Aspen Physical Property System - Physical Property Models

� User models for density and enthalpy. See User Models for
Nonconventional Properties in Chapter 6 of Aspen Plus User Models, for
details on writing the subroutines for these user models.
Notation
Most correlations for the calculation of coal properties require proximate,
ultimate, and other analyses. These are converted to a dry, mineral-matterfree
basis. Only the organic portion of the coal is considered.
Moisture corrections are made for all analyses except hydrogen, according to
the formula:
Where:
w = The value determined for weight fraction
w d
= The value on a dry basis
= The moisture weight fraction
For hydrogen, the formula includes a correction for free-moisture hydrogen:
The mineral matter content is calculated using the modified Parr formula:
The ash term corrects for water lost by decomposition of clays in the ash
determination. The average water constitution of clays is assumed to be 11.2
percent. The sulfur term allows for loss in weight of pyritic sulfur when pyrite
is burned to ferric oxide. The original Parr formula assumed that all sulfur is
pyritic sulfur. This formula included sulfatic and organic sulfur in the mineralmatter
calculation. When information regarding the forms of sulfur is
available, use the modified Parr formula to give a better approximation of the
percent of inorganic material present. Because chlorine is usually small for
United States coals, you can omit chlorine from the calculation.
Correct analyses from a dry basis to a dry, mineral-matter-free basis, using
the formula:
Where:
�w d = Correction factor for other losses, such as the loss
of carbon in carbonates and the loss of hydrogen
present in the water constitution of clays
298 4 Nonconventional Solid Property Models