Combustion System Development and Test for Stoichiometric H2/O2 Combustion in Steam Atmosphere

Abstract An Oxy-H2 in steam atmosphere combustion system for the use in a novel application is presented. The combustion system is intended to be used in a steam boosting system (“Clean Steam-Booster”) for steam cycle applications. The steam boosting system can provide additional heat and mass flow for peak power demands as well as for grid stabilization by increasing the steam temperature and the mass flow for short operation periods. The approach is free of the classical combustion emissions, NOx and CO, as well as from the greenhouse gas, CO2. The combustion system is intended to be operated at close to stoichiometric conditions. The combustion system has been developed with the primary targets stable combustion, low H2 and O2 contents in the exhaust steam, and a good thermal design concept which allows meeting life for a production design. A couple of different burner and combustor variants were designed. All burners are diffusion style burners to avoid flashback issues which is a major risk for the Oxy-H2 combustion in case of premixing due to the very high flame speeds. The general design concept for the combustion system is a two-stage steam supply with one steam stage in the burner and a second through the combustor. To support design decisions, kinetic analyses were performed which are also discussed in the present paper. A core development step of the combustion system design is the design validation in a high-pressure combustion test. To enable such tests, a labscale rig was designed, manufactured, and erected, including pressure vessel and back pressure valve for tests up to 15 bar operation pressure. Also, the supply infrastructure for steam, O2 and H2 was well as the measurement and control system had to be setup at the combustion test facility of Siemens Energy in Mülheim/Germany. In the validation test, stable combustion operation up to 15 bar could be demonstrated. Moreover, low H2 and O2 contents in the exhaust gas were achieved. The thermal design worked as expected. The precise mass flow measurement and control were identified as major challenge for the operation of the combustion system close to stoichiometric conditions. Small deviations from a stoichiometric mixture have a direct and significant impact on the H2 and O2 fractions in the exhaust. As next steps another design iteration for the combustion system design, an up-scaling of the combustion system and closed loop steam cycle tests are planned.