Roasting coffee beans

Mechanism of coffee roaster

Here, we will try to describe the characteristics of each element of a coffee roaster system.
At the first sight you may find it tricky to understand, specially if you are a beginner. But understanding it, will make you feel even more interested in coffee.
The structure of a roaster may look simple at first sight.
Its structure is not that complicated, the electrical and the gas control certainly is simple. However, roasting coffee beans requires a very well balanced machine structure which is very difficult to achieve.

Heat sources

Pipe burner
FUJIROYAL 1kg roaster uses a gas burner.
Iron pipe bend of 72 holes each 2.3 mm each is opened by hand drill.
This steady work is assigned to fresher of Fuji Royal.

Bunsen burner
Used in large roasters such as FUJIROYAL3 kg, 5 kg, 10 kg.
Its name comes from the German inventor, Mr. Bunsen who has developed a burner where the flame ignites at the top.
The burners used by Fuji Royal are of approximately 1000KCAL each.
Although it is used both in the semi-hot blast and the direct-fired type, periodical cleaning is required for the direct-fired roaster machine since the coffee dust falls on the burner top.

Gun burner "flame projector"
Our lineup of large-scaled roaster of 30 kg uses this kind of burner, in the hot blast roaster.Coffee beans are parched by the hot blast which is generated from the hot blast generator of the rear of the roaster machine.

Charcoal fire
The soft heat of the coal (lower temperature than gas) and the far infrared generated by the charcoal fire roast the beans.
The flavor of the charcoal stick to the coffee, creating a unique coffee taste.

The heat is generated from an infrared device attached to the side of the cylinder from the gas burner in the bottom, results in a full bodied taste.
The heat source is adequate for high quality coffee which deserves special attention although this kind of roaster is rare and has low demand.

Characteristics of a cylinder

FUJI ROYAL coffee roaster works currently with 4 types of cylinder.
It differs according to the taste of coffee, and of course, also depends on how you are going to use the coffee roaster.

Direct-fired cylinder
The cylinder has punching hole drilling, and the coffee beans are heated directly from the flame of the burner from the bottom.
The flavor of the direct flame is passed to the coffee making a aromatic and delicious coffee.
The main source of heat of the roaster is the heat of the burner and flame.

Semi hot blast cylinder
The cylinder is made of a griddle. Punching hole processing is carried out and the backside of a cylinder takes in hot blast from there. Control of the air flow in the cylinder by heat power and the exhaust damper of the burner from the bottom is important.

Semi hot blast dual cylinder
DThis cylinder is made with an extra sheet griddle which is wound around the outside of the griddle of a semi-hot blast cylinder, creating a layer of air between them. It has a mechanism in which green beans cannot be touched at the hot griddle heated by the flame of the burner from the bottom. This type of cylinder has being receiving special attention recently!

Far infrared coated cylinder
This is a direct-flame cylinder with a far infrared coating in its interior.
During the roasting, it irradiates directly the coffee beans with far-infrared rays, even if the cylinder is covered with coffee tar, and can parboil easily to the coffee core with the strong radiant heat.

Exhaust of the roaster machine

The exhaust system is essential to coffee roasting.
This is the first thing that we think about since the start of roaster.

What is the function of the exhaust?
To remove the smoke
The coffee roasting generates a lot of smoke. If there is an abundant smoke in contact with the beans, the coffee become over-smoke scented. As the roasting progresses, you need to open the exhaust damper to take out the smoke efficiently.

To remove the skin of the coffee beans.
The skin of the green beans are peeled off during the roasting. Make sure to remove the skin completely. It affect the taste in a negative way.

To control the convection of the heat of a gas burner.
Coffee roasting is all about "the good balance of temperature change and time"!
If you use a powerful heat to roast the beans in large quantities, it will be completed in short time. If you apply a weak heat to small-quantity, the roasting will not get finished so easily. To know how to control that balance is the key for a good coffee.

Some coffee beans like Blue Mountain and Brazil are soft, some beans from region of high altitude like Guatemala are hard. Coffee beans can be very small-sized species such as Macha, or large grain such as Maragogype and Pacamara. It is also very important to heat the bean very well, but too much heat is not recommended.
Control the heat with the burner and exhaust damper. The flavor depends on how it is heated! Here is the heart of roasting!

Trivia about roaster

What is a gas pressure gauge

Its unit is Pascal (Pa), where 1 Pascal (Pa) is defined as one newton per square meter.
In Fuji Royal, we use 3kpa for natural gas and 5kpa for LPG. Increasing the heat by using a flame regulator, also increases the pressure in it. We can raise the temperature by regulating the heat with a gas pressure gauge, but we cannot lower its temperature.

