2019 Volume 61 Issue 198 Pages 283-288
AIST carried out demonstration tests with the aim to show the potential of ammonia-fired power plant. 50kW class turbine system firing kerosene is selected as a base model. A standard combustor is replaced by a prototype combustor which enables a bi-fuel supply of kerosene and fuel gas. The gas turbine started firing kerosene and increased its electric power output. After achievement of stable power output, ammonia gas was started to be supplied and its flow rate increased gradually. Ammonia combustion in the prototype bi-fuel combustor was enhanced by supplying hot combustion air and by modifying the air inlets. However, the exhaust gases from the ammonia flames had high NOx concentrations. NOx removal equipment using selective catalytic reduction can reduce NOx emission levels to below 10 ppm from more than 1,000 ppm (converted value of NOx to 16% O2) as already reported. However, downsizing of NOx removal equipment should be achieved for practical use. Therefore, a low NOx combustor was developed. We modified the combustor to the rich-lean burning method and found the condition that the NO emission can be reduced to less than half, but the NOx emission reduction was insufficient as compared with the small-scale flow test at the lab scale. Therefore, each part of the combustor was redesigned so that mixing of fuel and air improves uniformity. Low-NOx combustor (Step2) was designed using knowledge of Prototype bi-fuel combustor for ammonia (Step0) and Low-NOx combustor (Step1). As a result, we found a condition that the NO emission can be reduced to 200ppm or less as compared with before redesigning for rich-lean combustion.