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Abstract Ammonia (NH3) is decomposed in the afterglow of an atmospheric pressure-nitrogen microwave plasma torch (MPT) for hydrogen production. And optical emission spectroscopy (OES) is employed in diagnosis to analyze characteristic molecular bands and determine rotational temperature using the Boltzmann plot method. The mechanism of chemical and joule heating and NH3decomposition in plasma afterglow is discussed by studying rotational temperature and concentration of excited species with respect to microwave power and NH3 flow rate. Additionally, the gas flow field distributed in the reaction chamber is numerically calculated using computational fluid dynamics (CFD). It is a principle to enhance effective collisions between NH3 molecules and the active species in the afterglow of N2 plasma for a high hydrogen production rate, which is materialized by optimizing the gas inlet position and NH3 flow rate and by introducing a metal rod against the afterglow in the reaction chamber to modify the gas flow field. The experimentally achieved results are as follows: hydrogen production rate of 544 L/h, energy yield of 274 L/kWh, and ammonia conversion rate of 86 %, respectively.
Niu et al. (Tue,) studied this question.