Power-to-gas and the consequences: impact of higher hydrogen concentrations in natural gas on industrial combustion processes

Abstract Operators of public electricity grids today are faced with the challenge of integrating increasing numbers of renewable and decentralized energy sources such as wind turbines and photovoltaic power plants into their grids. These sources produce electricity in a very inconstant manner due to the volatility of wind and solar power which further complicates power grid control and management. One key component that is required for modern energy infrastructures is the capacity to store large amounts of energy in an economically feasible way. One solution that is being discussed in this context is “power-to-gas”, i.e. the use of surplus electricity to produce hydrogen (or even methane with an additional methanation process) which is then injected into the public natural gas grid. The huge storage capacity of the gas grid would serve as a buffer, offering benefits with regards to sustainability and climate protection while also being cost-effective since the required infrastructure is already in place. One consequence would be, however, that the distributed natural gas could contain larger and fluctuating amounts of hydrogen. There is some uncertainty how different gas-fired applications and processes react to these changes. While there have already been several investigations for domestic appliances (generally finding that moderate amounts of H 2 do not pose any safety risks, which is the primary focus of domestic gas utilization) there are still open questions concerning large-scale industrial gas utilization. Here, in addition to operational safety, factors like efficiency, pollutant emissions (NO X ), process stability and of course product quality have to be taken into account. In a German research project, Gas- und Warme-Institut Essen e. V. (GWI) investigated the impact of higher and fluctuating hydrogen contents (up to 50 vol.-%, much higher than what is currently envisioned) on a variety of industrial combustion systems, using both numerical and experimental methods. The effects on operational aspects such as combustion behavior, flame monitoring and pollutant emissions were analyzed. Some results of these investigations will be presented in this contribution.