Mine diesel production

[sav455]

Hi,
I am working on developing a scheme for production of 15 ppm diesel from naphtha and kerosene stream. Basically I am trying to get to some scheme which gives me minimum heater duty, minimum no. of stages,min. col diameter, optimum tray location for both the feeds and optimum diesel draw location from the column.
I have found that reboiler configuration is always giving me higher duty than the feed heater configuration.
And expectedly, stripping steam introduction to the reboiler column brings down the duty further.But I am not sure if this is an accepted configuration.In general I have seen that stripping steam goes with feed heater configuration and not with reboiler.What do the experts in the forum suggest??
Another point is that decrease in heater duty (feed heater or reboiler either) is accompanied by the decrease in vapor-liquid traffic in the column.Now the question is how low can I go on that (probably this is what we call overflash??)? I am using figure of 20 % based on total feed (naphtha+kerosene) liquid volume. How would it work when column is to operated at turndown, let's sy 40%??
Any comment is welcome.
Thanks.

 

[sav455]

And this is distillation based scheme. I have to get some cut from these two feeds.Sorry about missing on this information in the first post.

 

[Milutin]

Sav

It is not possible to produce diesel from kero and naphtha. What is your feed composition?

 

[sav455]

Ammm...I think I should not call it diesel.
This is a stream which is back end of naphtha and front end of kero or Distillate. Due to the 15 ppm thing and associated hydroprocessing limitation we have to produce some stream for internal consumption using distillation route. The only deemed feeds for the 15 ppm sulfur in diesel are naphtha and distillate as they have sulfur within limits.
Naphtha:
IBP: -18 (deg C)
FBP:233 (deg c)
Distillate:
IBP:132 degc
FBP: 390 deg c

Idea is to mix them together (or separately) and fractionate them to get the desired stream.Whatever I have done so far shows that we can produce some stream which meets, although on borderline, the 15 ppm diesel specifications.

sav

 

[dcasto]

What is the level of sulphur in each stream?

The process looks more like you are using one stream to strip/absorb sulphur from one to the other.

 

[Milutin]

Sav,

I suppose that you want to dilute higher sulphur content distillate (132 - 390degC) with low sulphur stream (-18 - 233degC). Before starting any simulation it necessary to check is it possible to get on spec diesel from blending desired cuts of that two streams.

Final diesel must have not only sulphur but also other properties like density, cetane number, etc on spec.
It means that quantity of low sulphur component in final blend will be limited by properties mentioned above, especially because heavier stream 132-390 already contain kero boiling range material.

Regards,

 

[sav455]

dcasto, the sulfur in Naphtha is 1 ppm and that in Distillate is 130 ppm. This is the total S content. I have the S distribution over the entire boiling range also,so I know what cut range we are looking for.

Milutin,Whatever preliminary work I have done shows that It is possible to meet all the specs of diesel, although very close to limit. Especially the API of the diesel which is very close to 45. The flash point spec is 55 degc which is possible to be also.This will a light material but within the diesel specs.

sav

 

[dcasto]

I wonder if you could use hot naptha vapors as a stripping medium to to get some of the sulphur out of the distillate. You,d use hot bottoms from the bottom to vaporize a naptha stream (partially) and use those to strip the distillate. The un flashed portion of the distillate could then be mixed with the stripped ditillate to get a diesel mixture.

From your title, is this mixture for wide distribution or just a local market? You can design a diesel engine to burn anything you know.