Integrated gasification fuel cell cycle

Typical major components of the IGFC system, this one centered on a SOFC module running at atmospheric pressure, are identified in the simplified cycle diagram.

The system fuel as depicted is coal, converted to syngas by the gasifier, which is then supplied to the SOFC module after cleanup and pressure reduction.

The syngas pressure reduction step is accomplished in this system concept by an expander/generator, which thereby produces part of the cycle's gross power generation.

Oxygen for the coal gasification process is provided by a conventional air separation unit, and steam for the gasifier is raised by power system heat and recycled water.

The cold gas efficiency achieved by this gasifier is higher, circa 90%, and its syngas product stream will have methane content nominally in the 4-5% (vol) range.

[5] Fluidized-bed gasification (e.g., KBR Transport) proceeds with similar characteristics, but will exhibit somewhat lower syngas methane content, typically in the 2-3% (vol) range.

[6] Of particular interest to the SOFC-based IGFC power system is catalytic coal gasification, because of the characteristically high methane content of its resultant syngas.

Compared to conventional gasification summarized above, a catalytic gasifier would require less oxygen input, run at a lower process temperature, and produce a syngas stream with a higher methane concentration [15-30% (vol)], in addition to hydrogen and carbon monoxide.

In addition to high power system efficiencies, studies[2][9] also project significant IGFC system power plant capital cost, cost of electricity, and net water usage advantages: IGFC electric power systems integrating catalytic coal gasification with SOFC module designs that separate anode and cathode off-gas streams, and feature methane reformation-augmented SOFC cooling, would operate cleanly with very high electric efficiencies, while providing for high levels of carbon capture, and requiring low net water input.

In oxy-combustion, oxygen is extracted from air and used for fuel combustion, resulting in exhaust gases uncontaminated with nitrogen from which capture of a pure carbon dioxide stream is efficient.