16 replies to this topic

[Swetha Mohan]

Hi Guys,

 

The question may be too technical. Help me or please give your view on the following query. The query is regarding Isomerization Unit. We have ISOM unit running @ full throughtput ie @ 100% capacity utilization. The hot feed to this isom unit is light naphtha from NHT Unit. There is also some stock of light naphtha available in our storage tank (inventory). We want to feed Light Naphtha from tank to some extent but we could not feed this inventory material as it carries moisture content in it. Max allowed moisture content in feed is 0.1 wtppm. We have moisture absorber at feed inlet but it is not too sufficient to handle feed from tank too. Please share your views what other Refineries do with the excess Light Naphtha they have. How do you manage to feed Light Naphtha from tank to Isom Unit. or do other refiners sell these excess Light Naphtha directly without any blending?

 

Your Comment & reply will be really helpful.

 

 

Regards,

Swetha.

[gegio1960]

swetha,

could you clarify what do you exactly would like to ask?

If your ISOM is already at 100% utilization, you've to debottleneck it to feed more LTN.

If your Dehydration section is not sufficient to process additional LTN, you've to debottleneck it

[Swetha Mohan]

Its not question of debottleneck...my question is, do any other refinery, process light naphtha from storage tank (inventory)..becos stored light naphtha may contain moisture content and other impurities. So how do they process light naphtha from storage tank??? Hope you understand my question.

[gegio1960]

Water is a poison for ISOM catalysts, so it has to be removed from ISOM feed.

LTN should be completely processed in ISOM to obtain the max profit (except for the small quantities that can be directly blended in gasoline pool). Isomerate is a very useful stream to improve density / benzene / aromatics in gasoline pools.

LTN excess can be sold outside as an intermediate (ISOM feed ;-) ) but, first thing, you need a client (usually another refinery) and, second, the transportation is not so easy due to the high volatilty. Of course, LTN price will decrease with the increase of water content....

If you're willing to share more details ;-) about your "problem" I'll be more than happy to help.

cheers

[Swetha Mohan]

Hi Gegio, Thank you for your patience and reply. Again my question is "Even if other refinery buy LNT feedstock to isom from us, they too have to store it in tank and have to feed it to isom. I believe none of the refinery take feed from storage to isom. Have you come across with any refinery in the world doing this?

[gegio1960]

yes

[Swetha Mohan]

Hi Gegio, It’s surprising to hear the refinery is taking ISOM feed from storage tank even though it has moisture content in feed. If it is so, don’t they have the degradation of catalyst? How do they manage? If possible, can you share the name of the refineries or which part of Asian Refinery is doing such kind of process?

Regards,

Swetha

[gegio1960]

We've already mentioned the Dehydration section on the ISOM feed.....isn't it?

Another one should be also foreseen on the Hydrogen make-up

[Swetha Mohan]

If possible, can you share the name of the refineries or which part of Asian Refinery is doing such kind of process?

[gegio1960]

Swetha,

I mainly work in EMEA region. So, I think you've more easily access than me to Asian refineries :-)

Could you kindly provide more (basic) info on your case? For instance:

- type of ISO catalyst

- ISO technology/licensor (eg Penex, Molex, TIP, +DeIC5? +DeIC6?)

- presence and type of ISO feed and H2 make-up dehydration sections

- ISO capacity

- possible ISO feeds (eg LTN form SR, HCK, FCC) with relevant quantities and available storage

- presence and use of LP refinery models

- refinery processing scheme

- ISO operations in different modes/capacities (campaign)

If you want, I'm also available to further follow this subject privately (you can use the messenger tool available on the 2nd line of the site header).

Cheers,

gegio

[Himanshu Sharma]

Dear Sir/s

 

I assume that isomerate is blended with reformate along with other Naphtha range material to form Gasoline.If this is the case, capacity of ISOM is governed by amount of straight run/cracked light naphtha that can be straight ways blended to fixed quantity of gasoline pool.(you may need a LP model for this)

 

Increasing ISOM capacity may help you increasing Gasoline make in the refinery but please check with other streams available for blending as vapor pressure of isomerate is generally a concern.

 

ISOM as per norms should be fed directly from NHT as per stringent water and sulfur limits on ISOM catalyst.Licencors generally don't recommend cold feed processing from storage tanks,even during start-ups of ISOM whole naphtha is recycled back to NHT. However ,its your plant anyways and you may afford some calculated risks after tank material analysis.

 

Normally excess Light naphtha is managed by 

 

1. Blending in Gasoline Pool.
2. As a Feed to Hydrogen Generation Unit.
3. As a Feed to GT in CPP.
4. Blending with heavy naphtha to form full range paraffinic Naphtha for fertiizers/petrochemicals.
5. Cracked in FCC risers to form petrochemicals
6. Cracked in a dedicated Naphtha cracker feeding to petrochemical plants

Regards

Himanshu

 

[Swetha Mohan]

Hi Gegio and Himanshu,

 

Thank you so much for your replies. Your views were very much useful to me.

[NATU]

Swetha,

 

In our unit we are using light naphtha from storage during start up only. however, in our unit we have 3-phase separator at the inlet. Any water content in the feed is separated in 3-phase separator.

 

regards,

rajiv

[Mainak Sarkar]

Hi, phase separator is required, but it only separates the physical moisture. For removing equilibrium moisture, molecular sieve type absorbent is mandatory.  I think; for ISOM unit moisture in feed should be less than 1 ppmw. The use of light naphtha from storage tank is not recommended also due to presence gum precursor.

[rahulk_19]

Does anybody have experience of ISOM unit without dryer (facility for moisture removal from Naphtha feed ) .In our new ISOM plant there is a dryer on recycle gas but there is no dryer in naphtha circuit..

 

 

Regards

rahul

[P.K.Rao]

Ms Swetha,

Much is already said. About the Asian (and other) refineries, please follow the link,

https://en.wikipedia...ineries#Nigeria

Edited by P.K.Rao, 05 August 2015 - 03:10 AM.

[tuncer]

If you have small  Unused Diesel/Kero desulphurasition Unit, You can feed your sour light Naphtha to this Unit Hydrotreater and then directly feed to Isom unit. Your bottleneck is Isom NHT unit. ıf you increase Unifiner capacity you can play on sidedraw stream an increase Isom Unit capacity.