GB907192A - Improvements in or relating to forced flow once-through boilers - Google Patents

Abstract

907,192. Forced-flow steam boilers. BABCOCK & WILCOX CO. May 15, 1959 [May 16, 1958], No. 16743/59. Classes 123 (2) and 123 (3). In a forced-flow once-through boiler, designed for oil or gas firing and having a high output of steam at high pressure and which may be adapted to operate at super-critical temperatures and pressures, the lower end of each of the wall tubes lining the front, back and side walls 12, 14, 16 of an upright furnace chamber 10 includes two upflow sections C<SP>1</SP>, C<SP>3</SP> which are interconnected by a downflow section C<SP>2</SP> located behind them within a wind-box 75. The tube sections C<SP>1</SP>, C<SP>2</SP>, C<SP>3</SP> have the same diameter which is less than upflow extensions D. The wall tubes are supplied from an economiser 66 through pipes 77 fitted with flow resistors 97 the upper headers of the wall tubes all being connected to a T-shaped header 100 having a transverse branch 100A. Contiguous tubes 104, leading from the header branch 100A and forming the roof of the chamber 10 and a lateral pass 22 leading to a downpass 24, are connected to a transverse header 102 tubes from which supply the upper headers of tubes 118, 56 forming vertical partition walls to provide parallel gas passages 46, 52 and 48, 54. The transverse header 102 also supplies the upper ends of tubes 138, 128, 130 which line respectively the roof, the front and rear walls 26, 28 and the side walls 30 of the down pass 24. The lower ends of the tubes 128, 130, 138 and the lower ends of the partition tubes 56 are connected to a rectangular header 112A ... 112C which extends around the inner face of the downpass 24 and has a cross limb 142. The tubes of a three-part first section of a primary superheater 58, housed in the gas passage 52, lead upwards from opposite branches 112A, 112B of the rectangular header 112A. . . 112C and are connected at their opposite ends to a common header 144. Steam is passed from the latter successively in counter and parallel gas-flow directions through a second section 60 of the primary superheater heated in the gas passage 46 and through a tube 150 leading to a final section 38 of the primary superheater accommodated in the furnace chamber 10. The superheater section 38 comprises tubes 154 in the form of panels E, F which are spaced from one another and from the furnace walls 12, 14, divide the furnace chamber 10, and extend between upper and lower headers 156, 158 and 155 respectively the latter having a cross arm 155A to provide connections to the upper headers of the first section 44A of a secondary superheater 44 which is connected to a second section 44B leading to a steam outlet pipe 172. The secondary superheater sections 44A, 44B extend across both passages 46, 48 of the lateral pass. Series-connected primary and secondary sections 62, 64 of a reheater are housed respectively in the gas passages 54, 48 the section 64 having an outlet pipe which extends parallel to the steam output pipe 172. The downpass passages 52, 54 lead respectively to dampercontrolled outlet ducts which converge upstream of a heater, not shown, which heats combustion air supplied to a duct leading to the wind-box 75.