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

[Warrior372]

Hello Everyone,

I am tossing around the idea of building a fluid bed roaster and I have a few questions for all of you. What is the average air flow rate on machines such as a Sivetz 1.25lb machine or Sonofresco's 1 and 2 pounders? Is the air flow rate adjustable on these machines? If so, what is the range? What is the temperature range on them?

Thanks for the help!
-Mike

[peter]

Mike,

I can't help you, but think that 7over is the member to ask.  He's been a bit busy lately, and may not see this.  If you don't see him post before long, send him a PM.  Pete designed the roaster his Second Chance Coffee Co. is using.  That beast is a FBR, and I think its range is from 2.5-16lbs. 

I hope you have deep pockets and metal fabricating equipment. 

[J.Jirehs Roaster]

Hello Everyone,

I am tossing around the idea of building a fluid bed roaster and I have a few questions for all of you. What is the average air flow rate on machines such as a Sivetz 1.25lb machine or Sonofresco's 1 and 2 pounders? Is the air flow rate adjustable on these machines? If so, what is the range? What is the temperature range on them?

Thanks for the help!
-Mike

7over definitely has better answers..  if you are going to dabble I can tell you that the green beans are just barely moving in the 1# sonofresco at the beginning of the roast, and the speed stays the same throughout the roast... the heat cuts on and off but the fan stays steady..  so far in my experience the temp range on any roaster needs to be a very controllable 200 to 500 deg F  (you should not need 500 deg... I like insurance)

[John F]

All I have is a very non scientific answer that sounds sarcastic.....can't figure out a non sarcastic way to say it.

I think you want enough to fluidize the bed without blowing past/through it. 

Just enough to loft IOW.

The fluidizing isn't roasting it's agitating.

But ask 7 over.   

[J.Jirehs Roaster]

All I have is a very non scientific answer that sounds sarcastic.....can't figure out a non sarcastic way to say it.

I think you want enough to fluidize the bed without blowing past/through it. 

Just enough to loft IOW.

The fluidizing isn't roasting it's agitating.

But ask 7 over.   

what he said... the beans are heavy at the beginning so good loft at the beginning is launch at FC

[garybt3]

Hello Everyone,

I am tossing around the idea of building a fluid bed roaster and I have a few questions for all of you. What is the average air flow rate on machines such as a Sivetz 1.25lb machine or Sonofresco's 1 and 2 pounders? Is the air flow rate adjustable on these machines? If so, what is the range? What is the temperature range on them?

Thanks for the help!
-Mike

Check these guys out if you are planning on building your own roaster...

http://www.homeroasters.org/

tell Eddie that Gary sent you ;-)

[Warrior372]

Thank you to everyone for the info so far. I know how much I want / need the beans to move, and I know that the size of the roasting chamber and the amount of beans I want to roast play a factor. I am just after specific air flow rates so I know if I can use a heat gun in conjunction with a heat gun or if I need something more like a heat blower in conjunction with a high power fan. Each heat gun / blower and fan you look at has specific flow rates, some are adjustable some are not. Sixty dollar heat guns from the hardware store have adjustable heat ranges from about 200-500 degrees fahrenheit.

I am sure that throughout the process I will have to purchase and return several items to get it right. I just want to limit the number of times I need to do that .

Thank you for adding that the flow rate on the 1lb sonofresco is steady throughout the roast. Stuff like that will be very helpful! Is the heating element turning on and off to adjust to the roast temperatures you programmed the sonofresco to hit at different times in the roast?

Gary, thank you for the homeroasters.org recommendation. Some people have some pretty crazy ways of roasting! I thought I was creative until I saw what some of those engineers did!

Thanks,
Mike

[Ascholten]

the velocity of the airflow plays a part too.

10 CFM through a 1 foot diameter pipe is probably not going to move the beans too much.....  10 CFM through a 3 inch diameter pipe will move them pretty well.... so if you are having problems with bean movement, you also might want to look into the diameter of your roasting chamber.

you mention heat guns having variable heat,  they do this by opening a louver on the side to let more air in / out of them I believe,  you might also be able to use this as a flow control too.

Another thing to remember is, some beans are kind of... abrasive and don't float very well, while others rattle and roll really easy.

