to 1000 °C results in a release of over 60% of its initial potassium content. Raising the heating rate from 8 °C/min to 25 °C/min could lead to an additional release of up to 20% of the initial amount of potassium. A three-stage potassium release mechanism has been concluded from this work: the initial-step release stage (below 400 °C), the holding stage (400–700 °C) and the second-step release stage (above 700 °C). Comprehensive morphology analysis with elemental (i.e. K, S, O, Si) distribution was carried out; the results further confirmed that potassium is likely to exist inside the stem-like tunnel of biomass particles, mainly in forms of inorganic salts. During the heating-up process, the breakdown and collapse of biomass particle structure could expose the internally located potassium and thus accelerate the release of potassium and the transform of its existing forms. Lastly, a detailed temperature-dependent release mechanism of potassium was proposed, which could be used as the guidance to mitigate the release of detrimental potassium compounds by optimising the combustion process.
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30.
  • Cardozo Rocabado, Evelyn, et al. (författare)
  • Combustion of agricultural residues : An experimental study for small-scale applications
  • 2014
  • Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 115, s. 778-787
  • Tidskriftsartikel (refereegranskat)abstract
    • Energy services could be greatly improved by using of residues from local food industries in small-scale combustion units. Wood pellets are a reliant and proven fuel to be used in small-scale combustion units. However, these units should preferably be able to use different types of biomass depending what it is locally available. Therefore, studies have been focused on exploring the suitability of using agricultural residues for small-scale heat and power generation using direct combustion. This study targets to compare the combustion of different agricultural residues in a single unit designed for wood pellets. The different biomass fuels used are circle divide 6 mm and circle divide 8 mmwood pellets, circle divide 6 mmbagasse pellets, circle divide 6 mmsunflower husk (SFH) pellets and Brazil nut (BN) shells. The results reveal a decrease in the fuel power input, higher oxygen levels in the flue gases and shorter cycles for ash removal when using the agricultural residues. The excess air ratio was calculated based on a mass balance and compared with a standard equation showing a good agreement. CO and NO emission levels as well as the relative conversion of fuel-C to CO were higher for the BN shells and SFH pellets in comparison to the other biomass types. SO2 emission was estimated based on the analysis of unburned sulfur in ash and mass balances; the higher estimated levels corresponded to the BN shells and SFH pellets. All the biomass sorts presented over 95% relative conversion of fuel-C to CO2. Wood pellets and BN shells presented the highest amount of unburned carbon in ash relative to the fuel-C. The relative conversion of fuel-N to NO and fuel-S to SO2 were higher for wood pellets. Bagasse pellets showed similar emission levels and relative conversion efficiency to wood pellets.
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31.
  • Carlsson, Per, et al. (författare)
  • Experimental investigation of an industrial scale black liquor gasifier : 1. Influence of reactor operation parameters on product gas composition
  • 2010
  • Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 89:12, s. 4025-4034
  • Tidskriftsartikel (refereegranskat)abstract
    • A novel technology to mitigate the climate changes and improve energy security is Pressurized Entrained flow High Temperature Black Liquor Gasification (PEHT-BLG) in combination with an efficient fuel synthesis using the resulting syngas. In order to optimise the technology for use in a pulp and paper mill based biorefinery, it is of great importance to understand how the operational parameters of the gasifier affect the product gas composition. The present paper is based on experiments where gas samples were withdrawn from the hot part of a 3 MW entrained flow pressurized black liquor gasifier of semi industrial scale using a high temperature gas sampling system. Specifically, the influence of process conditions on product gas composition (CO2, CO, H2, CH4, H2S, and COS) were examined by systematically varying the operational parameters: system pressure, oxygen to black liquor equivalence ratio, black liquor flow rate to pressure ratio and black liquor pre-heat temperature. Due to the harsh environment inside the gasification reactor, gas sampling is a challenging task. However, for the purpose of the current study, a specially designed high temperature gas sampling system was successfully developed and used. The results, obtained from two separate experimental campaigns, show that all of the investigated operational parameters have a significant influence on the product gas composition and present valuable information about to the process characteristics.
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32.
