| 1. |
|
|
| 2. |
|
|
| 3. |
- Moldenhauer, Patrick, 1983, et al.
(författare)
-
Chemical-looping combustion with heavy liquid fuels in a 10 kW pilot plant
- 2017
-
Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820. ; 156, s. 124-137
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, chemical-looping combustion was performed with highly viscous vacuum residue. A fuel reactor with a fuel-injection system for liquid fuels was designed and built for a chemical-looping reactor with the nominal fuel input of 10 kWth. The gas velocities in the riser section and at the gas-distribution nozzles of this unit are comparable to those of industrial circulating fluidized-bed boilers. Reference experiments were performed with an ilmenite oxygen carrier and two different fuel blends that contained 40 wt.% and respectively 80 wt.% of vacuum residue in fuel oil 1. Fuel conversion was in line with that of experiments from an earlier campaign, where fuel oil 1 was used as fuel. The fuel contained a significant fraction of sulfur, but no SO2 was detected in the flue gas of the air reactor. More experiments were performed using an oxygen carrier based on calcium manganite. The oxygen carrier was exposed to fluidization at hot conditions (more than 600°C) for about 95 h, out of which fuel was injected during a total of 9.6 h. Undiluted vacuum residue, fuel oil 1 as well as different blends of these two were used as fuel. Furthermore, the parameters fuel flow, fuel-reactor temperature and air flow in the air reactor were varied to observe trends in fuel conversion. The experiments were carried out with a fuel flow corresponding to 4.0-6.2 kWth and an oxygen carrier-to-fuel ratio of about 1300-2000 kg/MWth (fuel-reactor bed mass per thermal fuel-power). With undiluted vacuum residue as fuel and a fuel-reactor temperature of 1000°C, up to 93% of all carbon leaving the fuel reactor was in the form of CO2. Carbon leakage from fuel reactor to air reactor was usually below 1% for all fuel types tested, but no SO2 was detected in the off-gas from the air reactor. The reactivity of the calcium manganite-based material decreased over the course of the experiments, which is likely due to sulfur poisoning. No defluidization or agglomeration problems were experienced over the course of the experimental campaign.
|
|
| 4. |
- Sefidari, Hamid, et al.
(författare)
-
The effect of disintegrated iron-ore pellet dust on deposit formation in a pilot-scale pulverized coal combustion furnace. Part II : Thermochemical equilibrium calculations and viscosity estimations
- 2018
-
Ingår i: Fuel processing technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 180, s. 189-206
-
Tidskriftsartikel (refereegranskat)abstract
- Fly ash particles from the combustion of solid-fuels together with disintegrated particles arising from iron-ore pellets result in accumulation of deposits on the refractory linings of the grate-kiln induration machine during the iron-ore pelletizing process. The deposits amass in the high-temperature regions of the induration furnace thus disturbing the flow of gas and pellets. Therefore, to tackle the above-mentioned issues, an understanding of deposit formation mechanism is of crucial importance. This study was conducted with the objective of addressing the effect of disintegrated iron-ore pellet dust on deposit formation and the mechanisms behind deposition (slagging) in the grate-kiln process. A comprehensive set of experiments was conducted in a 0.4 MW pilot-scale pulverized-coal- fired furnace where three different scenarios were considered as follows; Case 1 (reference case): Coal was combusted without the presence of pellet dust. Case 2: Natural gas was combusted together with simultaneous addition of pellet dust to the gas stream. Case 3: Coal was combusted together with the addition of pellet dust simulating the situation in the large-scale setup. Fly ash particles and short-term deposits were characterized and deposition was addressed in Part I of this study. In light of the experimental observations (Part I) and the thermochemical equilibrium calculations (Part II), a scheme of ash transformation during the iron-ore pelletizing process was proposed. The dissolution of hematite particles into the Ca-rich-aluminosilicate melt (from the coal-ash constituents) decreased the viscosity and resulted in the formation of stronger (heavily sintered) deposits. Overall, this pilot-scale work forms part of a wider study which aims at deepening the understanding of ash transformation phenomena during the large-scale pelletizing process.
|
|
| 5. |
- Mocholí Montañés, Rubén, 1990, et al.
