| 1. |
- Cui, Xiaoqi, et al.
(författare)
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Combustion and emissions in a light-duty diesel engine using diesel-water emulsion and diesel-ethanol blends
- 2009
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; , s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the investigation presented here was to compare the effects of fuel composition on combustion parameters, emissions and fuel consumption in engine tests and simulations with five fuels: a Diesel-water emulsion, a Diesel-ethanol blend, a Diesel-ethanol blend with EHN (cetane number improver), a Fischer-Tropsch Diesel and an ultra-low sulfur content Diesel. The engine used in the experiments was a light duty, single cylinder, direct injection, common rail Diesel engine equipped with a cylinder head and piston from a Volvo NED5 engine. In tests with each fuel the engine was operated at two load points (3 bar IMEP and 10 bar IMEP), and a pilot-main fuel injection strategy was applied under both load conditions. Data were also obtained from 3-D CFD simulations, using the KIVA code, to compare to the experimental results and to further analyze the effects of water and ethanol on combustion. The experimental data indicated that the lower aromatic content of Fischer-Tropsch Diesel fuel resulted in reduced soot emissions compared to conventional Diesel. Use of Fischer-Tropsch Diesel also gave lower NOx emissions. The Diesel-ethanol blend gave a large reduction in soot emissions, but higher NOx emissions than the Diesel-water emulsion. The lower heating value of the Diesel-water emulsion resulted in increased fuel consumption in comparison to the Diesel-ethanol blend and Diesel. The addition of the cetane number improver (EHN) to the Diesel-ethanol blend further reduced NOx emissions.
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| 2. |
- HANDA, PAUL, 1980, et al.
(författare)
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The Sonogashira reaction catalyzed by palladium leached from ordered mesoporous carbon
- 2009
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Ingår i: Microporous and Mesoporous Materials. - 1387-1811. ; 117, s. 126-135
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Tidskriftsartikel (refereegranskat)abstract
- The Sonogashira carbon–carbon coupling reaction between iodobenzene and phenylacetylene was performed using palladium nanoparticles formed directly inside the pores of ordered mesoporous carbon as catalyst. The nanoparticles were generated by two methods, a phase-transfer method and a microemulsion procedure. The coupling reaction was performed using different bases and varying amounts of palladium and the yields and reaction profiles were determined by 1H NMR. Recycling experiments were also performed and the recyclability was found to be very dependent on the choice of base. From the so-called Maitlis’ filtration test it was shown that soluble palladium species were present in solution and these were found to be active in catalyzing the coupling reaction. The degree of leaching depended on the type of base used. The results hint at the Sonogashira reaction being an example of homogeneous rather than heterogeneous catalysis, as has recently been suggested by other authors as well.
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| 3. |
- Heyne, Stefan, 1979, et al.
(författare)
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Production of synthetic natural gas from biomass - Process integrated drying
- 2009
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Ingår i: 22nd International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems. - 2175-5426. ; , s. 1877-1886
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Konferensbidrag (refereegranskat)abstract
- Opportunities for process integrated feedstock drying in connection with the production of synthetic natural gas (SNG) from wet biomass via indirect gasification are investigated in this study. Drying is a very energy-intensive process step – corresponding to about 10% of the dry fuel lower heating value for woody biomass. Process integrated drying offers opportunities for reducing the external energy supply necessary for drying, thereby improving the overall process efficiency. Simulation models for three drying technology options – air, steam and flue gas drying – have been developed using the flowsheeting software tool ASPEN Plus. The influence of basic operation parameters on the performance of the different drying configurations is investigated using sensitivity analysis. Based on a proposed SNG production process that is built as an extension of a fluidized bed boiler for a combined heat and power plant, the potential for heat integrated drying is assessed using pinch analysis in combination with the developed drying models. The biomass – 100 MWth input for both combustion and gasification, respectively - needs to be dried from 50 to 10 weight-% moisture content prior to combustion/gasification. It is shown that it is not possible to cover all feedstock drying needs for the process by internal heat recovery. Steam drying offers the highest potential for heat integration with the proposed SNG process, making it possible to cover 47.7 % of the necessary total dry fuel supply to both combustion and gasification. However, not all process heat used in the steam dryer can be recovered, increasing the external heat need to the SNG process at a lower temperature level. Nevertheless, substantial savings are possible making use of integrated drying within the SNG production process compared to stand-alone drying.
