Page 86 - New Trends In Coal Conversion

52 New Trends in Coal Conversion

sector. POSTCC technologies could be developed for cement production at commer-
cial scale by 2020, with the added advantage that the kiln flue gas presents greater CO 2
concentration than that of a pulverized coal power plant. However, most of the waste
heat from the kiln flue gases is already used for raw material drying (see Fig. 2.7), so
this source of heat could only provide a small fraction of the reboiler duty ( 15%),
requiring an external source of heat. OXYCC technology requires the adaptation of
the clinker production process; this could be developed at the commercial scale beyond
2025 (IEAGHG, 2013).
Carbonfree Chemicals captures 0.075 Mt CO 2 /y from the coal-fired Capitol
Aggregates cement plant in San Antonio, Texas, using the patented SkyMine® pro-
cess, where a sodium hydroxide solution is used to capture the CO 2 in a packed
scrubber. The solution is produced by the electrolysis of salt and water that releases
hydrogen and chlorine gases (IEAGHG, 2013). Revenues arise from selling process
by-products: sodium bicarbonate, hydrochloric acid, bleach, and caustic soda (Perilli,
2014). Additional 0.225 Mt of CO 2 emissions are claimed to be offset by shipping
CO 2 -negative chemicals to market and displacing CO 2 -intensive products. An alterna-
tive process, SkyCycle®, which uses waste heat instead of electricity, with an esti-
mated cost of $16e25/t CO 2 , is being developed and evaluated at pilot scale at San
Antonio facilities.
ITRI’s high-efficiency calcium looping technology (HECLOT) was evaluated at the
1.9 MW th scale (1 t CO 2 /h) in Taiwan Cement Corporation’s cement plant in Heping.
This is the largest CaL facility worldwide. The flue gas is fed to a bubbling fluidized
bed carbonator, and the spent CaCO 3 is fed to a rotary kiln calciner, where diesel oxy-
combustion provides the heat for calcination, releasing near-pure CO 2 that is partly
recirculated to reduce the temperature. The loop closes by collecting the CaO in a
tank under the calciner and pneumatically transporting it to the storage tank above
the carbonator. Over 600 h of operation were accumulated (>300 h continuous loop-
ing), achieving the design capacity, 1 t CO 2 /h, with a capture rate of 85% (Chang et al.,
2014). The estimated cost of CO 2 captured for the pilot is $40/t. ITRI is developing the
technology with the aim to reduce the cost to $30/t. A demonstration plant of 30 MW th
is under construction (Hsu, 2014).
Norcem CO 2 capture project evaluated different technologies at Norcem’s cement
plant in Brevik, Norway. Aker Solution’s Advanced Carbon Capture (ACC), which is
a mature technology validated at Technology Centre Mongstad (Tokheim et al., 2015),
was demonstrated using the proprietary amine-based solvent S26 for over 5,500 h. The
energy requirement for the basic process without heat integration is 3 GJ/t of CO 2 at
90% capture rate from a flue gas containing 20% CO 2 . A feasibility study indicates
that 50% of annual emissions (0.4 Mt CO 2 /y) could be captured solely using waste
heat without excessive heat integration and 85% of emissions (0.715 Mt CO 2 /y)
with extensive heat integration (Knudsen, 2015). Aker Solutions’ technology has
been selected to design a carbon capture plant with a capacity of 0.4 Mt CO 2 /y inte-
grated with the cement factory. An investment decision will be made by 2019, and
the full-scale carbon capture plant might be operational in 2022 (Nooryani, 2017).
RTI’s solid sorbent capture technology, which uses a polyethylenimine-based solid
sorbent working in a TSA process, was evaluated at Brevik cement plant at pilot scale.