(författare)
-
Dynamic Process Model Validation and Control of the Amine Plant at CO2 Technology Centre Mongstad
- 2017
-
Ingår i: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 10, s. 1527-
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a set of steady-state and transient data for dynamic process model validation of the chemical absorption process with monoethanolamine (MEA) for post-combustion CO2 capture of exhaust gas from a natural gas-fired power plant. The data selection includes a wide range of steady-state operating conditions and transient tests. A dynamic process model developed in the open physical modeling language Modelica is validated. The model is utilized to evaluate the open-loop transient performance at different loads of the plant, showing that pilot plant main process variables respond more slowly at lower operating loads of the plant, to step changes in main process inputs and disturbances. The performance of four decentralized control structures is evaluated, for fast load change transient events. Manipulation of reboiler duty to control CO2 capture ratio at the absorber's inlet and rich solvent flow rate to control the stripper bottom solvent temperature showed the best performance.
|
|
| 6. |
-
Systems Perspectives on Biorefineries 2013
- 2013
-
Samlingsverk (redaktörskap) (refereegranskat)abstract
- Replacing fossil fuels with biomass for the production of energy carriers, materialsand specialty chemicals is a challenge that now confronts humanity. In whichapplications shall we use limited resources of biomass? How can biomass berefined into the products we want? What are the consequences of demanding toomuch? What is an optimal design of a biorefinery? Where should they be located?What policy instruments are required to realise the biorefineries of the future?There is not one final answer to these questions. However, different systems studiescan provide us with complementary pieces of the puzzle. These can be valuableby themselves, or be brought together into a larger and more complex picture.Systems Perspectives on Biorefineries 2013 is an updated edition of SystemsPerspectives on Biorefineries 2012 and contains twelve chapters that address differenttopics related to the immensely important issue of how the world’s biomassresources can, or should, be converted into the goods we need and desire. Thebook is still far from complete, but it is a contribution and a start...
|
|
| 7. |
- Hosseini, Seyedehsan, 1994, et al.
(författare)
-
Alkyl ketene dimer modification of thermomechanical pulp promotes processability with polypropylene
- 2024
-
Ingår i: Polymer Composites. - 1548-0569 .- 0272-8397. ; 45:1, s. 825-835
-
Tidskriftsartikel (refereegranskat)abstract
- Alkyl ketene dimers (AKDs) are known to efficiently react with cellulose with a dual polarity in their structure: a polar component and a nonpolar component. AKD of three different carbon chain lengths, 4, 10, and 16 carbons have been synthesized, and thermomechanical pulp (TMP) fibers were modified by them. The modification of TMP fibers with AKD resulted in an increased water contact angle, showing the presence of the AKDs on the TMP fibers and a new carbonyl peak in the IR spectra, suggesting modification of the TMP fibers with AKD groups. Calculating the Hansen solubility parameters of AKD and AKD conjugated to TMP in polypropylene (PP) indicates improved compatibility, especially of longer chain AKD and TMP AKD. The rheological studies of the composites showed that the AKD with the longest carbon chain decreases the melt viscosity of the PP-TMP-AKD composite, which combined with the shape and the color of the extruded composite filaments indicates improved flow properties and reduced stress build up during processing. The research findings demonstrate the ability of AKD to enhance the dispersibility and compatibility of natural fibers with PP.
|
|
| 8. |
- Brandin, Jan, 1958-, et al.
(författare)
-
Multi-function catalysts for glycerol upgrading
- 2010
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- During the last three years Biofuel-Solution, a privately held Swedish entity, has developed an IP-portfolio around gas-phase glycerol conversion into medium-value chemicals. The targeted chemicals have large to very large markets, to allow for use by more than a fraction of the glycerol available today without impacting the cost of the product. The reason behind is that glycerol is a by-product from the biofuel industry, including biodiesel and bioethanol. This indicates large production volumes, even though the glycerol is a fraction of the fuel produced. A by-product from any fuel process will be vast and therefore any chemical produced from this side-product will have to have a large market to offset it to. In order to avoid changing the fundamental market behavior, similar to what the biodiesel industry has done to the glycerol market. In the course of this work, several end-products have been targeted. These include plastic monomers, mono-alcohols and energy gases; using acrolein as a common starting point. To produce chemicals with high purity and efficiency, selective and active catalysts are required. For instance, a process for producing propionaldehyde and n-propanol has been developed to the point of demonstration and commercialization building on the gas-phase platform. By developing multi-function catalysts which perform more than one task simultaneously, synergies can be reached that cannot be achieved with traditional catalysts. For instance, by combining catalyst functionalities, reactions that are both endothermic and exothermic can be performed simultaneously. This mean lower inlet reactor temperatures (in this particular case) and a more even temperature distribution. By performing the dehydration of glycerol to acrolein in combination with another, exothermal reaction by-products can be suppressed and yields increased. It also means that new reaction pathways can be achieved, allowing for new ways to produce chemicals and fuels from glycerol. As in the case of ethane production from acrolein, where a catalyst surface has been devised where acrolein is first adsorbed. The actual mechanism is unknown but in speculation, the adsorbed acrolein is decarbonyled into ethylene and carbon monoxide on a first reaction site. The formed carbon monoxide diffuses to another active site, where it reacts with water through the so called water-gas shift reaction to carbon dioxide and hydrogen. Said carbon dioxide leaves as an end-product, and the hydrogen diffuses to another active site where it reacts with ethylene to form ethane. This gives a way of producing energy gases from glycerol in a very compact reactor set-up, effectively reducing footprint and capital cost and increasing productivity of an installation.
|
|
| 9. |
- Eriksson, Gunnar, et al.
