NXT Coffee Roaster Design not "off the shelf"

To Google Maps
Most coffee roasters are heated by  a natural gas flame.  Natural gas is a cheaper form of energy than electricity but it comes with inherent limitations.  Since the flame requires a continual supply of oxygen it requires a lot of air which must be raised from ambient to combustion temperature, this  is not the end of the energy waste.  The coffee roasting is usually done in the exhaust gasses of the flame which, are not hot enough after passing through the Roasting Chamber, to break down the roasting smoke.  That smell is similar to burnt toast, in the later stages, - imagine several kilo grams of burnt toast.  Hence, an Afterburner is required to raise the temperature to over a 1000°F to break down the smoke.  The large amount of air required by the flame means that a large amount of air must be raised from ambient temperature to over 1000°F.  Consequently, the Afterburner burns, depending on the model,  three times as much energy as the roaster (the equivalence of 6 home furnaces) just so that the neighbourhood will not see nor smell the roaster emissions.  Of course the emissions from such burners are always present but the operators hope that they become sufficiently diluted by the outside air that they will not trigger calls to the environmental agency.  Pollution awareness is upon us and some areas already require permits for coffee roasters with 5 kg or more capacity.

Are there alternatives?
There is, if the fabricator begins with a clean design slate rather than use off the shelf technologies.  First, the amount of air needs to be reduced to greatly reduce the waste of energy.  It is true that often the electricity is generated by the combustion of natural gas but the electrical companies have specialized equipment to remove and neutralize gas volatiles that individual roasters do not use.  Nevertheless, the electrical Roastaire™'s biggest advantage is virtually eliminating the continual feeding of air to the roasting process.  It is possible to recirculate the air with electrical heating because you do not need to feed a flame.  The advantage, is that less energy is required to heat the returning air than to heat room temperature air (ambient) to roasting temperatures.  There is less air to treat when neutralizing the emissions therefore it can be done on a continual basis. A minor advantage is that the oily smoke, as part of the re-circulation process, is burnt which helps to heat the roaster.

Does the design work?

 Below is a photo of the tubing that guides the re-circulated air to the Roasting Chamber.  The roaster was in service for 5 years before this photo was taken.  It had roasted about 30 tonnes of coffee.  It does illustrate why Fresh Cup Roastery Café (Saanichton & Vancouver) clients refer to it as  "Clean Air Roasting"

 Now compare the above photo with one taken of a drum roaster after one year of service.

There wasn't a copyright on the photo but I am not attributing the photo because there is little benefit to kicking a hornet's nest.

In 2010, it is reported that there were 1800 chimney fires, in the USA, that were attributed to coffee roasters.  What heating method do you think was responsible for this incredible statistic?












                                                ------------------------------------------
In the Roastaire the exhaust is passed through a second SmokEater© before it is discharged.  It roasted hundreds of batches inside the Toronto and Vancouver convention centres without the use of a vent or chimney.

What is exhausted?
 Only the air cooling the roasted coffee is exhausted after scrubbing it twice.  More details about the design reasoning will be forthcoming when the topic of Bean Cooling is approached.  In the interim here is some more information on an earlier NXT    blogspot page.

NXT Freshly Roasted Coffee vs Marketing Spin

There are a lot of excuses that are generated by the untimely delivery of coffee.  It appears that more effort is made to make up a fanciful story than to deliver freshly roasted coffee.

It is easier to examine process where companies will pronounce certain rules as if they were laws rather than an opinion or marketing ploy.  Grocery stores have convinced the government agencies that coffee is not a perishable or that its shelf life is greater than 18 months.  Why?  I would say that it fits in with their warehousing distribution model rather than their concern for delivering a fresh product.  The economy brand coffee purveyors notably dance around their weakness which is usually centered on freshness.  Most often there is a clash of goals between their purchasing based on price and their desire to sell at a high end price.  Obviously that is not the message they wish to convey so this is where the marketing dance is conjured.
The question "Is your coffee freshly roasted"?  The typical answers:
- we grind it just before brewing
- we brew on the hour
- we serve our coffee when it is at its prime
- our coffee is ground to a different level
- we have a special relationship with our roaster even if it is 500 miles away
- our roaster uses the best beans
In all cases the question is not answered because it is important to circumvent that limitation by presenting a subjective answer (usually missing the point of the question).  It is a chink in their armour that appears to only be visible to those who are passionate about coffee, inquisitive about the claims, and discriminating purchasers.

