Jiangxi Chemicals talks about the aseptic treatment of compressed air Xu Weimin Liu Bo (Jiangxi Chemical Design Institute Nanchang uses air as the oxygen source. Because the air contains various microorganisms, in the real life, the air must be purified.) In the example, several key processes that should be noted during the process of compressed air purification are discussed. Relative temperature filling rate Whether it is food fermentation or fermentation of a drug, the fermentation bacteria require oxygen during reproduction, and air is usually used as an oxygen source in industrial production. We know that the air contains a wide variety of microorganisms. Once these substances (microorganisms) enter the fermenter with air and invade the culture solution, they will multiply and consume a large amount of nutrient solution and oxygen under certain living conditions. The resulting excreta can interfere with or even destroy the normal progress of the entire fermentation process, resulting in reduced product yields and even complete destruction of the fermentation process. Therefore, the sterilization of air has become an important link in the aerobic fermentation process, which is related to the success or failure of the entire process. In food and pharmaceutical fermentation projects, there are many methods for air sterilization, such as filtration sterilization, electrostatic sterilization, heat sterilization, etc., but the sterilization effects, equipment conditions, economic indicators, etc. of various methods are not the same, we must To avoid bacterial infection, it is necessary to simplify the sterilization process as much as possible to reduce the power consumption of equipment investment and operation. Therefore, this article focuses on the process of filtration sterilization. Process requirements for air quality We know that the different strains used in different fermentation processes are different. The growth and viability of the strains vary, depending on the atmosphere, the length of the fermentation cycle, the composition of the culture fluid, and the difference in pH. For different strains, there is a different requirement for the sterility of the sterile air used. In short, the influencing factors are complex and multi-faceted, and must be analyzed according to specific conditions, and specific process parameters must be worked out. When determining the amount of bacteria in the air, it is generally necessary to collect data on site. Today, the method for determining the bacteria in the air is generally to determine the approximate value of the data by culture or optical measurement, but in view of the current technical conditions, it is necessary to accurately design in the engineering design. It is not easy to determine the amount of bacteria in the air, that is, it is very difficult to control the amount of bacteria (aseptic) of the air filtered through the filter. In engineering design, data collection is a meticulous and long-term work. If the data is collected and then done in-depth design work, it can not meet the user's requirements for design progress, especially in the case of fierce competition in the market. Relying on it means losing the market. Since the initial bacteria content in the air cannot be accurately determined, the complexity of equipment selection and design is increased, and the quality of the product cannot be understood. In order to solve this contradiction, various research institutes and colleges and universities have done a lot of research work, and summed up a series of approximate calculation methods. We have used these research results in Guixi citric acid engineering design. It is worth mentioning that these research results are different because of different experimental methods and different observation angles. Therefore, the conclusions are different, but one thing is the same, that is, the basic principle of filtering has been recognized by all parties, because this problem is beyond The scope of this article is not discussed in detail. Sterilization method and process Jiangxi Chemical in Guixi citric acid project, the process parameters of compressed air are as follows: pressure P = 2.5kg / cm relative humidity is Υ = 50 ~ 60. Because Guixi is located in the southern part of the motherland, so we A more sophisticated air handling system (Figure 1) is used, which is suitable for any climatic conditions and is particularly suitable for wet southern areas. Its working principle is as follows: First, the atmospheric air is pre-filtered out of the large particle dust through the pre-filter (oil bath scrubber) to improve the service life of the compressor and improve the sterilization effect. The air is drawn into the compressor into the compression process. When the air is compressed, the temperature of the air rises sharply due to an increase in internal energy. By using the principle of heat sterilization, the high-temperature air at this time is sent to the gas storage tank through the pipeline, on the one hand, the gas source can be stabilized, on the other hand, since the gas flow enters the gas storage tank, the flow rate is reduced, and the gas is considered when designing the gas storage tank A certain residence time, so that under the action of high temperature, it plays a role of heat sterilization. The gas that has undergone the heat sterilization process and is stabilized is sent from the gas storage tank to the primary cooler for cooling. After this cooling, most of the water and oil are formed into larger mist particles, which is due to the compressed air. The content of the mist particles is large, so the cyclone separator is used for separation. In order to further precipitate the moisture in the air, the air is sent to the second-stage cooler to continue cooling. The cooled compressed air contains a large amount of misty water vapor. To intercept the water, the screen must be