(författare)
-
Combustion and fuel characterisation of wheat distillers dried grain with solubles (DDGS) and possible combustion applications
- 2012
-
Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 102, s. 208-220
-
Tidskriftsartikel (refereegranskat)abstract
- The present transition to a sustainable global energy system requires that biomass is increasingly combusted for heat and power production. Agricultural fuels considered include alkali-rich fuels with high phosphorus content. One such fuel is wheat distiller’s dried grain with solubles (wheat DDGS) from wheat-based ethanol production. Further increases in ethanol production may saturate the current market for wheat DDGS as livestock feed, and fuel uses are therefore considered. Fuel properties of wheat DDGS have been determined. The ash content (5.4 ± 1.6 %wt d.s.) is similar to many agricultural fuels. In comparison to most other biomass fuels the sulphur content is high (0.538 ± 0.232 %wt d.s.), and so are the contents of nitrogen (5.1 ± 0.6 %wt d.s.), phosphorus (0.960. ± 0.073 %wt d.s.) and potassium (1.30 ± 0.35 %wt d.s.). To determine fuel-specific combustion properties, wheat DDGS and mixes between wheat DDGS and logging residues (LR 60 %wt d.s. and DDGS 40 %wt d.s.), and wheat straw (wheat straw 50 %wt d.s., DDGS 50 %wt d.s.) were pelletized and combusted in a bubbling fluidised bed combustor (5 kW) and in a pellets burner combustor (20 kW). Pure wheat DDGS powder was also combusted in a powder burner (150 kW). Wheat DDGS had a high bed agglomeration and slagging tendency compared to other biomass fuels, although these tendencies were significantly lower for the mixture with the Ca-rich LR, probably reflecting the higher first melting temperatures of K–Ca/Mg-phosphates compared to K-phosphates. Combustion and co-combustion of wheat DDGS resulted in relatively large emissions of fine particles (<1 μm) for all combustion appliances. For powder combustion PMtot was sixteen times higher than from softwood stem wood. While the Cl concentrations of the fine particles from the the mixture of LR and wheat DDGS in fluidised bed combustion were lower than from combustion of pure LR, the Cl- and P-concentrations were considerably higher from the wheat DDGS mixtures combusted in the other appliances at higher fuel particle temperature. The particles from powder combustion of wheat DDGS contained mainly K, P, Cl, Na and S, and as KPO3 (i.e. the main phase identified with XRD) is known to have a low melting temperature, this suggests that powder combustion of wheat DDGS should be used with caution. The high slagging and bed agglomeration tendency of wheat DDGS, and the high emissions of fine particles rich in K, P and Cl from combustion at high temperature, mean that it is best used mixed with other fuels, preferably with high Ca and Mg contents, and in equipment where fuel particle temperatures during combustion are moderate, i.e. fluidised beds and possibly grate combustors rather than powder combustors.
|
|
| 10. |
- Larsson, Ann-Charlotte, et al.
(författare)
-
Targeting by Comparison with Laboratory Experiments the SCR Catalyst Deactivation Process by Potassium and Zinc Salts in a Large-Scale Biomass Combustion Boiler
- 2006
-
Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 20:4, s. 1398-1405
-
Tidskriftsartikel (refereegranskat)abstract
- The deactivation of a commercial selective catalytic reduction (SCR) catalyst of type V2O5−WO3/TiO2 has been studied in this work through comparisons of results from a full-scale biomass combustion plant with those from laboratory experiments. In the latter, the catalyst was exposed to KCl, K2SO4, and ZnCl2 by both wet impregnation with diluted salt solutions and deposition of generated submicrometer aerosol particles by means of an electrostatic field. The reactivity of freshly prepared and deactivated catalyst samples was examined in the SCR reaction, for which the influence of the different salts and the method of exposure were explored. Chemical and physical characterizations of the catalyst samples were carried out focusing on surface area, pore volume, pore size, chemical composition, and the penetration profiles of potassium and zinc. Particle-deposition deactivation as well as commercially exposed catalyst samples were shown to impact surface area and catalyst activity similarly and to have penetration profiles with pronounced peaks. Salt impregnation influenced pore sizes and catalyst activity more strongly and showed flat penetration profiles. Deposition of submicrometer-sized particles on the monolithic SCR catalyst has been shown to induce deactivation of the catalyst with characteristics resembling those obtained in a commercial biomass combustion plant; the laboratory process can be used to further assess the deactivation mechanism by biomass combustion.
|
|
| 11. |
- Zhou, Ming, et al.
