The fruit and vegetable gas storage library has been used for commercial storage for nearly 70 years. It has been widely used in some developed countries. For example, the fruit stored in the US atmosphere is as high as 75%, France is about 40%, and the UK is about 30%. China's fruit and vegetable modified atmosphere storage technology started late, and its commercial application is only a matter of recent years. With the integration of global economy and the development of China's national economy, people's quality requirements for fruit and vegetable preservation will be higher and higher, fruits and vegetables. Atmospheric storage will inevitably develop faster in China. To this end, a brief account of several issues that should be noted in the use of fruit and vegetable gas storage and its use. 1. Air conditioning library building The air conditioning library is developed on the basis of the cold storage of fruits and vegetables. On the one hand, it has many similarities with the cold storage of fruits and vegetables. On the other hand, it has a big difference with the cold storage of fruits and vegetables, mainly in: (1) The volume of the air conditioning reservoir. In Europe and the United States, the volume of a single storage room in a modified atmosphere storage room is usually between 50 and 200 tons. For example, the volume of a storage space in the British apple atmosphere storage warehouse is about 100t, and in Europe is about 200t, but the volume of a single vegetable compartment is usually 200. Between ~500t, the capacity in a single room in North America is larger, generally around 600t. According to the current situation in China, 30 to 100 tons is used as a opening room, and at least 2 units are built, but generally no more than 10. (2) The air conditioning warehouse must have good air tightness. This is one of the most important characteristics of the air conditioning warehouse building structure is different from the ordinary fruit and vegetable cold storage. Ordinary cold storage has almost no special requirements for air tightness, and air conditioning is essential for air tightness. This is because the required gas composition should be formed in the atmosphere control tank, and the set index should be maintained for a long time during storage of the fruit and vegetable, and the gas exchange and exchange of gas inside and outside the warehouse should be reduced, and the gas storage warehouse must have good air tightness. . To this end, in the process of air-conditioning warehouse door installation and air-tight layer construction, it must be carefully and meticulously found that suspicious parts should be promptly inspected and remedied. For the air-conditioning warehouse constructed by the brick-concrete structure of the civil engineering warehouse, if large-scale protrusions or falling off occur, it is often caused by the fact that the surface of the maintenance structure is not dry. Before construction, it is necessary to pay attention to the dryness of the maintenance structure. An important aspect of the quality control of the atmosphere control warehouse is the air tightness test. Currently widely used is the stress test method. It has the advantages of simple test method, simple test instrument and intuitive result. The pressure test method has a positive pressure method and a negative pressure method, and a positive pressure method is usually used to avoid the use of the negative pressure method to cause the inner liner to fall off. So far, the international standards for air-tightness testing of air-conditioning warehouses have not yet formed a unified standard. China has not yet issued a national standard for air-tightness testing of air-conditioning warehouses. However, using the positive pressure test method, the "half-buck time" is a representation of the commonly used airtightness test standards and results. The so-called half-buck time refers to the time required from the time when the test pressure drops to half of the initial pressure. Among the existing airtight standards in the world, the highest requirement is: the test pressure is 294Pa (30mmH2O), and the half pressure drop time is equal to or exceeds 30min. Otherwise, it is unqualified. This standard is only adopted by some manufacturers in a few countries such as Italy. . In recent years, the FCE company's air-tight test in the combined air-conditioning warehouse installed in China has passed the test: the pressure in the warehouse is up to 30mmH2O, and the pressure in the warehouse is reduced to not less than 4.4mmH2O within 30min. (3) Safety of the atmosphere control library. The safety of the atmosphere library must also be considered in the architectural design of the atmosphere library. This is because the air-conditioning warehouse is a closed type cold storage. When the temperature inside the warehouse rises and falls, the gas pressure also changes, which often causes a difference in air pressure inside and outside the warehouse. According to the data, when the temperature outside the library is higher than the temperature inside the library (4) The gas storage warehouse should generally be built as a single-storey building. Generally, the fruit and vegetable cold storage can be built as a single-storey or multi-storey building according to the actual situation, but for the air-conditioning warehouse, almost all single-story ground buildings are built. This is because when the fruits and vegetables are transported, stacked and stored in the warehouse, the ground is subjected to a large load. If a multi-storey building is used, the airtight treatment is complicated on the one hand, and the gas is easily generated during the use of the modified atmosphere storage. The dense layer is destroyed. The building height of a larger air conditioning library is generally 2. Air conditioning library refrigeration equipment and temperature sensor configuration (1) Refrigeration system. Most of the refrigeration equipment of the air-conditioning warehouse adopts a piston-type single-stage compression refrigeration system, which uses ammonia or Freon-22 as a refrigerant. The cooling method in the warehouse can be direct evaporation cooling of the refrigerant, or indirect cooling of the intermediate brine. The latter is used for the atmosphere control library is better than the former. Because the intermediate brine is more convenient to control the temperature of the liquid supplied to the chiller, it is only necessary to install a recirculating stroke control three-way valve on the liquid supply pipeline to meet the requirements of different temperatures in different warehouses. In order to reduce the dry consumption of the items stored in the warehouse, the well-performing air-conditioning warehouse requires a heat transfer temperature difference of 2 to 3 ° C, which means that the difference between the evaporation temperature of the air-conditioning warehouse and the storage requirement temperature is 2 to 3 ° C, which requires It is much smaller than a normal cold storage. Only by controlling and achieving a small difference between the evaporation temperature and the storage temperature can the evaporator be frosted and the higher relative humidity required in the reservoir can be maintained. Therefore, in the design of the atmosphere control library, under the same conditions, the heat transfer area of ​​the chiller is usually larger than that of the ordinary fruit and vegetable cold storage chiller, that is, the so-called "large evaporation area is adopted in the design of the air-conditioning chiller. Heat transfer temperature difference" program. (2) Configuration of the temperature sensor. A well-designed atmosphere library can be implemented within the library during operation. 