topbanner.gif
Login
Username

Password




Not a member yet?
Click here to register.

Forgotten your password?
Request a new one here.
Shoutbox
You must login to post a message.

allenb
11-15-2018 13:26
Cwilli62 Welcome

JackH
11-14-2018 10:26
Welcome joycan coffee drink

JackH
11-12-2018 08:50
welcome2 gtroaster15

JackH
11-09-2018 12:21
Welcome SPQR

JackH
11-07-2018 21:29
welcome2 John brown

Shoutbox Archive
Users Online
Guests Online: 3

Members Online: 1
pablo

Total Members: 5,573
Newest Member: sitanggang
Donations
Donations Bank

Latest Donations
PRABHATH COFFEE WORKS - 10.00
John Despres (Scene... - 25.00
snwcmpr - 10.00
Ozo - 20.00
Josh Woodrow - 10.00

View Thread

Homeroasters.org » BUILDING A ROASTER » Fluidbed Roaster
Who is here? 1 guest(s)
 Print Thread
Modular Fluidbed Roaster
Brandon
It's been a couple years, but I built KKTO roaster some time ago (based off farmroast's excellent design) with the expertise I gleaned from you guys. It's been functioning pretty well, and life happened so I've been away for a bit, but thinking I might take on a new project again. I roast regularly, but it's been of maintenance hog and probably needs a clean clean rebuild, but I've been looking at the fluidbed route.

I'll be reading to catch back up and learning this type of roaster, but looking forward to it. Hoping to build a smaller roaster (300-500g) first, and perhaps something larger once I get a feel for it. After a while I was able to sell on a small scale to pay for the habit, gave that up due to the maintenance issues on my original build.

Looking forward to mixing it up with you all again. Cheers!
Edited by Brandon on 10-25-2018 15:35
 
Brandon
So I let this thread lapse a little bit, huh. Life happens yanno. But, I'm back to planning stages again.

Goals for this build
- Fluidbed
- Minimal moving parts
- modular design (more on this below)
- max load: 4-5kg
- dump chute into cooling


I've read through some of Roaster Rob's designs and I've looked through PhilH's and mustangs (all great builds) Originally, I had considered buying the heating element from the coffee crafter's Artisan 9 roaster as it should meet the requirements (and I have a constant fear of blowing myself up with propane), but it'd require running a new line with a 60A breaker, so that's out for now. But I'm looking to try and build the roaster in three modular segments, the blower box, hot box, and the RC. The hope is to give flexibility and options, but maybe it's too much.

Blower Box
- vacuum blower. There looks to be a good one that someone (allenb?) linked in another thread. If it can't lower enough to not shoot a small roast to the moon, I will likely add a smaller one for that purpose.
- Would always remain the base in this modular design.
- made from some thick plywood I have, but will spray from the inside to seal it from leaks

Hot Box
- ideally have two versions, one fit with an electric version with elements in it, and one for gas.
- have sight glass to monitor heat situation

Roast Chamber
- Also two versions: one for small batches and one for larger batches.
- square tubes with sight glass for monitoring
- dump chute at base of RC to empty for cooling


I still have a couple questions, as I'm working through it.
- Aluminum or SS? I'm not the most skilled metalworker, so aluminum is likely easier, but if stainless is much better, I'll look at it. Will almost certainly use square tubes similar to mustang's build.
- Based on some math from another thread, it looks like 1 cu ft will hold 42lbs of green or 9.2lbs coffee at city (non-fluized). If that's right, my 6x6 RC would need to be about 55in to give it a little cushion. Is that accurate math?
- What kind of btu's, gas flow, would I need at the upper end. I have not used propane for anything besides grilling, so any pointers there are great. I am considering a sievert 2942 burner based on what I've seen in other threads, but have no idea what's best.

The image here is just a concept diagram I put together as I was dreaming. I'll probably do another as I get closer to starting on the actual build.

I'm sure I'll some other questions going forward, but for now, thoughts/advice/warnings?

Thanks!
Brandon attached the following image:
roaster-diagram-draft.png
 
allenb
Brandon wrote:

I still have a couple questions, as I'm working through it.
- Aluminum or SS? I'm not the most skilled metalworker, so aluminum is likely easier, but if stainless is much better, I'll look at it. Will almost certainly use square tubes similar to mustang's build.

- What kind of btu's, gas flow, would I need at the upper end. I have not used propane for anything besides grilling, so any pointers there are great. I am considering a sievert 2942 burner based on what I've seen in other threads, but have no idea what's best.

