NGL Liquid Dehydration Unit (LDU) Bed Outlet Temperature Droped

[richman1209]

Dear All.

I have some doubt regarding our NGL Liquid Dehydration Unit (LDU) during regeneration after heating cycle 30 minutes started, found LDU bed outlet temperature suddenly dropped out to – 8 till -10 deg C for 15-20 minutes only. This happen always repeated.

For information, parameter condition are :

We have 2 LDU unit : one drying and one regeneration.
- Drying Condition
normal operating pressure: 18 barg
NGL flow rate : 45 m3/hr
drying time : 12 hours
process flow : stabilizer overhead accumulator drum --> stabilizer ovr.head pump --> Liquid Dehydration Unit --> LDU Cooler --> Dry NGL Product.


- During Regeneration
pressure : 5 barg using LP Fuel Gas
regeneration sequence:
1. draining : 1 hours
2. depressurize : 45 minutes
3. heating cycle : 6 hours 48 minutes
4. cooling cycle : 2 hours 42 minutes
5. pressurizing : 30 minutes
6. filling time : 1 hours 30 minutes

My questions are :
1. Why after heating cycle 30 minutes started, LDU bed outlet temperature dropped out to minus deg ? Could detail explanation please ..

2.How to prevent temperature minus ? it means is that possible to adjust parameter condition on regeneration sequence or another method ?

Thank you for all who's giving idea to solve this problem.
I hope this forum we can share knowledge and experience

Regards,

Richman