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Bubblebed roaster based on Nepro wave design
Bhante
for today I'll start just by giving an ultra-brief intro to my plans for building a bubblebed roaster, and will give more details later on as I get the time.

My plans are based on the smaller models made by Nepro, of which there has been some coverage on this site such as in this thread here: https://homeroast...post_19342 and a few other threads.

The main patent, that of Jobst Zoellner 2002 is here: https://patentima...8303B1.pdf

The critical element is the plate itself, which is described in the patent (although there seem to be some trade secrets in the implementation!)

More materials on the Nepro roaster:

https://www.thefr...a068279701

https://web.archi...hneAni.gif

https://web.archi.../nepro.htm

An interesting feature of certain instantiations of this design - in particular the annular design - is a wave motion that spontaneously arises and roatates slowly around the annular roast chamber at about 1 rotation per minute. It has excellent mixing of the beans, with (as I understand) significantly less airflow than a conventional fluidised roaster. The roasting temperatures can be much lower because the heat transfer efficiency is very high. The roast atmosphere is "100% recirculated", which is possible because of the low roast temperatures, and according to Zoellner the atmosphere is oxygen depleted so that aromatic compounds are not burnt. Personally I am inclined to think the roasts could be much more aromatic than other fluid bed roasters because too much aromatic substance would be blown away. It remains to be proven whether the remaining aromatics are spoilt by the prolonged high temperatures, but I'm keeping my fingers crossed that it works.

So, to my plans: 1kg roaster, with 100% recirculation. Annular borosilicate roasting chamber: maybe something like 25cm diameter for the outer cylinder, and 6cm diameter for the inner cylinder. The hot air will pass down through the central cylinder after passing up through the beans, and go back to the fan intake (via a chaff separator). After passing through the fan it goes back up a tube with the heating elements (4 to 5 kW?), then back through the fluidizing plate and into the beans.

When the roast is complete, I extinguish the heater coil and switch the air flow to fresh room temperature air (hope the cool air won't make the roast cylinder crack!). When the beans are cool, dial up the fan to maximum and pneumatic transport the beans out into an external container.

Besides getting the right design for the fluidizing plate, one of the most difficult aspects is going to be the fan, which will be at 200 degrees centigrade or probably more (depending how much the air cools before recirculation). Also as the air gets hotter the pressure of the fan is reduced, so that means extra fan power is required. The fan will be powered by a 220V 3-phase motor and a VFD to control the speed digitally, with the motor driving the fan via a drive belt.

I am currently looking for a test fan, motor and VFD, and will then build a mock-up out of perspex to experiment with the fluid bed design. All that will be just cold obviously.
Edited by Bhante on 09/24/2023 4:26 AM
 
allenb
Wow, very exciting to see this happening! I look forward to progress updates. On the fan issue, most high pressure fans equipped with a heat slinger should do fine at those temperatures.

I noticed the Nepro site has been taken down. You can still get text and some images using the wayback machine but many images are gone now.

https://web.archi.../nepro.htm
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
Bhante

Quote

I noticed the Nepro site has been taken down.


Yes, it seemed to have been removed literally within one or two days of one of my posts about it back in July!!! Someone was obviously watching. The patent has expired now, but someone is maybe using it commercially.

Quote

You can still get text and some images using the wayback machine but many images are gone now.https://web.archi.../nepro.htm


I managed to save virtually everything, but you have to fiddle with dates quite a bit to get some of the components, especially for the shop roaster model.
 
renatoa

Quote

Bhante wrote:
...
The main patent, that of Jobst Zoellner 1975 ...


What is 1975? the patent date is much closer to our days...

Quote

1999-10-27 Application filed by Jobst O. A. Zoellner


Interesting that Typhoon Roaster claims theirs first prototype is 1997, before the patent filling
...
renatoa attached the following image:
image_2023-09-10_102618219.png
 
Bhante

Quote

What is 1975? the patent date is much closer to our days...

...

Interesting that Typhoon Roaster claims theirs first prototype is 1997, before the patent filling
...


Oops! 1975 was garbage, thanks for picking it up! Patent date is 15th January 2002. It claims priority from a 2nd November 1998 filing. I've corrected the posting above accordingly.

