In the craft beer industry, the most widely used beer fermentation equipment is the cylindrical cone bottom fermenter (conical tank for short). Today, let's talk about the structural characteristics of commercial conical fermenter!
The structure of commercial conical fermenter
(1) With cone base, Angle between 60°~90°, easy to recover yeast after (main) fermentation. In order to ensure the good filterability of beer, yeast strains with good coagulability are mainly used.
(2) Tank body is equipped with cooling jacket, cooling capacity can meet the process cooling requirements. The cylinder part of the tank is provided with 2~3 sections of cooling jacket, the cone part is provided with a section of cooling jacket, this structure is conducive to yeast settlement and preservation.
(3) The conical tank is a closed tank, which can recover CO2 and also be used for CO2 washing; It can be used as fermenter or wine storage tank.
(4) The natural convection of liquor in fermenter is strong. The higher the tank, the stronger the convection. Convective intensity is related to tank shape, capacity and cooling system control.
(5) The conical tank has a considerable height, and the yeast with strong cohesion is easier to precipitate, while the yeast with poor cohesion needs to be separated by other means.
(6) Cone-bottom tanks are not only suitable for fermentation below, but also for fermentation above. In Shandong, many breweries have used commercial conical fermenter to produce wheat beer above fermentation.
Size of commercial conical fermenter
In the past, there were no strict rules on the size of the conical cans, which can be up to 40m tall and more than 10m in diameter. With the continuous improvement of fermentation theory and brewing technology, in order to meet the requirements of beer quality, conical cans must be carefully designed and made in accordance with certain specifications.
Yeast is not only under hydraulic pressure, but also under pressure. If the high concentration of CO2 (concentration gradient phenomenon) is taken into account, the physiological performance of yeast will undoubtedly be greatly affected. In addition, the conical tank height is too large, the fermentation liquid flow is strong, also easy to form stirring fermentation. Therefore, the liquid level in the tank is an important parameter, which not only affects the composition of fermentation by-products, but also affects the activity and physiological metabolism of yeast. Tank height and diameter to height ratio shall be determined according to technological requirements.
The practice has proved that the highest liquid level of wort in commercial conical fermenter is 5m. The height of wort liquid level in conical wine storage tank can be determined according to the actual situation, because the post-ripening process of diacetyl decomposition has been completed, which has little influence on fermentation. There are different views on the diameter-height ratio of conical cans, generally 1:3~1:5 is appropriate.
Requirements for materials and inner wall of conical cans
The conical can is originally made of carbon steel plate, but it is easy to rust, and must be treated with antirust coating. During use, such large tanks should be inspected frequently to prevent the anti-corrosion coating from falling off, and the anti-corrosion coating should be renewed regularly. Nowadays fermenters are made of stainless steel.
The finish of the inside surface of the conical tank is very important. The inner surface should be as smooth and smooth as possible, and no gaps should be examined by microscope. The unsmoothness of a surface is often expressed as "rough depth".
The "rough depth" can be reduced by the correct surface processing method. The rough depth of the surface can reach 0.6~0.8m by rolling treatment. The "rough depth" can reach 0.4~0.5m by polishing treatment. Electronic polishing can achieve a "rough depth" of 0.3~0.4um.
Especially at the bottom of the tank and at the outlet of the material, the "rough depth" must be low to prevent microorganisms from living on the rough surface. This also involves the treatment of welds. Today, the "rough depth" of a polished weld is required to be 0.4~0.5um.
Yeast cells are about 6~10m in size, and yeast cells cannot enter the material treated by the roll. However, the size of bacteria is only 0.7 to 4m, and bacteria can multiply in the rough parts of the tank walls, causing contamination. Therefore, it is extremely important to polish the surface of the tank, which also reduces the working pressure of cleaning and sterilization.
