Titanium alloy tube reaction surface area size and product extraction method!

Release time：2022-07-10 18:12:47 丨 Number of visits：

Sodium reduction of titanium alloy tubes is a heterogeneous reaction, which is often affected by diffusion factors. Therefore, the total reaction rate on the melt surface is related to the surface area of the melt, and the larger the reactor cross-sectional area, the larger the reaction surface area. Due to the large cross section of the large reactor, the gap between the chin block in the melt and the wall of the reactor is also wide, which is convenient for the floating diffusion of sodium at the bottom of the tank, which is very beneficial to improve the reduction rate. This effect is particularly obvious in the process of sodium preaddition. Because the titanium alloy tube is in a large reactor, the distance between the wall and the central high temperature zone is large, so the wall is not easy to overtemperature, the reaction vessel space is large, the reaction pressure is passive, the operation is smooth, so it can allow the use of a large speed. However, due to the great thermal effect of sodium reduction reaction, the upper residual heat must be excluded to further improve the feeding rate.

The phase state of the product is related to the melt temperature, which has great influence on the reduction process. When the melt temperature is less than 800℃, NaCl and some other products are solid phase, and the melt is a mixture of solid and liquid. Due to the formation of solid phase products, the diffusion and contact of reactants hinder the reaction speed greatly reduced. In addition, at such a temperature, the reduction reaction can not be carried out to the end, especially below 650℃, the product is a mixture of NaCl and TiCl2, TiCl3 and titanium alloy tubes. This is because titanium tetrachloride has the characteristics of step-by-step reduction, and the gas phase TiCl4 has a high diffusion rate and is easy to reduce. Once the intermediate products TiCl2 and TiCl3 are generated, they become a solid with low volatility, which greatly increases the collar expansion resistance and becomes a control factor. To improve the reaction shortness of low temperature reduction, the reaction can be turbulent or stirred to increase the reaction contact surface of the reactants. This is also a common method for the preparation of low-temperature chlorophenol in the first stage of the two-stage process.

When the melt temperature is greater than 800. At C, NaCl products are liquid phase except titanium alloy tubes. Due to the large specific gravity difference between Na and NaCl, it is easy to stratify, and the diffusion resistance of liquid sodium floating in the melt is small, which is conducive to reduction reaction. In addition, the resulting titanium particles sink and aggregate into clumps, with one ship not bridging the surface of the melt and expanding between the reactants. The release resistance is small, greatly improve the reaction speed, this situation is particularly obvious in large reactors. At this time, the reduction speed is very high, the control factor is to remove waste heat in time. But for the pre-sodium method (especially in the small reactor) in the late reaction, due to the accumulation of products, the diffusion resistance of the liquid sodium floating at the bottom of the melt is larger, diffusion becomes a control factor, reducing the reaction speed. Practice shows that when NaCl is in liquid phase, its influence on the reduction process is not great and can not be discharged. Moreover, the titanium alloy tube can be protected from leakage gas pollution due to NaCl coverage, but the utilization rate of the reactor is reduced.