13 replies to this topic

[DTM]

hi guys/ girls.. as i'm need of thermodynamic properties of Liquefied petroleum gas, with any compositions of propane and butane. I would like to get this properties from any u people.

thanks

[JoeWong]

Pretty common nowsday to get properties from process simulator i.e. HYSYS, PRO-II, etc

[DTM]

Thanks a lot Joewong, but values obtianed for 100%propane and 100% butane is not matching with the values (what we get from HYSYS).do u have the softwares with u?
u can mail me miss.thiruselvi@gmail.com.

Pretty common nowsday to get properties from process simulator i.e. HYSYS, PRO-II, etc

[DTM]

Joewong,

Actually i tried with HYSYS for the composition of 60% propane and 40% butane and in order to cross check it, i got the values for 100% propane and 100% butane and compared with the values in Perry's chemical Engineers hand book, but the values for pure propane and butane were not not matching with the values in the book,so how can i believe the obtaine value for Composition of both propane and butane is correct.

this is my opinion, u can suggest me something to do with my project work.pls.

[ankur2061]

Joewong,

Actually i tried with HYSYS for the composition of 60% propane and 40% butane and in order to cross check it, i got the values for 100% propane and 100% butane and compared with the values in Perry's chemical Engineers hand book, but the values for pure propane and butane were not not matching with the values in the book,so how can i believe the obtaine value for Composition of both propane and butane is correct.

this is my opinion, u can suggest me something to do with my project work.pls.

DTM,

Which version of HYSYS are you using? What EOS package in HYSYS are you using to determine the stream properties? What properties are you trying to match with figures in Perry's Handbook? You should clarify what exactly are you looking for?

I don't think Perry has any data on a saturated mixture of Propane and Butane with a composition of 60% Propane and 40% Butane.

Unless you are able to clarify all what has been asked, I am afraid it would be very difficult to help you.

Regards,
Ankur.

[DTM]

Ankur,

i have used HYSYS 3.2 version.

I think, u didn't get me, bcz perry is having the details on the thermodynamic properties of pure propane (100%) and butane(100%), so making use of that HYSYS software, i got the values for Enthalpy , entropy and many parameters and compared with the Perry's value. But it does'nt get matched.

So how can i consider the values for LPG composition is correct..? since i'm doing my project work on process safety, my guide is asking for the cross reference data on LPG composition. In order to check the obtained value..

shall i give the pressure and temperture values, 'll u give the property values of the mixture at any composition.
i have attached the excel sheet which contains the pressure and temperture values for both propane and butane u can give me the thermodynamic properties of LPg at any composition(60% propane,40% butane) or (70% ,30%)

thanks..

Attached Files

•  Copy_of_LPG_prop_trial_2.xls   19KB   155 downloads

[Art Montemayor]

DTM:

It is you that is not “getting it”. And the reason you fail to understand is that you are confusing yourself and others at the same time. I believe we all know this is not on purpose; you simply have not focused on the specific details.

You failed to answer Ankur’s specific question(s): “What properties are you trying to match with figures in Perry's Handbook? You should clarify what exactly are you looking for.” And by not giving importance to Ankur’s leading questions, you failed to state the most important part of your query – which you have not defined: The properties you are seeking are the SATURATED properties – as differentiated from the superheated properties.

You don’t even state where you obtained your saturated temperature and pressures shown on your Workbook. Engineers cannot present sloppy data such as that. You must be specific if you are to be correct in your work. I have augmented your Workbook with the correct, specific, saturated properties of Propane and Butane as taken from the NIST database – which is clearly referenced in the data given. Also note that the reference bases for internal energy and entropy are clearly stated.

Note that the pressures and temperatures you gave are clearly those of the saturated state. Why didn’t you just tell us that in the first place? By using the NIST database (which is also clearly referenced and hyper-linked), you can now obtain any thermodynamic value for Propane or Butane. By using the mixing rules, you can obtain estimates on the properties of any mixture of the two.

I hope you realize how helpful Ankur was trying to be in order to help you. You do not have a language problem in trying to communicate. You simply have not communicated as an engineer should – with clarity and specifics.

I hope this helps you.
 Propane___Butane_Thermo_Properties.xls   46KB   235 downloads

[djack77494]

Actually i tried with HYSYS for the composition of 60% propane and 40% butane and in order to cross check it, i got the values for 100% propane and 100% butane and compared with the values in Perry's chemical Engineers hand book, but the values for pure propane and butane were not not matching with the values in the book,so how can i believe the obtaine value for Composition of both propane and butane is correct.

DTM,
If you follow the postings in these forums, you will see that one of the most important tools used by forum contributors is the process simulator. We all use simulators, and, if anything, rely on them excessively. So I'm a bit surprised to see someone who is apparently a newbie (often excessively simulator-dependent) complaining that the results obtained from a simulator couldn't be trusted. Furthermore, it is in dealing with very elementary and nearly ideal compounds that are well understood and well represented in the simulators. I have to suggest the problem is with YOU and not with the simulator. My take on other responses is that this is a common thought. Check the EOS and methodology selected. If necessary, generate a simple model to look at pure propane and pure butane. If you don't get VERY close agreement with published data, then YOU are doing something wrong. If you do that and still need help, then you're going to have to do a good job of fully detailing the specifics of your model.

