Page 71 - New Trends In Coal Conversion

Current status of CO 2 capture from coal facilities 37

2.2.2 Emerging POSTCC technologies demonstrated at pilot
scale in coal-fired power plants
2.2.2.1 Novel POSTCC solvent systems

General Electric’s chilled ammonia process (GE’s CAP) absorbs CO 2 from cooled flue

gas at 5e15 C and atmospheric pressure and releases pressurized CO 2 in the stripper
by heating. CAP has been demonstrated in nonsolids operating mode using a slip-
stream of a coal-fired boiler (20 MW e ) for 7,901 h with 97% availability, a capture
efficiency of 65%e85%, a CO 2 purity above 99.9%, and an energy consumption of
2.8 GJ/t. Calculations point out that the specific heat consumption could be reduced
to 2.2 GJ/t (Augustsson et al., 2017).

2.2.2.2 Enzyme-enabled POSTCC

CO 2 Solutions has demonstrated the technology at 1 t CO 2 /d scale using coal and nat-
ural gas flue gases, and at 10 t CO 2 /d scale using the flue gas from a natural gas-fired
boiler for over 2,500 h without enzyme deactivation and producing over 99.95% CO 2
using proprietary enzyme 1T1 dissolved in an aqueous carbonate solution with capture

rates between 65% and 95%. Absorption takes place at 30e40 C, and the solvent is
regenerated using hot water at 80e85 C. The specific reboiler duty for 80% capture

was measured to be 3.6 GJ/t (Fradette et al., 2017). Estimated costs lay between
$25e35/t CO 2 for large-scale applications. The technology is now under commercial
deployment. CO 2 Solutions has also developed a rotating packed bed (RPB), whose
performance was validated with coal and natural flue gas at Energy and Environmental
Research Center facilities in 2016. RPB testing suggests that the footprint of the cap-
ture unit can be drastically reduced.

2.2.2.3 Solid sorbents-based POSTCC processes

The first pilot plant based on physical adsorption technology that captured CO 2 from
the flue gas at a coal-fired power plant was constructed in Japan in 1991. This consisted
in a two-stage pressure and temperature swing adsorption (PTSA/PSA) pilot plant that
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treated 1,000 Nm /h of dehydrated flue gas using a Ca-X zeolite as adsorbent for over
4,000 h (>2,000 h continuous). The plant recovered 90% of the CO 2 producing 99%
CO 2 with an energy consumption of 2.0 GJ/t CO 2 (Ishibashi et al., 1996).
The largest demonstration of a solid sorbent-based POSTCC process integrated
with a coal-fired power plant is the 10 MW e KIERDRY® pilot plant (200 t CO 2 /d),
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fed with a 35,000 Nm /h slipstream of a 500 MW coal-fired boiler from Hadong power
station. The solid sorbent, a supported K 2 CO 3 phase, circulates between two fluidized
bed reactors: a riser, where CO 2 reacts with the sorbent at 40e80 C, and the bubbling

regenerator, where the sorbent is heated up to 140e200 C releasing the CO 2 . The

plant was operated with sorbent KEP-CO2P2 for over 3,400 h (1,000 h continuous),
with CO 2 removal above 80% and CO 2 purity above 95%. A recent simulation study
carried out for a 500 MW pulverized coal-fired power plant points out a regeneration
energy of 4e5 GJ/t (Jo et al., 2017).