There is actually a Neuhaus Neotec patent DE3325967C2 that is referenced by the Zoellner documents dated from 1983, - [EDIT - sorry my earlier edit is wrong on further reading - the Neuhaus is somewhat different people; I haven't read the patent yet], and it could have influenced Typhoon. On the Typhoon itself, the bean movement is quite different from the Nepro roaster and much more like a normal fluidized bed with much higher airflow. Also without seeing the 1997 prototype we don't know what their fluidizing plate was like. It may be that it radically changed once the Zoellner patent lapsed, for all we know - unless someone knows its detailed history. So again, Nepro could have influenced Typhoon there as well. I had a chance to examine a Typhone recently (4 year old 10kg model) but it was on show with no 3-phase current, so I couldn't see the bean movement unfortunately. Personally I think the air stream is far too strong for my taste on the Typhoon. The company where I saw it also dislikes it, claiming it "burns the coffee in 4 minutes" - presumably mostly due to misuse!
Edited by Bhante on 09/10/2023 7:53 AM
 
allenb

Quote

On the Typhoon itself, the bean movement is quite different from the Nepro roaster and much more like a normal fluidized bed with much higher airflow.


I think it's hard to tell from viewing their videos. Some of them look like the bean movement is fairly tame and not chaotic and others seem to show way more airflow than the Nepro versions.

Quote

Personally I think the air stream is far too strong for my taste on the Typhoon. The company where I saw it also dislikes it, claiming it "burns the coffee in 4 minutes" - presumably mostly due to misuse!



Yes, sounds like the user had no clue on how to program a normal roast profile and ended up with an overcooked flash roast.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
Bhante

Quote

allenb wrote:On the fan issue, most high pressure fans equipped with a heat slinger should do fine at those temperatures.
https://web.archi.../nepro.htm


What is a heat slinger?
 
Bhante
Well after much searching I finally found a decent readable (as opposed to the google trash) pdf version of the 1983 Neuhaus Neotec patent - it can be downloaded here:

https://worldwide...&ND=1#

I've only skimmed through it relatively quickly but it is quite interesting. It is definitely a precursor to the Nepro patent, with similar groupings of holes, but apparently does not work as well as the Nepro and is supplemented by a vibrational movement.
 
allenb

Quote

Bhante wrote:

Quote

allenb wrote:On the fan issue, most high pressure fans equipped with a heat slinger should do fine at those temperatures.
https://web.archi.../nepro.htm


What is a heat slinger?


It's a heat sink on the motor shaft between it and the blower wheel

https://www.genai...ing-wheel/
https://www.griev...r-htslng3/
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
Bhante

Quote


It's a heat sink on the motor shaft between it and the blower wheel


OK I understand. For cooling the shaft and bearings not the fan.

https://www.amca....-fans.html
 
allenb
Yes, they do a remarkable job at sinking heat keeping the shaft side motor bearing from dropping out its grease and prematurely failing.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
Bhante
What experiences do people have with borosilicate glass? My plan is currently to use 25cm diameter and 30cm length (or possibly 25cm - significantly cheaper); a possible supplier offered 5mm wall thickness. Any experiences of thermal breakages?

Most people are using smaller diameters (which would be stronger), and note that I also plan to cool in the roast chamber by venting room air through the fan past the previously hot heater element, so the inrush of cooling air should be quite fast.

What wall thicknesses do other people use?
 
progen

Quote

Bhante wrote:

What experiences do people have with borosilicate glass? My plan is currently to use 25cm diameter and 30cm length (or possibly 25cm - significantly cheaper); a possible supplier offered 5mm wall thickness. Any experiences of thermal breakages?

Most people are using smaller diameters (which would be stronger), and note that I also plan to cool in the roast chamber by venting room air through the fan past the previously hot heater element, so the inrush of cooling air should be quite fast.

What wall thicknesses do other people use?


There are of course lots of factors to be considered since you won't be using the same hardware as me but for a 1kg load, you don't need such a large diameter tube. It also depends on the loft pattern that you're looking for. Some people go for more of a spouting type, mine is a more violent Brownian motion kind of thing. Roflmao

Back to topic, I would suggest at max a 20cm diameter tube. Height is up to you because it depends on whether you're going for an open or closed system too. That diameter was close to the prototype hot air roaster I used last year before upgrading to a 3kg capable one. Great roast consistency at that diameter for 1kg loads (raw).

I didn't use borosilicate though. Got a workshop to fabricate a stainless steel cone and cylinder for me which I later brought to another workshop to be welded.

Large diameter borosilicate tubing with thick walls when ordered singly can be more expensive than stainless steel. That's why I went for stainless steel in the end although mine is still an open system so I have an excellent view of the beans.

As for the cooling part, theoretically yes, you can turn off the heater and use the loft blower to cool the beans but it still won't be as fast as a dedicated cooler. Even if you were to only roast one batch, there's still quite a lot of residual heat inside the heating chamber which will take easily over ten minutes to get anywhere near room temperature. Of course the rate of cooling is dependant on the loft blower's power but if you want your beans to drop to room temperature at the speed and rate of a dedicated cooler, you're looking at cranking the loft blower to near max.
 
