4 replies to this topic

[Matteo Giorgio Marrano]

Hi, i've tried to find a conversion factor in order to convert PTB of salt (Pounds per thousand Barrels) to ppm (mg/l), does the following is correct?

1 PTB: 1 lb/1000 barrels

1 barrel: 158.9 liters
1 lb: 0.454 kg

1 PTB: 0.454 kg/1000*158.9l so, 1 PTB=2.855 mg/l


i think there is something wrong, i don't now..

In example, how many ppm are 40 PTB?

Thanks in advance

[breizh]

Hi ,
PPM = part per million or mg/kg
regards
Breizh

[Art Montemayor]

Matteo:

breizh is correct in pointing out that the term "ppm" in english means "parts per million" - not relative density (mg/liter). What he forgot to state is that the ppms can be in terms of volume or mass - and it should always be specified as to which one you mean. Ppm is used to indicate very small concentrations - usually impurities - in a compound or a fluid.

Your calculations are correct for converting Pounds per thousand Barrels to milligrams per liter. The way I do it is the same as you:

(40 lbs/1000 barrels) (barrel/158.987 liters) (453.592 mg/pound) =114.1205 mg/liter

I always use my FREE Uconeer engineering conversion program to obtain all the correct conversions. You can download a free program also at Katmar's Website. It's the best conversion program ever put together for engineers.

[Matteo Giorgio Marrano]

Matteo:
breizh is correct in pointing out that the term "ppm" in english means "parts per million" - not relative density (mg/liter). What he forgot to state is that the ppms can be in terms of volume or mass - and it should always be specified as to which one you mean. Ppm is used to indicate very small concentrations - usually impurities - in a compound or a fluid.
Your calculations are correct for converting Pounds per thousand Barrels to milligrams per liter. The way I do it is the same as you:
(40 lbs/1000 barrels) (barrel/158.987 liters) (453.592 mg/pound) =114.1205 mg/liter
I always use my FREE Uconeer engineering conversion program to obtain all the correct conversions. You can download a free program also at Katmar's Website. It's the best conversion program ever put together for engineers.

Hi ART,
i was trying to understand more in desalting mass balances and i was "exercising" myself on the argument basing on a desaltere package i'm working on (i have the mass balance made by the desalter's supplier and i'm working on it).

i was working on salt concentration in water, so for water ppm=mg/l (considering the density=1, right?).
I founded also some useful formulas from a book called: "petroleum and gas field processing" by Abdel Aal and Mohammed Aggour (iranian/iraq people) in order to calculate the PTB of salt depending on the ppm concentration on the wet oil..

Anyway ,the fact that my calculation were ok gives me help .

Art, do you have any suggestion about making a mass balance for a "two stage desalting unit"?
Does companies made it with some programs like hysys and co. or i can make it on my own with a pen and a sheet of paper? (of course, an exstimating material balance)...

thanks (also for the tips of the convertion program)

Matteo

[djack77494]

do you have any suggestion about making a mass balance for a "two stage desalting unit"?
Does companies made it with some programs like hysys and co. or i can make it on my own with a pen and a sheet of paper?

Matteo,
The hard part of doing your mass balance around a two stage Desalter is figuring out your separation efficiency. Simulators may know about equilibrium conditions, but they are not able to address this problem, so you needn't start up Hysys. In a Desalter, you add water to your oil, allow the two to mix, and then separate the oil and water. Since salt has a greater affinity for water than oil, your hope is that the salt is able get out of the oil and into the water phase. Its ability to do so depends on the efficiency of the mixing and subsequent phase separation steps. I believe that you MUST rely on vendor information to obtain estimates of how effective your Desalter process will be. If you wish to disagree, then please be prepared to tell me how the salt content of the oil will change if you vary the applied voltage. That information is just not readily available.