(författare)
-
Oligoamine ionic liquids supported on mesoporous microspheres for CO2 separation with good sorption kinetics and low cost
- 2020
-
Ingår i: Journal of CO2 Utilization. - : Elsevier. - 2212-9820 .- 2212-9839. ; 39
-
Tidskriftsartikel (refereegranskat)abstract
- Ionic liquids display good CO2 absorption capacity but poor absorption kinetics and high costs. In the present work, we show that these problems can be solved by impregnating the new low cost ionic liquid pentaethylenehexammonium chloride [PEHA][Cl] and the corresponding amine precursor on a low cost mesoporous microsphere support. Nitrogen adsorption/ desorption, high-resolution SEM and thermogravimetric analysis were employed to analyze the structural and thermal properties of the prepared sorbents. The CO2 adsorption and desorption performance was studied by column experiments and mathematical models were fitted to the data. The results showed that sorbents displayed excellent sorption kinetics and capacity, comparable to the best reports in the literature. In addition, the sorbents could be regenerated and displayed high thermal stability. Finally, the costs of the sorbents developed in the present work is much lower than previously reported sorbents. Therefore this novel supported IL system could be promising for industrial CO2 removal and recovery applications.
|
|
| 12. |
- Yu, Xiaowen, et al.
(författare)
-
Hydrogen Evolution Linked to Selective Oxidation of Glycerol over CoMoO4—A Theoretically Predicted Catalyst
- 2022
-
Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6832 .- 1614-6840. ; 12:14
-
Tidskriftsartikel (refereegranskat)abstract
- Electrochemical valorization of biomass waste (e.g., glycerol) for production of value-added products (such as formic acid) in parallel with hydrogen production holds great potential for developing renewable and clean energy sources. Here, a synergistic effort between theoretical calculations at the atomic level and experiments to predict and validate a promising oxide catalyst for the glycerol oxidation reaction (GOR) are reported, providing a good example of designing novel, cost-effective, and highly efficient electrocatalysts for producing value-added products at the anode and high-purity hydrogen at the cathode. The predicted CoMoO4 catalyst is experimentally validated as a suitable catalyst for GOR and found to perform best among the investigated metal (Mn, Co, Ni) molybdate counterparts. The potential required to reach 10 mA cm−2 is 1.105 V at 60 °C in an electrolyte of 1.0 ᴍ KOH with 0.1 ᴍ glycerol, which is 314 mV lower than for oxygen evolution. The GOR reaction pathway and mechanism based on this CoMoO4 catalyst are revealed by high-performance liquid chromatography and in situ Raman analysis. The coupled quantitative analysis indicates that the CoMoO4 catalyst is highly active toward C—C cleavage, thus presenting a high selectivity (92%) and Faradaic efficiency (90%) for formate production.
|
|
| 13. |
- Akhtar, Farid, et al.
(författare)
-
Preparation of graded silicalite-1 substrates for all-zeolite membranes with excellent CO2/H-2 separation performance
- 2015
-
Ingår i: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 493, s. 206-211
-
Tidskriftsartikel (refereegranskat)abstract
- Graded silicalite-1 substrates with a high gas permeability and low surface roughness have been produced by pulsed current processing of a thin coating of a submicron silicalite-1 powder onto a powder body of coarser silicalite-1 crystals. Thin zeolite films have been hydrothermally grown onto the graded silicalite-1 support and the all-zeolite membranes display an excellent CO2/H-2 separation factor of 12 at 0 degrees C and a CO2 permeance of 21.3 x 10(-7) mol m(-2) s(-1) Pa-1 for an equimolar CO2/H-2 feed at 505 kPa and 101 kPa helium sweep gas. Thermal cracking estimates based on calculated surface energies and measured thermal expansion coefficients suggest that all-zeolite membranes with a minimal thermal expansion mismatch between the graded substrate and the zeolite film should remain crack-free during thermal cycling and the critical calcination step.
|
|
| 14. |
- Zacharias, Savannah C., et al.
