(698c) Techno-Economic Assessment of CO2 and SOx Capture Process By Dilute Aqueous Ammonia

Techno-economic
Assessment  of CO₂ and SO_x Capture Process by Dilute
Aqueous Ammonia

 

Hoan
Le Quoc Nguyen, David Shan-Hill Wong^*
 

Department
of Chemical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan

^*Corresponding
Author’s E-mail: dshwong@che.nthu.edu.tw

 

Keywords: Economic analysis;
CO₂ capture; Co-capture; Aqueous ammonia.

Dilute aqueous ammonia (NH₃)
solvent is one of the promising for post-combustion CO₂ capture.
This technology provides many advantages such as low solvent cost, negligible
solvent degradation and the simultaneous capture of multiple acid pollutants.
For example, Li et al. (2015) suggested an advanced NH₃-based CO₂
capture process that can be simultaneously achieved SO₂ and CO₂
removal. However, the economics of this co-capture was not been analyzed in
details.

In this work, we evaluate the
techno-economic feasibility of this concept using a 500 MWe gross coal-fired
power station with this advanced CO₂ capture process. Cost
estimation of Power plant was performed using the Integrated Environmental
Control Model (IECM) v9.5 and the capture plant was cost by ASPEN Plus v8.4. Figure
1 shows a brief description of two case studies including base case and
co-capture case. In the base case, the power plant has all the treatment steps
including selective catalytic reduction (SCR), electrostatic precipitator
(ESP), flue gas desulfurization (FGD) and post-combustion capture (PCC) by
aqueous ammonia process. In the co-capture case, FGD was eliminated and
additional ammonia was used in the PCC to remove the SO_x as ammonia
sulfate and ammonia sulfite. Besides, the reaction for absorbing SO₃
by aqueous ammonia is also included to the chemistry system in order to fully
describe the characteristic of the SO_x absorption in the capture
process, instead of that of SO₂ absorption only in literature.

Figure 2 shows the
capital cost (CAPEX) and operating cost (OPEX) of two cases. It can be seen
that the total capital cost for a whole power plant with full treatment steps
in the base case is about 1300 million dollars based on the U.S. cost reported
in 2014, which is included in the IECM framework. In that, the capital cost of
CO₂ capture unit is significant almost equal to 27% the capital cost
of total other units. By applying the advanced CO₂ capture unit to
remove SO_x and CO₂ simultaneously, the FGD unit can be
completely eliminated in the co-capture case. This leads to a CAPEX savings of
about 124 million dollars. The increase of the total operational cost due to
the increase of the amount of ammonia solvent make-up can also be nearly offset
by the elimination of operation cost by elimination of operation cost of the
FGD. Although there is an increase in operating cost of about 5.6 million dollars
due to the high recirculation rate required for the co-capture process, the
saving capital cost can cover this increase in 22 years. Moreover, without consumption
from FGD unit, the increase in net electrical output for sale leads to raising
the benefit of the power plant significantly. In addition to considering the
simple technique and operation of a single process, the combined SO_x
and CO₂ capture plant with the power plant is preferred rather than
the use of separate capture systems.

 

Figure 1: A brief description of two case
studies: Base case and Co-capture case.

 

 

Figure 2: CAPEX and OPEX of two cases.

 

Acknowledgment: This research was
supported by Grant MOST 107-3113-E-007-002 from the Ministry of Science and
Technology of the Republic of China.

 

References

1.      Li, K., Yu, H.,
Qi, G., Feron, P., Tade, M., Yu, J., and Wang, S., Rate-based modelling of
combined SO₂ removal and NH₃ recycling integrated with an
aqueous NH₃-based CO₂ capture process, Applied Energy,
148, 66-77, 2015.