On that note, a client must judge if coffee beans must degas for one to 5 days.  The beans will degas regardless because the pressure is sufficient to burst a tightly sealed plastic bag.  I prefer to package ASAP after roasting, letting the beans degas in the bag.  To that end we keep the bags closed, but not sealed, and upright so that the carbon dioxide* (which is more dense and heavier than air) will displace the air by pushing it our the top of the bag.  The client is able to decide when to drink the freshly roasted coffee. We have not found a need for valves.  If the valve is kept as the highest point of the bag the interstitial spaces will also be occupied by carbon dioxide instead of oxygen rich air.

Unfortunately most valves are located around the mid-line which means only half of the bag is purged of oxygen.  To purge the air from the valve equipped bag the bag has to be laid down so that the valve is the highest point in the bag.  Emptying the bag requires the same consideration to preserve the CO2 level, while keeping the bag upright scoop out the beans rather than pouring out the beans along with the CO2.  Pouring the entire bag into the grinder will pour in the CO2 as well but I suspect that the CO2 will drain out the bottom of the hopper, through the burrs, and out of the grinder.  That illustrates a grinder limitation which should be examined in another post.

*  Carbon dioxide is a colorless gas with a density about 60% higher than that of dry air. Carbon dioxide consists of a carbon atom double bonded to two oxygen atoms.  Dry ice is the solid version of CO2.  The wafted vapour that we see above the dry ice exposed to room air is actually moisture from the air that has condensed due to the low temperature near the dry ice.

Experiment With Unintended Consequence

It has been a longtime between updates.  A NXT Roasters search and highly placed search links in Google which are mostly attributable to this blogger or blogspot site tells me that it is a good idea to "feed the beast".  OK, I know, The Filter Bubble has been playing on the car sound system for the past couple weeks which certainly warns about the pervasiveness of Googles' data collection and data sales.  I don't like it but there is no better strategy at hand for the moment.

The original intent was to move the content to   nxtroasters.com   but the great positioning of a search results for "Freshly roasted coffee" Edmonton led me to reconsider.

The insulation experiment was to be a "quick & dirty" evaluation of the insulation value of a potting additive.  A light bulb was buried 25 mm below the surface and switched on.  The curious thing was that the light was getting brighter and brighter.  It did not make sense that the heat of the lamp was melting the insulation so the test continued to gain some conclusive insight.  In addition to observing the tests, measurements were taken with an infrared thermometer.  That was failing miserably because the surface was getting progressively hotter at an increasing rate.

 The test lasted less than 15 minutes giving enough time for wild speculation.  I often find that it is possible to guess most of the forces that will come into play when running an experiment BUT it takes a clairvoyant to rank the influencing laws of physics that are at play in the experiment.

Though I have melted wine bottles in the past this experiment was to be done at a much lower temperature.  The small glass finger broke off from the stresses that were not dissipated during a long cool down period.  The detail was nevertheless quite impressive though, I digress.

The experiment was stopped when the light bulb was obviously close to the surface.  Apparently it had for some reason moved upwards 25 mm.  After the "test bed" cooled down it was time for the autopsy.  Digging out the bulb made it clear that only the top of the bulb had moved and that the experiment was stopped in time, though the light was still functional it would hardly fit in a trouble light cage.

In conclusion the radiated heat of the element and the rising hot gasses is quite high and of course the heated gasses pushed outwards the glass were it was softest.  If the method is used again the voltage will be lowered if it is still possible to find an incandescent lamp.

NXT Fluidized Bed Roaster

AT NXT ROASTERS INC. WE USE THE WORD “INNOVATIVE” AS DISTINCT FROM “IMITATIVE” TO DESCRIBE OUR APPROACH TO DESIGN.

 

The NXT Roaster Design

We selected the fluidized bed technology for our roasting process because it provides even heat distribution, which results in product uniformity. The bean chaff is continually removed from the roasting chamber, eliminating the fire potential. 

To increase roaster efficiency we re-circulate hot air, reducing power consumption by about 75 percent.  To prevent tar deposits on roasted beans (from circulated air), we incorporate a primary afterburner, which burns away the smoke every time the air is reheated.  This arrangement increases the temperature of circulating air, which further reduces overall power consumption.

By circulating hot air in the roaster, we are open to the atmosphere only thirty seconds at the end of the roasting cycle when hot coffee beans are quenched by a blast of cool air, which is vented through our “SmokEater”.  (As an option, we deliver a roasting system that can vent to a room/space.) Loading green beans and unloading of roasted beans is done pneumatically.