(författare)
-
Exploring Supramolecular Gels in Flow-Type Chemistry-Design and Preparation of Stationary Phases
- 2021
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 60:28, s. 10056-10063
-
Tidskriftsartikel (refereegranskat)abstract
- Two major challenges facing chemical synthesis are product isolation and catalyst recovery. One method to overcome these challenges is to perform the synthesis in a flow system with a catalytic stationary phase. However, the polymeric catalytic materials used in flow systems are often laborious to produce. In this study, we investigate a novel supramolecular gel as a catalytic stationary phase material. The gel is based on a modular, easy to synthesize, oxotriphenylhexanoate (OTHO) gelator comprised of a catalytic unit designed to catalyze the Knoevenagel reaction. The catalytic organogel enhances the rate of product formation and can be reused five times. Use of the OTHO to construct catalytic gels is a flexible technique that can be utilized to improve product isolation and reduce wastage of the catalyst.
|
|
| 15. |
- Salvador, Christian Mark, 1989, et al.
(författare)
-
Indoor ozone/human chemistry and ventilation strategies
- 2019
-
Ingår i: Indoor Air. - : Hindawi Limited. - 1600-0668 .- 0905-6947. ; 29:6, s. 913-925
-
Tidskriftsartikel (refereegranskat)abstract
- This study aimed to better understand and quantify the influence of ventilation strategies on occupant-related indoor air chemistry. The oxidation of human skin oil constituents was studied in a continuously ventilated climate chamber at two air exchange rates (1 h-1 and 3 h-1 ) and two initial ozone mixing ratios (30 and 60 ppb). Additional measurements were performed to investigate the effect of intermittent ventilation ("off" followed by "on"). Soiled t-shirts were used to simulate the presence of occupants. A time-of-flight-chemical ionization mass spectrometer (ToF-CIMS) in positive mode using protonated water clusters was used to measure the oxygenated reaction products geranyl acetone, 6-methyl-5-hepten-2-one (6-MHO) and 4-oxopentanal (4-OPA). The measurement data were used in a series of mass balance models accounting for formation and removal processes. Reactions of ozone with squalene occurring on the surface of the t-shirts are mass transport limited; ventilation rate has only a small effect on this surface chemistry. Ozone-squalene reactions on the t-shirts produced gas-phase geranyl acetone, which was subsequently removed almost equally by ventilation and further reaction with ozone. About 70% of gas-phase 6-MHO was produced in surface reactions on the t-shirts, the remainder in secondary gas-phase reactions of ozone with geranyl acetone. 6-MHO was primarily removed by ventilation, while further reaction with ozone was responsible for about a third of its removal. 4-OPA was formed primarily on the surfaces of the shirts (~60%); gas-phase reactions of ozone with geranyl acetone and 6-MHO accounted for ~30% and ~10%, respectively. 4-OPA was removed entirely by ventilation. The results from the intermittent ventilation scenarios showed delayed formation of the reaction products and lower product concentrations compared to continuous ventilation.
|
|
| 16. |
- Öhman, Sebastian, 1991-, et al.
(författare)
-
Selective kinetic growth and role of local coordination in forming Al2TiO5-based coatings at lower temperatures
- 2021
-
Ingår i: Materials Advances. - : Royal Society of Chemistry. - 2633-5409. ; 2:17, s. 5737-5751
-
Tidskriftsartikel (refereegranskat)abstract
- Negative thermal expansion is an elusive property found among certain materials, whose potential applications have remained limited due to the many challenges faced in their synthesis. Herein, we report the successful formation of aluminium titanate-based coatings (Al2TiO5), a material renowned for its low-to-negative thermal expansion, by the co-deposition of aluminium-isopropoxide and titanium-isopropoxide in a hot-wall chemical vapour deposition instrument. While coatings grown at 450 °C were amorphous as-deposited, a short-range order into the Al2TiO5-phase was found and analysed by using Raman spectroscopy. Upon subsequent annealing at 700 °C for 3 hours, crystalline coatings were achieved without forming any binary phases. The selective synthesis of the Al2TiO5 phase is ascribed to the precursors’ inherent chemical similarities, resulting in a kinetic targeting of this phase and a short-range homogeneity, entailing its preferred crystallisation. The role of local coordination is expressed by demonstrating the formation of intergrowth phases ascribed to lower coordinating interstices in the compound. Both the formation and crystallisation temperatures reported herein, as well as the timescales needed for the synthesises, are considerably lower than any conventional adopted solid-state techniques used so far to attain the Al2TiO5 phase.
|
|
| 17. |
-
Method and models used in the project Pathways to Sustainable European Energy Systems
- 2011
-
Samlingsverk (redaktörskap) (refereegranskat)abstract
- This book describes the research that has been carried out during the first period (2006-2010) of the Alliance for Global Sustainability (AGS) project "Pathways to Sustainable European Energy Systems". this interdisciplinary project involves more that 40 researchers and addresses various aspects of the challenges faced in transforming the European energy system. Presented in this book are the energy-related methods and models that originate from different scientific disciplines and traditions and that were applied in the Pathways project. Some of the analytical tools are well-known, well-documented, and widely used in academic research. Others have been developed (or refined) during the Pathways project and are therefore unique. The chapters of this book cover around 30 different methods and models used in the Pathways project and presents an overview of the processes through which the research was conducted and the methods and models were co-ordinated.
|
|
| 18. |
|
|
| 19. |
- Ge, Yaxin, et al.
