Excerpt from Chlorine in Illinois Coal
Each of the four classes was then subdivided into, respectively, two, four, six, and eleven subclasses. In general, the higher the chlorine content, the greater is the possibility of corrosion. No coal containing over percent chlorine wa... s classified A free from corrosion. As the sulfur content increases, the risk of deposits and corrosion also increases. However, as the ash content increases, the possibility of problems with the coal decreases (crossley, 1963) He suggested that this scheme could be used to give valuable information concerning individual coals, to rate coal blends, and to suggest the best combination of any two or more 'coals to be utilized in a single boiler plant.
In addition to the blending of coals to minimize deposit formation and asso ciated corrosion, it may be possible to remove some of the deleterious constituents from the coal prior to firing. One instance of a marked decrease in total alkalies, following a two year period of storage, has been reported for a central Illinois coal (michel and Wilcoxson, 1955) A current study of the weathering of a central Illi nois coal over an 84.week period also shows this decrease in chlorine. The coal was crushed and sized to inch by 10 mesh and was left exposed out-of-doors with only a mesh screen over it to prevent contamination. The chlorine content decreased by one-half within an 8 week period and leveled off at approximately 36 percent of the original chlorine value after 24 weeks (john A. 'harrison, personal communication It is also possible to reduce the alkali chloride content of coal by washing. How ever, the amount that may be removed in this manner is probably small and may not be sufficient to alleviate specific problems. The amount that can be removed is dependent on the size consist of the coal being washed, composition of the wash water, original alkali chloride content of the coal, and duration of washing. Whether or not such a procedure is practical must be determined for each coal.
Other methods for preventing or minimizing these deposits are.
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