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!