02507

Severe

>1.0

>0.7

Numerous fouling studies, especially those using low-rank coals, have shown a relationship of the sodium in the ash and the fouling rate. This is particularly true of coals with lignitic-type ash (low-iron, high-alkali, and high-alkaline earth metals) as found primarily in the United States west of the Mississippi river, although sodium does contribute to deposition in higher rank coals as well. A fouling index based on the percent of Na2O in coal ash is [27]:

Lignitic Ash Bituminous Ash

Percent Na2 O Fouling Potential Percent Na2 O Fouling Potential

<2.0

Low

<0.5

Low

0 0

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