Prediction of parameters and simulation of the process for boron isotope separation

Abstract

High − abundance boron isotopes are “bottleneck − restricting” products in fields such as the nuclear industry, nuclear medicine and semiconductor manufacturing. Chemical exchange distillation with anisole as complexing agent is a promising boron isotope separation technology. Due to the lack of key physical properties of boron isotopes and their corresponding complexes, there was not a rigorous separation process model reported in literature. The complex conformation and enthalpy change was investigated with Density Functional Theory (DFT) based on the MP2/6-311++G(d,p) group using solvation effect. The Henry’s coefficients of BF₃ in anisole and complexes were predicted using the COSMO-RS model, the values were 0.2847 (¹⁰BF₃), 0.2847 (¹¹BF₃) and 2.2909 (¹⁰BF₃), 2.2910 (¹¹BF₃) respectively, indicating that boron trifluoride was mainly dissolved in anisole rather than in complexes. The equilibrium constants of exchange reaction in anisole at various temperature were necessary and obtained by analyzing the resonant frequency. Then a rigorous model of the chemical exchange distillation process insisting of exchange column, complexation reactor, and cracking reactor was established. The appropriate operating conditions are as follows: the temperature of the complexation reactor is 25 ℃, the temperature of the low − temperature cracking reactor is 110 ℃, and the temperature of the high − temperature cracking reactor is 170 ℃. Under the appropriate operating conditions, the specific heating energy consumption for producing ¹⁰BF₃ products with abundances of 85 %, 95 %, and 99 % is 6.90 × 10⁵ kJ/t, 7.41 × 10⁵ kJ/t, and 1.42 × 10⁶ kJ/t respectively, and the yields are 71.76 %, 65.27 %, and 56.32 % respectively. Furthermore, a vacuum deep − cracking method was proposed to obtain ¹¹BF₃ with an abundance of 99.9 %, which overcame the back-mixing caused by the reused anisole.