Thanks!


On btu's for a 4-5 kg fluidbed, from looking over previous builds and charts, I would shoot for around 48,000 btus which is equal to around 14kw if you end up going electric and would give you a little headroom.

On aluminum versus stainless? Aluminum is fine and has no negatives I can think of. Disregard any articles from the past poo pooing aluminum for cooking vessels.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
Want to Help?
By donating you can ensure that HR will continue to be open for years to come. Expenses are 100% transparent and can be viewed publicly at all times. You can find more information on donations and why we request them by reading up on the forum topic here. Thank you.

Brandon
That's helpful. Looks like Aluminum will be the route.

- Based on some math from another thread, it looks like 1 cu ft will hold 42lbs of green or 9.2lbs coffee at city (non-fluized). If that's right, my 6x6 RC would need to be about 55in to give it a little cushion. Is that accurate math?


I did roasted three batches last night (two different origins) to check the expansion, but I didn't get the dramatic shift noted above. Taking all three just through the end of first crack, they were just a hair under double the volume from the starting volume which should give me quite a bit more head room.

Currently looking at this for the blower. Do most use a variac for loft control, or some type of potentiometer?
https://www.grain...tor-32ZN74
 
ChicagoJohn
I use a universal vacuum motor similar to what you cited but 5A, and I use two SCR modules, sometimes called "PWM", one to control the motor and the other the heating coils. I use a 20A variac to maintain line voltage at 120VAC since I see considerable drop at at the 20A outlet I'm using to roast.

Example: https://smile.ama...ed+control
Edited by ChicagoJohn on 10-30-2018 06:07
So many beans; so little time....
 
Brandon
ChicagoJohn wrote:

I use a universal vacuum motor similar to what you cited but 5A, and I use two SCR modules, sometimes called "PWM", one to control the motor and the other the heating coils. I use a 20A variac to maintain line voltage at 120VAC since I see considerable drop at at the 20A outlet I'm using to roast.

Example: https://smile.ama...ed+control


That looks solid. Added it to the list!
 
Brandon
Am I sweating too much on vacuum motors?

Deciding between these two
https://www.grain...tor-32ZN74
https://www.grain...tor-32ZN82

They might both be fine, and I'm just indecisive. From reading the other threads, CFMs don't matter as much if I understand it right. One is 10A, so i'm assuming it's stronger, but looking at the specs, has vacuum (H20 sealed) of 56 but the presumably weaker one has 85. Is this the "inches of water column" I've seen referenced in other places or do I misunderstand how to rate these things?
 
ChicagoJohn
Brandon wrote:

Am I sweating too much on vacuum motors?

Deciding between these two
https://www.grain...tor-32ZN74
https://www.grain...tor-32ZN82

They might both be fine, and I'm just indecisive. From reading the other threads, CFMs don't matter as much if I understand it right. One is 10A, so i'm assuming it's stronger, but looking at the specs, has vacuum (H20 sealed) of 56 but the presumably weaker one has 85. Is this the "inches of water column" I've seen referenced in other places or do I misunderstand how to rate these things?


Sealed suction (static) in inches of water. I've read where AllenB says this is the single most important criterion. I think he said minimum of 10 inches. In my case, I found a used OreckXL handheld canister vacuum at a Goodwill store for $3.95 and used the 5A motor out of that and my 330 gm capacity unit has had over 150 lb through it so far and running well -- with recirc. I have no clue what the sealed suction value is on it. As others have noted, I found that geometry of the inlet to the RC is also a very important determinant of effectiveness.
So many beans; so little time....
 
allenb
Some good info from RoasterRob and should be helpful for figuring out VC motor needs for a 5kg fluidbed.

