Sunday, June 1, 2014

Improving a Working Device

Unlike a painting a machine can be tuned to new requirements without changing its fundamental reason of being.

An interesting book A Culture of Improvement: Technology and the Western Millennium written by Robert Friedel in 2007, reviews the invention and evolution of many technologies.  He certainly highlights that many factors determine the course of an idea and that it is not always the best idea that dominates.  In school,  history classes often gave the impression that there were technological leaps whereas this informed text demonstrates that more often than not inventors or the mechanically inclined stood on the shoulders of others, so to say.  Often people that leaped too far did not succeed for various reasons; people did not accept such a change, existing materials did not have the required properties, incompatibility  with existing technology, competitors sidetracked "message" etc.  In essence many aspects of a development have to be "done right" to assure success.

It is baffling that the author chooses to dismiss the work of Tesla while he lauds laboratory managers who were often credited with the inventions of employees.  Design of the distribution infrastructure of alternating current is only stated not credited.  Marconi's patent applications were turned down for years because of Tesla's existing patents.  His patent was only granted when well connected wealthy business people employed their power to influence.  It is not too different to where a federal government  concluded that the tomato is a vegetable that is subject to import regulations.

Meanwhile back in the present the challenge is to find an acceptable balance between the best technology and the price of implementing the solution.  To improve the efficiency and greatly reduce pollution the roasting air is recirculated after purging it of nearly all the smoke.  Sounds simple enough but the reality of working in a hostile environment is challenging.  

Fluidizing the bed of coffee beans is essential to the proper mixing and even distribution of heat.  In the upgrade shown on the right the Blower bearings have a lubrication system to improve the Mean Time Before Failure which usually happened too soon at roasting temperatures.

The continual cleaning of the recirculated air means that the roaster does not emit smoke during the hot weather roasting process.  A distinction is made regarding the weather because when it is cooler steam is vented during the bean cooling process.  Such a roaster can be used in higher density areas thanks to the built in pollution controls.

Of course the great smell of coffee is not to be wasted therefore we vent the air used to cool the coffee beans straight to the street to act as an olfactory business sign.

Sunday, February 23, 2014

Where to Next or is it NXT ? Suggestions?

It is time to refresh the blog but the subject matter is not "gelling".  We are working on upgrades but it would be premature to discuss a modification before they are introduced.  I am open to re-examining a blog or even attempting a new topic.  Send us an email about a topic.

Tuesday, November 26, 2013

Improving the Roasting Efficiency.

There are several aspects to be considered before a process can be implemented to improve a design.   Often it is possible to identify, let's say for the sake of discussion, 10 variables that will affect the process.  What is usually impossible to predict is the rank or the level of dominance of each variable unless you are really really really a gifted analyzer or clairvoyant.  Personally I resort to testing a few variables at a time to better understand their effect.  There will undoubtedly be surprises and inconsistencies when various variables are tested together but it is simpler to test in parts than in whole.

The testing results are unlikely to produce a clear graph such are joys of solving problems with multiple unknowns.  The results will give a better idea about the trade-offs that are required before a process can be adopted.  We maintained that coffee beans should be uniformly heated so that the chemical reactions that occur within the beans progress evenly.  It was also deemed important that the beans not be thermally overloaded.  To clarify; the bean has a certain capacity to transmit heat to its interior, if the heat applied is greater than what can be evenly distributed the exterior surface becomes much hotter  and creates a risk of scorching.  It is also for this reason that we roast at a relatively lower temperatures of 240°C to 250°C instead of ...  In "Espresso Coffee" R. Eggers writes the typical gas temperature of a drum roaster is 400° - 550°C.  The high temperature cooking analogy for beans hit by the super hot air is frying eggs while using the stoves highest heat setting.  Yet this fluidized bed roaster has a cycle time of less than 12 minutes versus up to 20 minutes in a drum roaster.   That  is Better Efficiency! 

The even distribution of heat is critical to preparing the beans for the roasting process.  We force heated air between the beans so that they are all heated, not just the outside layer.  There are small domestic roasters that also use air to create a fountain of beans.  It is quite dramatic but if the air flows through a narrow passageway then the remaining beans are not being heated until they gradually make it to the fountain.  Consequently, if you are looking for a home roaster look for one that pushes the air through all the beans.  Typically, the batch will move upwards as the beans are levitated by the flowing air then the air will break through and mix the beans.  The release of air pressure allows them to drop within the chamber but are then suspended again.  The air cushion has the added advantage of keeping the beans off the hot metal which often causes tipping which appear as little pieces of the exterior wall that leave behind a shallow cavity.

It is a simple concept that is regulated by many variables which turn it into a complex process.  

There is more to the efficiency quest than even thermal transfer and the recycling of air mentioned in the previous blog which leaves something to write about later.  Now it is time for an espresso.

Monday, October 21, 2013

Improving Roasting Technology

The conventional approach appears to be - buy a roaster and endure its limitations.  Most conventional roaster owners spend more time developing marketing spin than improving their coffee roaster.   The deficiencies i.e. emissions are already the focus of some legislative bodies which require permits for roasters in their jurisdictions.   Oil burning engines, showing that blue smoke, are rarely seen on the road today yet many owners are complacent about roasting without pollution controls.

The roaster owners who are concerned that large plumes of smoke coming from their chimney are bad for their community image have purchased large gas fired after-burners that burn approximately three times more gas than the roaster itself.  Imagine if automobile pollution controls involved using three times more gasoline than the engine.

Rather than maintain the polluting status quo which may or may not have visible smoke, NXT Roasters Inc., have developed an alternative (branded the Roastaire in Canada) approach that uses the smoke generated as a source of roasting heat rather than expend large amounts of additional energy to thermally neutralize the smoke.   Both 15 Kg/hour concepts thermally treat the pollutants but one system uses a 400,000 to 700,000 BTU after-burner  to accomplish the task.

The first picture is of the main air passageway of a Roastaire after five years of full time roasting.  This revealing photo demonstrates the reason for their motto of "Clean Air Roasting".  This illustrates how efficient and effective the air is scrubbed clean as it is re-circulated during the roasting process.   This closed loop roasting process means that the air only has to be heated 20° to 40°C to return it to the roasting temperature.  Compare that to a single pass air supply that is continually heated from ambient temperature then sent to the chimney.   In "Espresso Coffee" R. Eggers writes the typical gas temperature of a drum roaster is 400° - 550°C.   What a wasteful process.

In comparison,
one drum roasters Maintenance Manual draws attention to the chimney,  "Even if residue build-ups do not exceed 1/8 inch (.3 cm) per year, clean system annually ".    The quotation is not properly cited nor acknowledged but I will do so if the manufacturer requests it.

They also have this picture of a drum roaster fan as a warning about the residue that coats some of their components.  Roast Magazine had the following quotation "It's not IF you're going to have a roaster fire, but WHEN."  Which roaster do you think requires the most maintenance?  Which type of roaster do you think was responsible for nearly 1,800 chimney fires in the USA in 2010?

Which roaster do you think roasted hundreds of pounds of green beans inside the exhibition hall of the last four annual 
Canadian Coffee & Tea Shows?