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Purpose Of Direct Steam Injection In Diesel Stripper Column


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#1 Venkat1989

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Posted 29 March 2020 - 07:48 PM

I am in Diesel hydro-treater unit, the diesel stripper uses direct steam injection as stripping media, whereas the stripper in Pre-desulphurization unit of Hydrogen generation unit contains re-boiler, both columns intention is to strip out light ends along with H2S.

 

How exactly direct steam injection is helping the stripper column operation over re-boiler mode? Awaiting for your replies. Thank you.



#2 PingPong

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Posted 30 March 2020 - 07:13 AM

..... the stripper in Pre-desulphurization unit of Hydrogen generation unit contains re-boiler .....
It is not clear to me what kind of stripper that is.

What fluid is being stripped there? And at what reboiler temperature?

 

 

Now ask yourself: what reboiler temperature would be required to reboil diesel at the pressure of the stripper in an HDS unit (run a process simulator if you have no idea), and how would you achieve such temperature?



#3 Technical Bard

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Posted 30 March 2020 - 05:12 PM

Steam stripping is used when the temperature required to BOIL the liquid product is higher than an available utility.  Commonly, Diesel and heavier strippers will use steam injection to lower the partial pressure of light components, inducing them to vaporize.  In naphtha and kerosene, it is possible reboil these strippers with steam or hot oils.  



#4 PingPong

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Posted 01 April 2020 - 09:51 AM

@Chalapathi

 

If you would calculate the required reboiler temperature at the HDS stripper pressure I expect you would find something in the range of 350 to 400 oC.

To achieve that you would need a fired heater, which costs both investment and fuel.

 

I once saw an old HDS unit stripper with a fired heater reboiler. We revamped the design into steam stripping. The heater was re-used in another service.

 

Steam stripping does save cost, however it also increases sour water production.



#5 Venkat1989

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Posted 02 April 2020 - 11:59 AM

Thanks all, for your valuable comments.

 

May I Know, how to decide the amount of steam required and bottom temperature of the stripper that needs to be maintained to get rid of the H2S in the feed that is going to stripper?

 

Is there any relation between stripper bottom temperature that needs to be maintained and amount of H2S available in the feed to the stripper?


Edited by Chalapathi, 02 April 2020 - 12:01 PM.


#6 PingPong

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Posted 03 April 2020 - 03:21 AM

In general: the feed to the stripper will be hot.

The amount of stripping steam required depends on this feed temperature, the stripper pressure, the number of stripping trays, the amount of H2S in the feed, the max allowable amount of H2S in the bottoms product.

 

Is this topic about an existing HDS unit with stripper?

 

Or is this topic about a new design?


Edited by PingPong, 03 April 2020 - 03:37 AM.





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