Performance and Emission Footprint of Decentralized H2/NH3 Gas Turbines With On-Site Ammonia Decomposition and Exhaust Aftertreatment

Abstract Within the energy sector, the mitigation of climate change necessitates a paradigm change towards the replacement of conventional with sustainable power generation technologies and more comprehensive environmental impact considerations of the energy supply system. Due to the inherent volatility of renewable power generation, gas turbines (GT) as dispatchable technology must be considered to maintain grid stability. As a potentially CO2-free energy vector, hydrogen is a promising fuel for future gas-based power generation but has drawbacks in terms of transport efficiency. As a result, hydrogen derivatives are gaining momentum, with ammonia as a prominent energy carrier due to the existing infrastructure. However, NH3 combustion is associated with significant NOx emissions, so measures such as decomposition to H2 or exhaust aftertreatment are required to comply with regulations. In this study, a physical-based gas turbine performance model and an ammonia decomposition reactor (ADR) model are used to quantify the operational power plant performance. Further, an emission calculation tool for different combustion chamber types (e.g., premixed (DLE), sequential (RQL)) and an exhaust aftertreatment model are used to quantify the operational emissions for variable H2/NH3 mixtures. It is shown that NOx emissions from NH3 firing can be reduced by an order of magnitude with an RQL compared to a DLE combustor. To comply with a regulatory NOx emission limit (150 mg/kWh), NH3 decomposition in an ADR is mandatory. However, in most cases, additionally heated ADRs are required to achieve feasibility of ADR size and cost. NH3 operation is favorable with low and high gas prices compared to H2 operation for all configurations and gas price scenarios. In a low and high gas price scenario, NH3 operation becomes economical from 2040 and 2039 compared to CH4 operation.