Link to thread
forum.homeroaster...post_20036

The conical RC works well, i roasted 4kg with it using 1 only 1000watt VC blower and the 7kw sievert burner. I know I can move 6kgs in it using 2 blowers. The reason i went for the conical RC was i tested an 8" asymmetrical RC with 2 blowers and could not get much more than 3kg moving well in it. Also the beans fell back in the middle of the pile not across the other side of the RC. Because of the perceived problems with this RC I kept the perfed area of the conical Rc small - less than 2" dia.
Today i revisited the 8" asymmetrical RC. I redrilled the holes from 3mm to 3.3mm, broke the drill half way thru and finished the last half with a 3.2mm drill bit. Tested it cold with the 2 blower roaster that is almost complete. I had 6 kg of green dancing right up to the edge of the RC. Could probably do 7kg with it except once roasted it would be blowing out the top. Could look at a curved deflector to sort this.
The really good thing about this RC is that by just turning down the dimmer/controller on the VC blower the beans are roasted at a reasonable roast profile.
The height of the bean mass is limited by the airpressurre available and the how the beans behave once roasted. Any more than 2.3kg in my 6" Rc and I have roasted beans bouncing out the top toward the end of the roast, again a deflector at the top would probably mean i could do closer to 3kg. My earlier 6" RC would only do 1.9kg of green because it was shorter.
Problem now with 2 blowers and still only a 6" dia "furnace" section of the roaster is that the extra airflow snuffs the burner out. Something i need to work on


After reading through the thread, I'm thinking you'll need two 1kw vacuum motors to do 5kg to allow some headroom.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
Brandon
allenb wrote:

Some good info from RoasterRob and should be helpful for figuring out VC motor needs for a 5kg fluidbed.

Link to thread
forum.homeroaster...post_20036



After reading through the thread, I'm thinking you'll need two 1kw vacuum motors to do 5kg to allow some headroom.

Allen


This makes sense, now. I read through Rob's thread early in my research, but I didn't really grok the math at the time. I see what he's saying now. I think you're right that I'll need two either way. I'm planning on wiring them in series to balance the load and limit the number of things to control. Is there any reason not to do it that way? The goal for the week is to get the blower box together and get the VCs installed.
 
allenb
I'm planning on wiring them in series to balance the load and limit the number of things to control


If you plan on powering two 120 volt blowers with 220 then series is the way to go and will effectively drop the voltage. Central vacuum systems regularly utilize this method.

If you're feeding two 120 volt blowers with 120 volts then you must wire them in parallel. Series will drop the voltage between the two of them like two resistors in a series circuit do.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
ChicagoJohn
allenb wrote:

I'm planning on wiring them in series to balance the load and limit the number of things to control


If you plan on powering two 120 volt blowers with 220 then series is the way to go and will effectively drop the voltage. Central vacuum systems regularly utilize this method.

If you're feeding two 120 volt blowers with 120 volts then you must wire them in parallel. Series will drop the voltage between the two of them like two resistors in a series circuit do.


Not sure where you're at, Allen, but here in the US our 240VAC is single phase with hots 180° apart from a 240V CT with the center being neutral. These are alternating hot locations in the breaker box. So as an alternative to series couldn't you also then wire each motor with one of the two hot wires using the center as a common return? That way you could run one at 100% and vary speed in the 2nd one for blower control purposes. Just an idea....
So many beans; so little time....
 
ChicagoJohn


After reading through the thread, I'm thinking you'll need two 1kw vacuum motors to do 5kg to allow some headroom.

Allen


I've been thinking about this for a couple of days, and not having an engineering background in this area, a question keeps coming to mind so I thought I'd ask you for some clarification....

If you have a vacuum motor/blower capable of producing a static vacuum / pressure of X within a closed chamber, if you were to introduce a 2nd source of pressure into that chamber, would that source be capable of increasing the pressure therein, or would the extant motor/blower act in reverse to relieve the pressure back down to the maximum it is capable of sustaining? (Within that chamber, of course, lifting the beans off the perf plate is one avenue by which pressure can be relieved, and that is the objective.)

Intuitively I would be inclined to think that static vacuum / pressure limits might act to limit pressure this way in which case I was wondering how two vacuum motor/blowers could be used together to provide more lift for the RC. In analogy with electrical voltage, would you put the two blowers in series with one blower providing the air input to the second one? The reason I'm asking is that in reading the OP's thread it's got me thinking about maybe doing a project like this myself.
Edited by ChicagoJohn on 11-05-2018 00:31
So many beans; so little time....
 
Brandon
ChicagoJohn wrote:



After reading through the thread, I'm thinking you'll need two 1kw vacuum motors to do 5kg to allow some headroom.

Allen


I've been thinking about this for a couple of days, and not having an engineering background in this area, a question keeps coming to mind so I thought I'd ask you for some clarification....

If you have a vacuum motor/blower capable of producing a static vacuum / pressure of X within a closed chamber, if you were to introduce a 2nd source of pressure into that chamber, would that source be capable of increasing the pressure therein, or would the extant motor/blower act in reverse to relieve the pressure back down to the maximum it is capable of sustaining? (Within that chamber, of course, lifting the beans off the perf plate is one avenue by which pressure can be relieved, and that is the objective.)

