Rising global CO2 levels underscore the
urgent need for effective carbon capture and utilization (CCU) technologies to
support a circular carbon economy. This study evaluates the techno-economic
per- formance of a novel integrated CCU system that combines a K2CO3-based
capture column with a bicarbonate electrolyser for syngas production,
specifically targeting applications in the steel industry. An ASPEN PLUS model
of the capture column was developed and integrated with a pH-dependent Faradaic
Efficiency (FE) model of the electrolyser in Excel. Five cases were defined:
(I) 90 wt% CO2 capture, (II) syngas production with a 2:1 H2/CO ratio for the
Fischer-Tropsch process, (III) electrolyser operation with FECO > 50%, (IV)
syngas composition suited as feedstock for electric arc furnaces (EAF) in the
Energiron III process, and (V) an intermediate pH step. A techno-economic
analysis (TEA) was conducted across worst, base, and best-case scenarios for
each case. Key findings reveal a
trade-off between achieving high FECO at low pH levels and maximizing CO2 capture
efficiency at high pH levels. Systems operating with large pH steps
demonstrated a lower Lev- elized Cost of Syngas normalized to the Lower Heating
Value (LCOSLHV ), due to increased hydrogen output. In contrast, systems with
smaller and narrower pH steps incurred higher LCOSLHV due to their output’s
lower LHV. The techno-economic analysis (TEA) indicates that the operational
expenditure (OPEX) for the integrated CCU system is currently too high to be
cost-competitive with alternative solu- tions. Sensitivity analysis reveals
that the integrated CCU system is competitive with other electrolysis methods
only under best-case conditions. Electricity costs and a low CO2 utilization
ratio are identified as the primary drivers of OPEX. Improvements in these
areas result in the most significant reduction in LCOSLHV, making them critical
enablers for the integrated CCU system. Additionally, the cost per kilogram of
CO2 saved is high compared to EU CO2 Emission Trading System (ETS) prices. Current bicarbonate electrolysers are more
costly than gas-fed CO2RR systems in terms of Unit Capital Cost (UCC) per
kilogram of CO produced, largely due to reduced performance at higher current
den- sities (>100 mA/cm2). Achieving CAPEX parity with gas-fed CO2RR systems
would require increasing current densities while maintaining high FECO and
sustaining these efficiencies at alkaline pH levels. Future work should prioritize reducing both
OPEX and CAPEX for the system, with a particular focus on improving the
technical performance of the bicarbonate electrolyser. Key objectives include
increasing current density while maintaining high FECO at alkaline pH levels,
improving the CO2 utilization ratio, and enhancing the stability of the
electrolyser. Keywords: Carbon Capture
and Utilization, Bicarbonate Electrolysis, K2CO3-based CO2 Capture, Ben- field
Process, Integrated CCU System, Techno-economic Analysis