新型氟化反应器设计及温度场模拟

Design and Temperature Field Simulation of New Fluorination Reactor

  • 摘要: 氟化物挥发法是近年来乏燃料干法后处理研究领域最活跃的流程,它是利用氟化物挥发性的差异将大部分易挥发性氟化物与难挥发性氟化物进行分离的一种手段。为更好地开展乏燃料干法处理,本文根据氟化挥发法处理乏燃料的反应特性设计并加工了一种新型氟化反应器,该反应器主要由反应炉、料杯、顶升机构等组成。通过实验测定获得了新型氟化反应器的温度场数据,采用Fluent软件对氟化反应器温度场进行了模拟,同时以CeO2为模拟料开展了投料量、氟气流量等条件实验。研究表明,通过设计底部气体预热室、中间设置烧结板、顶部设置沉降空腔,可有效提升氟气与物料的接触面积。氟化反应器温度场实验与计算结果表明,温度场计算结果与实验测试结果较吻合,预热区对气体温度预提升有非常重要的作用,主流道气体经预热区加热并通过烧结板后,气体温度分布区间逐渐缩小,烧结板能起到有效均匀布气的作用。模拟料实验结果表明,投料量大于50 g、氟气流量控制在50~60 L/h时,该类反应器具有较高的氟化转化率。

     

    Abstract: 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.

     

/

返回文章
返回