Natural draft versus forced draft fire heaters

[Sawsan311]

Dear All,

I would like to confirm that although forced draft fire heaters ar emore efficient and require less fuel gas compared to natural draft heaters, yet they may have higher CAPEX due to the taller required stack draft due to the less buoyancy and draft capabilities??
Appreciate your views

regards,

 

[crshears]

I for one would confirm that; to my understanding, use of pure natural draft in commercial / industrial applications has been out of favour for decades, precisely for the reasons you state.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[LittleInch]

If they are more efficient they should be smaller hence lower CAPEX?

Natural draft heaters are very basic and hence can be lower CAPEX, but I don't believe there is a "confirmation" without getting prices from vendors and then allowing some element of OPEX costs.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Sawsan311]

Thanks alot

I was mainly comparing with respect to the stack height where flue gases are being disposed up safely to the atmosphere, I think forced draft have taller stacks due to less bouyancy. Do you agree?

 

[crshears]

Sorry; mis-read OP, so I was wrong...please disregard my previous post.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[LittleInch]

I honestly don't know, but can't quite see the link between forced, natural and stack height. As it's forced draft the stack can be any size - just affects the size of the fan surely.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[georgeverghese]

From a process safety perspective, natural draft fired heaters are not acceptable if located in a electrical hazardous area classification Zone 2. For zone 2 locations, a forced draught fired heater's air intake should be from an unclassified ( safe) area.

 

[Mohammad Ka]

Draft is calculated using the following formula
D = 0.52 H × P(1/T - 1/T1)            
in which
D = draft produced (inches of water)
H = height of stack (ft)
P = atmospheric pressure (psia)
T = absolute atmospheric temperature
T1 = absolute temperature of stack gases.

The height of stack is a direct function of draft. In induced draft furnace because of ID fan, lower draft and hence the lower height of stack is required. It seems CAPEX of ID furnace is lower than natural furnace although the OPEX is higher in the forced draft furnace.