Horizontal Direct Fired Heater Minimum Stack Height Requirements

[Ahmed Elarbagi]

Hello everyone,

I was trying to find if there is a specification or standard that specifies the minimum stack height above the building for a direct fired heater.

The most I found was 2 things:

1- CSA specifying that the minimum requirement is 1.2 * building peak height. However, this is for compressors. Heaters wouldn't be producing as much NOx as compressors, so I'm not sure if the is a different specification for fired heaters.

2- API 560 (Fired Heaters) section 9.2.1.2 specifies that " The minimum height above grade level and the exit gas velocity will be specified by the purchaser.".

Anyone has additional information as to if there is a different requirement for fired heaters than for compressors?

Thank you

 

[georgeverghese]

Fired heater Stack height is usually derived by simulation of the following cases:
a)If the fuel contains sulphur, then H2S and SO2 concentrations at ground level and at any elevated access platforms should meet max permissible exposure limits. NOx concentrations may also be a concern if applicable - check. "Low" NOx burners often dont deliver on expectations. Exposure limits for these pollutants with HSE implications can be found in OSHA, NIOSH, and/or other national agencies.
b)Thermal plume dispersion to keep temperatures at any elevated access platforms and/or nearby buildings within acceptable limits
c)In the event of accidental flame failure at the burners, combustible gas concentration at any nearby access platforms and/or buildings should not be greater than 25% LEL for the worst normal operating windspeed.

These Gaussian ( low stack exit velocity )atmospheric dispersion simulations are run on simulators such as PHAST by process safety / technical safety engineers. A report must be produced detailing these results and conclusions and signed off by a senior authority competent in this subject (Subject Matter Expert - SME)

 

[BEMPE16524]

Fired heaters, while producing fewer NOx emissions than compressors, can still contribute to air pollution. Therefore, local environmental regulations (often set by government or municipal authorities) may dictate stack height to ensure proper dispersion of pollutants. These regulations are often derived from air quality standards (e.g., U.S. EPA or local equivalents) and may require air dispersion modeling to determine the necessary height for effective pollutant dilution.

R.Efendy

 

[shvet]

@Ahmed Elarbagi
avoid doubleposting

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