| 1. |
- Aakko-Saksa, Païvi T., et al.
(författare)
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Renewable Methanol with Ignition Improver Additive for Diesel Engines
- 2020
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Ingår i: Energy and Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029.
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Tidskriftsartikel (refereegranskat)abstract
- Reduced emissions and environmental burden from shipping are an important aim of tightening emission regulations and ambitious climate change strategy. Renewable methanol produced from biomass or from other renewable sources represents one option to face these challenges. We studied the potential of renewable methanol to offer such benefits in diesel operation in a Scania ethanol engine, which is designed for additized ethanol fuel (ED95) containing ignition improver and lubricity additives. Methanol (MD95) with several types of ignition improver and lubricity additives was studied for use in diesel engines. MD95 fuels were clean-burning, emitting even less gaseous emissions than ED95, particularly when glycerol ethoxylate was used as an ignition improver. Particle mass and number emissions originating from additives in the experimental fuels could be reduced with an oxidation catalyst. Reduced additive dosing in the MD95 fuels was studied with the aid of fuel injection into the intake manifold. Overall, the results showed that the monofuel MD95 concept is a promising solution for smaller vessels equipped with 800-1200 kW engines. ©
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| 2. |
- Adanez-Rubio, Inaki, et al.
(författare)
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Investigation of Combined Supports for Cu-based Oxygen Carriers for Chemical-Looping with Oxygen Uncoupling (CLOU)
- 2013
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 27:7, s. 3918-3927
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Tidskriftsartikel (refereegranskat)abstract
- The chemical-looping with oxygen uncoupling (CLOU) process is a novel solution for efficient combustion with inherent separation of carbon dioxide. The process uses a metal oxide as an oxygen carrier to transfer oxygen from an air to a fuel reactor. In the fuel reactor, the metal oxide releases gas phase oxygen which oxidizes the fuel through normal combustion. In this study, Cu-based oxygen carrier materials that combine different supports of MgAl2O4, TiO2 and SiO2 are prepared and characterized with the objective of obtaining highly reactive and attrition resistant particles. The oxygen carrier particles were produced by spray-drying and were calcined at different temperatures ranging from 950 to 1030oC for 4 h. The chemical-looping performance of the oxygen carriers was examined in a batch fluidized-bed reactor in the temperature range of 900-950oC under alternating reducing and oxidizing conditions. The mechanical stability of the oxygen carriers was tested in a jet-cup attrition rig. All of the oxygen carriers showed oxygen uncoupling behaviour with oxygen concentrations close to equilibrium. During reactivity tests with methane, oxygen carriers with lower mechanical stability showed higher reactivity, yielding almost complete fuel conversion. Oxygen carrier materials based on support mixtures of MgAl2O4/TiO2, MgAl2O4/SiO2 and TiO2/SiO2 showed a combination of high mechanical stability, low attrition rates, good reactivity with methane and oxygen uncoupling behaviour.
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| 3. |
- Ahmadi, Mozhgan, et al.
(författare)
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Application of Solid-Phase Microextraction (SPME) as a Tar Sampling Method
- 2013
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 27:7, s. 3853-3860
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the result of an investigation of the potential use of solid-phase microextraction (SPME) as a tar sampling method. The SPME stationary phase used was 50 mu m of polydimethylsiloxane (PDMS) coated on a fused silica fiber. Tar model compounds normally present in a producer gas from gasifiers, benzene, toluene, indane, indene, naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, and pyrene, were used in the investigation. The adsorbed compounds were analyzed by injection into gas chromatography coupled to a flame ionization detector (GC- FID). The amount of adsorbed tar on the SPME fiber determined the detection and quantification limits for the method. The results showed that adsorption of tar model compounds on the SPME fiber increased with decreasing polarity. The adsorption of compounds increased with a decreasing temperature, enabling a possibility to tune the sensitivity of the method by changing the sampling temperature. Conclusively, SPME has a very high potential as a tar sampling method and, in combination with GC- FID trace analysis of tar, is a feasible application.
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| 4. |
- Ajdari, Sima, 1985, et al.