The Roasting Process

Roasting requires considerable control of the process to continually achieve a given degree of roast.  In any chemical engineering, operation controls address heat requirements, actual heat balances in roasting, and various heat transfer factors to determine the time required for roasting.   Many of the variables are beyond the control, of the Roast Master but it is possible to tame the process and reliably produce consistent roasts.

The NXT Roaster and its Roasting Process Controls include features that optimize process parameters such that the quality of roasted coffee delivered remains on target and is unaffected by factors beyond one’s control.

Roaster Description

The NXT Fluidized Bed 3 kg Roaster, is now in it's third generation.  The complete system comprises of: process controls, a primary after-burner, a SmokEater, Heating and Roasting Chambers, a chaff removal Cyclone and a pneumatic control system to operate the valves, which automatically load green beans, and transport roasted beans to the Packaging Silo at the end of the roasting process.

 Sequence of Operation

The Roasting Chamber is a cylindrical vessel that has at the chamber’s bottom a Butterfly Valve with Perforated Gate. Air enters the roasting chamber and simultaneously fluidizes and heats, or cools the coffee beans.  When roasting is finished, a blast of ambient air stops the pyrolysis by cooling the beans to below 150º C (320º F). When this temperature is reached, the Butterfly Valve opens and discharges roasted beans through the Poppet Valve and beans are then pneumatically transported to a Packaging Silo.

After-Burner System

The roaster is equipped with a primary after-burner and a secondary “SmokEater”.  The primary after-burner scrubs the hot air of volatiles and tar before these enter the Roasting Chamber.

The “SmokEater” is used at the end of the roasting process to scrub the smoke-laden cooling air from the roasted beans before it is vented to the atmosphere.

Comparing NXT Roaster roasteries with  and Drum Roasters 

		NXT    Roaster		Drum               Roaster
Batch capacity	kg	3		5
Hourly output	kg	18		14.7
Average time per batch	min	10		20
Power consumption with afterburners	kW/hour	6		64.5
Air required for roasting  process	CFM	80		300
Exhaust gas vented per batch	Cubic Feet	40		6000
Exhaust gas vented per hour	Cubic Feet	240		18000
Annual output
Roasting days per year	300	16200		13230
Roasting hours per day	3
Power consumption	kWh	5400		58050
Exhaust gas vented to atmosphere Annually	Cubic Feet	216,000		16,200,000

High Temperature Blower II

                                                High Temp. & High Pressure Blower II

Further to the 2012 post "High Temperature Blower at Work"and 2011 post "High Pressure & High Temperature Industrial Blower"; NXT Roasters has been working on an air bearing package that will deliver the same pressure and volume but at higher temperatures.

High temperatures create a hostile environment especially to an object that must turn at high speeds.  Materials must be carefully chosen so that they will maintain their strength and hardness at the elevated temperatures.  Thermal expansion creates problems as well because not only do different materials expand at different rates but various components operate at different temperatures.  That "constant" X 10^-6 per °C can really bite you.

Common bearings can handle high temperatures and high speeds but rarely can they do both in the same application.  The high speeds (above 10,000 rpm) mean that the components have to be dynamically balanced plus tight tolerances have to be maintained.

The initial goal was to place the Blower in the coffee roasters where it should easily cope with the 250°C recirculated air.  Curiosity drove the project to higher and higher temperatures.  The current temperature ceiling will remain until a stainless steel housing is fabricated.

Earlier this week a blog reader  requested information on a blower capable of moving flue gases.  Unfortunately the 800°C flue gasses are 300° higher than we have been running the Blower, that temperature is beyond the capacity of the 6061 Blower Housing.  

There are some obvious applications for the Blower but it would be interesting to find out if it is able to solve or enhance some industrial processes.  Email your suggestions and requests to main@nxtroasters.com  .  Perhaps our development plans will coincide.

In the meantime we will continue to accumulate operating hours.

NXT Generation III Roaster

 

NXTRoasters Inc. is introducing its third generation advanced roasting system, which protects the purchaser’s investment, consumes the lowest possible energy, and exceed strictest air pollution standards Training time to roast is finished in days instead of months!  Its two-step roasted coffee bean cooling system provides outstanding repeatability of roast degree.

The System combines in a single unit:

• A roasting and a heating chamber,
• A chaff catcher,
• Two afterburners,
• Pneumatic conveyor to load green beans into roasting chamber, and transfer roasted beans to the packaging hopper

The NXT roaster is practically maintenance free, with threat of fire nonexistent!  Chaff from the air stream is separated prior air entering the heating chamber.  Roaster develops no tar deposits.

