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15.9.5 Modeling Coal Combustion Using the Non-Premixed Model

If your model involves coal combustion, the fuel and secondary stream compositions can be input in one of several ways. You can use a single mixture fraction (fuel stream) to represent the coal, defining the fuel composition as a mixture of volatiles and char (solid carbon). Alternatively, you can use two mixture fractions (fuel and secondary streams), defining the volatiles and char separately. In two-mixture-fraction models for coal combustion, the fuel stream represents the char and the secondary stream represents volatiles. This section describes the modeling options and special input procedures for coal combustion models using the non-premixed approach.

There are three options for coal combustion:



Defining the Coal Composition: Single-Mixture-Fraction Models


When coal is modeled using a single mixture fraction (the fuel stream), the fuel stream composition can be input using the conventional approach or the empirical fuel approach.

Note that for both of these composition input methods, you should take care to distinguish atomic carbon, C, from solid carbon, C(s). Atomic carbon should only be selected if you are using the empirical fuel input method.

See Section  15.15 for details about further inputs for modeling coal combustion.



Defining the Coal Composition: Two-Mixture-Fraction Models


If your FLUENT model will represent the coal components using both the fuel stream and the secondary stream, one stream is used to represent char and the other stream is used to represent volatiles. (In the procedures below, it is assumed that the fuel stream represents the char and the secondary stream represents the volatiles.)

As in single-mixture-fraction cases, the fuel stream and secondary stream compositions in a two-mixture-fraction case can be input using either the conventional approach or the empirical fuel approach.

Note that for both of these composition input methods, you should take care to distinguish atomic carbon, C, from solid carbon, C(s). Atomic carbon should only be selected if you are using the empirical fuel input method.

See Section  15.15 for details about further inputs for modeling coal combustion.


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