(författare)
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Evaluation of Operating and Design Parameters of Pressurized Flue Gas Systems with Integrated Removal of NO x and so x
- 2019
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 33:4, s. 3339-3348
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the operating and design parameters of product gas compression and integrated control of nitrogen oxides (NO x ) and sulfur oxides (SO x ) in large-scale oxy-fuel and chemical looping combustion processes. A process model that includes a comprehensive description of nitrogen and sulfur chemistry and mass transfer is developed. The results show that the fraction of NO oxidation into NO 2 will be 10-50% in a multistage compressor to 30 bars (1-4% O 2 in the gas) depending on the residence times in intercoolers and pressure levels. At lower O 2 concentrations (>0.1% O 2 in the gas), the oxidation is limited but still active. Nitric acid formation in the compressor condensate is, thus, inevitable, although limited, as most water is condensed in the early stages, whereas the acid gases are formed in the later stages. The NO 2 /NO x ratio has an important effect on the total amount of NO x absorbed and extra residence time should be added after the compressor to increase this ratio. Evaluation of the process behavior in relation to simultaneous absorption of SO 2 and NO x revealed that increased SO 2 /NO x ratio and bottom liquid recycling enhanced the total NO x absorption. In addition, maintaining the pH in the absorbing solution above 5 improves the removal efficiencies of NO x and SO 2 . NO x removal rates of up to around 95% can be achieved for SO 2 /NO x > 1 in the flue gas with appropriate design of the absorber. For SO 2 /NO x < 1, increasing the packing height or addition of S(IV) solutions could enhance the NO x removal rates to 95% or more. The model predictions are compared with the experimental data from a laboratory-scale absorber. The process model developed in this work enables design studies and techno-economic evaluation of absorption-based NO x and SO x removal concepts.
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| 5. |
- Alamia, Alberto, 1984, et al.
(författare)
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Process Simulation of Dual Fluidized Bed Gasifiers Using Experimental Data
- 2016
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 30:5, s. 4017-4033
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Tidskriftsartikel (refereegranskat)abstract
- Process simulation of a dual fluidized bed (DFB) gasifier is challenging, owing to the high degree of freedominherent to the operation of the double-reactor system and the complexity of the reactions therein. We propose a method forsimulation of the gasifier based on the analysis of experimental data and of the total uncertainty associated with them. The overallaim is to use data from the large amount of pilot and demonstration gasifiers in the analysis and optimization of gasification-basedprocesses. In the method proposed a set of fuel conversion variables and their associated uncertainties are calculated using astochastic approach that takes into account the effect of unclosed mass balance, incomplete characterization of the raw gascompounds and measurement errors. Subsequently, these fuel conversion variables are used to simulate the gasifier in a flowsheetmodel developed in Aspen Plus. The results include the evaluation of critical parameters, such as, gasifier efficiency, chargasification, and tar yield and their uncertainties, which depend highly on the measurement system. The method is applied todata sets derived from several measurement setups, and the results are validated with total carbon measurements. The resultsshow that detection of ≥95% of the carbon in the raw gas is necessary to maintain the uncertainty level at
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| 6. |
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| 7. |
- Allgurén, Thomas, 1986, et al.
(författare)
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Chemical Interactions between Potassium, Sulfur, Chlorine, and Carbon Monoxide in Air and Oxy-fuel Atmospheres
- 2020
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 34:1, s. 900-906
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents experimental and modeling work on the interaction between the K, Cl, and S components, and these chemical interactions are studied in both air-fuel and oxy-fuel atmospheres. Detailed kinetic modeling is conducted to examine the potassium chloride sulfation and its interaction with CO oxidation in both nitrogen- and carbon-dioxide-based atmospheres. The oxidation of CO enhances the kinetics of alkali sulfation for typical post-flame conditions, below 1000 °C, in both atmospheres. For higher temperatures, sulfation kinetics are promoted even further in CO2-rich atmospheres. Oxy-fuel atmospheres, i.e., CO2-rich atmospheres, also promote increased levels of CO in technical-scale flames. Therefore, in practical systems, enhanced sulfation kinetics will automatically be promoted by flue gas recirculation. Also, the availability of sulfur, in the form of an increased SO2 concentration, often enables complete sulfation of alkali in oxy-fuel atmospheres as a result of the flue gas recirculation. The availability of SO3 may increase in oxy-fuel compared to air-fuel atmospheres as a result of either elevated SO2 levels or different sulfation reaction patterns, as discussed in the modeling of this work. However, SO3 has no significant impact on the overall sulfation rates in oxy- compared to air-fired systems.
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| 8. |
- Allgurén, Thomas, 1986, et al.