Specifications:

Batch capacity: 3 kg (green beans)

14.4 kg/Hr (roasted coffee beans)

Motor horsepower:

Main blower:                         2.2 kW

Pneumatic conveyor:             1.5 kW

Temperatures: Adjustable

Roasting: 235°C – 265°C

Heating:

Main heater:                           10 kW

Smoke Eater:                         1.5 kW  

Power consumption:      6.0 kW / Hr.

Including Built-in Afterburners!

Cycle Times: 8 – 12 minutes

Dimensions: 50” x 36” x 80

Improving a Working Device

The picture links were removed because Photobucket decided to change the terms of usage in mid stream, so to say,  It is inconvenient for viewers but it is better to rid yourself of such people as soon as possible.  It is the attitude as much as the action.   We will try to repair that mess at NXTroasters.com

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.

Where to Next or is it NXT ? Suggestions? Freshly Roasted?

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 it is introduced.  I am open to re-examining a blog or even attempting a new topic.  We are also considering a coffee related forum but it should be outside of the crowded topic of sensory and subjective appreciation for the brew.  Our preference is to measure rather than just opine.

Send us an email about a topic.

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.

Improving Roasting Technology

The picture links were removed because Photobucket decided to change the terms of usage in mid stream, so to say,  It is inconvenient for viewers but it is better to rid yourself of such people as soon as possible.  It is the attitude as much as the action.   We will try to repair that mess at NXTroasters.com

 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?

Aeropress - Well Designed & Good Value

NXT Roasters has a Coffee and Aeropress bundle in limited quantities available at our Roastery.

The picture links were removed because Photobucket decided to change the terms of usage in mid stream, so to say,  It is inconvenient for viewers but it is better to rid yourself of such people as soon as possible.  It is the attitude as much as the action.

Freshly Roasted coffee enhances the Aeropress and vis versa.   This brewer does not require an electric brewer which may bring you better coffee since all decent kettles can boil water but not all electric brewers can deliver water at 90°C or higher.

The coffee is Freshly Roasted On-Site in a roaster of our design that has achieved new levels of consistency and pollution controls.  We are very proud of the taste.



 This is the Aeropress package which consists of the brewer and some handy accessories.  The previous blog links to two videos that demonstrate how to prepare coffee with this unit.

We have found that a fine grind enhances the extraction and quite likely gives you a better exercise.  It is difficult to establish if more calories are "burnt off" during the press.

There has been some controversy about paper filters versus perforated stainless steel discs in the domains of tasted and environment.  The stainless steel discs are nearly the price of the entire unit therefore we opted to make the bundle more affordable rather than a high end offer that would cause many to hesitate.

The coffee is less "strong" than an espresso but stronger than drip.  People adjust to their preference by adding water to the final brew and call it an Americano.

There is a challenge for those who appreciate the espresso because the Aeropress cannot be placed on a demi-tasse, well not yet.  Extracting a small volume into a large cup is not satisfactory so we must accept some limits.  However, before discounting the unit try what it does best which is a smaller cup of coffee.

Scoop:

The Scoop contains about 12 grams of coffee depending on how the coffee is scooped and packed.  The preparation of coffee depends more on consistency than an absolute number because other variables often compensate.  Just don't consistently use stale coffee - nothing compensates for that.

Funnel:
Might also be useful in the kitchen but in this case it helps assure that the caffeine deprived person gets most of the coffee grind inside the brewing chamber.

Stirrer:
This is used to be certain that the grind is dispersed in the hot water (remember the key word is hot).  The top has "wings" which prevent the blade from reaching the bottom and tearing the Paper Filter.  Of course this is a moot point when using the Inverted Method.



 Paper Filter:
This is placed inside the Cap to stop the sediment from reaching your cup.  The Paper Filter can be replaced by a stainless steel perforated disc for the people who feel that the paper absorbs essential oils that rightfully should be in their cup.















                          Brewing Chamber et al.:

                       Brewing Chamber                     Plunger                    Filter Cap                    Paper Filter

Inverted style brewing: This is mentioned first because everyone reads the instructions which illustrate the conventional way of using the brewer.

 Place the Plunger inside the Brewing Chamber. 

The internal volume increases approximately 60cc for every number the Plunger is pulled down. Therefore for those without a calculator:
- 60cc X 4 units X .03519 = 8.4 Canadian ounces
- 60cc X 4 units X .03381 = 8.1 US ounces

Unless you know all about compensating for the meniscus let's call it 8 ounces no matter where you live is the maximum capacity.

