Temperature control on desuperheater
Temperature control on desuperheater
(OP)
Hi all, first time posting here. Not sure if this is the correct forum for this question, but there's no controls engineering forum. I work in EPC, and am working on a functional description for a desuperheater control loop. The way the system works is as follows:
Superheated steam passes through a letdown station (PCVs) and is dropped to 120 psig. It then passes through a desuperheater, where superheat is removed by condensate. Pressure is measured at the outlet of the DS. The condensate flow is controlled by a cascaded temperature and flow loop, with the temperature measured at the outlet of the DS and the flow measured upstream of the condensate flow valve.
Currently we show the FIC as being a feedforward controller. I don't have much experience with feedforward control, but to me this just looks like a cascaded loop. So my question is, does there appear to be any feedforward control in the system I described?
Thanks in advance!
Superheated steam passes through a letdown station (PCVs) and is dropped to 120 psig. It then passes through a desuperheater, where superheat is removed by condensate. Pressure is measured at the outlet of the DS. The condensate flow is controlled by a cascaded temperature and flow loop, with the temperature measured at the outlet of the DS and the flow measured upstream of the condensate flow valve.
Currently we show the FIC as being a feedforward controller. I don't have much experience with feedforward control, but to me this just looks like a cascaded loop. So my question is, does there appear to be any feedforward control in the system I described?
Thanks in advance!
RE: Temperature control on desuperheater
RE: Temperature control on desuperheater
RE: Temperature control on desuperheater
For future reference, you can find the Control Systems Engineering forum here: [/https://www.eng-tips.com/threadminder.cfm?pid=830i...]
Not sure how pertinent the question is, but IIRC the time constant in desuperheaters can vary depending on type, i.e. contact or spray; which one is used in your application?
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]
RE: Temperature control on desuperheater
If I understand your question, it's contact type. Basically a packed bed that the condensate is being sprayed across. We're still designing the processes, so not quite at the stage of figuring out time constants or tuning loops yet.
RE: Temperature control on desuperheater
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]
RE: Temperature control on desuperheater
RE: Temperature control on desuperheater
RE: Temperature control on desuperheater
You don't need special thermowells, traditional designs work fine. The finned designs are better suited for high precision, gas flow metering. They do offer improved response time and better accuracy at low temperatures. As long as your main run piping is insulated, accuracy is a non-issue for traditional designs. The calcs ar easily performed if you provide your data.
RE: Temperature control on desuperheater