| 1. |
- Andersson, Jim, et al.
(författare)
-
Multiscale Reactor Network Simulation of an Entrained Flow Biomass Gasifier : Model Description and Validation
- 2017
-
Ingår i: Energy Technology. - : Wiley. - 2194-4288. ; 5, s. 1-12
-
Tidskriftsartikel (refereegranskat)abstract
- This paper describes the development of a multiscale equivalent reactor network model for pressurized entrained flow biomass gasification to quantify the effect of operational parameters on the gasification process, including carbon conversion, cold gas efficiency, and syngas methane content. The model, implemented in the commercial software Aspen Plus, includes chemical kinetics as well as heat and mass transfer. Characteristic aspects of the model are the multiscale effect caused by the combination of transport phenomena at particle scale during heating, pyrolysis, and char burnout, as well as the effect of macroscopic gas flow, including gas recirculation. A validation using experimental data from a pilot-scale process shows that the model can provide accurate estimations of carbon conversion, concentrations of main syngas components, and cold gas efficiency over a wide range of oxygen-to-biomass ratios and reactor loads. The syngas methane content was most difficult to estimate accurately owing to the unavailability of accurate kinetic parameters for steam methane reforming.
|
|
| 2. |
- Bach-Oller, Albert, 1989-
(författare)
-
Alkali-enhanced gasification of biomass : laboratory-scale experimental studies
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Gasification seeks to break carbonaceous materials into synthetic gas (CO+H2) which can be subsequently upgraded into valuable products. Thus gasification can be utilized to convert low grade biomass stocks into carbon-neutral chemicals heat and power. Nonetheless, gasification produces tar and soot as a by-product, impurities which deposit on cold surfaces thereby risking operation downstream of the gasifier. Cleaning the syngas after the gasifier is a conventional way to attenuate the problem, yet a complex and expensive one. Thus, tar and soot should preferably be addressed already in the gasifier. Given that these impurities are non-equilibrium species they could be targeted by using some sort of catalytic material. Alkali elements have precisely shown to possess catalytic activity on char gasification, besides they have also been associated with a decrease in tar and soot. Yet, to design a functional alkali-catalysed gasification process we need to investigate in more detail on what exact products does alkali show an activity on, on what stage, under what circumstances and, on the measure that it is possible, the mechanism. This was investigated on the basis of experimental work that approached the topic from two opposite sides. On the one hand, we studied the effects of diluting the alkali content of a Na-rich black liquor (BL) by blending it with pyrolysis oil (PO), and on the other hand, we investigated adding various amounts of alkali on more conventional types of biomass fuels. Most of the experiments were conducted on a laminar drop tube furnace but the reactivity of BL chars was also studied through thermogravimetric analysis.Alkali was found to catalyse heterogeneous gasification reactions (e.g. char) and to lead to much lower yields of C2 hydrocarbons, heavy tars and soot, favouring the presence of lighter species over large aromatic clusters. Alkali was hypothesized to reduce the quantity of soot by inhibiting the formation and growth of PAH, key intermediates on the road to soot. Besides, it was found that the initial contact between the alkali and the organic matrix was not critical, neither for gas impurities nor regarding char conversion, suggesting that the activity of alkali was a gas-induced phenomenon. The latter implied the existence of a vaporization-condensation cycle that could supply alkali into the char. Nonetheless, the beneficial effects by alkali were impaired by the affinity of Si to capture K and form potassium silicates which are inert. This interaction effect was particularly noticeable on char conversion as the silicates are not only inert but also liquid and viscous and prompt to encapsulate the char particles, thereby limiting mass transfer.The experiments with blends of BL and PO showed that the concentration of alkali in BL could be decreased by 30% without any sign of a decrease in the catalytic activity on char gasification, thus indicating the existence a saturation threshold. Furthermore, adding PO into BL lead to a further reduction on the quantities of tar and soot, this finding was attributed to changes in the fuel composition unrelated to alkali. In any case the experiments with BL-based fuels showed lower amounts of tar and soot than those from alkali-impregnated biomass powder. The difference was partially attributed to the content of S in BL. The subsequent investigation targeting the role of S confirmed that S possessed a soot inhibiting role similar to that of alkali, yet unlike K, it did not show a catalytic effect on char gasification.
|
|
| 3. |
- Bach Oller, Albert, et al.
