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- Erlich, Catharina
(författare)
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Comparative study of residue pellets from cane sugar and palm-oil industries with commercial wood pellets, applied in downdraft gasification
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- While biomass utilization for energy conversion in the industrialized nations is being largely developed, highly efficient and environmentally friendly, many tropical countries still use biomass at low efficiencies and high emission levels. The main reasons for these gaps are both political and technological: the energy markets are different, the Gross National Product (GDP) differs widely, and the feedstock differs in form and conversion behaviour. By implementing newer technologies adapted for tropical biomass feedstock, there would be a large potential in these countries for increased energy services since access to modern energy still is an essential step for improving the GDP for a country. Two dominant and tropically placed industries available for energy improvements are the cane sugar and palm-oil industries, which both produce an abundant amount of biomass residues. One step towards enhanced utilization of the residues, which would not require large investment costs in the power plant section nor in the processes of these industries, would be to install a pelletizing unit in the industry area to make fuel out of the excess residues for sale to the nearby villages. The pellets could be used both for cooking/heating and for small-scale power generation in a gasification-IC engine plant. The overall objective of this study is to experimentally evaluate the biomass residues in pellet form from the cane sugar and palm oil industries during conversion to useful energy in small-scale systems. The thesis is built upon five publications which include experimental analysis on flaming pyrolysis and rapid heating of pellets (paper I), pyrolysis in oxygen-free atmosphere and slow heating with subsequent steam gasification (paper II), global pelletizing data such as relative energy consumption, temperature levels, particle size and moisture content for successful pelletizing process (paper III), downdraft gasification evaluation including reactor temperature distribution, gas composition, cold-gas efficiency and packed-bed mechanics (paper IV) and a numerical model including the overall system efficiency for residue-to-electric power based in a small-scale gasifier system (paper V).The single-pellet studies revealed that pyrolysis in reducing atmosphere is to prefer compared to flaming pyrolysis in oxidizing environment with regards to the char quality. The studies also showed favourable thermochemical and mechanical behaviour for smaller size pellets (Ø6- Ø8mm) compared to larger size ones (Ø12 mm). Therefore, a downdraft gasifier of closed constricted type was designed for real gasification tests of the residue pellets of sizes Ø6- Ø8mm. These tests showed that all the studied pellet sorts could be used in one and the same gasifier, resulting in different reactor temperature distributions and gas compositions with lower heating values in the range of 4.1-5.4 MJ/m3n dry gas. The reactor bed dynamics showed to be dependent both on the fuel reactivity and the size, with less pressure drop for larger size pellets with lower reactivity. The pelletizing process itself revealed that the selected residues all needed higher moisture content and smaller particle size than recommended for wood for successful pelletizing. The relative electric energy consumption was lower when producing larger size pellets Ø8 mm than smaller ones (Ø6 mm) of same material. For untreated wet empty-fruit bunch (EFB) a stand-alone power plant with integrated EFB pre-treatment and gasification could generate 380 kWh of net electricity per ton of EFB at a “well-to-wheel” efficiency of 15%.
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| 2. |
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| 3. |
- Fransson, Carl-Magnus, 1976, et al.
(författare)
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Non-conservative robust control: Optimized and constrained sensitivity functions
- 2009
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Ingår i: IEEE Transactions on Control Systems Technology. - 1063-6536 .- 1558-0865. ; 17:2, s. 298-308
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Tidskriftsartikel (refereegranskat)abstract
- An automated procedure for optimization of proportional–integral–derivative (PID)-type controller parametersfor single-input, single-output (SISO) plants with explicit modeluncertainty is presented. Robustness to the uncertainties is guaranteedby the use of Horowitz–Sidi bounds, which are used asconstraints when low-frequency performance is optimized in anonconvex but smooth optimization problem. In the optimization(and hence the parameter tuning), separate criteria are formulatedfor low-, mid-, and high-frequency (HF) closed-loop properties.The tradeoff between stability margins, control signals, HF robustness,and low-frequency performance is clarified, and the finalparameter choice is facilitated. We use a combination of globaland local optimization algorithms in the TOMLAB optimizationenvironment and obtain robust convergence without relying ongood initial estimates for the controller parameters. The methodis applied to a controller structure comparison for a plant with anuncertain mechanical resonance and a plant with uncertain timedelay and time constants. For a given control activity, stabilitymargin, and HF robustness, it is shown that a PID controller witha second-order filter and an controller based on loop-shapingachieve approximately the same low-frequency performance.
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| 6. |
- Mayorca, María Angélica, 1983-, et al.