Bhante
I've just ordered a VFD for controlling the fan speed here: https://www.aliex...21892.html

The nice thing about this device is that it can be user configured to operate either single phase or three phase motors. Both input and output 220V. With a welcome discount from Aliexpress it was only $66 for 2.2kW which is a very good price - and a powerful device. It can be operated via a serial cable from a microprocessor.

So for my cold flow test experiments I have a much wider choice of fans to use (I definitely cannot use the final fan as that is likely to be expensive, so I need to get the power rating right first).

It is a CNWeiKen model WK600D-0022-M1T (manual attached). The WK600 is mainly for high frequency motors up to 600Hz, the WK600D is for normal motors up to about 60Hz.

Well, the attachment didn't work, the webpage claimed it was a "fakepath"!
Edited by Bhante on 09/16/2023 8:43 AM
 
progen
That's more than adequate because I'm only using a 1.5kW one with my 750watt rated regenerative blower and with the frequency knocked up from 50Hz to 75Hz, I can lift 3kg of coffee beans at around 80 - 85% power.
 
Bhante
Thanks that's good to know. However I have to overrate it because of cycling the heat. A blower at 230 degrees centigrade works at much lower efficiency; also the inverter will be in a somewhat warm environment, that's unavoidable. But based on your experience I should have power in hand.

Tell me, what is a "regenerative blower"? These things have different terms in different parts of the world.
 
progen

Quote

Tell me, what is a "regenerative blower"? These things have different terms in different parts of the world.


Some call it a ring blower.

i.ibb.co/S53bT76/HRC900-l.jpg
 
Bhante
Is there any difference to a normal centrifugal blower? What is the diameter?
 
progen

Quote

Bhante wrote:

Is there any difference to a normal centrifugal blower? What is the diameter?


In theory, regenerative blowers are high pressure/ low volume when compared to centrifugal blowers of the same rating. Whether or not that makes them suitable for a hot air roaster depends on your hardware which I believe a knowledgeable engineer should be able to calculate instead of doing what I did which was to guess and just buy. Which is why I have a whole pile of junk and unsuitable parts. 🤣

The theory is, assuming your heater is adequate, a high volume of heated air will transfer more energy (heat) to the beans but at the same time, if your chamber is narrow and your bean bed high, you might want the blower to have the ability to produce enough pressure to break through the beans and get them moving. And it also depends on the pattern you want. A cute spouting bed kind or the violent volcano right in the middle of an eruption kind. Mine is the latter. 🤣
 
Piotrkurak
You don't have a pile of junk, tis but a supply for not imagined projects.

At least that's what I tell my wife the CFO..

OTOH, the other day I went into the parts bin and found the left handed farble I bought for something else and immediately repaired one of her toys.
 
progen

Quote

Piotrkurak wrote:

You don't have a pile of junk, tis but a supply for not imagined projects.

At least that's what I tell my wife the CFO..



But women can be very pragmatic. Whatever you're not going to use right now or latest by next week is junk. 🤣
 
Bhante

Quote

And it also depends on the pattern you want. A cute spouting bed kind or the violent volcano right in the middle of an eruption kind. Mine is the latter. 🤣


Like this (but annular wave motion):

https://web.archi...hneAni.gif
 
Bhante
On heating elements:

Various people have used nichrome wire heating elements wound on a former and mounted inside stainless steel tube. How have people done the supply wiring?

Most of those would have been using cool incoming air, while I am using 100% recirculation at around 230 degrees centigrade or more. Any suggestions for wiring the heater suitable for high temperatures?

Anyone know of suppliers for mica formers for nichrome coils and/or completed coils on mica formers? There are small ones available on Aliexpress for hot air blowers, but they are far too small (up to 2.5cm diameter) and have far too much resistance for the airflow. I found one supplier in Brazil (link from a youtube roaster who said he was planning to use one); I sent an enquiry in English on the website but got no answer.

http://resitermo.... Click on Mica - looks brilliant! (P.S. - Just tried the obvious machine translation!)

I have been thinking in terms of about 4kW to 5kW which is what other people seem to be using for 1kg, though actually as I am recirculating, a lot less surely ought to be more than adequate, like maybe 2kW. For my Hottop 1.4kW is barely adequate for 230g - but with bubble bed the heat transfer is massively more efficient. Somewhere I think I saw some figures for the energy absorbed by the coffee during roasting, which would give a baseline figure - but only if I can find it again!
Edited by Bhante on 09/24/2023 5:22 AM
 
Piotrkurak
Mica standoffs and related high temp ceramic stuff is available via pottery kiln web sites.

Random quick search " https://www.instr...tric-Kiln/"

Not sure how to embed addresses in this forum
Edited by renatoa on 09/24/2023 11:49 AM
 
renatoa
Select the URL, and use the "makes URL clickable " button, the globe with an arrow
Or, surround link in manually typed [url] [ / url] tags
 
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