Carbon Disulfide in Naphtha

[dieselpet07]

Dear all members,

Very good morning to all of you !!

Carbon disulfide(CS2),which is sulfur derivative impurities being reported in light naptha of naptha splitter overhead situated at downstream of crude/vaccum/gas con unit.

Lot of theories are there for formation of corrosion speicies in crude column overhead like NH4HS,NH4(SO4)2 etc.but Is there any theory to form CS2 in Crude heater or column overhead, of course to form CS2 from CO2 coming along with crude & reaction with H2S may be require higher temperature and furnace is only source where almost 380-400 C temp. environment is there, other than that,Is there any way to identify source of CS2 which is being reported in light naptha.

Another theory is that people use CS2 as an additive during crude oil exploration,transportation to dilute asphaltene solubels.Boiling point temp. of CS2 is 46 C.

I seek & urge your valuable inputs/guidence how to investigate further to identify source of CS2 which is impurity for light naphtha.The level of concentration in N/s ovhd stream is in the range of 1-40 ppm & of course it could not be able to identify the exact correlation of inlet crude oil CS2 & CS2 reported in light naptha. So,how to investigate further for formation theory of CS2 in CDU/Gas con unit ?

Thanks in advance to all of you !!

 

[Milutin]

Hi dieselpet07,

Does CS2 in light naphtha cause any problems in process or equipment downstream of naphtha splitter or what is reason for your concern about CS2?

To investigate source of CS2, crude oil or process, you can tray to distillate crude oil in simple and inexpensive ASTM D-86 distillation of crude oil. Distillate cut up to 50degC and analyze cut on CS2. If CS2 is present in significant value crude oil is source.

If crude oil is not source vacuum hater can be source because of cracking, but gases from VDU is usually burned in vacuum heater, I am mot sure if that is your case.

Regards,

Milutin

 

[dieselpet07]

Dear Milutin,

This light naphtha goes for sell quite often so, that’s why it is area of concern .In fact, inlet crudemix window consists of quite different types of heavy & light crudes and apart from that few of the crudes have been analyzed in the past for inlet carbon disulfide once (no routine analysis) & in that it was found that Ras Gharib was having considerable CS2 in the range of 15 ppm for that parcel compare to others which were around 1 ppm, Intresting thing is that this crude is being restricted to max. 10 % in the feed to crudemix & not only that even when there was no RG processed in the crude those days also, naphtha had shown 10-15 ppm CS2 (being analyzed on routine basis) ,normally it varies from as minimum as 5 ppm to as high as 40 ppm in the naphtha.

The VDU Off gases are diverted to heater only for burning. I came across through googleing that CS2 sometimes upstream guys add to use as an excellent additive for asphaltene/wax solubility but how far one should think off for formation theory of CS2 in the process unit?


Thanks

 

[dieselpet07]

Hi, everyone,

after long time...I could find very good correlation for response of Naptha splitter overhead CS2 in light naphtha Vz. crude such as Eocene wt % of crude processed in the feed and wt % of Ras Gharib crude processed in the feed and coincidently these crude is having very high "Potential H2S" around 4600 ppm & 2600 ppm.I am looking some evidence that this potential H2S and Cracked CH4 in the crude heater along with CO2 , is there any possibility to form CS2 ( Crude heater temp. remains around remains 400-500 C).COT is 386 C.


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