  • Chartier, Clement, et al. (författare)
  • Influence of jet-jet interactions on the lift-off length in an optical heavy-duty DI diesel engine
  • 2013
  • Ingår i: Fuel. - : Elsevier BV. - 1873-7153 .- 0016-2361. ; 112, s. 311-318
  • Tidskriftsartikel (refereegranskat)abstract
    • Several investigations have reported that the lift-off length on diesel jets depends strongly on the ambient temperature. The spacing between adjacent jets is thereby expected to influence the lift-off length, as it affects the amount of hot, burned gases present between the jets. Measurements on an 8-hole nozzle in an optical diesel engine showed that the lift-off length can be transient at all times between the start and end of injection. This is attributed to varying in-cylinder temperature and especially to the presence of hot combustion products in the gases entrained into the jets. The effect of inter-jet angle on lift-off length was investigated using symmetric and asymmetric nozzle cups. Decreasing the inter-jet angle produces shorter lift-off length. The lift-off length showed a weaker dependence on the ambient temperature in the engine than predicted by an empirical expression established in a constant-volume combustion vessel. These findings indicate that experiments in such vessels may not capture all features of the conditions in engines. The lift-off length tended to be 15% shorter on the downswirl (leeward) side of the jet. A strong interaction between the effects of the inter-jet spacing and the inlet temperature on the lift-off length was found. All these effects are attributed to the presence of hot gases between the jets. (C) 2013 Elsevier Ltd. All rights reserved.
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33.
  • Chelgani, Saeed Chehreh, et al. (författare)
  • Explaining relationships between coke quality index and coal properties by Random Forest method
  • 2016
  • Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 182, s. 754-760
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study was shown that random forest (RF) can be used as a sensible new data mining tool for variable importance measurements (VIMs) through various coal properties for prediction of coke quality (Free Swelling Index (FSI)). The VIMs of RF within coal analyses (proximate, ultimate, and petrographic analyses) were applied for the selection of the best predictors of FSI over a wide range of Kentucky coal samples. VIMs assisted by Pearson correlation through proximate, ultimate, and petrographic analyses indicated that volatile matter, carbon, vitrinite, and Rmax (coal rank parameters) are the most effective variables for the prediction of FSI. These important predictors have been used as inputs of RF model for the FSI prediction. Outputs in the testing stage of the model indicated that RF can predict FSI quite satisfactorily; the R2 was 0.93 and mean square error from actual FSIs was 0.15 (had less than interval unit of FSI; 0.5). According to the result, by providing nonlinear inter-dependence approximation among parameters for variable selection and also non-parametric predictive model RF can potentially be further employed as a reliable and accurate technique for the determination of complex relationship through fuel and energy investigations.
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34.
  • Chelgani, Saeed Chehreh, et al. (författare)
  • Relationships between noble metals as potential coal combustion products and conventional coal properties
  • 2018
  • Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 226, s. 345-349
  • Tidskriftsartikel (refereegranskat)abstract
    • Increasing coal consumption has generated million tons of ash and caused various environmental issues. Exploring statistical relationships between concentrations of valuable metals in coal and other coal properties may have several benefits for their commercial extraction as byproducts. This investigation studied relationships between conventional coal concentrations and concentration of noble metals for a wide range (708 samples) of eastern Kentucky coal samples (EKCS) by statistical methods. The results indicate that there are significant positive Pearson correlations (r) > 0.90 among all noble metals (Au, Pt, Pd, Ru and Rh) except for Ag (r < 0.2). The results also showed that the noble metals (except Ag) are associated with the minerals of the coal and have high positive correlations with ash (and high negative correlations with the organic fraction). Modeling through the database demonstrated that the highest Au concentrations in the EKCS occur when Si is between 6000 and 8000 ppm and Fe is below 10000 ppm, and the highest Ag was observed when both Cu and Ni were over 40 ppm. Outcomes suggested that aluminosilicate minerals and pyrite are possibly the main host of noble metals (except Ag) in the EKCS whereas Ag might occur in various forms including organic association, mineral species, and as a native metal.
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35.