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| 4. |
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| 5. |
- Nyström, Anna, 1974
(författare)
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Modeling and Simulation of a Semi-batch Reactor
- 2007
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Ingår i: The 48th Scandinavian Conference on Simulation and Modeling (SIMS 2007), 30-31 October, 2007, Göteborg (Särö), Sweden. - 1650-3740. ; 2007, s. 173-182
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The operation of an industrial semi-batch reactor, in which the bulk chemical EHEC, ethyl hydroxyethyl cellulose, is produced, is studied and simulated. In the reactor a strongly exothermic polymerization reaction takes place followed by a slightly exothermic reaction, and we want to minimize the duration of the operation of the process. Various operational as well as quality and safety related constraints have to be met during the batch. The complete process model, derived from measurements, first principles, and reasoning about effects on molecular level, is stated. The model includes heat and mass balances of the reactor, a pressure model, models of PID controllers, the jacket and the condenser. Technical limitations, for instance maximal and minimal jacket temperature changes due to limitations in the heat exchanger, have been modeled as constraints. The equations have been implemented in SIMULINK, MATLAB and the model predicts the process variables rather well over time. During the first reaction, the model is not able to reproduce the jacket temperature to the desired accuracy, but the other variables have acceptable predictions. An optimization problem is formulated, wherein the total batch time is minimized under the constraints of the differential algebraic equation system and other constraints originating from the process, for instance limited pump capabilities. As a first step in optimizing the operation of the process, a series of simulations has been performed in order to decrease the total batch time. It is concluded that a 10 % shorter batch time than today is possible if the quality is discarded, and a 5 % shorter batch time can be reached while using the existing requirements for the quality.
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| 6. |
- Reis, Pedro, 1978, et al.
(författare)
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Lipases at interfaces
- 2009
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Ingår i: Advances in Colloid and Interface Science. - 0001-8686. ; 147-148, s. 237-250
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Tidskriftsartikel (refereegranskat)
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| 7. |
- Ericsson, Per, et al.
(författare)
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Characterization of particulate emissions and methodology for oxidation of particulates from non-diesel combustion systems
- 2008
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Ingår i: SAE Technical Paper. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
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Tidskriftsartikel (refereegranskat)abstract
- Tailpipe particulate emissions, i.e., particle number, size distribution and total mass, from a series of four-cylinder engines with 2L displacement and power output of approximately 150 hp have been measured. The engines were in their respective vehicle installation, all midsize vehicles from various manufacturers, and represented different combustion concepts, i.e., port- and direct-injected vehicles and E5 and E85 fuels. The results are compared to post-Euro V emission standards for gasoline and biofuels using diesel as reference. The results show that the type of combustion and fuel significantly affect the particulate formation. In general, direct-injected engines show high particle numbers and mass compared to port-injected engines. The particulate number and total mass can be reduced by using biofuels, e.g., ethanol mixes, instead of gasoline. Moreover, an experimental procedure and setup facilitating precise studies of oxidation of particulates in realistic filter structures by well-controlled gas flow (composition and temperature) and sample (particulate load and temperature) conditions has been developed. The results from this method have been verified by using commercial soot as reference.
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| 8. |
- Mahmoudkhani, Maryam, 1971, et al.
