| 1. |
- 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.
|
|
| 2. |
|
|
| 3. |
- Bylin, Susanne, 1982
(författare)
-
Mechanisms of Biopolymer Solvation: Development of a two-component ionic liquid solvent system
- 2014
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ionic liquids are of potential interest in the processing of lignocellulosic biomass, and/or its components, for the purpose of producing renewable and value-added biomaterials. An understanding of how solvation can be achieved and the way in which the feedstock biopolymers are affected, however, needs to be gained prior to a viable implementation. In this thesis, the solvation of the wood biopolymers cellulose, xylan and lignin in the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate (EMIMAc) in a novel combination with the second system component 1-methylimidazole (MIM) have been investigated:The solvation of dissolving pulp, beech xylan and LignoBoost lignin model materials, was studied using FBRM (focused beam reflectance measurements) particle characterization in combination with microscopic analysis (cellulose and xylan), determination of molecular weights (xylan and lignin) and 13C- and 31P-NMR (nuclear magnetic resonance spectroscopy) of lignin.It was concluded that the most efficient solvation of cellulose and xylan occurred using 3-4% and 9% IL (n/n anhydroglucose units and n/n anhydroxylose Units), respectively, while polymer integrity was maintained. Cellulose solvation was found to be greatly dependent on the IL to AGU ratio whereas xylan solvation varied greatly with temperature. Moreover, a theoretical model was developed for the solvation of cellulose in the present system. The solvation of lignin was achieved at ~20% lignin loading (w/w), in any combination of MIM/EMIMAc. Regeneration of lignin resulted in two sets of fractions; one exhibiting a general and higher apparent molecular weight (Mw) along with an enrichment of condensed/aliphatic ether linkages and aliphatic hydroxyls, and the other exhibiting a lower apparent Mw and an enrichment of carboxylic and phenolic groups. The knowledge of biopolymer solvation gained in the present solvent system provides future opportunities of tuning extraction and/or fractionation processes to suite the specifications of a particular biomass-derived product.
|
|
| 4. |
- Erkfeldt, Sara U, 1974
(författare)
-
Lean NOx reduction by alternative fuels - with focus on catalysts for dimethyl ether
- 2011
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There is an increased demand for diesel engines running on non-fossil fuels such as dimethyl ether (DME), biodiesel and synthetic diesel. DME is a promising alternative fuel with potential for high energy efficiency and low CO2 emissions. However, during all high temperature combustion NOx is formed, which may require exhaust aftertreatment. Two technologies for NOx reduction under lean conditions utilizing the fuel as reducing agent are the lean NOx catalyst (LNC) and the lean NOx adsorber (LNA).Lean NOx reduction with alternative fuels was investigated in a flow reactor and showed that DME was an efficient reducing agent for NOx over a BaO-based LNA, but not over a Cu-ZSM-5-based LNC. Also methanol did not reduce NOx over Cu-ZSM-5, whereas higher ethers and alcohols did. Despite being more oxidised than DME, ethylene glycol reduced NOx. It was concluded that a C–C bond is required in hydrocarbon-based reducing agents for lean NOx reduction over Cu-ZSM-5. A comparison of biodiesel, synthetic diesel, conventional diesel and octane as reducing agents, showed that Cu-ZSM-5 reduced NOx at a lower temperature than Ag/Al2O3, which was more sensitive to the reductant used. RME gave the lowest, and octane the highest, NOx conversion over both catalysts. The oxygenated hydrocarbon triethylene glycol dimethyl ether (triglyme) efficiently reduced NOx over Ag/Al2O3, but not over Cu-ZSM-5. Adding a low amount of triglyme to propene as reducing agents drastically promoted the NOx conversion over Ag/Al2O3 at low temperature.A series of In2O3-, Ga2O3- or B2O3-promoted γ-Al2O3 catalysts were investigated for lean NOx reduction with DME. B2O3/Al2O3 and Ga2O3/Al2O3 catalysts gave a temperature window similar to Al2O3, but with higher NOx conversion. In2O3/Al2O3 showed the highest NOx conversion at low temperature, whereas pure In2O3 was inactive for NOx reduction with DME. It was concluded that a close interaction between In2O3 and Al2O3 is essential for the promoting effect of In2O3 at low temperature. In-situ DRIFT spectroscopy showed that the differences in activity of In2O3/Al2O3, pure Al2O3 and pure In2O3 correlated to differences in the amounts of surface species that are possible intermediates of the reaction.
|
|
| 5. |
- Huang, Chen, 1981, et al.
