13 replies to this topic

[Propacket]

Hi everyone!
I’m a newly appointed process engineer in a consultant company. I am simulating a TEG dehydration column using hysys. Gas flow is 30 MMSCFD. Temperature is 133F and pressure is 1264 psia. The inlet gas water content is 28.53 lb/MMSCF. I want to reduce it to 7 lb/MMSCF. I’m using TEG of 99% purity, flow rate of 1.65 USGPM. With these inputs and using 5 trays, water content is reduced to o.ooooo1 mole fraction which is very low. Can anyone tell me how to get the specified water content in hysys?

[NGL Licensor]

Hi,

What is Hysys version

What is the Theromo EOS used in the simulation

If you need fast reply, please e-mail (ngltechnology@yahoo.com)me the case and the feed composition

Regards,
H.Mostafa

[Propacket]

Hi,
I am using TEG circulation of 3.5 US gallons/lb H20. Reducing the flowrate of TEG is not working. TEG EOS is not available in my hysys version. Is there any method to specify water fraction in "Add Specifcations"? I have tried it but system becomes over specified.

[NGL Licensor]

Salam,

3.5 USG/LB water seems to be on the high side.

I have tried to re-model the TEG absorber and found that stream “Inlet gas” components mole fractions add to 0.8083 and not to 1.0.

If you use this composition you end-up with two phase inlet to the column which may worse the absorption calculation

Please revisit the feed composition and send me the right one


A.King

[Propacket]

Salam,
I have revised the composition and used low TEG flow. But the problem remains there. I think Peng Robinson EOS seems not applicable here.That is why TEG EOS is used in new hysys versions. Attached is the exact composition on dry basis and the gas is saturated at the given conditions.

Thanks

Attached Files

•  Composition.pdf   33.55KB   87 downloads

[Art Montemayor]

A. King:

I do not agree with your comment that "3.5 USG/LB water seems to be on the high side". Major international oil and gas companies (as well as myself) regard 3.5 as the LOWER limit for design, not the higher.

Normally, TEG systems are designed based on the glycol circulation rates of between 3 and 5 US gallons per lb of water to be absorbed. However, the actual flow used should always be calculated using a detailed simulation of the packed contactor section (in the case of a packed absorber tower) to ensure that there is adequate wetting of the packing, that the packing is not flooded, and that there are sufficient packing stages for the required duty expected of the contactor. The turndown ratio must also always be considered in the above analysis.

[NGL Licensor]

Art Montemayor,

Each case has its own specifics. The feed gas temperature and hence water content will be a major factor in determining the specific TEG rate.

In our case the temperature is low at 80 F and hence the feed gas water content. One will expect a lower 3.5 ratio

A.King

[joerd]

I agree with Art. The TEG flow rate seems fine, maybe even on the low side. You should be using only 2 or 3 theoretical stages, though - in most TEG units you will not get much more than that.

[NGL Licensor]

Salam,
I have revised the composition and used low TEG flow. But the problem remains there. I think Peng Robinson EOS seems not applicable here.That is why TEG EOS is used in new hysys versions. Attached is the exact composition on dry basis and the gas is saturated at the given conditions.

Thanks

Salam,

Please re-send the attachement with the new composition

A.King

[Propacket]

Hi NGL Licensor,
Please find the attached composition.

Attached Files

•  Composition.pdf   33.55KB   39 downloads

[NGL Licensor]

Hi NGL Licensor,
Please find the attached composition.

Salam,

I have used the revised composition and was able to simulate the TEG absorber. Brief main results are:

1.The 30 MMSCFD feed gas at 133 F and 1264 psia saturated with water

2.Amount of water in feed gas is 153.5 lb/hr

3.Amount of water in dry gas is 8.0 lb/hr

4.Amount of water removed is 145.4 Lb/Hr

5.For a 4 theo trays absorber you shall get close to 7 Lb/MMSCF spec when a 4 USGPM 99.5 wt% TEG is used

6.TEG circulation is below 2 Gallons/Lb water removed

Please feel free for any clarifications

Regards,
A.King

[Propacket]

Thanks,
I'll try to simulate the column to match your results.

[Padmakar Katre]

Salam,
I have revised the composition and used low TEG flow. But the problem remains there. I think Peng Robinson EOS seems not applicable here.That is why TEG EOS is used in new hysys versions. Attached is the exact composition on dry basis and the gas is saturated at the given conditions.

Thanks

Dear,
You can use Glycol package in hysys for modeling your system. You can visit below website where good articles are available (free to download). www.bre.com Bryan Research and Engineering Inc. Technical Articles Section.

[star@25]

The glycol circulation rate considered is not that much big. It is in the acceptable limit. In worst case we use 3 to 3.5 US gallons/lb of water. Then one more thing is the required water outlet spec is 7lb/MMSCF. But u achieved 0.000001 mole fraction of water which is very lower that the required. Hence your design is not bad. In the distillation unit use 2 or 3 no of stage. Using the same TEG flowrate, automatically ur outlet water content will increase.