(författare)
-
Effects of used bed materials on char gasification : Investigating the role of element migration using online alkali measurements
- 2022
-
Ingår i: Fuel processing technology. - : Elsevier. - 0378-3820 .- 1873-7188. ; 238
-
Tidskriftsartikel (refereegranskat)abstract
- Online alkali measurements using surface ionization are employed to study alkali release during heating of used industrial fluidized bed materials and gasification of biomass-based char and bed material mixtures. The alkali release from the bed materials starts at 820 °C and increases with temperature, the time a bed material has experienced in an industrial process, and in the presence of CO2. Online alkali measurement during heating of char mixed with used bed material shows significant alkali uptake by the char. Complementary SEM-EDS studies confirm the alkali results and indicate that other important inorganic elements including Si, Mg, and Ca also migrate from the bed material to the char. The migration of elements initially enhances alkali release and char reactivity, but significantly reduces both during the final stage of the gasification. The observed effects on char gasification become more pronounced with increasing amount of bed material and increasing time the material experienced in an industrial process. The ash-layer on the used bed material is concluded to play an important role as a carrier of alkali and other active components. The char and bed material systems are closely connected under operational conditions, and their material exchange has important implications for the thermal conversion.
|
|
| 20. |
- Punzi, Marisa, et al.
(författare)
-
Combined anaerobic-ozonation process for treatment of textile wastewater : Removal of acute toxicity and mutagenicity
- 2015
-
Ingår i: Journal of Hazardous Materials. - : Elsevier BV. - 0304-3894 .- 1873-3336. ; 292, s. 52-60
-
Tidskriftsartikel (refereegranskat)abstract
- A novel set up composed of an anaerobic biofilm reactor followed by ozonation was used for treatment of artificial and real textile effluents containing azo dyes. The biological treatment efficiently removed chemical oxygen demand and color. Ozonation further reduced the organic content of the effluents and was very important for the degradation of aromatic compounds, as shown by the reduction of UV absorbance. The acute toxicity toward Vibrio fischeri and the shrimp Artemia salina increased after the biological treatment. No toxicity was detected after ozonation with the exception of the synthetic effluent containing the highest concentration, 1. g/l, of the azo dye Remazol Red. Both untreated and biologically treated textile effluents were found to have mutagenic effects. The mutagenicity increased even further after 1. min of ozonation. No mutagenicity was however detected in the effluents subjected to longer exposure to ozone. The results of this study suggest that the use of ozonation as short post-treatment after a biological process can be beneficial for the degradation of recalcitrant compounds and the removal of toxicity of textile wastewater. However, monitoring of toxicity and especially mutagenicity is crucial and should always be used to assess the success of a treatment strategy. © 2015 Elsevier B.V.
|
|
| 21. |
- Winikka, Henrik, et al.
(författare)
-
Particle formation during pressurized entrained flow gasification of wood powder : Effects of process conditions on chemical composition, nanostructure, and reactivity
- 2018
-
Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180 .- 1556-2921. ; 189, s. 1339-1351
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of operating condition on particle formation during pressurized, oxygen blown gasification of wood powder with an ash content of 0.4 wt% was investigated. The investigation was performed with a pilot scale gasifier operated at 7 bar(a). Two loads, 400 and 600 kW were tested, with the oxygen equivalence ratio (λ) varied between 0.25 and 0.50. Particle concentration and mass size distribution was analyzed with a low pressure cascade impactor and the collected particles were characterized for morphology, elemental composition, nanostructure, and reactivity using scanning electron microscopy/high resolution transmission electron microscopy/energy dispersive spectroscopy, and thermogravimetric analysis. In order to quantify the nanostructure of the particles and identify prevalent sub-structures, a novel image analysis framework was used. It was found that the process temperature, affected both by λ and the load of the gasifier, had a significant influence on the particle formation processes. At low temperature (1060 °C), the formed soot particles seemed to be resistant to the oxidation process; however, when the oxidation process started at 1119 °C, the internal burning of the more reactive particle core began. A further increase in temperature (> 1313 °C) lead to the oxidation of the less reactive particle shell. When the shell finally collapsed due to severe oxidation, the original soot particle shape and nanostructure also disappeared and the resulting particle could not be considered as a soot anymore. Instead, the particle shape and nanostructure at the highest temperatures (> 1430 °C) were a function of the inorganic content and of the inorganic elements the individual particle consisted of. All of these effects together lead to the soot particles in the real gasifier environment having less and less ordered nanostructure and higher and higher reactivity as the temperature increased; i.e., they followed the opposite trend of what is observed during laboratory-scale studies with fuels not containing any ash-forming elements and where the temperature was not controlled by λ.
|
|
| 22. |
- Cantatore, Valentina, 1986, et al.