(författare)
-
Characterization of tar and soot formation for an improved co-gasification of black liquor and pyrolysis oil
- 2015
-
Konferensbidrag (populärvet., debatt m.m.)abstract
- Black liquor (BL) gasification is a proven process with very low tar generation at lower temperature than other entrained-flow biomass gasification processes. Recently, BL gasification technology was further expanded to increase feedstock flexibility by co-gasifying pyrolysis oil (PO) with BL. Economic advantage was shown by a techno-economic study. Our previous lab-scale studies using a thermo-gravimetric analyzer and a flat flame burner showed high char reactivity of sample mixture (30wt.% blend of PO into BL) as alkali content in BL kept high catalytic activity despite being diluted by the addition of PO. However, tar and soot formation from this new feedstock remained unknown. In this study, we investigated how the reaction conditions affect the formation of tar and soot to understand their formation mechanism and to suggest suitable operation conditions for the industrial processes. Experiments were carried out with fuel blends containing between 0 and 40wt.% of PO in BL using a laminar entrained flow reactor under the flow of N2/CO2. The effects of operating parameters were evaluated by varying temperature (1073-1673 K), partial pressure of CO2 (0-20 kPa), particle size (90-200 μm and 500-630 μm) and residence time. High temperature (i.e. 1673 K), high heating rate and short residence time experiments were performed to mimic industrial-scale conditions. Soot yield was under detection limit while low amounts of tar (mainly benzene) were formed at low temperature and decreased as the temperature increased. Addition of PO maintained the yields of tar and soot very low while it increased the syngas yield. Overall, this study demonstrated the feasibility of co-gasification of PO and BL and provided valuable information about tar formation under different operating conditions.
|
|
| 4. |
- 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.
|
|
| 5. |
- 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.
|
|
| 6. |
- Bach-Oller, Albert, 1989-, et al.
(författare)
-
Effect of potassium impregnation on the emission of tar and soot from biomass gasification
- 2019
-
Ingår i: Energy Procedia. - : Elsevier. - 1876-6102. ; 158, s. 619-624
-
Tidskriftsartikel (refereegranskat)abstract
- Entrained flow gasification of biomass has the potential to generate synthesis gas as a source of renewable chemicals, electricity, and heat. Nonetheless, formation of tar and soot is a major challenge for continuous operation due to the problems they cause at downstream of the gasifier. Our previous studies showed the addition of alkali in the fuel can bring significant suppression of such undesirable products.The present work investigated, in a drop tube furnace, the effect of potassium on tar and soot formation (as well as on its intermediates) for three different types of fuels: an ash lean stemwood, a calcium rich bark and a silicon rich straw. The study focused on an optimal method for impregnating the biomass with potassium. Experiments were conducted for different impregnation methods; wet impregnation, spray impregnation, and solid mixing to investigate different levels of contact between the fuel and the potassium.Potassium was shown to catalyze both homogenous and heterogeneous reactions. Wet and spray impregnation had similar effects on heterogeneous reactions (in char conversion) indicating that there was an efficient molecular contact between the potassium and the organic matrix even if potassium was in the form of precipitated salts at a micrometer scale. On the other hand, potassium in the gas phase led to much lower yields of C2 hydrocarbons, heavy tars and soot. These results revealed that potassium shifted the pathways related to tar and soot formation, reducing the likelihood of carbon to end up as soot and heavy tars by favouring the formation of lighter compounds such as benzene. A moderate interaction between the added potassium and the inherent ash forming elements were also observed: Potassium had a smaller effect when the fuel was naturally rich in silicon.The combined results open the door to a gasification process that incorporates recirculation of naturally occurring potassium to improve entrained flow gasification of biomass.
|
|
| 7. |
- Bach Oller, Albert, et al.