Aaron

[J.Jirehs Roaster]

the profile on the sono is always the same... it is just longer for darker roasts... this is not the best way, just the sono way... I remember seeing a home roaster with a heat gun for heat and a leaf blower for fan... (I don't know if it worked)

I would get the hottest heat gun, you can turn them down but you can not turn them up past high..

I separated the heat and fan on a cheaper Warner heat gun... same as the hot air poppers.. so I could hook it up to my PID for a bread machine roaster... the $20 one is a little wimpy ... hopefully I can tweak the $50 one the same way...

I don't know how much you can roast off of just the heat gun... and even with the really hot one and a second fan you will probably rapidly loose temp... maybe 2 or 3 heat guns into a manifold???

the heat guns most people use for dog bowl and bread machine roasters is simply a heat coil in a wind tunnel.. no louvers that I have seen

I have thought about heating elements out of pottery kilns and a squirrel cage blower...  but if I go that wrought I will build a drum roaster instead...   ceramic drum?!?!

[Warrior372]

Grainger has a heat gun that is adjustable from 300-500 degrees with an airflow velocity of 3000FPM and a volume of 30CFM. Unfortunatley that does not mean anything to me. That is why I am curious of the airflow velocity and volume of the Sonofresco and Sivetz. Achieving roasting temps really should not be an issue, as you can purchase a heat blower and most seem to be adjustable up to 1650 Fahrenheit. I will put the receiving end of a digital thermostat in the roasting chamber so I can measure the actual air temp within the chamber.

I know that if I use a fan to supplement the airflow velocity and volume from the heat gun that it will be throwing ambient room temperature air into the chamber too, so I will have to have a gun that can adjust up high enough temp wise to outweigh the ambient air.

A PID would be optimal, but unfortunately I have no idea how to rig one of those to a heat gun .

It is funny you mentioned the fluid bed roaster that uses the leaf blower and the heat gun! There is a video of that on youtube. I just typed in fluid bed coffee roasters and his came up. It seemed to get a nice result too!

Thank you for the continued input!
-Mike

[John F]

Now I think there is enough info to say you need "more".

Fluidizing 1.25#'s of beans is going to take more than a heat gun for sure.

I think more than 2, 3, or 4 heat guns even.

[Warrior372]

There is a difference between a heat gun and a heat blower. The air volume of a normal $50 dollar heat gun is about 7 CFM and from a $125 dollar heat blower is 30-45 CFM. It is like a blow dryer on steroids. Then if you get into industrial heat blowers they go up to 800 LPM and fully adjustable temperature up to 1650 degrees. One of the recommended uses on the most expensive model is deicing construction cranes. . . . and it weighs under 20 lbs. I feel that it is safe to assume something between the two extremes I just mentioned is being used in the sonofresco and the sivitz, but obviously in a much flashier package. I highly doubt they invented a new way to heat and blow around air. They just put a cool exterior around a heat source, fan and a computer. The readily available fluid bed roasters are very cool. . . trust me I am saying anything bad about any of them !

Sivitz actually uses one of the hot air guns that is around 30 CMF in their 30 gram gun roaster. So, obviously a 1lb sono or 1.25lb sivitz must use more than 30 CMF. . . .

I am just trying to gauge what I need to to buy in terms of the heat source and possibly a type of fan to supplement airflow. Unfortunately the industrial heat blowers I have found are only available online, so I cannot go and play with them.

Thanks,

[rasqual]

I've looked at this manufacturer for a couple years.

[Warrior372]

I got some feedback from Sivetz. They stated their airflow is adjustable, and it needs to be because the top of the roasting chamber is open to the ambient air. They also said that the temperature at the top of the roasting chamber is 480 degrees during roasting.

Thanks,
Mike

[milowebailey]

Now I think there is enough info to say you need "more".

Fluidizing 1.25#'s of beans is going to take more than a heat gun for sure.

I think more than 2, 3, or 4 heat guns even.

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

Input rating (propane): 31,000 BTU/hr

a heat gun typically has:

Dual Heat - 600 or 1,000° F - Nozzle Attachments included
1200 watts max 120vac UL Listed, 115V AC A dual range heat gun for use in heating shrink tube and drying coatings, adhesives, etc. Low temperature range setting produces a nominal 700°F (2,000 BTU's), high range 975°F (4,000 BTU's). Maximum setting draws 10 Amps, low heat draws 5 Amps.

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