  • Christensen, Moah, et al. (författare)
  • The temperature dependence of the laminar burning velocities of methyl formate plus air flames
  • 2015
  • Ingår i: Fuel. - : Elsevier BV. - 1873-7153 .- 0016-2361. ; 157, s. 162-170
  • Tidskriftsartikel (refereegranskat)abstract
    • Laminar burning velocities, S-L, of methyl formate and air flames were determined at atmospheric pressure and initial gas temperatures, T, of 298, 318, 338 and 348 K. Measurements were performed in non-stretched flames, stabilized on a perforated plate burner at adiabatic conditions, generated using the heat flux method. These new experimental data shed light on discrepancies seen in previously published results, and the temperature dependence of the laminar burning velocity of methyl formate was analysed using expression S-L = S-L0(T/T-0)(alpha). It was found that the power exponent, alpha, has a minimum close to equivalence ratio, phi, of 1.0. Both the laminar burning velocities and alpha coefficient were compared with predictions of the mechanisms of Glaude et al. (2005), Dooley et al. (2010) and Dievart et al. (2013). While the two latter mechanisms are in generally good agreement in lean mixtures, the Glaude mechanism over predicts the experimental burning velocities over the entire range of equivalence ratios. The temperature dependences predicted by the Glaude and Dievart mechanisms, however, are rather close and agree well with the measurements. To elucidate these differences and similarities in the performance of two mechanisms, the sensitivity analysis of the power exponent alpha was performed for the first time. It was demonstrated that examination of the temperature dependence of the burning velocity provides an independent approach for analysis of experimental data consistency. (c) 2015 Elsevier Ltd. All rights reserved.
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36.
  • Cifuentes, Luis, et al. (författare)
  • Chemical Explosive Mode Analysis for a Jet-in-Hot-Coflow burner operating in MILD combustion
  • 2018
  • Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 232, s. 712-723
  • Tidskriftsartikel (refereegranskat)abstract
    • Large Eddy Simulations (LES) of Moderate and Intense Low oxygen Dilution (MILD) combustion of a Jet-in-HotCoflow (JHC) burner were performed using detailed chemistry. On the contrary to traditional flames, where heat release is occurring in very thin fronts, MILD combustion occurs in the distributed reaction regime where the reaction zone is broad, thus, this paper applies a direct Arrhenius closure with detailed chemistry to resolve important details of the fuel oxidation reactions. Comparisons of LES results are in good agreement with experiments, demonstrating that the simulations capture the intermediate species and finite reaction rate effects. A Chemical Explosive Mode Analysis (CEMA) was used to determine the flame structure and to detect the pre-and post-ignition regions, including the contributions to the CEMs analyzing the Explosion Index (EI) and Participation Index (PI). To the best of our knowledge, a detailed study of CEMA on MILD or flameless regime has never been reported. The flame structure was clearly visualized with CEMA, as well as the lean and the rich flame fronts. Different flame zones close to the anchoring points of these turbulent lifted flames were selected and the analysis demonstrates the contributions of dominant chemical species, such as HO2 and O. The reactions related to the dominant local CEM were obtained to highlight the nature of the stabilization in these highly diluted operating conditions.
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37.
  • Cladek, Bernadette R., et al. (författare)
  • In situ inelastic neutron scattering of mixed CH4–CO2 hydrates
  • 2022
  • Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 327
  • Tidskriftsartikel (refereegranskat)abstract
    • An abundant source of CH4 can be found in natural hydrate deposits. Recent demonstration of CH4 recovery from hydrates via CO2 exchange has revealed the potential as a fuel source that also provides a medium for carbon sequestration. It is vital to understand the structural and dynamic impacts of guest variation in CH4, CO2, and mixed hydrates and link the results to the stability of various deposits in nature, harvesting methane, and sequestering CO2. Molecular vibrations are examined in CH4, CO2, and mixed CH4-CO2 hydrates at 5 and 190 K and Xe hydrates for comparison. Inelastic neutron scattering (INS) is an ideal spectroscopy technique to observe the dynamic modes in the hydrate structure and enclathrated CH4, as it is extremely sensitive to 1H. The presence of CO2 in hydrates tightens the lattice. It introduces more active librational modes to the host lattice, while hindering the motion of CH4 in mixed CH4-CO2 hydrate at 5 K. At 190 K, a large broadening of the CH4 librational modes indicates disorder in the structure leading to dissociation.
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38.
