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- Kilpinen, P., et al.
(författare)
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Towards a quantitative understanding of NOx and N2O emission formation in full-scale circulating fluidised bed combustors
- 2001
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Ingår i: In Proceedings of the 16th International Conference on Fluidized Bed Combustion--FBC01, held in Reno, Nevada, USA, May 13-16, 2001.
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Konferensbidrag (refereegranskat)abstract
- A mathematical tool is being developed for studying the nitrogen oxide emission formation in circulating fluidised bed combustors. The model is based on detailed homogeneous and heterogeneous chemical kinetics and a simplified, reasonable description of CFB hydrodynamics with presumed temperature distribution (Kilpinen et al, 1999a). With the model different fuels and fuel mixtures can be compared in regard to their nitrogen oxide emission formation tendency at typical CFBC conditions. In this paper the structure of the CFBC model and its submodels are shortly described in present form. The CFBC model is tested for nitrogen oxide prediction at normal air staging conditions in a 12 MW CFB with bituminous coal and wood chips as the fuel, respectively. Comparisons of modelling results with detailed gas concentration profiles measured inside the furnace are made. The relative importance of homogeneous and heterogeneous reactions on NO and N2O concentration profiles is illustrated based on a quantitative reaction rate analysis at different parts in the combustor. The importance of effects of radical removal on particle surfaces, and thus, a decreased CO burnout and, simultaneously, enhanced rates of catalytic bed/char reactions on nitrogen oxides’ destruction are discussed.
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- Kristenson, E Maria, et al.
(författare)
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Evaluation of modulators and electron-capture detectors for comprehensive two-dimensional GC of halogenated organic compounds
- 2003
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Ingår i: Journal of Chromatography A. ; 1019:1-2, s. 65-77
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Tidskriftsartikel (refereegranskat)abstract
- AbstractDifferent cryogenic and a heated GC×GC modulator(s) were evaluated and compared for the analysis of high-boiling halogenated compounds. The cryogenic modulators investigated were: (i) the longitudinally modulated cryogenic system; (ii) the liquid-nitrogen-cooled jet modulator (KT2001); (iii) a dual-jet CO2 modulator (made in-house); (iv) a semi-rotating cryogenic modulator (made in-house) and (v) a CO2 loop modulator (KT2003); the heated modulator was the slotted heater system (sweeper). Each modulator was optimised with respect to analyte peak widths at half height in the second-dimension. n-Alkanes, chlorinated alkanes, polychlorinated biphenyls (PCBs) and fluorinated polycyclic aromatic hydrocarbons (F-PAHs) were used as test analytes. The flow rate of the coolant was found to be an important parameter, i.e. the flow rate of the gaseous nitrogen in the KT2001, and of the liquid CO2 in the other cryogenic modulators. For the slotted heater the stroke velocity and pause time were important parameters. This modulator had a limited application range in terms of temperature due to a necessary 100 °C difference between sweeper and oven temperature. All cryogenic modulators were found to be suitable for the GC×GC analysis of high-boiling compounds, but the CO2 modulators are to be preferred to the KT2001 due to a wider application range and slightly narrower peaks. As regards the performance of three commercially available electron-capture detectors (ECDs), the aim was to obtain narrow peak widths in GC×GC, i.e. to avoid band broadening caused by the cell volume. The most important parameters were the flow rate of the make-up gas and the detector temperature which both should be as high as possible. Comparison of analyte peak widths obtained with ECD mode and flame ionisation detection (FID) showed that all ECDs exhibited band broadening compared to the FID. The narrowest peaks were obtained with the Agilent micro-ECD, which has a cell volume of only 150 μl.
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