Homeroasters - Home Roasting Coffee Community » BUILDING A ROASTER » Fluidbed Roaster
Who is here? 1 guest(s)
Page 1 of 2: 12
 Print Thread
Large Hot-Air Roaster Blowers
Dan
Top  #1 Print Post
Posted on 10/09/2006 8:47 AM
We've talked about making large fluid bed roasters in the five pound range. I thought the Dayton high-pressure blowers would make a good prime mover. They are reversable, and the casing can be turned every 45?. They come in many sizes with and w/o motor. I have a Grainger 2C940 (7D747 w/motor). It ha a 7.75" wheel with 1/2 Hp motor, and is rated 3 inches water column at 157 cfm.

www.grainger.com/images/products/enlarged/XL-7C447.JPG

I tried my blower to fluidize some beans. The chamber was 7", necked down at the bottom to 4", with a flat-bottomed 4" diameter floor. In the center was a 1" orifice. I selected the 1" orifice because any smaller the and blower shutoff.

With this unit I could keep 2 pounds of beans spouting. Any more and it stalled.

For comparison, I used my shopvac to power the chamber. I believe it is a 1-stage vacuum motor. It can spout 3 pounds of beans.

This does not look good for using the Grainger blower series. With some modification to the wheel and casing, I'm sure it could be made to spout 3 pounds of beans. If you were to use a 3-phase motor on the modified blower and power it by a VFD, you could increase the motor speed and spout, say, five pounds.

By the time you did all of that a used regenerative blower, although more expensive, might be just as effective. Perhaps a 2 or 3-stage vacuum motor (aka shopvac blower) could be employed, although it is loud.
 
Web
Ascholten
Top  #2 Print Post
Posted on 10/09/2006 3:28 PM
Go to any AC/R shop and get a squirrel cage / centrifugal blower such as this. They come in both 115v and 220 v models. Some of them can really move some air, and are actually pretty quiet and you are not talking needing a power plant to run them.

Having the chamber go from 4 inches to 7 inches is a bit of a pressure drop on the expansion there. Have you tried just a straight walled yet?

Also on the wet / dry vac motor idea, it will actually blow a bit more air if you take it out of the can and run it in free air. Might be a bit quieter as well w/o the resonances going on inside that can too.

Just some other ideas.

Aaron
Bean there Done that, donated the T-shirt to the Church of the Second crack.... St Beanyface
 
scotthal
Top  #3 Print Post
Posted on 10/09/2006 3:41 PM
Have been using a wet/dry vac in a small (<1.5lb) fluid bed prototype for the past couple of months. Only needs 80V for that size load, which quiets it down a bit; and taking advantage of the flex hose to park the canister under the workbench gets rid of a lot of the direct / high-frequency schtuff.
Edited by scotthal on 10/09/2006 3:42 PM
Food for thought; coffee for concentration
 
Dan
Top  #4 Print Post
Posted on 10/10/2006 6:38 PM
I now have a manometer to measure low pressures like "inches of water". What I'm going to do is rig up a spouting type bed with variable size orifice and record the pressures. I'll test at various bed heights, too. With some calculations I could get cfm, too. It should be a valuable resource for hot air roaster design. Just what I need, another fun project.

This came about because of the alt.coffee thread: Re: stainless steel pipe style coffee roaster.

Dan
Edited by Dan on 10/10/2006 6:39 PM
 
Web
Viridian
Top  #5 Print Post
Posted on 10/12/2006 10:36 PM
Dan, I found you! The alt.coffee thread has been great. I was just checking out the blower curves on my two regenerative blowers and comparing the numbers with what Alchemist John's fluid bed spreadsheet spit out. My 1hp regen should be able to fluidize about 10lbs according to his numbers in a true fluid bed. I doubt this to be true but I am gearing up to test it. The 2.7hp hi pressure regen scares me to think of it.

Erik
 
Dan
Top  #6 Print Post
Posted on 10/13/2006 10:09 AM
HI! Yes, that thread has gotten my curiosity up and interested in having some fun for a change. I've been extra busy at work for the past 6 months and finally it is tapering off.

