Economic analysis for hydrogen – ammonia decarbonization of a natural gas plant – a phased approach

This paper summarizes a comprehensive technical and economic analysis of a hydrogen-ammonia upgrade to an existing 42 MW natural gas plant. A phased approach is carefully chosen which deploys low-carbon technology in modules which are palatable by large-scale utility customers. The objective is to minimize capital costs of the conversion while maximizing decarbonization as each phase is deployed.

A phased approach delivers optionality to utilities which are often locked into carbon-emitting technologies by protracted investment durations. Phase one details implementation of an on-site thermal pyrolysis system. Existing natural gas infrastructure and plant waste heat are used to provide clean hydrogen. A thermal pyrolysis system using proven technology converts pressurized natural gas to hydrogen and atomic carbon, colloquially referred to as “Turquoise Hydrogen”. The system re-injects hydrogen into the plant fuel supply which is then burned as a blended fuel. The pyrolysis system isoptimized to reduce CO2 emissions without triggering costly combustion modifications or plant fuel storage. Phase two details blending sufficient ammonia volume with phase one hydrogen output to fully decarbonize the plant. Ammonia supply calculations are based on a 70% ammonia / 30% hydrogen blend by volume. This ratio permits flame speed and temperature consistency with natural gas and thus minimizes conversion hardware and engineering costs.

The ammonia demand necessary to decarbonize legacy power plants is recorded as a function of plant efficiency and output. Both phases examine CAPEX and OPEX calculations as a function of power output. The authors are actively deploying this method to support full-scale construction of phase one at a US customer location.