12 replies to this topic

[alextor]

Required to calculate the partial pressure of hydrogen sulfide for various oil fractions, at different temperatures.

The concentration of hydrogen sulfide is not large.

I found Henry constants for a variety of liquids, but not for petroleum fractions.

I know about the program Chemical Process Simulation, but the calculation requires manual

[PingPong]

Use

API Technical Data Book

or

GPSA Engineering Data Book

[alextor]

Use

API Technical Data Book

or

GPSA Engineering Data Book

Henry’s Constant only for water. 

[PingPong]

Once again:

 

Use

API Technical Data Book

or

GPSA Engineering Data Book

[MrShorty]

To reinforce PingPong's response, my old copies of the API Technical data book and the GPSA engineering data books (1980 and 1966, I think they are) both have procedures (as K values=vapor mole fraction/liquid mole fraction) for determining the VLE of H2S in hydrocarbons. Make sure you are looking in the right place for the procedures in those data books.

 

If you found Henry's constants for a variety of fluids, you might look at which fluids you have, and see if any of those data will allow you to at least make a guess at the Henry's constant or activity coefficient for H2S in hydrocarbons. My sources suggest that there is at least some well known and commonly referenced data for H2S in decane and pentane that might be useful for such an undertaking.

[breizh]

Hi,

 

In addition to the previous answers :

 

- Let you try with your favorite search engine , key words H2S solubility in oil .

 

https://pubs.acs.org...rnalCode=jceaax

 

- Carl L Yaws and coll . handbooks could be a resource to support your work.

 

Good luck

Breizh

Edited by breizh, 15 February 2019 - 02:06 AM.

[alextor]

To reinforce PingPong's response, my old copies of the API Technical data book and the GPSA engineering data books (1980 and 1966, I think they are) both have procedures (as K values=vapor mole fraction/liquid mole fraction) for determining the VLE of H2S in hydrocarbons. Make sure you are looking in the right place for the procedures in those data books.

 

I wanted to have a simple method for determining the partial pressure of hydrogen sulfide at concentrations of about 10-1000 ppmw.

I found information about VLE of H2S in hydrocarbons in the API and the GPSA (new version).

But I consider making the calculations VLE an unnecessary complication in my case.

So I asked Henry’s Constant.

 

If you found Henry's constants for a variety of fluids, you might look at which fluids you have, and see if any of those data will allow you to at least make a guess at the Henry's constant or activity coefficient for H2S in hydrocarbons. My sources suggest that there is at least some well known and commonly referenced data for H2S in decane and pentane that might be useful for such an undertaking.

 

Search and use of analogs, make a guess, this cannot be called a simple and universal method.

 

 

Hi,

 

In addition to the previous answers :

 

- Let you try with your favorite search engine , key words H2S solubility in oil .

 

https://pubs.acs.org...rnalCode=jceaax

 

- Carl L Yaws and coll . handbooks could be a resource to support your work.

 

Good luck

Breizh

Of course I used Google.

I've already seen "Solubility of Total Reduced Sulfurs.." but there is no information for fractions, only for individual hydrocarbons

Carl L Yaws - Henry's Law Constant for Compound in Water

 

 

I found a correlation in "Three-Phase Reactor Model of Hydrotreating in Pilot Trickle-Bed Reactors" Hans Korsten and Ulrich Hoffmann, May 1996 

 ....solubility of  hydrogen sulfide in mineral-oil fractions to be

a,  = exp(3.3670-0.008470*T). 

solubility is given in (N1 H,)/[(kg  oil)-(MPa)]. 

The Henry coefficient Hi can be obtained from solubility coefficientsi: 

Hi=un/(ai*pL)

where  uN is the molar gas volume at standard  conditions and pL  represents  the density of the liquid under  process  conditions... 

 

But according to calculations, I get an error 1000 times. Probably a question with dimensions

[PingPong]

The beauty of K-values is that they are dimensionless.

 

There is a very simple relation between K and H, which you should know.

Otherwise I suggest you dig up your old college textbook.

[alextor]

The beauty of K-values is that they are dimensionless.

 

There is a very simple relation between K and H, which you should know.

Otherwise I suggest you dig up your old college textbook.

Of course, the formula is simple, but a total vapor pressure is required. And we come back to the necessity of calculating VLE. But I want to avoid it.

[PingPong]

You don't need to do complicated VLE calculations.

 

A value for total absolute pressure P is required but normally that is known.

But even if it is not known you can simply assume a value for P to determine H.

 

For example, using the graph in GPSA EDB, the K-value for H₂S in hydrocarbons is:

K = 32  at P =   1 bar & 38 ^oC

K = 3.2 at P = 10 bar & 38 ^oC

 

So at 1 bar Henry constant H = 32 * 1 = 32 bar at 38 ^oC

and at 10 bar Henry constant H = 3.2 * 10 = 32 bar at 38 ^oC

 

It makes no difference what P is because K is inversely proportional to P as long as P is not too high (see graph).

In other words: only at very high pressures H is dependent on P.

[alextor]

Thank! The idea is clear!

As I understand this method for the ideal solution.

 

The pressure in the system is often not known, and when it is known it is not correctly used in calculations, for example, a nitrogen pressure vessel.

[PingPong]

Try also API method.

 

Pressure in vessel is usually known, or at least approximately.

Whether the gas above the liquid in the vessel is nitrogen, or HC gas, or liquid vapor, is irrelevant for this calculation.

 

It is not clear what you mean, or want.

[alextor]

"Pressure in vessel" at low concentrations of hydrogen sulfide does not affect the partial pressure of hydrogen sulfide. Therefore, "pressure in vessel" is not required and not necessary for a universal method of calculation.

 

For example, the partial pressure of hydrogen sulfide will not change if the nitrogen pressure in the tank doubles (0 barg-> 1 barg)

 

I think the proposed method is applicable for gas free liquid systems. And it's easier than for NACE MR0175

a ) Determine the bubble-point pressure

b ) Determine the mole fraction of H2S in the gas phase at bubble-point conditions by any suitable method. .

c )  Calculate the partial pressure of H2S in the gas 

Edited by alextor, 25 February 2019 - 01:01 AM.