Start-up system for a once-through horizontal evaporator
View Patent ↗Disclosed herein is a once-through evaporator comprising an inlet manifold; one or more inlet headers in fluid communication with the inlet manifold; one or more tube stacks, where each tube stack comprises one or more substantially horizontal evaporator tubes; the one or more tube stacks being in fluid communication with the one or more inlet headers; where one or more tube stacks are used for a start-up of the once-through evaporator; one or more outlet headers in fluid communication with one or more tube stacks; a separator in fluid communication with the one or more outlet headers; a first flow control device in fluid communication with the separator and at least one of the tube stacks used for startup; a second flow control device in fluid communication with a superheater to bypass the separator and at least one of the tube stacks used for startup; and a controller for controlling the actuation of the first and second flow control devices in response to a parameter of the evaporator.
1. A once-through evaporator comprising:
an inlet manifold;
one or more inlet headers in fluid communication with the inlet manifold;
one or more tube stacks, where each tube stack comprises one or more substantially horizontal evaporator tubes; the one or more tube stacks being in fluid communication with the one or more inlet headers; where one or more tube stacks are used for a start-up of the once-through evaporator;
one or more outlet headers in fluid communication with one or more tube stacks;
a separator in fluid communication with the one or more outlet headers;
a first flow control device in fluid communication with the separator and at least one of the tube stacks used for start-up;
a second flow control device in fluid communication with a superheater and at least one of the tube stacks used for startup to bypass the separator; and
a controller for controlling the actuation of the first and second flow control devices in response to a parameter of the evaporator.
2. The once-through evaporator of claim 1 , wherein the controller is a thermal controller that provides a signal indicative of the output temperature of the at least one tube stack used for start-up.
3. The once-through evaporator of claim 1 , further including a control valve in fluid communication with the inlet manifold and the tube stack to control the fluid flow therebetween in response a signal provided by the controller.
4. The once-through evaporator of claim 1 , wherein the controller is a pressure controller, a mass or volumetric rate flow controller, a phase change controlling device, or a combination thereof.
5. The once-through evaporator of claim 1 , wherein a single tube stack is used in the start-up.
6. The once-through evaporator of claim 1 , wherein the first flow control device is a block valve.
7. The once-through evaporator of claim 1 , wherein the second flow control device is a block valve.
8. The once-through evaporator of claim 1 , wherein a plurality of tube stacks is used for the start-up.
9. The once-through evaporator of claim 1 , wherein a plurality of tube stacks are disposed vertically.
10. The once-through evaporator of claim 1 , further includes a horizontal duct for directing heated gas through the one or more tube stacks.
11. The once-through evaporator of claim 1 , wherein the parameter of the evaporator is the temperature of the working fluid in the tube stack.
12. The once-through evaporator of claim 1 , wherein the one or more tube stacks used for a start-up of the once-through evaporator is one or more intermediate tube stacks.
13. The once-through evaporator of claim 1 , wherein the one or more tube stacks used for a start-up of the once-through evaporator is an outer-most tube stack.
14. A method comprising:
discharging a working fluid through a once-through evaporator; where the once-through evaporator comprises:
an inlet manifold;
one or more inlet headers in fluid communication with the inlet manifold;
one or more tube stacks, where each tube stack comprises one or more substantially horizontal evaporator tubes; the one or more tube stacks being in fluid communication with the one or more inlet headers; where one or more tube stacks are used for a start-up of the once-through evaporator;
one or more separators in fluid communication with one or more tube stacks;
a separator in fluid communication with the one or more outlet headers;
a first flow control device in fluid communication with the separator and at least one of the tube stacks used for start-up;
a second flow control device in fluid communication with a superheater and at least one of the tube stacks used for startup to bypass the separator; and
a controller for controlling the actuation of the first and second flow control devices in response to a parameter of the evaporator;
measuring a temperature of the working fluid in the tube stack; and
controlling and opening of the first flow control device and/or the second flow control device based on the parameter of the evaporator.
15. The method of claim 14 , further comprising opening the first flow control device and the second flow control device at low loads.
16. The method of claim 14 , further comprising closing the first flow control device and opening the second flow control device as the working fluid superheats.
17. The method of claim 14 , further comprising closing the second flow control device and opening the first flow control device as the working fluid superheats.
18. The method of claim 14 , wherein the parameter of the evaporator is the temperature of the working fluid in the tube stack.
19. The method of claim 14 , further comprising opening the second flow control device as the working fluid superheats.
20. The method of claim 14 , further comprising closing the second flow control device as the working fluid superheats.