(författare)
-
Fuel conversion characteristics of black liquor and pyrolysis oil mixture for efficient gasification with inherent catalyst
- 2014
-
Ingår i: European biomass conference and exhibition proceedings. - 9788889407523
-
Konferensbidrag (refereegranskat)abstract
- This paper describes the technical feasibility of a catalytic co-gasification process using a mixture of black liquor (BL) and pyrolysis oil (PO). A technical concern is if gasifiers can be operated at low temperature (~1000 ºC) without problems of tar, soot or char, as is the case for pure BL due to the catalytic effect of fuel alkali. Hence, we investigated fuel conversion characteristics of BL/PO mixture: conversion of single droplet in flame, and char gasification reactivity. 20wt.% (BP20) and 30wt.% (BP30) were selected for weight fraction of PO because of lignin precipitation in BP30. Single droplet was devolatilized and gasified in a methane flame with a flat flame burner at various droplet sizes. Conversion time and swelling ratio were investigated with imaging. They were more sensitive to initial droplet size and reaction atmosphere than the mixing of BL and PO. Char gasification reactivity was measured in an isothermal thermogravimeter (iTG) at T=880–940 ºC and PCO2=1 bar. Both BP20 and BP30 showed complete char conversion and there was no statistically significant difference in char reactivity among BP20, BP30 and BL. These results show that PO can be co-gasified in BL gasification process without major changes in the operation.
|
|
| 8. |
- Bach-Oller, Albert, et al.
(författare)
-
Fuel conversion characteristics of black liquor and pyrolysis oil mixtures: Efficient gasification with inherent catalyst
- 2015
-
Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 79, s. 155-165
-
Tidskriftsartikel (refereegranskat)abstract
- Alkali metals inherent in black liquor (BL) have strong catalytic activity during gasification. A catalytic co-gasification process based on BL with pyrolysis oil (PO) has the potential to be a part of efficient and fuel-flexible biofuel production systems. The objective of the paper is to investigate how adding PO into BL alters fuel conversion under gasification conditions. First, the conversion times of single fuel droplet were observed in a flat flame burner under different conditions. Fuel conversion times of PO/BL mixtures were significantly lower than PO and comparable to BL. Initial droplet size (300–1500 μm) was the main variable affecting devolatilization, indicating control by external heat transfer. Char oxidation was affected by droplet size and the surrounding gas composition. Then, the intrinsic reactivity of char gasification was measured in an isothermal thermogravimetric analyser at T = 993–1133 K under the flow of CO2–N2 mixtures. All the BL-based samples (100% BL, 20% PO/80% BL, and 30% PO/70% BL on mass basis) showed very high char conversion. Conversion rate of char gasification for PO/BL mixtures was comparable to that of pure BL although the fraction of alkali metal in char decreased because of mixing. The reactivities of BL and BL/PO chars were higher than the literature values for solid biomass and coal chars by several orders of magnitude. The combined results suggest that fuel mixtures containing up to 30% of PO on mass basis may be feasible in existing BL gasification technology.
|
|
| 9. |
- Bach-Oller, Albert, 1989-, et al.
