10 replies to this topic

[jatinder]

Dear All,

 

I have a question regarding Glycol reboiler and the heating source is considered as Steam. I have calculated the required steam consumption to maintain the glycol temperature in reboiler at 204 deg. C. Please find attached excel file. Could you please verify the calculations and inform me if I am on right track.

 

Steam data -

 

Steam pressure = 23.01 bar

Saturated Steam Temp. = 219 59 deg. C

Heat of vaporization @23.01 bar = 1859.2 KJ/Kg

 

Glycol mass flow rate = 2000 kg/hr = 0.56 kg/s

 

Specific heat capactiy of glycol = 3.12 kJ/kg°C - (It is considered as an assumption for the sake of calcuations)

 

Temp. of glycol before entering the Reboiler = 160 °C (Assumption)

Temp of glycol in reboiler = 204 °C

 

According to my calcuations:

 

My heat load = 76.27 KW

Required Steam Load = 147.67 Kg/Hr

 

 

Please find the calcuations in the attached excel sheet. Could you please check if I have calculated it correctly?

 

Thank you very much,

 

Regards

 

Mander

 

Attached Files

•  Steam Consumption.xlsx   11.17KB   55 downloads

[oscarsender]

Considering no heat losses, calculation is good for me. I just did the same manual calculation recently in my job.

[jatinder]

@ Oscarsender - Thanks a lot! Yes I did not consider heat loss. I just wanted to check if I am on the right path. I will try to dig further into heat loss consideration. 

[Bobby Strain]

Jatinder,

   You probaly asked the wrong question. Therefore you got the wrong answer.

 

Bobby

[Art Montemayor]

Why did you select steam as the heat medium for your TEG reboiler tube bundle?

[jatinder]

Why did you select steam as the heat medium for your TEG reboiler tube bundle?

Dear Art,

 

Currently I am learning about glycol dehydration system. I am trying to gather and learn everything related to this topic. For example, first I spend few days learning more about water content in the inlet feed gas composition, water dew point, dew point depression etc. Now I have moved to Regeneration part. Regarding the re-boiler, many different literature sources says that electricity, hot-oil and steam can be used as an energy source. 

 

Of course reboiler electric bundle is the least complex but what if the only available option is Steam? So for the sake of understanding calculations, I picked up steam in this case. 

 

I hope to inform you sufficient. Please let me know if you have more questions. 

 

It would be great if you can provide any information regarding it. 

 

Thanks,

 

Regards

 

Jatinder 

[jatinder]

Jatinder,

   You probaly asked the wrong question. Therefore you got the wrong answer.

 

Bobby

Dear Bobby,

 

Would you please be so kind to correct me ? What makes you come to the conclusion that I have asked wrong question?

 

Thanks a lot,

 

Kind Regards

 

Jatinder 

[Art Montemayor]

Jatinder:

 

I asked the question because of curiosity.   I've started up and operated TEG units and now I consult on them.  The TEG reboilers I've been involved with were all direct-fired or hot oil applications.  I've seen two electric models, but relatively small.  I've never seen a steam-heated TEG reboiler.  The subject has come up in the past and some in-experienced authors have mentioned the use of steam.  However, the ability to justify a 350 psig+ saturated steam supply has not been feasible in my experience.  Additionally, the majority of TEG dehydration is done out in the field where steam supply is not an option.  That's where direct-fired units are popular.  I would stay away from electric resistance heaters because of the possibility of having excessive hot spots within the elements due to fouling or bad circulation in the reboiler.  At 400 ^oF you are already on the border of decomposing the TEG.  The last big unit I consulted on was hot oil with the heating source coming from gas turbine exhaust.   That would be my preference for process control and TEG protection.

 

You should go back and study your Unit Operation around the TEG Stripper-Reboiler.  When you do, you will find that just about all designs incorporate a "reflux" condenser at the top of the stripper.  Although the unit operation in reality is a pure stripper, a portion of the water vapor leaving the reboiler is condensed and returned to act a water wash to reduce TEG losses out of the stripper top section.  Because of this, you will have a water vaporization load in the TEG reboiler.   If you made a heat and material balance around the stripper + reboiler, you would be aware of this.  Therefore, your calculated reboiler heat load is deficient by the amount of water vaporized in the reboiler.   Losses are something else; they are not a load.

[jatinder]

Art,

 

Thanks for the explanation. It is useful. 

 

Jatinder

[breizh]

http://oilgasprocess...com/tegdehy.htm

 

jatinder,

Consider this link , it might offer some information . As suggested take time to read what Art already published on this topic.

Good luck

Breizh

[Padmakar Katre]

Hello Jatinder,

Hope you take comments by forum members positively. Mr Art has explained in a detailed way as usual with proper reasons for not using steam. There are two take away points from here,

1. You know enthalpy balance for reboiler system and

2. Reboiler systems in glycol dehydration.

 

Additional thing you have to do it estimate additional heat required for water vaporization to meet the spec.