For a good Plunger seal keep both components vertical.  We cannot accept responsibility for spillage and "accidents" so we count on your diligence in keeping the hole towards the top.

Pour in the ground coffee without resting on the containers. Use one or two Scoops depending on the concentration your body requires.

Add the hot water without resting on the Brewing Chamber.

NOTE:  If there is unsteadiness or it is a challenge to manipulate these devices when they are full of scaldingly hot water you should resort to the conventional method.  Leave this method to the adventurous who thrive on danger.

Mix the water and coffee with the Stirrer to facilitate the extraction.

Place the Filter Paper in the Filter Cap (it will hold better if wet) and screw it to the top of the Brewing Chamber.  Hold the top of the Brewing Chamber.  Just remember the caveats - the liquid is very hot but bliss is now near.

Turn over the Aeropress and place it on a cup (please use a cup that is big enough for the contents). 

Push down on the Plunger.

It should now look something like the photo to the right.

Most people will now drink the coffee before extruding the Coffee Puck which is visible after removing the Filter Cap.

Updating our Roastery

We updated our Roastery and reception area so that it would not be confused with the workshop.



It is slightly more pleasant to sit down at a Granite table for the morning Espresso than a work bench.  Well, there is the optional bar height table for the devotees of the fitness club.

The main goal is to show that our roaster does not require a lot of room.   There is a full glass door that encourages observation though a full glass wall would yield a better view of the Roasting Theatre.

The coffee roaster is the focal point and the "raison d'être".  The green beans are loaded into the counter height Bean Loader Hopper.  the design of which expresses our opinion about overhead bean loading.  After roasting the beans are pneumatically conveyed to the Packaging area which saves the Roast Master from picking up roasted coffee from the floor area.  It appears that drum roaster designers just do not think of ergonomics and Roast Master comfort. These are important considerations when the Roast Master does sessions of over 20 roasts.

The previous post has some pictures of some of our morning Espresso shots.  Not all shots are photographed since pictures are secondary to tasting.  That series of pictures were intended to illustrate the Crema obtained with Freshly Roasted coffee.

The Coffee Roaster is labelled "Roastaire" which is the distributor for NXT Roasters in Canada.  Check out their site for information about roasting, energy conversion efficiency, and roasting pollution controls.

 

Coffee Roasting & Heat Transfer

One of the challenges in attempting a discussion that compares roasting environments is that too many "just know that they are right" without doing any tests or measurements.

An untested concept is, more often than not, nonsense.  Transformation processes require laboratory equipment and technical training to understand.  Some technologies have been around for a long time and have been saddled with claims that just do not stand up to scrutiny.  Drum roasting has many devotees that have been critical of other drum roaster users and other roasting methods. There have been several comments of disbelief about the R. Eggers quotation  from  "Espresso Coffee"  in which he claims that "the typical gas temperature of a drum roaster is 400° - 550°C".  The people contesting this did not measure the air temperature in a drum roaster but "felt" that it was way too high.   Now, I have not measured it either but then, I don't have a drum roaster nor do I advocate for their use.  Some drum roasters use heat exchangers which can be fed with variable volumes of air which consequently alters the air temperature sent to the roasting drum.  Perhaps someone will grace us with the range in temperatures achievable and the slope at which changes can be made.   What they don't have is an efficient way of transferring the energy in the air to the beans.   Without a high pressure blower forcing the hot air through the beans it is only possible to transfer significant heat to the outside layer.  In this situation more energy goes up the chimney than into the beans.

Efficient use of energy can only be attained through recirculation of the roasting air which has to be continually scrubbed of smoke to prevent redepositing on the beans.  Untreated air sent to the chimneys is responsible for many chimney fires.

Updated Hot Air Blower - Canadian Coffee & Tea Show

The High Pressure Hot Air Blower was updated for the Canadian Coffee & Tea Show in Toronto.  The new Insulation package improved the heat retention and made the unit even quieter.  The improved insulation is directly influenced by the desire to improve the conditions in the Roastery.  The direct participation of Roastaire supervisors meant that most of that effort would be directed to reducing both the heat and sound emissions.

Before insulating the Blower we installed improved flexible inlet and outlet connectors to decouple the rotating components from the static parts that could act as "loud speakers".  Again the moving parts were balanced to a high standard, better than G2.5, to "nip the noise source in the bud".  The new flexible connector is less transmissive and has the added advantage of having a smoother and less restrictive bore.

