Fouling Classification

Although the validity of the analytical data is uncertain, a generally accepted fouling classification of coal, according to total chlorine content (ASTM D-2361 ISO 352 ISO 587), is as follows ... 

Some additional methods of classification are under development that center on the use of lignite for combustion in utihty boilers or electric power generation. Correlations based on the sodium concentration in the lignitic ash (10), or soluble A1 concentration (11) are used. The classifications are often given in terms of the severity of boiler fouling. 

Table I shows the flexibility of the computational system. Six types of frequently encountered problems are classified according to their respective boundary conditions. In each classification, one or more run options can be selected. For example, Class 1 are typical simulation problems where the reactor outlet pressure and feed conversion are specified and the inlet pressure and radiant temperature are calculated. Alternatively, the effect of fouling can be determined by calculating a coking factor from a known pressure drop. The following examples illustrate applications of the system in problems under Classes 1, 5 and 6 respectively.

Figure 23.14 outlines a classification of fluidized bed dryers. For heat-sensitive materials, e.g., polymer pellets, use of immersed heat exchangers allows use of lower fluidizing air temperature without increasing drying time. Such exchangers can be used, however, only if the solids do not foul their surfaces. 

Sauf pour n 1 ou m. 1, Tone classification explicits de tels ystfemes semble sans espoir. On peut du moins ddfinir une fouls d invariants non triviaux pour un tel syst me, tels les polyn mes caract ristiques des S. ... 

Because of the wider variety of fouling mechanisms from liquids than from thermal fouling is classified with the liquid-solid interface as the prototype. The classification is based on the key physical/chemical process essential to the particular fouling phenomenon. Six primary categories have been identified ... 

The substantial effect on boiler sizing of the coal-ash classification is made clear by comparison of units sized for three types of coal. In general, an increased fouling tendency requires an increase in the furnace surface to lower the gas temperature entering the superheater, and an increased slagging potential of a coal causes furnaces designed for western coals to be substantially more conservative than those designed to fire eastern bituminous coak. 

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