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Calculating Physical Properties Of Mixture Of Crude + Water


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#1 tanveer.singh

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Posted 20 October 2014 - 05:20 AM

Hi everybody,

 

I am a mechanical engineering performing a process design. I am a novice in this and need your help.

 

Problem: I have a incoming stream containing crude oil + water. I know only the following for both the fluids separately:

a) Mass flow rate

B) Incoming temperature and pressure

c) Density 

d) Dynamic Viscosity

e) Specific Heat

 

Requirement: To know the Density, Dynamic Viscosity and Specific Heat of the mixture. Aim is to calculate the pressure drop when this fluid is flowing in a pipe with numerous bends.

 

How i tried to solve the problem:

1. For density and Specific Heat I believe the value for the mixture shall be the mass weighted average of the individual fluid values. Please correct me if I am wrong.

2. For Viscosity I searched the internet and found 2-3 references to the following:

 

a) There is a mentod of calculating the 'Kinematic' viscosity of a mixture using viscosity blending number method. Please see: https://neutrium.net...ty-of-mixtures/

 

For this method, first I converted the available dynamic viscosity values to kinematic viscosity for both the fluids. Then I used the above formula to calculate the kenimetic viscosity of the mixture. Then I reconverted this to the dynamic viscosity of the mixture by multiplying the vaue with the average density. This seems to be too convoluted. Am I doing it correctly?

 

B) Perry mentions that the dynamic vicosity (nu) of liquid mixtures can be calculated using:

ln numix = sum(i=1 to C) [xi * ln nui] + 0.5 * sum(i = 1 to C)[sum (j=1 to C) [xi * xj * Gij] ]

 

However, to use this method, I need the value of the constant G for each fluid which I have not been able to find.

 

Further, I tried to use two opensource process simulation software. COCO and DWSIM. These would easily provide me the physical properties of the mixture of the fluids. However, here I am faced with another problem - Crude oil is not a pure compound, and I dont know the exact constituents of this particular crude. All I know is the physical properties data mentioned above. How to model the crude in such a case in process simulation applications? Can I create a new compound with only the physical properties I know (only for the purpose of calculating the final mixture properties)?

 

Please help.



#2 P.K.Rao

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Posted 25 October 2014 - 04:11 AM

For density and specific heat, you are in a right direction.

For viscosity blending, please use SMS CT53-93



#3 srfish

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Posted 25 October 2014 - 12:20 PM

Except for the specific heat, the emulsion physical properties I have used  depend on the volume fraction of each component. You also have to determine which is the continuous phase and which is the dispersed phase.

 

One publication on emulsions is " Rheology of Crude oil Dispersions" , SPE Conference (1969) Paper No. 5299. There is also " Find Emulsion Viscosity Through Use of Nomograph", Hydrocarbon Processing, 1969.



#4 DanW

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Posted 05 November 2014 - 10:13 AM

With DWSIM you can use the Petroleum C7+ Fraction Characterization Utility and generate the pseudocompounds needed to calculate mixture properties. I must warn you that DWSIM calculates liquid viscosity using a mixing rule that doesn't take into account the formation of emulsion, which may cause you some trouble, depending on the amount of water.

 

Let me know if you need more help configuring your simulation in DWSIM.

 

Regards






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