Reviewing H2 combustion: a case study for non-fuel-cell power systems and safety in passive autocatalytic recombiners

Abstract

This Review looks at past and current research and development (R&D) on H2 combustion in terms of power generation in gas turbines and safety in passive autocatalytic recombiners (PARs). The drive toward reducing greenhouse gas emissions has forced researchers to look at carbon-free alternatives for power generation. Fortunately, H2 is one such fuel source and has been proposed as a fuel in gas turbines for large-scale power production. The effects of H2 on the heating values, flame speed, burning velocity, flammability range, flashback, blow-off, ignition delay, and emissions have been reported, and the trends and gaps in R&D identified. Properties such as flame speed, burning velocities, and flammability limits at typical gas turbine conditions (high pressures, high temperatures, lean equivalence ratios, and turbulent conditions) still need to be determined experimentally for H2 fuel mixtures, especially for mixtures with higher H2 concentrations and fuel mixtures with other fuels (such as biogas) as an evolutionary step toward adapting to a hydrogen economy. Much work has been done on pre-mixed dry low emissions and diffusion combustion with dilution as means of accommodating high hydrogen content (HHC) fuels. Staged combustion, vortex-stabilized combustion, multiple injection combustion, and catalytic combustion have been proposed for HHC fuels, yet still further R&D is required. Finally, oxy-fuel combustion provides a promising technology for HHC fuels, and researchers should focus on its testing and development. Although H2 is a good alternative to carbon-based fuel, its unique properties increase the probability of a fire hazard. Toward developing a hydrogen economy, we also need to ensure the safety of H2. Unfortunately, in unique scenarios, for instance in closed areas, venting and detection measures are no long adequate, nor possible, to ensure safety. Other intervention methods are required. H2 combustion in PARs is well known in the nuclear industry, but PARs can also be used for flammable gas control in other applications. The current status quo of PARs is discussed. Understanding and developing robust PARs for nuclear applications as well as alternative applications is vital for establishing a hydrogen economy. Gas turbine technologies that are H2 compatible have attracted much attention worldwide, within both academia and industry, especially in the U.S., Europe, and some Asian countries. Presently, the key role-players in this field are the U.S. Department of Energy, Hitachi, Kawasaki, Siemens, and General Electric. Some of the initiatives toward developing H2 gas turbines are discussed, with the strongest being the potential use in clean integrated coal gasification combined cycle applications