19 replies to this topic

[ankur2061]

Dear All,

HYSYS has a utility for hydrate formation temperature prediction for the corresponding gas composition, pressure & temperature. Does anyone have an idea what empirical correlations or equations they use to determine the hydrate formation temperature.? Also, how accurate are the calculated values & their reliability? Does anyone know of numerical methods to calculate the hydrate temperature formation using, say an excel spreadsheet?

Regards,
Ankur.

[Esteban Lopez]

You can find some info about the hydrate in HYSYS help.

I will check the manuals I have to see if they explain the correlation they used for

I hope that with the help option you can figure out the relations

[ankur2061]

Esteban,

The HYSYS help did not mention anything except that there are two models to be used for hydrate formation:

1. 2-phase model without a free-water phase
2. 3-phase model when the gas hydrate is in equilibrium with free-water phase.

Can you dig up some more information. Meanwhile I will continue looking.

Regards,
Ankur.

[shan]

I can only pass the comment from my ExxonMoble client a few years ago. He told me that Hysys hydrate prediction is too conservative. They contracted a Canada company specialized in hydration to do hydrate calculation.

[Padmakar Katre]

Dear,
Try to get the theory and design guides from the gas processing handbooks.

[ankur2061]

Dear All,

An excellent reference on gas hydrate formation is available at:

https://etd.tamu.edu....pdf?sequence=4

However, in section 2.7.3 of the above mentioned reference, the units used by the author for the 'Kobayashi' method are given in bar for pressure & deg C for temperature. It is important to note that the reference the author gives for the correlation in 2.7.3 is of the following renowned text:

Chapter 25, Phase Behaviour of Water/Hydrocarbon Systems, Petroleum Engineering Handbook by H. B. Bradley.

In this (pg 25-13) the same equation is mentioned with pressure units of psia & temperature units of R.

I used this regression equation with both units and somehow the results appear to be totally off the mark for both sets of units. I seem to be lost on this & need help.

I would request some petroleum expert (or more precisely a gas hydrate formation expert) to throw light on this.

The author of the paper mentioned in the link above is a distinguished alumni of 'Texas A&M' by the name of 'Sharareh Ameripour' with unfortunately no e-mail address. Any possibility that I could contact her & discuss her master's thesis on gas hydrate formation.

Additionally two of the topmost academicians on hydrocarbon/water phase behaviour are from 'Rice University' by the name of 'Ricky Kobayashi' & 'K. Y. Song'. Any means of corresponding with them. Another expert in gas hydrates is a distinguished academician 'E. Dendy Sloan' from the 'Colorado School of Mines'. Art Montemayor, could you help on this.

Would appreciate any help from some of our well known names like Art Montemayor, Harvey, Zauberberg, Joe Wong, Doug, since I am trying to develop a spreadsheeting solution for gas hydrate formation temperature for a given pressure & vice versa for a given gas composition.

Regards,
Ankur.

[VikingUK]

Try this programme

Attached Files

•  CSMHyd.zip   186.25KB   1184 downloads

[ankur2061]

VikingUK,

Thanks a lot. This is really good.

However, I am being a bit greedy by asking you if there is a windows version for this old DOS program. If yes, can you provide it.

Regards,
Ankur.

[VikingUK]

No, it's DOS only. Sorry...

VikingUK,

[ankur2061]

Dear All,

The hydrate formation utility in HYSYS is not considered to be accurate by some including "Shell". There are some empirical correlations available which calculate the hydrate formation given the natural gas specific gravity & the gas saturation pressure. Some correlations provided by some authors are "Motiee", "Mokhatab" & "Ostergaard".

A new correlation based on gas saturation pressure & Molecular Weight of the gas is given in the following link:

http://www.jngc.org/...hang/090409.pdf

Some commercial hydrate prediction software are available as follows:

1. Hydrate Plus 1.12

2. WatGas

3. AQUAlibrium

Demo versions of software 1 & 2 are available. I have checked the results of the new correlation as given in the link with the results of software 1 & 2, and they are in fair agreement.
The new correlation as given in the link is quite promising and is programmable as a spreadsheet.