(författare)
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Effect of scaling of blade row sectors on the prediction of aerodynamic forcing in a highly-loaded transonic compressor stage
- 2009
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Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO 2009, VOL 6, PTS A AND B. - 9780791848876 ; , s. 535-546
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Konferensbidrag (refereegranskat)abstract
- An investigation of the sensitivity of a geometrical scaling technique on the blade forcing prediction and mode excitability has been performed. A stage of a transonic compressor is employed as test object. A scaling ratio is defined which indicates the amount of scaling from the original geometry. Different scaling ratios are selected and 3D Navier Stokes unsteady calculations completed for each scaled configuration. A full annulus calculation (non-scaled) is performed serving as reference. The quantity of interest is the generalized force, which gives a direct indication of the mode excitability. In order to capture both up- and downstream excitation effects the mode excitability has been assessed on both rotor and stator blades. The results show that first harmonic excitation can be predicted well for both up- and downstream excitation using moderate amount of scaling. On the other hand, the predictions of second harmonic quantities do show a higher sensitivity to scaling for the investigated test case.
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| 7. |
- Mayorca, María Angélica, 1983-, et al.
(författare)
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Numerical tool for prediction of aeromechanical phenomena in gas turbines
- 2009
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Ingår i: 19th ISABE Conference. - Montreal : American Institute of Aeronautics and Astronautics Inc.. ; , s. 1-11
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Konferensbidrag (refereegranskat)abstract
- A numerical tool for aeromechanic design is presented. The output of the tool is the fatigue risk of the critical blade obtained by the Haigh diagram, and stability curves for the stability analyses. The tool integrates results from commercial Computational Fluid Dynamics (CFD) and Finite Element (FE) solvers. It uses a Reduced Order Modeling (ROM) technique in order to account for mistuning effects in an efficient way. The description of the numerical tool and an overview of typical results are presented in this paper. The applicability of the tool in the industrial design process is discussed as well as the outlook of the targeted capabilities.
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| 8. |
- Salomón Popa, Marianne, 1976-, et al.
(författare)
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Energy Potential of Coconut and Palm Oil Residues
- 2009
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Ingår i: 5th Dubrovnik Conference on Sustainable Development of Energy, Water and Environment Systems. - Dubrovnik : Faculty of Mechanical Engineering and Naval Architecture, Zagreb. - 9789536313976
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Konferensbidrag (refereegranskat)abstract
- Agricultural residues continue to attract interest for energy recovery purposes as a renewable, CO2 neutral and increasingly cost competitive alternative to traditional fossil fuels. The possibility of trigeneration in already established industries such palm oil mills and coconut processing plants is very attractive especially when residues that otherwise represent a disposal problem can be utilized efficiently. The use of these residues in rural areas or in small islands could certainly represent an advantage as the use of expensive fossil fuels represents an additional burden to foster development. Different technical scenarios for the production of electricity, process heat and biodiesel are analyzed using these residues Environmental aspects are also included in this analysis. Studies were done considering certain scenarios to evaluate the feasibility of using these residues for energy purposes. Residues were considered to be combusted directly in boilers and steam turbines were used as prime movers to generate electricity. Biodiesel is produced by transesterification of palm oil/coconut oil. The required process heat for palm oil or coconut oil processing is supplied by the residues as well as the steam required for biodiesel production. The advantage is that biodiesel is a more flexible and easy-to-distribute fuel that can be used for power generation or for transportation. The results shown that palm oil mills/coconut processing industries can be independent of fossil fuels. Furthermore, they can contribute positively to the energy balance of the communities by helping reduce the dependence on fossil fuels and reducing at the same time greenhouse gas emissions.
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| 10. |
- Wang, Shurong, et al.
(författare)
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Comparison of the pyrolysis behavior of lignins from different tree species
- 2009
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Ingår i: Biotechnology Advances. - : Elsevier BV. - 0734-9750 .- 1873-1899. ; 27:5, s. 562-567
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Tidskriftsartikel (refereegranskat)abstract
- Despite the increasing importance of biomass pyrolysis. little is known about the pyrolysis behavior of lignin-one of the main components of biomass-due to its structural complexity and the difficulty in its isolation. In the present study, we extracted lignins from Manchurian ash (Fraxinus mandschurica) and Mongolian Scots pine (Pinus sylvestris var. mongolica) using the Bjorkman procedure, which has little effect on the structure of lignin. Fourier transform infrared (FTIR) spectrometry was used to characterize the microstructure of the Bjorkman lignins, i.e., milled wood lignins (MWLs), from the different tree species. The pyrolysis characteristics of MWLs were investigated using a thermogravimetric analyzer, and the release of the main volatile and gaseous products of pyrolysis were detected by FTIR spectroscopy. During the pyrolysis process, MWLs underwent thermodegradation over a wide temperature range. Manchurian ash MWL showed a much higher thermal degradation rate than Mongolian Scots pine MWL in the temperature range from 290-430 degrees C. High residue yields were achieved at 37 wt.% for Mongolian Scots pine MWL and 26 wt.% for Manchurian ash MWL. In order to further investigate the mechanisms of lignin pyrolysis, we also analyzed the FTIR profiles for the main pyrolysis products (CO2, CO, methane, methanol, phenols and formaldehyde) and investigated the variation in pyrolysis products between the different MWLs.
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