I will know more this weekend as I gear up for testing spouting beds. I ordered 20# of greens so I could test a large batch. I'll start with various heights using 5#. I'll post a picture of my testing bed here soon.

Your 1Hp should be able to spout 40 pounds, I'd think. That is the beauty of a spouting bed, lower airflow.

Oh, it takes 0.018 BTU to raise one cubic foot of air 1?F. Once you know your flow, you can estimate your burner size.
 
Web
Mike
Top  #7 Print Post
Posted on 10/13/2006 11:20 AM
Dan,

I've been following the 'stainless steel pipe style coffee roaster' with interest. A lot of good info.

Looking forward to the pics.

Viridian,

The 1/4 bag Sivitz uses a 3 HP and moves more air than is needed for 15 Kilo.

Mike
B)
Edited by Mike on 12/30/2006 9:20 PM
 
Dan
Top  #8 Print Post
Posted on 10/13/2006 6:52 PM
Good to know, Mike. That gives us a upper bound. It sure is looking like only triple-stage centrifugal blowers and regenerative blowers will work for spouting beds larger than, say, 500g.

 
Web
Mike
Top  #9 Print Post
Posted on 10/13/2006 8:44 PM
Dan,

The vacuum cleaner two stage centrifugal that I have been experimenting with worked well for one pound (~450 gms) turning at about 3500 RPM. The trouble I've run into (other than life getting in the way of my projects) was noise. There was plenty of OOMPH left in the fan if a guy wanted to turn it faster - the noise seems to go up at a logarithmic rate with increased speed. I really like the idea of a direct drive impeller rather than pullies, countershafts etc.

I successfully roasted 725 gms with it turning at ~ 5000 RPM.

I keep thinking that a little more attention to detail and hideing the fan deep in the construct would work out well.

Mike
B)
 
Viridian
Top  #10 Print Post
Posted on 10/16/2006 2:26 PM

Quote

Dan wrote:
Good to know, Mike. That gives us a upper bound. It sure is looking like only triple-stage centrifugal blowers and regenerative blowers will work for spouting beds larger than, say, 500g.



Dan, I am using two stage blowers in my 15lb'er. Thanks to both you and Mike for the tips. Very valuable. I spoke with "Alchemist John" last week and he was also a wealth of good information, but I kind of doubt being able to use his spreadsheet to accurately forecast blower requirements. He recommended making changes to spherocity and tube diameter values to closer approximate spouting bed properties. I just don't know without the proper measuring equipment how the numbers match up to my own setup.

Do either of you know what the maximum bean bed depth would be for a spouting bed? Taking into consideration how often the beans circulate I am worried about the heat transfer in a taller column. I am just guessing that a 6" column is about as much as I would want. What do you think?

Erik
 
Viridian
Top  #11 Print Post
Posted on 10/16/2006 2:29 PM

Quote

Dan wrote:

Oh, it takes 0.018 BTU to raise one cubic foot of air 1?F. Once you know your flow, you can estimate your burner size.


I look forward to seeing what you find.

Thanks,
Erik
Edited by Viridian on 10/16/2006 2:33 PM
 
Dan
Top  #12 Print Post
Posted on 10/18/2006 4:42 PM
Viridian, A bed can be any depth, its just that the pressure rises to the point of not being effective. I'm beginning to think, just a gut feeling, that bean depth is best at about 1/3 to 2/3 of the chamber diameter.

I've finished the 5# tests. I got 20# of beans in, so I'm beginning the 10# in next. smile
 
Web
Viridian
Top  #13 Print Post
Posted on 10/19/2006 5:19 PM

Quote

Dan wrote:
Viridian, A bed can be any depth, its just that the pressure rises to the point of not being effective. I'm beginning to think, just a gut feeling, that bean depth is best at about 1/3 to 2/3 of the chamber diameter.

I've finished the 5# tests. I got 20# of beans in, so I'm beginning the 10# in next. smile


Dan, right, I know what you mean but I feel that the heat transfer rate will suffer if you go too deep. IE, the air will give up its heat long before it reaches the top of the bed to spout if the bed is too deep. I am guessing that there is a balance between the circulation rate and bean bed depth that I haven't found yet. Or something like that. At this point i agree with you that 1/3 to 2/3 of chamber diameter for bed depth sounds ballpark.

