Study On The Desorption Characteristics And Methods Of Radon Absorbing Activated Carbon Microwave Regenerator

Radon is the only natural radioactive gas,and the human body is irradiated by radon and its progeny everywhere.Especially in some areas where the air cannot be convective,such as underground engineering,the internal radiation dose generated by the human body due to inhalation of radon progeny accounts for more than half of the total dose produced by natural radioactive sources.Therefore,it is necessary to carry out partial artificial radon reduction in these areas.Activated carbon is a widely used material for removing radon,but the volume of air containing radon(radioactive gas)that can be adsorbed per unit mass of activated carbon is limited.It is of practical significance to develop the research of saturated activated carbon regeneration method based on microwave technology with practical application value.The most commonly used in activated carbon regeneration is the high temperature heating regeneration method,and the open-loop desorption mode is generally used,and there is a phenomenon of charcoal burning.Currently,microwave heating is a relatively complete technology,and its biggest feature is that the heating process is non-contact,fast,and uniform inside and outside.Aiming at the high temperature heating regeneration method that is most commonly used in activated carbon regeneration,and the open-loop desorption regeneration mode is generally used,the phenomenon of charcoal burning exists,and a new saturated activated carbon desorption regeneration mode,namely closed-loop desorption mode,is proposed.At the same time,therefore Research on the desorption characteristics and methods of open-loop desorption and closed-loop desorption of radon-absorbing activated carbon using an improved microwave regeneration device.This article firstly discusses the microwave desorption method of radon-absorbing activated carbon(open-loop desorption and closed-loop desorption),focusing on the research on the heating characteristics of radon-absorbing activated carbon heating in the microwave field,and the loss of radon-absorbing activated carbon under open-loop desorption and closed-loop desorption.Research on the desorption rate of radon by activated carbon under two desorption methods,the study on the desorption rate of radon-absorbing activated carbon under two desorption methods,and the re-adsorption performance of regenerated activated carbon on radon.The experimental data analysis of the research shows that:there are two stages of temperature rise in the open-loop desorption,the first stage is uniform temperature rise,the second stage is close to the ignition point temperature of activated carbon,and the second stage is fast temperature rise,and the speed of temperature rise in the second stage is related to the gas flow rate,the higher the gas flow rate,the faster the rise,accompanied by obvious char burning phenomenon;Under the condition of closed-loop desorption,the temperature rises uniformly at each gas velocity,and there is a maximum temperature value.The higher the gas velocity is,the lower the maximum temperature can be achieved.The loss rate of activated carbon in closed-loop desorption is lower than that in open-loop desorption.The maximum loss rate of activated carbon in open-loop desorption is 13.39%and that in closed-loop desorption is2.59%.The loss rate of activated carbon in both desorption methods increases with the increase of gas flow rate.The desorption time of radon adsorbed activated carbon in closed-loop desorption is longer than that in open-loop desorption.The activated carbon that adsorbs low concentration radon(600±50Bq/m~3)can complete desorption in 25min in open-loop desorption mode and 45～50min in closed-loop desorption mode.The activated carbon that adsorbs high concentration radon(3000±300Bq/m~3)can complete desorption in 30min.Under closed-loop desorption,there is a concentration balance between the desorbed radon and the residual radon in the activated carbon,so two cycles of air exchange are required to complete the regeneration.For the activated carbon with low concentration of radon(600±50Bq/m~3),the desorption rate of activated carbon is higher than 98%under two regeneration modes.For the activated carbon with high concentration of radon(3000±300Bq/m~3),the desorption rate of activated carbon is higher than97%under open-loop desorption and 94%under closed-loop desorption.The adsorption capacity of non regenerated activated carbon to radon is4.4L/g.After regeneration,the adsorption coefficient of activated carbon to radon will change.After regeneration by open-loop desorption,the adsorption coefficient of activated carbon to radon decreases significantly,and is positively correlated with gas velocity.After regeneration by closed-loop desorption,the adsorption coefficient of activated carbon to radon has little effect,and is always higher than 4.10L/g(The activated carbon after desorption and regeneration in the two modes is pretreated by oven drying during the radon adsorption capacity test,and there will be no radon residue in the activated carbon).