Study On Vacuum Drying Ang Baking Technology And Its Performance Of Space Molecular Sieve

CO₂ is astronauts in the cabin space of output of major pollutants and sealing cabin CO₂ reaches a certain level will be harm to astronaut health. The removal of CO₂ mainly from non renewable forms such as LiOH and switch to the recycled solid amine and molecular sieve adsorption method. Solid amine, because of its regeneration reduced stability, shortened life expectancy, and it is hard to meet long-term space flight is gradually being four bed molecular sieve regeneration system to replace. Four bed molecular sieve regeneration system has been used for many years in the United States Sky Laboratory and the International Space Station, and has achieved good results. And our country started lately, although the design of some four bed molecular sieve device, with foreign advanced technology is still a gap. One of the main problems is the lack of space to meet the requirements of the use of molecular sieve. Space flight environment is more complex, the molecular sieve performance requirements are also higher, mainly include:high adsorption capacity, high mechanical strength, good wear resistance, with excellent thermal stability, can be repeated several times to use, etc. Molecular sieve preparation steps more, crystallization, drying in addition to water, roasting activation of molecular sieve all aspects of performance have great influence. Through explore new preparation methods to find fulfillment can achieve space performance requirements of the molecular sieve.In this paper, the vacuum drying and roasting technology will make 5A and 13X molecular sieve in vacuum drying oven for activation. Studying different drying, roasting time and temperature, calcination temperature and vacuum degree of molecular sieve adsorption performance. Determining the optimal preparation conditions of preparation of space by molecular sieve.The vacuum drying oven is compared with the baking oven, and the vacuum is pumped to 300,400,500,800, 1000Pa. Lower vacuum degree can be obtained by using the aperture size analyzer, and the adsorption performance of the molecular sieve is better. When the vacuum drying in vacuum is lower than 300Pa,5A and 13X molecular sieve adsorption capacity for static CO₂ and water reached 219.0mg/g, 28.43% and 30.67%,184.3mg/g.Under vacuum conditions, set different drying time and drying tem- perature of molecular sieve structure changes by SEM and XRD. The results show that the drying temperature in 300℃, the drying time is longer, the molecular sieve internal structure, the better, can obtain bigger specific surface area and pore volume, adsorption performance is better.Under the condition of vacuum and the determination of drying temperature and time, the different calcination temperature was set, and the SEM, XRD and static water and static CO₂ test analysis was used. The effect of roasting time on the performance of molecular sieve is not obvious, but it needs to be 1h to keep the activation. The optimum calcination temperature of 5A molecular sieve is 550℃, and the optimum calcination temperature of 13X type molecular sieve is 600℃. After the determination of the optimal molecular sieve preparation route, the operation of the molecular sieve prepared by the four bed molecular sieve dynamic system was used to simulate the space condition. System were used to open and closed, the CO₂ cylinder through into the system, to three days for a cyclic molecular sieve on CO₂ adsorption and desorption capacity and to observe the dew point setting system, the drying bed and the adsorbent bed temperature changes. The results show that the 5A and 13X molecular sieves prepared by vacuum drying roasting technology can effectively adsorb at low temperature and high pressure, and the effective desorption is carried out at high temperature and low pressure. Drying bed outlet dew point is always at-45--50℃, can be very effective to ensure the degree of dry air. When the system volume concentration of CO₂ is below 7000ppm, the quality of the adsorption treatment is 3.95-4.32kg/d, which can meet the normal CO₂ concentration of 3 people in the space cabin.