Ejector driven steam generator start up system

Abstract

A generating system is presented that includes a steam generator, a separator coupled to the generator, a supply providing feed water, a start-up system coupled to and receiving the feed water, and a recirculation system coupled to the start-up system. The steam generator operates in a plurality of operating modes. In one mode the steam generator generates a flow of steam and fluid. The separator separates the flow into components of steam and fluid. The recirculation system receives the feed water from the start-up system and provides a required flow to the steam generator during at least one mode. The recirculation system includes an ejector. The ejector induces a portion of the fluid from the separator into the recirculation system, mixes the induced fluid with the feed water to provide a recirculation flow, and the recirculation system provides the required flow to the steam generator including the recirculation flow.

1 . A steam generating system, comprising:
 a steam generator operating in a plurality of operating modes, in at least one of the plurality of operating modes the steam generator generating a flow of steam and fluid;   a feed water supply providing feed water;   a start-up system coupled to and receiving the feed water from the feed water supply; and   a recirculation system coupled to the start-up system, the recirculation system receiving the feed water from the start-up system and providing a required flow to the steam generator during at least one of the plurality of operating modes, the recirculation system includes an ejector, the ejector induces at least a portion of the fluid from the steam generator into the recirculation system, the ejector mixing the induced fluid with a portion of the feed water to provide a recirculation flow, and the recirculation system providing the required flow to the steam generator including the recirculation flow.   
     
     
         2 . The steam generating system of  claim 1 , wherein the recirculation system further includes a bypass valve and a block valve, the bypass valve and the block valve being selectively operated during the plurality of operating modes of the steam generator to provide the required flow and the recirculation flow to the steam generator. 
     
     
         3 . The steam generating system of  claim 2 , wherein when the steam generator is operating in a once-through operating mode, the bypass valve opens and the block valve closes to isolate the ejector and to provide the feed water from the recirculation system to the steam generator as the required flow. 
     
     
         4 . The steam generating system of  claim 2 , wherein when in a low load condition operating mode, the block valve opens and the bypass valve is selectively controlled such that the ejector induces the fluid from the steam generator, mixes the induced fluid with the feed water to form the recirculation flow and the recirculation system provides the required flow from the recirculation system to the steam generator including the recirculation flow. 
     
     
         5 . The steam generating system of  claim 4 , wherein the low load condition includes a start-up operating mode of the steam generator. 
     
     
         6 . The steam generating system of  claim 4 , wherein the low load condition includes operating modes below a minimum once-through load equal to a range of about twenty percent (20%) to about fifty percent (50%) of a full load flow of the steam generator. 
     
     
         7 . The steam generating system of  claim 1 , wherein the recirculation system further includes a throttling valve coupled to the ejector, the throttling valve receives the mixture of the induced fluid and the feed water and provides the mixture as the recirculation flow, the throttling valve controls the feed water pressure and flow through the ejector as loads vary during ejector operation. 
     
     
         8 . The steam generating system of  claim 1 , wherein at least one of the plurality operating modes of the steam generator includes a drain mode, the drain mode including isolating the ejector and operating the recirculation system such that the required flow to the steam generator is provided by the feed water from the feed water supply. 
     
     
         9 . A steam generating system, comprising:
 a steam generator operating in a plurality of operating modes, in at least one of the plurality of operating modes the steam generator generating a flow of steam and fluid;   a separator coupled to the steam generator, the separator receiving the steam and fluid flow and separating components of steam and fluid from the steam and fluid flow;   a feed water supply providing feed water;   a start-up system coupled to and receiving the feed water from the feed water supply; and   a recirculation system coupled to the start-up system, the recirculation system receiving the feed water from the start-up system and providing a required flow to the steam generator during at least one of the plurality of operating modes, the recirculation system includes an ejector, the ejector induces at least a portion of the fluid from the separator into the recirculation system, the ejector mixing the induced fluid with the feed water to provide a recirculation flow, and the recirculation system providing the required flow to the steam generator including the recirculation flow.   
     
     
         10 . The steam generating system of  claim 9 , wherein the recirculation system further includes a bypass valve and a block valve, the bypass valve and the block valve selectively operated during the plurality of operating modes of the steam generator to provide the required flow and the recirculation flow to the steam generator. 
     
     
         11 . The steam generating system of  claim 10 , wherein when the steam generator is operating in a once-through operating mode, the bypass valve opens and the block valve closes to isolate the ejector and to provide the feed water from the recirculation system to the steam generator as the required flow. 
     
     
         12 . The steam generating system of  claim 10 , wherein when in a low load condition operating mode, the block valve opens and the bypass valve is selectively controlled such that the ejector induces the fluid from the steam generator, mixes the induced fluid with the feed water to form the recirculation flow and the recirculation system provides the required flow from the recirculation system to the steam generator including the recirculation flow. 
     
     
         13 . The steam generating system of  claim 12 , wherein the low load condition includes a start-up operating mode of the steam generator. 
     
     
         14 . The steam generating system of  claim 12 , wherein the low load condition includes operating modes below a minimum once-through load equal to a range of about twenty percent (20%) to about fifty percent (50%) of a full load flow of the steam generator. 
     
     
         15 . The steam generating system of  claim 9 , wherein the recirculation system further includes a throttling valve coupled to the ejector, the throttling valve receives the mixture of the induced fluid and the feed water and provides the mixture as the recirculation flow, the throttling valve controls the feed water pressure and flow through the ejector as loads vary during ejector operation. 
     
     
         16 . The steam generating system of  claim 9 , further including a downcomer conduit coupling the separator and the recirculation system, and wherein the recirculation system further includes a check valve providing one way flow from the downcomer conduit to the ejector. 
     
     
         17 . The steam generating system of  claim 16 , further including a flash tank coupled to the downcomer conduit through a flash tank valve, wherein when the steam generator is operating in a once-through operating mode, no fluid returns from the downcomer conduit and no flow is provided to the flash tank. 
     
     
         18 . The steam generating system of  claim 9 , wherein at least one of the plurality operating modes of the steam generator includes a drain mode, the drain mode including isolating the ejector and operating the recirculation system such that the required flow to the steam generator is provided by the feed water from the feed water supply.