Review of Fundamental Study on Ammonia Direct Combustion in Industrial Furnaces

Abstract

There are sever issues on increasing amount of CO₂ emission in the world. Many studies are devoted on alternative fuels. One potential candidate is the utilization of hydrogen energy which can realize a low-carbon and hydrogen-based society. Ammonia, which is zero emission of CO₂ and useful for hydrogen energy, might play an important role as a clean energy carrier and also can be burned directly as a fuel. For direct combustion of ammonia in industrial furnaces, there were three issues which were low burning velocity, weaker radiative heat flux and a huge amount of NOX emission compared with the combustion of methane. In this review, we introduce those solutions in our studies to overcome these three disadvantages of ammonia direct combustion in an industrial furnace. Firstly, the laminar burning velocity of ammonia, which is about 8 cm/s originally, could be improved with the increase of O₂ concentration [1, 2]. Secondly, radiative heat flux under the condition of the oxygen enriched (30 vol.%) ammonia non-premixed flame formed in a 10 kW test furnace was improved more than that of the methane/air non-premixed flame [3]. Thirdly, Air staged combustion could reduce the NOx emissions due to generated unburned-ammonia intentionally in the upstream of the furnace which played an important role in reduction action.