Page 72 - New Trends In Coal Conversion

38 New Trends in Coal Conversion

The Kawasaki CO 2 Capture (KCC) system, based on an amine-coated porous
material, was validated using the exhaust gas from a pulverized coal test facility in
a fixed bed test plant of 10 t/d capacity. The thermal energy required to regenerate
the sorbent, nearly 2.3 GJ/t, can be supplied using waste heat. For large-scale applica-
tions, the KCC system configuration is a moving bed (MB) process where the sorbent

circulates between the sorption reactor, working at 35 C, the desorption reactor, and
the sorbent dryer by means of conveyors and gravity. During the feasibility test carried
out in an MB pilot plant with coal combustion exhaust gas, 3.5 t CO 2 /d were captured
continuously for 3 h with 95% purity and 75% capture rate using saturated steam at 60
C to regenerate the sorbent. Higher capture rates can be achieved by increasing the

solid circulation rate (Okumura et al., 2017). The electricity consumption of the
KCC process is 1.3 GJ/t CO 2 . Kawasaki is planning to upscale the technology to
50 t/d by 2019 and to achieve commercialization for thermal power plants (500 t/d)
beyond 2020.
The ADAsorb POSTCC solid sorbent technology uses a three-staged fluidized bed
adsorber equipped with cooling heat exchangers and a single fluidized bed for regen-
eration. The technology was validated in a 1 MW e TSA pilot facility at a Southern
Company coal power plant, in the United States, using an amine-based ion-
exchange polymer. Although several limitations were encountered during pilot testing
(90% capture was achieved only at lower flow rates [z0.24 MW e ] and CO 2 purity was
lower than expected), modeling suggests that the process might be competitive to
benchmark technology through process and sorbent development (Sjostrom et al.,
2016).
The advanced carbon sorbent POSTCC technology, developed by SRI, Linde, and
ATMI, was validated using a 0.5 MW e slipstream of a pulverized coal-fired boiler
(z10 t/d) at the National Carbon Capture Center (NCCC) in the United States.
The process consists of a single vertical column that holds the adsorber and the
desorber: the gas and the solid circulate counter currently, with the carbon beads
lifted to the top of the column by pneumatic transport. Low pressure steam from

NCCC was used as a heat source to preheat the adsorbent to 60 C and to generate

steam that was injected in the stripper (adsorbent heated up to z120 C). Over 250 h
of testing were completed with a capture rate of 67% and a CO 2 purity of 93%. Steam
demand and sorbent attrition were higher than anticipated due to external heat losses
and high-velocity impact collisions, and flue gas pressure fluctuation and moisture
condensation affected sorbent circulation and capture rate. Higher capture rate and
purity could be achieved by process development. The cost of CO 2 avoided using
this technology was estimated to be $45/t CO 2 ; efforts are directed to reach the
DOE target (SRI, 2016).
TDA Research has developed a simulated moving bed process that makes use of
alkalized alumina as adsorbent. The process operates near atmospheric pressure and

adiabatically, between 120 and 140 C, using low pressure steam to regenerate the
sorbent. Estimated cost of CO 2 captured is $38.7/t. The patented technology will be
demonstrated on a 0.5 MW equivalent slipstream (z10 t/d) at NCCC in 2018 (Elliott
and Yi, 2017).