  • Dal Belo Takehara, Marcelo, 1987-, et al. (författare)
  • Investigation of oxygen-enriched biomass flames in a lab-scale entrained flow reactor
  • 2024
  • Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 366
  • Tidskriftsartikel (refereegranskat)abstract
    • Oxygen-enriched air combustion of pulverized biomass fuel is an effective method to improve char combustion and improve flame stability. Moreover, understanding the impact of O2 addition is an important step toward oxyfuel combustion, one of the most promising technologies for bioenergy with carbon capture and storage (BECCS). Our previous studies focused on flow manipulation methods, e.g., swirling co-flow and acoustic forcing, to enhance particle dispersion during biomass combustion and gasification. This work aims to extend the understanding of the effect of different manipulation methods on oxygen-enriched combustion at different levels in a lab-scale entrained flow reactor. This methodology combines the analysis of visible flame characteristics, CO and NO gas emissions, and coarse particle emissions characterization with thermogravimetric analysis and particle size distribution by dynamic imaging. The results indicated that oxygen-enriched combustion leads to lower liftoff distance and higher flame brightness. Moreover, oxygen-enriched combustion presented coarse particle emissions with finer particle size distribution and lower carbon content. The acoustic forcing further decreased the flame liftoff and decreased CO emissions, increasing combustion efficiency under conditions with similar equivalence ratios and lower momentum flux at the secondary air.
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39.
  • Dimitriadis, Athanasios, et al. (författare)
  • Biomass conversion via ablative fast pyrolysis and hydroprocessing towards refinery integration : Industrially relevant scale validation
  • 2023
  • Ingår i: Fuel. - : Elsevier Ltd. - 0016-2361 .- 1873-7153. ; 332
  • Tidskriftsartikel (refereegranskat)abstract
    • Reducing the use of fossil fuels is an ongoing and important effort considering the environmental impact and depletion of fossil-based resources. The combination of ablative fast pyrolysis and hydroprocessing is explored as a pathway allowing bio-based intermediates (BioMates) integration in underlying petroleum refineries. The proposed technology is validated in industrially relevant scale, identifying pros and cons towards its commercialization. Straw from wheat, rye and barley was fed to ablative fast pyrolysis rendering Fast Pyrolysis Bio-Oil (FPBO) as the main product. The FPBO was stabilized via slurry hydroprocessing, rendering a stabilized FPBO (sFPBO) with 49 % reduced oxygen content, 71 % reduced carbonyl content and 49 % reduced Conradson carbon residue. Fixed bed catalytic hydroprocessing of sFPBO resulted in the production of BioMates, a high bio-content product to be co-fed in established refinery units. Compared to the starting biomass, BioMates has 83.6 wt% C content increase, 92.5 wt% O content decrease, 93.0 wt% water content decrease, while the overall technology has 20 wt% conversion yield (32 wt% carbon yield) from biomass to BioMates. © 2022 The Author(s)
  •  
40.
  • Ding, Saiman, et al. (författare)
  • Time-resolved alkali release during steam gasification of char in a fixed bed reactor
  • 2024
  • Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 356, s. 129528-
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study time-resolved char conversion and alkali release under steam gasification conditions were investigated using a fixed bed reactor. The behaviour of an industrial char and chars produced from straw and furniture waste was investigated. For woody chars, an increase in gasification reactivity is observed together with a notable alkali release as the gasification approaches completion (degree of conversion > 0.8). In contrast, straw char exhibited a decrease in conversion rate and alkali release throughout the gasification process, attributed to the formation of catalytically inactive potassium silicates inhibiting the catalytic role of alkali. Aerosol particles in the 0.01–22 µm size range are emitted during the char conversion. A fraction is formed by nucleation of alkali compounds and other condensable gases. A wide particle distribution that extends over the whole size range is also observed, and the particles are likely to consist of solid char fragments. The study concludes on the importance of alkali release, illustrating the difference in alkali release pattern for high and low ash char.
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41.
  • Ding, Zheli, et al. (författare)
  • A thermo-chemical and biotechnological approaches for bamboo waste recycling and conversion to value added product: Towards a zero-waste biorefinery and circular bioeconomy
  • 2023
  • Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 333
  • Tidskriftsartikel (refereegranskat)abstract
    • Fast growth of bamboo species make them a suitable candidate for eco-restoration, while its lignocellulosic substrate could be used for production of high-value green products such as biofuels, chemicals, and biomaterials. Within these frameworks, this review comprehensively explored the thermochemical and biological conversion of bamboo biomass to value-added fuels and chemicals. Additionally, this review stretches an in-depth understanding of bamboo biomass lignin extraction technologies and bioengineered methodologies, as well as their biorefinery conversion strategies. Additionally, bamboo biomass often utilized in biorefineries are mostly constituted of cellulose, hemicellulose, and lignin, along with proteins, lipids, and a few micronutrients which are not utilized efficientely by current bioengineered techniques. The results indicates that the potential for producing high-value products from bamboo biomass has not been adequately explored. However, enormous potential is still available to make bamboo biorefinery technologies cost-effective, and environmentally sustainable, which are discussed in the current review comprehensively. Furthermore, processes such as pretreatment, enzymatic hydrolysis, and fermentation are essential to obtain final high-value bio-based products from bamboo biomass, therefore, this review critically designed to explore the current state of the art of these technologies. Overall, the current review establishes a zero-waste suastainable approachs for the reformation of bamboo biomass into chemicals, biofuels, and value-added products.
