High Pressure Hydrotreater - Block Valve on Chg Heater and Stripper Heater discharge?

[NWLaengr]

I'm designing a 2500# lube oil hydrotreater and had my first P&ID review yesterday. The operations guys would like a block/gate valve on the heater discharge to be able to steam out the heater in shut downs / turn arounds. This block valve would be used to block the heater outlet off from the reactor section (and assure no liquid is present when a spool piece is pulled and assure no steam makes it to the catalyst bed) and allow the heater to be steamed out from the heater discharge back to the heater inlet. At the inlet a bleeder valve would be connected to a line going to the plant steam blow down drum. The plant personnel would like the same set up on the stripper feed heater. On the charge heater the outlet temperature will be 680 to 700 def F @ 2400 psig. On the stripper feed heater the temperature will be 560 deg F (or lower) at 30 psig.

I have concerns on putting a block valve in such a high temperature/high pressure area downstream of the heater. Can anyone speak to set ups in refineries they've been in?

Also, if your facility doesn't have valves on heater discharges, what steps are taken to steam out a heater and not have steam make its way over your catalyst bed?

Thanks for your help.

-MM

 

[NiravK]

Yes, you are right in saying that high pressure hydrotreaters do not have any block valves in recycle gas circuit. There are various reasons for that.
I would recommend a "swing elbow" at heat inlet and outlet lines. This will allow you to disconnect heater from process inlet/outlet lines and connect it to either decoking system or for steam out purpose. In this way, no water or steam will go to catalyst. This is a standard way in many refinery hydro processing units.
Warm regards,

Nirav Kholiya
nirav-kholiya@enc.ltindia.com

http://www.lntenc.com

 

[GaTechTheron]

If I remember correctly, I believe we used a spec blind for this purpose on the last hydrotreater I built.