separated by wire mesh. Device. Since the relative humidity of the cooled air is 100, at this time, if the air is passed into the filtering device, the filter medium will become damp, followed by agglomeration and even mildew, and the process is not suitable for the air. Quality requirements. Therefore, in the process, we must consider the equipment to reduce the relative humidity --- heater. The heater is heated to the required parameters of the process and then sent to a sterile filtration unit for use in the fermentation unit. There are three key to achieving the above process. First, the degree to which the primary and secondary coolers should cool the air is good. If the air is cooled too low, it is disadvantageous for saving energy. On the one hand, it is not that the lower the air temperature, the better. This is because when the air moisture content is constant, when the air temperature is low, it is difficult to precipitate the water, even if the water temperature is lowered a lot. The effect of precipitation of water is not obvious, but it is not cost-effective in terms of economic benefits and energy conservation. On the other hand, to reduce the temperature of the air depends on the water temperature, and the choice of water source must take into account the geographical structure of the construction site and the capacity of the chilled water system. If the temperature is selected too low, it will inevitably require a water source with a lower water temperature, and each time the water temperature requirement is reduced by one degree, the investment of the equipment will be increased, and the equipment operation and management cost will be increased. In principle, higher air temperatures are beneficial for saving investment and saving energy. But this must be based on the requirements of the process. Similarly, the air temperature cannot be chosen too high. Although the high temperature compressed air can kill harmful bacteria, the excessive air temperature will also destroy the fermenting bacteria in the culture solution, and the high temperature compressed air cannot precipitate the water. The air with too high water content is the hotbed of the bacteria. If it is dangerous to enter the fermenter, it will destroy the growth of the fermenting bacteria, and will also slow down the fermentation cycle, resulting in a decrease in yield, which will eventually lead to the failure of the fermentation process. In short, it is important to select the appropriate air humidity for the fermentation process. In theory, the compressed air aseptic processing system can be calculated by the formula. The formula is as follows: X: the moisture content of the air (Kg water) Steam/Kg dry air) Ф: Relative humidity of air ()P: Air pressure (Pa) Pb: Saturated water vapor partial pressure (Pa) in air Second, water source temperature selection There are three general water sources, river water, deep well water ,frozen water. The water resources in the southern region are abundant compared to the northern regions, so natural water resources should be fully utilized when using water sources, and then artificial cooling water should be considered. At the same time, in order to rational use and save water resources, a circulating water system should be used. In the Guixi citric acid project, the water source water temperature selection values ​​are as follows: the primary water cooler inlet water temperature t the secondary cooler inlet water temperature t. Therefore, the principle of water source selection is that the primary cooler uses natural river water, and the secondary cooler uses artificial The cooling water source is both chilled water. In the Guixi citric acid project, the air temperature is selected as follows: primary cooler inlet temperature t secondary cooler inlet temperature t heater inlet temperature t third, selection of filter media for air filter, filter media is filtered The key to the bacteria, it directly affects the consumption of the medium, the power consumption of the sterilization process, as well as the labor intensity, maintenance management and so on. At the same time, the difference in the medium also affects the structure and size of the sterilization equipment. At present, the factory uses cotton fiber or glass fiber combined with activated carbon. In theory, the smaller the diameter of the fiber medium, the better the sterilization effect. Therefore, glass fiber is more effective than cotton. However, since the diameter of the glass fiber is small, its strength is low and it is easily damaged by the compressed air. More importantly, in the food and pharmaceutical industries, its products directly affect human life and health, and in the fermentation sterilization process, if the air is mixed with a trace of glass fiber is unfavorable. In terms of maintenance, when changing media. Glass fiber is easy to cause skin irritation in the human body. In the Guixi citric acid project, we used cotton as the filter medium (must be non-defatted cotton). In the design, considering the practical application, it is convenient for future maintenance and medium replacement. The filling rate of cotton is 0.09 ( At this time, the filling rate should not be too small. If it is too small, it may not press the medium, causing the media to flip and lose the filtering effect. But it is not too big. If the filling rate is too large, it will cause the medium to be replaced. The device cannot be covered, and the resistance of the device increases, increasing power consumption. In summary, if several key points can be coordinated, it is not difficult to design a sterile air system that is realistic and reasonable. CNC Machined Plastic Processing CNC Prototype Service,CNC Machining Prototype Plastic Processing,Plastic Products Machining Services,Precision CNC Machining Services Ningbo Jiongke Technology Co., Ltd , https://www.precisioncncmachiningparts.com