9 replies to this topic

[dhns]

Dear all,

could you anybody can explain about "HOW TO MEASURE THE FLASH POINT OF CRUDE OIL ?" by
theoritically or using simulation software(HYSYS).

thanks inadvance

regards,
dhn.

[ankur2061]

dhns,

You use the terminology "Measurement of Flash Point". Flash point is indeed measured using the "Cleveland Open Cup" and "Pensky-Marten" methods of measurement. I don't think there are any accurate theoretical methods for flash point.

Check out this link:

http://en.wikipedia....iki/Flash_point

This might help.

Regards,
Ankur.

[HMAlmosa]

I have been looking for an answer to your question for some time this year, as I needed to figure out how flash point of diesel will change if we mix with it light hydrocarbons (such as condensate). I came up with a theoritical method to calculate flash point if you have the composition of the liquid using a combination of Hysys and listed LEL (lower explosive limit) for various components.

In Hysys you can find the vapor pressure of a stream at any given temperature. This is the stream pressure when you specify a vapor fraction of 0.00 at a given temeprature. Hydrocarbon vapor concentration in the air is equal to (vapor pressure)/(atmospheric pressure). For example, if the vapor pressure of a mixture at 100F is equal to 1 psia, then concentration equals 1/14.7= 6.8%. Hysys will also give you the vapor composition in equilibrium with your liquid. Find the average LEL concentration for that vapor composition by prorating the composition (you can find LEL for individual components from GPSA).

Definition of LEL is "the lowest concentration of hydrocarbon in the air that can cause a sustainable flame"

Definition of flash point is "the temperature at which there is enough vapor above the liquid to ignite in the presence of an ignition source"

You can see that the definitions are very similar. In other words you could say that flash point is defined as "the temperature at which vapor pressure of the liquid yields a vapor concentration in the air above the liquid equal LEL"

Using this method you will find out that the flash point of a mixture is always close to the flash point of the lightest components of your mixture. You will notice that flash point of most crude oil mixtures will be when the vapor pressure is somewhere between 0.15 and 0.25 psia.

I hope this helps.

[Zauberberg]

Below is the list of available standard methods for measuring flash point of petroleum cuts. The ones which are most commonly used are ASTM D93 and IP35:

http://www.intertek-...petroleum.shtml

Flash point correlates to 10% D86 distillation point/slope; similar approach is used by HYSYS for flash point estimation.

[Alawi]

Hello Mr. Zauberberg,

I hope you are well, do you happen to know what exact method is used for measuring the Flash point of Crude Oil? the link you gave shows about sixteen different test methods. The Flash point of crude is relatively low “Some references use a value of around -20 C” therefore most commonly used flash measuring instruments may need some modification before been able to make such measurements as the crude sample should be cooled down, I have not made such measurement but maybe you can cool the sample in a separate apparatus then make the needed test.
You also mentioned that the Flash point correlates to 10% D86 distillation point/slope, can you refer the source of this correlation.

Salam

[rxnarang]

Another convienient equation is by the fire researchers at Factory Mutual:

t_F=0.683t_B-71.7

whre
tF = closed cup flash point ( °C)
tB= initial boiling point (°C) or NBP for pure compounds.


Regards

[JoeWong]

Another convienient equation is by the fire researchers at Factory Mutual:

t_F=0.683t_B-71.7

whre
tF = closed cup flash point ( °C)
tB= initial boiling point (°C) or NBP for pure compounds.


Regards

Can you advise the exact reference ? Thx-in-Adv.

[WooTz]

hi all,

I have not seen the answers above, the one formula only works for pure components and not mixtures I assume.

What was the reference of correlating flash point to the 10% distillation point D86?

Best Regards,
Martin

[Padmakar Katre]

Dear,
Addition to Zauberberg's reply 10% D86 distillation temperature based Flash point is ok with the CDU products like HNaphtha,ATF,Kero,GO but for heavies like 360C(+) material I used a graphica method with the D1160 distillation. Generate Bubble pressures(psia) the products streams (in my case it were the lube cuts from VDUs) @ the temperature rane of say 30 Deg C e.g. Spindle Oil have a spec of F.P. 170 Deg C so get the data of Bubble pressure @ 150,160,170,180,190,200 Deg C temperature and MolWt. Now plot the MolWt*BubblePressure Vs Temperature and where the MolWt*Bubble presure value of 15.1 intersect the graph record the temperature i.e. flash point for the said product.

Edited by Padmakar S Katre, 08 December 2009 - 10:28 AM.

[atbell]

So I'm an engineer by training but I do more with economics / media now than engineering.

This means I keep company with fairly creative people, get access to all kinds of wild and wonderful theories, and have lost my technical edge.

One of my more aware friends pointed out that there's an oil slick that keeps getting bigger in the gulf of mexico, that there's a yearly hurricane season that goes through the gulf, and that an oil/water/air mixture raining down on the US sounds very flamable.

... and hurricanes have lots of lightning.

So I'd be interested to know if this theorizing is idle (pun) speculation or if we should be expecting a full on biblical style external combustion engine of a hurricane season to rain down on Florida this year. (see, sensasionalisim is a habit I've picked up from the media part of my life).

Let me know what you think / know. I'm doing my own work into things like figuring out what kind of fuel / oil / air mixture could be expected to be picked up by hurricanes.

Feel free to message me directly via PM or right to my e-mail (atbell at hotmail dot com) because I'd like to get right on this one if the conclusions turn out to be negative. Hurricane seasons starts on June 1st if I'm not mistaken.

Andrew

Also, in the interest of full disclosure and quickly building some amount of credibility, my life is pretty much on display via facebook (same e-mail) so do some snooping to confirm the reality of 'me' if needed.