The linked thread does not mention the importance of a properly sized holding tank or "feed stabilization tank" (ideally 3 days) to ensure a constant composition in the flow to the SWS. This will help you to maintain a steady overhead temperature of 100 C or so. The feed to the SRU should be kept >85 C.
Ben Spooner, P. Eng
Process Engineer
Amine Experts Inc
Calgary, Alberta
Of course bspooner is right. The tank is an usual (obvious?) installation for homogeinizing compositional changes and getting a regular stripper operation. Otherwise, these changes may result in overstripping wasting steam, or not consistently meeting product spec.
About two feet of hydrocarbons are allowed to float on top of the sour water for odor reduction. Cone roof tanks may require nitrogen blanketing for safety and odor control.
Escaping vent gases may need to be treated to answer to local environmental regulations.
Clearly, hydrocarbons in the feed stabilization tank should be removed before emptying the tank to prevent the SWS to become an oil stripper.
The feed, pumped on flow control, is generally pre-heated by exchange with outflowing stripped water. A LP steam reboiler is usually used rather than adding water by injecting live steam, thus saving condensate while operating the stripper at lower pressures.
I believe it was mentioned in the previous link that the top of the stripper should be kept above 180 deg F, to avoid sublimation of ammonia salts, that may plug everything, including the tower's overhead piping.
A particular problem arises when treating FCC waters containing cyanides which may require titanium overhead condensers to prevent corrosion under deposits.
One of the procedures to avoid using a condenser and reduce corrosion is using a pump-around cooling system. Pump-arounds, being liquid-filled systems wouldn't permit deposition of solid salts.
Sour water conttain some sulphuric components such as ( hydrogen sulphide) is accumulated at the main accumulator of refinery fractionating column and then is fed to sour water stripping unit which use steam to strip the water and remove the sour gases at the top of stripper tower to pass through air fan coolers then to be burnt in the main heater as well as the stripped water which drawn from the bottom of the stripper is used again in the process by inject it to the crude system to dissolve the salt . the main problem is the very high of corrosion rate at the top of this sour water stripping unit ( the tubes of the fan cooler and the top trays of the stripping tower )
The question is if we install corrosion inhibitor dosing system at the top of the sour water stripper will it be the ultimate solution of this problem ?
