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Question Details
 
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Question No.:  5190 Category :  Refining Operations
Date Posted:  2/13/2010
Subject: Distillation
 
Question:
Why stripping steam is used in crude distillation column?
Submitted by :
Name:
Company Name:
Location:
EMail:

Prakash Nagrikar
Essar Oil Ltd.
Jamnagar, Gujarat
prakashfnagrikar@gmail.com


 

Number of responses : 4
Response 5190-1
Date : 2/16/2010

Most refineries are using fired heater in upstream of crude distillation column. In rare cases they are using stripping steam where cruse and capacity of column is very less. We also using fired heater (48 burners) in CDU (14MMTPA).

Name - Krunal
CompanyName - Parmar
Location - Jamnagar , Gujarat , India
Email - krunal_vapi@yahoo.com

Response 5190-2
Date : 2/26/2010

Stripping steam at the column bottom helps in stripping the lighters from the heaviers and contributes to lower the partial pressure and hence boiling point.

Name - V. K. Kapoor
CompanyName - Petroleum Refining Consultant
Location - Dehradun , Uttarakhand , India
Email - vkkapoor9@yahoo.com

Response 5190-3
Date : 2/28/2010

Crude distillation unit uses fired feed furnaces and stripping steam in the bottom of the atmospheric column and each side stripper column. Stripping steam is used in the vacuum column, too, unless it is operated as a dry vacuum unit. The function of the steam is to improve (sharpen) the separation between adjacent product streams (cuts) to optimize the yields of the most valuable product from the unit. However, if each stream from the crude unit, except perhaps the bottoms product, is hydro treated and thus re-fractionated downstream of the reactor section of each hydrotreator, thus providing another opportunity to sharpen the fractionation and optimize the yields, it makes one wonder why we try so hard in the crude unit to sharpen the cuts.

Name - Ralph Ragsdale
CompanyName - Ragsdale Refining Courses
Location - Houston, Texas, USA
Email - ragsdales@juno.com

Response 5190-4
Date : 3/11/2010

For understanding purpose, consider binary component (A+B) distillation. According to Dalton's law, pa + pb = Pt, i.e., "pa" is the partial pressure of component A and "pb" is the partial pressure of component B in a mixture, it will be equal to the total pressure.

Consider "pa" = 0.6 bar and "pb" = 0.4 bar, hence the total pressure is 1 bar. In general, relative volatility is more separation, is easier. i.e., difference in partial "pr" is more separation, is easier.

Introduce steam which has partial pressure "ps" = 0.1 bar, now the total pressure is fixed at 1 bar. After introducing steam, partial pressure of either of the component has to decrease. Say, it lowers the partial pressure of Component B hence "pb" = 0.3, now pa + pb + ps = 1 bar (0.6 + 0.3 + 0.1 = "Pt"). Relative volatility is increased.

Hence, steam stripping helps to reduce the partial pressure of the component.

Name - M. Murali
CompanyName - Petrofac Engineering Services India Pvt. Ltd.
Location - Chennai, TamilNadu, India
Email - murali.m@petrofac.com

 




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