seedlings Senior Member Joined: 6 Jun 2007 Posts: 216 Location: Saint Joseph, MO 64506 Expertise: I love coffee
Espresso: Nuova Simonelli Premier V Grinder: Rossi RR45 Drip: Newco Air Pot Roaster: breadmaker / homemade
Posted Mon Aug 11, 2008, 11:01am Subject: Indoor 2lb Electric Roaster - Hypothetical Concept
I'd like to make an indoor roaster, smoke-free enough to avoid alarming the smoke dectors. It will be an air-roaster capable of up to 2lbs, roast, de-chaff, cool, all-in-one unit. At the moment I'm still stuck at the beginning, trying to find a suitable blower that is capable of high inlet temperatures of 400-500F, yet with a high enough pressure to loft the 2lbs of beans (or more would be GREAT). The one blower I have on-hand is a squirrel cage fireplace blower which does not have high enough pressure, so I'm waiting shipment of a used ebay Dayton High Pressure Radial Blade blower. After establishing airflow to loft the beans, salvaged nichrome heat coils from a space heater will provide the heat. Hopefully I have enough backyard fabrication skills to put it all together. The temperature and fan speed will be variable, and with good fortune, a thermocouple or two will give a good bean temp guestimation.
The idea is that the blower will push the air across the heat coils, into a removable roasting chamber, through a sieve screen to filter out the chaff, then the air will re-circulate. As long as there's very little new oxygen (air) introduced during the roast, there should be no smoke. (I know other home roasters with various setups who observe smoke "enter" a roast chamber through a seam in the roaster. Once the seam is sealed, the smoke is pretty much gone.) Recirculating the hot air should provide considerable energy savings, thereby allowing all this to happen on a standard 20 amp 120VAC circuit. The beans will be cooled by killing the heat and then introducing fresh air to allow the blower to cool the beans.
What do you all think of this type of roaster concept?
CoffeeRoastersClub Senior Member Joined: 6 Jul 2005 Posts: 2,144 Location: Vernon Expertise: Professional
Espresso: Vintage La Pavoni Lever... Grinder: KitchenAid Pro Line Burr... Vac Pot: Vintage Silex Drip: Aeropress, French Press Roaster: "EL SUPREMO" w/QuikSPIN-CRC...
Posted Mon Aug 11, 2008, 11:11am Subject: Re: Indoor 2lb Electric Roaster - Hypothetical Concept
Its good to see that you are further exploring your air-roast concepts.
My 2 cents worth on any issues you will have: The cooling cycle. Introducing fresh air at that point of very hot, oxygen starved beans. will most likely cause alot of smoke, possibly fire. Since you are trying to produce an indoor smoke free roaster (I believe you do not intend to pipe exhaust outdoors), that is a major issue you need to address.
seedlings Senior Member Joined: 6 Jun 2007 Posts: 216 Location: Saint Joseph, MO 64506 Expertise: I love coffee
Espresso: Nuova Simonelli Premier V Grinder: Rossi RR45 Drip: Newco Air Pot Roaster: breadmaker / homemade
Posted Mon Aug 11, 2008, 11:40am Subject: Re: Indoor 2lb Electric Roaster - Hypothetical Concept
CoffeeRoastersClub Said:
Its good to see that you are further exploring your air-roast concepts.
My 2 cents worth on any issues you will have: The cooling cycle. Introducing fresh air at that point of very hot, oxygen starved beans. will most likely cause alot of smoke, possibly fire. Since you are trying to produce an indoor smoke free roaster (I believe you do not intend to pipe exhaust outdoors), that is a major issue you need to address.
Ooh, yeah. "Backdraft" style fire is bad. Great point, Len.
I read that the ignition temperature of wood (coffee beans are pretty much wood) is 480F give or take, depending on who's researching. http://www.doctorfire.com/wood_ign.pdf . Killing the heat source (hotter than 482F until the moment it's shut off), internal air temp should start dropping a little, down close to the bean temp. Maybe if the roast is stopped a little short of desired end, then coasts for a little until the air temp starts to drop, then hit it with some fresh air..? This will definitely have to be investigated before I unleash it in the kitchen!
CoffeeRoastersClub Senior Member Joined: 6 Jul 2005 Posts: 2,144 Location: Vernon Expertise: Professional
Espresso: Vintage La Pavoni Lever... Grinder: KitchenAid Pro Line Burr... Vac Pot: Vintage Silex Drip: Aeropress, French Press Roaster: "EL SUPREMO" w/QuikSPIN-CRC...
Posted Mon Aug 11, 2008, 12:13pm Subject: Re: Indoor 2lb Electric Roaster - Hypothetical Concept
seedlings Said:
Ooh, yeah. "Backdraft" style fire is bad. Great point, Len.
