| 1. |
|
|
| 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.
|
|
| 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.
|
|
| 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.
|
|
| 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.
|
|
| 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.
|
|
| 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.
|
|
| 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.
|
|
| 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.
|
|
| 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.
|
|
| 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.
|
|
| 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.
|
|
| 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.
|
|
| 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.
|
|
| 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.
|
|
| 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.
|
|
| 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.
|
|
| 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.
|
|
| 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.
|
|
| 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.
|
|
| 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.
|
|
| 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. |
|
|
| 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.
|
|
