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Adams et al. [40] divided SOFC systems for CO₂ capture into first‐ and second‐generation systems as a function of the operating pressure of the SOFC. Low‐pressure, first‐generation SOFC systems are the most promising option for SOFC commercialization at large scale (100 MW or greater) in the short term. Several process configurations and design options are possible (Figure 1.10), although those generally follow the same pattern and offer some flexibility to select the optimum combination of variables such as gas clean‐up/reforming, water gas shift (WGS), CO₂ capture technology, and heat recovery.

Second‐generation SOFC systems are high‐pressure SOFCs with separate streams for the anode and cathode exhausts. This arrangement promotes the use of an SOFC system that captures and compresses CO₂ at significantly reduced costs and minimum complexity via “pre‐anode” and/or “post‐anode” capture.

In the pre‐anode CO₂ capture process, syngas is generated at high pressure through high pressure coal gasification or by reforming the natural gas available from a natural gas pipeline at high pressure. Similar to the above cases, the syngas can be optionally shifted using the WGS reaction, creating a stream of steam, H₂, and CO₂. Up to about 90% of the CO₂ can then be recovered from the syngas (or shifted syngas) using absorption or adsorption technologies.

The post‐anode CO₂ capture has been extensively studied in SOFC IGCC and natural gas cycles. A simple IGFC system is similar to an IGCC system, but the gas turbine (GT) power island is replaced by a FC island. Some system configurations still have a gas or steam turbine to utilize the extra heat. “Post‐anode” CO₂ capture can be applied via CO₂ separation from H₂O via H₂O condensation (or via cooling, knockout, and additional drying) and can effectively result in a 100% CO₂ removal. A separation system that uses condensation followed by a cascade of flash drums can be used to produce CO₂ at high enough purity for pipeline transport at the SOFC anode exhaust pressure.