The issue is starting up a Sour Water Stripper (SWS) with a pumparound system. One concern was the pumparound pump suction going dry before sufficient level was maintained.
Summary responses:
On a recent SWS start up, condensate was injected into the pumparound pump suction. A jumpover also permitted recycling bottoms to feed for warmup prior to startup.
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The pumparound water will become the worst quality water in the system (high NH3 and H2S). Condensate, boiler feed water, stripped water or SWS feed could be used to the suction of the pumparound pump to fill the pumparound section up. Water with any hardness (service, fire or hard process water) should not be used.
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We filled our 500-gpm SWS via a 2” service water line to the pumparound pump suction. Once there was a high level in the bottom of the tower, we recirculated bottoms-to-feed (with the tower vented to atmosphere) and gradually ramped up the steam to the reboiler. Once the tower pressure was up to ~ 5 psig we started the pumparound pump, increasing steam as necessary to maintain positive pressure.
Establishing pumparound circulation before the tower is venting steam could be a problem. Usually the chimney tray has weep holes, in which case the pumparound pump may lose suction without supplemental water makeup. A welded chimney tray should be considered as gaskets tend to wash out in spots, requiring supplemental water injection to the pumparound section.
Consider locating the overhead TI in the top of the tower, rather than in the offgas line, where heat from the steam tracing will give a false high indication in the temporary absence of offgas flow during startup.
A TC bypass around the pumparound cooler allows the operator to maximize the pumparound rate and water temperature and minimize H2S concentration and corrosivity.
On a recent SWS start up, a jumper from the feed line to the pumparound return line was used to inventory the pumparound system.
Duke Tunnell
for the ABPG
2 responses so far ↓
Dr prakash // September 8, 2009 at 4:53 am |
Can feed be used instead of pumparound for debottlenecking of SWS with limited cpacity of pumparound cooler? Intend to use live steam to provide additional sensible heat and stripping steam for additional flow from 220 m3 to 300 m3.
Comments if any
Spartacus Refinery Services // September 30, 2009 at 12:16 pm |
Having worked in a gas treating unit for years, we would typically start our SWS with Utility water, and carefully bring up our reboiler temperature, when we got to optimum pumparound rate and tower temperatures, we would start slipping in sour water.