GB840687A - Improvements in tubulous vapour generating and vapour heating units - Google Patents

Abstract

840,687. Steam generators; superheaters. BABCOCK & WILCOX Ltd. Aug. 6. 1958 [Aug. 6. 1957], No: 24806/57. Classes 123(2) and 123(3) A steam generating unit comprises a vertical furnace chamber 12 which is fired, through a front wall 13, by a cyclone furnace 14 discharging into a secondary furnace chamber 15 and has an upper region leading to a lateral pass divided into a main upper pass 20 and a lower by-pass 22 both of which communicate with a gas turning zone 28 leading to a downpass 30. The front portion 93 of the roof 32 of the lateral by-pass 22 includes a spaced row of tubes 82 which are alternately arranged with tubes 84 to form a contiguous tube row along the rear portion 95 of the roof, the tubes 82, 84, connected at their front ends to a header 80, being united at the rear end of the roof by bifurcations to vertical tubes 83 which extend in spaced relation across an outlet 94 for the main pass 20. The tubes 83 are bent to form, alternately with a set of tubes 100, the roof 96 of the main pass 20. The tubes 100 extend the full length of the floor 24 of the by-pass 22, the front floor portion 106 of which includes the alternately arranged contiguous front portions of the tubes 84 which have vertical portions 97 leading down from the intermediate part of the roof 32. The floor tubes of the by-pass 22 are tack-welded to plates 88, 89, 92 carried by transom beams 108, 110 supported at their ends, in a conventional manner, upon upright convection superheater tubes 70, 75 which line the walls of the gas passes 20, 22. Small gaps, sealed, e.g. with strips of expansion material, not shown, are inserted in spaces between the edges of the bypass floor 24 and roof 32 and the corresponding wall tubes 70, 75. A damper 103, pivoted to inclined parts 101 of tubes 100, controls the passage of gas through the by-pass 22 and thus the amount of convection heat supplied to tube banks 158, 160 of reheat units accommodated in the main pass 22. Steam, generated in tubes 40, 48, 58 lining the walls of the furnace chamber 12 and in tubes 43 of a wall dividing off the secondary furnace chamber 15, flows from a steam and water drum 10, through connectors 73, to an inlet header 72 for the superheater tubes 70, 75. A lower wall header 76 for the latter is connected, by a line 78, to the header 80 which delivers steam, through the tubes 82, 84, to a return header 98 from. which it passes, through. the tubes 100, to an outlet header 102. The steam then flows, through connectors 124, to a lower wall header 120 supplying a tube row 116 which lines the front wall 118 of the downpass .30 and is connected to an upper wall header 122. A tube row 128, lining the roof 130 of the gas-turning space 28 and a rear wall 132 of the downpass 30, receives steam from the header 122 and passes it, through a lower wall header 134, in series through convection superheater tube banks 136, 138, 140 located in the downpass 30. Steam then passes successively through a radiant heat superheated platen 144, arranged in the upper region 18 of the furnace chamber, a spray attemperator 156, which may be subject to automatic control, and a secondary superheater tube bank 150 which is connected to a final discharge header 154. The tubes lining the furnace chamber 12 and the by-pass 22 have portions covered with refractory material shown, e.g. at 37. In a modification an inverted tube arrangement locates the by-pass 22 in the upper part of the lateral pass. The damper 103 may, in this case, be vertically slidable between the tubes 100, 116.