4 replies to this topic

[BJD]

I would like to know how temperature of stripping steam used in the fractional distillation column can effect the separation/recovery ? how the Diesel recovery and various distillation cut points got affected if the tempearture of stripping steam is reduced at constant pressure? 

 

what will happen to the distillation/recovery of product  if we use staurated steam in stead of superheated steam in the hydrocracker fractionator/distillation column ? 

 

Regards,

[PingPong]

Never use saturated steam for stripping steam, because that can (and probably will) contain free water that can cause a steam explosion in the fractionator, resulting in severe damage to the stripping trays.

 

The steam temperature has some impact on the amount of light components being stripped out of the liquid, because of its heat content, as stripping is an adiabatic process.

[BJD]

Thank you pingpong.

 

Do you mean that light component may not be properly stripped off from middle distillate product (which eventually may reduce the flash point)due to less heat content of steam if the stripping steam temperature is reduced  ?

[PingPong]

Yes, if the strip steam temperature is lowered you will need a little more stripping steam to achieve the same product flash point.

 

You can use a simulator to determine the exact impact.

[pavanayi]

The whole point of steam being superheated is to prevent condensation in the headers. Also, temperature of the steam affects the volumetric flow rate and hence the partial pressure inside the column, thus affecting the stripping.

 

If the steam to the column is suspected to be of near saturation, then a knock out pot can be considered just upstream of the inlet into the column to take out any condensed droplets. As mentioned earlier, if the effect is not considered properly, serious damage can occur to the column internals. There have seen such cases  (though rare) which have operated without major problems. 

 

LP Steam saturation temperature might be around 150°C  whereas the temperature inside the column will be higher so that the small distance from the knockout pot into the column wouldn't present a significant problem.

 

These instances are considered when a new energy recovery project proposes a LP Steam generator which uses heat from the product streams and can be located near to the column.

 

Pavanayi 

Edited by pavanayi, 27 November 2014 - 06:47 AM.