GB725583A - Improvements in or relating to tubulous vapour generating and vapour heating units - Google Patents

Abstract

725,583. Water-tube steam boilers; steam superheaters. BABCOCK & WILCOX, Ltd. March 6, 1953 [March 6, 1952], No. 6352/53. Classes 123 (2) and 123 (3). A forced circulation water-tube steam boiler comprises a furnace 1 which is fired by pulverised fuel burners 2 and 3 and which is lined with studded, refractory-covered, superheater tubes 12, 17 and 57. The furnace is operated at ash-melting temperature, the slag which deposits on the furnace walls, &c., draining quickly therefrom and passing away through an outlet 35 in the furnace floor 10. The hot gases flow from the furnace through a slag screen 31 of superheater tubes and pass upwardly through a radiation chamber 39 lined with bare steamgenerating tubes the surface temperature of which, at least in the lower part of the chamber, is kept below 320 ‹C. so that any slag adhesions which may occur can be easily dislodged. The gases then flow successively through a lateral pass 41 and downflow and upflow passes 42 and 45 locating a convection superheater, a reheater and an economiser and pass to the stack through air heaters 46 and 48. In the lower part of chamber 39 are located auxiliary burners 52 and associated combustion air nozzles 53 which are used when starting up to avoid damage to the furnace superheater tubes. Burners 52 may also be used during operation to cater for variations in the demand on the unit, the burners 2 and 3 then being regulated in dependence on the final steam temperature.