High moisture low-rank coal

The dry-feeding system of the Shell gasifier requires the water content in the bituminous coal to be less than -2 wt %. For high-moisture, low-rank coal, the required water content could be less than 10wt%. 

High-rank coal Refers to anthracite, meta-anthracite, and bituminous coals, which are relatively low in moisture, high in combustible carbon, and have high heat contents (compare low-rank coal, lignite, and subbituminous coal). 

It is often difficult to apply indirect weight-loss procedures to the determination of moisture content in low-rank coal that has a high moisture content and is susceptible to oxidation. Some ovens may be inadequate for determining the... 

Because of the complexity of the coalification processes, different measures are used to define different levels of rank (Table I) high moisture, low heating value, and nonagglomerating character of the coal define the rank (group) within the lignite and subbituminous classes and volatile matter (or fixed carbon) define the various groups of rank in the bituminous and anthracite classes. In addition to these properties, the reflectance of vitrinite, carbon content of the coal (dry, mineral matter free), and some other properties change proportionately as rank increases (Table I). 

Recent work has suggested that the coals of the Illinois Basin were never buried deeper than about 1500 m. (44), compared with an estimated 3000 m. or more for the coals of western Pennsylvania in the Eastern province. Presumably as a consequence, the coals of the Interior province tend to show low values of vitrinite reflectance and high values of moisture-holding capacity relative to coals of other areas of apparently similar rank (45). 

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