6 replies to this topic

[Sriram K. Yadav]

Hello friends,

We are buying PYGAS for gasoline blending. Some PYGAS are high in gum. Can anyone suggest how to remove the gum in PYGAS before blending.

[Zauberberg]

Normally you want to reduce the content of gum precursors in the Pyro Gasoline, not the gum itself. That would mean that the product is already contaminated with polymerized material.

Precursors for gum formation are di-olefins. These are commonly removed in the 1st stage of Hydrotreating (i.e. normally located in the Petrochemical Complex). Sulfur species and olefins are removed in the 2nd stage Hydrotreater which is usually within the refinery.

[Himanshu Sharma]

I doubt whether you can blend it straight forward to ur MS Pool because of Euro-4(whatever applicable) Regulations in place,not only stability i.e but Octane number will also be an issue meeting the required spec.

You may route this to MS block upgrading facilities,Mix it with ur other streams feeding NHT and subsequently to Isomerisation and CCR unit.Surely you need to tweak out certain operating parameters here and there.

@Zauberberg
Sir,i have commonly seen two NHT reactors in series in the refinery complex itself because of FCC Naphtha being fed to it. as you said ,the first one is for Di-olefin saturation.

Can you elaborate the Petrochemical Funda,if its ethylene plant you are referring to???

[Zauberberg]

Sharma,

You are absolutely correct. In my post I was referring to the Pygas from Ethylene plant within the nearby Petrochemical Complex, in refinery where I used to work. There was no treatment of FCC gasoline in our refinery at that time, although it was absolutely desirable to have it. In the meantime, I think they have opted for FCC feed pretreatment unit (mild MHC) so that should address the FCC gasoline quality issue as well.

[kimsun74]

Normally the Pygas having unpleasant odour so the percentage blend in gasoline pool are limited, so probably it can be diluted by other low gum blend component and meet specification. In addition high aromatics content in gasoline fuel may aids in keeping gum in dissolved form too. Whatever gum formed in fuel is unreversible, in order to store for longer period you can inject antioxidant to slow down the gum formation process.

[Qalander (Chem)]

Normally the Pygas having unpleasant odour so the percentage blend in gasoline pool are limited, so probably it can be diluted by other low gum blend component and meet specification. In addition high aromatics content in gasoline fuel may aids in keeping gum in dissolved form too. Whatever gum formed in fuel is unreversible, in order to store for longer period you can inject antioxidant to slow down the gum formation process.

Dear Kimsun74 Hello/Good Afternoon, Here I would differ from you

on the gasoline having aromatics would be helpful

• having gum in solution form(partially this might be true)
• but the gum and having it there is highly undesirable for most automotives combustion systems involving any Injection, Ignition mode(s).
• Having said that, the aromatics at times do provide good nucleation resource for even more complex polymerization& even co-polymerization in presence of some impurities, metallic additive(s) that might support such reaction's catalyzing; thereby creating even worse a situation with longer storage periods etc.

Hopefully this clarifies the matter from this typical perspective, somewhat not covered. My vote will not be in favor of blending unless and untill

• The quantity gets highly diluted
• No aromatics contents present to cross polymerize
• No metallic derivative(s) present as addittives to possibly help catalysis in one way or another
• Last but not the least important if posible anti-oxidants addition as suggested above could prove helpful, but at what cost?
• Cost benefit analysis viz a viz for pyrogas components use or no use has to be carefully worked out.

Hope I have shown the way forward in some way,please do feel free to discuss further if felt necessary.

Edited by Qalander (Chem), 12 April 2010 - 11:45 PM.

[Himanshu Sharma]

Adding my two cents

Pygas can either be routed to MS pool after hydrotreatment (mainly because of High aromatic and olefin content in Pygas)
or can be a feedstock for BTX recovery Plant.

Economic evaluation thats demand/supply and Price differetial between gasoline and Petrochem ,set the rules for decision.