| Radon,as a natural radioactive gas,is the main source of human natural radiation.Besides ventilation radon reduction technology,radon removal by adsorption is also a reduction technology with strong practicability and wide application value.Activated carbon is often used as adsorbent in radon removal devices.The adsorption performance of activated carbon has an important influence on radon removal effect and operation cost.Therefore,in order to improve the adsorption performance of activated carbon,it is necessary to study the adsorption behavior of radon and develop methods to enhance the adsorption capacity of activated carbon radon.In this paper,the self-made circular tube flow radon source is used to design and manufacture the experimental device for radon dynamic adsorption of activated carbon under the action of electric field and non electric field.In this paper,the effects of radon concentration,specific velocity of air flow,particle size of activated carbon and electric field on radon dynamic adsorption performance of activated carbon are studied by using the self-made circular tube flow radon source and the experimental device for radon dynamic adsorption of activated carbon under the action of electric field and non electric field.The adsorption mechanism is studied by using adsorption kinetics and isothermal adsorption model.The research results are as follows:(1)Based on the diffusion seepage migration theory of radon,the mathematical model of round pipe flowing radon/thorium gas source is proposed,and the experimental device of round pipe flowing radon gas source is designed and manufactured.Using uranium ore(free radon production rate a=0.004 Bq/m~3s)as radon production material,the variation law of radon concentration at the outlet of flowing radon source under different flow rates(1L/min-5L/min)and round pipe length is studied by means of numerical simulation and experiment,The research conclusions are as follows:1)When the specific velocity of airflow is constant,the radon concentration at the outlet of the circular tube flow radon source decreases with the increase of the flow rate,but the total amount of radon at the outlet per unit time is basically unchanged;2)When the inlet flow is constant,the outlet radon concentration and the total amount of outlet radon increase uniformly with the increase of ore length in the circular tube;3)When the length of the round pipe is constant,the greater the flow,the smaller the thorium gas concentration at the outlet of the thorium gas source,and the total amount of thorium gas at the outlet per unit time becomes larger.When the flow is constant,the thorium gas concentration at the outlet increases non uniformly with the increase of the length.(2)Under certain temperature and humidity,the dynamic adsorption experiments under different radon concentrations,specific gas velocity and activated carbon particle size under non electric field are carried out.The research conclusions are as follows:1)When the specific velocity of air flow is constant,the inlet radon concentration has no effect on the dynamic adsorption coefficient of activated carbon,but the equilibrium adsorption capacity is greater at high radon concentration;2)The dynamic adsorption coefficient and equilibrium adsorption capacity of coconut shell activated carbon were significantly higher than those of other air flow velocities from 2 cm/s to 8 cm/s when the air flow velocity was 6.6 cm/s;3)The dynamic adsorption coefficient of small particle size activated carbon is 1.11 times and 1.62 times that of medium particle size and large particle size activated carbon,respectively.(3)The dynamic adsorption experiments under the action of electric field show that:1)under the action of electric field,the adsorption performance of radon on the two activated carbons is improved,and the dynamic adsorption coefficient and equilibrium adsorption capacity of radon on the activated carbons with relatively poor adsorption performance in natural state are increased more significantly;2)The enhancement degree of electric field on the adsorption performance of activated carbon is different under different air flow velocity;When the electric field intensity is 12500 V/m and 25000 V/m respectively,there is no obvious difference in enhancing the radon adsorption performance of the two activated carbons.(4)The fitting results of adsorption kinetics and isothermal adsorption model show that:1)the quasi first-order and quasi second-order kinetic models can not describe the dynamic adsorption process of radon on activated carbon;2)The dynamic adsorption of radon on activated carbon conforms to Langmuir model,Freundlich model and sips model.The adsorption of radon on activated carbon is non-uniform single-layer adsorption. |
PDF Full Text Request