3 replies to this topic

[VIrendra20911]

I want to know what should be the stack outlet temperature of a combustion process and how it is decided.

Edited by Art Montemayor, 26 July 2016 - 11:58 AM.
Grammar, composition, spelling, etc., etc.

[breizh]

Hi ,

you need to perform an heat balance to get your temperature . Consider the resource attached to support your work.

 

Good luck

Breizh

[shvet]

It depends on heater type.

 

1 Case - High feed temperature and no cold-end corrosion risk exists.

Flue gas outlet temperature depends on temperature approach, Temperature approach depends on company's investment politicy. The less temp approach is the higher CAPEX and less OPEX are. Usually it lies in 30-150 °C.

 

2 Case - Low feed temperature and cold-end corrion risk

Flue gas outlet temperature depends on sulfur content and is defined according to type of preheater/convection section and its material of construction. Corrosion-resistant materials are extremely expensive. There are a lot of information about min recommended flue gas temperature vs. fuel sulfur content for different types of preheaters, In no case temperature approach should be less than 20 °C (flue gas temp vs. acid dew point temp). Relatively clean gas could be called gas with H2S less than 1000 ppmm.

 

More useful information about cold-end corrosion you can find in Lieberman's "Process Equipment Malfunctions" para, 24.3. Or ask here.

Edited by shvet, 26 July 2016 - 11:41 PM.

[S.AHMAD]

Hi

You need to determine the flue gas dew point which is depending on the composition of SO₃ in the flue gas. Rough estimate that for 20 ppm of SO₃ the dew point is about 130^oC. In absence of data use 150 ^oC  as the minimum limit. This is my own perception. The best is for you to determine the exact dew point and add 20^oC tolerance.

 

s.ahmad