(724g) Polygeneration of Fischer-Tropsch Fuels and Electricity by Hybridised Solar Gasification of Coal – a Pseudo-Dynamic Process Model

Polygeneration of Fischer-Tropsch fuels
and electricity by hybridised solar gasification of coal ? a pseudo-dynamic
process model.

Ashok A Kaniyal^1,2*, Philip
J van Eyk^1,3, Graham J NATHAN^1,2, Peter J Ashman^1,3,
Jonathan J Pincus^1,4

*Email: ashok.kaniyal@adelaide.edu.au; Phone: +61403691321.

¹ Centre for Energy Technology, The University of Adelaide, South Australia, AUSTRALIA, 5005

² School of Mechanical Engineering, The University of Adelaide, South Australia, AUSTRALIA 5005

³ School of Chemical Engineering, The University of Adelaide, South Australia, AUSTRALIA, 5005

⁴ School of
Economics, The University of Adelaide, South Australia, Australia 5005
Abstract

Presented is a comparative energetic
and environmental performance analysis of a solar hybridised gasification, coal
to liquids polygeneration system and a non-solar reference. Using AspenPlus and
HYSYS software, the reference system was configured, assuming the integration
of a pressurised, Shell entrained flow gasifier with a Fischer Tropsch liquids
(FTL) polygeneration facility. The hybrid plant assumes the feasibility of
integrating an atmospheric, continuously operational,
directly irradiated, oxygen blown hybrid solar reactor with this polygeneration
facility. To mitigate the diurnal and stochastic impacts of the solar-boosted
production of syngas, the hybrid polygeneration model was also assumed to be
configured with a pressurised syngas storage plant. Here, the dynamic operation
of the polygeneration system was modeled using a pseudo-steady state
approximation for two, six day time-series of validated solar insolation model
data. The two time-series were selected to represent a period in ?summer'
characterised by a steady, low cloud period of solar insolation, and a period
in ?winter' marked by intermittent solar insolation and high cloud. Using these
data, a MATLAB model was used to predict the maximum steady rate of liquids
that could be produced for the given solar insolation scenario.

For the summer time series, the hybrid
solar gasification system was shown to improve the steady rate of liquids
production by 32% and decrease the source-to-wheel (STW) GHG emissions per GJ
FTL by 26%, relative to the reference. For the winter time-series, only a
marginal improvement in liquids production was predicted .This result followed
from the assumed difference in gasification temperatures between the hybrid
system and the reference. On a total energetic output basis, GHG emissions were
shown to decrease relative to the reference by 17-21 percentage points for the
summer-time series, but increase by 18 percentage points for the winter
time-series. This increase in GHG emissions follows the large parasitic impact
of SG compression on the hybrid system's net electrical output. Additional
sensitivity analyses identified the potentially significant energetic and
environmental value of either operating the hybrid gasifier at
just 2 bar-g instead of 1 bar-g or incorporating an O₂
storage system to reduce the parasitic load of the hybrid system's ASU.

Importantly, the present analysis found
the difference in the steady output from the FT reactor and electricity
generating plant between the summer and winter time-series to be within the
feasible operational limits of the respective plant components. This provides
assurance as to the feasibility of developing a solar hybridised C2L
polygeneration facility using commercially available plant components.

Keywords

Coal gasification, concentrated solar energy, hybrid solar gasification,
Fischer-Tropsch liquids production, pseudo-dynamic process modeling, lifecycle GHG assessment.