I read that the ignition temperature of wood (coffee beans are pretty much wood) is 480F give or take, depending on who's researching. http://www.doctorfire.com/wood_ign.pdf . Killing the heat source (hotter than 482F until the moment it's shut off), internal air temp should start dropping a little, down close to the bean temp. Maybe if the roast is stopped a little short of desired end, then coasts for a little until the air temp starts to drop, then hit it with some fresh air..? This will definitely have to be investigated before I unleash it in the kitchen!
seedlings Senior Member Joined: 6 Jun 2007 Posts: 216 Location: Saint Joseph, MO 64506 Expertise: I love coffee
Espresso: Nuova Simonelli Premier V Grinder: Rossi RR45 Drip: Newco Air Pot Roaster: breadmaker / homemade
Posted Mon Aug 11, 2008, 12:31pm Subject: Re: Indoor 2lb Electric Roaster - Hypothetical Concept
No big deal. Officially it be part of the cooling cycle!
By the way, I have been called on stalling the roast already. I advised someone once to lengthen their popper roast by unplugging the machine for 10 seconds or so periodically. Yep, I was scolded. No one could tell me exactly why besides there are "chemical processes that you don't want to interrupt," which I will be happy to accept at face value. Since then I've been quite conscious of not stalling the roasts. I don't even peek into the breadmaker anymore!
I've oftened wondered if the farmers in Kenya and Ethiopia are concerned about stalling the roast when they have a 3 foot wide pan of beans, manually shaking back and forth over the fire pit and stirring with a 5 foot long stick, without a uber bean cooler nearby. I'd still drink a cup or two! ;)
CoffeeRoastersClub Senior Member Joined: 6 Jul 2005 Posts: 2,144 Location: Vernon Expertise: Professional
Espresso: Vintage La Pavoni Lever... Grinder: KitchenAid Pro Line Burr... Vac Pot: Vintage Silex Drip: Aeropress, French Press Roaster: "EL SUPREMO" w/QuikSPIN-CRC...
Posted Mon Aug 11, 2008, 12:37pm Subject: Re: Indoor 2lb Electric Roaster - Hypothetical Concept
seedlings Said:
No big deal. Officially it be part of the cooling cycle!
By the way, I have been called on stalling the roast already. I advised someone once to lengthen their popper roast by unplugging the machine for 10 seconds or so periodically. Yep, I was scolded. No one could tell me exactly why besides there are "chemical processes that you don't want to interrupt," which I will be happy to accept at face value. Since then I've been quite conscious of not stalling the roasts. I don't even peek into the breadmaker anymore!
Posted Tue Aug 12, 2008, 8:50am Subject: Re: Indoor 2lb Electric Roaster - Hypothetical Concept
With that much bean and thermal mass, you must dump to cool the beans! You have a removable roast chamber already, put a handle on it to dump the beans to a cooling tray. This is important for roast quality.
I don't know anything about the O2 starvation/smoke control, how it works or the effects of 100% re-circ of heated air and smoke, but I think it would be a good idea to include (controllled) fresh air inlet and exhaust of smoke.
Floating 2 lbs of beans does require a big blower. Have you considered some other way to keep the beans moving through a convective heat source? (ie. hot air)
Edit: forgot to add, don't forget to provide a clear, well lit view of the beans as they roast. Maybe a window and light will work.
seedlings Senior Member Joined: 6 Jun 2007 Posts: 216 Location: Saint Joseph, MO 64506 Expertise: I love coffee
Espresso: Nuova Simonelli Premier V Grinder: Rossi RR45 Drip: Newco Air Pot Roaster: breadmaker / homemade
Posted Tue Aug 12, 2008, 12:53pm Subject: Re: Indoor 2lb Electric Roaster - Hypothetical Concept
Frost Said:
With that much bean and thermal mass, you must dump to cool the beans! You have a removable roast chamber already, put a handle on it to dump the beans to a cooling tray. This is important for roast quality.
I don't know anything about the O2 starvation/smoke control, how it works or the effects of 100% re-circ of heated air and smoke, but I think it would be a good idea to include (controllled) fresh air inlet and exhaust of smoke.
Floating 2 lbs of beans does require a big blower. Have you considered some other way to keep the beans moving through a convective heat source? (ie. hot air)
Edit: forgot to add, don't forget to provide a clear, well lit view of the beans as they roast. Maybe a window and light will work.
I don't know much about recirculating either, but I do know that fresh air in, heated and vented outside is much easier. I already built one of those capable of about 1.25 lbs. On that model (pictured by my name), I don't dump the beans for cooling, just shut the heat off and in :30 they're at ambient temp. So, yes, I'm kind of extrapolating out where it may not be wise to do so... but why not give it a try. Sure there are lots of easier ways to move the beans around, like the breadmaker I'm using right now... I just really think this can work well with enough tinkering. At least I hope so.
Viewing the beans is critical for me too, so that is definitely in the works. Most likely by incorporating the Coleman propane lantern glass globe like the last roaster. It works great.
cooncatbob Senior Member Joined: 21 Apr 2008 Posts: 43 Location: California Expertise: I love coffee
Espresso: Gaggia Carezza Grinder: Rocky DL Roaster: I Roast 2
Posted Tue Aug 12, 2008, 1:47pm Subject: Re: Indoor 2lb Electric Roaster - Hypothetical Concept
Sounds like an I-Roast on steroids. You might want to look at the design of the I-roast roasting chamber where the hot air blows the beans up the chimney they circulate to the outside then back down.
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