8 replies to this topic

[mohammad reza]

Dears

 

Is there any criteria or guideline for  stripping steam temperature?

 

Thanks in advance.

 

Best Regards

Mohammad reza

[Bobby Strain]

Steam for what purpose?

[mohammad reza]

Steam for what purpose?

Steam fro stripping , for example in crude distillation column or relevant side stripper, in hydrotreater stripper column.

[PingPong]

Stripping steam must always be taken from a superheated steam header to avoid steam explosion in the column if steam condensate would enter the column together with the steam.

 

So if you want to use LP steam (3.5 barg, 50 psig) as stripping steam for an atmospheric crude column or a vacuum column, that LP steam shall be superheated well above its saturation temperature.

Preferably that superheat is achieved by heating steam from the LP header to at least 250 ^oC in the convection bank of the heater upstream the crude or vacuum column.

 

Creating superheated LP steam from saturated HP steam by simply reducing the pressure is therefor not a good idea.

Although depressurizing 40 bar saturated (but dry) HP steam would in theory produce superheated LP steam, you can never be sure that that LP steam will never contain some condensate as you cannot possibly know how much condensate could, every now and then or due to an upset in the HP system, be present in the saturated HP steam.

[mohammad reza]

Dear Pingpong

 

Is there any criteria/rule between stripping steam temperature and bottom product temperature?

[PingPong]

Not really.

Some people would recommend a stripping steam temperature that is roughly that of the stripped liquid, but that is really arbitrary, based on gut feeling.

 

Steam stripping is an adiabatic process, so the hotter the stripping steam the better, but as the amount of stripping steam is very small compared to the stripped liquid the effect of steam temperature on strip-out is also small. Moreover one can use slightly more stripping steam to compensate for a lower stripping steam temperature.

 

If you have access to a process simulator you can easily determine the effect of steam temperature as well as steam quantity in your specific stripper.

 

In any case: select a stripping steam temperature between 250 ^oC and the maximum allowable operating temperature of the stripping column.

[Arsal]

I dont know the standard of stripping steam temperature.

 

Some Refineries are using LP steam directly without superheated at 40 Psig and 150 C temperature that is above saturation temperature.But the amount of steam has been increased and the risk of condensate to carry out with steam is also increased.

 

Normally, The steam is superheated near to tranfer line temperature of Crude oil but this is not a standard practice.

[Arsal]

You can also find similar discussion on below link.

 

http://www.cheresour...am-temperature/

[PingPong]

I missed that other topic.

 

Once again: the main purpose of a considerable steam superheat is to assure that no condensate can enter the column causing a steam explosion that would blow out the stripping trays.

 

In the old days, when design were made by experienced engineers that knew what they were doing, stripping steam was therefor superheated in the convection bank of the heater upstream the column.

 

Nowadays some designs are done by young inexperienced engineers that only know how Hysys works. So nowadays there are columns built that use saturated stripping steam (or other design mistakes), because Hysys does not warn for stupid designs.

 

Every column that uses saturated steam for stripping will sooner or later experience a steam explosion, so don't do that.

Edited by PingPong, 18 July 2016 - 03:55 AM.