| 1. |
- Ruivo, L. C. M., et al.
(författare)
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Iron-based catalyst (Fe2-xNixTiO5) for tar decomposition in biomass gasification
- 2021
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 300
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a novel Fe2-xNixTiO5 catalyst for potential applications in biomass gasification gas cleaning/ upgrading was investigated. The material was successfully synthesized through combined mechanical activation and microwave firing. Catalytic steam reforming was studied in a fixed bed tubular reactor, using a mixture of toluene and naphthalene as model tar compounds as well as downstream a fluidized bed gasifier. Fe2-xNixTiO5 catalyst showed high activity in converting the model compounds at temperatures higher than 700 degrees C. The catalyst exhibited a tar conversion of 78% at 800 degrees C when exposed to biomass-derived gas from a bubbling fluidized bed gasifier. Nevertheless, the catalytic activity declined with increased time on stream due to structural changes in iron active phases, caused by redox conditions of the producer gas. Furthermore, thermodynamic calculations suggest that sulfur chemisorption on the nickel surface, may also contribute to the catalyst deactivation.
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| 2. |
- Vicente, E.D., et al.
(författare)
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Emissions from residential pellet combustion of an invasive acacia species
- 2019
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Ingår i: Renewable energy. - : Elsevier. - 0960-1481 .- 1879-0682. ; 140, s. 319-329
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Tidskriftsartikel (refereegranskat)abstract
- Currently, different types of raw materials are under investigation to fulfil the demand for pellet-based renewable energy. The aim of this study was to experimentally quantify and characterise the gaseous and particulate matter (PM10) emissions from the combustion of a pelletised invasive species growing in the Portuguese coastal areas. The combustion of acacia pellets in a stove used for domestic heating led to a noticeable production of environmentally relevant contaminants, such as carbon monoxide (CO, 2468 ± 485 mg MJ−1), sulphur dioxide (SO2, 222 ± 115 mg MJ−1) and nitrogen oxides (NOx, 478 ± 87 mg MJ−1). Besides gaseous pollutant emissions, substantial particle emissions (118 ± 14 mg MJ−1) were also generated. Particles consisted mostly of inorganic matter, mainly alkaline metals, sulphur and chlorine. About 25%wt. of the PM10 emitted had carbonaceous nature. The chromatographically resolved organic compounds were dominated by anhydrosugars, especially levoglucosan (284 μg g−1 PM10), and several types of phenolic compounds. Retene (8.77 μg g−1 PM10) was the chief compound among polyaromatic hydrocarbons.
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| 3. |
- Pio, D. T., et al.
(författare)
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Tar formation during eucalyptus gasification in a bubbling fluidized bed reactor : Effect of feedstock and reactor bed composition
- 2021
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 229
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Tidskriftsartikel (refereegranskat)abstract
- Tar compounds are inevitably present in the raw producer gas from biomass gasification and currently represent the main barrier for the commercial breakthrough of gasification technologies. In the present work, tar concentration in the producer gas from direct gasification of distinct types of residual forest biomass from eucalyptus in a 5 kWth bubbling fluidized bed reactor was investigated. The influence of the feedstock chemical composition and gasifier operation time was evaluated. Average tar concentration values in the raw producer gas were between 1.5 and 13.3 g/Nm3, representing a tar production between 8.4 and 67.0 g tar/kg biomass db, which surpasses suggested tar concentration limits for various potential applications for the producer gas. Major average tar compounds present in the tar sampled from the raw producer gas were benzene (47.1 %wt), toluene (21.6 %wt), naphthalene (10 %wt) and indene (6.4 %wt). A significant decay of the tar concentration in the producer gas was observed with increasing gasifier operation time, namely up to 50% within 45 min of operation, indicating its dependency on inorganics (e.g., CaCO3, KCl, maximum 5.5 %wt) and solid carbon (maximum 22.7 %wt) accumulation in the reactor bed.
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| 4. |
- Neves, Daniel Santos Felix, 1982, et al.
