The paper describes the activities undertaken to improve the operation of a typical brown coal burner (firing about 35 t/h brown coal) used for the top fired 150 MW(e) Units of the Niederaussem Power Plant of RWE Energie A.G..

In order to select the suitable burner modifications to improve the fuel burnout and reduce the NOx emissions, a series of tests was performed in a model burner (of 250 kg/h firing capacity) at the 1.2 MW(th) pulverized coal research facility of RWE Energie KF/FS (R + D dept.).

The model burner was designed and constructed to simulate the operation of the typical industrial one taking into account the restrictions of applicability of the similarity analysis for the investigation of pulverized coal combustion.

After a series of experiments where the different operating parameters were varied, the conclusions from 14 different flame investigations indicated that:
The effects of swirl on the early ignition and the burnout improvement are intensified when increasing the momentum ratio between the secondary and the primary stream at the burner's outlet.

On the specific burner configuration values of the a.m. momentum ratio higher than 1.4 divided by 1.5 lead to improved burnout conditions and to the reduction of the CO emission without increasing the NOx emissions.

The successful scaling of the model burner with respect to the original is pro;ed from comparative measurements in the test facility and in the 150 MW(e) boiler.

Concrete proposals were made for the industrial scale burner on the basis of these conclusions.

The proposals were applied and tested successfully in a single burner and in all operating burners of a brown coal fired boiler in the Niederaussem power station.

Keywords : brown coal combustion, industrial boilers, emissions