Removing everything but hydrocarbons from gas stream 3

[danyduclos]

Hi all,

I am beginning work on a new project for hydrocarbon gas recovery.
Basically, my client wants to take a stream of gas containing those hydrocarbons: propane, i-butane, n-butane, i-pentane, n-pentane, propanol, dimethyl-etherher and acetone, all in varying proportions.
This stream will be saturated with moisture and might contain nitrogen and other impurities, the objective is the eliminate everything from it except the HC, anyone has suggestions on how to do this?
Regards,

 

[gr2vessels]

Membrane type of Separators.
Cheers,
gr2vessels

 

[dcasto]

google Advanced extraction technologies. Carbon Coconut shells) based PSA (nitrotech).

 

[danyduclos]

Thanks you very much for your input, i'm contacting manufacturers right now to see how it can be integrated in the process!
If anyone else has suggestions, i'm listening!
Regards,

 

[dcasto]

good luck,

 

[mbeychok]

danyduclos:

Define what you mean by hydrocarbons. I would define propanol, dimethyl-ether and acetone as hydrocarbons. That just leaves nitrogen and "other impurities" to remove. Is that correct?

Or is your definition of hydrocarbons simply the alkanes?

Milton Beychok
(Visit me at www.air-dispersion.com)
.

 

[danyduclos]

Milton,

Yes you are correct, basically i want to remove nitrogen, oxygen if any and other impurities from the gas. what I want to keep are propane, i-butane, n-butane, i-pentane, n-pentane, propanol and acetone. I might also have dimethyl-ether in the gas stream.

Regards,

 

[mbeychok]

.
danyduclos:

If you want to remove the nitrogen and oxygen and retain the hydrocarbons you listed, then it could be done by low-temperature distillation using a turboexpander as is commonly done in a demethanizer to recover natural gas liquids (NGL) from raw natural gas (after removing any water vapor, CO2 and H2S).

Here is a schematic diagram of a demethanizer:

Of course the above design is for demethanizing and would have to be modified to fit your situation.


Milton Beychok
(Visit me at www.air-dispersion.com)
.

 

[dcasto]

your gonna need a whole lot more equipment if you want to get rid of the N2. and temperatures a lot colder.

 

[mbeychok]

Hi, dcasto:

Agreed. Lower temperatures and more equipment will be needed to remove nitrogen (as compared to a natural gas demethanizer) ... but the principle is the same. In other words, low temperature distillation could do the job.

Milton Beychok
(Visit me at www.air-dispersion.com)
.

 

[thegasmasher]

How much oxygen is present?

The order of treatment would be

O2 oxidation - using a catalyst
CO2 removal - amine unit
dehydration - TEG unit or molecular sieve
refrigeration 1 - removes heavier hydrocarbons
refrigeration 2 and distillation - cold enough to condense all but the nitrogen

This has been done in the past.

 

[danyduclos]

What i can do is purge the system with nitrogen before the start of production so there would be nothing but nitrogen and hydrocarbons in the gas.
Is it possible to use sieves to remove the VOC and then to liquefy the hydrocarbon gas by compression at around 100 psig, then all that would still be gas would be nitrogen?

 

[maddocks]

Liquefying at 100 Psig is going to require near-cryo temperatures. You're going to require CO2 removal followed by mole sieve for water extraction. This is starting to sound expensive.

 

[danyduclos]

The gases i have in the mix are basically butane, pentane, propane; those gases don`t need cryo to get liquefied at 100 psi...

 

[dcasto]

at -40F, you could still lose 10% of the propane with the N2.

 

[danyduclos]

Dcasto,

Do you mean that the propane `bonds' with the N2?