Mass and energy fl ows
As outlined before the optimal configuration of gasification
technology is highly dependent on the properties of the feedstock
that is to be converted. Table 5 provides information about the
composition and the respective specific HHVs of biomass and coal
derived slurries investigated in this study computed with Eq. (2).
Depending on the kind of slurry, the operating pressure and the
gasification agent used in the gasification process, the input
parameters for the respective configurations differ from one another.
Table 6 illustrates the changes in input parameters.
Combining the coal and biomass slurries corresponds in all cases
to 1000 MWth input. The minor differences in thermal input are
based on auxiliary natural gas consumption as well as in cases 2
and 6 from natural gas consumption for steam super heating. The
gasification temperature is constant in all cases but the quench
temperature in 80 bar operating pressure cases is about 35 °C
higher. As a result, the quench water flow in these cases is lower
as well. The stoichiometric oxygen-to-fuel ratio lambda is lowest
in co-feed cases, which has a major influence on electricity
consumption. The electricity consumption of the air separation
unit accounts for about 86% up to 96% of the electricity consumption
depending on whether or not steam has to be compressed in order
to be injected into the gasifier and whether or not coal has to be pretreated.
Table 7 summarizes the final syngas composition which is
considered as the output of the gasification facility in this assessment.