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- Pettersson, Jesper, 1978, et al.
(författare)
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A pilot plant study of the effect of alkali salts on initial stages of the high temperature corrosion of alloy 304L
- 2004
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Ingår i: Materials Science Forum. - 1662-9752 .- 0255-5476. ; 461-464, s. 965-972
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Tidskriftsartikel (refereegranskat)abstract
- Alloy 304L was exposed for between 15 min to 12 hr in the 12MW CFB research boiler at the Chalmers university of technology using an air-cooled probe. The base fuel consisted of a mixture of 67% wood chips and 33% pellets. In addition to the base fuel experiment, a number of exposures were performed where S and Cl was added to the fuel in the form Of SO2(g) and HCl(aq) in order to control the flue gas chemistry in the superheater region. After the exposures the samples were analysed by ESEM/EDX, XRD and SAM. Burning a mixture of woodchips/pellets without adding sulphur or chlorine results in the formation of K2SO4 deposits on the corrosion probes. When HCl is added to the fuel KCl deposits form. The simultaneous addition of HCl and SO, results in a deposit consisting of a mixture of KCl and K2SO4. In all environments studied an oxide in the 100nm range forms. With time, the oxide becomes covered by ash deposits. After exposure to the biomass flue gas environment, the oxide is enriched in K, especially the outer part. Chlorine is not present in the oxide even when the KCl(s) forms on the surface. It is suggested that potassium chromate formation occurs by the reaction of potassium chloride with chromium oxide.
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| 2. |
- Moldovan, M., et al.
(författare)
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Environmental risk of particulate and soluble platinum group elements released from gasoline and diesel engine catalytic converters
- 2002
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Ingår i: The Science of the Total Environment. ; 296, s. 199-208
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Tidskriftsartikel (refereegranskat)abstract
- A comparison of platinum-group element (PGE) emission between gasoline and diesel engine catalytic converters is reported within this work. Whole raw exhaust fumes from four catalysts of three different types were examined during their useful lifetime, from fresh to 80 000 km. Two were gasoline engine catalysts (PtPdRh and PdRh), while the other two were diesel engine catalysts (Pt). Samples were collected following the 91441 EUDC driving cycle for light-duty vehicle testing, and the sample collection device used allowed differentiation between the particulate and soluble fractions, the latter being the most relevant from an environmental point of view. Analyses were performed by inductively coupled plasma-mass spectrometry (ICP-MS) (quadrupole and high resolution), and special attention was paid to the control of spectral interference, especially in the case of Pd and Rh. The results obtained show that, for fresh catalysts, the release of particulate PGE through car exhaust fumes does not follow any particular trend, with a wide range (onetwo orders of magnitude) for the content of noble metals emitted. The samples collected from 30 00080 000 km present a more homogeneous PGE release for all catalysts studied. A decrease of approximately one order of magnitude is observed with respect to the release from fresh catalysts, except in the case of the diesel engine catalyst, for which PGE emission continued to be higher than in the case of gasoline engines. The fraction of soluble PGE was found to represent less than 10% of the total amount released from fresh catalysts. For aged catalysts, the figures are significantly higher, especially for Pd and Rh. Particulate PGE can be considered as virtually biologically inert, while soluble PGE forms can represent an environmental risk due to their bioavailability, which leads them to accumulate in the environment.
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