The structure of insulated coffee roster

Into the frame of a roaster you can find layers of thermal insulation, and its role is to avoid the heat loss from the oven and hold its temperature. It is structure consists in two layers called as first heat insulation and second heat insulation. As the heat gets accumulated inside the oven during the roasting, the heat is transmitted from inside to outside. There is a layer of air in between those two layers. The oven is warmed by the hot blast inside the layer of air at the time of preheating.

What is a cyclone?

Cyclone is something that works like a vacuum cleaner to collect the trash while roasting. IIt is easier to have an idea of what it is if you can visualize a structure of a vacuum cleaner. It is an essential element and installed as a set with the roaster machine.

The function of a cyclone
i1jTo let out the smoke which come out while roasting
i2jTo let out the skin of the coffee bean (chaff) generated while roasting

How a cyclone works
The cyclone is installed in the exit of the exhaust of a machine, connected to the exhaust duct. The blowing-in mouth of a cyclone changes whether it is a left-side or right-side operation. It blows off from a fan by air pressure. The smoke and chaff which came out in the roasting are sent into the cyclone from the main part through a cyclone duct connected to it. The speed of air is reduced since the air comes from a narrow duct to a wider duct, from the main part to a cyclone connection duct. So what is heavier than air goes down in a whril centrifugally inside the cyclone and consecutivelly fall to the chaff repository installed below. Lighter than air goes to the top of the cyclone, mostly of that air is discharged as smoke from the chimney.

Control of roaster motor (reset)

A safety device (thermal) is installed in the motor used in the roaster.
If the motor is overloaded or if an overcurrent is detected during the roasting, it activates the thermal on the operator control panel and forces the motor to stop.
Thermal works with the same principle as the overcurrent circuit breaker at your house and prevents motor burnout by opening the contact of electrical circuit.

Role and influence of a chimney

During the roasting a lot of smoke is generated. That smoke is normally discharged to outdoors through a chimney, connected to a duct of upper part of the cyclone of the machine. Turbulence occurs in the bended part of the chimney. So, it is important to design it as linearly-extended as possible. It is a well known principle that "the length of the lateral should be more than double" , and the gas is updraft as it loses density by the heat. The effect aimed is to cause a chimney effect by non-pressure. The longer is the chimney, you get a higher updraft, and from that principle the exhaust air will go upper. The chimney is also responsible to siphoning off the air (waste gas) accumulated in the cyclone.

Difference between town gas and LPG

i1jWeight (2) Source (3) Price
Town gas
(1) Lighter than air, and if the gas is leaked, it gets accumulated in the ceiling area.
i2jGas is supplied through a tube pulled by each household. The source is the nearest gas company.
i3jPrices are stable.

i1jHeavier than air and it gets accumulated near the floor when there is gas leakage.
i2jConnected to a gas tank installed outdoor. Can be purchased from propane gas company which comes with their supplier car.
i3jPrice varies for each company. Monthly fluctuations in price if the base fee of the gas raises. Prices can be 2 to 3 times more expensive than town gas.

About exhaust damper

Exhaust damper influences the taste of coffee. You can adjust it according to the flavor of your preference no matter the quantity of green beans. It has a very important role in the roasting.
Role of exhaust damper
i1jto adjust the amount of smoke emissions during roasting.
i2jto adjust the emission of heat in the cylinder.

Mechanism of exhaust damper
A lot of smoke is generated during the roasting process. That smoke needs to be ejected constantly, and the device to calibrate the amount of emission of that smoke is called exhaust damper. Exhaust damper is connected to the exhaust pipe, which can also be set manually. The heat source can raise the temperature, but cannot reduced it. With the exhaust damper, it is also possible to adjust the temperature to a lower degree. It is responsible for discharging the gas generated from the beans.

Relationship between the heating power and exhaust
The exhaust and heating power are correlated. If the exhaust power is strengthen up, more smoke and chaff is discharged, and consequently the heat in the oven will be higher. So if the heat is being lost, you need to increase the heating power. If you reduce the exhaust power to low, you can roast with few heat because the temperature of the oven is not easily lost, but the beans will get a smell of smoke.

Benefits of single exhaust

Benefit i1j
To cool the roasted beans, you need to changeover the fan by cooling the changeover damper. Normally because of it, during the refrigeration you cannot roast consecutively but by installing two fans as single exhaust, the work can be performed separately allowing consecutive roasting.

Since you don't need to changeover during the cooling process while roasting, changeover of the damper at the bottom of roaster is also not required. But since another fans is being added, you must have another cyclone.

Difference between iron and aluminum fan
Aluminum fan has 6 leaves, and the iron fan has 8 leaves. The difference between iron and aluminum fan is the quantity of air flow.

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listMechanism of coffee roaster