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Coker Naphtha Diolefin Reactor

Coker Naphtha Diolefin Reactor

Coker Naphtha Diolefin Reactor

We have and HDS unit that processes 100% coker naphtha (I don't recommend this operation to ANYONE).  It has 3 reactors.  The 1st Reactor was ment to be for diolefin saturation and it is placed before the furnace.  Sometime ago, it was decided to convert this unit to heavy coker naphtha and a depentanizer was installed before the unit.  Since then (I presume) the 1st reactor has become useless.  There is no dT, it is too cold to pick silica, ect.  I recommended that this reactor be taken out of service.  However, at least twice a year the depentanizer is down for about 7 days.  What would be the consequence of removing this reactor.  Could it be possible to plug the unit heater rapidly?

RE: Coker Naphtha Diolefin Reactor

The cold reactor will act as a filter removing particles and bypassing it will send the particles to the 2nd reactor causing delta P there. Why not increase the temperature by more heat exchange (i.e. revamp)? Then the reactor could be of use both for olefin saturation and Si pick-up.
Check if there isnt any adsorbent (for Si0 that can operate at the temperature you have at present. There are newer (high surface, low Ni) cats/adsorbents that perhaps can be used for this purpose.

RE: Coker Naphtha Diolefin Reactor

What's the pressure drop in this reactor?
You should be having somebody very rich to have such a large filter upstream of other reactors. I wonder what is the intention of designer of your plant.
It's ok to process 100% coker naphtha, catalyst is subjected to max severity.

Coker naphtha does have high silica, that can be caught in the gaurd beds, heater won't plug for silica.

What's the gurantee that it is catching all the Si what is normally assumed? do you check inlet & outlet Si-content? how do ensure that bed is working?

what's licensor's opinion on this?

If you have means to ensure no Si leakge from this reactor, then check what the trend says rather that taking it off-line. Costly indication would be higher Dp on subsequent reactor.


RE: Coker Naphtha Diolefin Reactor

The 1st Reactor does not trap silica or filter out solids. We have analyzed the Rx1 catalyst on several occassions for silica.  There is none. The dP is only 4 psi, so it does not filter anything (actually we have full flow filters before the unit).  All catalyst vendors agree that this reactor is too cold (<300F) to trap silica.  The other 2 reactors trap everything. Trust me, I have enough turnarounds in the year to know.  All shutdowns are related to silica in the product and never pressure drop.  

Revamping the unit to give this reactor more heat is extremely expensive and we have no incentive to do so. However, we have thought about converting this reactor into a swing reactor to extend cycle life.

I am still concern about diolefins which was the intended purpose of the reactor.  Diolefins are highly reactive and they will gum heater/exchangers if they are not converted.  My original question was to know if there are some coker naphtha HDS without a diolefin reactor.


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