condensation of wood fire flue gas?

[NCCaryME]

I have an application where an existing abort stack on a wood-fired combustion unit is to be replaced by a new, taller stack. In order for the new stack to be free-standing and the correct height, the base must be much larger than the top section (60" base versus 30" top). The larger diameter bottom will slow the gas velocity to under 1000 fpm. Should I be concerned about condensation of the gas, and possibly corrosives in the condensation? My alternative is a double-walled stack, but I'd like to keep the cost down if at all possible.

 

[rmw]

Some basic information like what temperature the flue gas is entering the base of the stack would be helpful.

rmw

 

[NCCaryME]

The estimated flue gas temperature is 550F entering the stack, estimated flow is 15,000 ACFM.

 

[25362]

A bare steel stack would indeed show a temperature drop almost twice as large than that for gunited steel (gunite lining 2-in. thick) and about four times the drop for concrete. It might become prohibitively large if one takes into account, for example, rainfall.

Other factors to be considered are draft and the exit gas velocity at the top to help in combating air pollution.