Homeroasters - Home Roasting Coffee Community » BUILDING A ROASTER » Fluidbed Roaster
Who is here? 1 guest(s)
Page 2 of 2: 12
 Print Thread
Large Hot-Air Roaster Blowers
lilboybrew
Top  #26 Print Post
Posted on 01/09/2007 8:58 PM
3-phase is always better than single-phase for efficient use of power, but to get the most out of your gear, you're going to need 3-phase for the VFD input as well (yes, some VFDs will give a 3-phase output with a single-phase input - but they pull a heck of a lot of current for the HP they deliver). As for the overload concerns, most VFDs will have built in electronic overload, just be sure to program it for your motor's rated current (and still monitor the motor temp and amp draw).

Quote

Dan wrote:

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.

Dan
To be good is noble, but to teach others how to be good is nobler...and less trouble.
- Mark Twain
 
Dan
Top  #27 Print Post
Posted on 01/29/2007 4:31 PM
Yup, I know that VFD come in 3-phase versions. I don't have 3-phase at home, so it is a moot point. I recall a discussion on another forum that showed that if properly wired, the difference in efficiency between 3-phase and single phase is in the one-percent range. Dunno if it is true, but like i said, a moot point for me.

Just to be clear, this setup draws about 5 amps on a 20 amp circuit.

At work it is another issue. I use 3-phase whenever possible, but not for efficiency sake. Rather, the wiring is less expensive to run and the motors last longer since there are no starter circuits or capacitors to deal with.

I jury-rigged the VFD on my wood lathe to spin the blower. I haven't done any tests yet, but will report back later. Dan
 
Web
Dan
Top  #28 Print Post
Posted on 02/19/2007 5:02 PM
Wes and I have been messing about with high pressure blowers with some amazing and encouraging results. High pressure blowers like this one are inexpensive and readily available.
www.grainger.com/images/products/enlarged/XL-7C447.JPG
I wondered if they couldn't be used for hot-air roasting. They normally spin at 3450 rpm. Larger ones will loft coffee beans, but they blow a lot of cfms, meaning they waste heat. I wondered if a smaller blower spinning faster would work. It does!

I replaced the 1/2Hp single-phase motor with a 3/Hp 3-phase motor and jury-rigged it to a VFD I have. To test it, I necked the blower's 3" x 3" exhaust to 1" diameter.

60 Hz, 73 dB, 3450 rpm (normal speed), 3.95 inches of water pressure
75 Hz, 77 dB, 4315 rpm, 6.15 inches of water pressure
80 Hz, 78 dB, 4600 rpm, 6.70 inches of water pressure
85 Hz, 79 dB, 4900 rpm, 7.75 inches of water pressure

I think that is plenty of pressure to get a bed spouting and keep it there. As the beans lose density, the blower speed can be gradually reduced for best spouting action and heater efficiency.
Edited by Dan on 02/19/2007 5:04 PM
 
Web
RoasterRob
Top  #29 Print Post
Posted on 03/04/2007 5:32 PM
Hi guys

I only just found my way to this forum last nite.

Dan i came to the conclussion that the side channel blower is the best bet and it would appear that is the way the air roaster manafacturers have gone. I am just in the process of building a 7 - 10 kg gas air roaster. I'm making it in wood first to test it cold with a load of 10kg of green and then a load of 8.3kg of roasted. The wooden panels are being cut by a local joiner ready for pick up tommorrow. I hope to assemble it thru/by the w/e and start testing it next week or sooner. The figures i am working on are a max flow of approx 2.5 cubic metres/ minute and pressure around 14inches of water as a minimum.
Hopefully this discussion will carry on and i will be adding my 2c worth from time to time.

Rob
 
Dan
Top  #30 Print Post
Posted on 03/04/2007 7:10 PM
Rob, What is a side channel blower? Got any pictures? Dan
 
Web
RoasterRob
Top  #31 Print Post
Posted on 03/05/2007 3:39 AM
Hi Dan

I was talking to a friend (whose company supply compresser & vacuum systems) about ring compressors he looked blank and and then suddenly said "you mean a side channel blower". I have referred to them as that since. Viridian has a Fuji unit, same thing again a different name "regenerative blower".
This friend i mentioned said they are bullet proof, he didn't think a vacuum cleaner motor would last long in that application.
As an aside my 900watt 2nd hand electrolux motor has done at a guess 750 or more roasts and still going strong.
From reading earlier parts of this thread just some info about my roaster that may or may not be of interest. The roast chamber on mine is 150mm dia the bed of green beans at the start is 220mm high and the beans spout about 150mm above this 220mm at the start of the roast. At the end they are spouting much higher and that is with blower turned down alot.

JMO but i think the bed height versus width or diameter should (or could) be at least 1 to 1. I origianlly built the 6" roast chamber as a 1.3kG (green) roaster, turned out it could easily roast 2.1 kg.
I would expect an 8" roast chamber to be capable of roasting 4kg of beans. Seems to me a larger diameter RC with a thinner bed of beans would waste more heat.

