2 replies to this topic

[Zauberberg]

G'day everyone

I have got a task to evaluate suitability of an existing TEG Glycol Dehydration Unit for another service/location. The basic design information for the existing unit is as shown below:

TEG purity: 99.75% weight
Max Circulation rate: 4.87 m3/h
Packing type: Sulzer Mellapak 250Y
Packing height: 5,040 mm
Max Capacity of Contactor: 9,360 actual m3/h
Max Reboiler duty: 450 kW

Now, there are two possible locations/services for this unit and the inlet gas conditions are as follows:

Location 1

Flow: 5,450 actual m3/h
Operating pressure: 13 barg
Inlet gas dew point: 20 degC
Outlet gas dew point spec: -32 degC
Inlet gas water content: 1,350 mg/Sm3
Outlet gas water content: 40 mg/Sm3
Available TEG/H2O rate: > 40 kg TEG / kg water absorbed

Location 2

Flow: 5,570 actual m3/h
Operating pressure: 35 barg
Inlet gas dew point: 35 degC
Outlet gas dew point spec: -18 degC
Inlet gas water content: 1,350 mg/Sm3
Outlet gas water content: 40 mg/Sm3
Available TEG/H2O rate: 20 kg TEG / kg water absorbed

I have been using GPSA Databook and Shell DEP in order to evaluate suitability of this unit for the two locations/services, and it appears that everything is OK.

Do you have any hints, or suggestions what sort of further checks I need to make?
Apart from Contactor/Regenerator, all other equipment items are 100% verified as suitable.

[mav9rick]

I would suggest the following:
1) What temperature are you planning to operate the reboiler at? TEG decomposes at around 204 oC.
2) Have you evaluated the need for stripping gas injection to increase the purity? Hydrualics of the the regenerator column may need to be asessed if your stripping gas requirement varies from the oroginal column spec.
3) What approach temperature are you assuming for the contactor? Normally a contactor has no more than 2-3 stages
4) TEG contactor should be designed keeping in mind the hydrate formation trenperature and not just the sales gas spec. 40 mg/sm3 seems to be a typical sales gas spec. You may want to consider lower water content in the exit gas so as to avert the hydrate formation

cheers

[vnpetroleum]

G' morning,
Some more comment for your reference,
1> How about glycol loss of existing TEG Unit? Is it within acceptable margin?
2> Reboiler Performance: stripping gas assumption, reboiler temperature? Is it operating at 204 degC? Check internal vessel - fouling?
3> Reflux Condenser: operating temp @ 105 degC? Check the integrity of Coil? Any leak found? Some sites experienced coil leak at the top of regenerator.
4> What is TEG Regeneration Model? DRIZO? Please check the required solvent, this will help to minimize stripping gas use.
5> Glycol/Glycol Heat Exchanger Performance: check the mean temperature, fouling?
6> pH, antifoam control? Is there pH, antifoam control available for control pH, foaming?
7> Glycol pumps efficiency?
8> Glycol/Gas Heat Exchanger? Glycol temperature should be 5 - 8 deg C higher than gas outlet

Edited by vnpetroleum, 16 October 2011 - 11:13 PM.