Posted by oldgearhead on 03/25/2014 9:13 AM
#9
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vahegan wrote:
Thank you, oldgearhead
Can you please explain what do you mean by being aggressive between Mayard phase and the first crack? Do you mean higher temperature or faster change of temperature?
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However, the drying phase is somewhat dependent on the ambient temperature and if you use a 'warm up' or not.
Again, not quite clear to me what do you mean? Since I am using a temperature controller, the drying phase temperature does not depend on the ambient, after the initial overshoot, its stable. I think only the steepness of the heating cure somewhat depends on the ambient temp.
As for the blower speed - yes, I can control it, but a two-variable PID is rather complicated and I am not quite good at PID tuning, therefore I leave it constant for the time being.
Again excellent job!
First let me say I use no automation on my coffee roaster. However, when I see a super job like yours, I am tempted to take the old A/B SLC504 off the shelf and start in.
I'll start by discussing two of the critical fluid-bed coffee roaster temperatures: Bean Mass Temperature (BMT) and Process Variable Temperature (PVT). BMT is the temperature of the beans and the hot air that keeps them moving. PVT is the temperature of the hot air that enters the RC (roasting chamber). If no change is made in blower pressure during the roast as the beans get lighter the BMT probe will be influenced more by the PVT than the BT (bean temp). For two years I always adjusted the PVT during each roast, but recently I have just set a constant PVT temperature, and adjusted the blower pressure about four times during the roast to control the BMT.
Answers:
1) "More aggressive' - I mean a quicker RoR (rate of rise of the PVT).
2) 'Ambient temperature' - My roaster lives in an unheated garage in Central Indiana. When the garage is 50F I use no warm-up or reclaim air baffles. But when its 17?F I must use the baffles plus a warm-up to have the same roast time for the same bean.
One more tip - Try to cool your beans faster with an external cooler.
Great job! Great job!
Edited by oldgearhead on 03/25/2014 9:20 AM