Regards,
Ankur.

Edited by ankur2061, 07 July 2010 - 10:29 AM.

[Propacket]

Ankur,

• A method for estimation of hydrate formation temperature is also provided in GPSA Chapter 20. But its main disadvantage is that it is not programmable because it makes use of different graphs provided therein.

• As far as I understand, the correlation provided as per the above link does not take into account the addition of hydrate inhibitor. How would we calculate the hydrate formation temperature if we use a hydrate inhibitor?

Edited by P.Engr, 07 July 2010 - 12:14 AM.

[ankur2061]

P. Engr,

I am aware of the GPSA chart also known as Baille-Wichert chart & it's limitation in being programmed as a equation.

As far as hydrate inhibition is concerned , the "Hammerschmidt" equation is a widely accepted equation for estimating hydrate inhibitior injection rates given the hydrate depresion temperature. The equation is easily programmable as a spreadsheet. The inputs required are the water content of the gas at the initial & final pressures. I have already programmed it as a spreadsheet.

The main concern of my earlier post was the reliability of HYSYS as a simulation tool for hydrate formation conditions & estimating hydrate inhibitor rates.

Regards,
Ankur.

[henrylcl]

Hello to all,

May i get some help from you all about gas hydrate prediction below 0 degree celcius. I am now doing the gas hydrate prediction project and now is using the HYSYS. I am able to predict the formation pressure by give the input of temperature in HYSYS. But, not for temperature below 0 C, as the result just indicate "Ices form first" without stating the formation pressure.
May i know someone who is familiar with hysys can suggest a solution for me. During the process, i just provide a feed with composition of methane, water and CO2,together with condition of temperature ,molar flow and pressure. i get the result by clicking on "performance - add utility (hydrate formation utility) to see the formation pressure.

[PaoloPemi]

I would include in the list Prode Properties, in my experience results are comparable with those of the software from Colorado University, unfortunately the free student's version (available at www.prode.com) doens't include the procedure (it is in commercial version).

[Engineeringiscommonsense]

Thanks to you Gentlemen, now I am relieved! I don't spend much time on teaching my students the troublesome and now I know mostly unreliable calculations of natural gas hydrates formation temperature. Just a few problems to solve in a tutorial and that is it plus calculating the inhibitor dosing rates. I tell my students each oil and gas company should have their commulative expertise in handling this topic, just be aware how they are formed, when they are formed, methods to keep them from forming, you won't be quite sure of exact calculations in a classroom.

[marchem]

you may download Prode Properties 1.19 (from prode.com)
it includes a Excel page which draws the hydrate formation curve,
according the manual hydrate phase is calculated according VDW-Plateeuw model while vapor, liquid and solid (water) with CPA Cubic Assocition model.

[MouradHosni]

By the way
The thesis by Sharareh Ameripour is wrong with the part of "Kobayashi units". She shaid temp is in C and pressure is in bars.
But when I programmed Kobayashi's correlation, I figured out that temperature in R and pressure in psia.

[maruthigabbita]

Dear Mr.Ankur,

Can you pl?ease repost the pdf document http://www.jngc.org/...hang/090409.pdf.

link got expired.

 

Thanks.

 

Prasad

[ankur2061]

Prasad,

 

The article is attached.

 

Regards,

Ankur.

Attached Files

•  090409.pdf   924.17KB   544 downloads

[RockDock]

I would not trust Hysys for hydrate predictions. John M Campbell did a good comparison a few years back for water content in a stream. Hysys had about 200% error on average. ProMax had less than 5% error on average. I think ProMax is probably the most common simulator to use for hydrate predictions. I consulted for a job with a client who had serious hydrate formation inside a dew pointing chiller. Hysys predicted there would be no hydrate formation, while ProMax predicted there would be. ProMax calculated an injection rate of DEG much higher than Hysys. Once the process was adjusted to the new flow rates, no more hydrates were being formed. Here is the Campbell article:

 

http://www.jmcampbel...phase-behavior/