With horizontal bias combustion burners, experiments have been carried out on a 670 th(-1), corner-fired, pulverized-coal fired boiler burning bituminous coal. At 200 MWe load, the furnace excess O-2 remains stable. The different horizontal fuel biases are obtained by changing the tilt angle of all the Louvre enrichers' regulating blades. The tilt angles of the blades are 0, 15, 24, 32degrees; the result is that the enriching ratios of the fuel-rich primary air increase from 2.2 to 2.6 at No. 2 corner, and from 1.2 to 4.2 at No. 3 corner. The gas temperature increases in the burner region. The application of the 3 horizontal bias combustion burners results in a reduction in NOx formation from 545.7 mg Nm(-3) (O-2 = 6%) to 287.9 mg Nm(-3), and a substantial reduction in carbon in ash content from 5.24 to 2.48%. The boiler operated stably at a load of 80 MWe without auxiliary fuel oil. Copyright (C) 2004 John Wiley Sons, Ltd.