3 replies to this topic

[ken0564]

Hi

 

Is there a general rule of thumb when it come to strippping steam in the atmospheric column of a Crude unit?

For example, if I am running at 40Kbpd does the stripping steam rate change when I increase to 70Kpd?  I was wondering if ther is a chart or something which correlates the two.

 

Thanks for your help in advance

[gegio1960]

ken,

in my experience, stripping steam flowrates on an operating CDU are field-tuning parameters: one should take them at a minimum, for each stripper (and bottom), to obtain the required product qualities (eg flash point, gap/overlap, etc).

Generally speaking, without changing the crude, if you already have the flowrates at 40 KBPD and the increase to 70 KBPD doesn't affect the operation of the various sections of the tower (ie no presence of bottlenecks), you could simply increase the flowrates by the multiplier 7/4.

Anyway, a re-tuning should be made to verify the effects of the changes, especially thinking that, in this case, the unit thruput is going to be increased by 75% (not peanuts, unless your CDU is running well below its design flowrate, you'll need a revamp to manage this change!).

Rules of thumb are applicable in the design phase of the CDU, mainly to define size of steam control valves and quantity of (sour) water to be recovered in the overhead system (and consequentky to be treated/recycled downstream).

Hope this help.

regards

[suhas]

General rule of thumb is use 2-3 #/BBL of the product withdrawn.

[Himanshu Sharma]

Ken0564

 

I assume that you have etsbalished Tray Hydrualics for the column and etsbalished that column and associates is suitable for revamp operation for this capacity increase.

 

I say this, becuase i have a concern here for Flash Zone Temperature and overflash which is dependent on flash zone pressure and bottom stripping rate.

 

A general rue of thumb for  starting  simulation of crude tower is steam rate of 4-6 lb/bbl of crude input,however this rate is often optimized at site and in most of the cases its is lower than design.