Reducing Gas Turbine Emissions Through Hydrogen-Enhanced, Steam-Injected Combustion

The Potential for reducing emissions from gas turbines by injecting steam for No_x control and hydrogen for Co control is evaluated through laboratory-scale combustion experiments. Results showed that hydrogen addition into a steam-injected diffusion combustor at hydrogen/fuel molar ratios of approximately 20 percent was associated with somewhat increased NO_x production and reduced CO emissions. Both effects are attributed to an increase in the local stoichiometric flame temperature. However, the decrease in CO was greater than the increase in NO_x, resulting in a net emissions benefit, or a shifting of the NO_x–CO curve toward the origin. Consequently, a greater range of NO_x/CO emissions targets could be achieved when hydrogen was available. Additional experiments on premixed systems with hydrogen injection showed a significant increase in operability. Cost estimates for producing hydrogen with a conventional fired steam reformer suggested high capital costs unless ample steam, is already available. Hence, the technology is particularly well suited for turbines that use steam for power augmentation. Alternate reforming technology, such as catalytic partial oxidation, offers the potential for reduced capital costs.