Household Oxygen Generator is a type of machine for producing oxygen, its principle is to use air separation technology. First, the air is compressed at a high density and then the different condensation points of each component in the air are used to separate the gas and liquid at a certain temperature, and then rectify it to separate it into oxygen and nitrogen. In general, people are used to calling it an oxygen generator because it is mostly used to produce oxygen. Because oxygen and nitrogen are widely used, oxygen generators are also widely used in the national economy. Especially Homecare Oxygen Concentrator and Household Medical Devices for hospital and household.
The first countries in the world to produce oxygen generators were Germany and France. The German Linde Company made the world's 10th m3/s oxygen generator in 1903. Following Germany, the French Air Liquide Company also began to produce oxygen generators in 1910. Since 1903, the oxygen generator has a history of 100 years.
Household Oxygen Generator,Homecare Oxygen Concentrator,Household Oxygen Machine,Household Medical Devices Haloxylon Ammodendron Medical Equipment Co., Ltd. , https://www.halowheelchair.com
Application of vacuum freeze drying in flowers
The dry flowers that have been dried and preserved for color retention have the shape, color, texture, and rhyme of fresh flowers, and have long-lasting and unobserved dried flowers. They are increasingly loved by people. It is ideal for dark-lit cafes. , hotel and home decor. Vacuum freeze-drying is a new method of dry flowers that has emerged in recent years. Drying large flower plants using this drying technique can maintain the shape, color and aroma of dried flowers, without pollution, and has the prospect of further research. The basic principle of freeze-drying Vacuum freeze-drying is to first freeze the material below the eutectic point temperature, make the moisture in the material become solid ice, and then sublimate the ice directly into water vapor under a suitable degree of vacuum. The water vapor condensation device (water trap) in the vacuum system is then used to condense water vapor to obtain a technique for drying the product. The phase equilibrium relationship of water is the basis for studying and analyzing the principle of freeze-drying of water-containing materials. When the vapor pressure around the ice is lower than 610.5 Pa, the heating temperature of ice can be directly sublimated into water vapor, which is the theoretical basis of sublimation drying. Vacuum freeze-drying The basic working principle is also here. Operation process The freeze-drying process is divided into three processes: pre-freezing, sublimation drying and analytical drying. Since flowers consist of stems, leaves, stamens and petals, the moisture content of each part is different. If the drying effect of various parts of the plant is studied, the moisture content of each part should be measured first, and their respective eutectic points should be measured by the instrument. And eutectic points. 1. Pre-freezing process Pre-freezing is the individual freeze-drying of the plants beforehand, as a separate operation, using a general freezing method to pre-freeze the flowers into a certain shape. In vacuum freeze-drying, the highest temperature of the material freezes is an important factor affecting the quality and energy consumption of the freeze-dried product. Pre-freezing temperature must be lower than the eutectic temperature, otherwise it will cause product surface blistering, product shrinkage and other undesirable phenomena. Under normal circumstances, the minimum temperature of the product frozen can be lower than the eutectic temperature 5 ~ 10 °C. However, the freezing temperature cannot be set too low. Otherwise, problems such as large investment and high energy consumption will occur. In addition, the pre-freezing rate is also an important factor affecting the drying rate and product quality. The rate of sublimation during slow freezing is faster, and the drying time is longer during rapid freezing. A more appropriate cooling rate should be used to ensure that the material quality is not affected, using a slower cooling rate. 2. The sublimation drying process is to continue the sublimation drying process and must meet two basic conditions, namely the continuous supply of heat and the continuous removal of generated steam. The drying process is gradually drying from the surroundings to the inner center. The heat transfer driving force in the drying process is the temperature difference between the heat source and the sublimation interface, while the mass transfer driving force is the vapor pressure difference between the sublimation interface and the cold trap, and the temperature difference. The larger the heat transfer rate is, the faster the steam partial pressure difference is, and the faster the mass transfer rate is. In sublimation drying, the heating temperature cannot exceed the eutectic point temperature of the material. If the temperature is too high, the ice crystals will melt and affect the quality of the product. In addition, the heating method in the sublimation drying process directly affects the important process parameters such as the material temperature distribution, sublimation interface temperature, sublimation interface water vapor flux, and drying time. 3. Analyze the drying process Analyze the drying process is the process of sublimation drying, remove the moisture distributed in the matrix of the material in the form of free or bound water. The analytical drying of the material generally depends on a much higher temperature than the sublimation temperature. High temperature and low pressure are conducive to the analysis of drying, dry drying time is not the main material, such as frozen tomato slices, which can be frozen into ice structure water and a large number of free water, accounting for about 95%, analytical drying time is very short, The freeze-drying cycle mainly depends on the sublimation drying time. At this time, considerations for increasing the drying rate should be based on sublimation drying. Regardless of sublimation drying or analytical drying, the requirements for the cold trap temperature are similar, and the literature shows that when the cold trap temperature is lower than -50°C, excessively lowering the cold trap temperature has little significance for shortening the drying time. At present, the cold trap temperature is generally set to -45 to 50°C. Process and Characteristics of Vacuum Freeze Dried Flowers 1. Characteristics of Vacuum Freeze Dried Flowers (1) The source of raw materials is extensive. So far, there are about 2,000 to 3,000 types of dried flower plants that are commonly used in various countries of the world. (2) The natural and simple posture not only has the natural charm of the plant, but also maximizes the inherent shape and color of the plant. (3) Easy to use and manage, not only can maintain its shape and color in a long time, but also have long storage and sales. (4) Rehydration performance is good. After rehydration of edible flowers, it can maintain its original beautiful shape and cause people's appetite. (5) Its shrinkage rate is much smaller than that of dried flowers obtained by other methods, and it can maintain the fresh state as much as possible. (6) The cost of the freeze-drying equipment is large and the operating cost is high, resulting in high costs. 