4 replies to this topic

[moein_omg]

Dear experts

 

I encountered with the problem of evaluating the ppm of H2S and CO2 in the liquid phase for selection of proper material for closed drain pump (in an oil production plant). Actually we have to provide the vendor with the mentioned information. Now I have two concerns in my mind:

 

1- As far  as I know, for gases engineers simply multiply the mole fraction in one million; for instance 1 percent of H2S equals to 10000 ppm (is that a normal practice? ). Dissimilarity, for liquids, labs usually report it in mg/lit.

Now my question is: which method shall I adopt to report these values which are obtained from HYSYS simulation? and which way is more routine to report liquid concentration.

 

2- Moreover, in our simulation, we have used pure water, I doubt about the validity of simulation since the produced water is extremely saline and complex equilibrium exists in the aqueous solution. The question is shall I consider all salt components or only pure water is enough to calculate the dissolved concentration of H2S and CO2.

 

 

Thanks for your precious comments in advanced.

 

Regards

[SPC]

Dear Moein,

   

           For your pump, you can calculate & find out PPM as follows:

 

1) Find out total Liquid Volume for your pump - litres

 

2) Find out mg of each gas in your pump stream flow. You can also take help from stream component data given by your licensor/ client Data/ Lab data. If values are in mole, try to calculate mass of component gas in mg.

 

3) Divide total mg of gas / total solution (Liquid) Volume in litre.

 

4) 1 mg/litre = 1 ppm

 

Below is example : here is SATP is standard Ambient temp. & pressure, Kindly go through link:

 

http://www2.ucdsb.on...psolutions.html

 

Example #2   Dissolved O₂ in water shows a concentration of 250 mL of water At SATP and 2.2 mg of O₂.  What is the concentration in ppm?
  ppm concentration = 1 mg   =   2.2 mg   =  8.8 mg/L = 8.8 ppm 
                                   1 L          0.25 L

[RockDock]

ppm can be a mole, mass or volume basis. It is normal practice to multiply it by 10000 once you have it in the correct basis, just as you said.

 

I gather from your description that you have sour water. Because of this, I would not trust the Hysys values. The best option is to take a sample from the plant. If that is not possible (as in a design), your next best option will be to use a ProMax model to predict the sour water composition. It will be much more accurate. Then you can also take into account the salinity of the water. I would absolutely model the salts because they are ionic. Your material selection needs to account for the ions in solution which is the whole reason you need different materials for H2S and CO2. In my experience Hysys does not model this well. I recommend ProMax.

[moein_omg]

Thank alot Dear SPC and RockDock.

what about gas concentaration PPM is "mole frac * 1000000"   routine?

 

Best Wishes

[RockDock]

1 mol% = 10000 ppm (mol)