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Info On Centrifugal Roasters???
dBndbit
Here's an off-the-wall question... (that's a pun if centrifugal roasters work the way I think they might)

Does anybody have any info on how centrifugal roasters work? Not a roaster with a centrifugal fan, a roaster that spins the beans as a mechanically efficient means of agitation. I believe the beans spin in a big bowl and are forced up the sides where they decelerated and dropped back to the bottom of the bowl. There are some interesting possibilities here.

So far the only hard info I have is that Probat-Burns makes a pair of them, a really big pair. But nothing else shows up on searches.

Any thoughts or actual info???
Jim
11 years old... forever!
ReeferDoor.com
>home-built roasters and fair trade
 
http://www.ReeferDoor.com
coffeehound
Interesting. I did a patent search and found only this one coffee roaster that used the word 'centrifugal:' 5,292,005 Checkit out for yourself. www.uspto.gov
 
cup_in_hand
The idea behind a centrifugal roaster is to increase the amount of convection heat in the roaster to get faster roasting times, but have a much larger batch capacity. Because the beans are flat against the wall of the roaster, bean movement is more controlled than in a fluid bud roaster.
There is a thread on coffeeed Here on centrifugal roasters.
And probat has a brief description of the process here.
:)
Edited by cup_in_hand on 04/20/2008 3:08 PM
Anton
A life without coffee is a life not worth living.
 
seedlings
I don't know anything about them, but would love to see a video. Heck, I'd even take a cheesy CGI graphic.

coffeehound, I searched "centripetal" just in case, and it turned up nada WRT coffee.

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
boyntonstu
A souped up clothes dryer sitting on its back?;)
Edited by boyntonstu on 04/21/2008 1:42 AM
 
seedlings
cup_in_hand wrote:
The idea behind a centrifugal roaster is to increase the amount of convection heat in the roaster to get faster roasting times, but have a much larger batch capacity. Because the beans are flat against the wall of the roaster, bean movement is more controlled than in a fluid bud roaster.
There is a thread on coffeeed Here on centrifugal roasters.
And probat has a brief description of the process here.
:)


Fantastic links! I wonder how a smaller scale might fare? Hmmmm... let's see... a wok, a heatgun, a record player...

CHAD
Edited by seedlings on 04/21/2008 4:14 AM
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
coffeehound
You know, there are those stainless steel perforated cones people use for smashing food (twirling a round wooden masher) before canning it. I wonder if those cones could be used as a basis for a centrifugal roaster (CR)? They are about the right size and price for home roasting!

i16.ebayimg.com/08/i/000/eb/0a/e9c5_1.JPG
 
seedlings
From the picture in this link that cup_in_hand gave us looks like a saucer they rotate. You can almost hear the bald man explaining the process.

(I love the sign above the door)

CHAD
seedlings attached the following image:
centrifugal roaster dish[898].jpg

Edited by seedlings on 04/21/2008 4:53 PM
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
seedlings
And here's a picture of the lid... from:

http://www.probat...id=291&L=1

CHAD
seedlings attached the following image:
centrifugal roaster lid[899].jpg

Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
Dan
Are you sure they spin that 'saucer?' That gray thing on top of the 'lid' is one huge blower. The central hole is its intake. So huge amounts of heated air is being sucked out of the roaster. I doubt it is being sent up a stack. So, it must be returned to the roaster. I suspect that it is being returned through tangential openings at the bottom of the 'saucer.' That airflow would spin the beans, sending them around and up the saucer due to a centrifugal force until they spill back down. The turbine-like blades at the inside edge of the lid is further evidence of some sort of airflow being used to make this work.

My guess is that the saucer does not spin, but the heated air does. The heated airflow isn't powerful enough to spout the beans, but is powerful enough to get them to spin up that circular ramp (saucer).

This also suggests that the saucer isn't heated, but that the air is, perhaps by a heater off to the side heating the return air. If so, then centrifugal roasters heat by convection, not conductance.

That doesn't mean that a spinning conical saucer won't work, as seedlings and coffeehound suggested. And perhaps some centrifugal roasters do employ that technique.

Dan
 
http://www.intactamerica.org
dBndbit
I don't think so, Dan. Could be, but I'm still thinking the efficiencies of this roaster come from it's unique ability to separate the bean motion from the air motion. By that I mean one of the difficulties in air-spout roasters is that bean motion and air motion are locked together. High air velocity/pressure is both the heater and the mover. So a big blower are necessary, as well as a big afterburner to deal with the huge volume of dirty air.

But I believe the centrifugal roaster greatly accelerates the beans with purely mechanical rotation of the bowl. So a huge volume of air isn't required either for high heating rates or bean motion. In addition, bean circulation is accomplished by non-rotating scoops at the rim of the bowl. At the rim of the bowl the beans are already rotating at a high velocity. All the scoops need to do is slow down the beans and direct them back toward the center of the bowl.

I don't think those fins in the lid are a centrifugal fan. I think they're bean brakes. There's some new ways of thinking going on here. That's what caught my interest in the first place. That, and I have never seen any homeroaster anywhere try to build one. I think the primary bowl and scoops could be easily built from two identical stainless bowls. Add a third one for the lid.

