4 replies to this topic

[Sumun]

Have you seen or implemented any feed surge drum without blanketing, does it work smoothly?
Our client is currently operating without blanketing in naphtha fees surge drum and having no issues but I think it is not good practise.
In the absence of blanketing is it right to assume that operating pressure will be more than or equal to equilibrium vapour pressure in the vessel in all scenarios including startup and shutdown.
Thus can it be considered that op pressure equals equilibrium vapour pressure for NPSHa in feed surge drum?
What about when the level in the vessel goes down, if there is no padding, then the pressure would generally go down and not maintain till the equilibrium is reached again?

[Nikolay_]

Нello,

I think to operate feed drum you should have breath in any case whether will it be nitrogen with gauge pressure or simple breath into atmosphere  (without blanketing). Thus, you will have atmospheric pressure in case breath into atmosphere and gauge pressure if you have nitrogen blanketing (for example).

[Sumun]

Thanks for your reply Nikolai.
Client doesn't want to introduce nitrogen or air in drum due to potential of catalyst poisoning in downstream units. Also non condensables can interfere with their downstream column operation.
Initially it was padded with fuel gas for this reason. But hydrogen in fuel gas is getting dissolved with the feed and leading to flaring in downstream splitter that has a total condenser.

[Nikolay_]

Do you have horizontal cylindrical vessel or vertical tank? What is the temperature in the drum? Reid pressure?

[Nikolay_]

I have seen the flow sheet of Reformer unit where feed stream goes from feed tank with pontoon (float blanket) to the preheat train exchangers directly. The feed tank intended to keep reserve of feed and for separating of water.