(författare)
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Influence of KCI and SO2 on NO Formation in C3H8 Flames
- 2017
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 31:10, s. 11413-11423
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Tidskriftsartikel (refereegranskat)abstract
- The use of low-quality fuels in power generation plants is typically motivated by the potential for reducing fuel costs or CO2 emissions, the latter in the case of a fuel based on biomass. These features make low-quality fuels attractive, although their use for power generation is usually problematic due to their composition. One of the main issues is high-temperature corrosion (HTC), which is caused by alkali-containing chlorides. The alkali chlorides, which are formed from alkali metals and chlorine released from the fuel during the combustion process, are a particular problem. HTC is often related to the combustion of fuels with a low sulfur-to-potassium ratio, such as biomass, and it has a significant effect on the thermal efficiency and/or the maintenance cost of the power plant. Sulfuric and alkali species not only influence the formation of highly corrosive salts but also affect other aspects of combustion chemistry. While the present work relates to HTC chemistry, it focuses on how potassium chloride and sulfur dioxide influence the formation of NO. The experiments were carried out in a 100 kW test facility using C3H8 as the fuel. In order to examine the influence of SO2 and KCI on combustion, these two components were injected into the combustion reactor. In the experiments, pure gaseous SO2 was injected upstream of the burner. KCI was fed as an aqueous solution (3.34%, of KCI) that was sprayed directly into the flame. Pure water was also injected, to distinguish any possible interaction between KCI and water. Kinetic modeling was conducted to examine the reaction routes and activities. The results show that both KCI and SO2 suppress the formation of NO. KCI appears to inhibit the formation of NO, whereas SO2 decreases the concentration of NO by enhancing its oxidation to NO2.
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| 9. |
- Andersson, Viktor, 1994, et al.
(författare)
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Online Speciation of Alkali Compounds by Temperature-Modulated Surface Ionization: Method Development and Application to Thermal Conversion
- 2024
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Ingår i: ENERGY & FUELS. - 0887-0624 .- 1520-5029. ; 38:3, s. 2046-2057
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Tidskriftsartikel (refereegranskat)abstract
- A novel method for online speciation of potassium- and sodium-containing compounds has been described and demonstrated. The method is based on a temperature-modulated surface ionization (TMSI) technique and may be used to determine the concentrations of alkali chlorides, hydroxides, carbonates, and sulfates in high-temperature processes. The measurement device is a further development of a surface ionization detector (SID) commonly used for online alkali measurements in combustion, gasification, and pyrolysis research. Discrimination between sodium and potassium compounds is made possible by differences in their aerosol evaporation characteristics as a function of temperature combined with the desorption kinetics of alkali on a hot platinum filament. The method is evaluated in laboratory experiments with known alkali salt concentrations. An experimental procedure where the platinum filament in the SID is regularly shifted between three temperatures is concluded to provide sufficient selectivity and time resolution for common applications. The TMSI method is successfully applied to characterize the emission of alkali compounds during pyrolysis of pine wood. The emissions during low-temperature pyrolysis are dominated by KOH, while similar amounts of KOH and NaOH are subsequently emitted from the remaining char and ash. The ability of real-time characterization of individual sodium and potassium compounds opens up new means to understand and optimize solid fuel conversion of common fuels such as low-grade biomass, waste, and coal.
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| 10. |
- Arjmand, Mehdi, 1986, et al.
(författare)
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CaxLa1−xMn1−yMyO3−δ (M = Mg, Ti, Fe or Cu) as Oxygen Carriers for Chemical-Looping with Oxygen Uncoupling (CLOU)
- 2013
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 27:8, s. 4097-4107
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Tidskriftsartikel (refereegranskat)abstract
- Perovskite materials of the type CaxLa1−xMn1−yMyO3−δ (M = Mg, Ti, Fe or Cu) have been investigated as oxygen carriers for the chemical-looping with oxygen uncoupling (CLOU) process. The oxygen carrier particles were produced by mechanical homogenization of primary solids in a rotary evaporator followed by extrusion and calcination at 1300°C for 6 h. The chemical-looping characteristics of the substituted perovskites developed in this work were evaluated in a laboratory-scale fluidized-bed reactor in the temperature range of 900−1000°C during alternating reducing and oxidizing conditions. The oxygen carriers showed oxygen releasing behaviour (CLOU) in inert atmosphere between 900−1000°C. In addition, their reactivity with methane was high, approaching complete gas yield for all of the materials at 950°C, the exception being the Cu-doped perovskite which defluidized during reduction. The rates of oxygen release were also investigated using devolatilized wood char as solid fuel, and were found to be similar. The required solids inventory in the fuel reactor for the perovskite oxygen carriers is estimated to be 325 kg/MWth. All of the formulations exhibited high rates of oxidation and high degree of stability with no particle fragmentation or agglomeration. The high reactivity and favourable oxygen uncoupling properties make these oxygen carriers promising candidates for the CLOU process.
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