When black liquor is burned, a significant quantity of ash is produced. Some of the ash accumulates on the boiler tube surfaces, reducing the boiler heat transfer efficiency. Eventually, the boiler flue gas passages can become plugged, and as a consequence, the boiler has to be shut down and washed with water to clean out the passages. This unscheduled shutdown interrupts production and incurs financial costs to the mill. In order to maintain the uninterrupted operation of the recovery boiler, sootblowers are installed at strategic locations on the boiler to help remove fireside deposits and prevent the flue gas passages from plugging.