Slag Removal

the removal from steam boiler fireboxes of residues resulting from the combustion of solid fuels.

A distinction is made between fireboxes in which the slag is removed in thin streams in the molten state into a vat with water and fireboxes in which solid slag drops from the firebox hopper into a bin, from which it is periodically removed through a gate. Usually the slag is subsequently transported together with the fly ash (seeASH REMOVAL) collected by gas-purification devices. In older boilers the slag and ash were removed by cars. In modern electric power plants slag is ordinarily removed by a hydraulic system. The slag is transferred to a slag-washing shaft and then (in the case of coarse slag) to a grinder, from which it passes through a grate and metal catchers into dredger pumps or to hydraulic ejector pumps, which transfer the slurry (a mixture of slag and ash with water) to an ash dump. The two materials are often removed individually—the slag by a hydraulic system, and the ash by a pneumatic system. The vacuum removal of ash and slag is used in small boilers.