Exergy of Solid Streams

To determine the exergy of a solid, it is reasonable to use a mass basis because streams such as coal or ash might not have any clearly defined molar structure. Hence, Equations (8.2) and (8.3) can be apphed. The thermomechanical exergy is determined only depending on the temperature, as shown in Equation (8.12). 

For all dry solid flows, the mean specific heat capacity Cn, - in kJ/(kg-K) is calculated based on coal enthalpy model HCOALGEN as implemented, for example, in Aspen Plus [2], which features a linear dependency from temperature 9i (in C)  

The exact chemical exergy can only be determined for pure carbon (graphite), as shown in Table 8.2. For the coal-feed streams, an approximation equation was used in line with literature [4], Equation (8.14), where HHV, is to be provided in MJ/kg, yielding the same unit for the chemical exergy. 

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