(författare)
-
Chemical model of gasoline-ethanol blends for internal combustion engine applications
- 2010
-
Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627.
-
Tidskriftsartikel (refereegranskat)abstract
- A semi-detailed chemical mechanism for combustion of gasoline-ethanol blends, which is based on sub-mechanisms of gasoline surrogate and for ethanol is developed and validated aiming at CFD engine modeling. The gasoline surrogate is composed of iso-octane, toluene, and n-heptane in volumetric proportions of 55%:35%:10%, respectively. In this way, the hydrogen-carbon atomic ratio H/C, which is around 1.87 for real gasoline, is accurately reproduced as well as a mixture equivalence ratio that is important for Gasoline Direct Injection engine applications. The integrated mechanism for gasoline-ethanol blends includes 120 species participating in 677 reactions. The mechanism is tested against experimental data on ignition delay times and laminar flame speeds, obtained for various n-heptane/iso-octane/toluene/ethanol-air mixtures under various equivalence ratios, initial temperatures, and pressures. Chemical, thermodynamic and transport properties used in the calculations are discussed.
|
|
| 6. |
- Lind, Fredrik, 1978, et al.
(författare)
-
Ilmenite and Nickel as Catalysts for Upgrading of Raw Gas Derived from Biomass Gasification
- 2013
-
Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 27:2, s. 997-1007
-
Tidskriftsartikel (refereegranskat)abstract
- Two metal oxides, naturally occurring ilmenite (iron titanium oxide) and manufactured nickel oxide supported on an α-Al2O3 matrix (NiO/AL2O3), were compared as catalysts for secondary biomass gas upgrading. The experiments were conducted in a Chemical-Looping Reforming (CLR) reactor, which combines biomass gas upgrading with continuous regeneration of coke deposits. The CLR system was fed with a tar-rich producer gas from the Chalmers 2–4 MW biomass gasifier, and the possibilities to reduce the tar fraction and to increase the yield of hydrogen were evaluated for temperatures between 700°C and 880°C. A system-wide molar balance was established, to enable calculations of tar removal efficiency on a mass basis; these results were further compared with those for the more widely used tar-to-reformed gas ratio, yielding tar concentrations in units of gtar/Nm3gas. Both materials exhibited activity with respect to tar decomposition and increased the yield of hydrogen. In addition, both tar removal and hydrogen production were increased with increases in temperature. All the phenolic compounds and a large proportion of the one-ring branched tars were decomposed at 800ºC by the two catalysts, despite the fact that the tar load in the raw gas was as high as 30 gtar/Nm3gas. Results from the mole balance showed that it is important to specify on what basis the tar removal efficiency is calculated. The tar removal efficiency was calculated to 95% for the Ni/Al2O3 catalyst at 880°C and to 60% for the ilmenite catalyst at 850°C on tar-to-reformed gas basis. When the produced permanent gases were removed from the reformed gas the same calculations yielded the tar removal efficiency of 86% and 42% respectively. The testing of serial samples of the effluent stream from the regeneration reactor for carbon oxides showed that coke was removed from the catalyst, and no deactivation by coke deposits was detected during the 8 hours of operation of the CLR reactor.
|
|
| 7. |
|
|
| 8. |
- Ziesig, Rufus, 1984, et al.
(författare)
-
Production of a pure lignin product part 1, distribution and removal of inorganics from Eucalyptus globulus kraft lignin
- 2014
-
Ingår i: Tappi Journal. - 0734-1415. ; 13:3, s. 65-72
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Future high value lignin-based products, such as carbon fibers, are expected to require a lignin raw material essentially free from inorganic impurities. Lignin of low inorganic content can be separated from kraft black liquor by the LignoBoost process. This laboratory scale study focuses on the effect of different process parameters, such as final precipitation pH and re-suspension pH, on the content of inorganic impurities in the LignoBoost lignin. Black liquor from pulping of Eucalyptus globulus was used in this study. Specific attention has been paid to the distribution of the inorganics Na, K, Ca, Al, Mn, Mg, Si and Fe. It was found that by lowering the re-suspension pH and wash pH to 1.5 the ash content could be greatly reduced, primarily due to the dissolution of Ca-oxalate particles present in the lignin. By slightly increasing the retention time in the re-suspension stage, the content of Mg, Al, Mn, Si and Fe could be reduced by approximately 50 %. Repeated re-suspension followed by washing resulted in a lignin with very low Na and K content. The total amount of inorganics could be reduced from 5.7 g/kg lignin to 0.6 g/kg lignin by combining a low re-suspension/wash pH and a repeated re-suspension and wash.
