GB974398A - Steam generating unit - Google Patents

Abstract

974,398. Water-tube steam boilers; regulating steam temperature. RILEY STOKER CORPORATION. Jan. 14, 1963 [Jan. 15, 1962], No. 1552/63. Heading F4A. In a steam boiler having an upright combustion chamber fired by burners mounted at the lower portions of the front and rear walls, the upper region of the chamber is divided into three gas passes by vertical baffles parallel to these walls, a reheater being disposed in the first and middle pass whilst a superheater is disposed in the middle and third passes, the reheat and superheat temperatures being maintained at a preset value over a wide range of loads by positioning the main stream of hot gases in relation to the inlets to the passes by means associated with the burners. In the form shown, the boiler has a vertical combustion chamber 18 lined with steam generating tubes extending between lower headers 27, 29 and a steam and water drum 25. On the front and rear walls 15, 16 of the chamber the tubes are bent inwardly to form abutments 21, 23 on the undersides of which are located burners 22, 24. The burners fire into a high temperature cell 50 and are respectively provided with adjustable vanes 76, 78 and 82, 84, the setting of which controls the position of the main stream of hot gases between the front and rear walls of the chamber 18. At the top of this chamber baffles 34, 35 divide the gas flow path into three passes 114... 116, a superheater 62 being located in the rear and middle passes 115, 116 and whilst a reheater 72 is located in the front and middle passes 114, 116. Radiant reheater and superheater platens 67, 57 are disposed in the chamber 18 below the passes 114, 115 respectively. The gases leaving the passes 114 ... 116 combine in an open space 119 and flow laterally through an offtake opening 118 and then downwardly in two passes 38, 39 respectively containing an economizer 123 and a primary reheater 71, the gases being proportioned between the passes 38, 39 by dampers 42, 43. The gases then recombine for flow through an air heater 44 to the stack 45. Steam from the drum 25 passes successively through tubes lining the back passes, the radiant superheater 57, a desuperheater 59 and the convection superheater 62 to an outlet header 63. Steam for reheating enters a header 65 and flows serially through the reheaters 67, 71, 72 to an outlet header 70. Temperature pick-offs 103, 105 respectively disposed in the headers 63, 70 transmit signals representative of superheat and reheat temperature to a controller 91 which causes the burner vanes 78, 84 to be adjusted to position the hot gas stream between the superheat and reheat sides of the chamber 18. Thus, at high load when heat transfer for reheating must be high, the stream is positioned against the wall 15. As the load is reduced the controller moves the stream across the chamber until at low load it is positioned against the wall 16. Temperature correcting adjustments are simultaneously made to the gas proportioning dampers 42, 43, the water injection rate to the desuperheater 59 and the air supply to the burners.