Abstract

Integrated Gasification Combined Cycle (IGCC) is a technology that integrates the coal gasification and combined cycle to produce electricity efficiently. Due to the fact that the heating value of syngas from coal gasification process is typically lower than that of the natural gas, the conventional gas turbine will have to be adapted for syngas. The nozzle adjustment is the key to the successful transformation since the ignition properties are different between syngas and natural gas which have totally different compositions. The nozzles suitable for natural gas have been prone to partially melting around the flame stabilization holes on sidewalls of the nozzle in real operation. Thus a computational fluid dynamics (CFD) model was constructed for the syngas nozzles as well as combustion chamber of the gas turbine for low heating value syngas to study the thermostability of the nozzle. The detailed structure of the syngas nozzle, the combustion characteristics of syngas, as well as the actual operation condition of the gas turbine were all employed in the CFD model to improve the simulation accuracy. The reason of partially melting of the nozzles suitable for natural gas can be attributed to that the syngas leaked from the flame stabilization holes into the mainstream air can quickly mix with air, adhere to the sidewalls of the nozzles and then ignite around the holes which result in temperatures high enough to melt the material of the nozzle around the holes through CFD simulation. Finally, a new structure of the syngas nozzle was proposed and validated by CFD simulations. The simulation result shows that the flames caused by the syngas leaked from the flame stabilization holes are no longer adhering to the nozzle sidewalls and local high temperature can be lowered by about 30% which will not be able to melt the nozzle material.

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