(författare)
-
On the role of potassium as a tar and soot inhibitor in biomass gasification
- 2019
-
Ingår i: Applied Energy. - : Elsevier Ltd. - 0306-2619 .- 1872-9118. ; 254
-
Tidskriftsartikel (refereegranskat)abstract
- The work investigates in a drop tube furnace the effect of potassium on carbon conversion for three different types of fuels: an ash lean stemwood, a calcium-rich bark and a silicon-rich straw. The study focuses on an optimal method for impregnating the biomass with potassium. The experiments are conducted for 3 different impregnation methods; wet impregnation, spray impregnation, and dry mixing to investigate different levels of contact between the fuel and the potassium. Potassium is found to catalyse both homogenous and heterogeneous reactions. All the impregnation methods showed a significant effect of potassium on heterogeneous reactions (char conversion). The fact that dry mixing of potassium in the biomass shows an effect reveals the existence of a gas-induced mechanism that supply and distributes potassium on the char particles. Concerning the effect of potassium on homogenous reactions, it is found that potassium in the gas phase leads to much lower yields of C2 hydrocarbons, heavy tars and soot. The results indicate that potassium reduces the likelihood of light aromatic to progress toward heavier polyaromatic hydrocarbons clusters, thereby inhibiting the formation of soot-like material. A moderate interaction between the added potassium and the inherent ash forming elements is also observed: Potassium has a smaller effect when the fuel is naturally rich in silicon. The combined results are of interest for the design of a gasification process that incorporates recirculation of naturally occurring potassium to improve entrained flow gasification of biomass.
|
|
| 10. |
|
|
| 11. |
- Biswas, Amit, et al.
(författare)
-
Change of pyrolysis characteristics and structure of woody biomass due to steam explosion pretreatment
- 2011
-
Ingår i: Fuel processing technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 92:10, s. 1849-1854
-
Tidskriftsartikel (refereegranskat)abstract
- Steam explosion (SE) pretreatment has been implemented for the production of wood pellet. This paper investigated changes in biomass structure due to implication of steam explosion process by its pyrolysis behavior/ characteristics. Salix wood chip was treated by SE at different pretreatment conditions, and then pyrolysis characteristic was examined by thermogravimetric analyzer (TGA) at heating rate of 10 K/min. Both pyrolysis characteristics and structure of biomass were altered due to SE pretreatment. Hemicellulose decomposition region shifted to low temperature range due to the depolymerization caused by SE pretreatment. The peak intensities of cellulose decreased at mild pretreatment condition while they increased at severe conditions. Lignin reactivity also increased due to SE pretreatment. However, severe pretreatment condition resulted in reduction of lignin reactivity due to condensation and re-polymerization reaction. In summary, higher pretreatment temperature provided more active biomass compared with milder pretreatment conditions. © 2011 Elsevier B.V. All rights reserved.
|
|
| 12. |
- Biswas, Amit, et al.
(författare)
-
Effect of pelletizing conditions on combustion behaviour of single wood pellet
- 2014
-
Ingår i: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 119:15, s. 79-84
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents how pelletizing die temperature and moisture content affect combustion behaviour of single wood pellet. Pine wood particles with two different moisture contents (i.e. 1 wt.% and 12 wt.%) were pelletized in a laboratory-scale single pelletizer (single die pellets) at die temperature of 20, 100, 150 and 200 °C. The pellets were combusted in a laboratory scale furnace at 800 °C. Time required for single pellet combustion generally increased with both increase of pelletizing temperature and moisture content of biomass. In addition, combustion behaviour of single die pellets was significantly different than those produced in a pilot scale pelletizing plant (semi-industrial scale pellet). That difference was due to variation in physical properties of pellets (e.g. density, and morphology).
|
|
| 13. |
|
|
| 14. |
- Biswas, Amit, et al.
(författare)
-
Simplification of devolatilization models for thermally-thick particles : differences between wood logs and pellets
- 2015
-
Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 274, s. 181-191
-
Tidskriftsartikel (refereegranskat)abstract
- Many phenomena affects devolatilization of relatively large wood particles, e.g. wood pellets and logs, including mass and heat transfer, chemical reactions and physical transformation such as shrinkage. Many studies investigated the importance of these phenomena through detailed mathematical models at particle scale, but the models need to be simplified at a certain degree to be implemented into large-scale simulation for gasifiers and boilers. This paper first presents how each physical and chemical parameter should be modelled for wood logs (low density and anisotropic) and wood pellets (high density and isotropic) through parametric studies with a detailed particle simulation. They required different sub-models for effective thermal conductivity and heat of reactions due to the difference in isotropy of particles between pellets and logs. Then, we demonstrated that a constitutive equation, i.e. analytical solution of the shrinking core model, is sufficient to express devolatilization rate of thermally-thick particles at the temperature of 1173 K with proper sub-models of physical and chemical parameters. The constitutive equation agreed better with experimental data of wood log than wood pellets, mainly because of the error caused during the consideration of the effect of convective cooling of char layer on thermal conductivity. Both detailed and simplified particle models were validated with the experimental data in an isothermal macro thermogravimeter allowing devolatilization of large particles
|
|
| 15. |
- Chan, Fan Liang, et al.