  •  
42.
  • Dirrenberger, P., et al. (författare)
  • Laminar burning velocity of gasolines with addition of ethanol
  • 2014
  • Ingår i: Fuel. - : Elsevier BV. - 1873-7153 .- 0016-2361. ; 115, s. 162-169
  • Tidskriftsartikel (refereegranskat)abstract
    • The adiabatic laminar burning velocities of a commercial gasoline and of a model fuel (n-heptane, iso-octane, and toluene mixture) of close research octane number have been measured at 358 K. Non-stretched flames were stabilized on a perforated plate burner at 1 atm. The heat flux method was used to determine burning velocities under conditions for which the net heat loss of the flame is zero. Very similar values of flame velocities have been obtained for the commercial gasoline and for the proposed model fuel. The influence of ethanol as an oxygenated additive has been investigated for these two fuels and has been found to be negligible for values up to 15% (vol). Measurements were also performed for ethanol and the three pure components of the model fuel at 298, 358 and 398 K. The results obtained for the studied mixtures, and for pure n-heptane, iso-octane, toluene and ethanol, have been satisfactorily simulated using a detailed kinetic mechanism. (C) 2013 Elsevier Ltd. All rights reserved.
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43.
  • Djuric Ilic, Danica, et al. (författare)
  • Integration of biofuel and DH production - Possibilities, potential and trade-off situations : A review
  • 2022
  • Ingår i: Fuel. - : Elsevier Science Ltd. - 0016-2361 .- 1873-7153. ; 320
  • Forskningsöversikt (refereegranskat)abstract
    • There are several barriers to increased use of biofuel in the transport sector (e.g., shortage of feedstocks, high production costs, and relatively low energy yields from standalone biofuel plants). One possible solution is integration of biofuel and district heating (DH) production. This study aims (1) to identify challenges (e.g. tradeoffs) related to integration and to suggests possible ways of dealing with these challenges, (2) to highlight factors that may influence effects on global GHG emissions from integration, (3) to highlight factors which should be considered when evaluating economic aspects related to integration. After conducting a systematic review using a prescribed and structured protocol, 38 articles were identified as relevant for this study. These articles present four different approaches for integration: delivering the excess heat from biorefineries to DH networks, utilising DH in biofuel production processes, integrating biofuel production with existing DH facilities, and building new polygeneration biofuel production facilities in DH systems (DHS).If investments in biofuel compete with combined heat and power (CHP) production, the electricity price and the premium paid for renewable electricity influence profitability in CHP plants investments and therefore even profitability in investments in biofuel production. Competition should also be considered when weighing environmental benefits (the influence on global GHG emissions). Competition can create trade-offs related to DHSs operating conditions, limited local and global biomass availability, and limited available heat sinks. To deal with these trade-offs and to avoid suboptimization, stakeholders in regional planning, investors and policymakers should cooperate.All identified studies noted that a comprehensive approach is needed to evaluate profitability aspects and effects on global GHG emissions.For instance, utilising excess heat or residues from a biofuel production process in a DHS requires consideration of alternative DH production and alternative fuels. If electricity is one of the by-products from the biofuel production, alternative electricity production should also be considered. The majority of the studies dealt with economic performance of integration. Some of the factors found to influence profitability include available heat sink, alternative DH and electricity production, expected operation patterns, energy policy and energy market conditions. The potential for reducing global greenhouse gases (GHG) emissions depends on alternative DH and electricity production but also on biomass availability and alternative biomass users.
  •  
44.