|
|
| 9. |
- Ziesig, Rufus, 1984
(författare)
-
Towards a pure kraft lignin
- 2014
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The most widely used production method for paper pulp in the world is kraft pulping. In chemical pulping the polymer, lignin, which binds the wood fibres together, is partly depolymerized. This allows the wood fibres to be separated from each other. Lignin and other organic by-products are dissolved in the black liquor and is subsequently combusted in the pulp mills recovery boiler to regenerate chemicals and recover the energy. Many kraft pulp mills have an energy surplus. This surplus means that parts of the organic by-products, such as lignin, can be separated and sold to generate an additional revenue stream for the pulp mill. Lignin with low inorganic content can today be separated from the kraft pulp mill with the LignoBoost process. This lignin can be used as solid fuel in e.g. lime kilns. Another alternative is to utilize the separated lignin as a raw material for high value materials such as carbon fibres. Such applications require a lignin raw material with even lower content of inorganic impurities than what can be produced today.This study focuses on further development of the LignoBoost process in order to facilitate a reduced content of the elements Na, K, Al, Ba, Ca, Fe, Mg, Mn and Si in the separated lignin. In this work parameters such as black liquor composition, residence time and pH in re-suspension were evaluated. Industrial black liquors were used in this study. This study confirms the previous findings on the possibilities to remove Na by washing, introduction of an extra wash stage resulted in 80-95% lower content of both Na and K. Other elements have in earlier studies been found to be more difficult to remove by washing. These findings were confirmed as an extra wash stage only marginally affected the content of the other studied elements, compared to a normal LignoBoost lignin. By use of SEM-EDS, inorganic particles, such as Ca-oxalate, were observed in washed lignin. This partially explains why some inorganics are harder to remove from lignin than others. The pH in the re-suspension stage did not affect the content of Al, Fe, Mg, Mn and Si in the lignin. However, the Ca content was affected in samples where Ca-oxalate occurred in large amounts, the solubility of this salt is pH dependent at pH
|
|
| 10. |
- Abrahamsson, Per, 1985, et al.
(författare)
-
CONTINUUM MODELING OF PARTICLE FLOWS IN HIGH SHEAR GRANULATION
- 2013
-
Ingår i: 6th International Granulation Workshop.
-
Konferensbidrag (refereegranskat)abstract
- High shear granulation (HSG) is a common process in the pharmaceutical industry. A better understanding of the flow conditions of powders and granulates in large-scale HSG equipment is crucial for constructing predictive models. The staggering amount of particles in the process makes the use of continuum flow models highly attractive. This article discusses the possibilities and problems in using continuum modelling in HSG systems and evaluates some of the available modelling approaches. We examine several dense granular flow models studying both the underlying theory and how they perform in practice. The studied models are the frictional model by Shaeffer [1], modifications to the transport coefficients that describe the solid phase stresses similar to those used in Khain and Meerson [2], and the framework developed by Jop et.al. [3] using a depth-averaged flow model for constant solid volume fraction flows.The model by Shaeffer has previously been used with the conclusion that the solid phase stresses are underestimated [4]. We show theoretically and in practice that this approach is not appropriate due to the strong resolution dependence of the model. The approach taken by Khain and Meerson, among others, to try to modify expressions from rapid granular flow to also be valid in the dense region is attractive from a theoretical point of view. Making use of the rigorous framework of kinetic theory, the applicability of a number of such models to HSG has been evaluated. The modelling framework developed by Jop et.al was used in disc impeller HSG equipment. The results show that the model can well predict the behaviour of the solid-phase viscosity of the dense granular flow. The model is nevertheless restricted to constant volume fraction flows and needs to be expanded to include a varying volume fraction. We conclude in this paper that continuum modelling of HSG has a promising outlook but there is a need to develop better models for the dense regions of the flow. We also give and evaluate some of the options available for treating these regions.
|
|
