7 replies to this topic

[bluewater]

An industry want to revamp its naphtha splitter unit.

The NSU column should be capable of processing 200 Mt/hr of NSU feed
corresponding to 17.0 wt% of Naphtha yield in BH crude case.this is to be done against the
design value of 150 Mt/hr because of higher availability of feed.

C7+ content in the NSU top cut to be maintained within 10% w/wt as per the
required feed specification of the ISOM unit.

Benzene and Benzene precursors in CCRU feed to be maintained within 4 wt% to
meet the Benzene specification of MS.


Basis for the study
a) The design data of column, condenser, and reboiler is given in the Annexure.
The column feed temperature after the feed bottom exchanger has been
considered at 95 deg C as per discussions with refinery. The reboiler to the
column is a furnace.
c) The reboiler duty is considered at 16.5 Gcal/hr for the study against design of
17.2 Gcal / hr in view of reported limitation in the reboiler furnace.
d) The client does not want to carry out any changes in the furnace system. The
overhead condenser is a set of Air cooler elements.
e) The design duty is 14.7 G Cal /hr.
f) The operating pressure of the column top is considered at the design condition
of 2.3 kg/cm2(absolute).


Annexure- I
NSU Feed:
Pretopper Naphtha : C5 - 140 deg C cut TBP
Topper Naphtha : 80 - 150 deg C cut TBP
NSU column
1.0 Diameter ID 4500 MM
2.0 No of Trays = 40 (Valve)
3.0 Feed entry at 19th tray
4.0 Delta P each tray 0.01 Kg/cm2
Reboiler to column
The reboiler to the column is a furnace. The reboiler duty is considered at 16.5 Gcal/hr
for the study against design of 17.2 Gcal/hr in view of reported limitation in the reboiler
furnace.
The client does not want to carry out any changes in the furnace system.
Overhead condenser
The overhead condenser is a set of Air cooler elements. The design duty is
14.7 G Cal /hr.

attached flow sheet  NSU-PFD.pdf   61.52KB   70 downloads]

[Padmakar Katre]

Dear,
Please let us know your actual problem i.e. where is the bottleneck among the column dia,the ovhd circuit or reboiler circuit.Waiting for your query.

[bluewater]

Dear,
Please let us know your actual problem i.e. where is the bottleneck among the column dia,the ovhd circuit or reboiler circuit.Waiting for your query.

how can we increase the feed input to the column to 200 Mt/hr against the design value?

[Zauberberg]

Where is the bottleneck? Tower itself, ovhd condenser, reboiler?

[bluewater]

Where is the bottleneck? Tower itself, ovhd condenser, reboiler?

couldn't understand your question
can u please explain a bit?

[Zauberberg]

My thought was that you have already taken some effort to benchmark the unit and confirm if there are any bottlenecks. But, you are just giving Design vs. Revamp conditions/requirements and without any analysis done by you? That's not the way to go.

My guess is that the reboiler would probably bottleneck the unit since there is little extra duty available for feed increase. In any case, it looks like the feed increase will first hit the reboiler limit but perhaps I'm wrong. One hint: try to apply the same capacity factor (+33,3%) for the entire equipment and compare it against max. design values. You'll see where you are, approximately.

[Padmakar Katre]

Dear
Just start with the simulation with taking into considerations the existing hardwares like column, ovhd condensers and reboiler.First make the simulation model for the existing conditions like Feed flow,temp,press and quality along with the column operating conditions. And just find the simulation ouput parameters to achieve the required specifications this will give you an idea where are the margins and what could be the probable bottleneck.
1. In case of your tower what is the V-L traffic in case of original thruput and what is margin in diameter (vapor loads) and what would be the revised liquid loads would it be accomodated with exsiting liquid downcomers.
2.In case of ovhd circuit what is the revised pressure drop/velocity which will help you to find the ovhd line adequacy. Further to it you need to do rating for the ovhd condenser with softwares like HTRI.
3. Similar to point 2 you need to do it for reboiler circuit.
Now after doing this assignemnt let us know your findings or any doubts we will help you to clarify those.

[ramu]

hey bluewater... are u mentally challenged guy that you have posted a chemical problem from a techno fest of a renowned institute here.... if you don't have the guts to solve a quiz problem by yourself then better not participate.... now better find another place...