  • Duan, Yumin, et al. (författare)
  • Sustainable biorefinery approaches towards circular economy for conversion of biowaste to value added materials and future perspectives
  • 2022
  • Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 325, s. 124846-124846
  • Tidskriftsartikel (refereegranskat)abstract
    • With the huge energy demand inevitably exacerbates the non-renewable resources depletion and ecological-social challenges, renewable energy has become a crucial participant in sustainable strategy. Biorefinery emerged as a sustainable approach and recognized promising transformation platforms for products, to achieve circular bioeconomy which focuses on the biomass efficient and sustainable valorization, promotes resource regeneration and restorative. The emerged biowaste biorefinery has proved as sustainable approach for integrated bioproducts and further applied this technology in industrial, commercial, agricultural and energy sectors. Based on carbon neutral sustainable development, this review comprehensive explained the biowaste as renewable resource generation and resource utilization technologies from the perspective of energy, nutrient and material recovery in the concept of biorefinery. Integrate biorefinery concepts into biowaste management is promise for conversion biowaste into value-added materials and contribute as driving force to cope with resource scarcity, climate changes and huge material demand in circular bioeconomy. In practice, the optimal of biorefinery technologies depends on environmentally friendly, economic and technical feasibility, social and policy acceptance. Additionally, policy interventions are necessary to promote biowaste biorefinery implements for circular bioeconomy and contribute to low-carbon cleaner environment.
  •  
45.
  • Duwig, Christophe, et al. (författare)
  • Large Eddy Simulation of turbulent combustion in a stagnation point reverse flow combustor using detailed chemistry
  • 2014
  • Ingår i: Fuel. - : Elsevier BV. - 1873-7153 .- 0016-2361. ; 123, s. 256-273
  • Tidskriftsartikel (refereegranskat)abstract
    • For meeting stringent emission restrictions, a modern solution is to operate in or close to the flameless mode. It implies a copious dilution of the reactants with vitiated gas resulting in low oxidant or fuel concentration and consequently low volumetric heat-release rate. On the contrary to traditional flames where heat release is occurring in very thin fronts, the flameless operation lies in the distributed reaction regime. Flameless operation is therefore associated with complex and non-linear interaction between mixing and chemical reactions. In this framework, this paper investigates turbulent combustion in a stagnation point reverse flow combustor and presents one of the first studies combining Large Eddy Simulation and detailed chemistry for capturing the reaction and flow dynamics during flameless combustion. The paper reports a comprehensive sensitivity analysis where the effects of the numerical discretization grid, of the chemical mechanism, of the operation (premixed vs. non-premixed) and of the heat-losses at the walls are studied and compared. Further, the simulation results are compared with experimental data from the literature, giving confidence in the quality of the predictions. The reaction and flow dynamics are extracted from the results using modal analysis, showing rotational and helical structures. Finally, the distribution of intermediate species in the reaction layer is investigated bringing some new insights into the flameless combustion process and providing recommendations for further experimental investigations. (C) 2014 Elsevier Ltd. All rights reserved.
  •  
46.
  • Dwari, Ranjan, et al. (författare)
  • Non-coking coal preparation by novel tribo-electrostatic method
  • 2008
  • Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 87:17-18, s. 3562-3571
  • Tidskriftsartikel (refereegranskat)abstract
    • A new laboratory fluidised bed tribo-electrostatic separator has been assembled and the beneficiation potential of thermal non-coking coal from Hingula block of Talcher coal field, India, is examined on this separator. The uniqueness of the separator originates from the efficient tribo-electrification of coal material in the cylindrical fluidised bed with internal baffle system. The collecting bins of the material underneath the copper plate electrodes are designed to function as Faraday cups such that the charge polarity and magnitude of particles in each bin can be measured directly. The liberation attributes of coal material is assessed by sink and float analysis of various size fractions. The mineral and maceral composition is determined by XRD and petrographic analysis. The separation tests were conducted at different tribo-charging and applied voltage conditions. The material collected in bins close to positive and negative electrodes show an ash content of 61% and 8% respectively, illustrating differential charge acquisition of mineral rich and coal rich particles during tribo-electrification. The charge results are in good agreement with the ash content of the coal material collected in the bins. The results showed that a clean coal of about 15% ash can be obtained from a coal containing 30% ash with about 70% yield. A better separation results can be achieved by recycling the material. The ash content in the clean coal is however limited by the liberation characteristics of the coal, which is evidenced by the SEM analysis of the particles in different bins. Thus, the tribo-electrostatic method observed to be a promising dry coal preparation technique.
  •  
47.
