Generation 2 went through several iterations. It did away with the sliding Roasting Chamber and overhead Loading Hopper. The counter top roaster, again with an outboard SmokEater™ had pneumatically controlled valves which were able to route the air so that green beans could be loaded from a counter height Loading Hopper. The re-circulated pressurized air is able to transfer more heat evenly to the beans than the high temperature (often twice the temperature)- low pressure circulated air used in drum roasters because in the fluidized bed all the air goes through the beans without having a portion of the flow simply going around the beans. This model also introduced the second generation of the Roasting Monitor.
The function of the NXT Roaster is responsible for the form it was given. In brief, recirculation requires the shape of an "O" which is formed by the two larger columns tied together by the base and top pipes. The left most small rear column is the Cyclone which removes the chaff from the circulating air while the right most rear column is the SmokEater™which does the final air cleaning or smoke neutralizing before exhausting the air during the Cool Mode.
Shown above is the third generation 3 kg Roastaire™ that roasted on the exhibition floor at both the Toronto and the Vancouver Canadian Coffee & Tea Shows. No chimney was used for the 110 batches of green beans roasted. It was the only roaster that Roasted On-Site and inside the hall. This version was a "complete re-think" of the functions and the layout of the coffee roaster. It required the development of a High Temperature Blower capable of fluidizing the green beans, a new computer based Roasting Monitor, PID Temperature Controllers, two Pneumatic Bean Conveyors, initial bean cooling within the Roasting Chamber, and a Packaging Silo to further cool the roasted coffee beans. The SmokEater™ was incorporated into the Roaster body so that the entire unit could be moved on casters and occupy a relatively small footprint.
The goal was to make the industrial roaster compatible with an urban environment, without requiring optional add-ons, yet be as compact as possible. To improve the efficiency well above that of a gas burning roaster the air was recirculated. The post "Roaster Pollution Reduction" shows photographic results, after 5 years of cafe roasting, that the air was cleaned before it was re-circulated to the Roasting Chamber. This compares very well with the caked exhausts, of other roasters, shown by KaladiCoffee on Youtube.com . It was not an overnight success but it works well. The High Temperature Blower required a great deal of development since off the shelf blowers do not survive such temperatures for very long even with high priced precision bearings. The pressure and flow is required to fluidize the beans which is among the most efficient ways to evenly transfer the heat to the beans. The wasteful solution has been to move cold air which is then passed through the Heating Element. Air is continually heated from ambient to roasting temperature. The wasted energy is augmented when the Pollution Controls are implemented. The NXT Roaster only exhausts air for 75 seconds of the 10 to 12 minute roasting cycle, During this phase the air is further cleaned, as shown in another photo in the already mentioned post.
The Computer based Roasting Monitor makes it possible for the Roastmaster to monitor the pyrolytic process to consistently and repeatedly attain the required degree of roast. There will be another post along with annotated pictures of the program's screen view in a further post or maybe posts. The Roasting Monitor clearly shows the the pyrolytic reaction is stopped within seconds, minimizing the roasting overshoot which allows the Roastmaster to "call the roast" for its degree rather than for what it will be in 60 to 90 seconds. Which is the time some units take to dump the beans, fill the bottom of the Cooling Tray, then turn on the Cooling Fan.
The PID ( Proportional Integral Derivative ) Temperature Controllers do not click Off/On as the temperature passes through the set point but rather the algorithms analyze the rate of temperature change to anticipate, with accuracy, reaching the temperature set point.
The Loading Pneumatic Conveyor allows the Roastmaster to fill the counter height Loading Hopper with 3 kg of green beans rather than the too common overhead hopper. The Green Bean loading takes place at the same time as the roasted coffee beans are conveyed to the Packaging Silo then cooled for several minutes. Typically this silo is positioned in the packaging area above the counter, shown in a photo from the Canadian Coffee & Tea Show booth.
Fresh Cup Roastery Café booth (well, half of the booth)
There is no visible exhaust to show how effectively the Pollution Control System is. We have reached the level of requiring sniffers and gas analyzers. The electric elements obviously do not create combustion gases which, in gas fired drum roasters, are circulated through the coffee before flowing to the chimney. Afterburners, for gas fired drum roasters, with a comparable output to the Roastaire™ range from 400,000 btu to 1 million btu which significantly increases the energy costs of each pound roasted. Such a waste. Perhaps an operational cost comparison blog is in the offing.
