用Sohn反应时间加性定律模拟多粒子反应器。三氧化铀转化为四氟铀的移动床炉案例
Using Sohn's law of additive reaction times for modeling a multiparticle reactor. The case of the moving bed furnace converting uranium trioxide into tetrafluoride
摘要：
多粒子反应堆的主要问题之一是处理它们的多尺度方面。对于建模，通常需要将反应器模型（描述宏观尺度的现象）与所谓的颗粒模型（模拟单个颗粒或粒子的行为）相耦合。H.Y. Sohn（1978）使用加性反应时间定律来近似但解析地计算反应器模型中颗粒的反应速率。与数值颗粒模型相比，它的最大优点是大大减少了计算时间，特别是在复杂反应堆模型的情况下。这是我们用来模拟移动床炉的方法，移动床炉是一种逆流气固反应堆，用于从三氧化铀生产四氟化铀的核燃料制造路线。我们开发的数值模型是二维的，稳态的，基于有限体积法。它描述了固体和气体流动，对流，传导和辐射传热，以及该过程中涉及的六种化学反应。应用反应时间加和定律，解析计算了反应器内各离散点的三个主要气固反应速率。我们已经证明了这种方法的有效性，通过比较其结果与从数值晶粒模型计算。文中还详细介绍了移动床炉模型本身的主要结果和计算所揭示的优化过程的可能性。
英文摘要：
One of the major issues with multiparticle reactors is to handle their multiscale aspect. For modeling, it usually comes to coupling a reactor model (describing the phenomena at the macroscopic scale) with a so-called grain model (simulating the behavior of a single grain or a particle). An interesting approach proposed by H.Y. Sohn (1978) is to use the law of additive reaction times in order to calculate, approximately but analytically, the reaction rate of a particle in the reactor model. Its great advantage, compared to a numerical grain model, is to drastically reduce the computation time, particularly in the case of complex reactor models. This is the approach we retained for modeling the moving bed furnace, a counter-current gas-solid reactor used in the nuclear fuel-making route for producing uranium tetrafluoride from uranium trioxide. The numerical model we developed is 2-dimensional, steady-state and based on the finite volume method. It describes solid and gas flow, convective, conductive and radiative heat transfers, and six chemical reactions involved in the process. The law of additive reaction times is used to calculate analytically the rate of the three principal gas-solid reactions at every discrete point in the reactor. We have demonstrated the validity of this approach by comparing its results with those calculated from a numerical grain model. Also detailed in the paper are the main results of the moving bed furnace model itself and the possibilities of optimizing the process revealed by the calculations.
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