C5+ Recovery from Injection Gas

[EmmanuelTop]

Hello to everyone,

I'm looking for applicable technologies/vendors for condensate recovery from injection gas - technologies based on solid bed adsorption and membrane systems.

Injection gas is very lean (about 3.5% weight of C5+), so mechanical refrigeration and turbo-expander plant are not attractive - which make adsorption and membranes to be favorite options. In addition, acid gas content is quite high (3.5% weight H2S and 27% weight CO2, saturated with water). Only C5+ fraction is of interest for recovery. Injection gas pressure is 100bar, and the temperature is 50C. Net flowrate is about 4,000,000 Sm3/day.

I have some information about Shell/Engelhard's SORDECO adsorption process, but I would like to include other technologies as well, in order to find the best solution.

Any feedback from forum members is appreciated.
Best regards,

 

[dcasto]

silca gel or sorb beads. Refrigeration is also good, its not that expensive and easy to maintain.

 

[maddocks]

dcasto is right - refrigeration is relatively cheap. However, you will be recovering H2S at the same time due to the phase equilibria. You'll also require glycol injection for water hydrate controls. You can talk to Engelhard or Sorbead but you'll likely have a sour product. Might need to consider acid gas removal upstream.

 

[EmmanuelTop]

maddocks/dcasto,

Thank you for your replies. I have already contacted Shell/Engelhard (SORDECO) and Grace Catalysts (SYLOBEAD).

The main issue related to solid-bed adsorption units - as I see it - is their applicability for highly sour gases. From what I have seen in the literature, adsorbents are used for hydrocarbon dew-point at remote locations and for esentially sweet natural gas, which is not the case here.

Due to relatively low content of C5+, refrigeration unit and turbo-expander do not look attractive: according to process modeling results recovery of C5+ in these units can go only up to ~55%, which is not enough for economical justification. On the other hand, adsorption can be quite efficient but I know this is true only for sweet gases. In any case, I do not care much if CO2/H2S are going to be co-adsorbed, because liquid product will be recycled back to the condensate train for fractionation.

Do you have experience with condensate recovery units from such highly sour gases?

Thanks again,

 

[maddocks]

Shouldn't really be a problem - typical phase behavour should apply. Use PR for modelling and you'll be fine. You'll want to examine specifications on the condensate product to see if you require a TVP spec or an RVP spec. Other than that, I can't see any issues. Of course, like any sour system, metallurgy requires consideration.

 

[dcasto]

I worked at similar facility in the 80's 7 mole% H2S, 25% CO2, huge amounts of condensate., reinject all the gas for resivior maintenance on retrograde condensate. We treated the liquids with molesieves (we made spec C3, mixed butanes, and the rest went in the oil) This site was way out in nowhere too at 7000' and in Wyoming.

The plant selected was refrigerated lean oil to maximize C3, no ethane recovery.
The sour gas made everything NACE.

I dissassembled a adsortion plant on sour gas one time. Man was it ever corroded out. Between the water coadsortion and the regeneration loop temperatures of 500F, bad news.

 

[EmmanuelTop]

Dcasto,

Which type of oil can be used for absorption tower? This technology can be interesting as well since there's no interest for recovering propane and butanes from injection gas.

I believe I cannot use stabilized condensate as lean oil because it has high TBP end-point (above 500C); I've never heard anyone had used such heavy fluid for absorption purposes.

This system is very similar to yours - high pressure retrograde condensate reservoir, with Injection gas pressure above 350barg.