  • Edison, Thomas Nesakumar Jebakumar Immanuel, et al. (författare)
  • Deep eutectic solvent assisted electrosynthesis of ruthenium nanoparticles on stainless steel mesh for electrocatalytic hydrogen evolution reaction
  • 2021
  • Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 297
  • Tidskriftsartikel (refereegranskat)abstract
    • Deep eutectic solvents (DES) are considered as a green non-toxic electrolyte for the replacement of cyanide based toxic electrolytes towards the electrodeposition of noble metal and alloy nanoparticles on conducting surfaces. In this work, ruthenium nanoparticles (RuNPs) are electrochemically synthesized over cathodically treated stainless-steel mesh (CSS) by applying the cathodic current of −15 mA/cm2 using ruthenium chloride and deep eutectic mixture consists of choline chloride/urea as electrolyte. The resulting material is abbreviated as RuNPs@CSS and are characterized by surface analytical tools such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning elctron microscopy with energy dispersive spectrum (FE-SEM with EDS). Further, the electrocatalytic hydrogen evolution reaction (HER) activity of RuNPs@CSS is accessed and compared with state of art Pt electrode using open circuit potential (OCP), linear sweep voltammetry (LSV), Tafel plot and electrochemical impedance spectroscopy (EIS) measurements in 0.5 M H2SO4. The calculated HER's onset potential and over potential @ −10 mA/cm2 of RuNPs@CSS are about −0.0273 and −0.0657 V vs. RHE, which are very close to the bare Pt values. The EIS results suggested that, RuNPs@CSS possess excellent conductivity, which decrease the charge transfer resistance and enhances the HER. This study proved that the electrodeposited RuNPs@SS is better replacement for Pt based electrocatalysts towards acidic HER.
  •  
48.
  • Edo, Mar, et al. (författare)
  • The combined effect of plastics and food waste accelerates the thermal decomposition of refuse-derived fuels and fuel blends
  • 2016
  • Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 180, s. 424-432
  • Tidskriftsartikel (refereegranskat)abstract
    • Mechanical treatments such as shredding or extrusion are applied to municipal solid wastes (MSW) to produce refuse-derived fuels (RDF). In this way, a waste fraction (mainly composed by food waste) is removed and the quality of the fuel is improved. In this research, simultaneous thermal analysis (STA) was used to investigate how different mechanical treatments applied to MSW influence the composition and combustion behaviour of fuel blends produced by combining MSW or RDF with wood in different ratios. Shredding and screening resulted in a more efficient mechanical treatment than extrusion to reduce the chlorine content in a fuel, which would improve its quality. This study revealed that when plastics and food waste are combined in the fuel matrix, the thermal decomposition of the fuels are accelerated. The combination of MSW or RDF and woody materials in a fuel blend has a positive impact on its decomposition.
  •  
49.
  • Edwards, Ylva, et al. (författare)
  • Rheological effects of commercial waxes and polyphosphoric acid in bitumen 160/220 : low temperature performance
  • 2006
  • Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 85:7-8, s. 989-997
  • Tidskriftsartikel (refereegranskat)abstract
    • Effects of adding three commercial waxes and a polyphosphoric acid to three bitumens of 160/220 penetration grade were studied using different types of laboratory equipment, such as dynamic shear rheometer (DSR), bending beam rheometer (BBR), differential scanning calorimeter (DSC), force ductilometer (FD) as well as equipment for determining conventional parameters like penetration, softening point and Fraass breaking point. The paper deals with low-temperature effects, which could influence the thermal cracking resistance of asphalt concrete pavements. The results show that magnitude and type of effect on bitumen rheology depend on the bitumen itself as well as type and amount of additive used. Bitumen composition was found to be of decisive importance. Adding polyethylene wax or polyphosphoric acid, especially to nonwaxy 160/220-penetration grade bitumen, showed positive effects on the rheological behaviour at low temperatures.
  •  
50.
  • Elled, Anna-Lena, et al. (författare)
  • Influence of phosphorus on sulphur capture during co-firing of sewage sludge with wood or bark in a fluidised bed
  • 2006
  • Ingår i: Fuel. - 0016-2361 .- 1873-7153. ; 85:12, s. 1671-1678
  • Tidskriftsartikel (refereegranskat)abstract
    • Interference from phosphorus on sulphur capture during co-firing of sludge with wood has been investigated in a circulating fluidised bed boiler. Chemical equilibrium analyses were performed on the combustion system to complement the experimental results. It was found that the relatively high content of phosphorus in municipal sewage sludge interferes with the sulphur capture by occupying calcium, which otherwise would be available for reaction with sulphur. This fact must be taken into account when sulphur capture strategies are decided for reduction of sulphur dioxide emissions from sewage sludge as an additional fuel.
  •  
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