EastWest 2012
EFFECT OF BIOFUEL IMPURITIES The use of biofuels is constantly increasing because of the tightening legislation [13]. The idea of this is to decrease exhaust and flue gas emissions and especially green house emissions (GHGs). However, even though carbon monoxide (CO) and hydrocarbon (HC) emissions have decreased, the release of nitrogen oxides (NOx) has increased [14]. Therefore, the SCR catalysts are still important to reduce NOx emissions. Besides that, impurities’ contents in biofuels depend naturally on the raw material used, such as sugars, starch and vegetable oils used. Figure 5 shows as an example of that, how much more plant based biodiesel contains impurities (e.g. P, Ca, Zn) compared to fossil based and traditionally used diesel. The effect of these biofuel-based impurities in the NH3-SCR applications has not been studied that much yet.
Figure 5. Chemical composition of particulate matter emitted from diesel engine driven with diesel or liquid biofuel, determined by Field Emission Scanning Electron Microscope (FESEM).
Based on the results by Väliheikki et al. [12, 15] it found that when 1 wt-% of sodium (Na) or potassium (K) was wet-impregnated on the studied fresh catalyst samples at room temperature, the effect of these impurities on specific surface areas (BET) measured by N2 physisorption by Micrometrics ASAP 2020 was relatively small (Table 1) (Figure 6).
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