Q & A > Question Details
The most common (in fact just ) application is stripping steam for stripping at the Crude distillation units. Is there any alternative to stripping steam, such as nitrogen, for stripping of steam at a Crude distillation unit? Is there a literature/research? What are the advantages or disadvantages?
07/01/2017 A: Mainak Sarkar, Indianoil Corporation Ltd, sarkarm@indianoil.in
For stripping purpose generally steam is used. However, N2 or any other gas viz. CO2, Helium etc. may be also used for stripping purpose, at least theoretically. But these type of gases are not used because of the following reasons:
1. Steam is the cheapest among all gases mentioned above.
2. Steam also acts as a source of heat, but for other options you need to heat them. The heat capacity of all gases are lower than water/steam.
3. Steam is condensable and gets separate easily from Reflux drum boot. But for other options they will end up in the Fuel gas header. This will further cause problem as it will reduce the calorific value of FG.
4. But in few discussions I have heard the use of FG as stripping medium, then the problems discussed in point 3 will be nullified.
04/01/2017 A: Eric Hennings, Technip Stone & Webster, EHennings@technip.com
Generally, stripping with steam is more economical than with gas. In addition, low pressure effluent gas must be compressed for recovery.
The drawback of stripping with steam is that the sidecut product (such as kerosene) will be water saturated. This is generally not an issue if the intermediate stream is being reprocessed (e.g sulfur removal) in a downstream process.
Some refiners will "reboil" a sidecut using hot process, particularly if it is advantageous to remove water at this stage in the process.
Disposition of effluent brine water from desalters is sometimes gas stripped and oxidized to reduce benzene or COD.