Roaster Exhaust

[Axel]

Trying to figure out the optimal way of powering the exhaust out of a roaster with a 22"x30" Drum and 140,000 BTUs.
Cost of parts is a factor.

I might be able to get a great deal on a new 2hp single phase motor with a 5/8" shaft.
with that I can probably easily power both the drum rotation and an exhaust blower.

the question in this scenario would be about suction control.
how effective(practical) would something like a heavy duty(large diameter 16g pipe) incarnation of a vacuum cleaner hose suction control be?
basically making a sliding door that adds outside air into the negative air end of the exhaust pipe.
Closing the door gives full suction, opening it decreases the suction.

or is having two separate motors with a speed control on the blower motor a much better idea?

 

[sae]

having separate motors is better. As far as adding outside air goes - the Diedrich's do something like this but you might be better off just using a blast gate to close off the air so that there is less suction.

 

[Axel]

I guess adding outside air before the blower is a much more primitive way(compared to electronic controls) of adjusting exhaust suction but it seems to have been used on large older machines?
and it's one less motor to buy/maintain/replace

 

[Axel]

planning for the burner to have approximately 140,000BTU's(to much,too little?)

I've viewed a lot of blowers on eBay but the ones that are "high temperature rated" have 450°F as the maximum.
should the blower be built to withstand a chimney fire(1,400°F)?
Thinking that 300-400 CFM should be good.

Planning to use 18gauge welded pipe ~6"diameter to run the exhaust to the chaff collection.
probably regular wood stove pipe(maybe 8") for the vertical.

any suggestions?