(författare)
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Low energy sodium hydroxide recovery for CO2 capture from atmospheric air – Thermodynamic analysis
- 2009
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Ingår i: International Journal of Greenhouse Gas Control. - 1750-5836. ; 3:4, s. 376-384
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Tidskriftsartikel (refereegranskat)abstract
- To reduce the risks of climate change, atmospheric concentrations of greenhouse gases must be lowered.Direct capture of CO2 from ambient air, ‘‘air capture’’, might be one of the few methods capable of systematically managing dispersed emissions. The most commonly proposedmethod for air capture is a wet scrubbing technique which absorbs CO2 in an alkaline absorbent, i.e. sodium hydroxide producing an aqueous solution of sodium hydroxide and sodium carbonate. In most of the previous works it was assumed that the absorbent would be regenerated and CO2 liberated from the alkaline carbonatesolution using a lime and calcium carbonate causticization cycle. We describe a novel technique for recovering sodium hydroxide from an aqueous alkaline solution of sodium carbonate and present an end-to-end energy and exergy analysis. In the first step of the recovery process, anhydrous sodium carbonate is separated from the concentrated sodium hydroxide solution using a two-step precipitation and crystallization process. The anhydrous sodium carbonate is then causticized using sodium tri-titanate. The titanate direct causticization process has been of interest for the pulp and paper industry and has been tested at lab- and pilot-scale. In the causticization process, sodium hydroxide is regenerated and carbon dioxide is liberated as a pure stream, which is compressedfor use or disposal. The technique requires 50% less high-grade heat than conventional causticization and the maximum temperature required is reduced by at least 50 8C. This titanate cycle may allow a substantial reduction in the overall cost of direct air capture.
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| 9. |
- Perdana, Indra, 1973, et al.
(författare)
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Effect of external mass transport on permeation in a Wicke-Kallenbach cell
- 2009
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Ingår i: Chemical Engineering Research and Design. - : Elsevier BV. - 0263-8762 .- 1744-3563. ; 87:10, s. 1438-1447
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Tidskriftsartikel (refereegranskat)abstract
- Wicke-Kallenbach (WK) cells are often used for studying separation and component transport in porous material. In order to obtain important transport parameters, mathematical models are frequently developed but they generally consider the fluid phase in the WK compartments to be free of concentration gradients and thus external mass transport resistance is neglected. The present work is a detailed study of how the external transport influences permeation through porous material in a WK cell. External mass transfer effects were demonstrated experimentally and they were further studied from three-dimensional (3-D) model simulations. Film theory was applied to develop an appropriate Sherwood number correlation for the external mass transport coefficient. It was shown that the flow in the compartment and geometrical factors of the WK cell had significant influences on the permeation. It was found that introducing the proposed external mass transport correlation into a simplified one-dimensional (1-D) model was adequate to reproduce results from both the experimental data and the 3-D model.
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| 10. |
- Schwartz, W. R., et al.
(författare)
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Combustion of methane over palladium based catalysts - A study of catalytic deactivation & the use of electrochemical oxygen pumping
- 2007
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Ingår i: 5th US Combustion Meeting 2007. - : Combustion Institute. - 9781604238112 ; , s. 1787-1794
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Konferensbidrag (refereegranskat)abstract
- Methane oxidation over palladium is of interest due to its clean catalytic combustion properties, forming only carbon dioxide and water. A successful palladium based catalyst will virtually eliminate polluting by products including unburned hydrocarbons, carbon monoxide, soot, and NOx. These potential benefits have have not been realized, in part due to catalyst deactivation over time. In this study we identify a relationship between catalyst deactivation and hydroxyl formation on Pd/Al2O3 and Pd/TiO2 catalyst surfaces, using time series FTIR spectroscopy. FTIR analysis suggests that catalyst deactivation is caused by growth of surface hydroxyls at temperatures below 450°C, and that that oxygen mobility on the catalyst surface may correlate with the degree of catalytic deactivation. We also examine the use of electrochemical oxygen pumping through a yttrium stabilized zirconia (YSZ) membrane as a possible method of delivering oxygen to the methane catalytic combustion reaction and improving catalytic conversion. We observe that applying a potential across a YSZ membrane can result in moderate increases in methane conversion, and that oxygen concentration in reactant gas mixture has a dramatic effect on catalytic activity. Our study will also address electrochemical oxygen transport to determine its rate limiting impact on the methane catalytic combustion reaction.
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