Quench Water Tank – Open Top or Roofed?

[danielParticipant]

Can anyone share the pros and cons of having open top tank versus roofed tank? What is design consideration taken into place when designing open tank? Do you send your blowdown settling drum water to open top tank? Appreciate you input.

[Anonymous]

Blowdown settling drum water is typically sour water.  We send ours to our sour water tanks for treatment in our various sour water strippers.  I would think that it would be a very bad idea to pump this water directly to an open tank.  You could add a slipstream of the sour water to your quench water during the quench, similar to sludge injection, but you would still need somewhere to store it until needed.
As far as open top versus roofed, it’s dependent upon your situation and your uses.  We have an open top tank.  We maintain our level in the tank with stripped sour water, so no H2S, with a utility water backup if we lose our stripped sour water makeup.  One of the benefits of an open tank is that you can quickly get a visual idea on the status of your tank.  Plus, when it comes time to clean out the fines, I imagine an open top may be easier in that you could wash it down with a firehose from up top.  The open top helps the heat dissipate a little faster than a roofed tank would.
Not everything by any means, but it may give you a starting point.

[Claus GrafParticipant]

In a DCU I worked some years ago, we pumped the blowdown settling drum water to the cutting/quench water tank that had a roof. We could also pump it to the fractionator (if needed).
 
Hope this helps.
 
CG

[antonio saura CebrianParticipant]

I have worked in various coker units, and almost all of them have had open-top tanks, it has advantages over closed-top tank (roofed tank), as well as allowing faster cooling, it also allows a quick overview of their level from the floor or from the cutting platform, the distinction of putting the roof up or not general are associated with the potential emissions of H2S, because of their sour water condition

the designs of these units (FW) indicates that the water collected in the Blowdown drum can send the tank between 3 to 4 hours after starting the cooling of the drum with water, since the content of H2S and NH3 are low (theoretically), but some of the problems that we had was the content of hydrocarbon accumulated in the tank that subsequently created problems in the pit of coke, we did several tests with the time and deemulsifier but finally we decided not to send the water to the cutting water

[Nor Syamrin WagirinParticipant]

thanks all for the input.. does anyone uses the blowdown settling drum water for quenching? if yes, what is the limit in temperature at coke drum when intorducing this water? we’d recently switch to open top tank (by incident), what we see is that the the water tank accumulates some oils (over the time), which we perform daily skimming. We are thinking of using demulsifier in the the settling drum to help separate water and oil. Any good chemicals?

[Author]

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