3. The main air conditioning equipment and auxiliary equipment of the air conditioning warehouse In general, the gas-conditioning equipment mainly includes nitrogen-making equipment, carbon dioxide removal equipment, ethylene removal equipment and humidification equipment. Among them, the nitrogen utilization equipment has the highest utilization rate, so it is more important. According to the working principle of nitrogen production equipment, it can be divided into three types, namely, adsorption separation type nitrogen production type, membrane separation nitrogen production type and combustion oxygen reduction nitrogen production type. (1) Nitrogen generator. At present, there are two main types of nitrogen generators used in air-conditioning warehouses in China: adsorption-separated carbon molecular sieve nitrogen generators and membrane-separated hollow fiber membrane nitrogen generators. Compared with the hollow fiber membrane nitrogen generator, the carbon molecular sieve nitrogen generator has lower price, less investment in supporting equipment, lower energy consumption per unit gas, cheaper replacement of the adsorbent than the membrane module, and the function of removing ethylene. The advantages are relatively complicated, the process is relatively large, the noise is large, the operation stability is not as good as the hollow fiber membrane nitrogen generator is the relatively weak of the carbon molecular sieve nitrogen generator. (2) Carbon dioxide removal machine. The carbon dioxide removal device is divided into two types: a discontinuous type (commonly referred to as a single tank machine) and a continuous type (generally called a double tank machine). The gas with a higher concentration of carbon dioxide in the reservoir is pumped into the adsorption device. After the carbon dioxide is adsorbed by the activated carbon, the adsorbed low carbon dioxide gas is sent back to the warehouse to achieve the purpose of removing carbon dioxide. The amount of carbon dioxide adsorbed by activated carbon is a function of temperature and is proportional to the concentration of carbon dioxide. Usually The air after offline regeneration of carbon dioxide contains a large amount of carbon dioxide and must be discharged to the outside. The intake and return air piping of the inlet and outlet gas storage tanks must be slightly inclined toward the storage body to prevent the condensed water from flowing into the removal machine, causing the activated carbon to fail. Volatile substances such as gasoline and liquefied gas should be avoided in the equipment room and kept at a temperature of 1 to 40 °C. (3) Ethylene stripping machine. At present, there are two main methods for removing ethylene: potassium permanganate oxidation and high temperature catalytic decomposition. The former method is to wet a porous material (such as expanded perlite, expanded vermiculite, alumina, molecular sieve, broken brick, foam concrete, etc.) with a saturated aqueous solution of potassium permanganate (usually at a concentration of 5% to 8%). The carrier is then placed in a reservoir, in a package, or in a closed loop system, and the ethylene is oxidatively removed using the strong oxidizing properties of potassium permanganate. Although the removal of ethylene by this method is simple, the removal efficiency is low, and it is generally used for small or simple storage. In the air oxidation de-ethylene removal device, the core part is a special catalyst and a variable temperature field electric heating device. The catalyst used is a special active silver containing calcium oxide, cerium oxide or cerium oxide. The variable temperature field electric heating device can generate a variable temperature field which gradually increases from the outside to the inside temperature: from 15 ° C → 80 ° C → 150 ° C → (4) Humidification device. Water mixing and humidification, ultrasonic humidification and centrifugal atomization humidification are three common humidification methods in the current atmosphere control library. 4. Reasonable use and management of the atmosphere library (1) Reasonable and effective use of space. The volume utilization factor of the air-conditioning warehouse is higher than that of the ordinary cold storage. Some people describe it as “high-filled pileâ€, which is a feature of the design and operation management of the atmosphere control warehouse. The so-called "high-filled pile" means that the fruits and vegetables that are loaded into the air-conditioning warehouse should have a large loading density. In addition to leaving the necessary ventilation and inspection channels, the free space of the air-conditioning warehouse should be minimized. Because the smaller the free space in the air-conditioning warehouse means that the gas inventory in the warehouse is less, so that the air-conditioning equipment can be appropriately reduced on the one hand, and the air-conditioning speed can be accelerated, the air-conditioning time can be shortened, and the energy consumption can be reduced. And make the fruits and vegetables enter the atmosphere storage state as soon as possible. (2) Fast forward and out. Atmospheric storage requires fruit and vegetable storage speed to be fast, fill up as soon as possible, seal the warehouse and adjust the gas in time, so that the fruits and vegetables enter the air-conditioning state in the shortest possible time. In normal management, it is not possible to enter and exit the goods as easily as ordinary cold storage. Otherwise, the gas composition in the storage will change frequently, thereby weakening or losing the effect of controlled atmosphere storage. When fruits and vegetables are released from the warehouse, it is best to finish them in one batch or in batches in a short period of time. (3) Good air circulation. In the process of cooling the atmosphere, the recommended circulation rate range in the UK is: in the initial stage of fruit and vegetable storage, the number of air exchanges per hour is 30 to 50 times the volume of the empty storage. Therefore, the two-speed fan or multiple axial fans can be used independently. Control plan. In the cooling phase, the air volume is larger and the cooling rate is fast. When the temperature drops to half or less of the initial value, the number of air exchanges can be controlled 15 to 20 times per hour.