Once-through steam generator recirculating startup system

Claim 2

A once-through vapor generator comprising a main flow path including, in series flow relatIonship, vapor generating and superheating surfaces; a bypass system connected with said main flow path including flash tank means therein; a main boiler feed pump for supplying liquid to said vapor generating surface, and pressure reducing means to reduce the pressure of the flow in said bypass system, the improvement comprising liquid conduit means connecting said bypass system flash tank means with the suction side of main boiler feed pump to transmit liquid flow from said flash tank means to said suction side; booster feed pump means upstream of the liquid conduit means to transmit makeup flow to the feed pump suction side; further including branch conduit means to transmit swell liquid from said flash tank means to the generator condenser.

Claim 3

The generator of claim 1 wherein the booster feed pump is connected to receive liquid from the generator deaerator storage tank.

Claim 4

The generator of claim 2 including a valve in said branch conduit means responsive to liquid level in the bypass system flash tank.

Claim 5

The generator of claim 3 including a vapor return line from said flash tank means to at least some of said superheating surfaces, valve means therein, and valve controlled vapor branch lines between said flash tank means and the generator condenser, gland seal regulator and deaerator, the valves in said vapor return line, and branch lines being pressure controlled.

Claim 6

The generator of claim 4 including check valve means between said booster pump means and the point of connection of the flash tank means with the suction side of the main boiler feed pump.

Claim 7

The generator of claim 3 wherein said valve in the branch conduit means can be made responsive to pressure in the flash tank.

Claim 8

The generator of claim 4 including burners and control means therefor, part of said control means comprising means responsive to the pressure in the flash tank to limit the flash tank pressure to a predetermined amount by controlling firing rate.

Claim 9

A once-through vapor generator comprising a main flow path including, in series flow relationship, vapor generating and superheating surfaces; a bypass system connected with said main flow path including flash tank means therein; a main boiler feed pump for supplying liquid to said vapor-generating surface; and pressure-reducing means to reduce the pressure of the flow in said bypass system; the improvement comprising liquid conduit means connecting said bypass system directly with the suction side of said main boiler feed pump to transmit liquid flow from the flash tank means to said suction side; booster feed pump means upstream of the liquid conduit means to transmit makeup flow to the feed pump suction side; first valve controlled branch conduit means to transmit liquid flow from the flash tank means to a heat sump, and second valve controlled branch conduit means to transmit vapor flow from the flash tank to the heat sump; said first and second branch conduit means first and second valves being responsive to liquid level in the flash tank and pressure in the flash tank, respectively.

Claim 10

A once-through vapor generator comprising a main flow path including, in series flow relationship, vapor generating and superheating surfaces; a bypass system connected with said main flow path including flash tank means therein; a main boiler feed pump for supplying liquid to said vapor-generating surface; and pressure-reducing means to reduce the pressure of the flow in said bypass system; the improvement comprising liquid conduit means connecting said bypass system directly with the suction side of said main boiler feed pump to transmit liquid flow from the flash tank means to said suction side; booster feed pump means upstream of the liquid conduit means to transmit makeup flow to the feed pump suction side; first valve controlled branch conduit means to transmit liquid flow from the flash tank means to a heat sump, and second valve controlled branch conduit means to transmit vapor flow from the flash tank to the heat sump; said first and second branch conduit means first and second valves being responsive to liquid level in the flash tank and pressure in the flash tank, respectively.

Claim 11

The generator of claim 8 including burner means, control means therefor, said control means being responsive in part to pressure in the flash tank means.

Claim 12

The generator of claim 9 wherein said valve means responsive to liquid level in the flash tank can be made responsive to pressure in the flash tank.

Claim 15

The method according to claim 11 wherein excess swell liquid and excess vapor only are transmitted to the Generator heat sump.

Claim 16

The method of claim 12 wherein the excess vapor amount is minimized by controlling the firing rate of the generator.