(författare)
-
Kinetic Study of Catalytic Steam Gasification of Biomass by Using Reactive Flash Volatilisation
- 2015
-
Ingår i: ChemCatChem. - : Wiley. - 1867-3880 .- 1867-3899. ; 7:8, s. 1329-1337
-
Tidskriftsartikel (refereegranskat)abstract
- Reactive flash volatilisation is an autothermal process to convert biomass into tar-free synthesis gas under steam-rich conditions. This article studies the kinetics of reactive flash volatilisation by using Ni, Pt[BOND]Ni, Ru[BOND]Ni, Re[BOND]Ni, and Rh[BOND]Ni catalysts supported on alumina. The rates of mass loss of cellulose, xylan, and lignin were measured and compared with those of the synthetic biomass mixture and pinewood sawdust. The kinetic parameters were calculated with and without catalysts by using a wire-mesh isothermal thermogravimetric analyser in an equimolar steam/N2 atmosphere and high heating rates of 8.6×102, 1.1×103, and 1.3×104 °C min−1 at 700, 750, and 800 °C, respectively. The results revealed three distinct regimes of the rate of mass loss: pyrolytic decomposition, reforming, and char gasification. The catalysts increased the rate of mass loss in the reforming regime. Rh[BOND]Ni and Ru[BOND]Ni supported catalysts showed higher reforming rates than other catalysts. This study provides direct evidence of the in situ catalytic removal of tar during gasification of biomass
|
|
| 16. |
- Chishty, Muhammad Aqib, et al.
(författare)
-
Numerical simulation of a biomass cyclone gasifier : Effects of operating conditions on gasifier performance
- 2021
-
Ingår i: Fuel processing technology. - : Elsevier. - 0378-3820 .- 1873-7188. ; 218
-
Tidskriftsartikel (refereegranskat)abstract
- In Nordic countries, biomass gasification in a cyclone gasifier combined with a gas engine has been employed to generate small scale heat and power. Numerical simulations were carried out to analyze the effect of different operating conditions on the functioning of the gasifier. Reynolds-Averaged Navier-Stokes equations are solved together with the eddy-break up combustion model in conjunction with a modified k − ϵ model to predict the temperature and the flow field inside the gasifier. Results were compared with the experimental measurements in a 4.4 MW cyclone gasifier constructed by Meva Energy AB at Hortlax, Piteå, Sweden. The predicted results were in good agreement with the experimental data and the model provides detailed information about the gas compositions, cold gas efficiency and temperature field. Furthermore, the model allows different operating scenarios to be examined in an efficient manner such as the number of inlets, fuel to air velocity difference (slip-velocity) and moisture content in the fuel feedstock. The cold gas efficiency, composition of product gases and outlet temperature were monitored for each test case. These findings help to understand the importance of geometry modification, feedstock contents and make it possible to scale-up the gasifier for future applications.
|
|
| 17. |
|
|
| 18. |
- Dal Belo Takehara, Marcelo, et al.
