12 replies to this topic

[Dmitry]

Hello Dear members,

 

I am Process Engineer, working on Gas Processing Plant in Ukraine. Since from 1 st of January 2016 we have new requirement regarding Natural Gas quality exporting to the trunk pipelines I would like to share with you my issue and receive advice.

 

The new requirement now limits H2S  mass comcentration (4 ppmv) and CO2 mole fraction  (not higher than 2 %)

 

Note that before we never had such requirement, only Dew point and Heating Value

 

Our inlet gas contain 5,385 % mole fraction of CO2 and H2S is 6 ppmv.

 

As you can see  the real problem is only with CO2, and H2S is just little bit above specification.

 

Below is inlet Gas composition, mole %

 

C1 - 86,974

C2 - 5,616

C3 - 1.,254

C4i  - 0,164

C4n - 0,209

C5neo - 0,008

C5i - 0,069

C6n - 0,046

C6+ - 0,164

O2 - 0,01

N2 - 0,282

CO2 - 5,385

H2S - 5 ppmv 

 

Gas flowrate is 2 000 000 st.m3/day

Pressure in plant 50-55 barg

 

In my experiance in Russia Gas plant we had Amine treatment unit, but we have in inlet Natural Gas about 6,0 % mole of CO2 and 1000 ppmv of H2S. And we used MDEA with 45-48 % mass concentration.

 

MDEA very selective for H2S treatment with bulk removal of CO2. In export gas we have very small amount of H2S (1 ppmv) and 1,5 % mole of CO2. 

 

Now we need to select process for remove CO2 from our gas and just a little H2S. 

 

Note that we also will install Gas dew point unit with Propane refrigeration loop to cool gas till -20 to provide Dew point specification (now we are use J-T Valve but in summer time there are problems with high watre and HC dew point temperatures)

 

My question is what type of process will be most suitible only for CO2 remove - Amine treatment or may be Membrane technology or else.

 

If we use only MDEA it will not react with CO2 as I know and we need to add catalics like DEA as I know

 

Please correct me if I am wrong

 

Looking forward for your reply

 

Regards,

Dmytro

 

[Bobby Strain]

You should look at BASF aMDEA. They require a license fee, but energy savings are substantial. And they will provide basic design information, too.  Also Huntsman. But MDEA in some form is likely your best choice.

 

Bobby

[Dmitry]

Tyt thanks for information. Do you want to tell that this should be activated MDEA? And using just MDEA will. If give result for remove CO2?

And the second question is the general process - Amine treatment is the best solution? What about membrane technology, what they required

Thanks

[RockDock]

MDEA could possibly remove the required amount of CO2 for your plant. You need to remove roughly 50% of the CO2. I have seen many MDEA units do that. It depends on your residence time for the chemical reaction. You will need a high residence time to achieve this with MDEA.

 

The other option I would suggest is DGA. It will have similar performance to aMDEA, as far as energy consumption is concerned. It will remove pretty much all your CO2.

 

An alternative to an amine process would be Selexol (DEPG) or Methanol. This option would likely have the least operating cost, especially in cold environments.

 

A membrane may be a good option, too. Frames would be a good company to explore that for you.

 

You can easily compare all these options in your ProMax model before going to a vendor so you can narrow down your choices.

[Dmitry]

Thanks,

You mean MDEA and aMDEA is the same or different? I suppose aMDEA is the mixture of MDEA 45% of weight and activator ti fast reactuon with CO2 - 5% of DEA for example. Am I correct?

What another actuators is used?


Could you please share name of companies where I can go for engineering and manufacturing of:

Amine units for CO2 remove
Membrane units for CO2 remove
Another technology for remove CO2

I have only Hysys and do not have Promax

Regards,
Dmytri

[senthil13]

I have used aMDEA from BASF (now INEOS), they work great for Co2 removal. the activator that i know of is piperazine.

 

Also read some literatures that Alstom have technology to use ammonia to remove Co2. Not sure whether it is commercial or just pilot stage.

[RockDock]

Activators would be DEA and piperazine (most common). MDEA would be roughly 50/50 MDEA and water. aMDEA is typically 7% piperazine and 43% MDEA.

 

In the absence of having the proper engineering tools to do an evaluation yourself, you are right that you will need to go directly to an engineering company to do all the work. There would be no point in modeling this in Hysys.

 

 

BASF and Huntsman are options for amine processes only.

 

Dickson is a company I would try. Interstate Treaters is another. Of course, you also have the big companies to consider, such as WorleyParsons, Technip, and Foster Wheeler and others. Any of those should be able to evaluate your options for chemical and physical solvents. Frames would be a good option for membranes. Dickson would be the first call I'd make. They should be able to evaluate all your options.

[Dmitry]

I have used aMDEA from BASF (now INEOS), they work great for Co2 removal. the activator that i know of is piperazine.

Also read some literatures that Alstom have technology to use ammonia to remove Co2. Not sure whether it is commercial or just pilot stage.

We used MDEA with water on previous Gas plant. Is any changes with operating parameters for using aMDEA if compare MDEA. I mean for example regeneration temperature and pressure in stripper

Thanks

[Dmitry]

RockDock:

 

Thanks for the names of Companies. I will contact to them soon.

Before we worked with Huntsman, they supplied MDEA for our Amine plant.They are very good.

Do you can compare Amine and Membrane. methods for CO2 remove?
Only design company can select which method is better? Or client (my company) can select based on some limits?

Thanks

[senthil13]

I dont see any change in operating parameter between MDEA and aMDEA

[RockDock]

No problem.

 

You could certainly do some evaluation on your own comparing chemical solvents, physical solvents, and membranes if you had the right tools. You would likely be able to narrow it down to one process before sending the detailed engineering to an external engineering company. That is not an evaluation anyone would recommend using Hysys. I think your best option would be to send it to en engineering company to complete all the options.

 

You may see some slight differences in reboiler duty between aMDEA and MDEA. Piperazine requires more heat to regenerate which is why you only have a small amount of it. The temperature of the stripper is dependent on the pressure not the duty. The temperature will be the boiling point of water at the given pressure.

 

I've also had great experiences with Huntsman.

[Dmitry]

RockDock:

 

On my Amine plant with MDEA 45-48% by weight pressure in Stripper was 1.6 barg in bottom and 1.3 barg in top. Acid gas goes to SRU with pressure 1,1 barg.
Temperature in bottom was 120-125 deg.C.
On the top we set it at 110 deg.C.

AMDEA + piperizane will have the same parameters?

[RockDock]

aMDEA would be the same for the above process details. However, the reboiler duty would likely be different, as freeing CO2 from MDEA requires less heat of reaction than from piperazine. That means you will likely need more steam generation in order to hit your 110 C set point.