(författare)
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Characterization and prediction of biomass pyrolysis products
- 2011
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Ingår i: Progress in Energy and Combustion Science. - : Elsevier BV. - 0360-1285. ; 37:5, s. 611-630
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Tidskriftsartikel (refereegranskat)abstract
- In this study some literature data on the pyrolysis characteristics of biomass under inert atmosphere were structured and analyzed, constituting a guide to the conversion behavior of a fuel particle within the temperature range of 200-1000 degrees C. Data is presented for both pyrolytic product distribution (yields of char, total liquids, water, total gas and individual gas species) and properties (elemental composition and heating value) showing clear dependencies on peak temperature. Empirical relationships are derived from the collected data, over a wide range of pyrolysis conditions and considering a variety of fuels, including relations between the yields of gas-phase volatiles and thermochemical properties of char, tar and gas. An empirical model for the stoichiometry of biomass pyrolysis is presented, where empirical parameters are introduced to close the conservation equations describing the process. The composition of pyrolytic volatiles is described by means of a relevant number of species: H(2)O, tar, CO(2), CO, H(2), CH(4) and other light hydrocarbons. The model is here primarily used as a tool in the analysis of the general trends of biomass pyrolysis, enabling also to verify the consistency of the collected data. Comparison of model results with the literature data shows that the information on product properties is well correlated with the one on product distribution. The prediction capability of the model is briefly addressed, with the results showing that the yields of volatiles released from a specific biomass are predicted with a reasonable accuracy. Particle models of the type presented in this study can be useful as a submodel in comprehensive reactor models simulating pyrolysis, gasification or combustion processes.
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| 5. |
- Neves, Daniel Santos Felix, 1982, et al.
(författare)
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Method for online measurement of the CHON composition of raw gas from biomass gasifier
- 2014
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Ingår i: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 113, s. 932-945
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Tidskriftsartikel (refereegranskat)abstract
- For unattended biomass gasification processes, rapid methods for monitoring the elemental composition (CHON) of the raw gas leaving the gasifier are needed. Conventional methods rely on time-consuming and costly laboratory procedures for analysing the condensable part of the raw gas. An alternative method, presented in this work, assesses the CHON composition of raw gas in a "one step" analysis without the need to previously characterise its chemical species composition. Our method is based on the quantitative conversion of a raw gas of complex chemical composition into CO2, H2O, and N2 in a small combustor. The levels of these simple species can be measured with high accuracy and good time resolution, and the CHON composition of the raw gas can be determined from the mass balance across the combustor. To evaluate this method, an online combustion facility was built and used to analyse the raw gas from the Chalmers 2-MWth dual fluidised bed steam gasifier. Test runs of the developed facility demonstrated complete combustion of the raw gas and the measurements were both fast and reliable. The new method used in combination with zero-dimensional reactor modelling provides valuable data for the operational monitoring of gasification processes, such as the degree of fuel conversion, composition of the char exiting the gasifier, oxygen transport by catalytic bed material, and amount of condensables in raw gas.
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| 6. |
- Neves, D., et al.
(författare)
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Volatile gases from biomass pyrolysis under conditions relevant for fluidized bed gasifiers
- 2017
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Ingår i: Journal of Analytical and Applied Pyrolysis. - : Elsevier BV. - 0165-2370. ; 127, s. 57-67
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Tidskriftsartikel (refereegranskat)abstract
- The pyrolytic volatiles released from a converting biomass particle are investigated in this work through laboratorial fluidized bed experiments simulating conditions typical of large-scale gasifiers. Two types of wood (eucalyptus and pine) and two types of pellets (forest residues and wood) with particles of 6-8 mm in diameter are fed over the hot bubbling bed at temperatures within 600-975 degrees C. The resultant major pyrolytic products (char, soot, liquids and permanent gas) are collected to verify the overall mass balance, and the composition of the permanent gas is resolved in C3H8, C2H6, C2H4, CH4, CO2, CO, and H-2. Primary pyrolysis of the parent fuel particles is essentially complete at 600 degrees C and further increase of the temperature mainly leads to a progressive change in the composition of the volatile gas mixture. Although the gas release does not attain thermodynamic equilibrium under the conditions tested, our results show that the yields of CO2 and light hydrocarbons go through maxima as temperature increases to give rise to CO and H-2 as the preferable species at high temperatures. As a whole, the gas composition evolves in such a way that the corresponding lower heating value steadily increases with temperature increase, from about 11 MJ/kg at 600 degrees C to above 17 MJ/kg at 950 degrees C. Furthermore, the yields of key gas species were found well correlated to each other (C2H4 vs. CH4, CH4 vs. CO and H-2 vs. CO), with the relation between the yields of H-2 and CO being slightly dependent on the composition of fuel.
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