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Current status of CO 2 capture from coal facilities 41

is supplied to the mill, so it needs to be cooled and washed in the flue gas condenser to
remove moisture, halides, and SO 3 . If an alkaline solution is added to the water wash or
a direct contact cooler with polishing scrubber is used, SO 2 can also be partially
removed. Secondary RFG can be taken from different points of the process leading
to warm or hot recycle with high particulate content, although generally it is preferred
to recycle dust-free flue gas to prevent erosion, corrosion, fouling, and clogging issues.
Different configurations are possible.
The first project that demonstrated integrated OPC in a retrofitted boiler from a
power plant at large scale (30 MW e ) was Callide A, in Australia. Retrofitting included
the construction of two ASUs, a flue gas treatment plant and a CPU that treated a slip-
stream of approximately 11% of all the exhaust, the replacement of two burners of the
boiler by IHI low NOx burners and two direct O 2 injection lances for test purposes, a
flue gas heater, an induced draft fan, and a gas recirculation fan. Flue gas was cooled

down to 150 C before entering the fabric filter, and the dust-free RFG was divided
into primary RFG, which after water removal was preheated and used to dry and
transport the pulverized coal, and the secondary RFG, which was fed to the boiler.
O 2 was premixed with the secondary RFG in normal operation or fed directly to
the boiler using the lances during specific tests. The CPU consisted of a water spray
and a low-pressure scrubber with caustic soda wash that eliminated SO 2 ,HCl, HF,
Hg, and NO 2 ,afabric filter and screen filter that eliminated particles from the gas
stream exiting the low-pressure scrubber, an Atlas Copco 4-stage centrifugal
compressor with intercoolers that eliminated NO as nitric acid in the condensates,
a high-pressure scrubber with chilled water that removed the remaining NO x ,a
TSA drier, and a cryogenic plant with an ammonia refrigeration circuit and recycled

CO 2 . The CPU produced 99.9% CO 2 in liquefied form at 27 C and 1.45e2.3 MPa.
The boiler operated over 10,000 h in oxy-combustion mode (>5,500 h with capture).
The project included the injection of the liquefied CO 2 produced between October
and December 2014 at CO2CRC’s Otway Project site in South Western Victoria
(Spero et al., 2014).
Shanxi International Energy Group will demonstrate OPC at commercial scale at a
350 MW supercritical coal-fired power plant that is planned to start operation in 2020
in China, with a capture capacity of 2 Mt CO 2 /y. The project will use Air Products’
oxy-combustion system and compression and purification technology, validated at
Schwarze Pumpe pilot plant in 2010e11.

2.3.2 Oxy-combustion in fluidized boilers
Oxy-combustion in fluidized boilers (OFB) has received less attention than OPC,
despite its inherent advantages, such as greater fuel flexibility, lower NO x emissions,
in situ SO x capture, and reduced boiler size. So far, OFB technology has been validated
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up to the 30 MW th scale at CIUDEN, Spain, where the CPU treats 4500 Nm /h of flue
gas, producing 11 t/d of 99% purity CO 2 (de Dios, 2015). OFB technology has reached
TRL 6.