Fermentation is a crucial process in the production of beer. The beer fermentation system consists of a fermentation tank, a sake tank, and a temporary storage tank. In the craft beer industry, the most commonly used equipment for beer fermentation is the cylindrical-conical bottom fermentation tank, also known as the conical tank. It is a complex biochemical reaction process that involves yeast. Today, ACE engineers will share with you the details of the conical fermenter.
The Composition of Fermentation Tank Equipment
The fermentation system includes fermentation tanks, sake tanks, and yeast expansion equipment. The tank body is made of 304 stainless steel and is sandwiched by a Miller plate. At the bottom, there is an inlet and outlet, while the top is equipped with a double-acting vacuum safety valve, a diaphragm pressure gauge, and a closable sight glass. This equipment allows for easy manual operation and cleaning. It also incorporates fermentation plant technology and equipment manufacturing, enabling automatic and semi-automatic control of the beer fermentation process.
Characteristics of the Conical Tank Fermentation Method
- The bottom of the tank is tapered to facilitate yeast discharge during the production process. This requires strains with good cohesion to ensure good beer filtration.
- The tank body is equipped with a cooling jacket that meets the process’s cooling requirements. This enables easy production control, shortens the fermentation period, reduces the risk of contamination, and maintains stable beer quality.
- The tank body is fitted with a thermal insulation device, allowing outdoor placement, reducing construction costs, saving floor space, and facilitating expansion.
- A closed tank design facilitates CO2 washing and recovery. Fermentation can also be carried out under certain pressures. It can be used as a fermentation tank, a wine storage tank, or a combination of both, known as the one-pot fermentation method.
- The fermentation broth in the tank creates a CO2 gradient or density gradient due to the liquid’s height. By controlling the cooling, natural convection occurs in the fermentation broth, with stronger convection at higher levels. This enhances yeast fermentation capacity, accelerates fermentation speed, and shortens the fermentation period.
- The fermentation tank can be controlled by instruments or microcomputers, making it convenient for operation and management.
- Conical tanks are suitable for both bottom fermentation and top fermentation.
- CIP automatic cleaning devices can be used, offering convenient cleaning options.
- The conical tank is easy to process on-site and demonstrates strong practicality.
- The equipment capacity can be adjusted according to production needs, ranging from 20 to 600m, with a maximum height of 1500m.
Dimensions of Conical Fermenters
In the past, there were no specific regulations regarding the size of conical tanks. The height could reach up to 40m, and the diameter could exceed 10cm. However, with advancements in fermentation theory and winemaking technology, conical tanks must now be designed and manufactured according to certain specifications to meet beer quality requirements.
Yeast is influenced not only by hydraulic pressure but also by air pressure. Concentration CO2, which refers to a concentration gradient, affects the yeast’s physiological performance. If the height of the conical tank is too large, strong convection occurs in the fermentation broth, leading to turbulent fermentation. Therefore, the liquid level’s height in the tank is an important parameter that affects fermentation by-products’ composition, as well as yeast activity and physiological metabolism.
The Working Principle of Conical Tanks and Tank Structure
How Conical Fermentation Tanks Work
The short fermentation period and fast fermentation speed of the conical tank method are due to the hydrodynamic characteristics of the fermentation liquid and modern beer fermentation technology.
After yeast inoculation, the yeast’s cell density at the bottom of the tank increases due to yeast coagulation, resulting in faster fermentation. The amount of carbon dioxide produced during fermentation increases. Simultaneously, due to the static pressure created by the liquid column’s height, the carbon dioxide content changes gradually with the liquid layer’s variation. As a result, the fermentation broth’s density in the tank also presents a gradient change. The cooling device outside the conical tank allows precise temperature control during each fermentation stage. The static pressure difference, the density difference of the fermentation liquid, the release of carbon dioxide, and the temperature difference generated by cooling the upper part of the tank drive strong natural convection in the fermentation liquid. This enhances yeast-fermentation liquid contact, accelerates yeast metabolism, speeds up beer fermentation, and shortens the fermentation cycle.
Additionally, increasing the inoculation temperature, beer main fermentation temperature, diacetyl reduction temperature, and yeast inoculation amount also contribute to accelerating yeast fermentation speed, enabling successful fermentation.
The Basic Structure of the Conical Fermenter
Tank Top Part: The top of the tank features a rounded arch structure. It has a central opening for installing a detachable large-diameter flange, which accommodates CO2 and CIP pipes and their connecting parts. The top is equipped with an anti-vacuum valve, an overpressure valve, a pressure sensor, a washing device, as well as a platform and channel for tank top operation.
Tank Part: The tank body is cylindrical and constitutes the main part of the tank. The fermenter’s height depends on the cylinder’s diameter and height. Generally, the diameter of a conical tank does not exceed 6m due to low-pressure resistance. Processing the tank body is easier than processing the tank top. The outer part of the tank body is reserved for installing cooling devices and thermal insulation layers and positioning temperature and pressure measuring elements. The tank body’s cooling layer takes various forms, such as coiled tubes, Miller pulleys, and jackets divided into 2–3 sections. These sections are connected to the cooling medium inlet pipe via pipes and covered with polyurethane foam or other thermal insulation materials. The thermal insulation layer has an additional aluminum alloy or stainless steel plate, along with a protective layer made of color steel plates.
Conical Bottom Part: The conical bottom typically has an angle of 60º to 80º, although larger angles of 90º to 110º are used for large-capacity fermentation tanks. The cone bottom’s height is related to the angle, with smaller angles resulting in higher cone bottoms. Generally, the cone bottom’s height accounts for about 1/4 of the total height and should not exceed 1/3. The cone bottom’s outer wall includes a cooling layer to cool the yeast that settles at the bottom. It is also equipped with inlet and outlet pipes, valves, sight glasses, temperature and pressure measurement sensing elements. The tank’s diameter-to-height ratio usually ranges from 1:2 to 1:4, and the total height should not exceed 16m to avoid strong convection that could affect yeast sedimentation and coagulation. The tanks can be made of stainless steel or carbon steel. If carbon steel is used, the inner wall must be coated with a non-toxic paint that does not affect beer taste. The fermentation tank’s working pressure depends on its nature and is typically controlled at 0.2 to 0.3 MPa. The tank’s inner wall should be smooth, flat, and polished for stainless steel tanks, while carbon steel tanks should have no concave or protruding surfaces or granules.
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