Sizing of nitrogen utility connection to Closed Drain drum

[cecilia bootree]

Dear Process Engineers,

I am looking for some tips to size nitrogen utility line (including restriction orifice for blow-by protection) connected to a closed drain drum. I assume that the Nitrogen flowrate required for sweeping of the drum should be related to the volume of the drum. Any other suggestion for the sizing of the connection ?
Thanks in advance

 

[Iomcube]

I assume that the Nitrogen flowrate required for sweeping of the drum should be related to the volume of the drum.

Technically it's more related that how much 'inert' is required to reduce LEL of vapours in that drum to acceptable limit. If vapour is toxic rather than flammable then acceptable environmental emission limit will dictate amount of sweeping inert e.g Cl2 gas

 

[georgeverghese]

Nozzle size should be a min of 2inch for mechanical integrity, if the drum isnt very large. Actual N2 flowrate would be managed by operators at a nearby throttle valve. The RO should be sized for the max safe handling capacity of the the flare or vent system the CD drum is tied into, but this rate should also not exceed say 20-25m/sec through the nozzle at min normal CD drum pressure.

 

[Iomcube]

The RO should be sized for the max safe handling capacity of the the flare or vent system the CD drum is tied into

I think N2 PRV set at desired pressure will be more reliable

 

[georgeverghese]

@iomcube,
My guess is that this CD drum free floats on the LP flare or vent system, with no valves on the vapor exit.

 

[cecilia bootree]

Thanks for your replies.
I confirm that this CD drum floats on LP flare, it collects effluents from hydrotreatment unit, containing H2S.

 

[georgeverghese]

Any manual valves on the vapor exit should be locked open and opened only with supervision and under work permit order.