Patent GB-1116706-A (GB)
Title: Startup system for a steam actuated electric generator
IPC: F22B29/12
Filed: 1966-04-12
Abstract: 1,116,706. Raising steam in forced flow boilers. ELECTRODYNE RESEARCH CORPORATION. 12 April, 1966 [30 April, 1965], No. 15989/66. Heading F4A. A forced flow steam generator 1, includes evaporator and super-heater heating conduits 4, 5 connected in series and leading to a superheater steam outlet 3. From here the steam passes through high pressure turbine 8, reheater 10 and the reheat turbine 13 to, a condenser 16. Water from the condenser 16 is pumped by pump 21 through water purification equipment 22, low pressure feed water heater 24, and deaerator 26 to de-aerator storage tank 30. The feed water pump 33 draws water from the deaerator storage tank 30 and passes it through a high pressure feed water heater 36 on its way to inlet 2. The feed water flow to the generator 1 is regulated in co-ordination with the firing rate by control valve 35. During start up, with valves A and B initially closed, a circulation flow is established through the evaporator heating conduits 4, conduit 42, one side of heat exohanger 43, and pressure control valve R in conduit 44 to flash tank 45. Liquid from flash tank 45 under the action of level controller 58 passes through conduit 46, and valve J to compartment 47 of the de-aerator storage tank 30. The water from compartment 47 may pass directly into the remainder of the storage tank 30 or alternatively pass through conduit 48 and valve L to steam condenser 16 to be purified in the equipment 22 and de-aerator 26 before being recycled through the evaporator heating conduits 4. Firing is commenced, and the steam separated in flash tank 45 is supplied to the deaerator 26 and the high pressure feed water heater 36. Surplus steam is passed to condenser 16 through valve P controlled by the flash tank pressure controller 52. Next, valve V in conduit 53 is opened, to pass steam from the flash tank 45 through superheater heating conduits 5, which steam is then discharged to atmosphere or to condenser 16 through valve 54. When the cycle water has been completely purified, turbine stop valve 7 is opened and warming steam passed through the high pressure turbine 7, the reheater 10 and the reheat turbine 13. Throttling valve B in line 55 is then gradually opened to lead some fluid directly from the evaporator heating conduits 4, through conduit 56 in heat exchanger 43, directly to the superheater heating conduits 5, thereby by-passing the flash tank 45. The fluid flowing through conduit 56, being at a lower pressure, absorbs heat from the fluid flowing through the heat exchanger 43 and passing to the flash tank 45, thereby " drying " the steam flowing directly to the superheater heating conduits 5, and by-passing the flash tank 45. As the flow to the superheater heating conduits 5 through valve B is increased, the flow through valve V from the flash tank 45 is reduced, and the firing rate of burners 41 is increased. Finally, a valve A is opened to allow the flow to pass directly from the evaporator heating conduits 4 to the superheater heating conduits 5, and valve B is closed. In a modification conduit 53 and valve V may be abolished, the initial flow to the superheater heating conduits 5 being through valve B. Alternatively, valve B may comprise the main flow circuit between the evaporator heating conduits 4 and the superheater heating conduits 5, valve A being eliminated. Again fluid flow from evaporator heating conduits 4 to superheater heating conduits 5 could be in parallel flow through both valves A and B to regulate the heat content of fluid entering the superheater heating conduits 5 to the desired value. In further modifications the start up heat exchanger (43) may be situated upstream of valve (A) in the main flow conduit (Fig. 2), it may comprise an extension of evaporator heating conduits (4) and receive heat from the burners (41, Fig. 3), valve (B) may be sited in the main flow line (Fig. 4), the take-off points to the conduits passing fluid through valves (B, R) may have further heat absorbing surfaces (4a) between them (Fig. 5), the start up system may be applied to a steam generator with recirculation (Fig. 6), and a portion of the superheater heating conduits (5) may also be by-passed by steam from the valve (B) (Fig. 7). Some of the conduits 4 may comprise part of the superheating surface of the generator, or some of the conduits 5 may comprise part of the steam generating surfaces.