Intuitively I would be inclined to think that static vacuum / pressure limits might act to limit pressure this way in which case I was wondering how two vacuum motor/blowers could be used together to provide more lift for the RC. In analogy with electrical voltage, would you put the two blowers in series with one blower providing the air input to the second one? The reason I'm asking is that in reading the OP's thread it's got me thinking about maybe doing a project like this myself.


I'd wire them in series, but I would mount them either next to each other or on perpenidicular walls to one another, in the hope that it creates better airflow, but I'm not sure if that matters or not. As I understand it, adding a second blower would be an additive effect, although I suspect there might be some diminishing return in there somewhere.
 
allenb
ChicagoJohn wrote:
Not sure where you're at, Allen, but here in the US our 240VAC is single phase with hots 180° apart from a 240V CT with the center being neutral. These are alternating hot locations in the breaker box. So as an alternative to series couldn't you also then wire each motor with one of the two hot wires using the center as a common return? That way you could run one at 100% and vary speed in the 2nd one for blower control purposes. Just an idea....


Hi John, I'm in US and you're right on domestic 240 being two 120's 180 degrees apart and would do fine as you mention with adding a neutral to split back to two separate 120 circuits but pre-existing 240/208 outlets are without a neutral although it would be easy enough to pull an extra wire. But, this would be somewhat unorthodox code wise unless you ended the circuit with two 120 volt outlets.

The manufacturers of central vac systems drawing more current than could be supplied by a 120 volt circuit chose to use two 120 volt motors in series so they could be fed by typical 240 and 208 two wire plus a ground (no neutral) feeds.

One issue with running the two at different speeds is backdraft through the one running at a lower rpm and lower static pressure. Would not be practical since it would only be cumulative with both at the same speed.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
allenb
Brandon wrote:
I'd wire them in series, but I would mount them either next to each other or on perpenidicular walls to one another, in the hope that it creates better airflow, but I'm not sure if that matters or not.


Something to think about here is you'll be using two 1kw or higher wattage vacuum motors which at full power will be drawing over 18 amps which is more than allowed through a typical domestic 120 volt outlet. So, the only way around this is to A. install your own custom 120 volt outlet with larger wire and an outlet capable of handling this amperage, B. Install an outlet with two hots and a neutral feeding two separate outlets as John mentioned or C. Utilize an existing 240 V outlet with both 120 volt vacuum motors running in series. Option C complicates things since you would have to use a variable power controller capable of working with two hots and a ground. Lots of options.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
Brandon
allenb wrote:

Brandon wrote:
I'd wire them in series, but I would mount them either next to each other or on perpenidicular walls to one another, in the hope that it creates better airflow, but I'm not sure if that matters or not.


Something to think about here is you'll be using two 1kw or higher wattage vacuum motors which at full power will be drawing over 18 amps which is more than allowed through a typical domestic 120 volt outlet. So, the only way around this is to A. install your own custom 120 volt outlet with larger wire and an outlet capable of handling this amperage, B. Install an outlet with two hots and a neutral feeding two separate outlets as John mentioned or C. Utilize an existing 240 V outlet with both 120 volt vacuum motors running in series. Option C complicates things since you would have to use a variable power controller capable of working with two hots and a ground. Lots of options.


My house was wired weird, and it posed some issues with my current roaster Somehow my whole basement and half the main floor ended up on the same breaker. My father in law is a contractor and we ran a larger wire on a 30A breaker, which should have enough clearance to make it work. I still have the old outlets nearby for exhausts and smaller power needs, if necessary.
 
ChicagoJohn

The manufacturers of central vac systems drawing more current than could be supplied by a 120 volt circuit chose to use two 120 volt motors in series so they could be fed by typical 240 and 208 two wire plus a ground (no neutral) feeds.

One issue with running the two at different speeds is backdraft through the one running at a lower rpm and lower static pressure. Would not be practical since it would only be cumulative with both at the same speed.


Thanks, AllenB - makes a lot of sense on the power and balanced operation. But I'm still unclear about how the vacuum motors would be connected to the vacuum chamber. If each one had a sealed suction value of 100 H2O inches, and if you connect them independently, separately to the same sealed chamber, will that chamber then have a sealed suction value of 200 in? If the max delta P sealed suction-to-ambient is 100, do you then connect the blower side of one to the vacuum side of the other one and operate them as a single series system so that the suction maximum is additive?

