Dieter Winkler

Staged Catalytic Combustion Method for the Advanced Zero Emissions Gas Turbine Power Plant

The AZEP (Advanced Zero Emissions Power Plant) project addresses the development of a novel “zero emissions,” gas turbine-based, power generation process to reduce CO2 emissions. Preliminary calculations indicate the attractiveness of this concept in comparison to conventional tail-end CO2 capture. Key to achieving the AZEP project targets is the development of a combustion system to burn natural gas with nearly stoichiometric amounts of oxygen and high levels of exhaust gas dilution. Within the first part of this study the fundamental combustion properties of AZEP gas mixtures are quantitatively determined. Significant inhibition results from the high level of exhaust gas dilution. In the second part a staged, rich–lean combustion concept, proposed to improve combustion stability, is investigated. It was shown that significant levels of hydrogen could be produced by a first stage, partial catalytic oxidation (PCO) of methane. Furthermore, it is shown that the addition of this produced hydrogen improves the stability of the downstream, second stage burnout zone. It was demonstrated that the produced syngas could act to reduce the blowout limit by ca. 100 K as compared to homogeneous gas phase combustion.Copyright

Catalytically stabilized combustion of CH 4 in zero emission processes

Publisher Summary This chapter highlights the great potential of catalytic syngas formation for Zero Emissions Power (ZEP) concepts. Syngas is produced with a high H2/CO ratio by utilizing the catalytic partial oxidation (POX) of methane combined with water reforming. The so formed syngas with a high H2/CO ratio can improve the blow-out characteristics of a homogenous downstream overall lean combustion. In order to design an appropriate catalyst, kinetic modeling can help to identify the crucial parameters determining catalytic activity and hydrogen selectivity. Complete oxidation in fuel-rich mixtures occurs at the shortest residence times (e.g. high flow rates and /or short catalysts); this reaction is followed by POX and reforming that both have longer characteristic residence times (smaller flow rates and /or longer catalysts) due to the required minimum operating temperature and the lack of oxygen. Therefore, higher inlet temperatures, longer residence times or higher catalyst dispersions respectively (high amount of active surface sites) favor POX and reforming, which both increase the syngas selectivity. The findings could be verified in experiments.