GB967580A - Steam generating unit - Google Patents

Abstract

967,580. Regulating steam temperature in boilers. RILEY STOKER CORPORATION. March 18, 1963 [March 19, 1962], No. 10577/63. Heading F4A. In a steam generator comprising a vertical combustion chamber fired by burners in the lower part thereof and having a lateral gas outlet in the upper part of one wall to a pass locating a convection superheater, steam temperature is controlled by positioning the main stream of combustion gases within the chamber by means associated with the burners so that it flows upwardly against the gas outlet wall at low loads or against the opposite wall, from which platens of water tubes project, at high loads or is located at an intermediate position between the walls at intermediate loads, the temperature of the gases entering the convention pass thereby being controlled to maintain the superheat temperature at a preset value over the range of load. In the form shown the generator has an upright, tubelined combustion chamber 18 having a front wall 15 from which platens 75 of generating tubes project and a rear wall 16 provided at its upper part with a nose 33 forming the floor of a lateral pass 34 locating pendent superheater and reheater sections 62, 69 and leading to parallel down passes 37, 38 respectively locating primary superheater and reheater sections 61, 68, the gas flow through the down-passes being proportioned by dampers whereafter the gases combine for flow through an air heater 42 to a stack 44. At their lower portions the walls 15, 16 are provided with abutments 21, 23 on the lower surfaces of which openings are provided for burners 22, 24 respectively, the burners firing into a high temperature cell 19. The inclination of combustion air injection for the burners 22, 24 is respectively controlled by vanes 83, 85 and 88, 91, the vanes being set by actuators 96, 97 in response to variations of superheat and reheat temperature from a preset value, signals representative of these temperatures being received by a controller 101 from pick-offs 113, 115 respectively disposed in the superheater and reheater outlet headers. At low loads when the superheat temperature tends to fall below the desired value, the controller sets the vanes 88, 91 downwards and the vanes 83, 85 upwards causing the main stream of combustion gases to ascend against the rear wall 16 out of contact with the platens 75. The gases thus reach the convection superheater at a high temperature to maintain the steam temperature at the desired value. At high loads the vanes are set at opposite inclinations to cause the gases to flow through the platens 75, reducing their temperature and counteracting the tendency for steam temperature to be above the desired value at these loads. At intermediate loads the gas stream is positioned at the appropriate location between the front and rear wall. At all loads the gas proportioning dampers are also adjusted to give the correct relationship between superheat and reheat temperatures and at the highest loads spray attemperation may be used to reduce the superheat temperature.