GB1294120A - Once-through vapour generator - Google Patents

Abstract

1294120 Vapour generators FOSTER WHEELER CORP 31 Dec 1969 [28 Jan 1969] 63573/69 Heading F4A A vapour generator, Fig. 1, comprises a furnace 12 formed by parallel tube wall panels 14, 16 which define a first upward flow pass and in series flow relationship therewith parallel tube wall panels (18), (20), Fig. 2 (not shown), defining a second downward flow pass. The generator is heated by gas, oil or coal fired burners E, the gases from which pass through an exit end C to a heat recovery area D which is divided into front and rear passes 48, 50 respectively by a partition wall 36 and contains superheaters 55, 30, 52, a reheater 54 and economizer 56. The gases flow through an air heater H to heat incoming combustion air for the burners E. Liquid to be vaporized leaves economizer 56 and via a downcomer 58, Fig. 3, passes to headers (60), (62) and flows up the tube walls 14, 16 to leave through headers 60a, 62a. A fan-mix arrangement, Fig. 5 (not shown), comprising a horizontal manifold (92) and numerous connections (96), (98), mixes and disperses the flow of liquid before it flows through a downcomer 66 to headers (68), (70). The liquid flows up the sidewalls (18), (20) through a fan-mix arrangement 72 formed by manifolds 74, 76 to the heat recovery area D. Here it flows through tube walls 36, 40, 44, 46 and sidewalls 38, 38a of a portion 32 formed by a screen of tubes 28 to the generator roof 22, heat recovery area rear wall 42 and superheaters 52, 55, 30 respectively. Part of the flow from downcomers 58, 66 is fed to a buffer circuit, Fig. 2A (not shown), formed by tube panels 80, 82, 84, 86 in the corners of the furnace 12. The buffer circuit partly reduces the stresses in the tubes due to differential thermal expansion by establishing a temperature between that of the first and second passes. To maintain high flow rates and reduce the pressure drop in the furnace the latter is divided into a lower highabsorption zone B<SP>1</SP>, Fig. 4A (not shown), and an upper lower temperature zone B<SP>11</SP>, the tube diameters increasing at a point 2/3 the height of the furnace. In a second embodiment, Fig. 8 (not shown), a larger furnace totally oil fired has the side walls divided into second and third passes (110), (112) with a mixing header (114) therebetween. In a final embodiment, Figs. 11, 12 (not shown), a division wall (120) is provided between front and rear walls (122), (124), the liquid flowing via downcomers (130), (132) to both the walls (122), (124) and the division wall (120). The embodiment of Figs. 11, 12 may be incorporated into that of Fig. 8. Graphs of temperature es. enthalpy, Figs. 9, 10 (not shown), are also described.