Characteristics of NOx decompositon in FFCC process

摘要

Estimating the characteristics of decomposing NOx in oxidants from the gas turbine in the FFCC (fully-fired combined cycle) process, we conducted bench-and pilot-scale tests, using gases, oils and pulverized coal. We simulated NOx and O_2 concentration in the oxidant of the actual gas turbine exhaust. NO gas was added to the combustion air and the O_2 concentration of the combustion air was adjusted by recirculating the flue gas from the test furnace. The results showed that fuel oils have the highest efficiency for NOx decomposition among the fuels tested. While comparing NOx decomposition during gas firing using gun-type and multi-spud type burner nozzles, we proved that the fuel mixing property significantly affected NOx decomposition in flames. Staged firing enhanced the decomposition of NOx in the oxidants. Its efficiency reached 90percent both for fuel oils and pulverized coal on the bench-scale (1.2MWt) test. However, the pilot-scale (12MWt) test showed 60percent NOx decomposiiton in fuel oil firing. Accordingly, we noted that the capacity of the burner also influenced NOx decomposition significantly. This was mainly due to the difference in local stoichiometry caused by the mixing property of fuels with the oxidant, which was directly influenced by the strength of the turbulence dependent on the burner capacity.