FGD and DeNOx
NEWSLETTER       

                                                                                                         September 2005
                                                                                                             No. 329

Advantages of IGCC Technology for New Coal-fired Power Plants

At Power-Gen Europe Alma Rodarte of GE compared integrated gasification combined cycle (IGCC) with conventional PC boilers. Benefits of IGCC include reduced emissions, increased efficiency, flexible fuel supply, avoided cost of byproduct disposal, lower water usage, fewer permitting and siting delays, sale of sulfur and gasification slag, and easier CO₂ removal, if necessary.

IGCC combines gasification technology with combined cycle technology. Gasification converts (at high temperature and pressure) any hydrocarbon into a synthesis gas (syngas) comprised primarily of hydrogen and carbon monoxide. The oxygen enriched environment enables a controlled partial oxidation reaction rather than full combustion. Oxygen is consumed in the gasification process and is no longer present in the syngas.

The combustor is designed to keep NO_x levels far below what is achievable with a conventional PC boiler with state of the art controls. In the combustion turbine part, GE uses diffusion combustion systems with diluent (inert) injection for NO_x control with optimal turn down and fuel flexibility. An SCR could also be added in the heat recovery steam generator, if extremely low NO_x emissions are required.

Sulfur exits the gasifier primarily as hydrogen sulfide. The H₂S is separated out and the syngas is then combusted in the gas turbine. This results in lower SO₂ emissions than a PC boiler with state of the art emission control systems. The H₂S removed from the syngas can be converted to elemental sulfur or sulfuric acid.

Particulates present from the gasification step are scrubbed from the syngas by water prior to combustion. Ninety to 96 percent of the mercury in the syngas can be removed using standard, activated carbon bed removal and molecular sieve technologies. The cost of 90 percent mercury removal from an IGCC is estimated at $3412 per pound of mercury removed. The CO₂ in the syngas can be captured in the acid gas clean-up prior to the combustion turbines. It would not be difficult to isolate this CO₂ for sequestration.

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