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In VGO HDS,fractionator Naphtha produced contains presence of H2S. So Naphtha is routing to slop. We have increased steam to stripper to reduce the H2S content in Naptha. But no effect obseverved.What can be done to avoid H2S presence of Naptha for routing to storage?
 
Answers
30/06/2015 A: keith bowers, B and B Consulting, kebowers47@gmail.com
Take a look at the H2S and C3 content of the stripper feed, and then the same on stripper bottoms and overhead products. Since H2S boils in C3 range, one muct strip out the C3 in the feed to get the H2S out.
29/06/2015 A: Ganesh Maturu, Self, maturu.ganesh@gmail.com
If the stripping operation is efficient, there will not be any H2S carryover to Naphtha in Fractionator overhead. Following are some optimiziation steps to increase the stripper performance.
1. Make sure that stripping steam saturated vapor temperature is below the column bottoms temperature. This will make sure that stripping steam never condenses on the trays and stripping affect is efficient in the bottom sections of the stripper. If stripping is efficient, almost all the C3s and H2S range material removes from stripper bottoms.
2. Try to reduce the stripper operating pressure based on your battery limit offgas pressure.
3. Increase the stripper overhead temperature little bit by adjusting the air cooler. Dont sub cool stripper overhead so much. Try to maintain around 50-55 deg C at air cooler outlet.
4. Increase stripping steam upto dewpoint margin is maintained. If water dewpoint margin can not be maintained at the stripper top, increase the feed temperature little bit to get enough reflux and hence dew point margin.
5. Make sure that Fuel gas push pull system maintained at fractionator receiver to control the receiver pressure should not contain any H2S.
21/06/2015 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
Then, there is the possibility that throughput is higher than the capacity of the stripper column. Calculations will determine if that is the case.
18/06/2015 A: sam lordo, Becht Engineering, salordo@comcast.net
One avenue that removes the h2s but not the sulfur itself is by applying h2s scavengers , most of this products contain no metals. it is important to determine what the byproducts are as some of the h2s scavenger can form undesirable amounts of monoethanolamine (MEA) , especially if it is being rerouted back to the crude unit
17/06/2015 A: Sarath Konda, DuPont India, sharathsatya@gmail.com
Typically stripper bottoms contains very less amount of H2S (probably in PPB levels), but in the fractionator it is gets concentrated in Naphtha product indicated a higher level of H2S. You can try following options to reduce the lower H2S concentration.
1. Lower Stripper pressure to pull more lighter material & H2S from stripper
2. If possible, increase the feed temperature (10-15 deg C, to increase the stripper bottom temp) with increase in stripping steam to strip more lighters/H2S from the stripper.
Above 2 options should help to reduce the slippage of H2S. Kindly note soluble H2S will still escape to fractionator (but should not cause much problem).
If the above suggestions doesn't help, then adding a caustic wash system to your naphtha stream will be the next option