I'm going to continue to follow Brandon's progress and try a build like he's planning next year. So Thanks Brandon !!
So many beans; so little time....
 
Wiz Kalita
My understanding is that hooking vacuum pumps up to a vacuum chamber and using them to blow air through a roaster are quite different systems. In a sealed chamber, the limiting factor for a vacuum pump is backflow. That is, air will always diffuse back into the chamber, and at some specific pressure the pump can't move air out faster than it goes back in. This determines the ultimate vacuum achievable. Connecting two pumps in parallel to the same chamber will increase your pump rate, but the ultimate vacuum won't improve a lot. Connecting pumps in series can yield higher vacuum, but this depends greatly on the types of pump used.

Most vacuum cleaner pumps are centrifugal fans. They operate at very weak vacuums but with high flow rates. The typical achievable pressure is 20 kPa from ambient, which is 80 inH2O, but the flow rate is of course very large. If it would be more effective to run them in parallel or series in a fluid bed roaster is hard to say, in my opinion. My concern is that if they're connected in series, the secondary fan (closest to the roaster) won't contribute with a whole lot to the air that's already flowing through at high speed, since the motor is designed to run at a specific speed.
 
ChicagoJohn
Wiz Kalita wrote:

My understanding is that hooking vacuum pumps up to a vacuum chamber and using them to blow air through a roaster are quite different systems. In a sealed chamber, the limiting factor for a vacuum pump is backflow. That is, air will always diffuse back into the chamber, and at some specific pressure the pump can't move air out faster than it goes back in. This determines the ultimate vacuum achievable. Connecting two pumps in parallel to the same chamber will increase your pump rate, but the ultimate vacuum won't improve a lot. Connecting pumps in series can yield higher vacuum, but this depends greatly on the types of pump used.

Most vacuum cleaner pumps are centrifugal fans. They operate at very weak vacuums but with high flow rates. The typical achievable pressure is 20 kPa from ambient, which is 80 inH2O, but the flow rate is of course very large. If it would be more effective to run them in parallel or series in a fluid bed roaster is hard to say, in my opinion. My concern is that if they're connected in series, the secondary fan (closest to the roaster) won't contribute with a whole lot to the air that's already flowing through at high speed, since the motor is designed to run at a specific speed.


Thanks for your comments. After a bit more reading online, it seems that connecting vacuum motors in parallel will tend to increase flow rate but not so much sealed suction, whereas connecting them in series will tend to increase sealed suction but not so much flow rate. This makes sense to me thinking about it using a simple electrical model analogy, and it also seems to be consistent with your comments if I'm interpreting them correctly.

However, I am also thinking that when a bean load is present in the RC it represents a resistance to flow through the vacuum motor and can, with the exception of flow through interstitial void volume in the mass, effectively shut down flow just as sealing off the vacuum side would. So I'm wondering if water lift on the vacuum side might not be highly related to "bean lift" on the exhaust side.

In my small system, I observe a couple of phenomena I think could be related to this; one is an initial central, continuous jetting up through the center of the RC where beans are then moving back downward along the outer walls, and the other is a pulsating lift and fall phenomenon that applies to pretty much the entire mass once the bulk density has dropped to about half.

So to increase bean load capacity, then, I'm thinking the idea would be to increase bean lift which may be more related to water lift in sealed suction than it is to maximum CFM of flow rate. And if that is the case, then I would think a series arrangement where the exhaust of one vacuum motor is on the vacuum side of the second motor may be preferable. Obviously it would be helpful to know one way of the other before designing something :)
Edited by ChicagoJohn on 11-06-2018 09:06
So many beans; so little time....
 
Jump to Forum:

Similar Threads

Thread Forum Replies Last Post
KKTO - My Humble Turbo Roaster Turbo Oven Roasters 156 11-11-2018 20:24
6kW Electric Air Roaster Fluidbed Roaster 41 11-07-2018 14:25
Small roaster Fluidbed Roaster 14 10-27-2018 18:25
Electric fluid bed roaster cart build Building a Coffee Roaster 7 10-27-2018 11:08
Mapping a career or business as a roaster COMMUNITY OUTREACH 2 10-14-2018 11:59
Homeroasters Association Logo, and all Content, Images, and Icons © 2005-2016 Homeroasters Association - Logos are the property of their respective owners.
Powered by PHP-Fusion Copyright © 2018 PHP-Fusion Inc
Released as free software without warranties under GNU Affero GPL v3
Designed with by NetriX