(författare)
-
Towards multifunctional coating in the boron-doped graphene/copper system
- 2017
-
Ingår i: Carbon. - : Elsevier BV. - 0008-6223. ; 115, s. 375-379
-
Tidskriftsartikel (refereegranskat)abstract
- A route to achieve multi-functional graphene coating is explored. Chemical bonding between copper substrate and coating results if the graphene is a priori boron doped. After pair-wise binding of boron sites to the Cu(111) surface, co-existence of pseudo-gap property in the graphene subsystem and a metallic density of states in the Cu subsystem at the common Fermi energy emerges. Apparently a paradox is that the two subsystems preserve and even recover their individual integrities upon formation of surface chemical bonds. Sensor capabilities are inferred. Employing pyridine as test molecule, conditioned ability of a nucleophile to offer competitive dative bonding, with the sub-strate, for boron sites is demonstrated. It is shown to occur for the case of half coverage and for adsorption to boron atoms originally bound to the on-top site on Cu(111). The ability of complementary boron sites to compensate for loss of binding between on-top site and boron, resulting from said bonding to the incoming nucleophile, is emphasized. Multifunctional substrate-coating system for catalysis as well as enhanced sensitization is inferred.
|
|
| 23. |
- Mukesh, Chandrakant, et al.
(författare)
-
Production of C-14 Levulinate Ester from Glucose Fermentation Liquors Catalyzed by Acidic Ionic Liquids in a Solvent-Free Self-Biphasic System
- 2020
-
Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 5:10, s. 4828-4835
-
Tidskriftsartikel (refereegranskat)abstract
- Herein, we present the C-14 levulinate ester of 2,3-butanediol as the product of sugar fermentation liquors. The designed Brønsted acidic ionic liquid (BAIL) catalysts enable self-induced phase separation with ester products, and the role of anions has been investigated. Esterification reactions were carried out by 2,3-butanediol (2,3-BDO) and levulinic acid in solvent-free media and low temperatures (60–105 °C). For comparison, sulfuric acid, amberlite IR-120, and sulfonic acid-functionalized pyridinium ionic liquids with different anions were utilized as a catalyst upon esterification reaction. The diester product, namely, butane-2,3-diyl bis(4-oxopentanoate), was formed with a good yield (85%) and selectivity (85%) after complete conversion of 2,3-BDO in 24 h at 80 °C. The low yield (8%) of the monoester was observed. The monoester and diester were separated by a liquid–liquid extraction method. The ester products were characterized by various instrumental techniques such as 1H and 13C NMR, GC–FID, LC–MS, and FT-IR spectroscopy. The Hammett acidity functions of BAILs were determined from UV–vis spectroscopy. The catalyst was successfully recycled and reused in the processes. The spent BAILs were reused in six consecutive cycles with only a ∼7% diminished diester yield and selectivity. The produced levulinate ester will be useful as biofuel additives, solvents, plasticizers, and other applications.