The deadline of the Canadian Coffee & Tea Show meant that there was no time for picture taking.  The fact that we were able to have a "normal" conversation in front of the working blower attests to the effectiveness of the sound containment.  After all, to achieve blower pressures it does have to turn at high speeds.

Containing the heat improves the efficiency of the roaster, reduces the temperature of the other components, and keeps the Roastery cooler.  The Roastaire components are insulated and mostly double walled, unlike most roasters, which greatly enhances the roasting experience.

This does bring about a philosophical design difference with bare bones roaster manufacturers that are promoting low entry prices.  Some show attendees quoted roaster prices that were much lower but the manufacturer omitted to tell the interested parties that an After-burner would be required for roasting in their city and that the After-burner would cost much more than the roaster to buy and to operate.  Neither the coffee nor the client should be "burnt".

The Impeller was also redesigned to improve efficiency and reduce noise generation.  The Impeller must redirect air that is moving axially to a radial flow as gradually and smoothly as possible.  Of course machining a steel Impeller to accomplish this requires many hours in a CNC Mill but if the noise is minimized and the output maximized at the source then the task is easier later on.  Aluminum is certainly cheaper to machine but our small pile of stretched, torn, distorted, and exploded off the shelf aluminum Impellers that could not handle our heat requirements attests to the need of using a steel Impeller at elevated temperatures.

After 1500 hrs Aluminum Rotor self destructs at 250°C

Another Aluminum Rotor tears at 250°C

The picture below was taken before the show opened. More picture are located here.  During the show there were too many interested people to get a clear shot of the roaster.  It was, after all, the only working roaster at the Canadian Coffee & Tea Show in Toronto. 

The Canadian Coffee & Tea Show

Well we are on our way to The Canadian Coffee & Tea Show in Toronto.

The trailer was packed with the Roastaire and the booth earlier in the week.  We expect to be roasting 3 kg batches in the conference hall without a chimney.  We did this at two earlier Canadian Coffee & Tea Shows in Toronto and Vancouver therefore it is not a new experience.  No other roaster appears to have the pollution controls to attempt this.

It will be a rather hectic event with many seminars, presentations, and discussions therefore there will most likely only be a recap after the show.  Perhaps Roastaire will be updating their blog during the event .

TEST TEST TEST - Analyse

An essential element of product development is the testing which establishes the characteristics of the device.  Sometimes the required testing equipment has its own limitations or is too expensive for only limited use.  Tools such as oscilloscopes and DAQ (Digital Acquisition Boards) have many applications and are of great assistance in observing short duration or rare phenomena.  

Simultaneous DAQ boards are nice because they eliminate channel skew but they are more expensive because each channel requires its own A/D converter.  I like Labview but it is frightfully expensive which means it has not been updated for many years.  An additional problem is that the program cannot be downgraded which means if you started with a deluxe-o-matic Suite then the upgrades will approach the cost of purchasing Labview.

It is possible to be creative and resourceful when selecting sensors but often it is a quick and dirty solution that yields the equivalent data.  Non-calibrated equipment can be misleading therefore some reference measurements should be done to develop a "feel" for the measurements.  There is little that is worse than making decisions based on faulty data.

One day I'll be brave enough to look into the new mini computers such as Arduino, Rasberry Pi, etc.  These devices have daughter boards with surprising capacity.  In addition to monitoring the tested device it is possible to also actuate devices.  So far the use of the digital output has only controlled solenoid pneumatic valves and solid state relays.  Not a sign of great imagination!

One handy improvised device was a "Magic Wand" which was essentially a meter stick with a piezzo film bonded card slotted in to the end.  It saved fingers from having mishaps with moving equipment when measuring pump strokes, checking vibrating structures, or simply establishing start/stop time.  An Infrared transmitter/receiver and a 9 Volt battery makes an inexpensive tachometer.  Coils are very handy for measuring current especially when coupled with a data acquisition system.  It is handy to know the start up amperage when testing various rotors and speeds.

The Blower output can be measured in many ways i.e. anemometer, rotameter, venturi but most of them can only be used at relatively low temperatures.  Our high temperature Blower required a metallic venturi which does present some fabrication challenges since the smallest diameter is the furthest from the opening which is not ideal for cutting a smooth wall.

Darn, that was mostly about testing, the analytical part will have to be postponed.

A cup of freshly roasted coffee is a great time saver akin to measure thrice - cut once.