Modeling for Simple Batch Distillation of Vanadium Oxychloride−Titanium Tetrachloride (VOCl3−TiCl4) Mixture Tran Duy Hai 1,2 , Tran Anh Khoa 1,2* , Minh-Vien Le 2,3 , Mai Thanh Phong 2,3 , Phan Dinh Tuan 1 1 Ho Chi Minh City University of Natural Resources and Environment, Ho Chi Minh City 700000, Vietnam 2 Faculty of Chemical Engineering, Ho Chi Minh City University of Technology (HCMUT), Ho Chi Minh City 700000, Vietnam 3 Vietnam National University Ho Chi Minh City, Ho Chi Minh City 700000, Vietnam Corresponding Author Email: takhoa@hcmunre.edu.vn https://doi.org/10.18280/ijht.390614 ABSTRACT Received: 9 November 2021 Accepted: 23 December 2021 VOCl3 and TiCl4 exhibit a similarity of various thermal properties, causing difficulty for these components separation through distillation technique. Dynamic behavior of distillation process of VOCl3−TiCl4 mixture was modeled based on the mass and energy balances, revealing in a model form of the ordinary differential equations. Influences of heating power, airflow, initial concentration, and operating pressure were considered. Simulation results show an ineffective distillation of the mixture under natural pressure. However, the reduction of the operating pressure advanced the pure TiCl 4 recovery performance. Compared to experimental data, the relative error of the simulation findings is less than 5%, indicating the potential of the application of the proposed model for describing the distillation of the VOCl3−TiCl4 mixture. Keywords: distillation, modeling, titanium tetrachloride, vanadium oxychloride 1. INTRODUCTION Titanium and its compounds have been widely used in aerospatiale, automotive and biomedical engineering because of specific physicochemical properties such as high mechanical strength, good corrosive resistance, and biocompatibility [1-3]. Natural minerals (ilmenite, rutile, anatase, leucoxene, and brookite) and concentrated sources (titania slag and synthetic rutile) are used as titanium-bearing feedstocks for titanium processing [4, 5]. Until now, metallic titanium and high-grade TiO2 were mainly produced from titanium tetrachloride (TiCl4) – a product of chlorination of titanium sources [6]. However, impurities in raw material, were also chlorinated to the chloride compounds, result in a color change of crude TiCl4 from yellow to dark reddish- brown [7, 8]. Physical, chemical and physo-chemical methods were successfully conducted for purifying TiCl4 with high efficiency [7, 9]. In terms of them, distillation is a powerful technique toward industrial application due to its low cost and controllability [9, 10]. Because of the small difference between the normal boiling point of vanadium oxychloride (VOCl3) (127℃) and the desired TiCl4 product (136.5℃), the removal of VOCl3 through distillation is ineffective [9]. However, the purity of product and the recovery yield of distillation can be controlled and optimized by changing distillation mode and operating conditions [11]. Using modeling and simulation, the instinct properties of many engineering problems under different setup values of variables can be quickly and simply explored [12]. To our best knowledge, the modeling of VOCl3−TiCl4 distillation has not been reported. In this paper, the dynamic behavior of VOCl3−TiCl4 mixture separation in a simple batch distillation column was modeled. The comparison between experimental and simulated results was also presented. 2. THE EQUATIONS The scheme of the studied batch distillation system is shown in Figure 1, including a bottom (boiler), a condenser, and a distillation column, which was cooled by outer airflow under forced convection. Assumptions were considered for modeling: (i) negligible temperature change in a cross-section of the distillation column, (ii) equilibrium of heat exchange through the distillation column and heat of condensation of the heavy component (TiCl4), and (iii) small mole fraction of VOCl3 in feedstock. The heating stage of bottom mixture up to the boiling point of the light component (VOCl3) was ignored. The models were established for the following stage since the temperature at the top of the distillation column has reached the boiling point of VOCl3 until the liquid in the bottom was completely evaporated. 2.1 Modeling for the distillation column Mathematical models are based on heat and mass balances of a differential volume of the distillation column with a height dz between z and (z+ dz), as shown in Figure 2. ( ) , 2 a pa z mc d hR T dz    = − (1) where, ma and cp.a is mass flow (kg.s −1 ) and constant pressure heat capacity (J.kg −1 .K −1 ) of air, h is convective heat transfer coefficient (W.m −2 .K −1 ), R is the radius of the distillation International Journal of Heat and Technology Vol. 39, No. 6, December, 2021, pp. 1805-1811 Journal homepage: http://iieta.org/journals/ijht 1805