You have been able to loft 5# with that new blower? Very cool. How many dB?

I just got some 4" steel tubing with a 90deg mandrel bend for connecting between my heater tube and the bottom of the roast tube cone. Not sure when I will get it hooked up. Not this weekend.

Erik
 
Dan
Top  #14 Print Post
Posted on 10/21/2006 6:02 PM
Viridian, It might not be as bad as you think since the beans are moving up with the heated air.

I've finished my tests! I measured the static pressure needed to spout 5, 10, 15, and 20 batches using a wide variety of orifice sizes from 0.5% to 8% of the bed diameter. I think the best way to use this as design information is to draw a nomograph that people can download and print to use. I'll work on that this week.

I found this neat online calculator for airflow! I used it to calculate all my CFMs.

http://www.pipefl.../index.htm
 
Web
Viridian
Top  #15 Print Post
Posted on 10/24/2006 12:05 AM

Quote

Dan wrote:
Viridian, It might not be as bad as you think since the beans are moving up with the heated air.

I've finished my tests! I measured the static pressure needed to spout 5, 10, 15, and 20 batches using a wide variety of orifice sizes from 0.5% to 8% of the bed diameter. I think the best way to use this as design information is to draw a nomograph that people can download and print to use. I'll work on that this week.

I found this neat online calculator for airflow! I used it to calculate all my CFMs.

http://www.pipefl.../index.htm


No question, you are the man!s:1

I look forward with bated breath to seeing the results.
 
Dan
Top  #16 Print Post
Posted on 11/02/2006 11:04 AM
Me, too! Work has been hectic and all I've been able to do is put a blank piece of paper on my drawing board. :( Wes is thinking of visiting to check out my testing rig before he committs steel to weld.
 
Web
Dan
Top  #17 Print Post
Posted on 11/18/2006 9:06 AM
Update, Wes came by last weekend and we spent 5 great hours talking hot air roaster design, pouring over catalog sheets, and messing with my test rig. Wes is serious about a 15# hot air roaster for commercial roasting. If anyone will make this work, Wes will. He's one determined guy.

I continue to test, learn, and retest, so don't have anything to share just yet, but will very soon.

Since I began, we have purchased a Dayton 2C820 1/2Hp, 9" wheel blower at work. It replaced the smaller 7.75" blower shown in the photo above. Since I had my test rig, I decided to see what this blower could do. Sure enough, it can spout beans!

The jury-rigged chamber I used for this test was 10" in diameter with 30? funnel bottom, and 50% open area 3" diameter perf plate at the bottom.

The blower could start and sustain a 5# charge of beans (3.5" DP). It could not start anything deeper, but if the beans were agitated manually, or poured in slowly, it could sustain a 15# charge of beans (7.5" DP). This meant that the blower was operating at 5.5 inches of water pressure (its upper limit).

Wes and I both feel that these Dayton blowers have potential for large hot air roasters. Either the 9" wheel, or the next larger unit with 11" wheel. What we think would be ideal is if the blower was powered by a 3-phase motor controlled by a Variable Frequency Drive (VFD). In this way the roast-meister would have good control over spouting and airflow usage. VFDs have the added advantage of permitting turning the motor faster than normal. This means the motor could be spun up fast enough to get the spouting action started, then backed down to a reasonable amount. This is important since it costs to heat every cubic foot of air you move through the beans.
 
Web
Dan
Top  #18 Print Post
Posted on 12/26/2006 4:43 PM
I have added my Spouting Bed Tests to the Download section. Ssee menu at upper left, or below.

http://forum.home...p?cat_id=1

Based on these tests, it appears that the next size larger Dayton high pressure blower would serve well for a roaster. I am talking about the 2C820 blower, 8 15/16 inche wheel. I would power it with a 3/4Hp, 3450 rpm motor. By using a variable frequency drive (VFD) and a 3-phase motor, you would have variable speed as well as the option to turn the blower faster than 3450 rpm, which may be required to get beans moving at first.
Edited by Dan on 12/28/2006 6:52 PM
 
Web
Mike
Top  #19 Print Post
Posted on 12/30/2006 9:19 PM
You guys have been coming up with some good data. How is the roaster project itself going?

