why using this control scheme??
why using this control scheme??
(OP)
hi all
tha attached pic is our stripper at Naphtha hydrotreating unit (NHT),after u see the pic plz answer me for?
1- why try no. 5th from top is selected as a temp. control while the common practice is the top tray temp will be controlled by the reflux flow.
2- why the TIC-1036 is cascaded to FIC1014(this product(LPG) we send it to another unit) and not with reflux flow
3- why the level of the reflux drum is cascaded to the reflux flow (LIc1008 with FIC1013)?
4- also the temp. control of the reboiler furnace (F-71102) has a selector TS1001 between 2 controls, the TIC1020 is the calssic but i want to know more about PDIC1001
thanks for being helpfull
tha attached pic is our stripper at Naphtha hydrotreating unit (NHT),after u see the pic plz answer me for?
1- why try no. 5th from top is selected as a temp. control while the common practice is the top tray temp will be controlled by the reflux flow.
2- why the TIC-1036 is cascaded to FIC1014(this product(LPG) we send it to another unit) and not with reflux flow
3- why the level of the reflux drum is cascaded to the reflux flow (LIc1008 with FIC1013)?
4- also the temp. control of the reboiler furnace (F-71102) has a selector TS1001 between 2 controls, the TIC1020 is the calssic but i want to know more about PDIC1001
thanks for being helpfull





RE: why using this control scheme??
I agree if you are suggesting that the level should set the product flow and temperature set the reflux. I don't have time for a study and I have not played with distillation control for a while. Others can address why temperature toward the top of the tower was selected for the product flow instead of the reflux flow. Internal reflux control used to be popular using differential temperature such as a high tray and the overhead. I cannot comment on why tray 5 from the top was selected. The graphic is not clear regarding the PDIC measurement points. One is the reflux line but the graphic does not reflect the other pressure in a manner that is clear to me. Perhaps the furnace temperature and PD selection is an automatic override.
RE: why using this control scheme??
the PDIC measurement is a typical orifice plate that installed at the reboiler furnace outlet line but itsn't reading a flow, it reads PD across that line.
RE: why using this control scheme??
If this is a demo control scheme, it doesn't necessarily have to be fully accurate to be a demonstration.
If the scheme is an actual plant under control then it ought to be accurate and any anomalies fully understood.
JMW
www.ViscoAnalyser.com
RE: why using this control scheme??
the scheme is an actual plant under control and operation for 3 years. this snapshot was taken during first configuration and if you like, I will upload the actual DCS snapshot which is the same and with actual operating values.
thanks for passing over.
RE: why using this control scheme??
Assume that the control is as shown. If the level is too high then perhaps it just sends liquid back to the column depending upon the output action. The cooling could knock the vapor down so perhaps that could work. And if the temperature is too high does it increase or decrease the overhead product draw?
RE: why using this control scheme??
Yes the scheme is an actual plant under control and operation for 3 years. this snapshot was taken during first configuration and if you like, I will upload the actual DCS snapshot which is the same and with actual operating values.
we needs to answer your questions to well understand the system. thanks
RE: why using this control scheme??
RE: why using this control scheme??
RE: why using this control scheme??
PDIC1001 is watch differential pressure across the tower. If it goes to high, then the tower is flooding and you need to cut heat input or reflux, which will cut heat input.
RE: why using this control scheme??
about using DP to detect flooding plz see the attached file