What is the optimal air flow rate in fluid bed roasters?

[John F]

I think gutting one of those cannon heater things might be more on track than a pack of heat guns.

[Tex]

If I was considering building a roaster from scratch I'd probably start with the heater, specifically a purpose-built element, not try to adapt something. http://www.omega.com/heaters/hsc.html



edited: Another thing I'd consider is recirculating the exhaust gases into the air intake (not 100% practical with gas burners). Basically, once you've got the air hot keep using it - the power necessary to reheat exhaust air is much less than bringing room air up to temp.

[J.Jirehs Roaster]

I think gutting one of those cannon heater things might be more on track than a pack of heat guns.

Hmm.. my brother has a civil war cannon...  coffee roasted and delivered in one pop... get that anvil in the mix and it could beground at the same time

[Ascholten]

Tex, the idea of recircing the hot air is not a new one.  Problem is, the equipment to handle that kind of heat, ie the motor and fan blading, can get expensive due to the insulation needed.   If one could mount a motor outside the heat tunnel with some kind of fan inside to run the air round and round it might work, however once the beans start cracking id think you might need to introduce fresh air and vent some of the old air out so you don't get super smoke flavored beans from the roasting smoke.

Aaron

[John F]

The Sonofresco is a ~1 lb roaster and per specification produces 31,000 BTU/hr for the propane version


It is possible to get more BTU from a heat gun but you will need a propane heat gun that boasts 212,000 BTU/hr

but it has a hefty price tag of Only $599.00

This dude pumps out 50K for $99.

No telling what the CFM's are or if they will loft a #.

http://www.lowes.com/lowes/lkn?action=productDetail&productId=154996-88644-RMC-FA50C&lpage=none

[milowebailey]

The Sonofresco is a ~1 lb roaster and per specification produces 31,000 BTU/hr for the propane version


It is possible to get more BTU from a heat gun but you will need a propane heat gun that boasts 212,000 BTU/hr

but it has a hefty price tag of Only $599.00

This dude pumps out 50K for $99.

No telling what the CFM's are or if they will lot a #.

http://www.lowes.com/lowes/lkn?action=productDetail&productId=154996-88644-RMC-FA50C&lpage=none

that would work

[John F]

that would work

I should get one, turn it on the side. stick a charcoal chimney on top of it with a screen in the bottom and just see what it would do.

Who knows...it might do a pound or .75 or 1.25 or .50..who cares, it should probably roast something and the batch size could be adjusted to get in a good window.

If I didn't have too much to do already I would because it looks  fast, easy, and cheap.

 

[milowebailey]

The sono has an air deflector that spins the beans.

Maybe Tex will shoot a photo of the air deflector in his... could easily make something similar to get the beans to stir.

[peter]

This dude pumps out 50K for $99.

No telling what the CFM's are or if they will loft a #.

http://www.lowes.com/lowes/lkn?action=productDetail&productId=154996-88644-RMC-FA50C&lpage=none

I know the Sono can work w/ propane, but for some reason I don't know that I'd want that thing blowing on my beans.

[John F]

The sono has an air deflector that spins the beans.

Maybe Tex will shoot a photo of the air deflector in his... could easily make something similar to get the beans to stir.

I thought the Sono was all fluid...there is an agitator involved?

I've only seen the pre Sono, I think it was the Monster and it looked like an erratic bounce of sorts and I assumed it was just the airflow.

If you just used the heat from the 50K, took whatever lofting you got from it, and supplemented with some sort of agitation there is little doubt it would roast.  

[John F]

I know the Sono can work w/ propane, but for some reason I don't know that I'd want that thing blowing on my beans.

Why not?

Propane burns clean and plenty of roasters use either it or natural gas.

[milowebailey]

The sono has an air deflector that spins the beans.

Maybe Tex will shoot a photo of the air deflector in his... could easily make something similar to get the beans to stir.

I thought the Sono was all fluid...there is an agitator involved?

I've only seen the pre Sono, I think it was the Monster and it looked like an erratic bounce of sorts and I assumed it was just the airflow.

If you just used the heat from the 50K, took whatever lofting you got from it, and supplemented with some sort of agitation there is little doubt it would roast.  

It is all fluid, but below the roast chamber there are fins that spin or direct the air mass in a circular direction so the beans stir.  I think it helps from having hot spots and allows for a more even roast.  This is especially important at the beginning of the roast when the beans have moisture and don't move very much.  I suppose if you have enough air moving it wouldn't be needed.

[peter]

I know the Sono can work w/ propane, but for some reason I don't know that I'd want that thing blowing on my beans.

Why not?

Propane burns clean and plenty of roasters use either it or natural gas.

I dunno, I guess I just have memories of working in someone's garage years back when maybe these things left an odor in the air.  One would have to see if the burners in these torpedo heaters are similar enough to the burners in a grill or commercial roaster.  The other thing about them, if I recall correctly is that some of them use the burner to heat a ceramic element and then the blower blows heat off of that, so it might not be heat from the flame directly onto the beans either.

$100 for the heater, $10 for a stock pot, and you're off to the races.

[Tex]

I know the Sono can work w/ propane, but for some reason I don't know that I'd want that thing blowing on my beans.

Why not?

Propane burns clean and plenty of roasters use either it or natural gas.

I dunno, I guess I just have memories of working in someone's garage years back when maybe these things left an odor in the air.  One would have to see if the burners in these torpedo heaters are similar enough to the burners in a grill or commercial roaster.  The other thing about them, if I recall correctly is that some of them use the burner to heat a ceramic element and then the blower blows heat off of that, so it might not be heat from the flame directly onto the beans either.

$100 for the heater, $10 for a stock pot, and you're off to the races.

Are you sure it wasn't a kerosene space heater?

[Warrior372]

Milo,

I believe that metal blade thing under the roasting chamber on the sono would be called a rotor-stator blade. They are used in the aeronautical engineering of planes as well as the mechanical engineering of turbo chargers. Their function is to intensify airflow, it creates a pull on upstream air, and it also makes the downstream air movement more erratic so it does not blow in a straight stream.

It is funny you mentioned that, because I was talking to a buddy, who is an aeronautical engineer, earlier today about ways to intensify airflow and make a vortex. . . . his short answer was a strator blade.

Cheers,
Mike