BTW in a previous post (I've just been re-reading the entire thread), I stated that the 1/4 bag Sivetz used a one HP motor......wrong......it uses a three HP motor. Visualize me hanging my head in shame. :( I'll edit the post with the correct #s.

The three HP motor on the Sivetz is definately overkill.......by how much, I'm not sure.

Mike
B)
 
lilboybrew
Top  #20 Print Post
Posted on 12/30/2006 9:49 PM
Just remember that when you use a VFD to go above the motor's base speed (i.e. 3450 RPM) you will be increasing the frequency going to the motor but not the voltage (the voltage would be maxed when you reached base speed). Therefore, the motor's torque would actually decrease, even if the speed increases. If the motor were at full load already, it would overload when you went above base speed.

But it sounds like you guys are onto some good ideas. Any plans to PID the temp control?


Quote

Dan wrote:
I have added my Spouting Bed Tests to the Download section. Ssee menu at upper left, or below.

http://www.homero...p?cat_id=1

Based on these tests, it appears that the next size larger Dayton high pressure blower would serve well for a roaster. I am talking about the 2C820 blower, 8 15/16 inche wheel. I would power it with a 3/4Hp, 3450 rpm motor. By using a variable frequency drive (VFD) and a 3-phase motor, you would have variable speed as well as the option to turn the blower faster than 3450 rpm, which may be required to get beans moving at first.
To be good is noble, but to teach others how to be good is nobler...and less trouble.
- Mark Twain
 
Dan
Top  #21 Print Post
Posted on 12/31/2006 2:20 PM
Mike and Lilboybrew, Wes and I continue to discuss details and I am confident that if anyone can use off-the-shelf components to make a working 15 pound roaster Wes will. I'll let him brief you on his progress.

Lilboybrew, you are right about the voltage, that is why Wes is going to purchase a larger HP motor than the blower normally would require in order to eliminate the overload problem. Also, he won't be using overspeed for a long duration, just to get the beans spouting, or for the first few minutes until dense beans lose some water.

I have a used Dayton 2C940 8" wheel blower. If I can find a 3/4 Hp 3-phase motor here or at work, I'm going to install an eBay VFD and see just what kind of performance I can get out of it. Now that you have brought up the overload problem I'll monitor motor temp and amperage draw.

Wes plans on PIDing his electric heater. Blower motor will be manually controlled for best spouting action.

Dan
 
Web
Javadude
Top  #22 Print Post
Posted on 01/02/2007 7:36 PM
http://www.sivetz...#1/2%20bag c:5
Edited by Javadude on 01/02/2007 7:38 PM
 
Dan
Top  #23 Print Post
Posted on 01/08/2007 7:20 PM
The Sivetz is interesting. Most of the parts are off the shelf industrial equipment or simple, shop made parts. Note that the cooling blowers he is using on the 5-8-12 pound and 1/4 bag roasters is the same blower I specified on the first post!
 
Web
Mike
Top  #24 Print Post
Posted on 01/09/2007 1:32 AM
Dan,

I think the blower that you see in the pictures of the 1/4 bag sivetz (same as the smaller roasters) is the blower used for the cooling tray. The blower used for air flow thru the roaster is a larger model (I believe).

Mike
B)
 
Dan
Top  #25 Print Post
Posted on 01/09/2007 8:24 PM
You are right, it is for cooling as evidenced by the fact that the ductwork is connected to the inlet side. I was just commenting that this blower has attracted the attention of a commercial roaster mfgr. I can't see what blower he is using on the roaster itself since in both pictures it is hidden from view. However, since one Dayton blower is used it may very well be a similar blower powering it as well. Dayton makes that blower in a variety of sizes. Mfgrs prefer to purchase from as few vendors as possible to keep purchase costs, inventory and shipping costs down.
Edited by Dan on 01/09/2007 8:25 PM
 
Web
Page 1 of 2: 12
Jump to Forum: