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Propane Fluid Bed Roaster Design
jfern
Top  #26 Print Post
Posted on 11/01/2024 9:20 AM
Great design, Allenb! I remember seeing your videos a few years ago and admiring your ingenuity! I just never got up the courage to build my own until now! I have a few questions, if you are open to fielding them. Have you continued to roast on this machine? Have you made any useful design modifications? Were you able to produce consistent roasts within an 8-12 minute window? Also, what would you estimate the distance to be from your flame to the beans, and would there be any benefit to a taller chimney with fins or channels at the outlet to maximize heat flow? Sorry for all the questions! No pressure at all, but if you are open to a brief phone conversation, it could provide an opportunity to address a few rapid fire questions. Thank you for your time!
 
allenb
Top  #27 Print Post
Posted on 11/01/2024 12:15 PM
Thanks for the complement jfern! I sold the roaster to snwcmpr not long after building it but Ken has done lots of roasts on it and never heard any issues with being able to do consistent roasts in that time range.
On distance from flame to beans? Not entirely sure but at least 2 or 3 inches I would guess. But, that design includes a turbulator plate which can be seen in the videos. It's a can lid with slots cut around the perimeter and the tabs tilted into an angle which causes the combustion gases and incoming air from the blower to completely mix in a vortex prior to hitting the bottom of the roast chamber so there is no flame impingement on any part of the roast chamber. I would highly recommend that for your design as it totally removes that potential issue.
Not sure I follow your question on the chimney with adding length and fins to it. Maybe add some verbiage to define better.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
jfern
Top  #28 Print Post
Posted on 11/01/2024 5:08 PM
Thanks for responding, Allenb! To clarify, I wonder if lengthening the chimney and adding segmented channels like rows of square tubing inside the chimney would make heat flow more efficient and prevent the flame from reaching the roast chamber. I've attached another concept below.
jfern attached the following image:
rc4.jpg
 
allenb
Top  #29 Print Post
Posted on 11/02/2024 11:55 AM
All you need is a simple air swirling turbulator out of sheet metal. Very cheap and extremely effective.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
jfern
Top  #30 Print Post
Posted on 11/02/2024 5:37 PM
Okay! Thank you for the direction, Allenb! I will try to scale up and copy your design from your video. Does the shape of the tube matter? My reason for asking is that it's cheaper for me to fold stainless steel sheet into a square chimney as opposed to purchasing 5" diameter 304 tubing. Also, because my burner is 50,000 btus high pressure, should the height of the chimney be significantly higher than yours in the video to prevent too much heat transfer? I appreciate your thoughtful suggestions, and for taking the time to respond to my ramblings.
 
jfern
Top  #31 Print Post
Posted on 11/02/2024 5:58 PM
Square tube turbulator?
jfern attached the following image:
turbulator.jpg
 
allenb
Top  #32 Print Post
Posted on 11/03/2024 8:35 AM
The shape of the enclosure doesn't matter, as you have shown in your drawing will work fine. On height of the enclosure, I would leave at least 8" above the burner before the turbulator plate to give it enough space to form proper combustion. Then, another 4" above the turbulator plate prior to hitting the inlet of the RC for proper mixing.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
jfern
Top  #33 Print Post
Posted on 11/03/2024 3:04 PM
Thank you, Allenb! This gives me some practical specs to work with! Do you think there is any advantage to including heat exchange tubes in the compartment between the turbulator and the RC inlet?
jfern attached the following image:
chimney_with_turbulator.jpg
 
allenb
Top  #34 Print Post
Posted on 11/03/2024 3:22 PM
A heat exchanger would not add any positive function to the roaster so no, not needed. Can you describe what you believe it would accomplish?
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
jfern
Top  #35 Print Post
Posted on 11/03/2024 4:34 PM
I thought I'd cover all my bases in regards to channeling heated air into the roast chamber without any possibility of the flame interacting with the beans. The assumption was that more metal in the hot air stream would increase thermal mass and heat exchange before entering the RC. I may not be understanding these concepts as well as I think though!
 
allenb
Top  #36 Print Post
Posted on 11/03/2024 5:45 PM
Ok, I follow you now but no, that will not serve any useful function since the combustion gasses (flame products) and incoming air from the blower will be thoroughly mixed when leaving the swirl plate (turbulator) well before entering the roast chamber perf plate.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
jfern
Top  #37 Print Post
Posted on 11/03/2024 7:14 PM
Thank you for the clarification, Allenb! I appreciate your time and expertise! Hope to get started with fabrication soon.
 
jfern
Top  #38 Print Post
Posted on 11/06/2024 7:29 PM
Hi Allenb, would you mind giving some feedback on this turbulator disc design. It's 4 1/2" in diameter with 16 fins, fabricated from 20 gauge stainless sheet. Thanks!
jfern attached the following image:
turbulator_1.jpg
Edited by jfern on 11/06/2024 7:48 PM
 
allenb
Top  #39 Print Post
Posted on 11/07/2024 11:05 AM
That should work nicely. But make sure you have at least a 30 degree tilt angle but no need to go more than 45 degrees to ensure you have a good % of open area. I'm assuming from the image that your turbulator tabs are around 1/2" long if measuring from outside circumference inward toward center hole? This would give you somewhere around 6 square inches of open area give or take a bit which would be plenty with no impedence to air flow when using a vacuum blower for air delivery.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
jfern
Top  #40 Print Post
Posted on 11/07/2024 12:44 PM
Thank you for putting eyes on this for me, Allenb! The tabs are roughly 1/2" long, but not sure of the angle tilt. I will go back and verify they are within the range you mentioned. On a side note, your centrifugal turbo roaster on youtube is brilliant!
 
progen
Top  #41 Print Post
Posted on 11/07/2024 2:21 PM
i.ibb.co/NVZTc8d/my-11134201-23020-d97brncgfknvaa.jpg

Has anyone tried to use one or two of these in a plenum as a gas powered heat source?
 
jfern
Top  #42 Print Post
Posted on 11/07/2024 8:25 PM
I seriously considered an infrared burner for my project. I like that it doesn't produce a traditional flame and supposedly reduces the risk of carbon monoxide. It also seems to produce more variable heat than a conventional burner which would give better control over the roast. However, I was unsure whether it would tolerate the high pressure of a vacuum blower, or if it would transfer heat to the air efficiently.
 
progen
Top  #43 Print Post
Posted on 11/07/2024 11:00 PM
I was wondering wherein it's possible to run two facing each other with the air coming in between and the burners on somewhat high pressure. The bean retaining / air straightening plate will provide some resistance to aid in mixing before entering the roast chamber.

i.ibb.co/c21sDCZ/my-11134207-23010-cz0s8tfnwemv62.jpg

Another possible alternative would be an angled high pressure LPG burner (the one on the right) with a stainless steel domed plate a few inches above and the air coming through that hole in the burner. The air will hit the bottom of the dome and the turbulence should help in mixing.
 
allenb
Top  #44 Print Post
Posted on 11/08/2024 9:35 AM

Quote

jfern wrote:

Thank you for putting eyes on this for me, Allenb! The tabs are roughly 1/2" long, but not sure of the angle tilt. I will go back and verify they are within the range you mentioned. On a side note, your centrifugal turbo roaster on youtube is brilliant!


You're welcome and thanks for the compliment on the centrifugal roaster! I have to admit that I got the idea from seeing the Probat huge bowl type centrifugal and just made it flat and added a couple of return vanes. One problem with this kind of agitation regimen is noise! Unless one is prepared to fully insulate the sidewalls of the enclosure, it makes hearing first crack/2nd crack impossible unfortunately.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
jfern
Top  #45 Print Post
Posted on 11/27/2024 10:03 PM
Just thought I would post an update on my project. It's turning out to be more time intensive than I imagined, but I am enjoying the process. I completed fabrication of the combustion chamber including a turbulator disc as recommended by allenb. It is constructed out of 18 and 16 gauge stainless steel sheet held together with 308 stainless plug welds and stainless M8 bolts. It's not the prettiest thing, but seems sturdy enough! The next challenges will be designing the vacuum blower plenum, propane burner mount, and making sure everything is airtight. Please offer any direction, criticisms, or encouragement you have. Happy Thanksgiving!
jfern attached the following images:
4_20.jpg combustion_2.jpg turbulator_2.jpg
 
jfern
Top  #46 Print Post
Posted on 11/27/2024 10:10 PM
Additional images.
jfern attached the following images:
5_11.jpg 6_15.jpg
Edited by jfern on 11/27/2024 10:17 PM
 
jfern
Top  #47 Print Post
Posted on 12/07/2024 3:05 PM
I hope everyone is staying well and out of he cold! As I continue working on concepts for my blower plenum and burner box, I was hoping someone with engineering expertise could give me feedback on the concepts in the attached image. Do any of these designs seem optimal for a fluid bed roaster. I recognize that some designs will present more challenges than others in terms of sealing and insulation. Thanks!
jfern attached the following image:
roaster_design.jpg
 
allenb
Top  #48 Print Post
Posted on 12/08/2024 12:43 PM
Here's some tips that I learned from previous builds. In order to avoid heat losses, utilize a round sheet metal sleeve around the portion of the burner head where combustion takes place. The sleeve diameter needs to be larger than the diameter of the burner head to allow at least a 1" gap between the exterior rim of the burner and the sleeve all the way around. The roaster enclosure, in your case, needs to be big enough in diameter to allow another 1" gap outside of the sleeve. Make the sleeve tall enough to reach the turbulator. What this does is allow any heat losses from the burner combustion path to transfer to the air within the roaster enslosure via the sleeve and almost no heat loss transferring out through the actual roaster enclosure.

This will require you to make the portion of the enclosure from the burner head up to the turbulator much bigger in diameter or in square cross section. You don't want a small gap (bottleneck) around the burner head where the incoming air from the blower whizzes by the outside diameter of the burner head as this will create turbulence at the rim of the burner.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
jfern
Top  #49 Print Post
Posted on 12/08/2024 3:55 PM
Thanks for responding, allenb! I built the burner column just large enough to leave 1/2" clearance around the circumference of the burner head to the inside perimeter of the column. It's possible I could install a deflector around part of the burner, but it would be a tight fit. Do you think there is any other way to navigate this challenge without buying a different burner or scrapping the burner column? The image below includes a semi-cylinder around the burner at the point where the air enters the column. Thanks for your time and advice!
jfern attached the following image:
burner_column.jpg
 
wbbh
Top  #50 Print Post
Posted on 12/09/2024 6:50 AM

Quote

jfern wrote:

Thanks for responding, allenb! I built the burner column just large enough to leave 1/2" clearance around the circumference of the burner head to the inside perimeter of the column. It's possible I could install a deflector around part of the burner, but it would be a tight fit. Do you think there is any other way to navigate this challenge without buying a different burner or scrapping the burner column? The image below includes a semi-cylinder around the burner at the point where the air enters the column. Thanks for your time and advice!


I like example 2 or 3 above, the example here looks like it will not allow an adequate flow of air to the intake port on the burner. The burner is designed to work in atmospheric pressure, so the entire burner needs to see the same pressure from your blower.. With increased air pressure, more gas can be consumed efficiently.
 
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