MDEA reboiler Maximum Steam temperature 5

[reena1957]

We are in the process of designing a MDEA regeneration reboiler. What is the max heat flux and what is the allowable Delta T? Can MP steam (about 180 Deg C) be used for heating?
Thanks in advance!!
Note.This was inadvertantly posted first in Chemical environmental Control forum first. Pl reply here. Thanks

 

[Longinthetooth]

We use LP steam 320 kpag in our 50% MDEA reboilers. Dont know about maximum heat flux.

 

[srfish]

I agree with geordie87 about using LP steam. For heat flux, I wouldn't go over a value of 8,000 Btu/hr-ft2.

 

[25362]

I've heard of heat fluxes in the order of 19,000 kcal/(h.m²). It has been said that some thermal decomposition could take place if skin temperatures are higher than 160^oC, but, since ternary amines, as MDEA, are more thermally stable, this has to be confirmed by the knowhow supplier. If the bulk temperature is 122^oC this would mean a [Δ]T ~ 38^oC.

 

[dcasto]

I've operated up to about 10000 kcal/hr direct fired heaters in different amines. The largest MDEA was 2 parallel 4000 kcal/hr heaters. These used circulating pumps to run the amine through the heaters. I've also done 2500 kcal/hr as direct fired with no pumps.

I'd stop at 5000 kcal/hr as a direct fired with a pump system and 2000 kcal/hr as a direct no pump system. These should have no more than 10,000 btu/hr-ft^2 heat flux, 8000 would be very conservative.

 

[maddocks]

I normally use a maximum flux of 8000 Btu/hr-ft2 as well. This is conservative, but it's not unusual for the lean/rich exchangers to slightly underperform. At the same, in Canadian winters, the condenser will tend to overcool and both these conditions will put additional load onto the reboiler.

I used to use hot oil in most of my systems, but am leaning more towards 350 Deg F glycol at the hottest to limit tube wall temps and heat flux.....having said that, the plants with hot oil are still working with no apparent amine degradation...go figure.