Page 81 - New Trends In Coal Conversion

Current status of CO 2 capture from coal facilities 47

The technology and the sorbent are now available worldwide at commercial scale via
license and sale, respectively (Denton et al., 2016).
Kemper County IGCC aimed to be the first demonstration project of PRECC at
commercial scale. The facility consisted of lignite handling and gasification in two
Transport Integrated Gasifiers (TRIGs), synthesis gas processing and cleanup, PRECC
using Selexol, two combustion turbines, and a steam turbine with capacity to generate
a peak of 582 MW (net) of electricity. The facility started to produce syngas in July
2016 and electricity in January 2017, 3 years behind schedule and $4 billion above
budget. However, due to operational issues, gasification was suspended in June
2017. The plant is currently running on natural gas.

2.4.2 Emerging technologies for PRECC
Adsorption or sorption enhanced water gas shift (SEWGS) processes have scope for
reducing the cost of PRECC, although present lesser stage of development than
absorption-based PRECC processes.
TDA has evaluated PSA at pilot scale using a slipstream of 0.1 MW e of coal-
derived syngas at Wabash River IGCC plant and at NCCC pilot air-blown TRIG
gasifier. The PSA prototype consists of eight cylindrical adsorbers, two recircula-
tion/buffer tanks, and two inlet/outlet accumulators. TDA’s patented sorbent is a mes-
oporous carbon with grafted functional groups that selectively adsorb CO 2 from

shifted syngas at high pressure (34 bar) and temperature (240e250 C) by strong
physisorption. The adsorbent is regenerated by hybrid concentration/pressure swing
using a purge of steam at 10 bar in near-isothermal operation. The higher operation
temperature of the capture unit provides higher IGCC efficiency compared with the
Selexol reference case. 707 h of continuous operation were completed at NCCC
with capture rates above 90% and results above design expectations. The pilot will
be retrofitted to allow the use of higher flow rates, which will bring performance im-
provements. A new test campaign will be carried out at Sinopec Yangzi Petrochemical
plant at Nanjing, China, on coal-derived syngas from an oxygen-blown gasifier. The
technoeconomic analysis points out a cost reduction of 15%e30% compared with
the Selexol reference case (Alptekin et al., 2017).
TDA is also developing a combined WGS-PSA process that entails reducing capital
cost and achieving higher CO conversions with lower steam excess, shifting the effi-
ciency of the power cycle. The integrated operation of the high-temperature proprietary
sorbent with a commercial low-temperature catalyst was demonstrated in 2015 with a
slipstream of coal-derived syngas at NCCC at 0.2 kg CO 2 /h scale. Early-stage testing
showed that the heat released by WGS is detrimental for PSA. Direct water injection
in the WGS-PSA reactor has shown to provide adequate temperature control and higher
plant efficiencies for all the coals and gasifiers evaluated. The improved technology was
planned to be demonstrated at Praxair and NCCC at the 10 kg CO 2 /h scale in 2017. Ac-
cording to a technoeconomic analysis, the integrated WGS-PSA process offers a 0.5%
improvement in efficiency over PSA alone (Alptekin, 2017).
In SEWGS, sulfur removal, WGS reaction, and CO 2 capture are accomplished in a
single step, avoiding the inefficient temperature step changes of conventional syngas