Gas Sweetening Plant Design 1

[meanderson3d]

I am looking for help designing a gas sweetening plant. We're just in the conceptual stage right now. The flow rate is about 15 MMSCFD of gas with 20 ppm H2S and 4% CO2. I'm familiar with amine units from a process flow standpoint having worked at a gas plant that had one specifically for CO2 removal. What I don't have much experience with is sizing the various components, material selection, and what the heck to do with the acid gas. Any feedback or direction to resources would be greatly appreciated.

 

[maddocks]

This is a pretty big question.

Step 1 - Review GPSA data book with respect to gas sweetening. Get a copy of LRGCC papers from University of Oklahoma. Check out the classic Gas Purification book. Do some preliminary sizing with the help of a process simulator and an engineering consultant.

Step 2 - Review regulatory requirements for potentially flaring and/or incinerating your acid gas. You'd be wise to check out Acid gas injection as an alternate to environmental dispersion.

Your best bet would be to hire an engineering consultant to help you with this. I know that sounds self-serving, but there's a lot of tech info and experience necessary.

 

[SJones]

For materials selection, here are some pointers:

API 571
API 945
EFC 46 Corrosion In Refinery Amine Units

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[SJones]

I missed this one off

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[EmmanuelTop]

Solvent selection (amine, hybrid solvent or physical solvent) is the first thing you should evaluate during concept stage. Since acid gas content is quite high, physical solvents (Selexol, for example) can be quite advantageous if sour gas source pressure is above 50-60bar. You need to prepare comparative analysis of each design concept, and determine optimal operating conditions of a gas plant.

Regarding material selection - you'll need at least some kind of cladding for amine and hybrid solvent system. Usually Alloy 825 or 625 are employed. Physical solvents are non-aqueous and NACE carbon steel can be used.

There are many things to look at: CAPEX/OPEX, availability, plant complexit, acid gas routing (sulfur recovery or injection), potential from NGL recovery from sales gas etc. Each of abovementioned process configurations has its own advantages and trade-offs. There is no "one size fits all" type of plant or technology.

Equipment sizing should not be a serious problem - at least in the concept stage where you can afford +/-30% error. Get a budgetary quotations from various vendors (UOP, BASF, ExxonMobil, Shell etc.) and you'll be able to perform preliminary screening. Focus on:

- Operating pressuere
- Severity of acid gas removal (ppm in sales gas)
- Potential for NGL recovery
- Plant complexity

It's very interesting job to work on. You'll enjoy all the way to the concept final report.

Good luck,

 

[dcasto]

get with your enviro people or hire one. The amout of SO2 is small, but the global warming rules will be attacking SO2 first. Look at a iron sponge or sulfatreat treat to get the H2S out of the vent.

Koch glitch has a free program to size your towers. You need to do you mass balance so you can bypass or slip CO2 to the pipeline specifications. Hint, slip CO2.

You'll be able to find a unit with an off the shelf design on this one. Nothing magic, no need for a lot of exotics.

 

[triniengineer]

I agree with maddocks. Are you developing a FEED (Front End Engineering Design) Package or doing the detailed design as well?
All responses above are useful in doing FEED/ Conceptual Study but please consider using an Engineering firm for detailed design.Your company can look at doing the Procurement and Construction and outsoucing the Deatiled Engineering if they want to cut cost.
I worked in a facility where a 20% Expansion was done in house and the operating plant never recovered to its full potential after the job were done and there were a set of "debottlnecking issues" that were overlooked.
Thanks.

 

[Chacuncha]

There is a recent patent filed on removing H2S from gas on a solid adsorbent-chemical scavenger, The scavenger removes H2S also by direct injection, as far as I have read.