Beer fermentor

Structural characteristics of beer fermentation tanks
Taking the mechanical stirring ventilation tank as an example.
Mechanical stirring and ventilation fermentation tanks are widely used in biotechnology factories. According to incomplete statistics, they account for 70% to 80% of the total number of fermentation tanks, so they are often referred to as universal fermentation tanks. These types of fermentation tanks are mostly used for ventilated fermentation, relying on compressed air and stirring impellers to achieve mixing and dissolved oxygen mass transfer of the fermentation broth, while enhancing heat transfer. The main components of a universal mechanical stirring and ventilation fermentation tank include the tank body, stirrer, baffle, shaft seal, air distributor, transmission device, cooling pipe (or jacket), defoamer, etc.
The main components of this type of fermentation tank are explained below.
1、 Tank body
The tank body is composed of a tank body, a tank top, and a tank bottom. The tank body is generally cylindrical, while the top and bottom of medium and large fermentation tanks are often connected to the tank body by elliptical or disc-shaped heads through welding. The bottom of small fermentation tanks is also generally connected to the tank body by elliptical or disc-shaped heads through welding, while the tank top is often connected to the tank body by flat caps and flanges. For easy cleaning, the top of the small fermentation tank is equipped with a hand hole for cleaning. Medium and large fermentation tanks are equipped with quick opening manholes. The top of the tank is equipped with sight glasses and light mirrors, feeding pipes, replenishment pipes, exhaust pipes, inoculation pipes, and pressure gauge connections. The exhaust pipe should be located as close as possible to the center of the tank top. There are cooling water inlet and outlet pipes, air inlet pipes, thermometer pipes, and detection instrument interfaces on the tank body. The sampling tube can be installed on the side or top of the tank, depending on the convenience of operation.
Stainless steel is commonly used for various parts of the tank body. To meet the process requirements, the tank must be able to withstand the working pressure and temperature during fermentation and sterilization. The thickness of the tank wall depends on the tank diameter, material, and pressure tolerance.
2、 Blender and baffle
The main functions of a stirrer involve gas dispersion, solid-liquid suspension, heat transfer, and mixing. Even if the air introduced is dispersed into bubbles and fully mixed with the fermentation broth, the bubbles are finely divided to increase the gas-liquid interface, obtain the required dissolved oxygen rate, and suspend and disperse biological cells in the fermentation system to maintain appropriate gas-liquid solid (cell) three-phase mixing and mass transfer, while enhancing the heat transfer process. To achieve these objectives, the design of the mixer should ensure sufficient radial flow and moderate axial movement of the fermentation broth. The agitators used in fermentation tanks mainly include radial flow agitators, axial flow agitators, and combination agitators.
3、 Defoamer
The fermentation broth contains a large amount of protein and other foaming substances, which will produce a large amount of foam under strong aeration and stirring, and a large amount of foam will lead to the overflow of the fermentation broth and increase the chance of infection. In addition to adding defoamer, mechanical defoamer can be used to crush foam when the amount of foam is small.
4、 Couplings and bearings
When the mixing shaft is long, it is often divided into 2-3 sections and connected with a coupling. There are two types of couplings: drum shaped and clamp shell shaped. The stirring shaft of a low-power fermentation tank can be connected with a flange, and the shaft connection should be vertical with the centerline aligned. In order to reduce vibration, adjustable intermediate bearings should be installed, made of asbestos phenolic plastic and polytetrafluoroethylene. The gap between the bearing shell and the shaft should be taken as 0.4% to 0.7% of the shaft diameter. Adding a shaft sleeve on the shaft can prevent the journal from being worn. 5、 Variable speed device
The test tank adopts a continuously variable transmission device. The commonly used variable speed devices for fermentation tanks include V-belt transmission, cylindrical or spiral bevel gear reduction devices, among which V-belt variable speed transmission is relatively simple and has less noise.
6、 Air distribution device
The fermentation tank distribution device is a device that introduces sterile air into the fermentation broth. It usually has two structures. For small fermentation tanks with low ventilation ratios, choosing a single inlet pipe can better distribute the air; However, for large fermentation tanks with high ventilation ratios, priority should be given to using circular distribution pipes with large holes. This is not only beneficial for increasing the gas-liquid specific surface area, but also for the overall distribution of air after entering the tank, and for the bottom agitator to crush bubbles.
7、 Shaft seal
The function of the shaft seal is to prevent bacterial contamination and leakage.
8、 Heat exchange device
During the fermentation process, the heat generated by biological oxidation must be immediately removed to ensure that fermentation proceeds at a constant temperature.
Cleaning and sterilization of beer fermentation tanks
1、 CIP parameters
1. Types and functions of cleaning agents
The cleaning agents used for fermentation tanks are water, alkaline solution, acidic detergent, bactericide, and sterile water. Water is the most commonly used cleaning agent, which is a highly polar inorganic liquid molecule. Inorganic and organic substances with strong polarity are generally easy to dissolve in water (alkaline solution can eliminate yeast on tank walls and pipelines, effectively remove proteins, hop resins and other dirt). Acidic detergents have good dissolution and washing effects on inorganic salt precipitates, tannins, hop resins, proteins, etc. in beer. Fungicides can kill bacteria and other microorganisms.