Am I way off track here?
Jim
11 years old... forever!
ReeferDoor.com
>home-built roasters and fair trade
 
http://www.ReeferDoor.com
seedlings
Per Probat:

"One of the SATURN’s main components is its roasting drum, which consists of a roaster bowl and cover in which the coffee is agitated via centrifugal and Coriolis force. After attaining filling temperature, the bowl is filled with green coffee. The centrifugal force that develops via the rotation distributes the coffee uniformly across the whole surface of the bowl. A roast air stream is applied to the agitated coffee layer in the centre of the bowl so that beans are completely enveloped by the roast air. The roasting process can be stopped in a targeted way on the basis of a controllable water extraction mechanism before further cooling of the roasted coffee in the ring cooler below the bowl takes place."

However, it should read "coriolis effect."

CHAD
Edited by seedlings on 04/22/2008 2:23 AM
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
Dan
dBanbit, I don't think those fins are part of any centrifugal fan either. Clearly, the lid does not spin. I suspect they are used to aid the air rotation.

We know the bottom of the 'saucer' is open, since that is how they dump the beans for cooling. It could also be open for the heated return air from the blower above. That blower, which would be powered by a motor in the range of 20Hp, could easily induce the beans to spin.

If we had more images, perhaps we could figure out this riddle. And, perhaps there are two types of centrifugal roasters, one with, and the other without, spinning 'saucer.'
Dan attached the following image:
centrifugal_roaster[900].gif

Edited by Dan on 04/22/2008 4:33 AM
 
http://www.intactamerica.org
MarkBart
Wouldn't spin on the bowl cause the beans to be thrown completely to the rim and not
distributes the coffee uniformly across the whole surface of the bowl
?
To cover the whole surface of the bowl would take careful manipulation of the spin speed and be rather low, seeing how angled that bowl is.

Mark B.
I'm so Bad, I'm Good! www.homeroasters.org/php/images/smiley/cool.gif
I'm putting the small back into Small Business!
 
bvwelch
coffeehound wrote:
You know, there are those stainless steel perforated cones people use for smashing food (twirling a round wooden masher) before canning it. I wonder if those cones could be used as a basis for a centrifugal roaster (CR)? They are about the right size and price for home roasting!

i16.ebayimg.com/08/i/000/eb/0a/e9c5_1.JPG


No No No! Please don't turn that wonderful gadget into some sort of coffee roaster!

Instead, give it to someone you know who is into canning, along with a big batch of blackberries. Wonderful jelly (without the seeds) can be made with one of those gadgets!

-bill
 
dBndbit
MarkBart,
You make a perfectly logical observation. However, there is physics at work here and it's never logical! So your second observation is correct.

In fact, the shape of the bowl can control how the beans behave. There are two primary forces at work: gravity and centrifugal force. Gravity is always pulling the beans downward with the same force. Centrifugal force pushes the beans sideways - away from the center axis of the bowl's rotation. CF gets stronger if the drum rotates faster, but it also get stronger if the beans move farther away from the center even if the speed stays the same. Anyway, it's possible to shape the curve of a bowl to perfectly balance out the effects of gravity and CF, so that rotating at a specific RPM you could spread beans all over the inside of the bowl and none of them would move up or down, constant force perpendicular to the bowl surface. I believe the centrifugal roasters use this curve but they make the bowl just a little bit flatter or rotate it just a little bit faster, so all the beans would have a controlled tendency to slide on up to the rim in a fairly even procession.

I think I'm talking myself into building one of these out of the two big stainless salad bowls in our kitchen. Now, how can I get my wife out of the house for a day?
Edited by dBndbit on 04/22/2008 12:53 PM
Jim
11 years old... forever!
ReeferDoor.com
>home-built roasters and fair trade
 
http://www.ReeferDoor.com
seedlings
dBndbit wrote:
Now, how can I get my wife out of the house for a day?



May I suggest VISA

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
cup_in_hand
I wanted to look up some info on "packed bed roasting" which is another ingenuous roasting method related to centrifugal roasters; also developed by Probat/Burns. While looking for info I came across this page.
The menus at the bottom of the page have descriptions of their roasters and the concepts behind them.
Its a slide show for a presentation, so watch for the navigation buttons on the bottom of the pages.
Great info on types of heat and how the work.
Edited by EddieDove on 05/05/2008 1:25 AM
Anton
A life without coffee is a life not worth living.
 
cup_in_hand
I just realized that on that last link, when you click on a type of roaster, there are buttons on the bottom of the page. If you click the button on the bottom right that says 'flow diagram', then click the next button it takes you to a flow diagram of the roaster.
The diagram for the centrifugal roaster shows that it is a recirculating roaster that reuses the hot air.
If you turn the button for features off, it shows an animation and you can turn the other features such as air and temperature on and off and it will show you how they work.
Very cool.B)
Edited by cup_in_hand on 04/22/2008 4:32 PM
Anton
A life without coffee is a life not worth living.
 
Dan
Great resources!!!

So, there ARE two types of centrifugal roasters. Probat calls the shallow, spinning saucer type a 'Bowl Roaster,' and the deep, spinning bowl type a 'Packed Bed Roaster.' The Bowl type has a spinning bowl, which surprised me. I expected the Bowl to be stationary.

Both use recirculated heat, which I expected. Note that the airflow if down, into the center for the Bowl, but is reversed for the Packed Bed. From this we know that the 'lid' pictured above is for a Packed Bed, and not a Bowl type.

According to Probat, both roast primarily via convection. The container in the Bowl is solid, but the Packed Bed is perforated.

I don't know if these would work for homeroasters DIY. The problem in all recirculating designs is finding a heat resistant blower with the right flow and pressure.
Edited by Dan on 04/23/2008 2:43 AM
 
http://www.intactamerica.org
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