(författare)
-
Effect of acoustic perturbation on particle dispersion in a swirl-stabilized pulverized fuel burner: Cold-flow conditions
- 2022
-
Ingår i: Fuel processing technology. - : Elsevier. - 0378-3820 .- 1873-7188. ; 228
-
Tidskriftsartikel (refereegranskat)abstract
- Inter-particle distance and particle dispersion during gasification of biomass have been found to significantly affect soot emission. Consequently, enhanced particle dispersion decreases energy losses and the risk for blockages of downstream equipment, increasing the efficiency and reliability of entrained flow reactors (EFRs). In this work, we investigated the interactions between imposed acoustic oscillations and particle dispersion under non-reacting conditions in a co-axial burner for a lab-scale EFR. A flow of air, laden with pulverized stem wood particles (Norwegian Spruce) of three different sizes (63–112 μm, 200–250 μm, and 500–600 μm), was forced axially through the burner center tube at Reynolds numbers ranged from 800 to 1700, and loading ratio of 0.7–4.2. The influences on particle dispersion from variations of the Strouhal number (0.12–0.6), the pressure amplitude at synthetic jet cavity (0.5–4.0 kPap-p), the swirl number (0–2.3), and the center jet velocity (1.9–3.9 m s−1) were investigated. Post-processed shadowgraph images revealed the influence of acoustic perturbations, which generate large structures with high particle concentration for both swirling and non-swirling conditions. Time-averaged contour maps showed a significantly higher particle dispersion, quantified as dispersion angle, for higher values of forcing amplitude and swirl numbers, with a stronger influence from the forcing amplitude, especially at lower Stokes number.
|
|
| 19. |
|
|
| 20. |
- 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.
|
|
| 21. |
|
|
| 22. |
- Dal Belo Takehara, Marcelo, 1987-, et al.
(författare)
-
Pulverized biomass flame under imposed acoustic oscillations : Flame morphology and emission characteristics
- 2022
-
Ingår i: Fuel processing technology. - : Elsevier. - 0378-3820 .- 1873-7188. ; 238
-
Tidskriftsartikel (refereegranskat)abstract
- Forced intermittent combustion with periodical variations of pressure, velocity, and air-fuel ratios is a promising method to increase efficiency and reduce emissions from combustion and gasification applications. In this work, flame characteristics and emissions from a pulverized biomass burner are investigated under oscillations induced by an acoustically-driven synthetic jet. Instantaneous images of incandescent light emitted from flame were captured using high-speed cameras. The images were analyzed to identify the liftoff distance, flame length, and shape. The flame liftoff distance decreased under excited conditions, notably at high forcing amplitude applied to small particle size distribution (63-112 μm). In such conditions, acoustic forcing increases particle dispersion as presented in the previous work, providing conditions for earlier ignition due to enhanced fuel-air mixing besides reducing CO emissions. Flue gas emissions were influenced mainly by the particle size distribution, from which the 63-112 μm particle size presented the lowest values of CO and highest levels of NO emissions. The results presented stable flame edge positions for the particle size of 63-112 μm, while wide range particle distributions (0–600, 0-400 μm) had strong fluctuations, indicating high flame instability. The experimental work adds new insights regarding acoustic excitation in swirl burners, which could be used to optimize pulverized fuel combustion.
|
|
| 23. |
- Das, Oisik, et al.
(författare)
-
Flammability and mechanical properties of biochars made in different pyrolysis reactors
- 2021
-
Ingår i: Biomass and Bioenergy. - : Elsevier. - 0961-9534 .- 1873-2909. ; 152
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of pyrolysis reactors on the properties of biochars (with a focus on flammability and mechanical characteristics) were investigated by keeping factors such as feedstock, carbonisation temperature, heating rate and residence time constant. The reactors employed were hydrothermal, fixed-bed batch vertical and fixed-bed batch horizontal-tube reactors. The vertical and tube reactors, at the same temperature, produced biochars having comparable elemental carbon content, surface functionalities, thermal degradation pattern and peak heat release rates. The hydrothermal reactor, although, a low-temperature process, produced biochar with high fire resistance because the formed tarry volatiles sealed water inside the pores, which hindered combustion. However, the biochar from hydrothermal reactor had the lowest nanoindentation properties whereas the tube reactor-produced biochar at 300 °C had the highest nanoindentation-hardness (290 Megapascal) and modulus (ca. 4 Gigapascal) amongst the other tested samples. Based on the inherent flammability and mechanical properties of biochars, polymeric composites’ properties can be predicted that can include them as constituents.
|
|
| 24. |
- Dossow, Marcel, et al.
