the pressurized fluidized bed combustion (PFBC), and the
circulating fluidized bed combustor (CFBC).
In order to improve the performance of the FBC, a vortexing
fluidized bed combustor (VFBC), an integration of bubbling
fluidized bed and cyclone, was developed early in the 1970s.18
The first pilot scale VFBC was constructed and operated by
Korenberg.19 It was modified and renamed by Nieh and Yang20
later. The concept of the VFBC is to establish a vortexgenerating
system by injecting the second air tangentially into
the freeboard to increase the combustion intensify, the calcium
utilization, and the turndown capability. The advantages of low
pollutant emissions and high combustion efficiencies by operating
a VFBC have been demonstrated for combustion of waste
tires in the previous study. We have reported the NO emission
in a vortexing fluidized bed combustor in our recent paper.21 In
this paper, the inner diameter of the combustor, including the
combustion chamber and the freeboard, is 0.45 m, and it is found
that the excess air is the most important factor to dominate NO
emission and that NO emissions can be reduced by adding
soybean to the fuels. However, this paper has not studied the
characteristics of the N2O emission.