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Residual H2S Loading In Lean Amine

amine regeneration unit lean amine h2s loading amine treatment unit reflux rate in aru

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#1 SANDEEPCH

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Posted 02 February 2018 - 01:11 PM

In our FCCU unit there is facility of amine treatment of fuel gas and LPG. We also have an amine regenerator column which strips out H2S from rich amine. Our unit went for long M&I approximately for 2 month. Before shut down we regenerated the whole Amine and stored in a tank with N2 blanketing. During start-up we took back our amine from the tank. Some amine got loss in process upset. So we had to take fresh MDEA (AROUND 10-20% OF TOTAL AMINE). After start-up we are facing residual H2S loading in Lean Amine.

Here are details.

Amine used- MDEA (25% strength)

Amine solution circulation rate 25m3/hr for fuel gas and 12m3/hr for LPG.

Reflux in amine regenerator column- 0.5 m3/hr

Amine regenerator top temp- 110 oC

Amine regenerator bottom temp -129.5 oC

 

Before shutdown we were maintaining amine regenerator top temp 106 oC and reflux rate 0.35 m3/hr and were getting 0.05 wt% H2S in Lean amine. We have increased top temp from 106 oC to 110 oC and reflux rate 0.5 m3/hr. But still we are getting Lean amine H2S around 2wt%. What could be the probable reason? How we can troubleshoot this problem. Please enlighten me from your expertise.

 

Thanks & Regards!



#2 Nikolai T

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Posted 04 February 2018 - 09:17 PM

Hello,

 

The amine strength seems too low. The 40-50 wt% is acceptable value for MDEA. If I were you I woud review old trends (concentrations, temperatures, pressures, flow rates) since first run if possible. What is design value of concentration?



#3 SANDEEPCH

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Posted 10 February 2018 - 10:54 PM

Earlier concentration was also 25-27%. Circulation rate, bottom temperature were same. Top temperature used to be 106 oC (now 110 oC ). Unit was designed for DEA. But solution has been changed for so many years and it was working fine before shutdown. 



#4 Nikolai T

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Posted Yesterday, 07:54 PM

Did you analyze your solvent?

 

Regards,

Nikolai

Attached Files


Edited by Nikolai T, Yesterday, 07:57 PM.


#5 Lavi

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Posted Today, 02:47 AM

You have added fresh amine to your system. And this is causing the lean loading to increase. It is normal.

The system will get back to regular amine lean loading after a certain period of time (when you have stable salts formed).

If you urgently want to decrease the loading try the below

1. Decrease the amine flowrate giving more time for amine to stay inside the column for more stripping
2. Increase column top temperature




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