Page 89 - New Trends In Coal Conversion

54 New Trends in Coal Conversion

The sorbent circulates between the adsorber, at 60e70 C, and the desorber, at

110e120 C. Estimated costs, based on extended testing, lie within 38 and 46 V/t,
depending on the amount of waste heat used from the cement plant (Nelson et al.,
2017). The energy consumption, 2.4 GJ/t without heat integration, is lower than that
of ACC, albeit the lesser development stage (Tokheim et al., 2015).
Fixed site carrier membranes developed by Norwegian University of Science and
Technology (NTNU) were operated for 6 months in Brevik showing sufficient dura-
bility but lower performance than expected. A technoeconomic analysis based on
the modeling of a two-stage vacuum-driven membrane process led to a cost of CO 2
captured of 46 V/t for a capture rate of 85%, although the cost depends on electricity
price (H€ agg et al., 2015).
The emissions from St. Mary’s cement plant in Ontario, Canada, are being used to
grow microalgae in a pilot biorefinery built next to the cement plant. A third-
3
generation photobioreactor (25 m boxlike structure filled with water and outfitted
with high-efficiency LED lights) receives 1% of the coal-fired kiln flue gas directly
through the pipeline and produces 50 kg/d of dry microalgae, offsetting 0.1 t/d of
CO 2 emissions. The goal of the project is to produce biofuels onsite for use in the
cement plant. The next step will be small-scale production to prepare for full-scale
commercial production by 2023 (Church, 2017).
The European-funded project CEMPAC is currently evaluating three different
POSTCC technologies (CAP, membrane-assisted CO 2 liquefaction, and CaL) and
OXYCC technologies for the cement industry (Jordal et al., 2017).

2.6 Concluding remarks

CCUS needs to be deployed in the power and industrial sectors to abate coal-related

emissions as soon as possible to limit global warming to 1.5e2 C above preindustrial
levels. Up to date, the technology that has reached greatest development stage is
POSTCC amine-based absorption processes, which are running at commercial scale
in coal-fired power plants. Alternative POSTCC technologies such as enzymes, solid
sorbents, or membranes present scope to reduce the energy penalty of amine-based
absorption processes, although they need further development. PRECC and OXYCC,
which will be demonstrated at commercial scale in the power sector in the near future,
present scope to reduce the cost of capture in new plants. However, POSTCC is the
single technology that can be applied to the existing coal fleet.
The main advantage of OXYCC is that CO 2 only needs to be purified and com-
pressed, and its main drawback is the need of an energy-intensive air separation
unit to produce oxygen. The latter could be avoided using emerging CLC processes,
which present lower energy penalty.
The main advantage of PRECC is the higher partial pressure of CO 2 compared with
POSTCC, which facilitates the capture step. One of the most promising options for
PRECC is the possibility of increasing H 2 conversion with lower steam ratios through
the development of SEWGS processes.