|
|
| 24. |
- Du, Chengjun, 1985
(författare)
-
Studies on Diesel sprays under non-reacting and reacting conditions
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Methods for reducing engine-out emissions are urgently needed to mitigate climate change and air pollution. In diesel engines, the quality of fuel-air mixing and the subsequent combustion process strongly affect fuel efficiency and engine-out emissions. However, fuel-air mixing, the subsequent combustion processes, and their dependence on the operating conditions are not yet fully understood. This thesis aims to address this deficiency by analyzing the effects of various orifice geometries and high injection pressures on the characteristics of diesel sprays.The thesis briefly reviews the fundamental physics governing the flow of pressurized fuel through the internal nozzle of a diesel injector, the subsequent formation of the liquid and vapor spray, and the turbulent diffusion combustion processes. The experimental work presented in this thesis can be divided into three main parts. The first focuses on the effects of geometry-induced cavitation on the liquid/vapor phase spray and injection rate evaluation. To this end, a light absorption and scattering technique (LAS) was used to measure the distributions of liquid and vapor sprays formed using nozzles with various geometries. It was found that the vaporization of the diesel spray was controlled by turbulent air mixing. The effects of geometry-induced cavitation on the spray properties were mainly due to differences in the fuel mass flow rate, spray momentum and spreading angle. In addition, the injection rates of cavitating and non-cavitating nozzles were evaluated using the momentum flux measurement method. It was found that failure to account for cavitation caused the injection rate to be overestimated for the cavitating nozzle but not for the non-cavitating nozzle.The second part of the experimental campaign investigates the effect of the injection pressure and nozzle geometry on soot formation and oxidation. A two-dimensional laser extinction method was used to measure time-resolved soot concentrations and soot volume fractions; OH* chemiluminescence imaging was used to measure the lift-off length and measure the distributions of the OH radicals qualitatively; soot luminosity images were used to identify the sooting area in the soot shadowgraph images. It was found that the equivalence ratio in the jet center at the lift-off length (ϕ_cl), which is influenced by the operating conditions, played a critical role in soot formation. Reductions in ϕ_cl thickened the OH zone in the upstream region of the jet, reducing the volume corresponding to the maximum soot volume fraction. The expansion of the OH zone also helped reduce the sooting zone’s width. However, under high sooting conditions (e.g. ϕ_cl>3.5), the sooting zone width in the downstream jet was independent of ϕ_cl. The third part of the thesis investigates combusting and non-combusting sprays formed from different blends of ethanol with diesel fuel. Using 0%-20% ethanol blended with diesel fuels, liquid/vapor phase spray images were captured, the ignition delay was measured, the lift-off length was measured, and natural soot luminosity images were captured. It was found that the differences in the fuels’ composition did not significantly affect the liquid/vapor phase sprays. However, as the ethanol content of the fuel was increased from 0% to 20%, the lift-off length increased and the detectable soot luminescence decreased. This indicates that soot formation declines as the fuel’s ethanol content increases.
|
|
| 25. |
- Purnomo, Victor, 1992
(författare)
-
Behavior of iron-based oxygen carriers at deep reduction states
- 2024
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Oxygen carriers have an important role as bed materials in both common circulating fluidized bed combustion unit (also known as oxygen-carrier-aided combustion, OCAC) and in various chemical looping processes. Contrary to conventional bed materials, e.g., sand, oxygen carriers are capable of transferring both oxygen and heat. This makes it possible to produce nitrogen-free product gas streams (in the case of chemical looping processes) and achieve a higher fuel conversion. Having been studied for almost three decades, various oxygen carriers show their own pros and cons depending on the processes for which they are intended to be used. Most of the published studies before this doctoral thesis focused on the reactivity and utilization of oxygen carriers in chemical looping combustion (CLC), where a complete fuel conversion is always desired. Nevertheless, this is not the case in, for example, chemical looping gasification, reforming, and water splitting, where only partial fuel oxidation is necessary, and the produced flue gases are the desired products. In such processes, the oxygen carriers can be exposed to a higher reduction degree than it would be in CLC or OCAC. This warrants further investigations into the deep reduction states of relevant oxygen carriers, which are expected to encounter inevitable performance issues under such a harsh environment. In this thesis, some aspects related to the physical performance and properties of various iron-based oxygen carriers in the occurrence of deep reduction states are examined and presented. The first part of the thesis focuses on the fluidization performance, attrition resistance, and particle size and shape analysis. This part is important mainly for assessing material stability. Iron-based oxygen carriers typically tend to encounter bed defludization at a high degree of reduction. The outward migration of iron into the particle surface, which typically creates a FeO/Fe layer, likely causes defludization. Furthermore, the oxidation state of oxygen carriers does affect the attrition resistance of iron oxygen carriers to varying extents. The results indicate that the presence of Fe-Ti and Fe-Si combinations contribute to a generally stable and low attrition rate, while an Fe-Ca system exhibits a decreasing attrition rate. In addition, the influence of exposure to redox cycles and oxidation degree on the size and shape of oxygen carrier particles seems to be minimal. The oxygen carrier particles generally have a high sphericity but are slightly elongated. Reactivity and fuel conversion are the other focuses of this thesis. These have main implications for engineering design but also for material screening. The apparent kinetic study of oxygen carrier performed in this thesis demonstrates that the changing grain size (CGS) model is applicable to predict the reactivity of three iron oxygen carriers in the presence of CO, H2, and CH4. This applies even at lower oxidation degrees (3 – 5 wt.% reduction), where the reactivity of oxygen carriers has generally decreased. Finally, the gasification rate of pine forest residue char remains at similar levels when using either ilmenite or iron sand as the oxygen carrier.
|
|
