3 replies to this topic

[SyedAhmed]

Dear All

 

I need your expertise on the above topic.

 

Actually I have a task to replace the Modulating LCV with ON/OFF LCV combination with RO in the rich amine line at the amine contactor bottom. I am confuse because this may cause problem during operating. The rich amine from the contactor will carry heavy HC and suspended particles which may plug in the RO bore. As we know that Carbon filter is used to remove the particles from the Rich amine. So its mean rich amine contain some unwanted components. But due to the Pressure difference, this plugging may not occur. Because Flash tank and Amine contactor pressure difference is very high so the some particles will flow without choke the RO bore.

 

Please advise if I can suggest to install in the replacement of Modulating LCV with Restricted Orifice (RO).

Edited by 12345656, 24 October 2018 - 08:11 AM.

[Bobby Strain]

I have never seen such a control as you propose for an amine contactor bottoms flow.

 

Bobby

[shan]

A Modulating LCV is able to able to adjust its opening to maintain the amine tower liquid at the desired level.  On the other option, an ON/OFF LCV is not actuated (closed) until the tower liquid level reached the valve set point and a RO with a fixed opening allows a specified constant flow rate without variation with the tower liquid level.  To my understanding, usually the amine flow is controlled with the sour gas rate.  Is it acceptable to you if the amine flow is not matched with the specified RO flow and  the imbalanced flow rates may close the LCV because of high liquid level or low liquid level to cut the rich amine flow to the downstream amine regenerator?         

[Art Montemayor]

You state “Actually I have a task to replace the Modulating LCV with ON/OFF LCV combination with RO”.  Then you follow this with “I am confuse because this may cause problem during operating”.  I - and I would suspect the rest of our members - am also very confused.  If you have doubts (and rightfully so) on what your task is, then why are you doing it?  I doubt that there is any economic reason for replacing the standard liquid level controls normally specified for the amine contactor tower.  I suspect you intend to use a solenoid type of on-off valve to maintain a positive level in the contactor sump.  Whatever the actuating signal, the mechanisms of an on-off valve in a continuous process are going to suffer with wear and tear due to the continuous repetitions of the same actions.  This is not a type of level control I would approve of for a steady state process.

 

Like Bobby Strain, I have never seen, heard of, nor read about such a level control for an amine contactor tower.  The amine flow rate is normally controlled by the steady, continuous flow from the lean amine positive displacement pump and the level in the contactor has to be kept at a constant level to allow for a positive liquid seal there.  The unit operations taking place downstream of the contactor on the amine side are the flash drum (and its own liquid level controls), the amine heat exchangers, amine filters, and the final entrance into the amine stripping column.  All of these operations depend on a steady state flow of amine.  Why do you propose to interrupt that action?  Unless you can come up with a detailed, accurate, and positive reason for doing so, I would not undertake what you propose.  It doesn’t make any sense to me.