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Sunday, April 15, 2018

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.  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.

Sunday, April 8, 2018

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.

Monday, October 31, 2016

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.  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, or Roast Master.d

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
















Sunday, November 15, 2015

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";  LEQ (Les Entreprises Quénétic Lée.) 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.  Perhaps our development plans will coincide.

In the meantime we will continue to accumulate operating hours.