A review on ammonia blends combustion for industrial applications

Abstract

In response to the increasingly serious problem of climate change, the development of carbon-free fuels faces a significant opportunity in the background of global carbon emission reduction. Combustion of NH3 is an important part of building a low-carbon energy system. The utilization of NH3 to replace traditional fossil fuels is considered a frontier technology to achieve large-scale carbon emission reduction and is receiving increasingly widespread attention. Although combustion of NH3 has no CO2 emission, it also has serious limitations such as poor stability, low burning velocity and high NOx emission. This review composes various ways to enhance combustion of NH3. Oxygen-enriched combustion, plasma-assisted combustion, pre-cracking combustion and combustion with other reactive fuels can all significantly improve the combustion characteristics of NH3. The laminar burning velocity of pure NH3 and NH3 blends with other fuels, such as NH3/CH4 and NH3/H2, is reported. The pure NH3, NH3/CH4 and NH3/H2 emissions are discussed. Recent research results on the combustion of NH3 mixed with liquid fuels such as DME are summarized. Research on NOx emission reduction of gas turbines fueled by NH3, NH3/CH4 and NH3/H2 is presented. The analysis indicates that the most desirable combustion approach at present is rich-lean staged combustion. However, the equivalence ratio of the primary burning zone must be precisely controlled to achieve low NOx and unburned NH3 emissions. This review systematically elucidates possible approaches to address NH3 combustion barriers, and it provides a reference for future experimental and numerical investigations as well as practical industrial applications.