Design And Manufacture Of Model He Cryogenic Adsorber

Model He cryogenic adsorber has been widely used in the LHe refrigerator cryogenic system., which is important to the high efficient and stable operation of the system. The working medium of the LHe refrigerator is99.999%purity helium gas. After operation over extended periods of time, the system may be decontaminated, which result from the introduction of air into the system and may result in the plug、low efficiency, even the damage of the system. The main contaminant is N2, O2etc.gaseous contaminants. A model He cryogenic adsorber may serve an alternate purpose to remove N2,O2gaseous impurities to guarantee the continuous、high efficient operation of the system, which has been proved to be effective and widely used and thus will have broad prospect in the future. Up to now, the model He cryogenic adsorber, which has been widely used in the LHe refrigerator cryogenic system.at home and abroad, is made by LINDE company of Germany. It is costly, large LN2consumption and short work period. The aim of this thesis is to study on the model He cryogenic adsorber to make it localize and replace foreign product completely. Based on the optimal design of scheme, internal main heatexchanger, serpentine tube supercooling heatexchanger, liquid air separating cylinder, adsorption tube, liquid nitrogen dewar container, pressure and temperature etc. measuring/display/control instruments and safety device, a model He cryogenic adsorber that with good purification performances, less LN2consumption, longer work period and low price is prepared. As a result, the adsorber can be used for purifying helium gas from99.96%to99.999%. The main contents are as follows:I. Optimal design of the major structure scheme of model He cryogenic adsorberStudy the structure design scheme of LINDE model He cryogenic adsorber, find the main factors which cause its large LN2consumption and short work period when it is used to purify helium gas from99.96%to99.999%are:,the inadequate cooling to the inlet helium gas, which could result in with high temperature and large impurities for the inlet helium gas when it get into the adsorption tube. In our optimal design scheme, enhance the cooling of inlet helium gas to LN2temperature as close as possible and ensure large cold precipitation of impurities in it before adsorption tube by introducing heat exchange between LN2vapor and inlet helium gas, and then making it pass through a serpentine tube supercooling heatexchanger and liquid air separating cylinder soaked in LN2, which will lower LN2consumption and extend work period of the cryogenic adsorber. Our optimal design scheme of model He cryogenic adsorber includes:a main heatexchanger,.a serpentine tube supercooling heatexchanger, a liquid air separating cylinder, a series of activated charcoal adsorber, a LN2dewar, a set of measurement, display, control instrument of pressure and temperature and safety device, in which all cryogenic equipments are installed in LN2dewar. After passing through the main and serpentine tube supercooling heatexchanger, the liquid air separating cylinder, the temperature of inlet helium could reach to80K and the liquid impurities for cold precipitation will be collected in the bottom of liquid air separating cylinder and then be discharged to atomosphere mannully and regularly. The final cryogenic adsorption to the residual impurities is made in the activated charcoal adsorber, which is soaked in LN2.II. Optimal design of the main elements of model He cryogenic adsorber1. Optimal design of main heatexchangerThe optimal design scheme of main heatexchanger is a three-ways wound tube heatexchanger, which includes heat exchange among the inlet helium, the outlet cold helium and the LN2vapor. Passed through main heatexchanger, inlet helium could be cooled to90K.2. Optimal design of serpentine tube supercooling heatexchangerThe optimal design scheme of serpentine tube supercooling heatexchanger includes heat exchange between the inlet helium and the LN2vapor. It is a one-way wound tube heatexchanger, Passed through serpentine tube supercooling heatexchanger, inlet helium could be cooled to80K further.3. Design of liquid air separating cylinderAccording to accomplishing the separation of all N2, O2impurities amount during12hours operation periods to design.4. Design of activated charcoal adsorberAccording to accomplishing the physical adsorption of all N2, O2impurities amount during lOhours operation periods to design.5. Design of LN2dewarAccording to the bearing pressure of0.1MPa to.design. Adiabatic method choose high vacuum, multilayer insulation,. 6. Design of pressure&temperature measurement, display, control instruments and s afety deviceUse a PLC control system to execute the measurement, display and control of pressure and temperature.III. Manufacture and performance test of model He cryogenic adsorberThe model He cryogenic adsorber, which is designed and manufactured optimally in this thesis has finished construction and performance test up to now. The test results are:it can be used for purifying helium gas from99.96%purity to99.999%, of which the capacity is100Nm3/h, the LN2consumption is less than1L/h, the work period is11.6h and the regeneration period is6h.