Q & A > Question Details
Where can I obtain information about Vacuum distillation unit overhead sourgas minimization?
What are the parameters that effect the sour gas generation rate? Are there any correlations available to relate those parameters to sourgas rate?
What are the methods and ways to minimize the cracking of reduced crude oil in vacuum unit charge heater? what are the main effecting parameters of fouling the vacuum charge heater?
25/11/2009 A: Vishnu Ram A S, RIL, vishnu.selvaraj@ril.com
This could be obtained only by experience as I also could not find in any articles. I can suggest few things:
1. Keep attacking against your cracking in the atmospheric column itself by increasing the recovery; You can check the stripping section efficiency and also take maximum of HAGO; Because this HAGO will be loaded in the vacuum column increasing the C-factor and also increase the Vacuum furnace load; Keep the Crude furnace COT max. with type of crude you process in mind Ex;Ras Garibh Crude cracks at low temp.
2. Check the Delta P of the Overflash bed (Slopwax)- should not be high as it increases the back pressure for the flash zone and enhanses cracking.
3. Turbulizing steam in the heater coils can be increased and be monitored for the minimization of Cracked Off gasses.
4. Increase the vacuum to max. Also check the Column Delta P remains the same and C factor.
5. Check for the Oxygen percentage in the Off gasses and back pressure of the ejectors which might gives you an idea why the cracking happens; Also analyse the Cracked oil obtained in the overhead.
Finally to summarise, Cracking happens due to be specific crude blends and even then we can obtain our valuable products by just changing the parameters with little allowable contraints in hand.
09/02/2009 A: Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
In addition to temperature and residence time, cracking is a function of the specific crude oils being processed. Different crudes will evolve differing amounts of H2S as a function of temperature. The amount of H2S formed and the temperature it forms at is dependent on the specific sulfur species present and their quantity. I am not aware of any generic correlations that allow prediction of gas evolution in a vacuum heater.
Fouling in the heater is a complex issue. Furnace design will influence fouling - heat flux, velocity/residence time and localized flame patterns are all important in determining the amount of fouling. As the amount of cracking/gas formation increases, fouling will also increase. Asphaltene stability of the oil can also be a factor as can be the presence of inorganic solids (corrosion products, salt, clay, sand, etc.)
09/02/2009 A: keith bowers, B and B Consulting, kebowers47@gmail.com
'Sour Gas' from a vacuum distillation unit depends upon the crude oil AND furnace coil operating conditions. Crudes are the biggest variable. Some with high sulfur concentrations have very stable sulfur compounds and 'make' little sour gas. Others with moderate total sulfur produce a lot of H2S in the fired heater.
09/02/2009 A: Samuel Sinanan, IPSL, Samuel.Sinanan@ipsl.co.tt
The sour gas or offgas generation rate is dependent on the extent of thermal cracking that takes place in the vacuum heater. To minimize cracking you need to reduce your vacuum heater transfer temperature (at the expense of distillate yield) and also increase your velocity in the tubes of your heater possible by injecting steam.