Study of Experimental and Calculated Flame Speed of Methane/Oxygen-Enriched Flame in Gas Turbine Conditions As a Function of Water Dilution: Application to CO2 Capture by Membrane Processes

ASME Turbo Expo 2017: Turbomachinery Technical Conference and ExpositionVolume 4A: Combustion, Fuels and EmissionsCharlotte, North Carolina, USA, June 26–30, 2017Conference Sponsors: International Gas Turbine InstituteISBN: 978-0-7918-5084-8International audienceA solution for CCS (Carbon Dioxide Capture and Sequestration of CO2) is oxycombustion. Due to the high cost of pure O2 production, however, other approaches recently emerged such as post-combustion coupled with Oxygen Enhanced Air (OEA). This is the solution studied in this paper, which presents an innovative gas turbine cycle, the Oxygen Enriched Air Steam Injection Gas Turbine Cycle (OEASTIG). The OEASTIG cycle is composed of Methane combustion with OEA (Oxygen Enhanced Air), EGR (Exhaust Gas Recirculation) and H2O coming from a STIG (Steam Injection Gas Turbine). CO2 capture is achieved by a membrane separator. The final aim of this work is to predict NO and CO emissions in the gas turbine by experimental and numerical approaches. Before carrying out this study, the validation of a reaction mechanism is mandatory. Moreover, this new gas turbine cycle impacts on the combustion zone and it is therefore necessary to understand the consequences of H2O and CO2 dilution on combustion parameters. While a large number of papers deal with CO2 dilution, only a few papers have investigated the impact of water dilution on methane combustion. A study of the influence of H2O dilution on the combustion parameters by experimental and numerical approaches was therefore carried out and is reported in the present paper. The paper is divided in three parts: i) description of the innovative gas turbine (OEASTIG) cycle and determination of the reactive mixtures compatible with its operation; ii) validation of the reaction mechanism by comparing laminar methane flame velocity measurements performed in a stainless steel spherical combustion chamber with calculations carried out in a freely propagating flame using the Chemical Workbench v.4.1. Package in conjunction with the GRIMech3.0 reaction mechanism; iii) Extrapolation to gas turbine conditions by prediction of flame velocities and determination of the feasible conditions from a gas turbine point of view (flame stability). In particular, mixtures (composed of CH4/O2/N2/H2O or CO2) leading to the same adiabatic temperature were investigated. Lastly, the influence of oxygen enrichment and H2O dilution (compared to CO2 dilution) were investigated