[DTM]

Art Montemayor,

Thanks for helping me.sorry!! (for not explaining that it should be in saturated state). ok I'll try to work out and find the values by making use of the mixing rules.

But now, when i compare the values of Enthalpy and entropy (which i have attached with this rply), obtained from the Perry's physical and chemical data, chapter 2 of seventh edition,with the values send by u (from the NIST web book)
The values are getting varried, i cant able to find the reason. U can also check once, if u dont believe my words.

now i'm pretty doubt to use which value for my work...

Thanks a lot for responding me...

Attached Files

•  Copy_of_LPG_prop_trial_2.xls   249.5KB   88 downloads

[MrShorty]

I haven't thoroughly evaluated the two references, but my first thought when looking at the two references is: what are they using for reference values? Enthalpy in particular cannot be an absolute value -- it is always a difference from some "reference" condition. Neither spreadsheet explicitly states what they are using for the reference condition, so it seems likely to me that the difference in enthalpy values is simply different reference conditions. Maybe that's also the reason for the discrepancy between your simulator output and literature.

[Art Montemayor]

DTM:

Your communicating still persists in being confusing to the reader.

Please, when you communicate with other engineers, be concise and accurate. For example, you claim that enthalpy and entropy values taken from Perry’s Handbook are different from those of the NIST database. You literally cut and pasted what seems to be the Perry values (in different units) and claim they are different. PLEASE communicate as an engineer. Construct three tables (as I have started in the attached Workbook, in the "butane" worksheet), each side-by-side. One table is for the HySys data, the next one for the Perry data, and the third one for the NIST data. Show the base values of the SATURATED temperatures and pressures, the corresponding enthalpy values and the entropy values in each table. SHOW ALL UNITS CLEARLY AND THEY SHOULD BE THE SAME. DO NOT COMPARE BETWEEN DIFFERENT UNITS. WE ARE NOT GOING TO DO YOUR UNITS CONVERSION FOR YOU.

Note that I have edited your so-called Perry’s database information and identification of units. DO NOT BLINDLY COPY PERRY INFORMATION. EXPLAIN WHICH ENTHALPY AND ENTROPY IS FOR THE SATURATED LIQUID AND WHICH IS FOR THE SATURATED VAPOR. FOLLOW THE SAME METHOD AS THE NIST DOES. Your explanations of hf, hg, sf, and sg are incomplete. This shows sloppy communications and is not understandable.

When you have finished constructing your 3 comparison tables, use “call outs” to identify those data that are in conflict or are “varied” (as you state). If you do not present your data accurately, clearly, and concisely, we cannot comment on your problem – if there indeed is a problem in the first place.

Use the same Workbook that I have attached in this posting. When you make your revisions (include your tables and make any other revisions to this workbook, RETITLE IT WITH A SUCCEEDING REVISION NUMBER (2). That way, we know who did what, when, and where.
 LPG_Prop___Rev1.xls   279KB   152 downloads

[DTM]

Art Montemayor,


sir, I have checked the saturated thermodynamic values of propane and butane of NIST with the saturated thermodynamic properties of seventh edition Perry's (even after the unit conversion). but, i found it to be varrying.

Then i compared the Eight edition perry's value (after unit conversion) with NIST values, i found both are same. so now i got the data for the thermodynamic properties of pure saturated propane and butane.

then after discussing with my project guide, i found there was the difference in the reference data used for the calculation in 7th and 8th edition of perry's. i have attached the excel sheet which contains the comparitive data for butane.

now i need the suggestion in mixings rules, (for manual calculation) which can be used for the determination of mixture properties of LPG with any of the composition 60% propane and 40% butane, or 70% propane and 30 % butane.

Help me, by giving the ideas for getting the thermodynamic properties of the LPG.


thanks a lot.

[Edgar martínez(chemical)]

if you are working for the distribution side of the bussiness, i.e. towards the user of LPG you cau use the methods and data shown in an old but very widely used book in the lpg trade. The butan-propane gases handbook. it is out of print but it is wporth a seach in the net.

The calculation is a ponderation of the property using the mole fraction, just be sure to specify if the percentages in the mix you are considering are in a volume or in a weight basis. It is rather common to specify the composition as percentage wothout taking the extra effort to specify the basis.

The acostummed basis vary from country to country so make sure to find out whis is the case for your mix.

small differences in the property values are of no significance in the distribution side of the lpg bussiness, where we are normally only faced eith pipe sizesing for the vapor phase or the selection of a pump or compressor.

In mexico we normally have an lpg which is a c3/C4 mixture but calculate our pipes and equipmnet for the mos unfavorable chemical composition, which by the way is not always straigh propane.

hope the information helps you

[Padmakar Katre]

Joewong,

Actually i tried with HYSYS for the composition of 60% propane and 40% butane and in order to cross check it, i got the values for 100% propane and 100% butane and compared with the values in Perry's chemical Engineers hand book, but the values for pure propane and butane were not not matching with the values in the book,so how can i believe the obtaine value for Composition of both propane and butane is correct.

this is my opinion, u can suggest me something to do with my project work.pls.

Dear Have you reported this incident to Aspen-Tech.