2. The practice of vacuum freeze-dried flowers To explore the new technology of dried flowers, Li Baoguo et al. performed freeze-drying experiments of purple Limonium, yellow marigold, and red Chinese rose. The average moisture content of each part was measured. The freezing temperature is -65°C and the degree of vacuum is set to 10 Pa. Using vacuum freeze-dried flowers, the shape of the flowers remains good, and some colors change slightly. The stems of the Chinese rose and Limonium and the flowers of the Limonium grasses did not contract and the petals of marigold and Chinese rose slightly deformed. The color of rose flowers is darker and darker than that of flowers. The color of yellow marigolds becomes lighter, and the color of purple hemophilia is basically the same after freeze-dried. The use of hot air drying, when the drying temperature is selected as 50 °C, dried flowers will have a serious shrinkage deformation, in addition, Li Baoguo also found in the test, dried flowers after the fragrance is not as strong, and the whole dried flower plants become brittle, easy to break and broken. Xu Chenghai made a freeze-drying test of Limonium and Asparagus, and the obtained Limonice all maintained its original shape. The color of flowers was natural and lifelike. It can be seen that the use of a suitable freeze-drying equipment, followed by optimization experiments, can greatly shorten the freeze-drying time, mass production, and commercialization requirements. Zhu Wenxue studied the lyophilization test of peony flowers of the Luoyang Red variety. It can be seen that the eutectic and eutectic temperatures of the stamen and petals are higher, and the eutectic and eutectic temperatures of the stems and leaves are lower, and the pre-freezing temperature is selected. Sublimation interface temperature should be based on stem eutectic temperature and eutectic temperature. Zhu Wenwen found that different drying conditions have different effects on the drying of peony flowers. When the pre-freezing temperature is -15°C and the heating temperature is 20°C, drying for 12 hours, the stems and leaves are generally dry, but the petals are still moist and partially faded, failing to reach the drying requirements. When the prefreezing temperature was -30°C and the heating temperature was 0°C, after drying for 45 hours, the whole plant was found to be substantially dry, the color of petals was slightly darker than that of flowers after drying, the stems did not shrink and deformed, and the leaves and petals slightly deformed. . Similar to Li Baoguo’s conclusion, dry plants are also brittle, easily broken and broken. Therefore, Zhu literature believes that although peony without pretreatment can be dried under certain conditions, and it can basically maintain the appearance, color, and floral scent, dried flowers cannot reach the effect of flowers and have a long drying time. Therefore, research should be focused on. The pretreatment process of peony flowers is to develop techniques for increasing plant toughness and reducing brittleness so as to ensure subsequent processing and viewing. In order to gain a deeper understanding of the characteristics of dried flowers, Zhang Zhengyong also observed the micro-morphology of branches, leaves, and petals of peony under scanning electron microscope and found that there were structural differences among various parts of peony plants, and this structural difference was found. It will inevitably affect the internal heat and mass transfer process, resulting in different drying characteristics of each part, thus affecting the overall effect of plant drying. Peony's petal surface cells are arranged densely, so the water is not easily discharged and the drying speed is slower. The stalk surface has a vertical stripe texture structure and the interior is a hollow mesh-like conduit structure. The epidermal cells on the epidermis of the leaf were arranged in a dense and dense array without a stomatal apparatus, and the epidermal cells were round; the stomata on the back surface were evenly distributed. Since the stems and blades have a sieve-like conduit structure and pores, the moisture content is easily discharged and the drying speed is faster. The results of the microstructural analysis are consistent with the freeze-dried test results. It makes the study of dry flowers from the macroscopic world into the microscopic world, which has a certain guiding significance for the improvement of dried flower processing technology. 3. Things to pay attention to when freeze-drying flowers should be noted Vacuum freeze-drying technology Drying flowers is a brand new dry flower production technology. Although there has been a lot of research and application in the drying of foods and medicines, flowers are different from foods and medicines. The drying index is mainly the shape and color of the flowers. Therefore, it is not possible to completely use the drying process of foods and pharmaceuticals, and it is necessary to carry out the research and improvement of the drying process aiming at the different biological characteristics of the flowers and the commercial requirements of dried flowers. With reference to domestic and foreign literature, the main problem of freeze-dried flowers currently is that the pretreatment process of flowers is not mature, and after the unpretreated flowers have been freeze-dried in vacuum, the plants are generally brittle, easily broken and broken. Therefore, the direction of further research is to study the pretreatment process of flower materials before drying and further optimize the vacuum freeze-drying process.