6 replies to this topic

[robynjc]

Hi there,

I'm trying to find the flash point of a methanol/ water mixture in hysys. I've found the section in the cold properties in utilities where it tells you this, but it's empty. Looked on the aspen tech website and it suggests this is because the flash point temp is out of range. I've tried a bunch of different components, different compositions, different pressures and different fluid packages and I can't get any value to appear.

Is there something important that I'm missing. This seems like it should be fairly basic, but it won't work and I'm not sure what's going wrong. Sorry if this is a stupid question, I'm fairly new to this, help would be appreciated.

Thanks.

Edited by robynjc, 25 August 2011 - 10:21 PM.

[Zauberberg]

Have a look at: http://www.engineeri...ater-d_987.html

Not sure how accurate HYSYS will predict those figures, but you can access the "Calculator" engine by right-clicking on the stream and chosing "Show table" option and then clicking on it again, which will allow you to add more parameters/properties. Go to the "Calculator" option and see if any of the listed Flash Point calculations matches with what you need - make sure that the method specified (e.g. ASTM) is applicable for the type of compounds/chemicals you are interested in.

[PaoloPemi]

I would presume you wish to calculate the minimum temperature at which your components can form a ignitable mixture with air, if that is the case there are several methods available, see for example "http://www.uctm.edu/...va-291-296.pdf" , supposing you use Excel start from flammability limit and vapor composition...
I utilize a different software (Prode Properties) and I can't verify the operating of your simulator, however there could be several reasons, for example it requires that all components in the mixture have a specified flammability limit (which is not the case for water)

[robynjc]

Have a look at: http://www.engineeri...ater-d_987.html

Not sure how accurate HYSYS will predict those figures, but you can access the "Calculator" engine by right-clicking on the stream and chosing "Show table" option and then clicking on it again, which will allow you to add more parameters/properties. Go to the "Calculator" option and see if any of the listed Flash Point calculations matches with what you need - make sure that the method specified (e.g. ASTM) is applicable for the type of compounds/chemicals you are interested in.

Thanks for that, I want to look at mixtures with other components under a range of conditions added in as well, which is why I'm looking at using HYSYS- have you any suggestions for more accurate predictions if HYSYS isn't likely to be up to the job?

I'm after the ASTM D93 standard closed cup flash point, which I believe is the default value HYSYS gives. I've found the entry for this, it just won't return a value. The only reason that I can think of is that the values are outside those calculated by this method- as you suggest, it may not be appropriate for these compounds. Can you suggest where I can find more information on what methods are appropriate for what compounds. I never really knew there were different methods available until I started working on this project!

[Zauberberg]

The best place to look at these methods is the "Standard Index" - whether it is ASTM, or something else. Another option is to contact Customer service at ASTM, or an experienced industrial laboratory, and seek for advice. Perhaps someone from the forum can be of more help.

[GS81Process]

I would recommend looking up the flash point diagram for methanol/water/etc. binary and/or tertiary mixtures in published literature rather than trying to predict. I was able to find one source for methanol/water by doing a quick google search.

http://www.engineeri...ater-d_987.html


What property method are you using in HYSYS? I would not recommend using HYSYS to estimate closed cup ASTM D93 flashpoints when the lab tests have already been done for countless methanol mixtures. The hydrogen bonding in methanol systems can make physical property estimation difficult.

In case you are forced to estimate after exhausting the literature and you do not have appropriate lab access to have the ASTM test(s) performed, you could use the method in the following article:

http://www.nist.gov/...es/jpcrd695.pdf

Edited by GS81Process, 26 August 2011 - 11:48 AM.

[hshethna]

Have you tried to use the flash point property on a stream directly. If you go to the properties page and press the '+" sign. It will give you a tree selection of properties. Under Petroleum there is a property called Flash Point. Try it - it might work.