Conceptual Drawing of the Roaster #1

2010 May 7
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There comes a time when your hand wants to draw. The mind is full of ideas that must be put on paper — ideas that need to be expressed for others to examine and comment on, ideas that once on paper allow the mind to focus on details. Today, my hand wanted to draw my current best thinking on how the core of the roaster will work. So…

A Conceptual Drawing of the Roaster based upon a Bowl as the Roast Vessel (5/7/10 4p)

As you can see I have a fixation on the sphere as a design element. This comes from a couple of sources. First, I like a very clean design and the sphere meshes well with the bowl as the internal element … not a lot of wasted housing space. Secondly, I have a love affair with Atomium in Brussels … I think it is one of the coolest modern structures I’ve ever experienced.

The Atomium built for the 1958 Brussels World's Fair . Designed by André Waterkeyn

As for the inner workings of the roaster, I would like to explain. The heart of the roaster is a spinning bowl. The bowl spins the beans outward, via centrifugal force and up the lip. The lip of the bowl directs the bean back into the center to begin the whole process again. The beans are both spinning and flowing in a donut pattern as shown by the arrows. This is essentially a mechanically induced fluidized bed of coffee beans.

As for heating the beans, a jet from above blows down into the center of the bowl and through the cascading beans. This heats them via convection. As the jet hits the center of the bowl, there is a diverter cone that spreads the airflow out over the bowl. The exhaust air, including smoke and chaff are sucked back up into the exhaust plenum at the top of the spherical housing and vented out. The hot air of the jet heats the beans and the bowl. In addition, there are ribbon burners under the bowl to add heat directly to the bowl for conductive heat transfer, if desired, and to pre-heat the bowl. An infrared burner array is also in the top of the sphere to offer radiant heat, as needed.

For cooling, the diverter cone pops up and the beans fall through the hole in the bottom of the bowl, now exposed by the lifted cone. The beans flow into a manifold and out of the roasting sphere into the cooling vessel (which may very well be a sphere).

The upper portion of the roasting sphere includes a window, so that the operator and guests can clearly watch the roasting operation. There would also be a “trier” (not shown) for the purpose of pulling samples of the beans while roasting. This enables the roastmaster to make an evaluation of bean color, development, and aroma.

This drawing is the starting point for many more refinement sketches and discussions. My hand is happy that it has been allowed to express itself and my mind is at ease.

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2 Responses
  1. Mark permalink
    May 12, 2010

    Cool stuff. Speaking of cooling, that could be a huge part of what is wrong with today’s roasters. The roast master goes to all the trouble of creating a perfect roast, but if cooling is not happening quickly enough, then the beans are still changing even after the roast is supposed to be over.

    Just a thought.

    • May 12, 2010

      I agree, Mark. I will be working on the conceptual design of the cooling system shortly. While it is often considered bad practice, I would like to investigate the use of conservative water quench to speed the cooling process without being absorbed by the beans.

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