Nitrogen oxides are one of the most significant pollution sources during coal combustion. This experimental study was conducted in a 15 kW

th

lab-scale pressurized fluidized bed (inner diameter=81-100 mm

H

=2100 mm) firing with bituminous coals. The effects of operating parameters

including bed temperature (800℃-900℃)

operating pressure (0.1-0.4 MPa)

excess air level (16%-30%) and flow pattern on NO

x

and N

2

O emissions were systematically studied during the tests. During each test the interaction effects of all the operating parameters were properly controlled. The results show that most operating parameters have an opposite effect on NO

x

and N

2

O emissions

and the N

2

O emissions mainly depend on the bed temperature. Increasing the operating pressure can significantly suppress the fuel-N conversion to NO

x

but enhance its conversion to N

2

O. With the rise of the excess air level and fluidization number

NO

x

emissions grow distinctly while N

2

O emissions remain almost unchanged. Total nitrogen oxide emissions increase with the bed temperature while

decrease with the operating pressure.