Design and Temperature Field Simulation of New Fluorination Reactor

Fluoride volatility method is the most active process in the dry reprocessing of spent fuel in recent years, which is based on direct fluorination of spent fuel to separate volatile fluoride from non-volatile ones. For the purpose of dry separation of spent fuel, this process begins with volatilizing most of the UF₆ by using F₂-O₂, then the other fission elements of the spent fuel are volatilized by using F₂ or halogen fluorides such as Cl, Br, etc. However, because of the strong corrosion of HF (or F₂), the fluoride equipment used in practical production is faced with high requirements for corrosion resistance, operability and so on. The commonly used fluorination reactors mainly include fixed bed and fluidized bed. Fixed bed is suitable for batch production mode with small operation volume for its advantages of simple operation, fewer process control parameters, lower cost, etc. Fluidized bed, which can significantly increase the gas-solid reaction contact area and thus the reaction efficiency, is widely used in the field of gas-solid reaction. Existing fluorination reactors mostly use fixed-bed reactors, which have small material contact area and uneven distribution of air field in the furnace. Thus, more F₂ is usually consumed compared with the theoretical amount to obtain better fluorinated products. With consideration of the characteristics of traditional fixed bed and fluidized bed reactor, a new fluorination reactor, which mainly consists of reactant furnace, feed cup and jacking mechanism, was designed according to the characteristics of fluorination reaction in this work. The temperature field of the new fluorination reactor was simulated by using a software of Fluent, of which the data were measured experimentally. Meanwhile, experiments of preparing CeF₄ were carried out by using CeO₂ and F₂ under different feeding amounts, fluorine flow and fluorine time. The results show that the contact area between fluorine and material, can be increased by designing a gas preheating chamber at the bottom, setting a sintering plate in the middle and setting a cavity at the top. Comparing the fluorination reactor temperature field experimental data with calculated value, the experimental data are consistent with the calculated results. The temperature distribution range of the gas gradually decreases after preheating zone and sintering plate according to the calculated results of fluorination reactor temperature field, which suggests that the sintered plate can effectively make the gas distribute evenly. The results of experiments of preparing CeF₄ show that the reactor has a high fluorine conversion rate when the feed amount is more than 50 g and the fluorine gas flow rate is between 50 to 60 L/h.