What is the purpose of a desuperheater?
What is the purpose of a desuperheater?
(OP)
Hello,
I recently had an opportunity to look at a project at a natural gas-fired generation plant's desuperheater. Neat bit of engineering, but the question I had that nobody seemed to have an answer for is; why? What is the benefit of taking 1800F steam at 2200psi (or so) and injecting cool water? I get that there's a phase change involved, but why not take steam at the desired pressure/temp/quality from the turbine where those conditions exist? Is there some aspect I'm missing?
Thanks in advance!
I recently had an opportunity to look at a project at a natural gas-fired generation plant's desuperheater. Neat bit of engineering, but the question I had that nobody seemed to have an answer for is; why? What is the benefit of taking 1800F steam at 2200psi (or so) and injecting cool water? I get that there's a phase change involved, but why not take steam at the desired pressure/temp/quality from the turbine where those conditions exist? Is there some aspect I'm missing?
Thanks in advance!





RE: What is the purpose of a desuperheater?
1800F @ 2200 psi is very hot and high pressure so needs really special materials / turbines etc which cost a lot.
I also don't really know what you do with a fluid that hot.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: What is the purpose of a desuperheater?
Maybe a power plant engineer could chime in.
Here's a webpage with the plant I was looking at:
http://www.power-eng.com/articles/print/volume-109...
RE: What is the purpose of a desuperheater?
RE: What is the purpose of a desuperheater?
Have a fantastic day!
RE: What is the purpose of a desuperheater?
If the plant has a turbine bypass system, pressure reducing valves and desuperheaters may be used to limit pressure and temperature at the discharge end of the bypass (typically, the cold reheat system in a reheat application and a condenser in reheat and non-reheat applications). These pressure and temperature reductions are required so design conditions at the discharge are consistent with the design parameters at the destination.
Best of luck!
RE: What is the purpose of a desuperheater?
Nothing I've read says that Coyote Springs is anything other than a decent CCGT, whereby the GT supplies about 60-70% of the electrical power direct from the GT, thus the inlet temps into the power turbine section can be 1800F or higher, but leave at around 1000F before they enter the HRSG. Steam temp used in the steam turbine is lower than that as stgrme states.
https://energy.gov/sites/prod/files/nepapub/nepa_d...
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: What is the purpose of a desuperheater?
LittleInch - Thank you for the paper and clarification. I'm trying to get a deeper understanding of their systems so I can be more effective contracting work to them.
RE: What is the purpose of a desuperheater?
Thanks,
Ehzin
RE: What is the purpose of a desuperheater?
RE: What is the purpose of a desuperheater?
My experience has been that if the plant is designed correctly, it is not required to have desuperheating for normal operations. For combined cycles, you may want attemperation to help the unit get in emissions compliance sooner. Rather than having to hold lower load on the CTs while the steam turbine warms, you can use attemperators to meet the required warm up rates on while running the gas turbines at full load. Usually this is only considered in the design if it is a unit that has a lot of annual starts.
RE: What is the purpose of a desuperheater?
Tolerance is the virtue of the man without convictions -GK Chesterton
RE: What is the purpose of a desuperheater?
We didn't at the nuke plant I worked at or any of the combined cycles I worked on design (we actually didn't have any steam turbine driven equipment other than the power turbine at the combined cycles) or at the current district energy plant I work at.
Extraction steam from the ST was used for heating processes (feedwater heaters, etc.). The feedpumps at the nuke plant had GE steam turbines as drivers, but they just took LP steam and had an auxiliary condenser below them that fed condensate back to the loop. It all comes down to design stage and matching equipment to available process conditions.
At the district energy plant I am at now, we have steam turbine driven feed pumps, chillers, and chilled water pumps. All of them are designed to take steam at the normal operating temps/pressures of the system. We do have attemperators in the main steam header in case we need to condition steam going out to the adjacent medical center heating process, but I think it is rarely used (I'll check some data tomorrow). It just depends on how our boilers and HRSG are operating.