After searching thru the web for what roaster builders are using i found this pic, (pic 2 & 3 )

http://www.coffeed.com/gallery/slideshow.php?set_albumName=album03

also when these guys built their roaster they went for side channel blowers as well. One of these guys posted to a.c briefly last year.

http://www.scottbroscoffee.com/about/frameset_photo.htm

So i am gonna bite the bullet and get a side channel blower, unless of course your further experiments proof a blower like the Dayton can do the job.
Once i get the wooden roaster mock up made i ntend to test it using 2 -3 vacuum cleaner motors and i will measure pressure in inches of water and calculate the flow thru the beans.

more soon

Rob
 
Dan
Top  #32 Print Post
Posted on 03/05/2007 10:14 AM
Aha! A regen! Both Wes and I were (note the past tense) convinced that regens would be the way to go. They are high pressure output. I have no doubt they could be used on hot air roasters up to about 5-10 pounds.

What Wes and I determined was that, in regard to a 10-20 pound hot-air roaster, they run out of volume in taller beds.

What I like to say is that regens are powerful on pressure, but puny on volume. On the other hand, high-pressure centrifugal blowers are powerful on volume, but puny on pressure.

What we have found is that by adding a VFD to a high-pressure blower (as described above), not only do you have infinite control over speed, but you can spin the blower faster than the nominal 3450 rpm. This increases pressure to keep a taller bed of beans spouting.

While you could just buy a larger (2-5Hp) regen to do the job, we think a .75-1Hp high-pressure blower will do the same or better job, and cost less. They would have the same life expectancy of the regens, since the weak link in both are the motor bearings.
 
Web
RoasterRob
Top  #33 Print Post
Posted on 03/09/2007 5:55 PM
Is there anything out there that is a compromise between the regen and a "high" pressure blower?
I had thought about making my own blower, i would look at getting parts laser cut - disc and blades for the impellor etc. Would probably be looking to nearly copy a vacuum cleaner setup, with a (probably) 8" diameter impellor and whatever modes to suit a blower instead of a sucker based on what i can glean from people that know more than me. Just thinking out loud at this stage and most probably will just go for a regen. Cost for one here in NZ is about $1k, then there is the cost of a VFD to control the speed of the motor.
Got the wooden test bed 75% constructed just need to drill a plate with the right perforations about 200 x 3.3mm by my calcs. then test it with the 2 or 3 vacuum motors to see if it behaves like i hope. More on that soon.
Hey Erik you out there? Any progress with your roaster.

Rob B)
 
Dan
Top  #34 Print Post
Posted on 03/10/2007 7:57 AM
Rob, None that I know of, and I've spent some time looking. If there were, it would be a centrifugal blower with enclosed vanes. That is, exactly as you have come up with, a scaled-up version of a vacuum motor. That impeller is enclosed. That is, it has a front disc as well as the required back disc. This prevents leakage pass the vane edges. At 8" you would still need to spin it faster than a 3450 rpm motor to get the pressure needed. If you made the diameter larger, you might get it to work on a 3450 rpm motor without speed control.

FYI: The high-speed blower wasn't noisy, about 78dB at max speed. I would still put it in an enclosure or in the next room. Regens are unbelievably noisy! Their construction is very close to those old mechanical sirens. That is why everyone comes with integral mufflers on the intake and exhaust.

There are lots of regens on eBay. Before you buy, get a copy of its performance specs and compare it to my spreadsheet on the Downloads section so you know you have the right unit for your needs.
Edited by Dan on 03/10/2007 12:21 PM
 
Web
Dan
Top  #35 Print Post
Posted on 04/14/2007 8:37 AM
The variable speed drive (VFD) driving a high-pressure blower test was a success. At last week's midwest HUGS we jury-rigged a blower and VFD like this one:
www.hitachi.us/siteimages/forbus/powerequipmentsystems/Inverters/L200_Series-1.gif
The 3/4Hp motor was able to keep 20 pounds of beans spouting pushing 2.65" of water pressure through a 3" perf plate (5/32" holes) while pulling 2.8 amps. The was overloading the motor slightly, which is rated at 2.6 amps, but within its duty factor.

This would be a good combination for a 15# roaster. For 20# I'd go with a 1Hp motor.

We were not able to use the VFD to rev up the blower to get the beans spouting except on one test with fewer beans. However, a person could start a few beans spouting and then pour in the rest. Or, we discovered that a spoon-shaped paddle could reach down and jerk start the spouting action.

The VFD was easily adjusted to keeping the beans spouting. I can imagine that some sort of feedback device or sensor could automate this, too.

What this means is that a 15-20 pound hot air roaster is within the budget and availability of a serious home roaster or small commercial roaster.
 
Web
seedlings
Top  #36 Print Post
Posted on 08/15/2007 2:00 PM
I just ran across this thread. What type of heat are you thinking of using? And, is this still a work in progress or did you all give up?

CHAD
 
tamarian
Top  #37 Print Post
Posted on 12/12/2013 8:19 AM
Dan, I was looking at your spreadsheet, and wanted to understand the setting so I can digest the numbers.

Is this a cone design fluid bed, where the perforated plate is in the center?
Is the non-perforated area at the bottom horizontal or angled?
Is the bean bed height taken from the sides or center?
By orifice, you mean drill size?
Orifice area is the drilled circle area?
Open area is orifice area multiplied by number of orifices?
What is nominal bed area ratio?
What is orifice/bed area ratio?

That's all I wanted to ask smile
Wa'il. 1 Kg PID'ed gas-fired fluid bed roaster, GS/3MPS, K10F
 
Web
Page 2 of 2: 12
Jump to Forum: