Limestone addition to a coal-ยฎred ยฏuidized bed combustor usually results in an increase in NO/NO x emissions and a decrease in N 2 O emissions. This observation has been explained in the literature by the effect of limestone on: (i) the conversion of coal volatile-N to NO/NO x and N 2 O; (ii) the decomposition of N 2 O; and (iii) the pool of H, OH and/or O radicals due to sulphur capture. Since char-N is also an important source of NO/NO x and N 2 O under ยฏuidized bed combustion conditions, any effect of calcined limestone on the conversion of char-N to NO/NO x and N 2 O can also contribute to the above observation. The effect of calcined limestone on the conversion of volatile-N species, i.e. NH 3 and HCN has been well documented. However, so far few studies have studied the effect of limestone on the conversion of char-N under ยฏuidized bed combustion conditions. In this study, a series of batch-type char combustion tests was carried out in a bench-scale bubbling ยฏuidized bed combustor with different bed materials. These tests reveal that in addition to reducing N 2 O emissions from char combustion, calcined limestone also enhances the conversion of char-N to NO/NO x similar to the case of volatile-N. Possible reaction mechanisms to explain the experimental results of char combustion tests have been discussed.