GB1089383A - Improvements in or relating to starting once-through vapor generators - Google Patents

Abstract

1,089,383. Raising steam in forced flow once through generators. FOSTER WHEELER CORPORATION. April 20, 1965 [April 24, 1964], No. 16579/65. Heading F4A. A once through forced flow supercritical or subcritical vapour generator is started up by establishing a 30% full load fluid flow through the boiler circuitry 12, 14, 16 and the primary and/or platen superheater 22, and with the main flow line stop valve 52 being closed, through a first by-pass loop line 50 to a vapour/ liquid separator 48 whose pressure is set at 1500 p.s.i. to maintain a like boiler circuitry pressure by means of valves 72, 74 in outlet lines 68a, 68b, the output from the separator passing through the lines 68a, 68b to the condensate system for re-use as boiler feed water. As heating from the burners at 15% full load firing rate continues, steam flashing in separator 48 is fed via lines 60, 60a, 60b and 44a to the gland seal regulator 62, de-aerator 38 and high pressure feed water heaters 44, 42. Once a separator pressure of 1500 p.s.i. is reached, valve 58 in vapour line 60 to the inletof finishing superheater 24 is cracked open to supply warming steam to the main steam line, the steam from the finishing superheater outlet 24a by-passing the turbines through by-pass line 78. When 5% full load steam flow becomes available from the separator a portion is passed through line 60 and finishing superheater 24 to the turbine throttle by-pass control valve 90 (Fig. 2, not shown) to warm and roll the turbine, the excess passing to the condensate system through lines 60a, 60b, 44a and 78. To load the turbines valve 58 is opened wide to increase the turbine load to 15% at 1500 p.s.i. throttle pressure, now under control of the governor valves 88 (Fig. 2, not shown) and when the entire 30% full load flow in the boiler circuitry is vaporized, main flow line valve 52 is opened, valve 58 in vapour line 60 is closed and pressure reducing valve 77 in the second by-pass loop line 75 is opened to by-pass a portion of the vapour generated around the turbines. The amount by-passed is reduced as turbine load is increased, by throttling valve 77. At 30% full load flow all the boiler circuitry flow passes through the main steam line and the second by-pass loop line 75 is also shut off. Loading to full load is then achieved through control of the governor valves 88, the feed water supply and the combustion conditions; The system throughout may be under automatic control in response to the load demands.