Grate-fired two-pass natural circulation boiler - has furnace restriction forming cross-pass housing superheater; fully gas-tight roof

摘要

The grate-fired two-pass natural circulation boiler is esp. for applications with a proportionately high evaporation-heat requirement. Evaporation surface, functioning convectively, is therefore provided in the second pass and a restriction is fitted near the top of the furnace. This restriction (8) is formed by a gastight welded wall of tubes bent out of the furnace (10) backwall (9) plane; the top header (12) for these tubes supports the partition between the passes facing the evaporation surface (4), and straight (cooled) tubes (11) in the backwall plane. The superheater (15) is suspended in the cross-pass (14); its in- and outlet connections (24,25) run through a gastight closure (22) in the gap (21) between the first- and second-pass roof tube walls (19,20).