(författare)
-
Electrification of gasification-based biomass-to-X processes - a critical review and in-depth assessment
- 2024
-
Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry. - 1754-5692 .- 1754-5706. ; 17:3, s. 925-973
-
Forskningsöversikt (refereegranskat)abstract
- To address the impacts of climate change, it is imperative to significantly decrease anthropogenic greenhouse gas emissions. Biomass-based chemicals and fuels will play a crucial role in substituting fossil-based feedstocks and reducing emissions. Gasification-based biomass conversion processes with catalytic synthesis producing chemicals and fuels (Biomass-to-X, BtX) are an innovative and well-proven process route. Since biomass is a scarce resource, its efficient utilization by maximizing product yield is key. In this review, the electrification of BtX processes is presented and discussed as a technological option to enhance chemical and fuel production from biomass. Electrified processes show many advantages compared to BtX and electricity-based processes (Power-to-X, PtX). Electrification options are classified into direct and indirect processes. While indirect electrification comprises mostly the addition of H2 from water electrolysis (Power-and-Biomass-to-X, PBtX), direct electrification refers to power integration into specific processing steps by converting electricity into the required form of energy such as heat, electrochemical energy or plasma used (eBtX). After the in-depth review of state-of-the-art technologies, all technologies are discussed in terms of process performance, maturity, feasibility, plant location, land requirement, and dynamic operation. H2 addition in PBtX processes has been widely investigated in the literature with process simulations showing significantly increased carbon efficiency and product yield. Similar studies on direct electrification (eBtX) are limited in the literature due to low technological maturity. Further research is required on both, equipment level technology development, as well as process and system level, to compare process options and evaluate performance, economics, environmental impact and future legislation.
|
|
| 25. |
- Furusjö, Erik, et al.
(författare)
-
Co-gasification of pyrolysis oil and black liquor - a new track for production of chemicals and transportation fuels from biomass
- 2015
-
Konferensbidrag (refereegranskat)abstract
- Pressurized oxygen-blown entrained flow black liquor (BL) gasification, the Chemrec technology, has been demonstrated in a 3 MWth pilot plant in Piteå, Sweden for more than 25,000 h. The plant is owned and operated by Luleå University of Technology since 2013. It is well known that catalytic activity of alkali metals is important for the high reactivity of black liquor, which leads to a highly efficient BL gasification process. The globally available volume of BL is however limited and strongly connected to pulp production. By co-gasifying pyrolysis oil (PO) with BL it is possible to utilize the catalytic activity also for PO conversion to syngas. Adding PO leads to larger feedstock flexibility with the possibility of building larger biofuels plants based on BL gasification technology. This presentation summarizes new results from research activities aimed at developing and assessing the PO/BL co-gasification process. Results from laboratory experiments with PO/BL mixtures show that pyrolysis behavior and char gasification reactivity are similar to pure BL. This means that the decrease in the alkali metal concentration due to the addition of PO in the mixture does not decrease the reactivity. Pure PO is much less reactive. Mixing tests show that the fraction of PO that can be mixed into BL is limited by lignin precipitation as a consequence of PO acidity. Pilot scale PO/BL co-gasification experiments have been executed following design and construction of a new feeding system to allow co-feeding of PO with BL. The results confirm the conclusions from the lab scale study and prove that the co-gasification concept is practically applicable. Process performance of the pilot scale co-gasification process is similar to gasification of BL only with high carbon conversion and clean syngas generation. This indicates that the established BL gasification technology can be used for co-gasification of PO and BL without major modifications.
|
|