2. Surface tension of various liquids
The cleaning of fermentation tanks adopts the cleaning method of spraying from the top of the tank. Pressure cleaning solution is sprayed out through a nozzle to impact the surface of the tank top, and then a uniform downward flow of cleaning liquid film is formed, generating friction and achieving the cleaning effect. But if the dirt is tightly bound, it will be difficult for the detergent to penetrate into the dirt due to its high surface tension.
It can only work on dirty surfaces. The surface tension of water and alkaline solution is higher than that of beer, and the traditional alkaline washing process only heats the washing solution to clean the fermentation tank, resulting in poor washing effect. At present, breweries usually reduce the surface tension of detergent by adding some detergents to achieve the goal of removing tank wall dirt.
3. CIP process
The basic process of traditional CIP cleaning is CO2 evacuation, pre rinsing with water, alkaline washing, rinsing with water, acid washing, rinsing with water, sterilizing solution, and sterile water. Its advantages are good cleaning effect, low cost, and low equipment requirements. But for existence Yao's fermentation tank undergoes alkaline washing. Before cleaning, the%/* inside the tank needs to be emptied, causing time waste and oxygen ingress. Nowadays, many breweries have improved the traditional%&∆ process by adding some additives containing surface active ingredients to the alkaline solution to enhance the washing effect, saving%&∆ cleaning time and improving equipment utilization.
The acid washing process is an alternative method to traditional alkali washing. The acid washing process uses acidic detergents to clean under CO2 pressure, which can reduce the operation time of CIP cleaning, save CO2, and avoid oxygen intake. Moreover, the concentration of acidic detergents in the acid washing process is lower than that of the alkaline washing solution, which reduces the consumption of detergents (without heating the detergents and saves energy). However, long-term use of the acid washing process can also lead to the resistance of microorganisms in the fermentation broth to acidity. Therefore, more and more breweries are adopting the CIP process of alternating alkali washing and acid washing.
4. Tank washing
The most suitable CIP process also requires the best CIP system to cooperate, because the cleaning of the fermentation tank requires that it can be cleaned in all directions without dead corners, and there must be a certain cleaning impact on the tank wall, especially the bubble cap. So fermentation tank scrubbers are generally selected to be able to rotate horizontally or in three-dimensional space, with multiple nozzles at different angles in different directions, and the sprayed water can reach every part of the fermentation tank.
The cleaning of fermentation tanks largely relies on the mechanical action of the cleaning solution to achieve the cleaning effect, and the mechanical action of the cleaning solution depends on the flow rate, flow rate, and pressure of the cleaning solution. Therefore, the power of the pump should be matched with the pipe diameter to ensure the pump pressure and liquid flow velocity. The pumping pressure is generally required to be controlled above 1.0 MPa, and the Reynolds number Re ≥ 25000. This has a strong impact on the wall and a strong descaling effect.
2、 Testing work
During the cleaning process, a portion of the cleaning agent will be lost, and the concentration of the cleaning agent has a significant impact on the cleaning effect of the fermentation tank. Therefore, it is necessary to test the concentration of the cleaning agent and determine its usage period, appearance, odor, etc. Taking into account all factors, it is necessary to promptly supplement and replace cleaning and sterilizing agents.
1、 Common methods and procedures for cleaning fermentation tanks
According to the cleaning operation temperature, it can be divided into cold cleaning (room temperature) and hot cleaning (heating). People often clean at high temperatures in order to save time and detergent; For the safety of large tank operation, cold washing is often used for cleaning large tanks.
According to the type of cleaning agent used, it can be divided into acidic cleaning and alkaline cleaning. Alkaline washing is particularly suitable for removing organic pollutants generated within the system, such as yeast, protein, hop resin, etc; Acid washing is mainly used to remove the internal components of the system
Inorganic pollutants generated, such as calcium salts, magnesium salts, beer stones, etc.
2、 Types and selection criteria of cleaning agents
Cleaning agents play a crucial role in the cleaning effectiveness of CIP systems, and selecting a suitable cleaning agent is essential.
1. Requirements for cleaning agents
Cleaning agents should have various functions such as wetting, penetration, dissolution, saponification, and digestion, with low corrosiveness, good safety, easy rinsing, low cost, and convenient use. They should also not pose a threat to human health and have minimal environmental pollution.
2. Classification of cleaning agents
According to the pH value of cleaning agents, they can be divided into two types: alkaline cleaning agents and acidic cleaning agents. Most alkaline cleaning agents are composed of 60% to 80% NaCl with the addition of baking soda, silicates, phosphates, chelating agents, and surfactants. Acidic cleaning agents are mainly composed of phosphoric acid, sulfuric acid, nitric acid, or citric acid with surface active agents added.
3. Selection of cleaning agents
The selection of cleaning agents should be comprehensively considered based on the material characteristics of the fermentation tank, the nature of the pollutants, the urgency of time, the local water quality characteristics, and environmental protection requirements.
4. Advantages of acid washing
Compared to alkaline washing, the superiority of acid washing lies in:
a. During acid washing, due to * 4 in the fermentation tank! Not interacting with acid, it will not affect the cleaning effect when reused repeatedly, and has good safety.
b. Acid washing is more effective in preventing beer stones and has a lower cost.
c. Acid washing does not require heating, thus saving energy.
d. When exchanging acid cleaning agents and disinfectants, there is no need to empty the gas inside the tank, so CO2 will not be lost.
e. Acidic cleaning agents are easier to clean and save water and time.